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 D_ge from combined lidar and radar measurements. In the algorithm, the lidar extinction coefficient σ is parameterized as σ = IWC[a_o + (a₁ID_ge)] and water equivalent radar reflectivity factor Z_e is parameterized as Z_e = C' (IWC/p₁)D^b_ge where a_o, a₁, C¹, 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 D_ge is also developed using the optical depth and mean radar reflectivity factor of the cloud layer.