Estimation of surface ammonia concentrations and emissions in China from the polar-orbiting Infrared Atmospheric Sounding Interferometer and the FY-4A Geostationary Interferometric Infrared Sounder

Abstract. Ammonia (NH3) is the most important alkaline gas in the atmosphere, which has negative effects on biodiversity, ecosystems, soil acidification and human health. China has the largest NH3 emissions globally, mainly associated with agricultural sources including nitrogen fertilizer and livestock. However, there is still a limited number of ground monitoring sites in China, hindering our understanding of both surface NH3 concentrations and emissions. In this study, using the polar-orbiting satellite (Infrared Atmospheric Sounding Interferometer – IASI) and Fengyun-4A Geostationary Interferometric Infrared Sounder (GIIRS), we analyzed the changes in hourly NH3 concentrations and estimated surface NH3 concentrations and NH3 emissions in China. GIIRS-derived NH3 concentrations in the daytime were generally higher than those at night, with high values during 10:00–16:00 local time. Satellite-derived surface NH3 concentrations were generally consistent with the ground observations, with R-square at 0.72 and slope equal to 1.03. Satellite-based NH3 emissions ranged from 12.17 to 17.77 Tg N yr−1 during 2008–2019. Spatially, high values of NH3 emissions mainly occurred in the North China Plain, Northeast China and the Sichuan Basin, while low values were mainly distributed in West China (Qinghai–Tibet Plateau). Our study shows a high predictive power of using satellite data to estimate surface NH3 concentrations and NH3 emissions over multiple temporal and spatial scales, which provides an important reference for understanding NH3 changes over China.