Airborne measurement technologies: Airborne Multiparameter Precipitation Radar (CAMPR) observation of wind fields in snow clouds

Abstract

The CRL airborne multiparameter precipitation radar (CAMPR-D) is equipped with a dual-beam antenna to measure three-dimensional wind fields in precipitation. This paper describes the methods and related problems of wind-vector calculation, and shows the results of dual-Doppler analysis. The observation data was obtained through the WMO-01 (Winter MCSs Observations over the Japan Sea 2001), the objective of which was to reveal the structure of snow clouds over the Japan Sea. First, the trajectories of the front-and rear-antenna beam were investigated. The results showed that there were some gaps between the two beam footprints due to the speed and direction of the wind relative to the aircraft, and that the front beam did not overlap the rear beam in some regions on the leeward side. The investigation also demonstrated that the data from a flight-information system (POS) consisting of an optical fiber gyroscope and a differential GPS is effective in removing the aircraft velocity component from the measured Doppler velocity. Finally, some distributions of the wind vectors in the along-track vertical sections are shown. The wind vectors were analyzed using the observation data for linear clouds in the JPCZ (Japan Sea Polar-airmass Convergence Zone). The distributions showed that updrafts were dominant over the sea because of developing convective cells, and that the repetition of updrafts and downdrafts seemed to indicate roll convections. The distributions also showed a common structure of anvil echoes that extended northward or northeastward.