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NH 3  is an important part of the global nitrogen cycle as the most important atmospheric alkaline gas. NH 3  reacts rapidly with acidic substances and accelerates the generation of particulate matter (PM 2.5 ), which has important effects on the atmosphere and climate change. In this study, satellite NH 3  column data were used to analyze spatial and temporal distributions of NH 3  in China, and because of high concentrations and rates of change, North China was selected for more detailed analysis. Qualitative analysis was conducted to understand the relations between concentrations of NH 3  and those of SO 2  and NO 2 . Last, the random forest method was used to quantify relations between concentrations of atmospheric NH 3  and factors influencing those concentrations, such as meteorological factors, NH 3  self-emission, and concentrations of SO 2  and NO 2 . Satellite-retrieved NH 3  column concentrations showed an increasing trend during the 11 years from 2008 to 2018, and the rate of increase in summer was faster than that in winter. In those 11 years, NH 3  self-emission had the greatest influence on NH 3  concentrations. Concentrations of SO 2  and NO 2  had some effect and were negatively correlated with NH 3  concentrations. The effect of SO 2  on NH 3  concentration was greater than that of NO 2 . Atmospheric NH 3  concentration was also affected by meteorological conditions (temperature, relative humidity, pressure, and wind). In summer, temperature is the most important factors of meteorological conditions and relative humidity is the most important factors in winter. Therefore, to better control atmospheric NH 3  concentrations, it is particularly important to formulate practical NH 3  emission reduction policies and to consider the effects of SO 2  and NO 2  emission reduction policies.

Satellite-Based Analysis of Spatial–Temporal Distributions of NH3 and Factors of Influence in North China