Dusty Cloud Properties And Radiative Forcing Over Dust Source And Downwind Regions Derived From A-Train Data During PACDEX

Atmosphere aerosols can directly impact climate by scattering solar radiation and absorbing land-atmosphere long wave (LW) radiation, they also can alter cloud droplet concentrations by increasing cloud condensation nuclei abundance and subsequently affecting the microphysical properties, cloud life and climate. Dusty cloud properties and radiative forcing (RF) over northwestern China (source region) are compared to those over the northwestern Pacific (downwind region) during the Pacific Dust Experiment (PACDEX; April 2007 to May 2007) using collecated data from three satellites in the A-Train constellation:CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations), the Clouds and Earth Radiant Energy System on Aqua, and CloudSat. Dusty clouds are defined as clouds extant in a dust plume environment (i.e., dust aerosols observed within 50 km of the cloud), while pure clouds are those in dust-free conditions. CALIPSO lidar and CloudSat radar measurements are used to discriminate between dusty and pure clouds in both study regions. It was found that dust aerosols change the microphysical characteristics of clouds, reducing cloud optical depth, liquid/ice water path, and effective droplet size. The decreased cloud optical depths and water paths diminish the cloud cooling effect, leading to a greater warming effect. The dust aerosols cause an instantaneous net cloud cooling effect reduction of 43.4% and 16.7% in the source and downwind regions, respectively. The dust aerosol effects appear to be greater for ice clouds than for liquid water clouds in the downwind region. These results are consistent with PACDEX aircraft observations.