Coincident in situ and W-band radar measurements of drop size distributionin a marine stratus cloud and drizzle

Investigation of precipitation formation requires measurements of the drop size distribution in a cloud. These measurements have usually been made usi ng ground-based radar systems or aircraft in situ probes. Difficulties enco untered in practice using these systems include accounting for the air moti on at points remote from the radar systems and small sample volumes measure d using the aircraft probes. An airborne W-band radar system provides a mea surement from a much larger sample volume, close to the aircraft, with a co rrection for air motion possible using the data from the aircraft inertial navigation system. The Coastal Stratus Experiment conducted off the coast o f Oregon in late 1995 provided W-band radar and microphysical probe data sa mpled from much of the same region of a marine stratus cloud. The unique co mbination of cloud probes and W-band radar on board the University of Wyomi ng King Air allowed the radar sampling to be only 60 m away from the probe sampling region. Doppler spectrum data from the W-band radar were used to p roduce estimates of the drop size spectrum density N(D). These estimates we re compared to measurements of N(D) taken by the Particle Measuring Systems forward scattering spectrometer, 1D, and 2DC probes. This comparison sugge sts that a vertically pointing airborne W-band radar is a viable remote sen sing tool for measuring N(D) in clouds and precipitation. This radar provid es information on drop size distribution variation on a much smaller horizo ntal scale than the probes as a result of the much higher sample rate and l arger measurement sample volume.