Investigation of ice-cloud radition intereaction in a general circulation model

Incorporation of the prognostic microphysics scheme to model the grid-resolvable precipitation physics in general circulation models (GCMs) influences the simulated climatology in various ways: 1) the microphysics effect that represents clouds and precipitation processes with ice phases in the bulk microphysics scheme, 2) the cloudiness effect that considers the ice-phase properties in computing fractional cloudiness, 3) the radiation property effect that considers the ice-cloud properties in the radiation algorithm, and 4) the detrainment effect that considers the detrained liquid species from the convective clouds into the stratiform clouds. The individual role of these processes is investigated on a single column model (SCM) and seasonal simulation framework to improve our understanding of the ice-cloud radiation interaction in GCMs. In both the SCM and GCM simulations, the microphysics effect reduces large-scale precipitation, whereas the corresponding temperature changes are not distinct in the GCM simulations. The cloudiness effect is relatively insignificant in both testbeds. The radiation property effect plays an important role in modulating the temperature and moisture in both testbeds by directly influencing the radiative fluxes. The convective cloud detrainment effect reduces the global-mean precipitation significantly in the GCM simulation, whereas its effect is negligible in the SCM testbed. Our study demonstrates that an understanding of the fundamental characteristics of microphysics and associated cloudiness, radiation properties, and their interaction in modulating large-scale features is pre-requisite to the successful implementation of a specific prognostic cloud scheme in GCMs.