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FOEHN IN THE RHINE VALLEY AS SEEN BY A WIND-PROFILER-RASS SYSTEM AND COMPARISON WITH THE NONHYDROSTATICMODEL MESO-NH.S. Vogt 1 , G. Jaubert 21Siegfried Vogt Institut fuer Meteorologie und Klimaforschung, Forschungszentrum76024 Karlsruhe, Germanysiegfried.vogt@imk.fzk.decorresponding author2Genevieve Jaubert Centre National de Recherches Meteorologiques31057 Toulouse, Francegenevieve.jaubert@meteo.fr1. IntroductionFoehn is the generic name for the strong and turbulent wind, which blows from the crests ofthe mountains towards the lee. This wind brings warm and dry air at the surface. Foehn eventsare quite common on the northern side of the Alps and represent very important phenomenafor the weather forecasting in the Alpine valleys, where a lot of people live.Different conceptual models have been proposed for the Foehn. However, the lack of data inmountainous regions limits the understanding and the validation of the numerical simulationsof the Foehn. The Foehn study in an Alpine valley has been recognized as a major scientificobjective of the Mesoscale Alpine Program (MAP), (Binder et al 1996, Bougeault et al 2001).2. Experimental Design290One of the scientific objectives of MAP addressed the four-dimensional variability of theFoehn flow in the Rhine valley. Of special interest were the investigation of the dynamicalprocesses which determine the spatial extension and the temporal variation of the Foehn. Thefield experiment FORM (Foehn in the Rhine Valley during MAP), dedicated to this objective,was conducted from September 7 th to November 15 th 1999, including 10 intensive observingperiods (IOP). A unique observing network was deployed, for details see Bourgeault et al.,2001. Fig.1 shows the FORM experimental area.One of the two wind profilers was the wind-temperature Radar (WTR) of our institute. TheWTR is a mobile system, especially designed for probing the lower atmosphere.The WTRworks in two modes: the RASS-mode and the clear-air-mode. In the RASS-mode the WTRrecords the air temperature by detecting the propagation of sound pulses with a RADAR. Inthe clear-air-mode the WTR observes the electro-magnetic structure parameter of the2,refractive index C n which in contrast to its acoustic counterpart is mainly dominated bymoisture fluctuations but much less by temperature fluctuations.The WTR has a five-beam geometry with two bistatic radiofrequency (rf) and one acoustic(ac) antenna. The rf antenna emits continuous waves that are frequency shifted with a sawtooth modulation (FM-CW Doppler Radar) in order to provide a fine range gate resolution.The sound source is not only used to measure the vertical sound velocity and hence thetemperature, but also to estimate the wind components in the so-called RASS-mode. This ispossible because the ac beam is simultaneously shifted in the same four oblique beamdirections like the rf beam. The combination of the RASS mode and the clear air mode allows
estimating two independent and redundant wind profiles. A description of the profiler is givenin Bauer-Pfundstein, 1999.3. Model DesignThe numerical simulation is performed with the non-hydrostatic model Meso-NH based onthe anelastic equation system. Two simulations domains are used with the two-way interactivegrid-nesting technique of Stein et al. (2000), the horizontal mesh size being 10 km and 2.5km. Domains and physical parametrizations are as described in Lafore et al. 1998, except forthe use of the most recent radiation scheme of ECMWF (Morcrette et al.2001).The simulation starts at 12 UTC November 5 th. It is initialized with two mesoscale analyses,performed at the resolution and on the horizontal grid of each of the two nested models, withthe CANARI/DIAGPACK assimilation system, developed at Meteo-France and based onoptimal interpolation (Calas et al. 2000). Lateral boundary conditions are provided by timespaceinterpolation between operational analyses of the ARPEGE system of Meteo-France,available every 6 hours.4. Experimental Data and Model ResultsThe descending of one strong Foehn in the area of Rankweil from upper layers down to thesurface can be seen best by means of time-height cross sections of wind and temperature.Figs. 2 and 3 are showing the virtual potential temperature and the S-N wind component,respectively measured by the WTR. Strong south wind was detected first at an altitude of 1.2km around midnight November 4 th . It lasted more than 19 h until the Foehn penetrates downto the valley floor. The descending was not uniform but with some intermittent periods.Nevertheless an overall descending rate of 33 m/h is estimated. More details of this Foehnevent will be found in Jaubert et al. 2003.Four periods of IOP15 are evident:1. onset of Foehn, heating and eroding of the stagnant cold pool,2. break through of Foehn to the surface,3. intermittence of Foehn,4. arrival of the perturbation and end of Foehn.Fig. 4 is showing simulated potential temperature along a S-N transect in the Rhine valley forfour selected time periods (16, 19, 23 UTC, Nov. 5th and 6 UTC, Nov. 6th). Left hand side ofFig. 4 is a similar viewgraph of the wind parallel to the cross-section and Fig.5 is themodelled air flow near the surface (90 m level). When comparing the depth of the cold airpool for different time periods measured by WTR to the depth simulated by Meso-NH, themodel simulation is very close to the measurements.6. ConclusionThanks to the excellent resolution in time and height of temperature and wind fields measuredby the WTR it is possible to get a very detailed picture of the evolution of this Foehn event.The model simulations are in good agreement with the observations. So it will be possible toquantify the physical processes involved in the removal of the cold pool and the instationarynature of the Foehn flow. This will be a significant key to better understanding and, hopefully,to forecast Foehn episodes.291
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MST10Tenth InternationalWORKSHOPOn
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MST 10 Group PictureMay 15 th , 200
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TENTH INTERNATIONAL WORKSHOP ON TEC
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Table of ContentsPREFACE ..........
