Atmospheric Transport of Agricultural Nitrogen Emissions from Eastern Colorado into Rocky Mountain National Park

Upslope winds on the lee side the Rocky Mountains transport agricultural and urban nitrogen (N) into the Rocky Mountains. Increased agricultural N emissions from eastern Colorado have led to increased nitrogen deposition in Rocky Mountain National Park (RMNP) over the last three decades. In our study, we simulated the transport of a tracer that represented ammonia (NH₃) during three summer events where N deposition in RMNP was anomalously high. High-resolution simulations were performed to accurately capture the boundary layer processes and transport of the simulated tracer over complex topography. We found emissions are transported by the combination of small-scale (e.g. cloud-scale) and large-scale (e.g. synoptic circulation) processes. We then leveraged the knowledge of the transport processes surrounding high deposition events and co-developed a pilot early warning system (PEWS) that would alert agricultural producers during times when emissions from their operations would advect westward towards the Rocky Mountains. Over 60 agricultural producers from the largest agricultural operations in Colorado registered to receive alerts for the PEWS. Subsequently, the producers voluntarily enacted or halted activities that minimize NH₃ emissions from their operations. Between April 2014 and December 2016, 76 of the 1005 days (or 7.5% of all days) had warnings. In this presentation, we will discuss the meteorology that precedes and occurs during high N deposition events in RMNP, methods for the operational PEWS, and results and statistics from the PEWS for three years of operation.