Colloquium: May  20, 2008 -- 3:00 pm, EN6085A

Atmospheric aerosols have been recognized to have an effect of modifying the cloud optical and microphysical properties by serving as cloud condensation nuclei (CCN). The estimate of this aerosol indirect effect is one of the most uncertain factors in understanding and predicting climate change. In this talk, I will present my research work on this topic using several types of numerical models and satellite observations.

At first, I will show some results from my previous studies using a General Circulation Model (GCM) and a spectral bin microphysics cloud model in comparison with satellite remote sensing results. The GCM results show that the simulated global correlation statistics of cloud properties with aerosols are consistent with satellite observations when aerosol lifetime effect is incorporated into the parameterization. The simulated results from the spectral bin model are also compared with satellite observations focusing on correlation patterns between effective radius and optical thickness of warm clouds. Effective radius and optical thickness are found to be positively and negatively correlated for non-drizzling and drizzling clouds, respectively, consistent with previous observational findings. Further analysis reveals that the correlation patterns simulated for pristine and polluted air conditions closely resemble the correlation patterns observed over the FIRE and ASTEX regions, respectively, suggesting the significance of aerosols in controlling the particle growth processes over these regions.

I will also introduce my recent work on a global cloud resolving model newly coupled with an aerosol transport model. A short-term simulation result shows that the model reproduces a detailed spatial structure of cloud particle radius over the globe including equatorial regions where traditional GCMs have difficulty in simulating the effective radius distribution. Some other results will be shown from the new model in comparison with satellite observations, including aerosol effect on vertical particle growth processes. This aerosol-coupled global cloud resolving model can be further used in future studies especially for comparison with new A-Train satellite observations including CloudSat and CALIPSO. Some potential applications of combined use of the new global cloud model and A-Train observations will be discussed.