Continental influence on the spatial distribution of particulate loading over the Indian Ocean during winter season

Advection of continental aerosols over to the Arabian Sea and Indian Ocean regions during winter (when the prevailing synoptic wind is north-easterly) has been studied by examining the spatial distribution of the near-surface aerosol mass concentration (M-C). In the northern part of Arabian Sea and north of the inter-tropical convergence zone (ITCZ) M-C is significantly larger than that in the southern side of ITCZ. A prominent high in M-C is observed near the mid-Arabian Sea region similar to 12degrees to 15degreesN. Associated with local convergences introduced by mescoscale weather systems, pockets of high M-C are observed at different locations over the oceanic regions. Significantly low values of M-C are observed in the ITCZ. Surface streamlines and wind patterns indicate advection of continental aerosols from the adjoining landmass over to the oceanic environment. Aerosol mass concentration in the far oceanic region is also influenced by in situ production of sea-spray aerosols, which depends on wind speed. The nature of advection of continental aerosols has been studied by separating the wind-induced component of M-C and chemical nature of the aerosols. The spatial variation of the wind-independent component matches well with that of the non-sea-salt aerosols estimated from chemical composition. (C) 2003 Elsevier Ltd. All rights reserved.