EVALUATING THE INFLUENCE OF SATELLITE OBSERVATION ON INVERSING NO<sub>X</sub> EMISSION AT REGIONAL SCALE
In order to explore the influence of satellite observation data on the top-down NOx estimates at regional scale, the top-down NOx emissions for Yangtze River Delta (YRD) region at 9 km spatial resolution were developed with Peking University Ozone Monitoring Instrument NO2 product (POMINO) v1 and POMINO v2 satellite observation data in January and July of 2016. The differences of top-down NOx estimates derived from the two satellites were quantitative evaluated, and the reasons were comprehensively analyzed. The total NOx emissions based on POMINO v2 in January and July was 27% and 45% higher than those derived with POMINO v1, respectively. It indicated that the difference of top-down estimate derived from different satellite observation in summer was larger than that in winter. Considering that the difference between the two observations in January was similar to that in July, it was mainly because that the sensitivity of NO2 concentration to emissions was larger in summer than in winter. Top-down estimates derived from the two satellite observation were evaluated with air quality model (AQM) and ground observation. The model performances derived from top-down NOx emission based on POMINO v1 were better than those based on POMINO v2. The probable reason was that the NO2 vertical column densities (VCD) in POMINO v1 was closer to available ground-based MAX-DOAS observations during cloudless days and the satellite observation of cloudless was usually selected to inversing NOx emission.