Impact of CrIS-Derived NH ₃ Emission Updates on Simulated Nitrate and Ammonium Aerosols over East Asia

Fine particulate matter (PM₁ diameter <1 μm) strongly affects air quality and health, with sulfate, nitrate, and ammonium (SNA) as major components across East Asia. Because NH₃ is a key precursor of SNA formation, accurate NH₃ emission data are essential for reliable SNA simulations. This study improves NH₃ emission inventories in East Asia by integrating the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and the Cross-Track Infrared Sounder (CrIS), with extensive evaluation against ground-based and aircraft observations from the Korea-United States Air Quality (KORUS-AQ) campaign. Iterative linear inversion of NH₃ emissions using WRF-Chem markedly enhances simulations of nitrate and ammonium, in agreement with both the aircraft and surface measurements. The absolute biases of nitrate and ammonium were reduced from 89.7 and 50.1% to 13.6 and 0.6%, respectively, compared to the aircraft observations over Seoul. However, uncertainties in nocturnal NH₃ emissions remain potential sources of nighttime biases in nitrate and ammonium. Overall, the results indicate that nitrate aerosol in most of East Asia is sensitive to NH₃ emission changes. To advance our understanding of SNA formation and support effective aerosol mitigation policies, improved characterization of the diurnal cycle of NH₃ emissions through ground-based monitoring and high-resolution geostationary satellite observations is urgently needed.