Impacts of climate change and emissions on atmospheric oxidized nitrogen deposition over East Asia

A multi-model ensemble of Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) simulations is used to study the atmospheric oxidized nitrogen (NOy) deposition over East Asia under climate and emission changes projected for the future. Both dry and wet NOy deposition show significant decreases in the 2100s under RCP4.5 and RCP8.5, primarily due to large anthropogenic emission reduction over both land and sea. However, in the near future of the 2030s, both dry and wet NOy deposition increase significantly due to continued increase in emissions. Marine primary production from both dry and wet NOy deposition increases by 19 %-34% in the 2030s and decreases by 34 %-63% in the 2100s over the East China Sea. The individual effect of climate or emission changes on dry and wet NOy deposition is also investigated. The impact of climate change on dry NOy deposition is relatively minor, but the effect on wet deposition, primarily caused by changes in precipitation, is much higher. For example, over the East China Sea, wet NOy deposition increases significantly in summer due to climate change by the end of this century under RCP8.5, which may subsequently enhance marine primary production. Over the coastal seas of China, as the transport of NOy from land becomes weaker due to the decrease in anthropogenic emissions, the effect of ship emissions and lightning emissions becomes more important. On average, the seasonal mean contribution of ship emissions to total NOy deposition is projected to be enhanced by 24 %-48% and 3 %-37% over the Yellow Sea and East China Sea, respectively, by the end of this century. Therefore, continued control of both anthropogenic emissions over land and ship emissions may reduce NOy deposition to the Chinese coastal seas.