Simulating cloud-microphysical processes in CRCM5 Ping Du, Éric Girard, Jean-Pierre Blanchet

The current microphysics scheme in GEM climate is a single-moment bulk scheme, in which only the mass-mixing ratio of total cloud water prognosed and a simple temperature dependency is used to separate the cloud water amounts into liquid and frozen componets. In this single-moment scheme the development of precipation is diagnosed solely from the evolving cloud-water field. This simple microphysical conversion processes can not properly represent the complicated in- cloud microphysical processes. So an advanced microphysical scheme is need to improve the simulation of precipitation rate, in-cloud microphysical structure,cloud- aerosol interaction and cloud-radiation interactions. We plan to implement and evaluate the performance of a multi-moment microphysicas sheme in the framework of CRCM5, to compare the simulated cloud-microphysical variables against cloud-radar data and a collocated evaluation of the surface radiation and precipitation rates.

A recent developed double-moment microphysical scheme ( Morrison et al. 2005) is chosen to use in CRCM5. In this scheme, the number concentrations and mixing ratios of four hydrometeor species ( cloud droplets, cloud ice, rain and snow) are prognosed. The new scheme provides a very detailed treatment of the microphysics for cloud and climate models at a reasonable computational cost, it can be utilized in process- oriented studies ranging in scales from global to regional to local depending on the application. And it is useful for studying the influence of anthropogenic aerosol on clouds and radiation since the scheme incorporates close coupling between aerosol and cloud microphysics for liquid, ice and mixed-phase clouds.

Currently the Morrison et al microphysical could scheme is being implemented and evaluated in GEM climate with the resolution of 10km.