Study of the aerosol parameters and radiative forcing during COVID-19 pandemic over Srinagar Garhwal, Uttarakhand

The present study was done at Hemvati Nandan Bahuguna (H.N.B.) Garhwal University, Srinagar (78°46′56″E, 30°13′7″N, 540 MSL) using automatic weather station and satellite-derived aerosol products. To understand aerosol loading, the space borne radiometer (Moderate-Resolution Imaging Spectroradiometer), onboard of aqua and terra satellite to retrieved aerosol optical depth (AOD), Angstrom exponent, and single scattering albedo (SSA) have been analyzed. The global COVID-19 pandemic has forced to the implication of nationwide lockdown, the AOD level decreased by 32% in the first week of lockdown (March 24 to March 31, 2020) as well as 30.1% in the first phase of lockdown (March 24 to April 14, 2020). The AOD levels in April, May, June, and July of year 2020 drastically reduced by 15.30%, 15.77%, 8.39%, and 41.74%, respectively, as compared to the similar months of 2019. Whereas, the higher AOD values were observed only in the June and July of 2019 and 2020 due to the transportation of aerosols (based on the NOAA HYSPLIT model) from Thar and Sahara desert as well as local emissions. But, a further decrease in AOD was may be due to the precipitation/washout of aerosols from the atmosphere during August and September of 2019. The change in the SSA was in the range of 1%–10% as well as Angstrom exponent (α) showed the variation in the range of 0.74–1.8 and 0.95–1.8 in the year 2019 and 2020 due to the presence of a different type of atmospheric aerosols.