Events

University of Puerto Rico - Río Piedras

Environmental Sciences

 

SEMINAR

 

“From expanding marine stratocumulus to suppressing hurricanes: aerosols impacts on precipitation and the dynamic response of cloud systems”

 

Abstract

A large fraction of air pollution, smoke and desert dust aerosols serve as cloud drop condensation nuclei (CCN). Larger CCN concentrations nucleate a greater number of smaller cloud drops, which are slower to coalesce into rain drops. The formation of rain leads to downdrafts that replace the updrafts that formed the cloud at the first place. Therefore, delaying the rain incurs profound dynamic response on the clouds. In marine stratocumulus a regime change from open to closed cells with full cloud cover is observed. In deep convective clouds delaying the rain enables the lofting of the cloud water to the freezing level and realizing the latent heat of freezing before precipitation. This invigorates the clouds into thunderstorms. The dearth of CCN explains, at least in part, the scarcity of lightning in maritime clouds. The invigoration of clouds in the periphery of hurricanes that ingest air pollution or desert dust occurs on expense of the intensity of the convection in the eye wall, and so decreases the intensities of these storms. All of this underlines the importance of long term measurements of cloud aerosol interactions, especially in a place such as Puerto Rico, where desert dust and other aerosols occasionally interact with the normally pristine maritime clouds.

 

 

Dr. Daniel Rosenfeld

Institute of Earth Sciences

The Hebrew University of Jerusalem

 

January 27, 2010

4:00 pm