Aerosol optical depth variability in the Northeastern Arabian sea during winter monsoon: a study using in-situ and satellite measurements

Abstract

Presents study consists the results of the Sun photometer measurements of aerosol optical depth (AOD) over the northern Arabian Sea during December 4-17, 2004 along with OCEANSAT-1 Ocean Colour Monitor (OCM) data derived AOD estimates. In-situ AOD ranged between 0.15-0.38 at 500-nm wavelength (with a mean of 0.274). Relatively higher values of angstrom exponent (mean=1.8) were observed during the cruise period, indicating presence of smaller particles, which seem to have advected from Indian subcontinent and associated with favorable wind conditions as shown by wind vector data from Quickscat scatterometer. The Spatial distribution of the AOD over the study area was derived using OCEANSAT-1 OCM satellite data. OCM derived AOD images showed plumes of high aerosol optical depth originating near the coastal regions and dispersing over oceanic regions. The satellite data derived AOD values were also compared with in-situ measurements. OCM derived AODs matched well with in-situ measurements having an RMSE of sixteen percent for seven match-up points.