Characterization of Aerosol Types by Columnar Optical Properties Analysis at a Coastal Site on Eastern Seaboard of India

The coastal stretch of the northwestern Bay of Bengal experiences a mixture of aerosol types from a variety of sources attributed to spatial heterogeneity. The present study aims to identify aerosol types from ground-based spectral measurements of Aerosol Optical Depth (AOD) at Gopalpur (19.30 degrees N, 84.88 degrees E), a coastal site on the eastern seaboard of India. The spectral variation of AOD exhibits four distinct types viz. strong wavelength-dependent with a high loading of fine and coarse aerosol (type 1), strong wavelength-dependent with low loading of fine and coarse aerosol (type 2), weak wavelength-dependent with a high loading of fine and coarse aerosol (type 3) and weak wavelength-dependent with low loading of fine but high loading of coarse aerosol (type 4).The seasonal variation of aerosol size characterization revealed the prevalence of coarser mode particles during pre-monsoon (March-June) and monsoon (July-October) period. The coarse mode aerosols during premonsoon were attributed to transport of dust, minerals, and local sea spray aerosols, whereas during monsoon due to wet removal of finer aerosol particles. In contrast, the dominance of fine mode particles was observed during postmonsoon (November-February) possibly due to strong local anthropogenic emission and advection of finer particles. In addition, AOD variations were strongly associated with daily fluctuations in wind speed. The relatively higher wind speed during premonsoon acts conducive to the genesis of relatively larger aerosol particles such as sea-salt. The present study complements the information on daily and seasonal variability of aerosol size characteristics that could be critical in filling gaps for global-level assessment. Additionally, this study strengthens the existing knowledge of the aerosol influence on the regional weather pattern, contributing to a more comprehensive understanding of the regional climate system in response to anthropogenic forcing.