Dynamic modeling of ammonia emissions and nitrogen deposition via online coupling of WRF-Chem and Noah-MP-CN

Ammonia, a common harmful gas emitted from agricultural croplands, plays a crucial role in global nitrogen cycles through NH3 volatilization. Previous studies have often regarded NH3 emission as a static process in air quality modeling, relying on emission inventories with limited spatial and temporal resolutions, thus failing to investigate the complete terrestrial and atmospheric nitrogen cycle. We integrated the land surface and chemistry modules into the regional climate model WRF. Leveraging the nitrogen dynamics module (Noah-MP-CN), our novel emission strategy enables a more accurate representation of annual variations in NH3 emission fluxes, including the dynamic deposition of reduced nitrogen (NH3 and NH+ 4) onto the land surface. Additionally, we assessed the effects of nitrogen deposition on vegetation growth, revealing a 2.25 TgC yr-1 reduction in net primary productivity in the absence of nitrogen deposition.