Fourth Study Conference on BALTEX Scala Cinema Gudhjem

Figure 2. Diurnal cycle of the sensible (H) and latent (LE)
heat fluxes over the major land use classes in the LITFASS
area on May 25, 2003.
LE in mm
Heat flux in W/m 2
10
9
8
7
6
5
4
3
2
1
0
500
400
300
200
100
0
00:00 06:00 12:00 18:00 00:00
-100
-200
21.05.03
23.05.03
25.05.03
27.05.03
29.05.03
31.05.03
02.06.03
UTC
04.06.03
Date
Figure 3. Daily sums of turbulent heat transport (H)
and evaporation (LE) from the major land use classes
in the LITFASS area during the LITFASS-2003
experiment
Taking into account the considerable differences in the
energy fluxes between the various land use types at local
scales, the question arises how these data can be aggregated
into area-representative flux values. Both, scintillometer
measurements along a path of 3 ... 10 km length and the
Helipod measurements along flight legs of 10 ... 15 km
length are assumed to provide a reasonable estimate of area
averaged fluxes. For the sensible heat flux, reasonable
agreement has been found between the scintillometer data
and an average from the surface measurements
characterising the surface types upwind of the scintillometer
paths (Figure 4). Also, the heat flux values derived from the
Helipod measurements along low-level flight legs fit well
into the picture obtained from the surface and scintillometer
data.
For the latent heat flux (Figure 5), larger differences have
been found between the different types of measurements.
Systematically higher latent heat fluxes have been derived
from the microwave scintillometer data when compared to
an average of the eddy covariance measurements, and quite
some scatter has to be noticed in the Helipod fluxes.
A comparison of sensible and latent heat fluxes derived from
Helipod measurements along flight legs over the major land
use types against surface measurements shows reasonable
agreement within the uncertainty of the derived fluxes
(Figure 6).
06.06.03
08.06.03
10.06.03
12.06.03
H (grassland)
H (forest)
H (Lake)
LE (grassland)
LE (forest)
LE (Lake)
14.06.03
16.06.03
18.06.03
-200
0
200
400
600
800
1000
1200
1400
1600
1800
- 38 -
H in J/cm 2
Sensible heat flux in W/m 2
500
400
300
200
100
-100
-200
Figure 4. Diurnal cycle of the sensible heat flux over the
mainly forested and mainly agricultural parts of the
LITFASS area as derived from local eddy-covariance,
LAS, and Helipod measurements on May 25, 2003.
Latent heat flux in W/m 2
0
00:00 06:00 12:00 18:00 00:00
500
400
300
200
100
0
00:00 06:00 12:00 18:00 00:00
-100
-200
Figure 5. Diurnal cycle of the latent heat flux over the
mainly forested and mainly agricultural parts of the
LITFASS area as derived from local eddy-covariance,
MWS, and Helipod measurements on May 25, 2003.
Heat flux at ground level [W/m 2 ]
350
300
250
200
150
100
50
0
-50
Figure 6. Comparison of locally measured surface fluxes
over the main land use classes in the LITFASS area
against Helipod measurements along flight legs above the
major land use types (catalogue flight) carried out on May
30, 2003.
UTC
UTC
-50 50 150 250 350
Heat flux Helipod [W/m 2 ]
Forest (in-situ)
Farmland (in-situ, mean)
Scintillometer (forest)
Scintillometer (farmland)
Helipod (forest)
Helipod (farmland)
Forest (in-situ)
Farmland (in-situ, mean)
Scintillometer (farmland)
Helipod (forest)
Helipod (farmland)
H (farmland)
H (lake)
H (forest)
LE (farmland)
LE (lake)
LE (forest)