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 due to emissions from biomass burning and
biogenic sources. FY-4B/GIIRS effectively tracks HCOOH enhancements from
wildfires and biogenic sources both during the day and at night.
Finally, cross-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 towards 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).