Why
Mie? Accurate observations of vertical
air velocities and rain drops using a cloud radar
Dr. Pavlos Kollias
Rosenstiel School of Marine and Atmospheric Science, Miami, Florida
This talk demonstrates an innovative method
for the observation of vertical air motion and raindrop size distribution in
precipitation using a 94-GHz Doppler radar. The method is particularly
appealing since it is based on fundamental physics—the scattering of microwave
radiation by large particles (Mie scattering). The technique was originally
proposed in 1988 by Dr. Roger Lhermitte, who ironically pioneered the
development of 94-GHz Doppler radars for the study of nonprecipitating clouds.
Since then, no real effort for the evaluation and demonstration of the
technique was undertaken. In this talk, observations from stratiform rain are
presented to illustrate the potential and accuracy of the method. The
retrievals from this technique provide vertical air motion to an accuracy of
5–10 cm s
1 .
Despite attenuation, the Doppler velocity measurements remain unbiased and the
data revealed high-resolution kinematical and microphysical structures within
the stratiform precipitation for the first time. We will expose the potential
of this technique, which serves as another example of the visionary
contributions that Dr. Lhermitte has made to radar meteorology.