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

Ethylene industrial emitters seen from space

Over the past decade, significant progress has been made in improving the monitoring of the Earth’s atmosphere and our understanding of the impact that human activities have on air pollution. IASI/Metop is one of these satellite instruments capable of mapping the chemical composition of the atmosphere globally and in near-real time. In a recent study, […]

How did ozone pollution evolve during the COVID-19 lockdown of spring 2020? 

In the boreal spring of 2020, worldwide measures for curbing the spread of the COVID-19 virus have led to unprecedented and abrupt lockdowns in transportation and industry. They have led to sharp decrease of emissions of anthropogenic pollutants that induced significant changes in the composition of the atmosphere from city to hemispheric scale. Using an […]

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 […]