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

Nitrogen oxides (NO_x) 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 NO_x 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.