WTC _,

WTC _,

International PyfheHometer Comparisons 

IPC VII 

24 September to 12 October 1990 

Results änd Symposium 

Working Report No. 162 

Swiss Meteorologica! Institute 

Davos and Zürich, March 1991

Internationa! PyrheHometer Comparisons 

IPC VII 

24 September to 12 October 1990 

Results and Symposium 

Table of Contents 

IPC VII. Part 1: Measurements and Results , 1 

1. Introduction .......... 1 

2. Pafticipation ........... . .. , I 

3. Data Acquisition and Evaluation : . . 3 

4. Results . ..... .... .. . ......... 4 

IPC VII Part 2: Tables and Figures 7 

IPC VII Part 3: Contributions to Symposium 35 

Table of Contents . . . : 35

1. Introduction 

IPC VII Part 1: Measurements and Results 


The Executive Council of the World Meteorological Organization (WMO) at its 4 Ist Session (Geneva, June 1989) 

authorized the 7th International Pyrheliometer Comparisons (IPC VII) combined with the RA I and RA VI Regional 

Pyrheliometer Comparisons to be held at the Physikalisch-Meteorologisches Observatorium Davos; World Radiation 

Center (PMOD/WRC) from 24 September to 12 October 1990. The technicai Organization was delegated to 

PMOD/WRC, whereas the overall responsibility, as to ratify and disseminate the final results is with the WMO 

Commission for Instruments and Methods of Observation (CIMO) Working Group on Radiation änd Atmospheric 

Turbidity Measurements. The chairman of this WG is D.Wardle and the secretary from WMO K.Schulze; who was 

also responsable for the Organization of the IPC as far as WMO was concerned.. 

2. Participation 

A total of 27 WMO Me'mbers and 7 Institutions were represented by 54 participants with 58 instruments. They 

are listed in Table. 1.1. Not all the participants Hsted in the last column were present during the whoie period; the 

ones labelled') are members of the CIMO WG and some of them attended on!y the last wcek's mceting qf the WG. 

A list ofaddresses is given in Part 2. 

Country Instrument Manüfacturcr 

... or dcsigncr 

Worid Radiation Centers 

USSR 

Switzerland 

WSG 

A212 

PCC3-005 

PM06 80022 

PM06 10 

PM02 

PM05 

CROM2-L 

CROM3-L 

HF-18748. 

MKV1-67814 

. PAC-3 

Regiona! Radiation Centers 

Table 1.1: IPC Vn Participation 

SMHI 

MGO 

PMOD 

PMOD 

PMOD 

PMOD 

IRMB 

IRMB 

Eppley 

TMI 

JPL 

RA I (including National Centers of RPC) 

Algeria 

Ä 16491 Eppley 

Egypt 

Ä564 SMHI 

Ethiopia NIP-18653 Eppley 

Kenya 

Ä 13444 Eppley 

Nigeria 

Ä576 Eppley 

Tunisia 

Uganda 

A 9003 

HF 23725 

Ä6549 

Eppley 

Eppley 

Eppley 

Institute Participant 

Main Gcophysical Observatory, 

Leningrad 

Physikalisch-Meteorologisches 

Observatorium, Davos 

Office National M6teo., Alger 

Meteo. Auth. Koubry, Cairo 

NaL Metep. Serv., Addis Ababa 

Kenia Meteo. Dept., Nairobi 

Meteo. Dept,, Lagos 

V.Kievantsova 

M.KIimovskäya 

C. Fröhtich 

J.Romero 

Ch.WchrH 

A.Chevalier, IRMB 

D. Crommelynck, IRMB 

AGeisseler, PMOD/WRC 

S-.KoIIcr, PMOD/WRC 

A.Rohrer, PMOD/WRC 

H.J.Roth, PMOD/WRC 

A.Chabäne 

F. M.E!-Hussainy 

G. ZeIelew 

G.Muchemi 

K.Rufai 

INnodu 

Centre Regional, M6teo. NaL, Tunis B.Ben M'Rad 

R.Kenzari 

Meteo. Service, Kampala E.Bagarukayo 

1


RA II 

India 

Japan 

RA in 

Argentina 

RA IV 

Cänada 

USA 

RA V 

Australia 

Fihland 

France 

FR of Germany 

Hungary 

EPÄC-13219 Eppley 

PMO6-8H107 CIR 

MKVI-67915 TMI 

HF-18747 , Eppley 

EPAC-12843 

MKV1-67502 

Ä 578 

PMO6-850407 

HF-27160 

Various Institutions 

DSET, USA HF-17142 

Eppley, USA HF-14915 

HF-21185 

HF-27798 

Table 1,1: IPC VII Participation (cont.) 

Eppley 

TMI 

SMHI 

CIR 

Eppley 

RA VI (including National Centers of RPC) 

Austria 

A 15192 Eppley 

MKVI-68025 TMI. 

Belgium 

A 7 Smiths.Inst. 

A 7190 Eppley 

A 7191 Eppley 

PMÖ6^850401 

A 7636 

MKVI-68016 

A 568 

PM06-5 

HF-19746 

Israel 

HF-27162 

Netherlands A559 

HF-27159 

Norway EPAC-13617 

Spain PMO6-811104 

Sweden 

A 171 

PMO6-811108 

Switzerland PM06-79121 

United Kingdom MKVI-67604 

2 

CIR 

Eppley 

TMI 

SMHI 

PMOD 

Eppley 

Eppley 

SMHI 

Eppley 

Eppley 

CIR 

SMHI 

CIR 

CIR 

TMI 

Eppley 

Eppley 

Eppley 

Eppley 

Meteo. Office, Pune 

Meteo. Agency, Tokyo 

Meteo. Service, Buenos Aires 

Atm. Env. Service, Toronto 

Nat. Ocea. Atm. Adm., Boulder 

Bureau Meteo., Melbourne 

Meteo. Zentralanstalt, Wien 

, Inst. Roy. Meteo., Bruxelles 

Meteo. Institute, Helsinki 

Centre Radiometr., Carpentras 

Dt. Wetterdienst; Hamburg 

Inst. Atmos. Phys., Budapest 

Meteo. Service, Bet Dagan 

Meteo. Institute, GK De Bilt 

Geophys. Institute, Bergen 

Inst. Nacional, Madrid 

Meteo. Institute, Norrköping 

Inst. Suisse M6teo., Payeme 

Meteo. Office, Wokingham 

DSET Lab, Phoenix 

Eppley Lab, Newport 

V.Desikan 

H.Shimura 

T.Grajnar 

B.McArthur') 

D.Wardle*) 

D.NeIson 

B.Forgan*) 

K.Gregory 

P.Novotny 

E. Wessely 

H.Boyen 

AJoukpff 

M.Lombaerts 

W.Vandenborre 

L.Laidnen 

J.Olivieri 

K.Dehne^) 

G.Major") 

F. Miskolczi 

Z.Nagy ^ 

A.Manes 

W.Slob 

T.de Lange 

R.M.Ramlrez Marttn6z 

L.Dahlgren 

M.Collins 

J.Hickey

JPL.USA 

SIRI.USA 

TMI, USA 

Inst.Geo. Mdxico 

NTI, Sweden 

MKVI-67702 

MKVI-68018 

MKVI-69036 

MKVI-67401 

Ä 18587 

HF-15744 

Table 1.1: IPC Vit Participation (cont.) 

TMI 

TMI 

TMI 

TMI 

Eppley 

Eppley 

3. Data Acquisition and Evaluation 


Jet Propulsion Lab!, Pasadena 

Solar Energy Res. Inst., Golden 

Technical Meas. Inc., La Canada_ 

Univ. NaL Aut. Mexico, Mexico 

NaL festing InsL, Boras 

EJLaue 

C.V.WeUs 

TJ..Stoffel 

MlBerdahl 

J.Stallkamp 

A.Muhlia 

LJîedquist 

3.1 Timing 

The measurements are taken in runs lasting 2-1 minutes with a basic sampling of 90s,. Voice announcements before 

änd büzzer Signals during each event are used to inforrn the participant about the sequence. The timing for the 

different instrument. types isasfollows: 

a) Angstrom pyrheliomcters: during the first 90s the zero of the instrument is es^blished. From there on every 

90s a icft or right rcading is performed, stariing with exposing the right hand Strip to the Sun. The first Teadingis 

not taken into account. The following readings are combined as L-R, R-L, etc., yielding a total öf 11 irradiance 

values per run. 

b) PACRAD: the run Starts with shutter closed, after 60s the heater is turned pn during 30s (this was introdüced 

after IPC III in order tö have a. well defined thermal Status of the instrument independentof the Operation sequence 

beibr the run). At 270s the zero of the thermopile is read and the heater switched on again. At 360s the heatcr 

voltage, current and thermopile is read, the heater tumed off and the shutter opened; From 450s on every 90s 

readings are taken änd after the last one the shutter is clösed yielding 8 irradiance yalues during a tun; 

c) HF type pyrheliometers: the run Starts with the shuttcr'closed, after 90s the zero i$ read. Then the heater is 

turned on until 90s and then the voltage, current and thermopile is read, the heater tumed off and the shutter opened.' 

From 270s onward the in$tm^ 

d) TMI type pyrheliometers: the run Starts with shutter closed and.the calibration procedure is performed until the 

end of the first 90s. Starting at. 180s readings are taken every 90$ yielding a total öf 12 irradiance yalues during a 

, run. - .. . * - ' 

c) Active cavity type pyrheliometers : the run Starts with a reference phase (shutter closed) during the first 90s, 

foiiowed by a measuring phase (shutter open) for the next 90s. This is repeated for the next 18 minutes. A total pf 

6 open and 7 closed readings are taken yielding a total öf 6 irradiance välues during a run. PM02, as the working 

reference, is read at twice the pace, yielding 13 irradiances for each run. The reference phase lasts 38s and the 

measuring phase 52s. 

f) Other instruments: the NIP ahd PCC3-005 pyrheliometer take 12 irradiance values every 90s after a zero 

rcading during the first 90s. < . . ' 

3.2. Acquisition 

The analog data-acquisition system is based on 8 parallel DVM HP3478A with scanners and is used for the WSG 

Instruments, the radiorneters of PMOD/WRC and the auxiliary data. For the input of data from thepartieipants micro-. 

terminals, Burr-Brown type TM27 and TM2700 are used. The whole System is controlled by a HP Computer Series 

9200, which also Stores and evaluates the data. The terminals are identified by an ünique address (terminal number) 

and the input from the partieipahts cönsists of up to 8 digits foiiowed by a label A to F; indicatihg the type of data. 

A maximum Of three different values ean be assigned to Ohe instrument. Thus two users can share a terminal. 

3.3. Data Evaluation ; 

For each instrument the irradiance and ratio to PM02 is obtained with the corresponding evaluation procedure. 

After each run, a summary of measured yalues and eyäluated irradiances is printed and distributed for checking by 

the parüeipants and; if necessary, the raw data can be edited for gross errors. Updated summaries with the mean

IPC VII Part 1: JMeasurements and Results 

Yalues of the ratio and the Standard deviation for each instrument are made available during the course of the 

comparison. 

For each type df instrument the procedure used to calculate the irradiance is described in the following. The 

notationsare: - - 

V^ Output of the thermopile 

UM voltage across heater (h) or Standard resistor (i) 

R. Standard resistor 

K calibration factor 

Ci correction factor for lead heating 

P electrica! power in the active cavities 

a) Ä-pyrheliometers: the current through the right or left Strip is measured as voltage drop across a Standard 

resistor and the irradiance obtained as : 

y = AT^l^ 

This corresponds tö the geometric mean of the irradiances at the time of right and left reading. Thus, the ratio to the 

reference is calculated using the geometric mean of the irradiances at the corresponding instantes. 

b) PACRAD änd HF type pyrheliometers: the irradiance is calculated from the thermopile Output V^(irrad) when 

the receiver is irradiated. The sensitivity is determined by the calibration during which the cavity is electrically heated 

and U), and U; are measured together with the corresponding thermopile Output V^(cal).Furthermore, the zero of the 

thermopile V^(null) is measured and taken into account, . 

, e) TMI type pyrheliometers: most are operated in thg 'normal' way, that is by calibrating the readout directly (for 

an irradiance of 100 mWcm*^ a value of 100 mV is displayed).The values are entered in Wm** and no irradiance 

calculation is neede^. Others are operated and evaiuated as HF type pyrheliometersd) 

Active cavity pyrheliometers : the irradiance is obtained from. P^^ averaged from the closed values before 

and after the open reading P^. The power ca!cu!ation aecording tp the prescription of the type of instrument: 

wRA P = Uj^, or P - ^ or P - t/^ —i 

' ^.' * ' ' - 

e) Other. instruments: for the NTP the thermopile reading is multiplied with its calibration factor after substraction 

öf the zerö. For the PCC3-005 the irradiance is evaiuated by the Operator (similar to an active cavity pyrheliometer 

with.reference and observätion phase). 

f) Reference values from PM02: As during the preeeding IPC PM02 is used äs the working reference instrument. 

the irradiance values of PM02 used as reference are obtained with the algorithm of the active cavity radiometers 

with P^,) as mean of the c!osed readings before and after the current open phase. At the end of the open phase, 8 

P°pcn readings are taken, separated by approxirhately 0^7s. The first of these readings is used as reference for the 

values entered by the terminals and the other 7 for the instruments connected to the analog data acquisition system 

at the appropriate time. The Standard deviation of these 8 readings is also used as quality control parameter to judge 

thestabilityoftheradiation. 

3.5. Auxiliäry Data 

The meteorological parameters are taken from the automaüe weather Station of the Swiss Meteorological Service 

located at PMOD/WRC. From this System 10 minutes values are available which are averaged over the period of 

a run. The values are: air temperature, relative humidity, atmospheric pressure (p.34), global radiation, sky radiation 

(p.31). Ciose to the measuring benches the wind speed and direetiön is measured, not as meteorological parameter, 

but as an indication öf the Situation at the measuring site (p.33). Mpreover, an instrument temperature is also given


(p.33). Sunphotometer measurements are used to determine total vertical optica! depth at 368,500 and 778 nm (p.32). 

The daily Ozone values are measured at Arosa and amount to: 28.09: 273.0, 2.10: 282.8, 3.10: 278.5, 9.10: 270.0, 

10.10: 260.0 and 11.10: 261.6 mcm (Dobsön units). 

4. Results 

A total of 36 runs taken during 7 days (1 to 11 runs per day) have been selected for the finai evaluation.- The 

value of PM02 readings are plotted in Fig.2.28 (p,31) and the individual ratios to PM02 on Fig.2.1-2.57 (pp.12-30) 

together with the frequency distribution of the data to ülustrate possible deviaüons from a normal distribution. The 

sky eonditions were not always ideal and the criteria for keeping a specific reading is based on the Standard deviation 

of the 8 readings of PM02, which had to be lower than 0.8 Wm"^. If this criterion was not reached the readings of 

all instruments at that particular time were dismissed. The mean results are summarized in Table 1!2 with the 

calibration faetdrs (C„ Q, C3) used in the evaluation and the WRR calibration factor from IPC VI if available. 

Instrument 

PM02 

PM05 

CROM 2L 

CROM 3L 

PAC 3 

MKVI-67814 

HF-18748 

PM06-5 

PMO6-10 

PM06-79121 

PMÖ6-80022 

PMO6r811104 

PMO6-811107 

PMO6-811108 

PMO6-850401 

PMO6-850407 

EPAC-12843 

EPAC-13219 

EPAC-13617 

HF-14915 

HF-15744 

HF-17142 

HF-18747 

HF-19746 

HF-21185 

HF-23725 

HF-27159 

HF-27160 

HF-27162 

HF-27798 

Calibration Cönstants 

C2 C3 

24.18 

31.615 

127.687 

127.549 

9962.6 .07 75 

10007. 10. 

19989. .07 75 

23/729 ' 

22.6395 

23.847 

23i9l5 

23.855 

24.031 

24.0887 

24.095 

24.046 

1.0035 

10079. 

10024. 

20010. 

20020. 

20020. 

20014; 

19975. 

20020. 

19970.2 

20030. 

20030. 

20020. 

20020. 

.064 

.064 

.066 

.066 

.066 

.066 

066 

.066 

Table 1.2: Ratios to PM02 and WRR-WSG 

Comments 

WRR (IPC VI) 24^1546 

WRR (IPC VI) 31.6384 

WRR (IPC VI) 128.0215 

WRR (IPC VI) 127.4852 

WRR (IPC VI) 9965.59 

WRR (IPC VI) 10015.3 

WRR (IPC VI) 23.7314 

WRR (IPC VI) 22.7346 

WRR (1987) 

WRR (IPC VI) 23.9205 

Charäcterization 1982 

WRR (IPC VI) 24.0120 

Change in electronics 

WRR (1985) 

WRR (1986) 24.196 

WRR (IPC VI) 

WRR (IPC VI) 

WRR (IPC VI) 10052.1 

WRR (IPC VI) 19978.4 

WRR (IPC VI) 20020.6 

WRR (TPC VI) 19982. 

WRR (IPC VI) 19998.6 

WRR (IPC VI) 19973.8 

WRR (IPC VI) 

Ratio to PM02 

with C used 

1.00000 

.99881 + .00092 

' .99651 + .00140* 

1.00054 ± .00140 

.99917 ± .00085 

.99850 ± .00090 

(1.00022 ± .00197 

1.00073 ± .00417 

.99717 ± .00219 

.99320 ± .00090 

1.00232 ± .00090 

1.00044 ± .00119 

.99995 ± .00153 

.99947 + .00087 

1.00085 + .00189 

.99141 ± .00187 

1.00152 + .00169 

1.00031 + .00541 

.99716 + .00193 

1.00104 + .00129 

.99976 ± .00098 

1,00244 ± .00158 

1.00027 + .00132 

.99790 ± .00122 

1.00012+ .00161 

.99838 ± 00188 

1.00016 ± .00113 

1.00217 ±.00115 

, .99907 ± .00133 

L00107 ±.00146 

Ratio to Change Fig. 

WRRwsG PP*^ ' page 

-.99951 -487 

1.000H 113 

.99984 -157 

1.00060 603 

1.00003 33 

.99989 -107 

31 

12 

12 

12 

13 

13 

1.00078)') 13 

1.00140 1396 14 

1.00192 1924 14 

.99376 

14 .. 

L00312 3117 15 

1.00101 15 

.99969 -306 15 

1.00003 16 

1.00142 16 

.99816 16 

1.00209 2085 

1.00088 1 875 

17 

17 

1.00052 520 17 

1.00002 .23 18 

1.00035 . 354 18 

1.00110 1102 18 

1.00007 65 19 

.99840 -1597 19 

1.00069 19 

.99894 1056 20 

1.000731 20 

1.00274 20 

.99963 

21 

1.00164 

21 

') After the comparison a bug was found in the cavity; although it was not in beam the results have to be discarded. 

