| ne of the primary uncertainties in measuring aerosol optical depths from satellite is in the choice of the aerosol phase function. Various investigators have suggested the ratio of AVHRR channels 1 and 2 could be used to derive a variable phase function suitable for many different aerosol cases. In order to investigate this possibility, a new aerosol model was developed from a large data set of in-situ aerosol size distribution measurements and used to model the satellite response. The model results suggest the ratio of AVHRR channels 1 to 2 can be used to roughly derive the aerosol phase function value. In order to test the modeling results, aerosol optical depths were obtained from satellite images and were compared with ground based sun photometer measurements. Both methods were in reasonable agreement for this study although clouds made exact comparisons difficult.;Error analysis of the aerosol optical depth derived from AVHRR satellites was also performed. The error was found to be dependent on the scattering angle with largest errors occurring near 120 degrees corresponding to the minimum in the aerosol phase function. Sources of error studied here include sun glint, sensor noise, sensor calibration, water vapor absorption for channel 2 and ozone absorption for channel 1. For the scattering angles with the largest errors, near 120 degrees, the one standard deviation errors in the aerosol optical depth were approximately... |
