Forest fire aerosol forcing of precipitation along the U.S. South Atlantic coast
Ramseyer, Craig Allen
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This thesis uses six case days to examine the effects of aerosols produced by forest fires on the development of deep marine clouds and their ability to precipitate available cloud liquid water (CLW) along the U.S. South Atlantic coast. A proxy for precipitation efficiency (CREP) is calculated using a blended satellite precipitation product and CLW path from the Advanced Microwave Scanning Radiometer – Earth Observing System (AMSR-E), following the methodology of Jin and Shepherd (2008); Berg et al. (2006). This study finds that shallow precipitating clouds are very rare, likely due to precipitation suppression from forest fire aerosols. Upwind aerosol optical thickness (AOT) values of >1.5 are needed for a noticeable impact on precipitation in deep clouds. Cloud effective radius is decreased in all six cases. CREP shows inconsistent aerosol forcing on precipitation for high aerosol cases. The discrepancy may be related to suppression of precipitation when a high percentage of cloud condensation nuclei are thrust above the level of homogeneous nucleation by intense updrafts.