5

IPC VII Part 1: Measurements änd Results 

MKVI-67401 

MKVI-67502 

MKVI-67604 

MKVI-67702 

MKVI-67915 

MKVI-68016 

MKVI-68018 

MKVI-68025 

. MKVI-69036 

A-7 . 

A-171 

. A-212 

A-559 

A-564 

A-568 

A-576 

A-578 

A-6549 

A-7190 

A-7191 

A-7636 

A-9003 

A-13444 

A-15192 

A-16491 

A-18587 

^ PCC3-0Ö5 

NIP-18653 

1.0028 

1.0039 

1.0028 

1.0035 

1.00406 

1.0037 

1.0046 

1.0020 

1.0020 

30044.3 

5715. 

10535, 

5724. 

5913.6 

5767. 

5885.6 

6241. 

4418.6 

4586. 

4502. 

4321.4 

4564.8 

4428.67 

4479. 

4540, 

4516.3 

50.9933 

9.6 

Table 1,2: Ratios to PMOl^nd WRR-WSG (cont.) 

3.0 

2.0 

250 

WRR (IPC VI) 1.00486 .99956 ± .00134 1.00218 2179 

WRR (IPC VI) 1.00236 1.00058 ± .00132 .99961 -391 

WRR(IPC VI) 1.00373 .99711 ± .00123 .99860 -1402 

WRR (IPC VI) 1.00066 1.00127 ± .00129 .99900 -1000 

WRR (IPC VI) 1.00583 1.00071 ± .00126 1.00304 3040 

WRR (IPC VI) 1.00353 .99836 + .00124 .99876 -1245 

1.00074 ± .00090 1.00131 

.99997 ± .00172 1.00054 

.99854 ± .00101 .99910 

WRR (IPC VI) 

.99835 + .00153 .99891 -1086 

WRR (IPC VI 

.99902 + .00244 .99958 -416 

WRR (IPC VI) 10527.8 .99858 ± .0Q224 .99846 -1539 

WRR (RPC-VI IV) .99838 + .00363 .99894 -1056 

WRR (IPC VI) .99754 ± .00354 .99810 ^1897 

WRR (IPC VI) 

.99845 ± .00234 .99901 -986 

WRR (IPC VI) .99837 + .00304 .99893 -1066 

WRR (IPC VI) 6237.3 .99779 ± .00141 .99776 ^2239 

..98726 ± .00238 .98782 

WRR (RPCrVI IV) .4616. .99527 ± .00444 .99583 

WRR (RPC-VI IV) 4544. . .99255 + ,00772 .99311 

WRR (IPC VI) ' 

WRR (IPC VI) 

.99793 + .00147 .99849 -1507 

^99966 ± .00499 1.00022 224 

.98909 + ,00146 .98965 

WRR (Budapest 1987) 1.00030 ± .00216 1.00087 $65 

1.00374 + .00200 1.00431 

WRR (IPC VI) 

.99442 + .00354 .99498 -5029 

1.00085 + .00477 1.00142 

.99527 + .00211 .99583 

The mean of the ratios öf all absolute radiometers having participated in IPC VI (26 instruments) amounts to 

1.00039 ± .00131 and the mean taking all (including the A-pyrheliometers, 37 instruments) is .99984 + .00156. These 

results demonstrate the stability of the WSG and most of the instruments. In order to define the WRR for the 

evaluation of JPC VII the results of the WSG members are analyzed first. According to the decisions of CIMO IX 

the WSG consists of PM02, PM05, CROM 2L, CROM 3L, PAC 3, HF 18748 and the MKVI 67814. After the 

comparison a bug was foünd in the cavity of HF 18748; although it was not in beam its results have to be discarded. 

6 

21 

22 

22 

22 

23 

23 

23 

24 

24 

24 

25. 

25 

25 

26 

26 

26 

27 

27 

27 

28 

28 

28 

29 

29 

29 

30 

30 

30

IPC vn Part 1: Measurements and Results 

The remaining 6 are used to deHne the WRR with their WRR factors of IPC VI. The WRR result qf each WSG 

instrument can bc calculated from 

and yields the follöwing WRR values: 

WSG Instrument 

PM02: 

PM05: 

CROM 2L: 

CROM3L: 

PAC 3: 

MKVI 67814 

Mean: 

.. ' . , * \ - '< ' ' ' 

fwRR(X) - X/fwm,(PM02) WRR(X) Deviation 

6.99895 ' (1.OOOOO/099895) 

1.00074 ' (0.99881/0.99895) 

1.00278 -(0.99651/0.99895) 

0.99950 -(1.00054/0.99895) 

1.00030 -(0.99917/0.99895) 

1.00083 -(0.99850/0.99895) 

1.00000 

1.00060 

1.00033 

1.001Ö9 

1.00052 

1.00038 

1.000487 

The Standard deviation of the mean for all 6 WSG instruments amounts to 10*^=361 ppm. The deviations of PM02 

and CROM 3L exceed lo* which might be due to a real change of the instrument or the influenae of the atmospheric 

eonditions being different from IPC VI. The mean is not significäntly changed (-27 ppm) if they are left out, only 

the Standard deviation is decreased to 124 ppm. Thus, the WRR is well represented by the mean of the WSG and 

the results shown in Table 1.2. This choice of the WRR is also süpported by the results from the partieipating 

instruments having IPC VI WRR factor. The mean deviation pf all absolute radiometers (inciuding 'the WSG) is 

about Icwsaand 387 ppm above one or about 0.5o*wsG and* 163 ppmbelow one if the A-pyrheliometers are included. 

ppm 

-487 

113 

-157 

603 

33 

-107 

7

IPC VII Part 2: TäMes and Figures 

8 

IPC VU Part 2: Tables and Figures 

Table 2.2: View limiting geometries of absolute radiometers and NIP 

Instrument Dimensions[mm] 

R r I 

PM02 3.6 2.5 85,0 

PM05 , 3.7 .2.5 95.4 

CROM 2L 6.29 . 4,999 144.05 

CROM 3L 6.25 5.0 144.0 

PAC 3 8.18 5.64 190.5 

HF 18748 5.81 3,99 134.7 

MKVI 67814 8.2 5.65 187,6 

PM06 genertc 4.1 2.5 94.0 

PM06-5 3.6 2.5 84.2 

PMO6L10 4.25 . 2.5 95.4 

EPAC ggheric 8.32 5.64 190.5 

HFgeneric 5.81. 3,99 . 134.7 

MKVI genertc 8.2 5.65 187.6 

MKVI-67401 8.2 5.64 190.5 

PCC3-005 10.0 5.0 114:5 

NIP-1865.3 10.3 4.0 203.0 

R t radius of front aperture, r : radius of receiver aperture, ! : distance between apertures 

Table 2,2: View Iimitihg geometries of A-pyrheliometers 

Instrument Dimcnstons [mm] 

1 v w 

A-7 150.0 . . 9.5 7.5. 

A-171 ,. 72.2 10.25 2.4 

A-212 50.0 11.8 2.5 

A-559 70.0 10.0 8.0 

A-564 75.1 10.3 2.5 

A-568 55.5 10.6 4.0 

A-576 . .82.0 10.0 2.5 

, A-578 70.5 10.3 2.5 

A-Eppley 111.0 10.3 4.1 

V, w : half tength of the sides df the front aperture rectangle.J : distance between receiver and front aperture

E. Bagarukayo 

DepL of Meteoroiogy , 

Min. Environment Prot. 

P.O. Box 7025 

Kampala 

Uganda 

Tel: ..25 6 41 258 537 

B. Ben M'Rad 

Ihst. National de la Meteorologie 

BP. 22 ;. 

2035 Tunis Carthage . 

Tunisia . 

Tel: ..21 61 782 400 

Fax: ..21 61 784 608 

M.C. Bcrdah! 

Tcchn. Measurements, Inc. 

RO. Box 838 

Lä Canada, CA 91012 *' 

U:S.A. 

Tel: ..I 818 248.1035 

Fax: ..i 818 790 4257 

H. Boyen 

IRMB 

3, avenue Circulairc 

B-1180 Bruxelles 

Tel: ..32 2 373 0626 

Fax: ..32 2 375 5062 

A. Chäbane 

O N M Dar-Et-Beida 

Route de. §idi-Mouissa 

Algcr - 

A!gir ' 

Tel: .21 ß 250 8950 

Ai Chevalier 

IRMB 

3, avenue Circulaire 


Tel: ..32 2 373 0602 

Fax: ..32 2 374 6788 

Table 2 J: Address Hst of the Participants 

M, Coliins 

Nadönal Radiation Centre 

Meteoroiogicai Office . 

Beaufort Park 

Eästhampstead 

UK-Wokingham, RG11 3DN 

Tel: .^44 3 4485 5879 

Fax: ..44 3 4485 5878 

Dr. D. Crommelynck 

I R MB 

3, Avenue Circulairc 


Tel: ..32 2 373 0600 

Fax: ..32 2 374 6788 

Dr. L. Dahlgren 

Swedish Meteo. Hydro. Inst. 

S-60176 Nörrköping 

Tel: ..46 11 158 186 

Fax: .;46 H 158 26! 

T.de Lange ' 

Geophys. Inst, Dept. Meteo. 

University of Bergen 

Aüegtcn 70 

N-5007 Bergen , 

Tel: .47 5 212 687 

Fax: ..47 5.960 566 

K. Dehne 

Meteorologisches Observatorium 

Deutscher Wetterdienst 

Frahmreddcr 95 

D-2000 Hamburg 65 

Tel: ..49 40 601 73220 

Fax: ..49 40 601 73299 

S.V. Desikan 

Instruments Division 

Meteorological Office 

Poona 411 005 

India 

Tel: ..91 0212 339 015 

Fax: ..91 0212 58 289 

tPC VII Part 2: Tables and Figures 

F.M. El.-Hussainy 

Meteorological Authority 

Koubry El-Quobba 

Cairo 

Egypt 

Tel: ..20 2432 830 105 

B.W. Forgan 

Bureau of Meteoroiogy 

GTOBox 1289K 

Melbourne, Victoria 3001 

Aüstralia 

Fax: ..61 3 669 4050 

T. Grajnar 

Atmosph. Environment Service 

4905 Dufferin: Street 

Dowhsview, Ontario M3H 5T4 

Canada 

Tel: ..1 416 739 4464 . 

Fax: ..1 416 739 4521 

K.J. Gregory 


GPO Box I289K 


Aüstralia, 

Tel: .,61 3 669 4050 

Fax: ..61 3 669 4168 

Dr. J.R. Hickey 

Eppley Laboratory, Inc. 

12 Sheffield Avenue 

P.O.B. 419 

Newpört, R.I. 02840 

U.S.A, 

Tel: .1 401 847 1020 

Fax: .1 401 847 1031 

A. Joukoff 

IRMB 



Tel: ...32 2 373 0623 

Fax: ..32 2 374 6788 

9

IPC VII Part 2: TaMes and Figures 

R. Kenzari 

Inst. National de la Meteorologie 

BP. 22 

2035 Tunis Carthäge 

Tunisia 

Tel: ..21 61 782 400 

Fax: ..21 61 784 608 

V.A. Klevantsova 

Main Geophysical Observatory 

Karbyshcva 7 

Leningrad 194018 

U.S.S.R 

Tel: ..7 812 247 0103 

Fax: ..7 812 247 8661 

M;V. Klimovskaya 

Main Geophysical Observatory 

Karbysheva 7 


USSR 

. Tei: ..7 812 247 0103 

Fax: .,7 812 247 8661 

L. Laitinen 1 

Finnish Meteoroiogicai inst. 

Box 503 

Vuorikatu 24 

SFÔOlOl Helsinki 10 . 

fei: ..35 8 0192 9443 

E.G. Laue 

Jet Propulsion Laboratory 

4800 Oak Grove Drive 

Mai! Stop 125-177 

Pasadcna, CA 91109 

U.S.A. 

Te!: ..1 818 354 3304 

Fax: ..1 818 354 8153 

L. Liedquist 

Physics and Electrot&hnics 

Swedish Nat-Testing + Res.Insti 

Box 857 

S-50115 Boras 

Tel: ..46 33 165 448 

Fax: ..46 33 135 502 

TaMe 2 J: Adresslist of the Participants (cont.) 

M- Lombaerts 

IRMB 



Tel: .32 2 373 0602 

Fax: ..32 2 374 6788 

Dr. G. Major 

Inst, for Atmospheric Physics 

P.O.Box 39. 

H l675 Budapest 

Tel: 0036 1 585 711 

Dr. A. Manes \ 

Director, R&D 

Meteorological Service 

P.O.Box 25 

50250 Bet Dagan 

Israel 

Te!: .,97 23 968 2187 ; 

Fax: ..97 23 968 2126 

B. McArthur 


4905 Dufferin Street 

Downsview, Ontario, M3H 5T4 

Canada 

Te!: ..1 416 739 4464 

Fax: ..1 416 739 4521 

Dr. F. Miskolczi 


P.O.Box 39 

H-1675 Budapest 

Te!: ..3 61 158 5711 

G.M. Muchemi 

Kenya Meteo. Dept. 

Min. Transp. & Communication 

P.O. Box 30259 

Nairobi 

Kenya 

Tel: ..2542 56 788 018 

A. Muhlia V. 

Insütuto de Gebfisica 

Univ. Nac. Autonoma de Mexico 

Circ. Ext., Deleg. Coyoacan 

04510 Mexico D.F. 

Mexico 

Tel: ..52 5 *572 36 22 

Fax: ,.52 5 550 2486 

Z. Nagy 


P.O. Box 39 

H-1675 Budapest 

Tel: . 36 1 158 5711 

D.W. Nelson 

ARL/GMCC /R/E/AR4 

NOAA 

325 Broadway 

Boulder, CO 80303 

U.S.A. 

Tel: ..1 303 497 6662 

Fax: ..1 303 497 6290 

N. Nnodu 

Headquarters 

Meteorologica! Department 

Private Mai! Bag 12542 

Lagos 

Nigeria 

Tel: .23 41 633 371 

P.M. Növotny 


P O. Box 1289K 


Australia 

Tel: ..61 3 669 4050 

Fax: ..61 3 669 4168 

J. Olivieri 

Centre Radiometrique 

Meteorologie Nationale 

P-8426oCarpentras 

Tel: ..33 9063 1271 

Fax:, ..33 9060 1078

R.M. Ram&ez Martfhez 

Inst. Naciönal de Meteorologia 

Paseo de las Mqreras S/N 

E-Madrid 28071 

Tel: ..34 91 581 9738 

Fax: ..34 91 581 9767 

K.R. Rufai 

Headquarters 

Meteorological Department 

Private Mail Bag 12542 

Lagos 

Nigeria 

Tel: . 23 41 63 33 71 

K. Schulze 

WMO 

Case postale Nö. 5. 

1211 Geneve 20 . 

Tel: 022 730 81 11 

Fax: 022 73 40 954 

H. Shimura 

Japan Meteorological Agency 

1-3-4, Ote-maehi 

Chiyoda-ku 

Tokyo 100 

Japan 

Tel: . 81 3211 4966 

Fax: ..81 3211 2032 

Table 2.3: Adresslist of the Participants (cont) 

W H. Slob 

Royal NL Meteorological Inst. 

P.O.Box 201 

Wilhelminalaan 10 

NL-3730 AEDeBilt . 

Tel: .31 30 206 911 

Fax: .31 30 210 407 

J.A. Stallkamp 

Techn. Measurements, Inc. 

Box 838 ' 

La Canada, CA 91011 

U.S.A. 

Tel: ..1 818 248 1035 

Fax: .1 818 790 4257 

T.L. Stoffel . 

Solar Energy Research Inst. 

1617 Cöle Boulevard 

Golden, CO 80401-3393 

U.S.A 

Tel: :.l 303 231 1814 

Fax: ..1 303 231 1381 

W. Vandenborrc 

IRMB 

3, avenue Circulairc 


Tel: ..32 2 374 6787 

Fax: ..32 2 375 5062 


DJ. Wardle 


4905 Dufferin Street 

Downsview, Ontario M3H 5T4 

Canada 

Tel: ..1 416 739 4464 

Fax: .1 416 739 4521 

Ch. Wells 

Solar Energy Research Inst. 

1617 CoieBlvd. 

Golden, CO 80401 

U.S.A. 

Tel: .;! 303 231 1981 

Fax: ..1 303 231 1381 

Dr, E. Wcssely 

Zentraianstalt für Meteorologie 

und Geodynamik 

Höhe Warte 38 . 

A^l 190 Wien 

Tel: ..43 1 364 453 

Fax: . 43 1 369 1233 

G. Zclelew 

Nat. Meteorol. Service Agency. 

P.O. Box 1090 

Addis Ababa 

Ethiopia 

Tel: ..25 11 512 299 

11

IPC VTI Part 2: Tables and Figures 

12 

- 4+ 

Figure 2.1-23: Resuits of PM05, CROM2L, CROM3L 

IPC Vn Results for PM05/PM02: .99881 * .00092 n=191 

-t L. -< ) < t ' ' ' t ) ) ' ' ' ' ) ) ) t—) t t ) t—Lj—)—L—

2009 .0640 

2909 .0910 

2609: .0940 

2509 .1100 

2609, .1130 

2809. .1200 

2809. .1230 

2809. .1300 

2609. .1330 

2809. 1400 

2609. .1620 

02fÖ. .1230 

0210. .1430 

0210 1500 

0210. 1530 

0310. .1000 

0310. 1045 

0310. 1115 

0710. 1045 

0910. 1212 

0910. 1242 

091Ö. 1312 

1010. 0845 

1010. 0916 

1010. 0945 

1010. 1042 

1010. 1112 

1010. 1242 

1010. 1448 

1010. .1518 

1110. 0630 

1110. .0900 

1110. .0930 

1110. .1000 

liio. .1030 

1110. L1100 

-1 

Deviation from PM02 in X Deviation from PM02 in X 

t ! I 

)., ) t ! ) ! 

! ! I' I I ! ! I 

"3 

ta 

C. 

? 

O. 

^ 

. 

CD 

-

IPC Vn Part 2: Tables and Figures 

14 

t*: 

t - 

t - 

= 4-. 

