A132-06
Global NOx emission reductions and tropospheric chemistry response linked to the world-wide COVID-19 lockdowns
Friday, 11 December 2020: 16:15
Virtual
Kazuyuki Miyazaki1, Kevin W Bowman2, Takashi Sekiya3, Masayuki Takigawa4, Henk Eskes5, Jessica L. Neu2, Vivienne Payne6 and Thomas Walker7, (1)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (2)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (3)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Research Institute for Global Change, Kanagawa, Japan, (4)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan, (5)Royal Netherlands Meteorological Institute, De Bilt, 3730, Netherlands, (6)NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (7)Carleton University, Department of Civil and Environmental Engineering, Ottawa, ON, Canada
Abstract:
The unprecedented steps taken to stop the transmission of COVID-19 had the ancillary effect of rapid emission reductions worldwide, which provided substantial changes in air pollutants such as ozone and aerosols as shown by various observations. We evaluated global NOx emission reductions and its impacts on global air quality and tropospheric chemistry, using a multi-constituent data assimilation of multiple satellite observations of TROPOMI and OMI NO2, OMI SO2, MOPITT CO, and MLS ozone and HNO3, in conjunction with the new satellite retrievals of tropospheric ozone and PAN from the CrIS satellites obtained through JPL’s TROPESS project. By combining with complementary information such as burned areas and decadal chemical reanalysis from MOMO-Chem, the relative roles of natural activity, such as biomass burning, and changes in anthropogenic emissions linked to the COVID-19 lockdowns were separately examined.
Corresponding to the lockdowns in numerous countries, the global total anthropogenic emissions were reduced by more than 20 % in April and May 2020, which is about twice larger than the reductions in February and March 2020 attributed primality to the Chinese lockdown. We find that ozone responses to the NOx emission reductions vary dynamically as a consequence of seasonal and regional variations in ozone production efficiency, providing substantial reductions in surface ozone especially over developing countries in the tropics with substantial influences from mega cities. Our chemical transport model simulations indicate that the free tropospheric ozone distribution is also modified, with up to 4 ppb reductions for monthly mean ozone widely in the northern hemisphere and downwind of megacities in the southern hemisphere such as over southern Atlantic in May 2020, which provides substantial constraints on the oxidation capacity. The decreased PAN concentrations both over polluted and remote areas revealed non-local impacts of the lockdown emission reductions through long-range transport of precursors. These results suggest strong impacts of the worldwide lockdowns on global tropospheric chemistry, climate radiative forcing, and human health.
