Aerosol Effects on Thin Clouds – Not all Clouds are the Same


Scientists in the DOE Atmospheric Radiation Measurement (ARM) Program used a cloud resolving model and found that aerosols affect thin and thick clouds differently. Thin clouds cover approximately 30% of the globe and play an important role in the Earth’s radiation budget. In thin clouds, if aerosols increase the total water content in these clouds, the reflection of sunlight would be increased and the clouds would cause cooling. Thin clouds were studied for which rain did or did not reach the Earth’s surface. Clouds from which rain reached the Earth’s surface had increased aerosols and increased water content. Conversely, clouds from which rain did not reach the Earth’s surface had reduced aerosols but increased water content due to a differing microphysical process. Comparisons of these results with results from the literature for thicker and warmer clouds suggest that these two cloud types have different interactions with aerosols. These results suggest that different approaches need to be considered in climate models for different cloud types to represent aerosol-cloud interactions to assess aerosol effects on clouds and hence climate.


Lee, S. S., J.E. Penner, and S.M. Saleeby, 2008: Aerosol effects on liquid-water path of thin stratocumulus clouds, submitted to J. Geophys. Res.