Ice cloud microphysical properties and their relation to the dissipation process observed by ship-borne cloud radar

Ice clouds with different generation mechanism may response differently to climate change, which is still an open question. In this study we focus on the dissipation process of ice clouds using 95-GHz cloud radar onboard Research Vessel Mirai (JAMSTEC). The areas include the Western Tropical Pacific, North-East off shore Japan and the Arctic. Ice microphysics and air motion were first retrieved by radar-only algorithm with multi-parameter; radar reflectivity factor, Doppler velocity and linear depolarization ratio. The method is validated by in-situ measurements and by comparison with the Equatorial Atmospheric Radar (EAR). These results were compared with the output from the CCSR-NIES-FRCGC GCM along the cruise tracks. The GCM tended to overestimate the grid-mean IWC for mid-level clouds in both Tropics and mid-latitude. Such overestimation was due to the over prediction of IWC in cloud rather than the cloud fraction. We also found that the performance in the prediction of ice cloud microphysics in GCM depends on the latitude. These differences reflect the treatment of formation and duration of ice clouds in GCM. In order to further quantify the duration mechanism for ice clouds, the dissipation rate of ice clouds are estimated from the retrieved air motion, terminal velocity and IWC of non-spherical ice particles, which are then compared with the value estimated in the GCM.