Remote sensing of ammonia point sources at high spatial resolution with satellite-based imaging spectrometers

Javier Roger, Adriana Valverde , Javier Gorroño, Zhipeng Pei , Itziar Irakulis-Loitxate, Luis Guanter

Ammonia (NH3) emissions play a key role in air pollution and the disruption of the nitrogen cycle. Global emissions of ammonia are expected to increase in the future, making their monitoring essential to better understand their impacts and to support effective environmental policies. Recent studies have demonstrated the potential of satellite imaging spectrometers operating in the shortwave infrared (SWIR) to identify ammonia point source emissions, mostly from fertilizer plants. In this work, we extend these observations to the current fleet of SWIR imaging spectrometers, including EMIT, EnMAP, PRISMA, GF-5A AHSI, and MethaneSat and provide a first systematic assessment of ammonia plume detection and quantification capabilities. We derive instrument-specific detection limits as a function of retrieval noise and wind speed, and obtain plume quantification models following the IME method, also accounting for a range of potential ammonia atmospheric lifetime values (1 h to 48 h). Under favorable conditions, we find detection thresholds of approximately 0.5 t/h and 0.8 t/h for EnMAP and EMIT, respectively. Using this framework, we present multiple ammonia plume detections from fertilizer plants and provide consistent emission estimates across different sensors. Finally, a 2.5-year time series over a fertilizer plant in Iraq demonstrates the potential of the current SWIR imaging spectrometer constellation to monitor ammonia point sources.