The Diel Cycle of NH3 Observed From the FY‐4A Geostationary Interferometric Infrared Sounder (GIIRS). Issue 14 (17th July 2021)

• Record Type: Journal Article
• Authors: Clarisse, Lieven; Van Damme, Martin; Hurtmans, Daniel; Franco, Bruno; Clerbaux, Cathy; Coheur, Pierre‐François
• Is Part Of: Geophysical research letters. Volume 48:Issue 14(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-07-17
• Subjects: ammonia -- GIIRS -- diurnal -- nocturnal -- diel -- atmosphere; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL093010
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Limiting excess atmospheric ammonia (NH3 ) is one of the great challenges for humanity in the 21st century but can only be achieved with adequate monitoring means in place. Here, we report the first NH3 measurements from the Geostationary Interferometric Infrared Sounder (GIIRS) onboard the Chinese FY‐4A satellite. The instrument scans almost all of Asia 10 times per day. We show that GIIRS′ unprecedented temporal sampling can be exploited to measure diurnal and nocturnal variations of NH3 and demonstrate this on two case studies over Punjab and the North China Plain. Day–night variations are found to be almost absent in winter, but can reach a factor 2–3 in the warmer months. These case studies are very promising given the future landscape of geostationary sounders, but also show that improved knowledge on lower tropospheric air temperatures and the vertical profile of NH3 is key to better exploit their measurements. Plain Language Summary: To reduce the worldwide concentrations of ammonia (NH3 ) in the air is one of the great challenges for humanity in the 21st century, but this can only be achieved with stringent policies in place, and with the support of accurate and frequent measurements. In this paper, we report the first ammonia measurements from the Geostationary Interferometric Infrared Sounder (GIIRS) onboard the Chinese FY‐4A satellite. The satellite is positioned above Indonesia and measures almost all of Asia 10 times per day. We show that GIIRS' measurements can be used to measure ammonia both during day and night. We look into more detail at two locations, over Punjab (Pakistan) and the North China Plain. Day‐night variations are found to be almost absent in the colder months, but can reach a factor 2–3 in the warmer months. These case studies are very promising given the future landscape of geostationary sounders, but demonstrate also that improved knowledge on the air temperature at the surface and the behavior of ammonia at higher altitudes will result in more accurate ammonia measurements. Key Points: We report the first observations of atmospheric NH3 from the geostationary satellite FY‐4A GIIRS over Asia The potential of GIIRS to reveal the diurnal and nocturnal variations of NH3 total columns is demonstrated over two sites To better exploit geostationary data, improved temperature profiles and knowledge on the vertical NH3 distribution is needed