Multispectral satellite analysis of marine stratocumulus cloud microphysics.

Abstract

Variations in marine stratocumulus cloud microphysics during FIRE IFO 1987 are observed and analyzed through the use of NOAA-9/10 AVHRR satellite data and aircraft in-cloud measurements. The relationships between channel 3 reflectance and cloud microphysical properties are examined through model reflectances based on Mie theory and the delta-Eddington approximation, and reveal a channel 3 reflectance dependence on cloud droplet size distribution. Satellite observations show significant regions of continental influence over the ocean through higher channel 3 reflectances resulting from the injection of continental aerosols and the associated modification of cloud droplet characteristics. Channel 3 reflectance gradients across individual cloud elements correspond to radially varying cloud droplet size distributions within the elements. Various mesoscale and microscale features such as ship stack effluent tracks and pollution sources are observed in the data. Correlations between reflectance values and aircraft measurements illustrate the potential of estimating cloud droplet size distribution and marine atmospheric boundary layer aerosol composition and concentration through use of satellite data. Such an estimation technique may prove useful in determining climatic implications of cloud reflectance changes due to the influence of natural and man-made aerosol sources, and provide a means to assess the performance of boundary layer electro-optic systems. Keywords: Radiometry; Cloud physics. Theses. (edc) 24u