Long-range transportation of anthropogenic aerosols over eastern coastal region of India: Investigation of sources and impact on regional climate change

Estimation of the effect of long-range transportation of anthropogenic aerosols in India is a real challenge due to the strong influence of local sources. This study addresses this issue from the measurements of aerosol optical and physical properties during 16-31 March 2006 at Kalpakkam (12.56° N and 80.12° E), a remote eastern coastal station in India. Increased anthropogenic aerosols were observed due to long-range transport from Indo-Gangetic Basin (IGB) in comparison to two other sources: central Bay of Bengal (CBoB) and northern Indian Ocean (NIO) as grouped from back-trajectory analyses of air parcels. AOD is found to be maximum of about 0.32 during IGB wind regime followed by CBoB (0.27) and NIO (0.20) winds. MODIS observed AOD is found to be high all along the wind back-trajectories connected from IGB indicating IGB as a source. Black carbon (BC) during IGB wind (2.0 μg·m− 3) is 65% greater than that observed during NIO wind (1.2 μg·m− 3). As a result, single scattering albedo becomes as low as 0.89 during IGB wind while 0.92 during NIO wind. These long-range transported aerosols cause about 65% enhancement of atmospheric radiative forcing and consequently, aerosol heating rate is also increased by about 70% during IGB wind regime (0.36 K/day) compared to NIO wind regime (0.21 K/day). Being a coastal region, Kalpakkam experiences strong diurnal variation of aerosol properties due to land and sea breezes that introduce about 30% increase of atmospheric forcing during land breeze by short-range transport of BC from nearby urban region. The present study concludes that long-range transported anthropogenic aerosols over coastal region of India cause significant enhancement of regional aerosol radiative forcing and their heating effect can have significant consequences for regional climate change by altering hydrological cycle over the tropical continental area.

► Identification of sources of long-range transported aerosols at eastern coastal region of India. ► Indo-Gangetic Basin is a potential source of anthropogenic aerosols transported to East coast. ► Aerosol forcing and heating rate become maximum due to this long-range transportation of anthropogenic aerosols. ► Land and sea breezes cause significant diurnal variation in BC concentration. ► Aerosol forcing enhances by 30% due to short-range transportation of BC during land breeze.