Spaceborne Measurements of Formic and Acetic Acid: A Global View of the Regional Sources

Formic (HCOOH) and acetic (CH3COOH) acids are the most abundant carboxylic acids in the Earth’s atmosphere and contribute to the acidity of rainwater and cloud. Current knowledge is however unable to explain their elevated concentration levels measured in the atmosphere since their sources remain poorly known and quantified. The first measurements of acetic acid atmospheric abundance have recently been obtained from space by the Infrared Atmospheric Sounding Interferometer (IASI) satellite instrument (Franco et al., 2020). These measurements allow the production of global maps, which reveal that formic and acetic acids exhibit similar abundance, distributions and seasonality, pointing to major common sources. Furthermore, their atmospheric abundance appear to be closely linked to the hydrocarbon emissions from the terrestrial vegetation as well as to the presence of wildfires, especially in the tropics. Over Africa, evidence is provided that residual smoldering combustion related to wildfires might be a major driver of the formic and acetic acid seasonality. In some regions, differences between these two compounds suggest that sources and production pathways specific to each species are also at play.

Top panel: Means (on a 0.5° × 0.5° grid) of the HCOOH and CH3COOH total columns from the 2007–2018 IASI/Metop–A observations over October. Middle panel: Correlation coefficients between the daily 0.5° × 0.5° gridded HCOOH and CH3COOH total columns and (d) CH3COOH:HCOOH column ratios, over October throughout the 2007–2018 time period. Bottom panel: Time series of monthly mean HCOOH and CH 3 COOH total column (blue and purple solid lines, respectively, MEGAN–MOHYCAN isoprene and monoterpenes emission fluxes (green dotted line) and cumulative MODIS FRP (orange dotted line) over areas of interest. (Franco et al., 2020)

More news


Homogeneous temperature data record derived from 13 years of IASI data using an artificial neural network

Bouillon et al. (2022) recently designed a neural network to retrieve atmospheric temperatures from the IASI radiance data. This new temperature data record is validated against other datasets and a good agreement is shown. Trends were computed from this new temperature dataset over the 2008–2020 period. A general warming of the troposphere, more important at […]



Humidity levels to determine future liveability in the Arabian Peninsula

Human survivability in hot regions does not depend only on temperature, but also on humidity levels in ambient air. In fact, the body’s ability to shed heat is diminished when the air around it is saturated with humidity. The wet bulb temperature (also called heat stress) is the temperature of the air when it is […]



Trends in spectrally resolved outgoing longwave radiation from 10 years of satellite measurements

By analyzing the changes in the spectrally resolved Earth’s Outgoing Longwave Radiation (OLR) from 10 years of daily IASI observations, Whitburn et al. (2021) have highlighted the impact of large climate phenomena (in particular El Niño) on the surface and atmospheric temperature and atmospheric composition. More interesting from a longer-term climate monitoring perspective, they were […]