Recent studies demonstrated the difficulties to explain observed tropospheric nitrogen dioxide (NO _2 ) variabilities over the United States and Europe, but thorough analysis for the impacts on tropospheric NO _2 in China is still lacking.Here we provide a comparative analysis for the observed and modeled (Goddard Earth Observing System-Chem) tropospheric NO _2 in early 2020 in China.Both ozone monitoring instrument and surface NO _2 measurements show marked decreases in NO _2 abundances due to the 2019 novel coronavirus (COVID-19) controls.However, we find a large discrepancy between observed and modeled NO _2 changes over highly polluted provinces: the observed reductions in tropospheric NO _2 columns Colon Care / Cleansing are about 40% lower than those in surface NO _2 concentrations.By contrast, the modeled reductions in tropospheric NO _2 columns are about two times higher than those in surface NO _2 concentrations.
This discrepancy could be driven by the combined effects from uncertainties in simulations and observations, associated with possible inaccurate simulations of lower tropospheric NO _2 , larger uncertainties in the modeled interannual variabilities of NO _2 columns, as well as insufficient consideration of Vacuum Sealer Bags aerosol effects and a priori NO _2 variability in satellite retrievals.In addition, our analysis suggests a small influence from free tropospheric NO _2 backgrounds in E.China in winter.This work demonstrates the challenge to interpret wintertime tropospheric NO _2 changes in China, highlighting the importance of integrating surface NO _2 observations to provide better analysis for NO _2 variabilities.