English abstract
Atmospheric aerosols play a vital role on the dynamics of climate processes through direct and indirect effects. Dust storms originating over the world's and regions contribute a large fraction of aerosols in the atmosphere. Using remote sensing data, an anomalous enhancement in the biological productivity of sea was observed in the Gulf of Oman which was attributed only to cold sea surface temperature (SST) eddies (during November to early December months of 1996-1999), whereas recent study has shown that during dust storms (June-July-August and October-November-December months of 1997-2004), major nutrient supply is from atmospheric dust deposition. We have carried out a study of individual cases of major dust storms over the Arabian Sea during the entire year (December 2003 -December 2006) to quantify role of dust storms and changes in ocean surface due to chlorophyll bloom. Using Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua, we have found that the deposition of dust along the passage of major dust storms (aerosol optical depth (AOD) ∼0.25-0.41) occuring over the Arabian Sea causes chlorophyll blooming (usually 10-22.43 Mg/M3) within a period of 1-2 to up to 3-4 days. However, we have also found significant anomalous cooling of the ocean surface (SST) and relatively higher ocean wind speeds (QuikSCAT) during dust storms that may lead to favorable conditions for blooming. Exact nature and cause of chlorophyll bloom in the sernienclosed northern Arabian Sea, surrounded by one of the world's major sources of dust storms (Africa, Middle East, Iran, and Afghanistan), are very important in understanding the productivity and the biogeochemical cycles of the marine ecosystem. The results have been validated using the Indian Remote Sensing Polar-4 Ocean Color Monitor (IRS P4 OCM) data.