Figure 2.7-2.10: Results of PM06-5, PMO6-10, PM06-79121 

IPC Vn Results for PM06-5/PM02: 1.00073 * .00417 n=179 

J I ) I L ) t ) t < ) < ) L-i-J ) ! ) t t t ' ' ' ' ' ' ' ! [ L- 

+ 

+' '+ 

+++ #+ 

+ 

+ + 

+ ' 

' +- ' 

+* 

'+' 

+' 

+ 

+. +^ ++ 

*i—t—t—t—

-1 

i i i i 

2809. .0640 

2609. .0910 

Z609. .0940 

2909. .1100 

c* - 

2609, .1130 

2809. .1200 

2809. .1230 

2809. .1300 

2609. .1390 ^ 

2609. .1400 ^ 

2909. .1620 

0210. .1230 

0210. .1430, 

0210. 1500 ^ 

0210. .1530 ** 

0310. .1000 

0310. .1045 

0310. .1115 

0710^ .1045 M 

0910, .1213 *** 

0910. 1242 

0910. .1312 

1010. .0645 

1010. 09i5 M 

1010. .0945 ** 

1010. .1042 

1010. .1112 

10101 .12^2 

1010. .1448 es 

1010. .1516 

1110, .0830 

1110, .0900 

1110, .0930 

1110. .1000 

Uio. .1030 

1110. .1100 a- t r 

Deyiaüon from PM02 in X Deviation from PM02 in X 

< :+ 

i ^ 

4? 

4+ 

3++ ! 

rt-! 

+. 

4 ! + 

) ) ] ) ! ! ! ! ! 

+ - 

*5 

t*3. 

ta 

s* 

s- 

o 

- ? 

C3 

o 

M 

CO 

CO 

CO 

CO 

O 

C3 

M 

P 

!) 

ca 

CO 

Ol - 

+4 

-4 

^1^ 

++ 

4 t 

^ ! 

+ r, 

! ! t ! J_tJ ( ! ! 

ca 

O 

o 

< 

09 

an 

o 

O 

o 

X 

CS 

Deviation from PM02 in X 

-.5 6 i.O 

Li_U H ! ! t i I 

++ 

4# 

:t4 

< 4 

:4 

41. 

L4 

! ! ! ] n ! ! [ I 

!=3 

5t) 

M - 

Deviation from PM02 in X Deviation from PM02 in X Deviation from PM02 in X 

^1.5 -1.0 -.5 0 

! H 1,1 1,1 ),! Lt ! ) I I I 

+ .4 

^4 

+ 4 

am 

m 

:+ 

t 

*3 

C3 

- 3 

K) 

3 -. 

O 

3 

o 

M 

a 

a 

o 

35 

M 

O 

R< 

H 

o 

a 

)0 . 

)*1 

7 

"4 

IPC VII Part 2: Tables and Figures 

Figure 2.16-2.18: Results of EPAC42843, EPAC-13219, EPAC-13617 

IPC VII Results for EPAC-12843/PM02: 1.00152 ± .00169 n=374 

j t—) [ J I I L 

+4 

' i i i t i ! i t 

^4 

z 

+ + ...-4- 

WS ^.^%4 -4+ ++ r- 

44 

44. + 

*T—i—r—I—i—i—i—i—[—t—r—r—i—t—i—t—i—i—i—t i t — i — I — t — i — r — i — r — i — i — — ) — r 

5 10 15 20 25 30 35 

4 

IPC VII Results for EPAC-13219/PM02: 1.00031 ± .00541 n=249 

+ 

4^4' 

4^. % 

'4 

4-tt,'444-. + 

4*^ 

"4^ 

) : ! L. 

4 

+ 4 

i i i i i i i i 

4+' 

+ 

'+ '4 

44+ '4 

10 15 20 

t 1 

& 

+ 4 4f 

# + 

+ 4 + 

4 

4+' -4-44- 

44- 

4r 

' 

4%. 

. 4 

) — i 1—t 

25 30 35 

IPC Vn Results for EPAC-13617/PM02: .99716 * .00193 n=246 

J I J ; I' ' ! t- ) 1 I I t- i t - ) t i t ! i ) ' ' t ! ) i ] ) ) L. 

4" 

-4-.i+#.- 

^1 

'"'4** 

4 4 

'^T 

4+^ 

.4^.4. 

^4 

i—t—i—1—1—t—rn—r—1—1—1—1—1—i—1—1—1—1—t—1—1—i—1—1—1—r—t—1— 

5 10 15 20 25 30 

4: 

4 

-4 

-f- 

n—ryi—i—! 

35 

^1 

^. ^. o S:- 

O o' O o' 

17


18 

a 

M 

O 

0k 

o 

A 

a 

e 

-3 

'P 

33 

a 

M 

O 

a 

o 

3 

a) 

'P 

Figure 2.!9-2.21: Results of HF-14915, HF-15744, HF 17142 

IPC VII Results for HF-14915/PM02: 1.00104 ± .00129 n=181 

i i ! t i i i i ! i t i ! ' i i i t i ! f t ; i i ' i i i — I — i — i j ] ] )_ 

-Mr. 

-H-. 4 

^ 

.4 

+r ^4 

- ) — i — 1 — i — 1 — T — i — t — i — i — i — i — i — l — t — i — t — i — i — i — t — i — t — t — i — i — i — i — ] — i — r — t r 

5 tO 15 20 35 30 35 

IPC Vn Results for HF-15744/PM02: .99976 * .00098 n=330 

I I ] I I ) I' I ) I I I I t I I I I [ I I; I t . I I I I I i < 

1—TT-]—[—]—y—]—]—I [ t — I — I — t — ] — [ — I — I — [ — ! — T 

5 10 15 20 

— t — t — i — t — r — [ — t — ) — t — r — i — r 

25 30 35 

IPC Vn Results for HF-17142/PM02: 1.00244 ± .00158 n=335 

I t t i i i i i I i ) I 

.+ 

* ^ r — ! — ) — t — r — t — i — r — ] — r 

5 10 

i — i — i — r * r 

15 

! ) ) 1 

' 1 ' 

20 

j ) t )—* I — i — ] I ] t- 

*T—r—r* 

25 

* i — r — t — r — f - 

30 

3 3 3 3 3 5 3 3 3 3 3 3.5 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 

±3^ 

35 

6r 

3


0540 

0910 

.0940 

noo 

4-+ 

1130 

1200 

1230 

1300 

1330 

3 

1400 

1520 

1230 

° 

1430 

1500 

-4 +-+ 3 

1530 °* 

1000 

1045 

++ + 

++ 09 

1115 

1045 M 

1212 

13 

SC 

.0945 

1515

Deviation from PM02 in X Deviation from PM02 

-.5 1.0 

I t I t t t ! I I I I I I 

44 

+4 

4 4t 

tu 

4^ 

4*-- 

11 ! I I m 

ta 

§ 

M 

^! 

t-^ 

OS 

es 

"0 

o 

M 

CS 

CS 

M 

CS 

CS 

tu 

n 

M 

tO 

tn 

: ) t t 

< 4- 

1.4 

' 4i 

4i 

47# 

44- 

: + 

!-r! 

^4- 

Eft 4- 

t t < < ) 

Deviation from PM02 in X 

-1.0 

-.5 

III). ,.! U. . t I N! 

4i4+: 7*4^+ 4 4^ 

44+ 4t-: 

++- 

4

Deviation from PM02 in % Deviation from PM02 in 

', ',_AJ ) 

^3 

4-^ 

4+ 

;+ 3 

3 

4+' 

ri rt 

OS 

CS 

13 

SO 

to 

OS 

es 

es 

CK i 

M _ 

et 

cx 

et 

-S 0 .5 

! ! ! ! t 11 ) ] ! ! ! ! 

4- 

4^ 

4^ 

4-4t 

4 

+ 

, f n t

IPC VII Part 2: Tabies and Figures 

22 

Figure 2.31-2.33: Results of MKVI-67502, MKVI-67604, MKVI-67702 

IPC Vn Results for MKVI-67502/PM02: 1.00058 * .00132 n=373 

' < < ) I ' ' ' ' ' ' ' t t _ j t t ] ) ) ] ) ) [ ] [ ) j ) ) ] [—t—) L 

a 

o 

t - 

'S 

---— ir**: ^ +** 

a 

) t . t I 

.5 

1 — ) — t — t — : — i — i — i — t — t — i — i — t — r * 

10 15 30 

.++ 

" 1 — I — ! — ) — ! — I — ! — ) — I — ! — I — 

35 30 35 

IPC VII Results for MKVI-67604/PM02: .99711 i .00123 n=349 

t 

) t t t t ) t t t t ! : t t—J t ) ) t t t t ) ), t i L. 

l — i — t — ) — t 1 !—i—]—i—t—t—)—n—irn—i—[—t—)—l—)—t—t—i—)—t—]—t—1—)—)—1—r* 4 

10 15 20 25 30 35 

IPC Vn Results for MKVI-67702/PM02: 1.00127 i .00129 n=353 

' ' ' ' ' ' ' ' ' ' ' ' ! ] ] ] ] t L. 

m - ++ 

-+-.+ 

-+ 

—— — 

10 15 

4^ 

20 25 30 35 

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 o o 3 3 3 3 3 3

2809 0B40 

2609 0910 

2609 0940 

2609 1100 

2809 1130 

2809 1200 

2609 1230 

2809 1300 

2809 1330 

Deviation from PM02 in X Deviation from PM02 in % 

-.5 .5 1.0 

LU 

''!''"! 

2809 1400 

2809 1520 

0210 1230 

0210 1430 

0210 1500 

0210 1530 

0310 1000 

0310 1045 

0310 1115 

0710 1045 M _ 

0910 1212 

0910 1242 

0910 1312 

1010 0845 

OS 

CO 

CS 

co 

13 

1010 0915 

1010 0945 

CS 

cs 

1010 1042 

1010 1112 

1010 1242 

1010 1446 

-h 

CS 

CS 

CS 

1010 1518 

1110 0830 

1110 0900 

CS 

1110 0930 

1110 1000 

1110 1030 

00 

1110 1100 


-l.o 

-.5 

!.! ! ! I I I 

2909 0940 

2809 .0910 

2909 0940 

4 

2909 1100 

CX 

2B09 1130 

2809 1200 

2809 1230 

2809 1300 

2B09 1330 

ZB09 1400 

2809 1520 

0210 1230 4r- 

0210 1430 

0210 ,1500 

0210 1530 ** + 44- 

0310 1000 

0310 1045 4++ 

0310 1115 

0710 1045 M 

0910 1212 

4-4- 4+ 

0910 .1242 

44 

0910 1312 

1010 0945 

4+ 

1010 .0915 

1010 .0945 "* !+rr*r 

1010 1042 

1010 1112 

1010 1242 4t- 

1010 .1445 M 

O 

1010 .1519 

1110 .0930 

.0900 

4t 

1110 

.0930 

44 

1110 

1110 1000 

1110 1030 *^ 

1110 1100 

L! ! t t 

3 

PO 

ta 

o 

- j 

13 

SS 

o 

M 

CO 

tO 

CO 

M 

o 

tn 

M 

P 

H 

M 

CO 

cn 

cx - 

M - 

1.0 

I ) < : i ] : ) t 

a 

o 

a 

o 

33 

a) 

'P 

.a 

M 

a 

'p 

4) 

.3 

M 

O 

Figure 2.40-2.42: Results of A171, A212, A559 

IPC Vn Resulta for A-171/PM02: .99902 * .00244 n=306 

! t t J t—! L ' ' ' ' 4- t t -< i—j ), t t 

4^-1- ,--.-JL_+.-tr__j4-___4, 

* i — i — r 

5 

! ' ' ' 

10 15 -r-!—r-r- 

20 

+ 

IPC VÜ Part 2: Tables and Figures 

. ^.— ^— 

4*-++ 

" i — i — i — i — r 

25 

43: 

T-t—[ 

)—!—I 

30 35 

IPC Vn Results for Ä-212/PM02: .99858 * .00224 n=264 

J L. J ] < ! L. -) ) < ) t-J t t- ' I L--L-J ] t L 

4-4i,' 4- 

,_.^...^......4.^..........+ . + + 

.OHIO 

.0910 

.0940 


-l.o -.5 

I ! ! !.D !.!.! 

1100 

1130 

1200 

1230 

+,+ 

:++% 

1300 4t- 

1330 

4-4- 

44 

1400 ° tu4: 

1520 

1230 

1430 

:+4--c 

4#* 4- 

1500 

1530 * *^ 

W4- 

41- 4* + 

1000 

1045 

1115 

1045 

4-4- 

4- 

44- 

4- + 4^ 

„ 

1212 ° 

M 

.0945 °* 

44- 

4^ -t- ++t: ++ 

44- # + 

4-+ + t 

1515 ° dt- 

ca 

1030 *^ 

n 

4-4-:4j 

4-4-+!+^ .4- 4- 4- 

4- + 

-4- 

4*! 

^4 

3 

so 

CS 

to 

t? 

o 

en 

o 

CO 

CO 

09 

M 

O 

o 

M 

C3 

2809 0640 

2809 0910 

2B09_0940 

2609_1100 

2809_1130 

2809_1200 

2809 1230 

2809 1300 

2809 1330 

2809_1400 


-1.0 -.5 0 

i,! H U LH ],! ) i !,! ! 

+ #4# 

4+4'-+ 

^ + +44- 

?-.^4++,+ 

4?++ + + 

4+-!L+ 

2809 1520 + ^4. 

0210_1230 

0210_1430 

0210_1500 

0210 1530 

0310_1000 

0310_1045 

0410_H15 

0710_1045 

0910_1212 

0910 1242 

0910_1312 

1010 M45 

1010JM15 

1010_0945 

1010_1042 

10101112 

1010_1242 

1010_1446 

1010_1518 

H10_0830 

1110_0900 

1110-0930 

Hioiooo 

1110-1030 

U10_1100 

4+ 

++ 

4+ 

+ + 4+ 

+ + 

^4 

++ + 4 

4+ 

4+, 

+ + +* + 

4+ 

+ 44- 

rrrn rrm 

+ 4i 

11) ] ! 11 

3 

J 

00 

2809-0640 

2809_0910 

2B09_0940 

2809-1100 

2809-1130 

2609 1200 

2809 1230 

2609-1300 

2809_1330 

2609_1400 

2809 1520 

0210_1230 

0210 1430 

0210-1500 

0210 1530 

031C1000 

0310-1045 

0310_1115 

0710 1045 

-1 


^4 

+ + 

++ 

++ 

++44+ 

+ ++ +t 

4tW 

++ 

4 ^ 

4^^ 

4+t+" ++ =t^. 

. + + 

+ + 

+ ' 4^+ 

.+.+ 

++;b 

0910_1212 + + 

0910 1242 

+ + 

0910_1312 

+ 4* 

4f +t= + + 

1010 0645 

4+ 

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Figure 2.61-2.63: Verticai Optica! Bepth at 778, 500 and 368 nm 

IPC VH: Verücal Opücal Depth 778 nm 

< - ' ' ' ' ' 1 ' ' ' ' ' ' < ' ' ' ' ' ' ' ) t t t t-J L—J—t—t—)—) 

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IPC Vn: Verücal Opücal Depüi 368 nm 

35 

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IPC VM Pärt 2: TaMes and Figures 

Figure 2.64-2.66: Instrument Temperature, Wind Speed and Direetiön at Measuring Site 

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35 

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33

IPC VII Pärt 2: TaMes and Figures 

34 

Figure 2.67-2.69: Air Temperaturen Relative Humidity and Atmospheric Pressure 

D?C VH: Air Temperature 

o j ] t t t t i t ) ! < t t t t ' ' ' ' ! t ) t t ' ' ' ' ) ) < ) ) t t r 

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IPC VH: Relative Humidity 

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TaMe of Contents 

IPC VII Part 3: Contributions to Symposium 

V.Klevantsova: Solar Radiation Measurement Metrology in USSR . ... .. 36 

LJ.B.McArthur, C.T.McElroy, DJ Wardle: The Use of a Self-scanning Photodiode Array 

in Sunphotometry. 37 

T.Stoffel: HBCU Solar Radiation Monitoring Network ...42 

PNovotny: Australian Radiation Network Plans ... 48 

T.Stoffel: Solar Radiation Research Laboratpry at SERI 53 

K.Dehne, U.Bergholten WMO Sunshine Duratiön Measurement Comparispn 1988/89 in Hamburg . 59 

J.Romero, N Fox, CJfÖhlich: Solar and Cryogenic Radiometrie Scales: A Preliminary Comparison — ........ 65 

I.RÜickey, R.CPrieden, DJ-Brinker Expehence with a Radiometer Cavity in Space ............. 66 

K,Dehne, U.Bergholten IEA Comparison of Leng-Wave Radiometers in Hamburg 1989/90 67 

Ch.Wehrli, CFröhlich: Sunphotometer Calibration and Results 73 

J.L.Bravo, AMuhlia: Some Statistical Aspects Results from the First Regional AR-IV 

Pyrheliometric Intercompansoh at Ensenada, Mexico < .'75 

LOiiyieri, SJMevel: Experience with CM-15 79 

K.Dehne, L.Liedquist, L Dahlgren: IEA Global Radiation Reference Radiometer Comparison ............ 85 

D Crommelynek, AJoukoff: Estimatiön of Spectral Radiation Distribution from Global Radiation 91 

/ 

35

IPC VH Part 3: Contributions to Symposium 

SOLAR RADIATION MEASUREMENT METROLOGY IN USSR 

VA.Klevantsova and M.VKlimovskaya 

Voeikov Main Geophysical Observatory 

Karbysheva 7 


USSR 

This is the abstract of a paper presented at the Conference "New Developments and Applications in 

Opücal Radiometry III", September 20-22 at Davos and will appear in the proceedings published as a special 

issue ofMetrologia. 

The probiem of traceabiHty of measurements of solar radiation in USSR and transferof measurement unit 

to working instruments is discussed. In 1987 the State Standard of USSR has approMed thecomposition of 

radiation Standard group consisting of the absolute cavity pyrheliometer with cooled receiver, PCC3-005 and 

the A compensation pyrheliometers: A 212, A 250, A 196. Comparisons are made every year between the 

readings of the Standard group instruments and the results demonstrate good stability (inter-annual changes 

of less than 0.3 %). The limit of esümated error of radiation measurement at the stations of the radiometric 

network in the USSR do not exceed the following values (95% confidence level): 

36 

pyrheliometer 

pyranometer 

net-pyrradiometer 

3% 

11 % 

20%

Abstract 

The Use of a Self-scanning Photodiode 

Array in Sunphotometry 

LJ.B. McArthur, CT. McElroy, D.I. Wärdle 

Atmospheric Environment Service 

Downsview, Ontario, Canada, M3H 5T4 

Tins paper was presented at: 

New Developments and Applications in 

Optical Radiometry III 

20 - 22 September 1990 

Davos, Switzerland 


The use of self-scanning photodiode arrays is Well established for low-light intensity multi-specträl 

measurement Systems such as those used in spectroscopy and astronomy. Using the newly deveioped EG & G 

Reticon random äccess self-scanning linear photodiode array an mstrument has been deveioped for solar 

observations which overcomes the difSculties associated with these detectors at high light levels. By coupling 

this technology with fiat-Seld concave holographic grating technology from American Holographie ä 

"sunphotospectrometer" has been built. This instrument is presently able to scan 1024 Channels of spectral 

införmation in less than 1 second. A prototype instrument is being tested with a second generation version 

expected to fly aboard the US. Space Shuttle within the next two years. The design of this instrument is 

described and preliminary spectra are presented to ülustrate the measurement of NQ using this portable system. 

