Observing the Ammonia Daily Cycle over Agricultural Areas in Asia Using Combined Satellite Measurements

Ammonia (NH₃) is one of the most important nitrogen gas species and pollutants in the lower troposphere because of the wide usage of nitrogen-based fertilisers in agriculture. Most of the ammonia present in the atmosphere originates from anthropogenic sources, agriculture being the dominant one [1]. Ammonia enters the atmosphere through volatilisation from agricultural soils where fertilisers and/or manure have been spread [2]. Ammonia is a highly unstable gas, reacting chemically with acids to form fine particulate matter (PM_2.5), therefore playing an important role in secondary aerosol formation [3]. Wet and dry deposition of ammonia on soils and water bodies is detrimental to ecosystem biodiversity as it leads to acidification of the environment [4]. Therefore, observations of ammonia are essential for establishing air quality and environmental regulations for agricultural practices.

The remote sensing of ammonia presents numerous challenges because ammonia concentrations rapidly change over time and space due to the short life-time of the gas, which ranges from a few hours up to a day [5]. Studying the ammonia diurnal cycle provides valuable information on its sources, surface exchange, deposition and transport processes, and the impact on these by weather and surface conditions; all these are crucial for improving atmospheric models.

The ammonia daily cycle over the Indo-Gangetic Plain in India has been studied using combined satellite observations from the Infrared Atmospheric Sounding Interferometer (IASI) and the Cross-track Infrared Sounder (CrIS) instruments during different months in 2022. By studying the evolution of the ammonia total column concentrations at different satellite overpass times over several days, changes in the ammonia daily cycle can be observed between different seasons. The study makes use of optimal estimation-based retrieval methods developed at the University of Leicester.

 

References:

[1] Clarisse L. et al (2009), Nature Geoscience, 479-483

[2] Van Damme M. et al (2021), Environ. Res. Lett., 16 055017

[3] Erisman, J. W. et al (2007), Environ. Pollut., 150, 140– 149

[4] Krupa S. V. et al (2003), Environ. Pollut., 124, 179-221 

[5] Dammers E. et al (2019), Atmos. Chem. Phys., 12261–12293