Global Wet‐Reduced Nitrogen Deposition Derived From Combining Satellite Measurements With Output From a Chemistry Transport Model

Wet‐reduced nitrogen (NH4+) 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 NH4+ deposition. Here we utilize NH3 measurements from satellite retrievals (Infrared Atmospheric Sounding Interferometer) to estimate global wet NH4+ 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 NH4+ concentration in precipitation and atmospheric NH3 columns using a global chemistry transport model (GEOS‐Chem). Satellite‐based wet NH4+ 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 NH4+ 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 NH4+ deposition using the satellite observations without depending on the ground‐based measurements for constructing the models. It is particularly helpful in estimating wet NH4+ deposition over regions with few monitoring sites. Our unique satellite‐derived wet NH4+ deposition can be applied for evaluating its impacts on ecosystems in the future. Key Points We present a novel approach for estimating wet‐reduced nitrogen deposition globally The proposed satellite‐based model shows better performance than the global atmospheric models The largest increase of wet reduced nitrogen deposition occurs in southern China, followed by northeastern India, North America, and Western Europe