MLS and CALIOP Cloud Ice Measurements in the Upper Troposphere: A Constraint from Microwave on Cloud Microphysics

Abstract

his study examines the consistency and microphysics assumptions among satellite ice water content (IWC) retrievals in the upper troposphere with collocated A-Train radiances from Microwave Limb Sounder (MLS) and lidar backscatters from Cloud?Aerosol Lidar with Orthogonal Polarization (CALIOP). For the cases in which IWC values are small (<10 mg m?3), the cloud ice retrievals are constrained by both MLS 240- and 640-GHz radiances and CALIOP 532-nm backscatter ?532. From the observed relationships between MLS cloud-induced radiance Tcir and the CALIOP backscatter integrated ?532 along the MLS line of sight, an empirical linear relation between cloud ice and the lidar backscatter is found: IWC/?532 = 0.58 ± 0.11. This lidar cloud ice relation is required to satisfy the cloud ice emission signals simultaneously observed at microwave frequencies, in which ice permittivity is relatively well known. This empirical relationship also produces IWC values that agree well with the CALIOP, version 3.0, retrieval at values <10 mg m?3. Because the microphysics assumption is critical in satellite cloud ice retrievals, the agreement found in the IWC??532 relationships increase fidelity of the assumptions used by the lidar and microwave techniques for upper-tropospheric clouds.