32nd Conference on Broadcast Meteorology/31st Conference on Radar Meteorology/Fifth Conference on Coastal Atmospheric and Oceanic Prediction and Processes

Thursday, 7 August 2003: 8:45 AM
Vertical wind oscillation observed by vertically pointing W-band radar
Yuichi Ohno, Communications Research Laboratory, Koganei, Tokyo, Japan
Poster PDF (1.2 MB)
Communications Research Laboratory developed a W-band (95.04GHz) cloud profiling radar called "SPIDER". This radar is sensitive enough to observe non-precipitating clouds, which are difficult to be observed by lower-frequency weather radars. However, this W-band radar has a disadvantage for rain observations because of larger attenuation compared with lower-frequency radars. Lhermitte (1988) found that a vertically pointing W-band radar can measure vertical wind in rainy environment using Mie scatter theory. Information of vertical air velocities is necessary to measure accurate drop-size distributions of rain from the vertically pointing radar. In Dec 2002 and Jan 2003, we operated SPIDER pointing vertically from the ground and Doppler spectra were obtained during a few rain events. When a low pressure system passed over Japan in January, vertical winds during rain were observed by SPIDER using Lhermitte's methods up to 1 km over 5 hours. The measured vertical winds show clear vertically coherent oscillations that have a 1 m/s amplitude and a 5-6 minute period. The oscillation is probably related to gravity waves, but the cause of the oscillation is still unknown. We will compare these data with data from a disdrometer as well as a vertically pointing L-band radar. Drop-size distribution affected by vertical air motions will be discussed.

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