Aerosol microphysics over a tropical coastal station inferred from the spectral dependence of Angstrom wavelength exponent and inversion of spectral aerosol optical depths

Six years of spectral aerosol optical depth (AOD) measurements have been analyzed from a tropical coastal site, Trivandrum (8.55 degrees N, 76.9 degrees E, 3 m msl) to infer on the seasonal changes in the microphysical properties of columnar aerosols, by examining the derivatives of the Angstrom wavelength exponent (alpha) in the wavelength domain (alpha'lambda) as well as in AOD domain (alpha'tau) and by retrieving the columnar size distribution by numerical inversion of the AODs. The inference of the changes in the aerosol microphysics drawn from the features of the derivatives alpha'lambda and alpha'tau is consistent with the pattern revealed by the aerosol proper-ties obtained from the columnar size distributions retrieved from the AOD spectra as well as from the surface measurements of mass-size distributions, which are supported by the back-trajectory cluster analysis and the results of chemical species analysis. (C) 2009 Elsevier Ltd. All rights reserved.