Climatology and Trends in Aerosol Optical Properties over Different Emission Regions in India

Climatological variations and trends in aerosol parameters were studied over six different regions identified as different source regions of aerosol emissions over India. Analysis was carried out on monthly mean satellite data for total aerosol optical depth (AOD), black carbon AOD (BC-AOD), single-scattering albedo (SSA) and Ångström exponent (ANG), in addition to NCEP reanalysis data for air temperature and relative humidity, for two decades (2000–2019) over the six different Indian regions. Through analysis of seasonal and annual climatology, it was found that region R3 (Indo-Gangetic Plain) was the most aerosol-laden area, as evidenced by a high value of BC-AOD and AOD. A high mean value of ANG indicated an increase in natural aerosol emissions over region R1 (Northeast India). Single-scattering albedo was highest in region R4 (South India). The aerosol changes over all regions showed a lower enhancing trend in total AOD and BC-AOD in the second decade (2010–2019) as compared with the first decade (2000–2009), which was attributed to the improvements in vehicle technology and use of more refined fuels in the domestic sector. The decreasing trend in Ångström exponent and AOD indicates that the anthropogenic aerosol loading decreased in the second decade relative to the first decade.