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 stud ied using a high volume sampler (HVS) and a low pressure impactor (LPI) dur ing the first field phase of the Indian Ocean Experiment (INDOEX), These st udies show that aerosol loading at Thiruvananthapuram is in the range 20-13 0 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 h igh. 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 s imilar 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 obse rved when the prevailing flow pattern from north changed to south. This ind icates an increased concentration of aerosols in the northern hemispheric a ir, A sharp decrease in aerosol loading is observed at the Inter-Tropical C onvergence 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 r eturn voyage in the latitude region 12 degrees S to the equator. An enhance ment 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 als o showed a significant positive correlation between the columnar aerosol op tical depth (at 0.5 mu m wavelength) and the surface mass loading.