1 Introduction 

To overcome some of the difSculties found in handheld sunphotometry, the Atmospheric Environment 

Service (AES) pf Environment Canada has deveioped a "sunphotospectrometer" which avoids the use of 

interference filters and single eiement photodiode detectors. This instrument was originally designed to be flown 

as a mid-deck experiment aboard a NASA space Shuttle in the early 1990's. The main purpose of this 

experiment is to measure verticai trace gas and aerosol profiies through the earth's atmosphere by using solar 

and lunar occultations at 20 or more wavelengths sünultaneously. Since this original design, the use of similarly 

designed instruments för surface-based measurements of SOg, NO2 and O3 is also being considered. 

2 Instrument Description 

The sunphotospectrometer is a handheld, battery powered instrument construeted from commercially 

available 'state-of-the-art' components. Software control of the mstrument and Output storage are via high-speed 

serial Communications to an IBM-compatible laptop. The instrument is able to be operated for approximately 

6 hours using four 9 volt batteries to supply power to the electronics and a further six 'AA' battcries are used 

to operate the two on-board stepper motors. Induding these, the mstrument weighs less than 3 kgi 

The detector is anEG&G 1024SR random access self-scanning photodiode array consisting of two 1024 

photodiode sensors construeted on a common Substrate, öne for the detectipn of incident energy with the second 

used for the removal pf the majority of Rxed pattern noise. Each individual sensor within the array has 

dimensions of 2.5mm high by 25/im wide. This array is styled after an array Erst deveioped in the late 1970's 

by Reticon Corporation (presently EG&G Reticon) as a response to demands of the spectroscopy Community 

[1]. The S series array, the SR's predecessor, has been described in [1,2]. A number of application papers using 

these avaläüche arrays have shown their usefulness in medlcal x-ray imaging [3], inductively coupled plasma 

emission spectrometry [4], weak light stellar spectroscopy [5,6] and more recently in near-infrared spectroscopy 

[71- 

The layout of the main optical components is shown in Figure 1. Light enters the instrument through 

37


a 25 mm säpphire entrance aperture and is split between the spectrometer optics and the sighting optics by an 

osciliating beam Splitter. Eighty percent of the iight is reileeted into a 22 mm focal length F2.2 entrance iens 

which focuses a 2* field of view on the plane of the 2.5mm X 25pm slit. The transmitted Iight is used by the 

Operator to sight the instrument on the sun. The sht is imaged directly onto the photodiode array with an 

American Holographie concave diffraction grating, modei 44633. This is iocated 92 mm from the sht on an 

angle of 13.6* from the grating normal. The Hat Held grating disperses the light Over an angle of 14.? such that 

the spectrum is focused on the array at an average distance of 97^5 mm ± 0.05 mm. The grating is used in the 

first Order with a waveränge between 400 and 900 nm. This grating has a relative efficiency of 28% at 400 nm, 

peak at 29% ät 450 nm and then slowly and nearly monotonically decreasing to 14% at 9Ö0nm. The use öf a 

concave Bat-Reld grating reduces optical components and eliminates any moyements associated wth individual 

photodiodes, when used with array detector technology. 

Two instrument stepper motörs controlled by the on-board microcomputer are used to enhance overall 

Performance. Motor one, located inside the spectrometer box, controls the positioning of a double "filter" wheel, 

one of which contain optional blocking filters, while the second aecommodates live irises. By setting the iris and 

then reversing the motor to set the blocking filter up to 25 cbmbinations can be selected dependent upon light 

levels and the wavebänd being measured. The second motor, mounted at the rear of the instrument, operates 

the osciliating beam splifter. This is used to step the 2* total field of view of the instrument across the slit in 

steps öf 0.05^ at a rate öf 80 steps per second. Because the instrument is handheld shght movements by the 

observer will image different parts of the solar disk onto the entrance slit. By driving the field of view across 

the slit to obtain an Observation at each step, with a 50% overlap, observer error can be corrected to obtain 

maximum verticai resoiution. A further benefit of moving the image aeross the slit is the potential of obtaining 

solar aureole measurements during the occultation which wöuld äid in the determination of atmospheric aerosol 

characteristics. 

Light transmitted through the osciliating beam sphtter is focused by ä 30 mm plano-conVex lens though 

a onto an imbedded cross-hair. This, in tum, is magniRed by a pair of 8mm and 9mm bi-convex lenses onto two 

frosted viewing screens by means of a 50/50 beam sphtter. The design enables the observer to use the 

instrument in a manner either similar tö a übw camera" or4he-^ne^M^-!!t!ee!!îAe^bnsâMt^men&- The 

sight has a 5* field of view to aid in locating the sun before the measurement sequence begins. 

3. Measurement of NOg 

The concentration of NC^ has long been of interest to the atmospheric sciences Community. The highly 

struetured absorption spectra of this species between 320 and 650 nm makes it relatively easy to identify. 

Furthermore, the very high absorptivities of NC^ between 380 and 450 nm provide an excellent means of 

identifying it even when part of the more complex mix of pollutants normaüy found over populated areas. To 

test the abihty of the instrument to measure NOg several unknown amount^ were compared using the 

sunphotospectrometer and the Perkin-Elmer Lambda 9 spectrometer. Figure 2 illustrates the results of one 

comparison between 475 and 525 nm for a concentration of 0.012 cm of NOg in a laboratory cell. The 

sunphotospectrometer used a 25/* m slit and had a photodiode integration time of 100 p s. The complete spectra 

was obtained in under 2 seconds. The spectra obtamed by the spectrometer has been degraded to the resoiution 

of the sunphotospectrometer and graphed using the approximate midpoints of the sunphotospectrometer spectra. 

Such a spectra would require 5 minutes to obtain. The conversion from photodiode position into central 

wäveiength for the sunphotospectrometer is approximated using a wäveiength offset and an assumed constant 

dispersion. For this wavebänd ränge and this intercomparison these simplifications are sufficient. A more 

precise mapping algorifhm will be deveioped for the actual flight instrument. Even with these estünates it is 

apparent that the sunphotospectrometer has the resoiution to detect the major spectral strueture of nitrogen 

dioxide even in spectral regions beyond the peak absorption bands between 425 and 445 nm. The overall 

increase in transmittance shown for the hand held instrument cannot be categorically explained, but it is 

postulated tö be due to the Variation in the source lamp intensity used in obtaining the spectrum. In independent 

tests, the short-term Variation in the lamp was greater than ± 1% at shorter wavelehgths. 

38

4. Summary 

IPC VfJ Part 3: Contributions to Symposium 

An sunphotometer mstrument has been designed and construeted using photodiode array and aberration 

corrected concave holographic grating technology. The instrument is speeifieally designed -to be handheld, use 

little power and accurately measure the concentrations of trace constituents in the atmosphere. Preliminary tests 

using a early prototype confirm that NOg can b% identißed with the resoiution necessary to measure optical 

depths and its verticai distribution when using solar occültation techniques from space. Further Software and 

hardware developments are antieipated with coneurrent increases in the resolving power of the spectrometer. 

A final yersion of the instrument is expeeted to fly ä NASA Shuttle in mid-1992 as a mid-deck cabin experiment. 

6. Relerences 

1. Talmi, Y, änd R.W. Simpson, Apphed Optics, 19,1401 (1980). 

2. Simpson, R.W., Rey. Sei. Instrum., 50, 730 (1979). 

3. Cunningham, LA. and A. Fenster, Med. Phys,, 11, 303 (1984). 

4. McGeorge, S.W. and E.D, Salin, Spectrochimica Acta, 40B, 435 (1985). 

5. Vogt, S.S., RG. Tull and P Kelton, Apphed Optics, 17, 574 (1978). 

6. Walker, G.A.H., R. Johnson and S. Yang, Adv. Elec. Electron Phys. 64A, 213 (1985). 

7. Mayes, P.M. and J B. Callis, Apphed Spect. 43, 27 (1989). 

7. Figure Captions 

Figure 1. Schematic diagram of the sunphotospectrometer optical layout. 

Figure 2. A comparison of transmission spectra for 0.01 cm NOg at a 1 nm resoiution. The Lambda 9 

spectrometer data (solid) was obtained at a resoiution of 0.1 nm and degraded fo the resoiution 

of the sunphotospectrometer (dashed). 

39


Figure 1. 

40 

INPUT_ 

LIGHT 

CONCAVE HOLOGRAPHIC 

GRÄTING^—=\ 

FILTER 

MQTOR 

ENTRANCE 

LENS 

ENTRANCE 

SLIT 

SCILLATING 

^ - BEAM SPLITTER 

BAFFLE 

PHOTODIODE 

DETECTOR 

SIGHTINGU 

LENS/CROSSHAIRS 

OtSCILLATINC 

MOTOR 

BEAM 

SPLITTER SIGHTING 

EYE PIECE 

SIGHTING 

EYE PIECE

Figure 2. 

1.00 

(0 0.95 

0.90 - 


NO2 Transmittance Spectra 

1 nm resotution, 0.01 cm NO2 

Lambda 9 Spectrometer 

Sunphotospectrometer 

0.85 [ I I I ! ! 1,1 ) ) I i t ! I ) I ) I ) ) t ! ! I ! 1 ! I ) I I ) ! ! ! ! ! t I I ! ! ! ! ! ! I ] I 

475.00 485.00 495.00 505.00 515.00 

Wavetength (nm) 

525.00 

41


ABSTRACT 

HBCU SOLAR RADIATION MONITORING NETWORK 

T. Stoffe! 

So!ar Energy Research Institute 

Golden, Colorado 80401 

U.S.A 

The Historically Black Colleges and Universities (HBCU) Solar Radiation Monitoring 

Network has been in Operation since November 1985. Funded by the U.S. Department of Energy, 

the six-station network provides 5-minute averaged measurements of global and diffuse horizontal 

solar irradiance. The data are processed at the Solar Energy Research Institute (SERI) to improve 

the assessment of the solar radiation resources in the southeastern United States (Stoffel, 1989). Two 

of the stations also measure the directrnormal solar irradiance with a pyrheliometer mounted in an 

automatic sun tracker. All data are archived in the SERI Standard broadband forrrfat (SBF) with data 

quality-assessment indicators. Network data recovery has been better than 98%. 

1. BACKGROUND 

In i'981, President Reagan signed Executive Order 12320, directing all federal agencies to 

implement programs that couid strengthen the technicai capacity of the nation's Historically Black 

Colleges and Universities (HBCUs). In responding to this executive order and a subsequent 

congressional mandate (the Science and Technology Equal Opportunity Act), the Solar Energy 

Research Institute (SERI) noticed that the distribution of HBCUs in the southeastern United States 

corresponded with the lack of solar monitoring stations operated by the National Oceanic and 

Atmospheric Administration (NOAA). With funding provided by the U.S. Department of Energy, 

SERI deveioped a solar resource assessment project involving the HBCUs. 

The six-station HBCU solar-radiation monitoring network shown in Figure 1 is the result of 

a solicitation and selection proceSs that begaii in April 1984, when 22 HBCUs were invited to submit 

a letter of interest for participation in the project. Campus visits were arranged for the eight finalists. 

A source selection board reviewed the available information and made the final selection on the basis 

of geographic location, academic program, facilities, and faculty background and experience in the 

physical sciences and mathematics. 

2. STATION EQUIPMENT 

As shown in Table 1, all six HBCU stations measure the global and diffuse horizontal solar 

irradiance using the Eppley Laboratory's Precision Spectral Pyranometer (PSP). The pyranometer 

used to measure the diffuse solar irradiance is mounted under ashadow band. Two of the stations 

42

Columbia 

Lake Charles 

Nashvit e 

oMtsstsstppt vattey State 

. ) 

Montgomery 

'' ^ 

Tatlahassee 

. NOAA SOLRAD Network 

o HBCU/SER) Network 


Sterling 

Btuefietd State 

Êlizabeth City State 

Ratetgh 

oSouth Caröltna State 

Savannah State 

Bethune-Cookman 

Figure 1. HBCU and NOAA/SOLRAp stations in the southeastern United States 

TaMe 1. HBCU Network Stations 

Station Name 

Bethune-Cookman College 

Daytona Beach, Florida 

BlueSeld State College 

Bluefield, West Virginia 

Elizabeth City State University 

Elizabeth City, North Carolina 

Mississippi Valley State University 

Ifta Bena, Mississippi 

South Carolina State College 

Orängeburg, South Carolina 

Savannah State College 

Savannah, Georgia 

Solar Irradiance Measured 

Global Diffuse Direct 

X 

X 

X 

X X 

X 

X 

43


also measure the direct-normal solar irradiance with an Eppley Normal Incidence Pyrheliometer 

(NIP) mounted in a LI-COR Model 2020 Automatic Solar Tracker. 

A radiometer mounting platform was deveioped especially for this project (see Figure 2). The 

platform design and a list of readily available hardware materials was sent to each HBCU Station to 

aid on-site construction before a SERI scientist arrived for the final equipment Installation. 

SERI selected data-!ogging equipment to provide records of 5-minute and hourly averages, 

as well as daily totals of low-level direct current (de) voltage input Signals from the radiometers. The 

Campbell Scientific model CR21 is battery powered and capable of scanning each input channei every 

10 seconds, Converting the input voltages into engineering units (watts per square meter, W/m^), and 

recording averaged and total values. The primary recording is aecomplished magnetically on audio 

cassette tapes. Printed listings provide a backup record of the data in the event that the magnetic 

record is missing or unreadable. The printed data are also used for on-site data quality control and 

data base development because the information is available almost in real time and is presented in 

W/m^. The data-logging equipment is inexpensive and simple to operate, yet it provides the retiabitity 

needed to ensure that a high percentage of all possible data are collected from the network. 

* . . . . . 

Figure 2. Solar monitoring equipment mounted on a SERI-designed fixture at Bluefleld 

State College, Bluefield, West Virginia. (From left to right, diffuse radiation is 

monitored with an Eppley PSP under a shadow band; global horizontal radiation is 

measured with a second Eppley PSP; and direct normal radiation is measured with an 

Eppley NIP mounted in a LI-COR LI-2020 solar tracker.) 

44 

r -

3. TRAINING 

IPC VU Pari 3: Contributions tö Symposium 

It was essential that the Station staff achieve a thorough understanding of the equipment and 

its maintenance to realize the project's goal of coHecting high-quality solar radiation data for the 

SoutheasL We deveioped ä training seminar and field Operations manuai to introduce the project 

änd serve as a reference. The seminar was presented by a SERI scientist when the equipment was 

Erst installed. The Eeld manuai contains a thorough review of the basic Station Operations, and a 

copy was left at each Station. 

Several staff changes have occurred at the HBCU stations, owing to the use of students for 

the routine Operations. The faculty has done an excellent job of retraining new students. The 

success of the project can be attributed to the demonstrated interest and enthusiasm of the Station 

staff. 

4. STATION OPERATION 

Routine maintenance and operational checks are made daily at each of the six HBCU solar 

monitoring stations. Using a Standard log form deveioped at SERI (see Figure 3), the observer 

systematically checks and records the Station equipment functions and current meteorologica! 

eonditions. This Information is then available for data reduction and analysis at SERI. 

The completed log fbrms and printed data output are coHected and sent to SERI biweekly. 

This provides an important record of the station's Performance and can be used to identify probiems. 

By the third day of each month, the cassette tape in the data-logging system is removed from the 

recorder; it is then annotated with the Station name, date, and time of removal and mailed to SERI. 

A new cassette is prepared for recording the next month of data. This tape exchange can be 

aecomplished between the regulär data transfers from the data logger memory and the tape recorder 

so that no data are lost in the process. 

As part of the quality assurance requirements för the project, all radiometers and data loggers 

are recalibrated at SERI's metrology laboratory (Myers, 1988). When equipment failures occur, we 

diagnose the probiem over the teiephone and quickly send the necessary replacement equipment to 

the Station. 

5. DATA PROCESSING AND ANALYSIS 

About 500,000 characters are stored monthly at each Station on cassette tape. At SERI, the 

data are transferred from cassette to ASCII Eies on personal Computer (PC) diskettes, which also 

serve as the archive media för the original data. The ASCII files are then transferred to a VAX/VMS 

Computer system for analysis. Each 5-minute data point is then ässessed for quality, a monthly report 

is prepared (summary data in hourly and daüy intervais), and the data are archived in SERI's Standard 

broadband format (SERI, 1988). 

Our data quality assessment Software (SERI QC) assigns a 2-digit flag describing the outcome 

of the evaluations. No measured data are replaced or changed in any manner. The flag is positioned 

next to each data vame as prescribed in the SBF archival format. 

As a result of the interest and dedication of the HBCU participants, the average annual data 

recovery for the network has been better than 98%. 

45


SEM/HBCU Sotair Monitoring Station 

MAINTENANCE CHECKUST & WEATHER LOG 

Station Name: Mississippi Valley (MV) For the Period "4/-2'/9* to°y-/^7/7° 

DATZ AND TIMZ 

Day of Year 

Day of Week 

Month/Day/Year 

Standard Time 

Observer'3 Initials 

GLOBAL HORIZONTAL 

Dome Condition 

Sensor Level 

Desiccant 

Current Reading 

DITTCSZ HORIZONTAL 

Dome Condition 

Sensor Level 

Desiccant 

Current Reading 

Shading Band 

DATA ACQUISITICW 

Time Display 

Battery Voltage vctcjctoo 

Recorder Counter 

Tape Change (Y/N) 

Printer Status 

WBATHER OBSERVATION 

Cloud Amount 

Temperature °g 

C 

o 

M 

M 

E 

N 

T 

S 

3 

))) 

4** 

21 

'7M 

1/ 

^2- 

ZT- 

2.Q 2. 

"4 77V 

17" 

17^ 

f^7 

1?^ 

^7 

3-4- z.-7 

-

6. REFBRENCES 


Myers, D.R., 1988: Uhcerya/n/y y4na^M ^br 7%erwM%M/e J^rawwergr aw^f T^rAe/fomg^r 

Ca/^raffo/M PerfOHMea' ÊR/. SERVTR-215-3294, Soiar Energy Research Institute, 

Goiden, Colorado, 44pp. - 

SERI, 1988: -SER7 âwânf ßroa^6aAMf FowMf, v4 ô/ar an^ Meôro/ogfca/ Da/a ^rc/aw/ 

-Forma?. SERI/SP-320-3305, Solar Energy Research Institute, Goiden, Cotorado, 52pp. 

