ALBERT

Description: Ammonia (NH3), as an alkaline gas in the atmosphere, can cause direct or indirect effects on the air quality, soil acidification, climate change and human health. Estimating surface NH3 concentrations is critically important for modeling the dry deposition of NH3 and for modeling the formation of ammonium nitrate, which have important impacts on the natural environment. However, sparse monitoring sites make it challenging and difficult to understand the global distribution of surface NH3 concentrations in both time and space. We estimated the global surface NH3 concentrations for the years of 2008–2016 using satellite NH3 retrievals combining vertical profiles from GEOS-Chem. The accuracy assessment indicates that the satellite-based approach has achieved a high predictive power for annual surface NH3 concentrations compared with the measurements of all sites in China, the US and Europe (R2=0.76 and RMSE = 1.50 µg N m−3). The satellite-derived surface NH3 concentrations had higher consistency with the ground-based measurements in China (R2=0.71 and RMSE = 2.6 µg N m−3) than the US (R2=0.45 and RMSE = 0.76 µg N m−3) and Europe (R2=0.45 and RMSE = 0.86 µg N m−3) at a yearly scale. Annual surface NH3 concentrations higher than 6 µg N m−3 are mainly concentrated in the North China Plain of China and northern India, followed by 2–6 µg N m−3 mainly in southern and northeastern China, India, western Europe, and the eastern United States (US). High surface NH3 concentrations were found in the croplands in China, the US and Europe, and surface NH3 concentrations in the croplands in China were approximately double those in the croplands in the US and Europe. The linear trend analysis shows that an increase rate of surface NH3 concentrations (〉 0.2 µg N m−3 yr−1) appeared in eastern China during 2008–2016, and a middle increase rate (0.1–0.2 µg N m−3 yr−1) occurred in northern Xinjiang over China. NH3 increase was also found in agricultural regions in the central and eastern US with an annual increase rate of lower than 0.10 µg N m−3 yr−1. The satellite-derived surface NH3 concentrations help us to determine the NH3 pollution status in the areas without monitoring sites and to estimate the dry deposition of NH3 in the future.

Description: Ammonia (NH3), as an alkaline gas in the atmosphere, can cause direct or indirect effects on the air quality, soil acidification, climate change as well as human health. Estimating surface NH3 concentrations is critically important for modelling the dry deposition of NH3, which has important impacts on the natural environment. However, sparse monitoring sites make it challenging and difficult to understand the global distribution of surface NH3 concentrations both in time and space. We estimated the global surface NH3 concentrations for the years of 2008–2016 using the satellite NH3 observations combining its vertical profiles from the GEOS-Chem. The accuracy assessment indicates that the satellite-based approach has achieved a high predictive power for annual surface NH3 concentrations (R2 = 0.76 and RMSE = 1.50 μg N m-3). The satellite-derived surface NH3 concentrations had higher consistency with the ground-based measurements in China (R2 = 0.71 and RMSE = 2.6 μg N m-3) than the US (R2 = 0.45 and RMSE = 0.76 μg N m-3) and Europe (R2 = 0.45 and RMSE = 0.86 μg N m-3) at a yearly scale. Annual surface NH3 concentrations higher than 6 μg N m-3 are mainly concentrated in the North China Plain of China and Northern India, followed by 2–6 μg N m-3 mainly in southern and northeastern China, India, western Europe and eastern United States (US). High surface NH3 concentrations were found in the croplands in China, US and Europe, and surface NH3 concentrations in the croplands in China were approximately double than those in the croplands in the US and Europe. The liner trend analysis shows that a significant increase rate of surface NH3 concentrations (〉 0.2 μg N m-3 y-1) appeared in the eastern China during 2008–2016, and a middle increase rate (0.1–0.2 μg N m-3 y-1) occurred in northern Xinjiang over China. NH3 increase was also found in agricultural regions in middle and eastern US with an annual increase rate of lower than 0.10 μg N m-3 y-1. The satellite-derived surface NH3 concentrations help us to determine the NH3 pollution status in the areas without monitoring sites and to estimate the dry deposition of NH3 in the future.

Description: The effects of NOx and SO2 policies on acid species in precipitation was assessed in China from 2005 to 2016, based on the OMI measured SO2 and NO2 columns. The results showed that the SO2 and NO2 columns in the atmospheric boundary layer (ABL) could be used to indicate the variations of S / N in precipitations (R = 0.90, incept = 0.97, P