Cirrus Cloud Microphysical Property Retrieval Using Lidar and Radar Measurements. Part I: Algorithm Description and Comparison with In Situ Data

A retrieval algorithm is described to estimate vertical profiles of cirrus-cloud ice water content (IWC) and general effective size Dge from combined lidar and radar measurements. In the algorithm, the lidar extinction coefficient s is parameterized as s 5 IWC[a0 1 (a1/Dge)] and water equivalent radar reflectivity factor Ze is parameterized as Ze 5 C9(IWC/ri) , where a0, a1, C9, and b are constants based on the assumption of a b Dge modified gamma size distribution and hexagonal ice crystals. A comparison of retrieved results from a cirruscloud case study with aircraft in situ measurements indicates that the algorithm can provide reliable cirrus cloud microphysical properties. A technique to estimate ice water path and layer-mean Dge is also developed using the optical depth and mean radar reflectivity factor of the cloud layer.