Impact of COVID-19 Lockdown and Australian Bushfires on Aerosol Loading over the Downwind Coastal Oceanic Regions

Abstract:

Nearly 40-years aerosol optical thickness (AOT) climate data record (CDR) from AVHRR satellite observation over the global ocean was used to study the impact of COVID-19 lockdown and Australian bushfires on aerosol loading over the downwind coastal oceanic regions since recent similar impact studies are mainly focused in the land areas near the emission sources. AOT was used as the proxy of aerosol loading in our study. We found out AOT variations due to the emission reduction during the lockdown period are complex and non-linear. AOT reduction was observed due to the emission reduction during the stringent lockdown period of China. However, unexpected surge of AOT also occurred over the coastal oceans of India during the tighten lockdown period. Moreover, inter-annual variations of AOT may also mask the AOT changes over the east coastal ocean of USA and the Mediterranean Sea during relatively relaxed lockdown. By a contrast, AOT was increased in a monotonic way due to the burning emissions of severe Australian bushfires in 2019/2020 fire season. The AOT surge was not only over the Australia coastal ocean but also extended to over the entire southern ocean. This comparative study for the two opposite extreme emission scenarios in natural condition is benefit for seeking the effective mitigation strategy of anthropogenic emissions.