Changes in global air pollutant emissions during the COVID-19 pandemic: a dataset for atmospheric modeling
Authors: Doumbia Thierno , Granier Claire , Elguindi Nellie , Bouarar Idir , Darras Sabine , Brasseur Guy , Gaubert Benjamin , Liu Yiming , Shi Xiaoqin , Stavrakou Trissevgeni , Tilmes Simone , Lacey Forrest , Deroubaix Adrien , Wang Tao 
Published: August 2021

Abstract. In order to fight the spread of the global COVID-19 pandemic, most
of the world's countries have taken control measures such as lockdowns during
a few weeks to a few months. These lockdowns had significant impacts on
economic and personal activities in many countries. Several studies using
satellite and surface observations have reported important changes in the
spatial and temporal distributions of atmospheric pollutants and greenhouse
gases. Global and regional chemistry-transport model studies are being
performed in order to analyze the impact of these lockdowns on the
distribution of atmospheric compounds. These modeling studies aim at
evaluating the impact of the regional lockdowns at the global scale. In
order to provide input for the global and regional model simulations, a
dataset providing adjustment factors (AFs) that can easily be applied to
current global and regional emission inventories has been developed. This
dataset provides, for the January–August 2020 period, gridded AFs at a
0.1×0.1 latitude–longitude degree resolution on a daily or monthly basis
for the transportation (road, air and ship traffic), power generation,
industry and residential sectors. The quantification of AFs is based on
activity data collected from different databases and previously published
studies. A range of AFs are provided at each grid point for model sensitivity
studies. The emission AFs developed in this study are applied to the CAMS
global inventory (CAMS-GLOB-ANT_v4.2_R1.1),
and the changes in emissions of the main pollutants are discussed for
different regions of the world and the first 6 months of 2020. Maximum
decreases in the total emissions are found in February in eastern China,
with an average reduction of 20 %–30 % in NOx, NMVOCs (non-methane volatile organic compounds) and SO2 relative
to the reference emissions. In the other regions, the maximum changes occur
in April, with average reductions of 20 %–30 % for NOx, NMVOCs and CO in
Europe and North America and larger decreases (30 %–50 %) in South America.
In India and African regions, NOx and NMVOC emissions are reduced on
average by 15 %–30 %. For the other species, the maximum reductions are
generally less than 15 %, except in South America, where large decreases
in CO and BC (black carbon) are estimated. As discussed in the paper, reductions vary
highly across regions and sectors due to the differences in the duration of
the lockdowns before partial or complete recovery. The dataset providing a range of AFs (average and average ± standard
deviation) is called CONFORM (COvid-19 adjustmeNt Factors fOR eMissions)
(https://doi.org/10.25326/88; Doumbia et al., 2020). It is distributed by the
Emissions of atmospheric Compounds and Compilation of Ancillary Data (ECCAD)
database (https://eccad.aeris-data.fr/, last access: 23 August 2021).