Observing a Volatile Organic Compound From a Geostationary Infrared Sounder: HCOOH From FengYun‐4B/GIIRS

Abstract Formic acid (HCOOH) is one of the most abundant volatile organic compounds (VOCs) in the Earth's atmosphere and an important source of atmospheric acidity. Here we present the first retrieval of HCOOH from a geostationary orbit using observations from the Geostationary Interferometric Infrared Sounder (GIIRS) on board FengYun‐4B. The results from July 2022 to June 2023 show the monthly variation of the HCOOH distribution in Asia. In addition, we show that FY‐4B/GIIRS effectively tracks HCOOH enhancements from wildfires both during the day and at night. Finally, inter‐comparison with IASI HCOOH data shows good agreement, indicating that FY‐4B/GIIRS observations have comparable sensitivity to IASI. This study is an important first step toward monitoring VOCs from geostationary infrared sounders, including the existing and future GIIRS on board the FY‐4 series and the forthcoming European geostationary infrared sounder (IRS) on board Meteosat Third Generation (MTG).