The sensitivity of precipitation in low clouds to aerosol perturbations

February 04, 2010

Robert Wood (UW)

Hosted by Jeff Collett

Abstract

It is becoming apparent that even modest amounts of precipitation falling from low clouds can have a profound effect upon their coverage, thickness, and organization. It is therefore imperative that we understand the frequency and strength of precipitation produced by low clouds, together with the factors controlling it. Since Albrecht's seminal paper hypothesizing that polluted clouds may precipitate less efficiently than clean clouds and thereby persist longer, there has been much interest in the microphysical controls on precipitation, especially in shallow marine boundary layer clouds which cover vast tracts of the Earth's surface. Satellite measurements from CloudSat are now able to detect light precipitation associated with low clouds, and together with passive satellite sensors we can begin to understand the cloud microphysical and macrophysical controls upon it. In this presentation I will explore some of the new satellite evidence, introduce simple heuristic models of precipitation formation, and show some new aircraft observations which highlight the strongly coupled nature of low clouds and the precipitation they produce.