Dominance of Natural Aerosols Over India In Pre-Monsoon: Inferences From the Lockdown Effects

Changes in absorbing and composite aerosols over India during the first phase of lockdown are examined, using multi-satellite observations. While MODIS shows –16.17  1.35% reduction in AOD over the Indian landmass, OMI shows a decrease of –22.4  1.36% (–26.2  1.17%) in AOD (AAOD). Considerable fraction of this AOD difference is contributed by the changes in aerosols at higher altitudes. While reduc-tion in AOD of –38.05  1.06% (–39.4  1.12), –23.02  2.63% (–17.08  2.12) and –18.98  2.86% (–28.38  2.39%) is observed over IGP, Northwest and Southern Peninsula respectively from MODIS (OMI), enhance-ment in AOD of 5.16  2.44% (6.82  2.86%) is seen over Centralwest India. Reduction in absorbing aero-sols over IGP is –39.18  1.25%, whereas that over Southern Peninsula is –33.1  2.03%. These changes are significantly contributed by the changes in dust aerosols, in addition to the decrease in anthropogenic aerosols. Though there is a reduction in aerosol load-ing, compared to previous years, gradual increase in AOD and AAOD is seen even during the lockdown period due to strengthening of dust transport. More-over, the reduction in total (absorbing) aerosol load-ing over India during the lockdown phase is only 20% (26%), with significant contribution from higher alti-tudes, even in the absence of major anthropogenic sources. These results show the dominance of natural aerosols over India during pre-monsoon.