Long-term change in aerosol characteristics over Indo-Gangetic Basin: How significant is the impact of emerging anthropogenic activities?

Long-term aerosol characteristics were assessed over the Indo-Gangetic Basin (IGB) using satellite-derived aerosol properties from January 2007 to December 2017. The study shows steadily high aerosol optical depth (AOD ~0.7) with a decadal increasing trend (~20%) over the IGB. Angstrom exponent (AE) shows a relatively large increasing trend at Lucknow in the central IGB (~25%) as compared to Delhi in the north-west IGB (~18%), which suggests relative increase in fine-mode aerosols at Lucknow (~30%). Though, single scattering albedo (SSA) does not show any considerable decadal trend at both the stations, the ultraviolet-aerosol index (UV-AI) shows an increasing trend, with a pronounced increase at Delhi (~26%) compared to Lucknow (~20%). Result suggests relative dominance of absorbing dust aerosols over Delhi. Further, to understand the impact of emerging activities, analyses were done in two sub-periods: 2007–2012 and 2013–2017. Interestingly, a relative increasing trend in AOD (~31%) is observed at Delhi compared to Lucknow during 2007–2012, which was observed at Lucknow (~22%) during 2013–2017. The emission inventory corroborates with the trend and variability of optical properties for different sub-periods, and results show intense development activities in the region have an influence on vertical as well as horizontal aerosol load. [Display omitted] •Lang-term aerosol characteristics were assessed at two contrasting sites over IGB.•A decadal increasing trend in AOD by ~20% was observed over the IGB.•Pronounced increase in AE at Lucknow suggests relative dominance of fine particles.•Pronounced increase in UV-AI at Delhi suggests relative dominance of absorbing aerosols.•PM10 is ~2.5 times higher at Delhi than Lucknow associated with intense developmental activities.