Global Wet‐Reduced Nitrogen Deposition Derived From Combining Satellite Measurements With Output From a Chemistry Transport Model
Lei Liu, Yuyu Yang, Ruipeng Xi, Xiuying Zhang, Wen Xu, Xuejun Liu, Yi Li, Pu Liu, Zhen Wang
Abstract
Abstract Wet‐reduced nitrogen (NH 4 + ) is the main component of atmospheric nitrogen (N) deposition. Due to the poor coverage of ground‐based measurements, it is still challenging to characterize the global wet‐reduced NH 4 + deposition. Here we utilize NH 3 measurements from satellite retrievals (Infrared Atmospheric Sounding Interferometer) to estimate global wet NH 4 + deposition at 0.1° grids for nine years (2008–2016). We achieve this by developing a novel approach by calculating the feedback ratio between wet NH 4 + concentration in precipitation and atmospheric NH 3 columns using a global chemistry transport model (GEOS‐Chem). Satellite‐based wet NH 4 + concentration and deposition is relatively highly correlated with the ground‐based measurements ( r = 0.88 and bias = 12% for wet deposition). The largest increase in the satellite‐derived wet NH 4 + deposition occurs in southern China (>0.5 kg N ha −1 yr −1 ), followed by northeastern India, North America, and Western Europe. The proposed method is simple, fast, and effective in estimating wet NH 4 + deposition using the satellite observations without depending on the ground‐based measurements for constructing the models. It is particularly helpful in estimating wet NH 4 + deposition over regions with few monitoring sites. Our unique satellite‐derived wet NH 4 + deposition can be applied for evaluating its impacts on ecosystems in the future.