The properties of cirrus clouds are only beginning to be understood, yet it is certain that these high clouds represent a relatively significant component of the climate of the earth- atmospheric system. Under this Accomplishment-Based Renewal award, Dr. Sassen will continue his research on the nature of cirrus clouds and their characterization through satellite radiance measurements. The work will include field observations with polarization lidar, radiometers, Ka-band radar and research aircraft; basic laboratory microphysical and backscattering studies; microphysical model parameterizations for application to large-scale cirrus growth models; and lidar scattering simulations for improved data retrieval. The field observations will be conducted in accordance with the "Extended Time Observations" schedule and will support the second "Intensive Field Observations" experiment of the first ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE). Special emphasis will be given to the study of supercooled liquid water in cirrus, and to determining the structure and generating mechanisms present in a variety of cirrus cloud types. The entire observations will be compiled into a set suitable for ISCCP cirrus cloud algorithm verification.//
