Tropical and Midlatiatude Cirrus Cloud Properties and Model Applications

Knowledge about the cirrus properties and the processes in both midlatitude and tropics is of great interest to climate modeling. An innovative algorithm using three Doppler radar moments to retrieve the cirrus microphysical parameters and the air mean vertical motion and their errors simultaneously is applied to a 17- month MMCR data set collected at the ARM SGP and TWP sites. The dataset first allow us to determine the geographic variations and seasonal variations of cirrus clouds. The properties of tropical cirrus clouds are quite different from those found at the SGP site with larger particle sizes and ice masses in stronger ambient updrafts. While the cirrus clouds in the midlatitude have relative larger seasonal variations than tropical cirrus. With this dataset, the interrelationships between the ice particle size, ice water content, and mass weighted particle fall velocity are investigated. The mass weighted particle fall velocity is parameterized as a function of IWC and temperature. As an improved GCMs diagnostic parameterization of cloud properties usually parameterized as a function temperature only (Del Genio, et al, 1996), hopefully this result may improve the cirrus representation in GCMs.