A Satellite-based Assessment of Long-term Trends in Extreme Smog and Haze and Their Radiative Impacts over the Indo-Gangetic Plains

Atmospheric pollution over the Indo-Gangetic Plain (IGP) has attracted wide attention due to its strong impacts on air quality, radiative forcing and climate implications. These impacts are potentially growing due to rising trends of anthropogenic aerosols emissions. Intense episodes of crop residue burning, smog and haze are increasingly observed in recent years over the IGP during post-monsoon and winter seasons, respectively. This study presents a satellite-based trend assessment of aerosol loading and radiative fluxes from Moderate Resolution and Imaging Spectroradiometer (MODIS) and Cloud and Earth's Radiant Energy System (CERES) observations since early 2000s. The results depict a large sustained increasing trend in aerosol optical depth (AOD) during the post-monsoon crop burning season, during the last two decades. Smoke transport and the build-up of smog from crop burning in northwestern India is persistently observed in the enhancement of AOD throughout the IGP. On the other hand, haze events during winter months are consistently observed with high AOD exceedances, largely concentrated over the eastern IGP. The increasing trend of aerosol loading and corresponding decadal changes in top-of-atmosphere (TOA) and surface radiative fluxes over IGP are quantified using satellite measurements. Furthermore, aerosol-induced changes in radiative fluxes indicate a characteristic increase in surface cooling and waring of lower troposphere over the IGP. Overall, the present study quantifies long-term changes in aerosol loading and its radiative implications over the IGP linked to crop burning and extreme winter haze events.