J1.12 Satellite Monitoring of the First Indirect Aerosol Effect: Retrieval of the Droplet Concentration of Water Clouds

Tuesday, 11 July 2006: 4:45 PM
Ballroom AD (Monona Terrace Community and Convention Center)
Reinout Boers, KNMI, De Bilt, Netherlands; and J. R. Acarreta and J. L. Gras

A model for the vertical variation of microphysical and optical properties of single-layer water clouds is used to design a procedure to obtain cloud droplet concentration from satellite cloud optical depth / effective radius retrievals. This method is applied to data from the MODIS instrument aboard the EOS-TERRA satellite platform over a region near Cape Grim, Tasmania over the Southern Ocean. At this location there are seasonally repeated well-described variations in cloud droplet concentration. The satellite observations show that there is a factor 2.5 difference in droplet concentration between the summer and winter seasons as measured over the four year period (Jul 2000 – July 2004), which agrees well with Cloud Condensation Nuclei concentrations observed at Cape Grim. Cloud droplet concentration is a key parameter to monitor the first indirect aerosol effect. This analysis demonstrate that the MODIS instrument on-board the EOS-TERRA and AQUA platforms can be applied in a strategy to monitor the indirect aerosol effect.
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