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I.2.18 FURTHER OBSERVATIONS OF PMSE
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I.3.27 NEW MST RADAR METHODS FOR ME
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I.4.19 STUDY OF A MESOSCALE LAND-TO
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I.5.502 AN ATTEMPT TO CALIBRATE THE
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PrefaceMST10The Tenth International
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and the local organizing committee,
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The operational aspects and recent
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To improve the understanding of dyn
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Improving MST radar resolution by u
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latitudes, arguing that the former
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Report on Session I.3 “Winds, Wav
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Turbulence.The session then moved i
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Report on Session I.4 “Meteorolog
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Multiple Antenna Profiling Radar (M
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Report on Session II “Novel Persp
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synchronized by GPS and connected v
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The highly positive response of the
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10th International Workshop on Tech
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10th International Workshop on Tech
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Session I.1: Radar scattering proce
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⎡7800 ∂q⎤(3)⎢ 15500q⎥M =
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Figure 2 compares profiles of ω B
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Figure 1: Data from the MST radar a
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Ri =shear2ωB22⎛ ∂u⎞ ⎛ ∂v
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Meridional (deg)1050−5−10Echo P
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Subarray Configuration, Capon Metho
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Fig. 2 PMSE plot (SOUSY Svalbard Ra
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VHF radar interferometry had shown
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turbulence. From Figures 1 and 2, i
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SummaryFrom the aspect sensitivity
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a specific range. In this work, syn
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P C(dB)(a) Echo Power60504030200.70
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most occidental area of South Ameri
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Quegan, 1992). It should be useful
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measurements, is shown in figure 1(
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The present observations thus empha
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RECENT OBSERVATIONS OF E REGION FIE
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measured spectra in order to separa
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drifts at E and F regions heights b
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• Are characterized by type II ec
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The main parameters that could be o
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THE ROLE OF UNSTABLE SPORADIC-E LAY
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(σ H / σ P )E y (where σ H and
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STUDY OF A LOW E-REGION QUASI-PERIO
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100 m/syrFigure 4: Geometry of the
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Where the notations carry same mean
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Where dx/dt and dy/dt are the veloc
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non-negativity of the image is prio
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spectrum corresponding to the backs
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The Artigas and Machu-Picchu Statio
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Arguments against the second altern
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Extension of the Kolmogorov spectru
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volumeESRvolumeSSRSSR SSRESR ESRSSR
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individual particles in a statistic
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Anomalous spectraTalkner [4] studie
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To observe the E region FAI echoes,
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matter daytime or nighttime and are
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two sub-arrays, each sub-array made
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4. SummaryHere we describe a radio
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Figure 1. E-region DPS4 spectra, ri
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effects. It is therefore plausible
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1996 and high in 2002). The electri
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electric fields map along the geoma
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SNR condition is always difficult a
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Figure-4 Power spectrum plots of a
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As we show below, Jicamarca offers
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particularly during daytime counter
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where ˆδ nm = (δ l − δ m )
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PMSE is more easily interpreted as
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ResultsTemperature climatology• s
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Simultaneous PMSE and NLC observati
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ResultsSeasonal variationMSE are no
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Figure 2: MSE parameters as functio
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Session I.3: Winds, waves and turbu
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poor. It was shown that poor perfor
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The use of diffraction pattern simi
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F 13 (ξ x ′) = (1 − cos 2ψ N)
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Figure 3: (a) Baseline length depen
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3. ResultsFigure 1 shows the amplit
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variability.Figure 4 shows the aver
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Figure 1. Period-time amplitude wav
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the 12-h and 24-h periodicities in
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winds and variances at altitudes 70
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similar correlation with larger mag
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of the refraction index are not equ
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Fig. 8. Zonal wind (top) and temper
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STUDIES ON ATMOSPHERIC GRAVITY WAVE
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1100-1200 hours. From this plot 6.3
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STUDIES ON WINDS AND MOMENTUM FLUXE
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3.4 Monthly variation of momentum f
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DEEP PENETRATIVE CONVECTION AND GEN
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ly changes direction with time with
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189
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191
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193
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These two last relations are the on
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3.2.1 From v ′2 to ɛ kThe questi
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5.2 Frequency distributionsSeveral
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ReferencesAlisse J.-R. and C. Sidi.
