Aerosol loading in coastal and marine environments in the Indian Ocean region during winter season

The mass loading of aerosols in the coastal and marine environments is studied using a high volume sampler (HVS) and a low pressure impactor (LPI) during the first field phase of the Indian Ocean Experiment (INDOEX), These studies show that aerosol loading at Thiruvananthapuram is in the range 20-130 mu g/m(3) depending on the wind direction. During the sea breeze period, the concentration is low, and during the land breeze period, it is rather high. The mean size distribution obtained using the LPI, in general, shows a trimodal distribution. The measurements conducted on the cruise show that the mass loading over the ocean, near to the Thiruvananthapuram coast, is similar to 25-40 mu g/m(3) which is comparable to that observed on the coast during the day. At Male a significant reduction in aerosol loading is observed when the prevailing flow pattern from north changed to south. This indicates an increased concentration of aerosols in the northern hemispheric air, A sharp decrease in aerosol loading is observed at the Inter-Tropical Convergence Zone (ITCZ), similar to 15 degrees S during the southward voyage of the ship. South of ITCZ, aerosol loading is less than that in the north. A significant reduction in aerosol concentration is observed during the return voyage in the latitude region 12 degrees S to the equator. An enhancement in aerosol loading is observed in the central Arabian Sea (lat, 10-15 degrees N), which is higher than near the Indian coast, The cruise data also showed a significant positive correlation between the columnar aerosol optical depth (at 0.5 mu m wavelength) and the surface mass loading.