Stoffe!, T.L, and E.L. Maxweü, 1989: "Current Status of Solar Radiation Networks in the U.S." 

Piroc. iP6*9JiwwMaV Cow/grewcg v4wcncaM ô/ar Energy 6*oda?y, Denver, Coiorado, 

June 19-23, 1989. 

47

IPC Vn Part 3: Contributions to Symposium A 

48 

ABSTRACT 

AÜSTRALIAN RADIATION NETWORK PLANS 

P. M. V. Novotny 


Box 1289K 

Melbourne VIC 3001 

Australia 

Aüstralian Bureau of Meteoroiogy currently operates a solar 

radiation monitoring network, which was established in the late 

1960's consisting of 25 stations measuring global and diffuse 

solar exposure. The existing equipment reached the limits of its 

serviceable life and planning is in hand for the re-equipment of 

the network with a new generation system based on low maintenance 

and readily available modern technology. The implementation of 

the new system will enhance the quality of the data, and improve 

the quality control and data management. 

NETWORK HISTÖRY 

In the mid 1950's the Aüstralian Bureau of Meteoroiogy took 

over t^he responsibility for a small network rof 7 actinographs 

monitoring global solar radiation which was operated by the 

University of Melbourne. Following a survey of user requirements 

for the radiation data, including quality, quantity, and spatial 

distribution, the network was gradually upgraded, starting in the 

second half of 1960's. Low accuracy Sensors were replaeed by 

thermopile pyranometers, and a monitoring system, based on an 

analog chart recorder, mechanical integrator and electromechanical 

printer, was installed. The size of the network was 

increased to 22 stations monitoring global solar exposure, and 13 

at which diffuse solar exposure was monitored. The diffuse 

component of global exposure being monitored by a pyranometer 

with an occulting diBc driven by a synchronous motor. 

With the growing demand for solar radiation data at 

localities not previously covered by the existing network, nine 

stations were added to the network between 1982 and 1986, all 

monitoring both the global and diffuse exposure. Ät four new 

stations an in-house designed electronic integrator replaeed the 

mechanical integrator, and at five of the new stations an inhouse 

designed electronic integrator and electronic memory 

storage unit replaeed the mechanical Units. There has, been some 

fluctuation in the number of stations in the network for various 

reasons. The current number of active stations is 25.


All stations provide half hourly radiant exposures as either 

a hard copy printout br on a removable electronic membry storage 

unit, depending on the type of the Station, in addition to ä hard 

copy continubus chart of the irradiance. The data are transferred 

each month from the stations to the National Climate Centre (NCC) 

by mail for quality control checks and ärehival. 

CURRENT DATA QUALITY MONITORING AND SYSTEM PERFORMANCE 

The data quality control is applied at four levels 

consisting of: 

1. initial pyranometer ahd auxiliary equipment calibration 

prior to-the depioyment at the Station and on return from the 

Station.; 

2. Continuous maintenance and Performance monitoring öf the 

sensor änd däta acquisition system by the field staff at the 

Station. The sensor Performance is monitored by a comparison of 

ah actüal clear sky half hourly radiant exposure around local 

äppärent npon to an expeeted value. The data acquisition system 

timing is monitored and time marks are inserted on the irradiance 

chart. 

3. Regulär maintenance of the system and calibration checks 

of the auxiliary equipment by regional field teohnicians using a 

Standard voltage source. 

4. Central data bank quality control program Monitors long 

term trends in senior and data acquisition system Performance 

based on the results obtained at levels 1, 2 and 3 of the initial 

and field quality control and the results are applied as a 

correction to the räw data. Individual half hourly radiant 

exposures are compared to maximum expeeted values and the night 

time dark Signals and the relation between global and diffuse 

radiant exposures are monitored. Spurious data are flagged by a 

computerised quality control program and investigated using hard 

copy irradiance Charts änd any other relevant meteorological 

observations. Quality control leid and corrected data are then 

stored in the NCC central data bank. 

It is estimated that the uncertainty of the archived data is 

within 5% and 7% for half hourly global and diffuse radiant 

exposure respectively at solar elevationsgreater then 20°. 

Up to 20 years of data are available in the central 

ärchives of the Bureäu of Meteoroiogy National Climate Centre. 

It is apparent that with the current network, the data 

quality control and Management is labour intensive with a Iarge 

volume of manuai data processing required. The quality control 

program does not cover periods of measurement under other than 

Clear sky eonditions for global irradiance and is inadequate for 

diffuse irradiance. Maintenance of the network equipped with 

three different types of auxiliary equipment is demahding and 

49


extensive periods of data loss have occurred due to the 

increasing equipment failure and slow communication between 

stations and the central data quality control facility. Some pf 

the stations located in capital eitles do not provide 

representative data due to their exposure within the local 

polInted environment, These deficiencies have been addressed 

under the current Bureau capital re-equipment program and i t is 

expeeted that reliable data with smaller uncertainties will be 

obtained from a reconstrueted network. 

OUTLINE OF THE PLANNED SYSTEM 

The pbjeetive of the new solar radiation monitoring network 

is tö produce a reliable database of a broad band solar radiation 

measurement satisfyihg the needs öf users reqüiring long term 

climatological Information äs well as near real time data with a 

relatively high time resoiution. 

An efficient data quality control program managed by a PC 

based data acquisition System at the Station level will automate 

the quality control levels 2 and 3 noted above and provide 

objective information on the status pf a Station fünetion and 

data reliability. A daily communication of data and Status 

details via the Aüstralian telecommunication network to a central 

data management facility will provide near real time da^ta usefs 

with the required Information.and eoable the network management 

to täke immediate corrective action in case öf sub-system 

f ailures.. . 

. ^ 1 Th^ Station level quality control 

is in the redundancy of monitored parameters. The basic 

measurements are the 1 minute direct, diffuse and global exposure 

using first class sensors which are regularly characterised, and 

using the direct and diffuse components as a major eomponent of 

the information, with the global eomponent as a quality control 

indicator. Any discrepancy in the mutual relationship of 

monitored parameters will be evaiuated, interpreted and reported 

as both a warning to the Station staff to take a corrective 

action and as a data quality, flag to the central Office. Other 

quality control. indicators will mpnitor the dfift in calibration 

of the global pyranometer, the status of: an active sun tracking 

device proyiding for the measurement of direct and. diffuse 

irradiance; änalog/digitai conversion (zero, ränge, blas); 

individual sensors (temperature, cireuitry status); the system 

time base; and, the power supply. 

50 

The planned Aüstralian solar radiation network will consist 

of: twelve high quälity basic stations measuring direct, diffuse 

and global solar exposure and providing for the measurement of 

downward long wave radiation änd calculation , of sunshine 

duration; three high quality research stations monitoring the 

above pärameters on multiple basis as well as spectral 

measurements (Cape Grim, Darwin, Laverton); and; one high quality 

research Station (Alice Springs) taking part in the WMO Global 

Background Surface Radiation Network (GBSRN). A limited version


of the upgraded data acquisition System is also planned for 

installation on the existing stations located in Aüstralian 

capital cities. The distribution of stations within the network 

is shown in Figure 1. 

The minimum information yielded by the network will consist 

of 1 minute values of radiant exposures together with flux 

variance indicators and data quality flags. This information will 

be stored for use by specific research programs and use by the 

central data bank for the data quality control program 

(equivalent to level 4 above). These data will then be used to 

generate a database of radiant exposure for individual 

quantities. The high quality research stations and GBSRN Station 

will also provide the solar radiation information required by 

other Short and long term research programs. 

The re-equipment program is planned to commence in the 

second half of 1991 with total cost of approximately A$1.2M. 

Conclusion 

Based on local daily precision checks and half yearly 

rotation of sensors, together with yearly re-calibration of the 

sensors, i t is expeeted that the planned network will yield the 

data with uncertainty of 2 to 3% and 5% for short wave and long 

wave components respectively. Labour intensive and highly 

subjective quality control will be replaeed by automated and 

objective procedures which will reduce workload requirements for 

the quality control, data archival, retrieval and dissemination. 

Effective feedback to the network management centre will reduce 

the data loss to a minimum. 

Despite the promise of significant improvement in the solar 

radiation data yielded by the planned network, the network reequipment 

plan effectively reduces the number of solar radiation 

monitoring sites. This will affect some users requiring data with 

higher spatial resoiution. Currently the Bureau is evaluating a 

program of retrieval of daily surface global radiant exposure 

from satellite measurements. When operational the program should 

provide daily global radiant exposure data for a variable grid 

displacement of between. 6 and 24 km, with an uncertainty 

estimated at or better than 7% under clear sky eonditions and 

approximately 3 to 5 MJm-* under cloudy skies. The high quality 

surface observations will serve as ground truth and quality 

control indicators for the satellite-derived data. The program is 

expeeted to be fully operational during 1991. 

51


52 

-10OS- 

-400S- 

LSAHMONTH 

GERALDTON 

BROOME 

KALGOORLJE 

120°E tMACQUARiE !S. 

A!RNS 

ALICE SPR!NGS 

CHARLEVtLLE 

MT GAMBtER 

High Quality research stations 

WAGGA 

WAGGA 

LAVE3TON 

4-CAPE GR!M 

1ECOE 

WtLLJS tS. 

*ROCKHAMPTGN 

t'MLL!AMTOWN 

(multiple radiation quantities includin? spectral measureaents) 

High quality basic networi stations 

(measuring global, diffuse, direct and Ions wave radiation and 

sunshine duration) 

Publie information or partially capital iunded externally 

(measuring global and diffuse radiation)< 

Figure l 

Aüstralian solar radiation monitoring network.

ABSTRACT 


SOLAR RADIATION RESEARCH LABORATORY AT SERI 

T. Stoffe! 

So!ar Energy Research Institute 

1617 Co!e B!vd. 

Golden, Colorado 80401 

U.S.A. 

The Solar Radiation Research Laboratory (SRRL) was established in 1983 by the Solar 

Energy Research Institute (SERI) to collect high-quality solar radiation and surface meteorologica! 

data in support of SERI's research mission. The SRRL is located in Golden, Colorado, on South 

Table Mountain. In addition to continuously monitoring so!af radiation resources, the SRRL 

providcs an outdoor radiometer caübration faciüty, capabHities for instrumentation deve!opment and 

testing, and the data acquisition Systems ahd mounting p!atforms necded for research in solar energy 

conversion technölogies. 

1. RESEARCH DATA BASE 

The SRRL Baseüne Monitoring System (BMS) collects observations of the 17 so!ar radiation 

and meteorologica! parameters listed in Table 1. The battery-powered data acquisition system is 

programmed to sample the data Channels at 10-second intervais; it stores five-minute äverages of al! 

but wind-speed and wind-direction data, which are instantaneous samples. Data are stored on 

audiocassette tape for up to 14 days. The tapes are read onto disk files and are processed for quaiity 

control, reporting, and archiyal in SERI Standard broadband format (SERI, 1988). Routine 

maintenance of the BMS is performed daüy, except on Weekends and hoiidays. The condition of the 

equipment, adjustments to the System, and a simple weather Observation are recorded on a Standard 

!og form (Figure 1). Figure 2 is a sample monthly report of two-axis-tracking g!oba! so!ar irradiance. 

Simüar products are avaüable for the remaining data Channels. 

2. RADIOMETER CALIBRATIONS 

We have deveioped a Standard procedure for Broadband Outdoor Radiometer CALibrations 

(BORCAL) performed at SRRL. More than 200 radiometer caHbrations have been made as of 

December 1990. The procedure is based on direct comparisons with an abso!ute cavity radiometer 

for pyrheliometers and the Component Summation Technique (ASTM, 1986; Myers, 1989) for 

pyranometers. 

Pyrheliometers are caübrated by comparing the voltage signa! from the instrument under test 

with the dircct-normal solar irradiance as measured with ah electricaüy se!f-ca!ibrating absolute cavity 

radiometer traceable to the World Radiometric Reference (WRR). TypicaUy, the average of more 

53


than 500 such comparisons, made over at least two däys, is used tö determine the mean calibration 

factor (in microvolts/watt/square meter). 

Pyknometers are calibrated by summing measurements of the direct-hormal sola r eomponent 

as measured with an absolute cavity radiometer and the diflüse-horizontal (sky) solar irradiance as 

measured with a thermopile-based pyranometer mounted under an automatic solar tracking disk. The 

reference solar irradiance is calculated from the sum of these two components, incorporating the 

effect of the solar zenith angle at the time of measurement. The reference irradiance is then compared 

with the voltage signal from each pyranometer under test to determine the calibration factor. 

The final reporting method allows the instrument owner to easily interpret the calibration 

process and results. A sample of the instrument calibration factor variations with solar zenith angle 

is shown in Figure 3. 

3. RESEARCH SUPPORT 

The SRRL facilities have been used to evaluate the Performance of prototype automatic solar 

trackers for the U.S. solar monitoring network. Spectral solar irradiance measurements, in 

conjunetion with the Baseline Monitoring System (BMS) data, are used to evaluate the Performance 

of photovoitaic cells and submodules under natural outdoor eonditions. The devclopment and 

evaluation of SERI's Atmospheric Optical Calibration System (AOCS) has also been aecomplished 

at the SRRL. The AOCS provides Photometrie data for estimating the spectral distribution of solar 

irradiance needed för photovoitaic device testing. Building thermal Performance methods have 

benefitted from the measurements of solar irradiance on verticai surfäces oriented north, east, south, 

and west. Recently, the monitoring of direct-normal ultraviolet solar irradiance has been added to 

the SRRL BMS in support of a research project on solar detoxification of hazardous wastes. 

4. REFERENCES 

ASTM, 1986: .SYaH&zra' MÂo^/br Ca/^mô^t o/Pyra?:owiefefY ü^mg r/:^ -S'MW Dfrgc/ 

o/ta* D^/tMc Compo/teAt/y o/ Jo/ar /rraa'ifahcg. Ständard E913-R2, Committee E-44, 

American Society for Testing and Materials. 

Myers, D.R., 1989: "Application of a Standard Method of Uncertainty Analysis to Solar Radiometer 

Calibrations." Proceg^Mgy o/;/:e 796^9 Co/^re/!cg o/f/^v4manca/: 5*o/ar E;i

IPC VII Part 3: Contributions tö Symposium 

Table 1. Data Channels Cor the SRRL Baseline Monitoring System 

Channei 

No. Measurement Parameter Instrument* 

1 Global Horizontal Irradiance PSP 

Diffuse Horizontal Irradiance PSP 

Direct Normal Irradiance NIP 

Global Irradiance on a 40° South-Facing Till PSP 

Global Normal Irradiance on a Two-Axis Tracking Surface PSP 

Global Irradiance on a One-Axis Tracking Surface 

(Horizontal, North-South Axis) 

CM-11 

Global Horizontal Irradiance (780-3000 nm) PSP 

Direct Normal Irradiance (780-3000 nm) NIP 

Total Horizontal Ultraviolet Irradiance (295^385 nm) TUVR 

10 Ground-Reflected Radiation PSP 

11 Direct Normal Irradiance (500 nm) LCSP 

12 Wind Speed, 10 m above ground level TGT 

13 Wind Direetiön, 10 m above ground level TGT 

14 Dry Bulb Temperature CSI 

15 Relative Humidity CSI 

16 Barometric Pressure YSI 

17 Direct Normal Ultraviolet Irradiance (295-385 nm) TUVR 

*CM-11 = Kipp & Zonen Pyranometer, Model CM-11 

CSI = Campbell Scientific, Inc., Model 207 Probe 

LSCP = SERI-Designed Lpw-Cost Sun Photometer (T. Cännon) 

NIP = Eppley Laboratory Pyrheliometer, Model NIP 

PSP == Eppley Laboratory Pyranometer, Model PSP 

TGT = Teledyne-Geotech Wind System 

TLT/R = Eppley Laboratory Photometer, Model TUVR 

YSI = Yellow Springs Instrument Company 

55


SRRL MAINTENANCE AND OPERATIONS LOG (Vol. 25) 

Observer: ToM Day: MT@)TF Date: ^./24/^ DOY: Time: ö4 : SZ(MST) 

(circle) Solar Declination (ö): - o.??^ 

CR-21X 

Channel 

—RADIOMETERS/SENSORS— 

Measured 

Parameter 

1 GLOBAL HORIZONTAL WG7 

2 DIFFUSE (SB) 

3 DIRECT NORMAL WG7 

,4 GLOBAL 40-SOUTH 

5 2-AXIS GLOBAL 

6 1-AXIS GLOBAL 

7 GLOBAL HORIZONTAL RG780 

8 DIRECT NORMAL RG780 

9 TOTAL UV PHOTOMETER 

10 ALBEDO 

11 PHOTOMETER (500 NM) 

12 WIND SPEED 

13 WIND DIRECTION 

14 DRY BULB TEMPERATURE 

15 RELATIVE HUMIDITY 

16 PRESSURE 

17 UV DIRECT-NORMAL 

Condition 

Code* 

—DATA ACQUISITION SYSTEM (CR21X)— 

Clock (Reset at 

(slow/fast by 

—SURFACE WEATHER OBSERVATION— 

Temperature: Current _S]8_F Max 8^ F 

Cloud Cover: Total ^/p Type(s) 

MST) 

Reading 

(OT_:OOMST) 

//Ö 

^1 

-SUPPORT EQUIPMENT- 

W/m' 

W/m?. 

W/m'. 

W/m' 

4St W/m'. 

4/34 W/m'. 

44 W/m' 

w/m'. 

W/m' 

-Wl

STATION! 

SOOR 

1 

' DAY 

1 

2 

3 

4 

' 5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

1,9 

20 

2:1 

22 

23 

24 

25 

2 6 

2 7 

28 

29 

30 

AVS 

S D 

S/A 

MIN 

MAX 

Monthly Summary Prepared By The Solar Energy Research Inatitute 

SRRL 16-CBANNEL BASELINE MONITORING June 198 9 

3 9.74 N Latitude 105.18 tf Longitude 1829. Meters AMSL Time Zone -7.0 

SLOBAL SOLAR RADIATION ON A 2-AXIS TRACKIKS SURFACE 

HOURLY INtESRATED AND DAILY TOTALS 

WATT-HOURS PER SQUARE METER 

8 9 10 11 12 13 14 15 16 17 18 19 21 23 24 DAILY 

-[- 

2 6 3.8 7 

!- 

I 

866 990 

— - ! 

96 6 

-!- -I.- 

671 613 

-1 - 

8 91 82 3 

- I - 

124 

-!- -! - 

468 4 37 361 

- I - 

264 

-!- 

308 7 

-1 

8201 

4,0- 3f28 677 960 1035 977 600 3 93 66 4 4 05 393 1019 931 7 4 26 1. 