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Röttger J. and C.H. Liu. Partial r
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Specular reflection is negligible f
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−0.5C n2 Distribution (PROUST & S
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the beamwidth, α is the zenith ang
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this latitude in late April). Surfa
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Fig. 1. Median (upper) winds and (l
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Fig.1. Lines of constant radial vel
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which have not yet been considered
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is calculated from the radiosonde t
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Figure 3: Time-altitude cross-secti
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Absorption of cosmic noise is cause
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Incoherent scatter spectracompared
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variations of spectral widths, refr
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Figure 1. Diurnal variation of Turb
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further experimental test of the ST
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waves can be observed more clearly
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winter and a minimum in summer near
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The main recently assumed mechanism
Page 245 and 246: Figure 2. Statistics of numbers of
Page 247 and 248: LIDAR OBSERVATIONS OF MIDDLE ATMOSP
Page 249 and 250: latitudinal dependence of the seaso
Page 251 and 252: APPLICATION OF THE DUAL-BEAMWIDTH M
Page 253 and 254: Figure 2: Mean zonal and meridional
Page 255 and 256: JLKLLK/ILIL6II/G/II/G/LEODFLK/LO/DD
Page 257 and 258: The monthly diurnal mean of horizon
Page 259 and 260: Session I.4: Meteorological Phenome
Page 261 and 262: Integration of the VHF wind profile
Page 263 and 264: Figure 1 : Map of the Lago Maggiore
Page 265 and 266: precipitating clouds, the cyclonic
Page 267 and 268: Eyewall(a)(b)(c)(d)Fig. 3: Radius-h
Page 269 and 270: as low as 0.55. The Piura 50-MHz ra
Page 271 and 272: place features in the profile with
Page 273 and 274: • Period 1 (June 1-10): SCCs exis
Page 275 and 276: Sumatera occurs by stratiform cloud
Page 277 and 278: very interesting to note the double
Page 279 and 280: 20(a) Convective Region(b) Transiti
Page 281 and 282: Typhoon LekimaFig. 2 Typhoon Lekima
Page 283 and 284: Fig. 5 Passage of typhoon Hayan on
Page 285 and 286: the 50 cm 2 sensor head, enabling t
Page 287 and 288: 22 June 2000 23:22:23 - 23:24:20 at
Page 289 and 290: the time-height section of a convec
Page 291 and 292: Thurai, M., T.Iguchi,T. Kozu, J.D.E
Page 293 and 294: There are two main mechanisms which
Page 295: Horel, J.D. and Cornejo-Garrido, A.
