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

Abstract

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 σ is parameterized as σ = IWC[a0 + (a1/Dge)] and water equivalent radar reflectivity factor Ze is parameterized as Ze = C?(IWC/?i)Dbge, where a0, a1, C?, and b are constants based on the assumption of a modified gamma size distribution and hexagonal ice crystals. A comparison of retrieved results from a cirrus-cloud 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.