Subtropical Cirrus Properties Derived from GSFC Scanning Raman Lidar Measurements during CAMEX 3

The NASA/GSFC Scanning Raman Lidar (SRL) was stationed on Andros Island, Bahamas for the third Convection and Moisture Experiment (CAMEX 3) held in August - September, 1998 and acquired an extensive set of water vapor and cirrus cloud measurements (Whiteman et al., 2001). The cirrus data studied here have been segmented by generating mechanism. Distinct differences in the optical properties of the clouds are found when the cirrus are hurricane-induced versus thunderstom-induced. Relationships of cirrus cloud optical depth, mean cloud temperature, and layer mean extinction-to-backscatter ratio (S) are presented and compared with mid-latitude and tropical results. Hurricane-induced cirrus clouds are found to generally possess lower values of S than thunderstorm induced clouds. Comparison of these measurements of S are made with other studies revealing at times large differences in the measurements. Given that S is a required parameter for spacebased retrievals of cloud optical depth using backscatter lidar, these large diffaences in S measurements present difficulties for space-based retrievals of cirrus cloud extinction and optical depth.