Spatial distribution and vertical structure of the MABL aerosols over Bay of Bengal during winter: results from W-ICARB experiment

Abstract

The first ever in-situ measurements of size-segregated vertical profiles of aerosol in the marine atmospheric boundary layer (MABL) over the Bay of Bengal (BoB), made at five different locations during the winter Integrated Campaign of Aerosols, gases and Radiation Budget (W_ICARB) experiment is presented which showed large spatial variability in aerosol properties over BoB with high aerosol concentration over northern BoB >500 cm⁻³) and low aerosol concentration (≤100 cm⁻³) over southern BoB with a moderate aerosol concentration (250–450 cm⁻³) over far east BoB. The altitude variation of aerosol number density is found to be steady in the convective boundary layer (up to ∼400 m) at all locations over BoB and above that the aerosol concentration is found to decrease, except at far eastern BoB. Over far eastern BoB, the altitude distribution of aerosol number concentration showed an increase at ∼600 m. Examination of the simultaneous air mass back trajectories along with the observations aerosol size distribution indicates that while the aerosols advected from IGP have a strong natural (coarse mode) component where as those from the east-Asia region are in general accumulation mode (anthropogenic) dominant.