Proceedings with Extended Abstracts (single PDF file) - Radio ...

MESOSCALE ALPINE PROGRAMME (MAP):SYNERGIES BETWEEN WIND PROFILERS AND DOPPLERWEATHER RADARSM. Petitdidier 1 , V. Klaus 2 and P. Tabary 3(1) CETP/CNRS, Vélizy, France, monique.petitdidier@cetp.ipsl.fr(2) Meteo France, CNRM/GMEI/STM, Toulouse, France, vladislav.Klaus@meteo.fr(3) Meteo France, DSO/CMR, Trappes, France, pierre.tabary@meteo.frIntroductionDuring the field phase of the Mesoscale Alpine Programme (MAP see Bougeault et al., 2001;Caccia et al., 2001) a number of instruments were deployed in the southern flank of the Alpsin the Lago Maggiore area in order to document atmospheric and hydrological processes. Inparticular the experimental set up included research and operational weather Doppler radarslike the French C-band Ronsard, and Swiss C-band Monte Lema Radar(ML) (5.6GHz). Thisset up provided a coverage of Alpine precipitating systems with a unique spatial and temporalresolution. In order to complement those sets of data, a bifrequency UHF/VHF wind profilerwas installed in the area scanned by the weather radars.The signal of weather Doppler radars(WDR) and VHF wind profilers(WP) are backscatteredby different types of targets, hydrometeors and refractive index inhomogeneities respectively,due to their frequency difference. Their running modes are also different. WDR provide avolume observation of the precipitation system at different elevations and azimuths. Verticalprofiles of wind speed and direction are deduced by VAD(Volume Azimuth Display)analysis or Velocity Volume Processing(VVP) methods. Over the past decades, manymethods have been developed to retrieve the three-dimensional wind field from MultipleDoppler observations, at least 2 radars. The main drawback is that those radars provide noinformation where there are no hydrometeors. The VHF WPs, whatever the frequency is,operate with antennae oriented in fixed positions, 3 or 5, and provide the wind vector andreflectivity profiles near the vertical direction. One of their drawback is that the observationsprovide a cut of the cloud or meteorological event passing over the radar. If the systemcannot be assumed to be frozen at the observed scale it is difficult to separate spatial and timevariations. One interesting point is: the VHF WP provides a description of the air motioninside the cloud and in its environment.This experiment has been an opportunity to test the complementarity of the two types of dataset. First of all, our interest has been focussed on simultaneous wind measurements, then onreflectivity ones.1-Wind comparisonThe VHF wind profiler provides wind vector every 15mn whatever the weather conditionsduring the MAP experiment. The time resolution of wind profiles deduced from the WDR isthe same.254Validation of a new algorithm for WDROne general problem that occurs in the data processing of WDR observations is the foldingof the Doppler spectrum that leads to erroneous wind values. Wind data coming from WPmay be used as a reference basis to avoid ambiguity in Doppler radial velocities obtainedwith WDRs, or to validate new algorithms. Tabary et Petitdidier (2002) validated a Bayesianwind-profile algorithm. This technique applied to WDR data processing does not require anypreliminary defolding of the radar data. As a consequence this algorithm is well adapted tooperational WDRs. The authors used the wind profiler data to validate this new algorithm.