6525 

0 8 40 149 632 7 40 7 97 210 201 172 2 4 10 7 2 4 

1' 16 43 58 139 144 157 160 18:7 86 155 53 58 39 

69 6,1"7 882 987 1039 10 6 3 10 80 108 4 952 1071 354 62 9 927 549 

23 152 8 32 876 881 1033 225 43 807 1105 227 205 124 77 

81 2 34 44 8 17 8 815 240 876 1201 1020 1021 1073 841 257 

10 2 36 222 911 90 6 10 69 1133 3 34 371 64 79 655 2 38' 540 

1 31 66 18 2 37 6 4 63 502 467 654 613 254 738 2 57 12 9 

4 4 577 871 953 1031 100 6 7 77- 175 219 477 669 276 1,74 19 4 

4 34 69 3F81 514 6 95 8 52 774 48 7 542 815 876 3 61 .122 

4:4 192 713 881 605 482

IPC Vn Part 3: Contributions to Symposium 

WMO SUNSHINE DURATION MEASUREMENT COMPARISON 

1988/89 IN HAMBURG 

Dehne, K., Bergholter, U. 


Meteorologisches Observatorium Hamburg 

1. INTRODUCTION 

The definition of the quantity "sunshine duration" recommended at CIMO-VIII (1981) as the 

sum of time intervais during which the direct (normal) solar irradiance exceeds the threshold 

of 120 Wm i has stimulated the development of automatic measurement methods. The WMO 

comparison described here was performed according to the terms of reference of the 

Working Group on Radiation and Atmospheric Turbidity Measurement (see Resol. 10 of 

CIMO IX) "in order to establish and maintain comparability of sunshine duration data 

throughout the world." 

This paper containing some preliminary results is a modified Version of a presentation at 

TECIMO IV (1). The final report on the comparison will be pubtished by WMO in 1991 as 

"Instruments and Observing Methods" report. 

2. PARTICIPATING INSTRUMENTS 

Totally 9 member countries participated in the comparison with 11 optoelectronicsensors, 4 

pyranometer combinations with shade devices ("GD"-methods) and 2 Campbell-Stokes 

sunshine recorders. In Table 1 opto-electronic sensors scanning periodically the sky 

irradiance of more or less narrow sectors are compiled in group A. The MS-91 is the only 

one using a "black receiver" (pyroelectric detector). The sensors in group B apply Silicon 

cell arrays to evaluate the contrast, which is amplified in the case of the model SOLAR by 

a rotating shade bow. To specify the "GD"-methods, Table 2 contains information about the 

pyranometers and shade rings used (incl. corrections) as well as the applied threshold 

formulae. Iii the case of method GD (GDR) threshold formula and ring corrections are 

approximated by simply calculable terms being derived from measurement values. 

Tab. 1 

group number model manufacturer owner conntry 

(abbr;) 

HeHogr. ä Fibre Optique HFO C1MEL 

MS -91 EKO 

SONIe 6.008 SIGGELKOW FRG, NL, SF 

SOLAR HIB HAENNI CH, FRG, NL 

DB - SS9 Stove. Hydr. Inst. CSSR 

B NG - Al AES (Canada) CDN 

The 2 participating Campbell-Stokes recorders were models as used in French or German 

networks equipped with "blue" or "black" cards, respectively. 

59


Por deriving the reference values 2 Eppley Normal Incidence Pyrheliometers (NIP) of the 

Regional Radiation Center Hamburg were used. 

Tab. 2 

pyranom. modets shade device shade ring 

correction 

G 

PRM2 PRM2 ring: r—200; 

b=40 mm 

CM!1 CM11 ring: r=310; 

b =35 mm 

CM 11 CMH ring: r=296; 

b=50 mm 

CM 11 CM 11 disk: r=600? 

0=60 mm 

monthly 

factors 

"isotropie 

sky" 

threshold form owaer 

country 

G-D > 20 + D/10 GDR 

G-D > 120 sin? NL 

formüla 4 (3) G-D > 120 sin? FRG 

G-D > 120 sin? FRG 

(?: soiar eiev. angle) 

3. SITE AND DURATION 

The comparison was accomplished at the Meteorological Observatory Hamburg (53°39'N; 

10°07'E, h = 49 m) of the German Weather Service which is RRC in WMO-RA VI. The 

main period of the comparison was the 8 months interval from August 1988 to Mar ch 1989. 

4. DATA ACQUISITION AND REFERENCE 

The data acquisition system consisted of a Commodore 8032 Computer system, two scanning 

digital multimeters PREMA 5000, and a special digital input interface. Digital sensors were 

read out at 50 samples per second, 13 analogue Signals were scanned within 12 seconds 

every 20 seconds, Hourly results were printed änd stored on disc referring to TST, nameiy: 

- sunshine duration for each method, 

- sunshine duration for 41 fictitious thresholds from 80 to 240 Wm^, in steps of 4 Wm'\ 

- the sums of energy of all analogue values. 

Reference sunshine duration (S^f) was determined according to WMO definition, using the 

average of 5 Signals from the two NIPs for each set of scanned data. 

5. SUNSHINE AND WEATHER CONDITIONS 

Düring 6 months the monthly sums of sunshine hours were lower than the climatological 

means. The relative monthly sunshine duration S,,, (S^f related to the astronomical possible 

monthly sum) fluctuated between 35% (August) and 15% (December). The total number of 

threshold transitions N amounted to more than 7000, with high contributions of September 

and February, Winterly temperatures were extremely mild (only one Short snow episode in 

November). The precipitation was 440 mm corresponding to 90% of the climatological 

mean. 

6. PRELIMINARY RESULTS 

6.1 General 

The main groups of evaiuated results are: 

a) the absolute and relative deviations of hourly and daily 

S-values from the corresponding reference values. 

60


b) as a) but for data sets discriminated in groups A, B, and C 

according to the daily value of relative sunshine duration 

S^ < 0.3; 0.3 < S^


days with iarge Clusters of clouds (150), days with scattered clouds (40), and days with "fine 

weather" (20), respectively. For most of the methods the dots for (B) and (C) are relatively 

close to each other while the (A)-dots can be found somewhat separated at the side of higher 

deviations, This may be explained by the high probability tb meet fields of bright altus and 

cirrus clouds in group (A). The Standard deviations (in hours) describe the scattering of the 

absolute daily deviations öf the unseleeted data set and are typically high for the CSdeviations, 

The MEIT-values (in Wm'^) are calculated from the monthly values weighted by 

the proper number of evaiuated hours, at least for some methods these values should be 

considered as very preliminary. 

10- 

APR - 

), AUG ] SEP t OCT ) NOV ) OEC ) JAN I FEB ) MAR ) 

--A 

GD (FRG -O) 

CO (GOR) 

GD NL) 

^! GO (FRG) 

t AUG I SEP I OCT ) NOV I OEC. I JAN I FEB I MAR j 

10-, HFO (F-t) 

I AUG I SEP I OCT I NOV ! DEC I JAN I F$6__1_MAR ] 

10-, . 

A- ^Â?^. 

.— 

^ 

\ 

\ 

-10-] .* ^ s 

-\ \ 

-20- 

-10 

! AUG I SEP I OCt I NOV ] OEC I JAN t FEB I MAR ) 

I. AUG I. SLP I 0C1 I NOV I OEC I JAN ! FEB I MAR 

APR 

HFO (F^2) 

SONt (NL) 

SON! tSF) 

SONI (FRG) 

A- 

o— 

A- 

o- 

SOLAR (NL) A- 

SOLAR (FRG) *>- 

/! SOLAR (CH) o-— 

- MS-91 (J) + 

DB-SS!) (CSSR) 

NG-Al (CDN) 

CS (F-l) 

CS (F-2) 

CS (FRG-1) 

CS (FRG-2) 

CS (FRG-3! 

+— + 

Fig. 1: Percent dtviations of the monthly sums for al! participating methods. (Repiacement of SOLAR (CH) in 

October and HFO (F-l) in December.) , 

62 

A- 

-o 

+

W/m 

)20 

160- 

120- 

200^ 

160- 

120- 

t AUG ) SEP ) OC! ) NOV ) DEC ) JAN t H B ) MAR ] 

+ ^- 

.-A 

— + 

AUG [ SEP I OCT ) NOV ) OEC ) JAN ! FEB I MAR ) 

) AUG ) SEP ] OCT I NOV I DEC t JAN ] FEB ) MAR ) 

^— — o 

A A..^^ 

y 

Ah 

Y 

-A* ^ IT* 

^— — + 

'A- 


4 

00 (FRGÔ) A— A 

GD (GOR) ° ;—o 

CO tNL) 

CD FRG 

HFO (F-l) 

HFO F-2) 

- SON! (NL) 

SON} tSF) 

SON! (FRG) 

^ + 

- SOLAR (NL) Ar^r-.-rA 

SOLAR (FRG) "— " 

SOLAR (CH) n - — a 

MS-91 (J) 

08-SS9 (CSSR) '—- -* 

NG-Al (CON) Y —

IPC VlI Part 3: Contributions to Symposium 

40- 

30 

20- 

10-- "-A- 

-10 

20 

-30-* 

SO A 

WEIT 

— O ZU, ^ CE O o 

Li.CE 

t/1 LL CCCC 

zzz 

ooo 

oo 

1 1 

-toce oi 

ZOU. ü- 

OOO O 

YYY 

A A 

-0.8 

-0.6 

-0.4 

0.2 

-60 

-90 

120 

Y Y -150 

^ f^< (7! 

. ' ' o-oro: 

IPC VU Part 3: Contributions to Symposium 

SOLAR AND CRYOGENIC RADIOMETRIC SCALES : 

A PRELIMINARY COMPARISON 

J. Romero', N.P. Fox^ and C. Fröhlich* 

' Physikalisch-Meteorologisches Observatorium Davos, World 

Radiation Center, 7260 Davos-Dorf, Switzerland 

^ National Physical Laboratory, Division of Quantum Metrology, Teddington, UK 

This is an abstract of a paper presented at the Conference "New Developments and Applications in Optical 

Radiometry III" held in September 20-22 at Davos, which will appear in Metrologia. 

Established in 1975 for solar radiometry purposes, see Fröhlich (1978), the World Radiometrie Reference 

(WRR) is maintäined by a group of seven instruments - nameiy PACRAD III, PMO-2, PMO-5, CROM 

OL, CROM-3L, TMI-67814, HFQ4915 constituting the World Standard Group (WSG) - working at 

ambient temperature and pressure. These instruments are optimized for irradiances up to 1500 Wm^ and 

the estimated absolute uncertainty of the WRR is 0.3%. Cryogenic electrical Substitution radiometers 

working at radiative power levels in the 1 mW ränge have ah absolute uncertainty of few parts in 10^, 

which allbws to realise the radiative SI "scale" very accurately, see eg. Quinn and Martin (1985). We 

have performed a comparison with the Primary Standard Radiometer (PSR) of NPL, a cryogenic 

radiometer, and the lully characterized PM06-9 radiometer working at room temperature and pressure 

which is traceable to the WRR. The former has an absolute accuracy of ±0.001% measunng alaser beam 

and the latter of ±0.17% for solar irradiance, both at the 3o* level. 

This preliminary comparison was performed using a chain of transfer with Silicon trap detectors as 

described by Fox and Martin (1990) which arc well suited for that purpose and another room temperature 

radiometer. Measurements of a power-stabilized laser source at different wavelengths and power levels 

by both type of radiometers show a reproducibility of better than 0.02%. The comparison gives 

PSR/PM06-9=1.00145 which is within the stated absolute uncertainty of the radiometers, butis very closc 

to the limit of the 3c uncertainty of PM06-9. The ratio of PSR to WRR is 0.99869, and as a correction 

for diltracüon of about 0,1 % is not included in the WRR, the Anal ratio is very closc to 1 (0.99969). 

Notwithstanding, for solar radiometry fröm ground, a cryogenic radiometer can not be used without a 

window, thus it can not measure with its high accuracy solar radiation. thus, för the immediate future, 

the conventiona! room temperature radiometers as those of the WSG have to be used for that purpose as 

well äs the WRR. In future, plans exist to use cryogenic radiometers för solar radiometry fröm Space. 

Brusa, R.W., and C. Fröhlich, 1986: Appl. Optics, 25, 4173-80 

Fox, N., and J. Martin, 1990: Appl. Optics, 29, 4686-95 

Fröhlich, C, 1978: Final Report, WMO No. 490, 108-112 

Romero, J., N-P- Fox and C. Fröhlich, 1991: to appear in Metrologia 

Quinn, T.J., and J. Martin, 1985: Phil. Trans. Roy. Soc. (London), A316, 85-189 

65


EXPERIENCE WITH A RADIOMETER CAVITY IN SPACE 

J. R. Hickey and R. G, Frieden 

The Eppley Laboratory Inc. 

Newport, RI 02840, USA 

D. J. Brinker 

NASA Lewis Research Center 

Cleveland Ohio 44135, USA 

This is an updated summary of the paper delivered at the 

Optical Radiometry I I I Symposium, Hickey et. al. (1990). 

An H-F type cavity radiometer was included as the total i r 

radiance monitor of the Advanced Photovoitaic Experiment (APEX) 

aboard the Long Duration Exposure Facility (LDEF) satellite. This 

is the same type cavity which has returned data from Nimbus 7 for 

almost 12 years. The LDEF satellite was placed into orbit by the 

Space Shuttle Challenger on April 7, 1984 and Was retrieved by 

the Shuttle Columbia on January 12, 1990* The exposure of the experiments 

was för a period of almost 6 years although a mission 

of only one year had been intended. The APEX cavity radiometer 

was the total irradiance reference for a Iarge number of photovoitaic 

cells which were being tested. The APEX was pn the leading 

edge surface of the LDEF Which experienced the füll effects 

of the ram, including atomic oxygen flux and impacts by debris 

and micrometeorites. Examination has shown a minimum of visual 

ef fects caused by contamination. A change in the structure of the 

cavity paint is seen under microscopic examination at high I l l u 

mination. The Chemglaze Z3Ö2 paint appears to have deveioped 

ridges or "puckering" on the interior surface. The electrical 

properties, including heater resistance and thermopile resistance 

show nö change. For intercomparison in direct sunlight the APEX 

cavity Was mounted in a case of the type used for ground intercomparisons 

with an outer tube and a normal FOV tube replacing 

the flight tube. Initial irradiance intercomparisons at Newport 

showed agfeement with the local reference instrument, HF serial 

number 14915, at the ±0,1% level with uncertainty at this same 

level. Selected initial results at IPC VII show agreement at the 

-0.05% level with ±0.07% uncertainty. Final results with regard 

to the WRR for 14915 and the LDEF cavity await the IPC report. 

During the IPC the LDEF cavity reflectance was measured at PMOD. 

The reflectance appeared to be unchanged within the measurement 

uncertainty of about i80 ppm. 

The stability of seif calibrating cavity radiometers during 

long space misslohs is critical to our knowledge of true variations 

of the solar output at


IEA COMPARISON OP LONG-WAVE RADIOMETERS 

IN Hamburg. 1989/90. 

K. Dehne, U. Bergholter 


Meteorologisches Observatorium Hamburg 

D-2000 Hamburg 65 

F.R. Germany 

IPC VII Pari 3: Contributions to Symposium 

For measurement of the hemispherical long-wave irradiance (wavelengths 

3um) two methods are applied in meteoroiogy: 

- the determination of the difference between the total hemispherical 

irradiance (0,3um tö > 50um) measured by a pyrradiometer and the 

hemispherical solar irradiance (0,3um to 3(im) measured by a pyranometer. 

- the direct measurement by a pyrqeometer. 

The disadvantage of the former (and older) method is the use of two radiometers 

(and three calibration factors, see eq.(l), and some practical probiems 

With the Polyethylene dorne used mostly in pyrradiometry. The main probiem 

of the pyrgeometer is the non-ideal transmittance of the Silicon dorne which 

is covered by a cutôff interference filter to define the wäveiength border 

at about 3um (1). 

No precision Instrument is up to now available as ä reference. 

The differences between atmospheric heat radiation (A) determined at 

different meteorological institutes are usually within + 10 X. They can be 

explained by different types of field radiometers, different calibration 

procedures, different Ventilation Systems and last not least by different 

calculation procedures for the determination of A. 

The objectives of the long-wave measurement procedure comparison within 

IEA-Subtask 9F were 

- to find out the state-of-the-art of the international^ used procedures, 

expecially the level of measurement uncertainty in dependence on meteorological 

eonditions, 

- to find out the level of agreement between calibration factors derived 

in different Institutes, 

- to recommend procedural improvements for reducing the measurement Uncertainty 

with the special aim to establish a reference, 

- to recommend measurement procedures which are especially suited for solar 

collector test applications. 

2. PARTICIPATING RADIOMETERS 

Totally 6 IEA member countries have partieipated in the comparison with 6 

pyrgeometers and 2 pyrradiometers. 

Six of the pyrgeometers are Eppley radiometers of the type (PIR): one of 

them is modified by J.S. Foot (Meteorol. Research Flight, Farnborough) and 

has a special thermopile to reduce the influence of the internal temperature 

gradients on the measuring Signal (2). Only the PIR instruments of SMHI and 

NASA are equipped with a YSI-thermistor bead for monitoring the dorne 

temperature near its rim. 

The pyrradiometer of the Middleton-type, CN-1, is a radiation balancemeter 

67


with the downward lookirtg receiver surface covered by a metallic cap. The 

temperature of the cap is measured and introduced in the evaluation formula 

for Tg. The thin Polyethylene dorne protecting the upward looking receiver 

surface has to be blown up by dry compressed air. The "Schulze"-pyrradiometer 

manufactured by Dr. B. Lange, Berlin, is represented by the upper sensor 

of the homonymous radiation balancemeter.The temperature of the radiometer 

body (Tp) is measured by a platinum thermometer. For both pyrradiometers 

the mentioned CMll-pyranometer delivers the global radiation Signal needed 

for the evaluation. 

All Ventilation Systems are flanged to the side of the pyrgeometers with 

the exception of the NARC-device, the Ventilator of which is placed at the 

bottom of the pyrgeometer. In case of the MOH-radiometers the air is blown 

first into the body casing and streams out to the dorne afterwards, as for 

the NARC-device. The PIRof NASA, the PIR-Foot and the CN-1 of AES are not 

ventilated. 

2.2 Site and duration 

The comparison was accomplished at the Meteorological Observatory Hamburg 

(53°39'N, 10°07'E, h = 49 m) of the German weather Service. The climate of 

Hamburg is maritime; that means moderate seasonal temperature variations, 

seldom calm eonditions and a strong variability of cloudiness. 

The radiometers were installed at the measuring field on the roof. The 

data acquisition system consisting of three microcomputer-controned 

10-channel scanning digital multimeters (PREMA type 5000 and 5001) was 

operated in a laboratory connected by cables of about 25 m length. The raw 

data (mV,K ) were measured at 1 reading per 3Ös and stored on disk at this 

resoiution of time. 

