J4.1
Liquid water path variability in marine boundary layer cloud
Robert Wood, University of Washington, Seattle, WA; and D. L. Hartmann
The liquid water path probability distribution function (pdf) in boundary layer cloud over the ocean is examined using daytime retrievals for two months of data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Terra satellite. It is shown that the pdf can be described quite well using a modified gamma distribution in accordance with earlier work. The modified gamma distribution is shown to be successful in reproducing the observed pdf moments up to orders 3 or 4, in contrast to the lognormal distribution which tends to overpredict the higher moments. This allows estimations of both albedo biases and biases in process rates that depend upon higher order moments. The geographical distribution and the scale dependence of the pdf properties are presented. In both the NE and SE Pacific low cloud regions the narrowest pdfs are found close to the coast, and broaden markedly as the stratocumulus breaks into trade cumulus. Compositing and regression analysis are used to examine the influence of large scale forcings upon the pdf characteristics. variables
Joint Session 4, Cloud Variability and Its Radiative Effects (Joint between 11th Cloud Physics and 11th Atmospheric Radiation)
Thursday, 6 June 2002, 3:30 PM-5:00 PM
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