Identifying the natural and anthropogenic drivers of absorbing aerosols using OMI data and HYSPLIT model over South Asia

Aerosols absorption contributes significantly to the total radiative effects of aerosols and so an important component of radiative forcing estimates. Therefore, this study explores the spatiotemporal distribution of ultraviolet aerosol index (UVAI), future trends, potential sources of absorbing aerosols and their relationship with temperature, wind speed, precipitation and total ozone column using Ozone Monitoring Instrument retrieved UVAI and HYSPLIT model over South Asia during October 2004 to March 2022. The mean UVAI within the ranges of 0.56–1.62 are observed over Eastern and Southern Pakistan and Northern India associated with dust and biomass burning aerosols. The interannual variations in UVAI show that the values of UVAI increases from 1.73 to 3.11 during 2018–2021 over the Indo-Gangetic Plain. Contrary to this, UVAI < 0 is observed along the Karakorum and Himalaya range during 2005–2021 indicating presence of non-absorbing aerosols. The interaannual variations in UVAI reveal highest UVAI of 0.64 in December followed by 0.51 in July over South Asia. Seasonally, UVAI shows increasing trend at the rate of 0.9064 DJF⁻¹, 0.3810 JJA⁻¹, 0.2707 SON⁻¹ and 0.0774 MAM⁻¹ over South Asia. A positive correlation of 0.56 is observed between UVAI and wind speed followed by over Southern Pakistan followed 0.43 between UVAI and total ozone column Southern Pakistan and India. The UVAI shows increasing trend at the rate of 0.1409, 0.1124, 0.1224, 0.1015, 0.1242 and 0.2054 per year over Lahore, Karachi, Kanpur, New-Delhi, Varanasi, and Dhaka with maximum UVAI of 5.55, 4.47, 4.51, 4.99, 4.61 and 4.65 respectively during the study period. The anthropogenic productivity analysis reveals that primary industry and secondary industry contributes in lowering UVAI values whereas tertiary industry, energy consumption and gross domestic products increase aerosols loading in South Asia. Moreover, HYSPLIT cluster analysis further reveals the localized and trans-boundary sources of absorbing aerosols over the selected cities.