Land use change and meteorology effect on atmospheric ammonia as seen by IASI

Agriculture contributes to air pollution and is affected by atmospheric composition, meteorology and climate change. One of the important gases emitted from agricultural activities is ammonia (NH₃), which makes up a large portion of the anthropogenic reactive nitrogen in the environment. Agricultural ammonia emissions contribute to the formation of inorganic fine particulate matter (PM_2.5), causing multiple negative effects on human health and the overall air quality. Many studies proved the capability of the Infrared Atmospheric Sounding Interferometer (IASI) instrument aboard the Metop satellites in measuring ammonia from space. The series of 3 instruments provides a continuous view of the global atmosphere since 2006, allowing us to study NH₃ and many other pollutants relevant to air quality.

In this presentation, we explore the interaction between atmospheric ammonia on the one hand, and land and meteorological conditions on the other hand. To start, IASI NH₃ total columns and ERA5 land surface temperatures are used to estimate the NH₃ emission potential from the soil in agricultural fields. In addition to temperature, the emission potential is affected by the soil physical properties, fertilizer application practices and the concentrations of NH₃ near the surface. The results are used to validate the emission potential of NH₃ as derived from chemistry transport model (CTM) simulations.

Then, we look at the spatio-temporal variability of ammonia, focusing on different source regions around the globe. The NH₃ land-atmosphere exchanges depend on land cover and land use management, and on meteorology. We study this relationship in two test regions and periods: an agricultural region in Syria that was subject to land use change during the conflict, and over agricultural regions around safe megacities.

In Syria we show that the detected changes in NH₃ concentrations is driven by land use/cover rather than meteorology.

Over megacities, in particular, Paris, Toronto and Mexico, the result is quite different. We show that the NH₃ variability is mainly driven by meteorology, and interestingly, we can detect the fertilizers application period by looking at the NH₃ – temperature relationship.