A roadmap to estimating agriculturalammonia volatilization over Europe usingsatellite observations and simulation data

International audience Ammonia (NH3) is one of the most important gases emitted from agricultural practices. It affects airquality and the overall climate and is in turn influenced by long-term climate trends as well as by short-termfluctuations in local and regional meteorology. Previous studies have established the capability of the InfraredAtmospheric Sounding Interferometer (IASI) series of instruments, aboard the Metop satellites, to measure am-monia from space since 2007. In this study, we explore the interactions between atmospheric ammonia, land andmeteorological variability, and long-term climate trends in Europe. We investigate the emission potential (0soil)of ammonia from the soil, which describes the soil–atmosphere ammonia exchange. 0soil is generally calcu-lated in-field or in laboratory experiments; here, and for the first time, we investigate a method which assesses itremotely using satellite data, reanalysis data products, and model simulations.We focus on ammonia emission potential in March 2011, which marks the start of growing season in Europe.Our results show that 0soil ranges from 2 × 103 to 9.5 × 104 (dimensionless) in fertilized cropland, such as inthe North European Plain, and is of the order of 10–102 in a non-fertilized soil (e.g., forest and grassland). Theseresults agree with in-field measurements from the literature, suggesting that our method can be used in otherseasons and regions in the world. However, some improvements are needed in the determination of mass transfercoefficient k (m s−1), which is a crucial parameter to derive 0soil.Using a climate model, we estimate the expected increase in ammonia columns by the end of the centurybased on the increase in skin temperature (Tskin), under two different climate scenarios. Ammonia columns areprojected to increase by up to 50 %, particularly in eastern Europe, under the SSP2-4.5 scenario and mighteven double (increase of 100 %) under the SSP5-8.5 scenario. The increase in skin temperature is responsiblefor a formation of new hotspots of ammonia in Belarus, Ukraine, Hungary, Moldova, parts of Romania, andSwitzerland.