Ice Production Rate in Precipitating Ice Cloud: A Comparison between Synergic Satellite Observations and GCM Outputs

Ice clouds and floating snow are ubiquitous globally. They play critical roles in the Earth's energy and hydrological budgets. Understanding and accurately representing the cloud and precipitation cycle in models, especially the changes over short period of time, require intensive observations and deep understanding of the coupled cloud-precipitation processes.

As the key parameter that determines the ice cloud development and decay throughout the diurnal cycle, ice production rate (IPR=dQi/dt, where Qi is the ice mixing ratio, and dt is the GCM timestep) in General Circulation Models (GCMs) is by far only constrained by lab experiments and very limited field campaign measurements. In this study, we will use synergized multiple spaceborne passive microwave (MW) instrument measurements to derive the first tropical IPR map, which will also be compared to GEOS-5 and MERRA2 outputs.

Our previous effort developed an empirical forward model to retrieve the ice water path (IWP) for thick anvils and floating snows from high-frequency microwave (MW; 150 - 190 GHz) passive sensors using collocated CloudSat measurements as the baseline. In this work, we will apply this approach to Global Precipitation Measurement Microwave Imager (GPM-GMI) and Megha-Tropiques Soundeur Atmospherique du Profil d'Humidite Intertropicale par Radiometrie (MT-SAPHIR) measurements to retrieve the CloudSat-consistent IWP in the tropics for different local times because of the procession orbit design of the two satellites. The IPR map will then be derived from collocated and time-lagged retrievals from the two passive instruments. Lastly, we will compare the derived IPR with model outputs to understand better the model-observation discrepancies of ice cloud diurnal cycle.