Cloud-Aerosol-Radiation ensemble modeling system (CAR): one application on aerosol climate effects

Description

The Cloud-Aerosol-Radiation (CAR) ensemble modeling system has recently been built to determine (via intercomparison across all schemes) or reduce (e.g., via the optimized ensemble integration) the range of the uncertainties caused by the likely cloud-aerosol-radiation interactions. In the CAR, cloud, aerosol, and radiation transfer have been separated; the radiative effects of cloud including cloud vertical overlap and aerosol including aerosol first indirect effects are explicitly treated. By using the climate model coupled with the CAR, the comprehensive studies on the different roles of the different cloud/aerosol/radiation factors in cloud-aerosol-radiation interactions and their feedback can be conducted. In this study, to show the complicated interactions among cloud, aerosol, and radiation, the influences of the following factors, such as cloud scheme combinations, cloud vertical overlap treatments, radiation transfer schemes, cloud droplet number schemes, and aerosol optical property schemes on aerosol direct effects and first indirect effects have been investigated both offline at the U.S. Southern Great Plains for the year 2000 and online over the U.S. by using CWRF/CAR (the regional Climate-Weather Research and Forecasting Model). Our preliminary results clearly show that all the above factors obviously affect aerosol direct and first indirect effects. The substantial model differences among different CAR cloud/aerosol/radiation scheme combinations suggest the limited physical descriptions of cloud-aerosol-radiation interactions in current models and the potential powerful application of CAR on cloud-aerosol-radiation interactions. Some results from CESM1.0/CAR are also shown.