P13.4
How stratiform-like is stratiform rain observed with a 94 GHz Doppler radar?
Pavlos Kollias, Univ. of Miami/RSMAS, Miami, FL; and B. A. Albrecht
Scattering of raindrops using a very short wavelength radar ( l=3.2 mm) is described by Mie scattering. Using a new technique and taking advantage of the Mie signature on the observed Doppler spectrum, the partitioning of the vertical air motion and subsequently the retrieval of the raindrop size distribution under convective and stratiform conditions is possible. The high spatial and temporal resolution and the small beamwidth further enhance the accuracy of the retrievals. During the summer of 1999 the cloud radar and a collocated 915 MHz wind profiler were used for precipitation studies. Data collected in stratiform rain in South Florida illustrate the enormous potential of 94 GHz Doppler radars in highlighting details and structures of the vertical velocity and microphysical field in stratiform rain. The vertical air motion variance profile exhibits a maximum at low levels (below 500 m), and 90% of the vertical velocity measurements have magnitude less than 0.2 ms-1. The microphysical field is homogeneous in the vertical dimension with large variability in the horizontal. The decorrelation time scale of the DSD parameters (Do , L and m) increases with height reaching 3-5 min at 1 km above the ground. Finally, an interesting comparison of the retrieved air motion from the cloud radar (accuracy within 5- 10 cms-1) and the wind profiler is performed that highlights the limited capability of wind profilers to detect the low amplitude and high frequency variability of the vertical air motion.
Poster Session 13, Quantitative Rainfall—Microphysics II
Monday, 23 July 2001, 2:00 PM-3:30 PM
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