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<br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />.---- 'I" <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />Experiment 6: Precipitation processes <br /> <br />Lead Scientist: Robert M. Rauber <br /> <br />Participating Scientists: Alexis B. Long, Patricia A. Walsh, DRI <br />Robert A. Kropfli, William R. Moninger, <br />Jack B. Snider, Taneil Uttal, WPL <br />Lewis O. Grant, CSU <br />Norihiko Fukuta, Kenneth Sassen, UU <br /> <br />The objective is to describe the microphysical processes likely <br /> <br />responsible for precipitation particle growth and the rates of these <br /> <br />processes. The analysis will examine graphic displays of C-band radar <br /> <br />reflectivity factor Z and Ka--band radar equivalent reflectivity factor <br /> <br />Ze and circular depolarization ratio COR for significant changes indica- <br /> <br />tive of precipitation particle growth in the clouds. Focus will be on <br /> <br />changes in these variables occurring along Lagrangian particle trajec- <br /> <br />tories. <br /> <br />The analysis will also examine time-height plots of lidar <br /> <br />linear depolarization ratio 0 . for features representing growing precipi- <br /> <br />tation particles. Such a feature might, for example, start as a cluster <br /> <br />of depolarization ratios of ~,o. 5 indicative of pristine ice crystals. <br /> <br />They may emanate from a "generating cell" in the upper reaches of the <br /> <br />cloud. <br /> <br />If the crystals fall through a region of supercooled water <br /> <br />(revealed by depolarization ratios near zero) they will become rimed and <br /> <br />the depolarization ratios of tlhe ice particles will increase, perhaps to <br /> <br />- 0.6 if there is moderate riming. Alternatively, a feature might start <br /> <br />as a cluster of depolarization ratios of - 0.2 indicative of oriented ice <br /> <br />crystals. <br /> <br />If the crystals fall toward the surface without encountering <br /> <br />any riming, the depolarization ratios may only increase to - 0.5. <br /> <br />The surface microphysics observations will be made at the terminal <br /> <br />points of the trajectories of some of the precipitation particles. It <br /> <br />will be possible then to char'acterize the particles and the precipita- <br /> <br />33 <br /> <br />rZ;::-.. <br />