Investigation of aerosol indirect effects on regional climate using a cumulus microphysics parameterization

As demonstrated by observational and modeling studies, aerosols can exert significant influence on convection, with the potential to alter the timing and intensity of precipitation as well as provide feedbacks on the large-scale circulation. However, cumulus parameterizations used in climate simulations generally do not include cloud microphysics so aerosol-cumulus cloud interactions are not fully represented to allow investigation of aerosol effects on convection. Recently, Song and Zhang (2011) have developed a physically-based microphysics parameterization for use in the Zhang and McFarlane (ZM) convective parameterization, which allows us to simulate the influence of aerosols on microphysical and dynamical processes for cumulus clouds in regional and global climate model frameworks. We have implemented the new ZM convective parameterization with cloud microphysics and aerosol-cloud interactions into the Weather Research and Forecasting (WRF) model coupled with the physics package from the Community Atmospheric model (CAM5), which is newly developed at PNNL. Simulations are being conducted over China to examine the impacts of the new scheme in simulating cloud properties, vertical mass fluxes, and precipitation compared with the original ZM scheme and to assess the significance of aerosol indirect effects from cumulus clouds at the regional scale. Model evaluation and analysis will be presented for selected case studies.