A large decline of tropospheric NO2 in China observed from space by SNPP OMPS.

Nitrogen oxides (NOx) are important constituents of air pollution. Here we use retrievals of tropospheric NO2 column from the Ozone Mapping Profiler Suite (OMPS) Nadir Mapper (NM) onboard the Suomi National Polar Partnership (SNPP) spacecraft to analyze global changes of NO2 from 2012 to 2017. The largest decline of NO2 is detected in eastern China, at a rate of -7.3 ± 1.5% per year, and almost entirely driven by wintertime decreases, indicative of decreasing anthropogenic NOx emissions. During the same period, NO2 over other regions around the globe was either stabilizing or changing at a rate only a fraction of that in China. In the case of the US, OMPS reports a statistically insignificant decreasing trend in NO2, consistent with recent work based on the Ozone Monitoring Instrument (OMI), which can be almost entirely attributed to meteorology. OMPS thus offers a continuation of satellite NO2 products from OMI to future JPSS satellites.