The comparison was started on 20 July, 1989, and finished on 17 April, 1990. 

The main period of the comparison was the interval of 8 months from August 

1989 to March 1990. 

3. PRELIMINARY RESULTS 

3.1 General 

The general formula to derive the atmospheric heat radiation A froni the 

radiometer Output V, the radiometer temperatures Tg and Tp (body and dorne), 

the radiometer responsivity R^ and Rg (long-wave and short-wave) and the 

global solar radiation G is A A 

A = V/R, +o-.Tg^ - c . G - k.o"(Tp -Tg^) (1) where 

c equals toi^/R. for pyrradiometers or, for pyrgeometers, to an correction 

factor (^0,1), and k is an estimated correction factor (


more or less dependlng ort a.m. eonditions. It is also expeeted that the 

results of noh-ventiläted radiometers deviate sömetimes from the other results 

because of dew or rime depositions on the dorne. 

3.2 Preliminary results 

In the following we present some examples of absolute and relative A-values 

determined by the mean of the owner's calibration factors as well as 

fictitious results generated by Variation of evaluation parameters. 

3.2.1 Daily courses of A 

Fig.l shows the measured half-hourly sums in J- cm * of a nearly cloudless 

day (29 March, 1990). Related to the types of measurement eonditions mentioned 

in clause 3.1, type I can be identified at early midnight, type III in the 

early morning and late evening (incl. "cloud peaks") and type IV during 

daylight hours (with the largest spread of the curves). Pyrradiometer No. 

2 shows in the morning a "dew peak", pyrgeometer No. 7 "solar peaks" because 

of smail Scratches of the dorne filter near its foot. 

Fig.2 shows the course of half-hourly sums on a foggy day, (12 December 

1989), with the smail spread at type II eonditions. 

J/cm^ (hotfhourty sums) 

70 

65 

60 

55 

50 

45 

29. Morch 1990 

3,3 

jb4 

Rodiometar 

Np. ): Pyrrodiom. MOH 

3. 3 No. 2: Pyrrqdtom. AES 

J 3 No. J; Pyrgeom. SMH) 

4 No. 4: Pyrgeom. NASA 

5 Nö. 5: Pyrgeom. AES 

^ Np. 6: Pyrgeom. MOH 

7 No. 7: Pyrgeom. EKO 

-8 No. 8: Pyrgeom: "Foot" 

40 I ) 12 15 18 21 24 

UTC ^ 

&n'vc(f MgayMrg/ng/!f va/H&K?/*6' /on^-wave radio/Kîfery. 

69


j/cnrf (hatfhourty sums) 

70 

65 

60 

55 

50 

45 

40 

12. Dec. 1989 

7 7-. 

7-7 7.. 

7 7 7-7 7 7 

.7-7 

Radiometer 

t- ! No. 1: Pyrrodiom. MOH 

g. r-2 Mo. 2: Pyrrodtom. AES " 

3 ^-3 3- Pyrgeom. SMH) 

4 No. 4: Pyrgeom. NASA 

5 No. 5: Pyrgeom. AES 

€ No. 6: Pyrgeom. MOH 

-7 No. 7: Pyrgeom. EkO 

^ No. 8: Pyrgeom. "Fbot" * 

7-77-?? 

7- 7 7 7 -7 7 

12 15 !8 21 UTC 24 

F


Fig.4 shows curves as in Fig.3, but derived for the sums of the four hours 

10 tö 14 UTC, ite. around UTC-npon. The spread of the curves is enlarged 

by a higher eontribution of type IV eonditions to the A ^ values. 

A (Ref.: Pyrgeom. SMHt)ß 

re< 

1.09 

1.06 

1.03 

1.00 

.97 

.94 

A 

91 

1.09 

1 ,06 

1.03 

1.00 

JUL 

t ) t t ! ) ! 

AUG SEP OCT 

i- - - -) No. ): Pyrrodiom. MOH 

? -- -2 No. 2: Pyrrodiom. AES 

No. 3: Pyrgeom. SMHI (obs ) 

j / c m ' 

No. 4: Pyrgeom. NASA 

No. 5: Pyrgeom. AES 

No. 6: Pyrgeom. MOH 

3500 

^7 

No^ 7: Pyrgeom. EKO 

8 No^ 8: Pyrgeom. "Foot 

- ^. ' 7 . ! 

' ' , \ /' 

) ) ) ! t ) ! ! i < t ) ! ! 

NOV DEC JAN FEB MAR APR 

Fig. 4; Ay Fig J, ÖM^


3.2.3 Dependence of the seasonal course of A^ on the Variation of factors 

in eq.(1). 

Fig.5a shows, for the PIR of NASA as an example, the influence of the 

löhg-wave responsivity on the seasonal course of the relative decadic means 

of hourly sums. The responsivity is variated from .-15 X to +15 X in steps 

of 5 X. In maximum a 5 X step corresponds to an 1 X Variation of the decadic 

means the effect is very smail in decades with dominant type I and II 

eonditions. Fig.5b shows the effect of a Variation of the factor k (see 

eq.(1)) to correct the imperfectness of the PIR dorne. The Variation of k 

from Ö to 6 produces a change of the decadic means of only about 3 X or less. 

A - 

1.09 -, 1 r ! — i 1 , 1 1—^ 1 1 

1.06 

1.03 

1.00 

.97 

.34 

JUL AUG SEP OCT NOV DEC JAN FEB MÄR APR 

Fig. 3b; As in 3a), DM: depency ön tAe correenon/acfor K as de/ined in eö.fi). TAe va^Mes are related M 

Âe mean o/a// radiometry. TAe cMrvey are marêd by /Ae corresponding va/Mgy o/KCO, 2, 4, 6j. 

K=4MMjed/pr/AeroM^neeva/Mafion. 

4. FINAL REMARKS 

For continuous all-weather Operation of long-wave radiometers now in use 

Ventilation of the dorne is strongly recommended. Further investigations are 

necessary to Standard!ze a reliable calibration procedure. Pyranometer dorne 

shading has been proven to eliminate interference from direct solar. The 

final report of this comparison will be published in fall 1991. 

REFERENCES 

(1) Fröhlich. C. & Lohdon, J. (1986): Revised Instruction Manual on Radiation 

,Instruments and Measurements MRCP Publ. Ser.-No.7, MMO/TD-No.149, Geneva 

(2) Foot, J,. (1986): A New Pyrgeometer, J. of Atm. Oc. Techh., 3, 363 ff. 

72


SUNPHOTOMETER CALIBRATION AND RESULTS 

Ch.Wehrli and CFröhlich 

Physikalisch-Meteorologisches Observatorium 

World Radiation Center 

CH-7260 Davos Dorf 

Switzerland 

This text is an extended abstract of a presentation given at "New Developments and 

Applicaüons in Optical Radiometry tn, Davos 1990". The füll text is to be published in 

Metrologia. 

THE SUNPHOTOMETER SPM05 

This sunphotometer has three independent Channels in a tubulär housing of 5cm 

diameter and a length of 30cm. The detectors consist of interference filters and EG&G ÜV215 

photodiodes, they have a field of view of 1.3 degrees. The filters have center wavelengths and 

bandwidths of 778/5nm, 5(X)/5nm and 368/12nm. The sensor head is stabilized at a 

temperature of about 40 degrees celcius. 

LAMP CALBBRÄTIONS 

The absolute sensitivity of SPM05 was determined by calibration with a 1kW FEL 

Standard lamp to an estimated absolute accuracy of 1.9% at 778nm, 2.3% at 500nm and 2.7% 

at 368nm. Figure 1 shows the relative change in sensitivity over ä period of 6 years. In 1987, 

after a sharp drop occurred in the blue Channel, the filters were cleaned and the calibration 

repeated. While the blue and green channei imcreased, the red Channel decreäsed slightly after 

cleaning. This decrease may be explained by a molecular contaminaüon on the filter acting 

äs an anti-reflection coating that was removed by cleaning. 

O 

C 


based on Neckel and Labs (1984) data with an accuracy of betief than 1%. On absolute scale, 

the results äre well within the combined accuracies of the reference spectrum and Standard 

lamp. 

The solar constant measured by ACRIM, decreäsed by 0.05% in the same period. Thus, the 

relative changes might be explained by solar variations, stronger in the blue as UV variations 

are known to be higher, negligible in the solar maximum at 500nm. But wäveiength 

dependant ageing of the Standard lamp and seatter in calibration may also explain these 

results. An instrumental stability of much better than 1% has to be achieved in order to detect 

solar spectral variations in the visible. Improved Silicon detectors and methods for absolute 

calibration are investigated för sunphotometry aiming at a traceability of a few tenths of a 

percent. 

no. 

c 

ro' 

10 — 

1984 ' 1985 '1986' 1987 ' 1988 ' 1989 ' 1990 

Fig.2 eömparison of sotar spectral irMdiance determined by SPM05 with Necke) and Labs (19S4) data. 

+ 778nm X50Qnm 0 368nm 

REFERENCES 

H.Necket, DJLabs 1984: The soiar radiation between 3300 and 1250%) A. Kyy., 90, 205-258 

74 

3>


SOME STATISTICAL ASPECTS RESULTS FROM THE FIRST REGIONAL AR-IV 

PYRHELIOMETRIC INTERCOMPARISON AT ENSENADA, MEXICO^. 

J. L. BRAVO, A. MUHLIA 

Institute de Geofisica, 

Universidad Naciönal Autönoma de Mexico. 

/ ' ' 

INTRODUCTION. 

The first Regional Pyrheliometer Comparison was organized at 

Ensenada, Mexico, on 20 tö 25 april, 1989. 

A total of 13 instruments from five AR-IV member states and 

Switzerland (World Radiation Center Davos) participated in these 

comparisons. 

In two days with good eonditions for observing (22 and 23 april) 22 

series of 12 measurements were obtained, from which 80 individual 

measurements were valid according to the adopted criterium. 

The intercomparison has been evaiuated in terms of ratios of 

irradiances measured by each instrument against a reference 

irradiance. The regional pyrheliometric reference group (RRG) was 

implemented by the following instruments: 

PM05 WRC Davos 

HF-18747 RRC Ontario 

MK VI-67502 RRC Boulder 

A-18587 RRC Mexico, D.F. 

The pyrheliometers förming the RRG were referenced each against the 

three others. 

SOME STATISTICAL ASPECTS OF RBSULTING RATIOS. 

Considering the ratios as random variables we can construet 

histogräms of frequencies for each instrument (frequency 

distribution funetions), classified into a convenient number of 

class values. 

It is well known that for this kind of random variables the 

expeeted histogräms are those that correspond to normäl frequency 

distribution funetions. 

For this feason i t is of great interest to test the obtained 

histogräms for normality. In such a way i t is possible to detect 

measurement errors, instrumental defects or other kinds of probiems. 

MThis resume is an extract from the complete technicai report 

published in spanish (1) 

73


To test normality on histogräms we use the skewness and kurtosis 

coefficients and the Anderson-Barling statistic (2). For these 

parameters 95% confidence intervais for normal distribution 

assumption are estimated. 

The advantage on using the Anderson-Darling statistic is ^hat, 

besides testing normality/ i t is possible to have information about 

the provenance of the sample from an unique normal distribution. 

Statistical results. 

The values for skewness, kurtosis and the Anderson-Darling 

coefficient are listed in table 2. Among these parameters are also 

the mean and Standard deviation of the ratios for each instrument. 

The values marked with asterisk (*) are those that are out of the 

95% confidence interval. 

Instrument Mean 

HF-18747 1 .00064 

MK-67502 1 .00074 

PM05 0 .99994 

Ä-18587 0 .99869 

MK-68020 1 .00116 

MK-67401 1 .00082 

MK-68018 1 .00212 

MK-67702 

HF-21182 

HF-14915 

NIP18938 

NIP23946 

SMHIÄ166 

1 .00255 

1 .00309 

1 .00110 

0 .94856 

0 .96188 

0 ,99730 

Stdev 

0.00149 

0.00105 

0.00194 

0.00137 

0.00081 

0.00100 

0.00070 

0.00086 

0.00099 

0.00127 

0.00492 

0.00818 

0.01195 

Skewness 

-1.526* 

0.742* 

0.240 

0.326 

0.011 

0.509 

0.136 

0.398 

-0.319 

-0.629* 

-0.521* 

0.383 

1.065* 

Kurtosis 

5.99* 

3. .24 

3. 15 

2 37 

2 04* 

3. .24 

4,11 

3.00 

3.37 

3.52 

2.14* 

2.48 

4.36* 

Anderson 

2.623* 

0.910* 

0.276 

0.557 

0.746 

489 

464 

399 

705 

0.699 

2.718* 

0.718 

1.379* 

In terms of this statistics we distinguish the following groups of 

instruments: 

i) Instruments without normality probiems: 

PM05 

A-18587 

MK VI-68020 

MK VI-67401 

MK VI-68018 

MK VI-67702 

HF 21182 

HF 14915 

NIP 23946E6 

WRC Davos 

RRC Mexico, DF 

MARIETTA Denver 

TMI California 

SERI Colorado 

JPL California 

FSEC Florida 

EPPLEY Newport 

MARNR Caracas 

i i ) Instrument with normality probiems: 

76 

(Marginally platykurtic) 

(With significant platykurtosis) 

(With significant negative skew) 

(With marked negative tendency) 

HF 18747 RRC AES Canada (Highly skew and leptokurtic 

and with significant high A-D 

stat. This permits Us to reject 

the hypothesis of unique normal 

distribution).


MK VI-67502 RRC Boulder (Highly skew and significant 

high A-D statistic) 

NIP18938E6 1MN Costa Rica (three statistics out of 95% 

confidence interval). 

SMHI A-166 IGORS Mexico, DF (same as the above). 

COMMENTS 

Some comments we can do on relevant cases, for example: in the case 

of the HF-18747 we See some points out of his general comportment, 

same is for MK VI-67502. In the case of the A-18587 i t is apparent 

some flathess form on this histogram is due to a not so good 

sensitivity. Another relevant cases are the NIP 18938E6 and A-166, 

we see in the histogram, of the first one of these, that there is 

a significant bimodality due probably to a discontinuity in his 

trend ratio, caused when the Operator clean the pirheliometer 

window. In the case of the A-166, the three statistics are out of 

the 95% confidence interval due to a general failure on his control 

box. Finally a special case is the NIP 23946E6 which has a 

significant negative tendency, may be düe to temperature dependency 

on his instrumental constant. 

ACKNOWLEOGEMENT. 

The authors are gratefülly acknowledged.to Christoph Wehrli from 

Physikalisch-Meteorologisches-Observatorium at Davos for his 

helpful support and his comments on portions of the manuscript that 

motivate us to publish this paper. 

REFERENCES. 

1. Mühlia, A., J.L. Bravo, M. Valdes, E. Jimenez de la Cuesta, J. 

Martinez y A. Mota. "Primera Intercomparacion Pirheliometrica 

Regional de la O.M.M., Region IV/ Mexico. Reporte Teenico.", 

Comunieaciones teenicas, Instituto de Geoflsica, Universidad 

Naciönal Autönoma de Mexico, Serie Datos Instrumentacion y 

Desarrollo, No. 34, 1990. 

2. DÂgostino, R.B. and Stephens, X.A. Editors: "Goodness of Fit 

Techniques"; MARCEL DEKKER, INC. New York and Basel, 1987. 

77

00 

16 

12 

0.995 

20 

f 15 

r 

e 

c 

*-< 10 

e 

n 

c 

a 5 

0.995 

HtSTOGRArB DE ERECUENGtQS 

^:: 

0.9974 0.9998 1.0022 

RAZON PW5 

HtSTOGRAWA Dt FREQUENCtAS 

0.997 0.999 1.001 

RAZOW H-f 18747 

1.0046 

1.003 1.005 

20

EXPERIENCE WITH CM-15 

J. Olivieri and S. Mevel 

Meteorologie nationale 

Centre radiometrique 

F-84200 Carpentras 

France 


The new Pyrradiometer CM-15 is made from a Pyranometer CM-11 

(Kipp & Zonen) the glass dornes of which are replaeed by a 

polythene one. The temperature of the cold junetions (or the case 

of the CM-15) is measured by a platinum resistance temperature 

detector. This radiometer was first calibrated using the same 

method as that used for pyranometer using the Sun and Sky as 

source with a removable disk for the pyrradiometer. The reference 

is a Standard pyrheliometer. 

The sensitivity K of the thermopile of the CM-15 is given by the 

well-known formula: 

K=(V1 - V2)/ I*sinh (1) 

where: 

.VI and V2 are the thermopile readings 

averaged over the exposed and shaded 

periods, 

. I is the direct normal irradiance, 

. h is the solar elevation. 

An electronic box is connected to the CM-15. Inside the 

thermopile output is measured and the detector flux is calculated 

from the resistance of the platinum sensor. The results of the 

Total irradiance measurements are calculated using the formula: 

E(4 ) = V/K + c

IPC VII Part 3: Contributions tp Symposium 

The results of the pyrgeometric measurements (IR irradiance from 

atmospheric origin) were calculated using the Albrecht and Cox 

formula: 

E(IR)=V^/K^+^.6".T^ - k.(T (T/ -Tj ) (3) 

where: 

. V^^ is the thermopile output (V), 

. Kp is the sensitivity of the thermopile, 

. od., is a coefficient the value of which is 

dose to 1, 

. k is a coefficient the value of which is 

close to 4, 

. Tt is the case temperature, 

. Tj is the dorne temperature, 

. o** is the Stefan-Boltzmann constant. 

Whether using or not using a tracking disk to shade the dorne from 

the Sun, the results of longwave measurements were very close 

although the temperatures T^. and Tj were different in these two 

cases. 

The following Tables and Graphs summarize the results of the 

comparison between the CM-15 and the "reference" that took place 

in July during hot days and nights with cloudless skies. 

The Tables and Graphs show that the ratios between the raw results 

of the CM-15 and the reference measurements are close to 1 at noon 

and that they reach 1.08 by night-time: see graph 1 Figure 1 : 

o< =0.98 ; K=4.94E-6 V/Wm*^. 

These "errors" are inadmissible; it seems that they are the 

consequence of: 

. a wrong value of coefficient e*< in formula (2), 

. the overheating of the dorne of the CM-15, 

. a wrong value of the sensitivity K of the thermopile, 

Some complementary attempts to correct these errors confirm these 

assumptions: see grapf 2 Figure 1 : c< and K are corrected: 

c< =0.93 ; K=4.82E-6 V/Wm"^(the former value of K is probably 

wrong). 