Page 299 and 300: RASS THETA (K) RASS v-component (m/
Page 301 and 302: Surface winds usually range from 10
Page 303 and 304: weak (maximum of 5 m s -1 ) and the
Page 305 and 306: The vertical component from the VTB
Page 307 and 308: Figure 8 shows the profile of virtu
Page 309 and 310: 2 3D ( , ) ( ) ( ) ˆ ( ) ˆp∆ xm
Page 311 and 312: presented in Praskovsky et al. (200
Page 313 and 314: In Fig. 2 a sketch of a mountain le
Page 315 and 316: In Fig. 8 the lamina is aligned on
Page 317 and 318: Figure 1: composite day (13 days) o
Page 319 and 320: virtual sensible heat fluxes ( Wm-2
Page 321 and 322: 3. Characteristics of precipitation
Page 323 and 324: Fig. 3: Horizontal distribution of
Page 325 and 326: 3. Results and discussionUHF profil
Page 327 and 328: Figure 4. Monthly variation of slop
Page 329 and 330: system with two receiving antennae,
Page 331 and 332: cycle of precipitation. Figure 3(a)
Page 333 and 334: Histogram of Zonal Velocityh=5.13 K
Page 335 and 336: 5. Summary of results and concludin
Page 337 and 338: the two nearby major cities, Chenna
Page 339 and 340: Boundary layer height, km32.521.5(a
Page 341 and 342: Figure 1:Data from the MST radar at
Page 343 and 344: spectral processing. In this partic
Page 345 and 346: 3. Results and discussionIn the pre
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4. SummaryAn attempt has been made
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The purpose of this study is to exa
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Figure1. Three-day average of momen
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3. The improved method to estimate
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But in case of period until 1800 UT
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Session I.5: Operational Aspects an
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The profilers of WINDAS weredesigne
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NOAA, 1994 : Wind profiler assessme
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FIRST RESULTS OF THE BOUNDARY LAYER
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Figure 3. Pulse Design Diagram to s
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MOVEABLE UHF/S-BAND PROFILER/DISDRO
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one-minute Z values determined from
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TOWARD A MULTISENSOR GROUND BASED R
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3. Cloud Evolution Case StudyOn the
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DEVELOPMENT OF A DIGITAL RECEIVER F
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Experiment 1 Experiment 2IPP 999Km
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ELECTRONIC DIGITAL BEAMFORMING IMPL
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The main element of the unit (figur
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.ON-LINE ADAPTIVE DC-GROUND-CLUTTER
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esulting in a widening of the bandw
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ON THE RADIATION EFFICIENCY OF COCO
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Table 2: Experiment #1 results, Tra
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A NEW NARROW BEAM MF RADAR AT 3 MHZ
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Off-zenith beams towards N, S, E, W
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95ALWIN VHF radar: signal powerdB80
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ANTENNA BEAM VERIFICATION USING COS
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Figure 2: A 45 MHz reference sky te
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AN ATTEMPT TO CALIBRATE THE UHF STR
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is at 4.7 km, but in the first 4-ga
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QUALITY CONTROL FOR DOPPLER WIND PR
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The resulting moments are subjected
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SOUSY RADAR AT JICAMARCA: SYSTEM DE
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NEControl andcomputer roomCompCoute
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THE EQUATORIAL ATMOSPHERE RADAR:SYS
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Table 1: Specifications of the EAR
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VHF ATMOSPHERIC AND METEOR RADAR IN
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ased upon a geotechnical engineerin
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VORTICAL MOTIONS OBSERVED WITH THE
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interpolation from the original gri
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A NEW MINIRADAR TO INVESTIGATE URBA
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e eliminated to analyze correctly t
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Session PWG 1: System Calibrations
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Session PWG 2: Data Analysis, Valid
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• the time series vectors x(k) of
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Fig. 4: reflectivity of the hydrome
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Session PWG 3: Accuracies and Requi
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Session PWG 4: International Collab
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Session II.E: NOVEL PERSPECTIVES AN
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2 Proposed AlgorithmReceived signal
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N#4E-1-16E1A1#1#2A-1-1C1#3C-1-19Fig
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of conventional DCMP, with which th
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applying the directional constraint
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while for a beam of finite width, t
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In order to make the process more q
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WHAT IS TURBULENCE SEEN BY VHF RADA
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Enhanced resolution applyingpulse s
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Beckmann, Spizichino, 1964Fig. 8 Po
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Fig. 11 Plots of temporal variation
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Fig. 14 Distributions of phase cent
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Hocking, W.K., Radar studies of sma
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THE STRUCTURE FUNCTION-BASED APPROA
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{ Ui( t), Vi( t), Wi( t)} = { Ui ,
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161). Assumption 2H: the instantane
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Only the second order SF are consid
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fluctuations umk( t ) along the bas
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VHF PARASITIC RADAR INTERFEROMETRYF
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• All the costs of transmitter pr
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Figure 2: Example of range-azimuth
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Target Altitude, km1009080706050403
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ReferencesGriffiths, H. D., A. J. G
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Participants ListAvery, James P.Uni
Page 489 and 490:
Hysell, David L.EAS/Cornell Univers
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Silva, Robert R.ATRADAustraliarsilv
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AAdachi, A. .......................
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TTabary, P. .......................
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