Ammonia (NH₃) and nitrogen oxides (NO_x: nitrogen dioxide [NO₂] + nitric oxide [NO]) play important roles in atmospheric chemistry. Throughout most of Africa, emissions of these gases are predominantly from soils and biomass burning. Here we use observations of tropospheric NO₂ vertical column densities (VCDs) from the Ozone Monitoring Instrument from 2005 through 2017 and atmospheric NH₃ VCDs from the Infrared Atmospheric Sounding Interferometer from 2008 through 2017 to evaluate seasonal variation of NO₂ and NH₃ VCDs across Africa and in seven African ecoregions. In regions where mean annual precipitation (MAP) is under 500 mm yr⁻¹, we find that NO₂ and NH₃ VCDs are positively related to monthly precipitation, and where MAP is between 500 and 1,750 mm yr⁻¹ or higher, NO₂ VCDs are negatively related to monthly precipitation. In dry ecoregions, temperature and precipitation were important predictors of NH₃ and NO₂ VCDs, likely related to variation in soil emissions. In mesic ecoregions, monthly NO₂ VCDs were strongly related to burned area, suggesting that biomass burning drives seasonality. NH₃ VCDs in mesic ecoregions were positively related to both monthly temperature and monthly carbon monoxide (CO) VCDs, suggesting that a mixture of soil and biomass burning emissions influenced NH₃ seasonality. In northern mesic ecoregions, monthly temperature explained most of the variance in monthly NH₃ VCDs, suggesting that soil sources, including animal excreta, determined NH₃ seasonality. In southern mesic ecoregions, monthly CO VCDs explained more variation in NH₃ VCDs than temperature, suggesting that biomass burning may have greater influence over NH₃ seasonality.

中文翻译：

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卫星观测揭示了非洲大气 NO2 和 NH3 季节性的大陆和生态区特定驱动因素

氨 (NH ₃ ) 和氮氧化物（NO _x：二氧化氮 [NO ₂ ] + 一氧化氮 [NO]）在大气化学中起着重要作用。在非洲大部分地区，这些气体的排放主要来自土壤和生物质燃烧。在这里，我们使用2005 年至 2017 年臭氧监测仪器的对流层 NO ₂垂直柱密度 (VCD) 和2008 年至 2017 年红外大气探测干涉仪的大气 NH ₃ VCD 的观测值来评估 NO ₂和 NH ₃ VCD 的季节性变化。非洲和七个非洲生态区。在年平均降水量 (MAP) 低于 500 mm yr ^{-1 的地区}，我们发现NO ₂和NH ₃ VCDs 与月降水量呈正相关，当MAP 在500 到1,750 mm yr ^-1或更高时，NO ₂ VCDs 与月降水量呈负相关。在干旱生态区，温度和降水是 NH ₃和 NO ₂ VCD 的重要预测因子，可能与土壤排放的变化有关。在中生态区，每月 NO ₂ VCD 与燃烧面积密切相关，表明生物质燃烧驱动季节性。NH ₃中等生态区中的 VCD 与每月温度和每月一氧化碳 (CO) VCD 呈正相关，表明土壤和生物质燃烧排放的混合物影响了 NH ₃季节性。在北部中等生态区，月度温度解释了月度 NH ₃ VCD 的大部分变化，这表明土壤来源，包括动物排泄物，决定了 NH ₃季节性。在南部中等生态区，每月的 CO VCD比温度解释了更多的 NH ₃ VCD 变化，这表明生物质燃烧可能对 NH ₃季节性有更大的影响。