This Postdoctoral Research Fellowship (PRF) research focuses on the trends and impacts of agricultural releases of reactive nitrogen to the atmosphere. A scheme will be developed to assess reactive nitrogen emissions that account for transport and chemistry including pollutant lifetime as well as cross-information from all observed reactive nitrogen species. While reactive nitrogen is necessary for plant growth, its use leads to emissions of reactive nitrogen species with implications for radiative forcing and air quality. The objectives of the project are to: (1) Exploit satellite and surface observations of nitrous oxide (N2O), ammonia (NH3), and nitrogen oxides (NOx) to jointly constrain global reactive nitrogen (Nr) emissions from agriculture over the past decade (2015-2024); (2) Assess the drivers (e.g. meteorology, economics) which best explain the inferred emissions trends and determine where and why 2015-2024 emissions trends diverge from the agricultural emissions projected by various forecasts of Nr; and (3) Simulate the air quality (fine particulate matter and ozone) and the radiative impacts of future Nr emissions scenarios, assuming a variety of agricultural intervention strategies and their interactions with fuel decarbonization pathways. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.