A Better Tropospheric Aerosol Analysis and Forecast Using Data Assimilation and Coupled Modeling



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Chemical transport models are useful to predict air pollutant concentrations and provide advice to people to minimize adverse impacts of high levels of tropospheric aerosols and ozone. This dissertation incorporated a coupled model between meteorology and air quality, as well as data assimilation techniques to get more complexity and reliability of chemical transport models. In the first chapter, we assimilated the GOCI AOD into the WRF-CMAQ two-way coupled model over East Asia during the KORUS-AQ period. Improvement of modeling performance on aerosol simulations enabled us to accurately quantify the impact of direct effects of aerosols. Stabilized atmospheric conditions increased most of the gaseous and aerosol pollutants at the surface by 7.87 – 34%. In the second chapter, we showed that the direct effects of aerosols enhanced the strength of the radiation sea fog over the Yellow Sea due to lower temperatures. We found dominant changes in inorganic aerosols at an altitude of 150 m through the aqueous-phase chemistry (~12.36% and ~3.08% increases for sulfate and ammonium) and loss via the wet deposition process (~-3.79% decrease for nitrate).
In the third chapter, to estimate top-down NOx emissions over East Asia, we applied an inverse modeling technique with tropospheric NO2 column from TROPOMI in the spring of 2019. We found a substantial contribution of the transported air pollutants on local NOx (22.96 – 35.24%) and O3 (24.23 – 42.26%) budgets. The enhanced chemical loss of NOx compensated for increases by transport, as well as the increased vertical gradient of MDA8 O3 amplified vertical transport and dry deposition processes. In the last chapter, to examine changes in the O3 chemical production regime over the CONUS in the summers of 2011, 2014, and 2017, top-down emissions of NOx and NMVOCs were estimated by using tropospheric NO2 and total HCHO columns from OMI. The inversion suggested 2.33 – 2.84 times higher NOx over the CONUS and 0.28 – 0.81 times fewer NMVOC emissions over the southeastern U.S. We found major metropolitan areas shifted toward NOx-limited conditions. However, meteorological changes caused a significant reduction in the HCHO column over the southeastern U.S, thus the region becoming sensitive to VOC emissions.



data assimilation, air quality forecasting


Portions of this document appear in: Jung J., Souri AH., Wong DC., Lee S., Jeon W., Kim J. and Choi Y., 2019, The impact of the direct effect of aerosols on meteorology and air quality using aerosol optical depth assimilation during the KORUS-AQ campaign, Journal of Geophysical Research: Atmosphere, 124(14) (http://doi.org/10.1029/2019JD030641); and in: Jung J, Choi Y., Wong DC., Nelson D., and Lee S., 2020, Role of sea fog over the Yellow Sea on air quality with the direct effect of aerosols, Journal of Geophysical Research: Atmosphere, 126 (https://doi.org/10.1029/2020JD033498)