Improved assimilated inversion of NOx emissions using OMI and GOME2 measurements over China

We improved the assimilated daily inversion of NO_x emissions by updating the a priori NO_x profiles used in the satellite retrieval using that from the daily assimilated NO_x inversion process. The improved procedure implemented with a regional chemical transport model (REAM) was applied to OMI and GOME2 NO₂ measurements in 2011, respectively. The inversion results were compared with the daily assimilated inversions using KNMI OMI and GOME2 tropospheric NO₂ column products. The retrieval results with a priori inversion update estimate an average NO_x emission of 6.9 Tg N/yr over China and the difference between using OMI and GOME2 measurements is only 0.4 Tg N/yr. In comparison, the difference between the assimilated inversion results using KNMI tropospheric NO₂ column products is significantly larger at 1.3 Tg N/yr. The relative difference is reduced from 30% to 7% when a priori NO_x profiles are updated during the daily inversion process. The more consistent NO_x emission inversion results are applied to examine the seasonal and weekday-weekend anthropogenic NO_x emission changes over China.