A tropospheric chemistry reanalysis for the years 2005-2014 based on an assimilation of OMI, MLS, TES and MOPITT satellite data

Abstract:

I will present the results from a ten-year tropospheric chemistry reanalysis for the period 2005–2014 obtained by assimilating multiple data sets from the OMI, MLS, TES, and MOPITT satellite instruments. The reanalysis calculation was conducted using a global CTM and an EnKF data assimilation approach that simultaneously optimises the chemical concentrations of various species and emissions of several precursors. The optimisation of both the multiple species concentration and the emission fields is an efficient method to correct the entire tropospheric profile and its year-to-year variations, and to adjust various tracers chemically linked to the species assimilated, while taking their feedbacks into account. Comparisons against independent aircraft, satellite, and ozonesonde observations demonstrate the quality of the analysed O₃, NO₂, and CO concentrations on regional and global scales and for both seasonal and year-to-year variations from the lower troposphere to the lower stratosphere. The northern/southern hemisphere OH ratio was modified considerably due to the multiple species assimilation and became closer to an observational estimate, which played an important role in propagating observational information among various chemical fields and affected the emission estimates. In comparison to the a priori emissions based on bottom-up inventories, the optimized surface NOx emissions were higher over eastern China, the eastern United States, southern Africa, and central-western Europe, suggesting that the anthropogenic emissions are mostly underestimated in the inventories. In addition, the seasonality and year-to-year variability of the estimated emissions differed from that of the a priori emission over both industrial and biomass burning areas. The assimilation of multiple chemical data sets with different vertical sensitivity profiles also provides comprehensive constraints on the global lightning NOx source while improving the representations of the entire chemical system affecting atmospheric NOx, including surface emissions and inflows from the stratosphere. The ten-year consistent concentration and emission products provide unique information on year-to-year variations of the atmospheric environment.