The twilight zone between clouds and aerosols
April 25, 2007
A continuum exists between clouds and dry aerosols, as reported recently in Geophysical Research Letters by scientists from this Branch and colleagues at the Weizmann Institute in Israel. This zone of gradual decline -- a twilight zone-- consists of dissipating cloud droplets and hydrated aerosols. These "in between particles" act to enhance radiances and aerosol optical depth around clouds and throughout a zone extending 10-20 km from the nearest cloud. Because of the widespread distribution of clouds, we expect 30% - 60% of the cloud free atmosphere to be affected. If climate models do not properly represent the physical processes leading to this continuum in the twilight zone, the models will be incorrectly estimating aerosol direct effects and forcing. Full Story