The comparison between the results of the CM-15 measurements and 

those of the "reference" will be going on with new measurements 

during cold days. We hope for good results with correct values 

of K and ^(see formula (2)) that we are going to strive. 

80

SUNRISE 

Local Apparent Time 

SUNSET 

FIGURE 1 : CM-15 / Reference Ratios 

Day : July 13, 1990 

Formula (2) was used for the CM-15 measurements : 

Graph i


82 

TIME 

00:30 

01:30 

02:30 

03:30 

04:30 

05:30 

06:30 

07:30 

08:30 

09:30 

10:30 

11:30 

12:30 

13:30 

14:30 

15:30 

16:30 

17:30 

18:30 

19:30 

20:30 

21:30 

22:30 

23:30 

IRRADIANCE Wer 2 

o< =0.98 

CHI 5 REF. 

344.67 

342.61 

339.81 

338.39 

349.69 

452.36 

613.17 

790.69 

959.28 

1095.17 

1203.33 

1261:06 

1268.33 

1218.22 

1125.86 

986.06 

821.11 

646.75 

488.36 

387.22 

370.47 

364.61 

357.50 

353.22 

322.19 

320.11 

317.64 

316.56 

326.17 

432.83 

594.75 

776.08 

949.03 

1088.97 

1199.36 

1253.64 

1257.83 

1204.58 

1109.58 

969.00 

798.89 

618.44 

456.56 

355.89 

343.61 

339.17 

333.69 

330.72 

RATIO 

(1) 

CHI5/REF 

1.070 

1.070 

1.070 

1.069 

1.072 

1.045 

1.031 

1.019 

1.011 

1.006 

1.003 

1.006 

1.008 

1.011 

1.015 

1.018 

1.028 

1.046 

1.070 

1.088 

1.078 

1.075 

1.071 

1.068 

TABLE 1 : CM15 / Reference Ratios 

CM15 : (1) 0.98 

(2)

APPENDIX : OVERHEATING OF PYRGEOMETER DOME 

AND PYRGEOMETRIC MEASUREMENTS . 


The overheathing of the Pyrgeometre dorne depends on the use or 

the non-use of the tracking disk that shades the dorne fröm the 

Sun. Figure 2 shows the overheating of the dome during hot days 

in July at Carpentras ( the meteorological temperatures reäched 

37 "C ). 

Using formula number (3) the results of the IR irradiance 

measurements made by the Pyrgeometer were very clöse in these two 

cases. Table 2 shows the results of 8 of 50 series of 

measurements. 

CD 

(0 

CO 

o 

! 

§ 

*3* 

93* 

* 3* 

Local Apparent Time 

++ 

+ + 

5K ^ $K 3K 

FIGURE 2 : Overheating of the Pyrgeometer dorne: 

* the tracking disk is used 

+ the tracking disk is not used. 

83


84 

RUN 

N° 

31 

34 

36 

38 

41 

44 

48 

50" 

TRACKING 

DISK 

YES/NO 

Y 

N 

Y 

Y 

N 

Y 

Y 

N 

Y 

Y 

N 

Y 

Y 

N 

Y 

Y 

N 

Y 

Y 

N 

Y 

Y 

N 

Y 

LOCAL 

APPARENT 

TIME 

05:30 

05:34 

05:38 

06:12 

06:16 

06:20 

13:30 

13:34 

13:38 

14:00 

14:04 

14:08 

14:42 

14:46 

14:50 

15:26 

15:30 

15:34 

17:06 

17:10 

17:14 

17:56 

18:00 

18:04 

The sky is becoming cloudy . 

IR 

IRRADIANCE 

Wm-s 

330.81 

329.97 

331.22 

332.70 

331.53 

333.57 

385.46 

387.55 

386.89 

386.03 

387.26 

387.57 

390.26 

389,52 

391.79 

388.25 

385.48 

388.85 

381.17 

377.79 

381.08 

382.89 

380.40 

381.11 

MIDTIME IRRADIANCE 

disk:yes disk:no 

331.02 

333.14 

386.18 

386.80 

391.04 

388.55 

381.13 

382.00 

329.97 

331.53 

387.55 

387.26 

389.52 

385.48 

377.79 

380,40 

TABLE 2 : Pyrgeometric measurements with / without 

the tracking disk on July 22, 1990. 

RATIO 

(*)./(**) 

1.0032 

1.0048 

0.99&5 

0,9988 

1.0039 

1.0080 

1.0088 

1.0042


IEA GLOBAL RADIATION REFERENCE RADIOMETER COMPARISON 

K. Dehne, Deutscher Wetterdienst, Meteorologisches Observatorium Hamburg, 

D-2000 Hamburg 65, F.R. Germany 

L. Liedquist, Statens Provningsanstalt, S-50115 Boras^ Sweden 

L. Dahlgren, Swedish Meteorological and Hydrological Institute 

S-60176 Norrköping, Sweden 

ABSTRACT 

It will be reported on a method to acquire global radiation reference data 

and on a comparison of corresponding reference radiometers. 


1.1 According to clause 9.4 of the WMO Guide (1) and to definitions in 

an ISO Standard (2) the solar radiation received from a solid angle of 

2T7*steradian on a horizontal plane is called global (solar) radiation. If 

the solar radiation has passed through the atmosphere the global radiation 

consists of the direct solar radiation (beam eomponent) and the diffuse 

solar radiation (scattered eomponent). Due to absorption in the atmospheric 

gases (first of all ozone and water vapour) its wäveiength ränge reaches 

nominally from 0,3 to 3 um. 

The direct measurement of global irradiance G requires the use of a 

pyranometer the speeifications of which meet the above mentioned 

characteristics. The indirect measurement is based on the fundamental 

relationship G = I cos ^+ D (eq. 1) 

where ^ : zenith angle of the sun 

I : direct solar irradiance 

D : diffuse solar irradiance 

and has to be realized by the pyrheliometric measurement of I (field-of-view 

anglet) and the simultaneous measurement of D using a pyranometer which 

is shaded from the solar beam by a disk (shaded field-of-view as Iarge 

as


86 

with uncertainties of about 5 % and 3 X, respectively. För aimihg the IX 

level it was recommended to use a combined radiometer system as mentioned 

in 1.2. 

An internal comparison of two combined global radiation reference Systems 

was established during the summer of 1985 at the Centre Radiometrique of 

the French Meteorologie Nationale in Carpentras (5). The system of the MARC 

of the AES in Canada used an Eppley Normal Incidence Pyrheliometer (NIP) 

and a shaded CM11 pyranometer; the french system consisted of the same 

components. The comparison of 6 min mean values measured during cloudless 

eonditions showed deviations in G within about 20 M-tn * which corresponds 

to about 2 X for high G-values. 

2. PURPOSE AND RATIONALE OF IEA GLOBAL RADIATION REFERENCE RADIOMETERS (GRRR) 

2.1 The Solar Heating and Cooling Program (SHCP) of the IEA (International 

Energy Agency) is mainly concerned in the working group of Subtask 9F with 

tests and improvements of radiometrie measurement procedures needed for 

solar energy applications. At the end of a longer period of investigations 

of pyranometer characteristics the following goals suggests the establishment 

of global radiation reference radiometers (GRRRs): 

r- Validation of the improvement of global radiation data by correction 

formulae derived from the characterizations of pyranometers. 

- Recommendation of high quality radiometers to achieve ä minimum 

uncertainty of global radiation data. 

- Proof of the achievement of the 1 X, rms uncertainty level of 

global radiation data. 

2.2 The rationale of the GRRR may be described by the following 

speeifications: 

a) The GRRR is a compact instrument system which uses one solar tracker 

to follow the sun with both, the pyrheliometer and the shade disk of 

the pyranometer. It works like one radiometer with two different 

radiometric sensors. Its portability and transportabelity by smail 

cars is desired for applications in different sites. 

b) The GRRR has to be equipped with radiometers of the highest quality. 

That means according to (2) that in the case of the pyrheliometer an 

absolute cavity radiometer is required which is labelled as a ISO Primary 

Standard, or at least, as a ISO Secondary Standard. The pyranometer has 

to be taken from the class of ISO Secondary Standards. 

c) For practical reasons the GRRR has to be operated-automatically, but 

not necessarily during precipitation events, 

For the purpose of solar eollector tests the weather eonditions can 

generally be restricted to fine weather exeluding the hours with solar 

elevations less than 20°. 

3. ON THE UNCERTAINTY OF GRRR DATA 

The uncertainty pf GRRR data can only be estimated from the deviations of 

corresponding data measured with different GRRR's and from an uncertainty 

analysis of the GRRR instrumentation and method. To the latter some important 

considerations are compiled in the following. 

3.1 The bäsic relationship of eq.(1) requires for an exact synthesis öf 

G that 

- the time constants of the pyrheliometer änd the pyranometer are equal,

IPC VII Pari 3: Contributions to Symposium 

- the optics of the pyrheliometer tube and the shade-disk-pyranometer 

geometry are equivalent so that the ämout of circumsolar radiation 

received by the pyrheliometer is obstructed by the disk, . 

- the effective spectral ranges of the pyrheliometer and the pyranometer 

are equal. 

If no instantaneous values but only hourly means, for instance, are required, 

or if the sky is cloudless, differences in the time response are acceptable. 

The shaded angle of the pyranometer can easily be fitted (by choice öf the 

disk radius r. and the distance D between the Centers of the disk and the 

receiver surface) to the field-of-view angle c< of the pyrheliometer. For 

smail -values this shaded angle is also well approximated for receiving 

points at the border of the surface if the sun is in the zenith. With 

increasing zenith angles the shade on the receiver is more and more 

elliptically shaped where the increasing long axis lies in the solar 

meridian. The field-of-view angles in the two border points on this axis 

deviate from


88 

formulae for temperature response and non-linearity. Considering these 

speeifications a percentage uncertainty level of 3 X (rms) is obtained. 

To approximate the spectral ränge of the pyrheliometer and to enlarge the 

UV- and IR-responsivity the pyranometer should be equipped with quärtz domes 

(OH -free quality). Due to the higher heat conduetivity of quartz also the 

offset effect of the pyranometer can be redueed^. For further reduction 

of the thermally generated offset the pyranometer domes should be ventilated 

(6). The remaining offset has to be approximately determined by covering 

the pyranometer domes by a zero cap. A carefully construeted zero cap should 

be able to shield the solar radiation with a minimum of disturbance of the 

air streams (natural and ventilated) and the IR fluxes. A prototype of such 

device is shown in Fig. 1. 

thin metä! sheet isoiätion-PVC 

^ i i - -VS. 

CM 11 

Fig.l: Improved prototype of a zero cap for pyranometer CM11 (schematic). 

Inner walls : black painted; outer walls : white painted; metal 

screen : shaded from direct solar radiation by disk. 

Assuming that the offset can be reduced to an irradiance equivalent of less 

than 3 M-m ^ (in the case of CM11 : Signals less than 15 uV) and that 

G = (I . cos 30° + D) is equal to 780 W.m ' + 100 M-nf') on a clear summer 

day the resulting uncertainty in G is 1.1 X (rms) if the uncertainty 

contributions of the beam and diffuse eomponent are added. 

4.ORGANIZATION OF THE IEA COMPARISON 

The comparison was hosted by the Swedish Meteorological and Hydrological 

Institute (SMHI) in Norrköping. The measurement Site was the roof platform 

of the radiation center of this institute. The owhers of the three participating 

GRRRs were the Swedish National Testing and Research Institute (SP) 

(in Cooperation with the host), the National Radiation Center of the 

Atmospheric Environment Service in Canada and the Meteorological Observatory 

Hamburg of the German Meather Service. 

The comparison was started in the middle of June 1990 with a long t?st phase 

for the Swedish and German GRRRs. The measurement phase runned through the 

August 1990 and began after the installation of the Canadian GRRR. 

-5. SHORT DESCRIPTI0NS 0F THE INSTRUMEMTS USED IN THE COMPARISON 

5.1 In all three GRRRs the pyrheliometers are of the Eppley H-F (Hiekey- 

Frieden) type; the hiStöry of the individual radiometers is of different 

length. The same applies for the pyranometers which all are instruments 

of the Kipp & Zonen CMTI-type selected first of all because of their low 

4) In combination with CMlI-^pyranometers: reduction of the thermal offset 

by a factor of 0.65.


cosine errors. All pyrheliometers were additionally equipped with an 

automatic shutter to computerize the calibration procedure. The Canadian 

pyrheliometer was not closed by a window, as the other two instruments. 

The pyranometers were ventilated by different blower devices. For measuring 

the zero offset of the pyranometers a zero cap prototype of the Met. 

Observatory Hamburg was used. 

The Canadian and Swedish GRRR were tracking the sun by the means of the 

commercial, fully automated. altazimuth COSMOS-tracker (see Fig. 2a). For 

the sun-following movement of the shade disk different mechanical Solutions 

are applied. 

The solar tracker of the German GRRR is an equatorial mount driven by a 

synchroneous motor and designed by the Met. Observatory Hamburg (see Fig. 

2b). The adjustment of the shade disk to follow the declination angle of 

the sun häs to be accomplished manuaily. This inconvenience and the larger 

work effort for the initial adjustment of the tracker should be balanced 

by the smail size and price of the mount. To stabilize the mount mechanically 

a counter weight is necessary to compensate for the weight of the cavity 

radiometer. 

poraHet 

eteva&m 

thift of 

thading dittt 

thade dtHt 

thaded pyranometer 

thutttr 

1 pyrhehometer 

Fig.2: Simplified sketchs of a) the Swedish GRRR, and b) the.German GRRR 

The Swedish data acquisition system has hosted also the German GRRR, Its 

main part is the Hewlett & Packard multimeter/scanner model! 3457. The used 

scahning time for 8 Channels is 2s; the data are taken every 6s. The Canadian 

data acquisition System has used the same type of multimeter/scanner. 

5.2 The GRRR data are supplemented by those of the routine measurement of 

the Station, for instance ambient air temperature and global radiation. 

Furthermore hourly synoptic observations of a nearby airport are available. 

A special set-up was the Operation of the fish-eye.video camera (model 

Panasonic + Nikkon) to obtain a documentation of the actual cloudiness. 

A complete picture of the sky with 256 x 256 elements was taken and stored 

every half hour. a reduced picture of 16 x 16 integrated elements was stored 

every 5 minutes. 

b 

IT 

89


90 

6. RULES OF OPERATION 

The following rules have determined the operational eonditions for the 

comparison: ' 

a) Selection of comparison hours: 

The core time of the comparison is restricted to hours of working days 

(generally during 6.00 and 14.00 UTC) with low cloud amount (m 4 octa) 

and no precipitation. Cloudless sky eonditions are preferred. 

b) Calibration of the H-F-pyrheliometers 

A calibration procedure has to be performed every hour between the 

minutes 0 and 9 (during the shading period) at about 700 W-m * 

and 950 W-m '. 

c) Zeroing of the pyranometers 

During the calibration of the pyrheliometers the pyranometers have 

to be covered for 5 to 10 minutes to determine the zero offset. 

d) Maintenance routine 

- Dismantling or covering of the H-F-pyrheliometer if rain is expeeted 

during the following hour. and at the end of a working day. 

- Observations of the weather eonditions at least every hour and control 

of the precise solar tracking every two hours. 

- Cleaning of Windows and domes of radiometers at least before starting 

the daily comparison. 

- Control of the data acquisition procedure every 2 hours. 

7. RESULTS 0F THE COMPARISON 

Final results of compared data are not yet available. The intention is to 

compare 10 min means. 

An important result is the operational experience gained in the test phase 

of the comparison. This concerns first of all'the handling of the German 

solar tracker, the calibration and zeroing procedures as well as the data 

taking routine. 

Due to the late delivery of quartz domes only traditional CMll pyranometers 

are used. Use of quartz domes and other improvements may be considered if 

another comparison in 1991 will be suggested by the final results. 

REFERENCES 

(1) WMO (1983): Guide to Meteorological Instruments and Methods of 

Observation (5 th edition) 

(2) ISO (1990): Solar Energy - Specification and Classification of 

instruments for measuring hemispherical solar and direct 

solar radiation. ISO-Standard 9060; ISO-Bureau, Geneva. 

(3) ISO (to be published): Solar Energy - Calibration of a field 

pyranometer using a reference pyrheliometer (ISO-DP 9846) 

(4) WMO (1986): Revised Instruction Manual on Radiation Instruments and 

Measurements, WRCP Publication Series No.7, WM0/TD-No.l49, Geneva. 

(5) Coudert, R.; Olivieri, J.; Wardle, D.I. (1988): 

Summary of the results of the 1985 NARC-SETIM Comparison of 

reference measurements of horizontal short-wave irradiance 

(Internal report) 

(6) ISO (1990): Solar Energy - Field pyranometers - recommended practice 

for use (Technical Report 9901), ISO-Bureau, Geneva.


ESTIMATION OF SPECTRAL RADIATION DISTRIBUTION 

FRÖM GLOBAL RADIATION 

D. Crommelynck and A. Joukoff 

Royal Meteoroiogicai Institute of Belgium 

B - 1180 Bruxelles 

Belgium 

On the basis of a füll year spectra! irradiance observations performed in Uccie at the 

Royal Meteorological Institute, a simple algorithrh is deriyed for the evaluation of the spectral 

distribution of the Solar radiation on a horizontal surface as a function of the total Solar 

irradiance (global radiation). 

The method, valid for indüstrial applications (agriculture, aging pf materials, etc .) is 

based on a triangulär fepresentätion of the spectrum between 300 arid 900 nm. 

The functions h and hz(X) which depend on the wäveiength X(nm) and on the global 

radiation G(Vm^), give respectively the ascending and descending straight lines of the triangle 

whose summit is taken at 465 nm. 

These functions (spectral densities of radiation, expressed as h(m ^nm"') are 

A,(X)= 1.163 10*s(x-300)& 

^2(\) = (3.1515 10^-2.651 10'^X)C 

These two functions can be used, for all sky eonditions, as a good first approximation of 

the global spectral radiation distribution as illustrated below. 

SOLM) SfECTKAL nHUUMMCE DENSITY 

Comparison o( the triangutar mode! to 

continuous observations (—) ana discrete observations 

(*) with ctear sky. 1 : Gtoba) radiation - 2 

; Direct radiation - 3 : Diffuse radiation. 

UttlFORM ÖVEHCMT SKY 

Compansoh of the triangulär mode) to 

continuous observations (—) and dtscrete observations 

(*) with uniform overcast sky. 

The details of the method can be found in our paper Mmp/e a/gwMm /or ?%e ^//wafroM 

o/ fAe êc/ra/ raavaf/ow a*^^!&Mfww ow a Aor/zow/a/ .SMr/ace, Aayea* ^/oM/ raa*/a^0M 

wea^M^wcn^" published in Solar Energy Vol. nr 3, pp 131-137, 1990. 

91

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