Multi-year TROPOMI trace gas columns, created on the occasion of three years S-5P/TROPOMI

April 2021 marked the 3rd anniversary of the first public release of atmospheric measurements by the Sentinel 5 Precursor (S5P) TROPOMI instrument, launched in October 2017. BIRA-IASB has been strongly involved in the development of algorithms for the derivation of trace gas column products derived from TROPOMI measurements, as well as in validation activities, and quality monitoring of the TROPOMI data.

On the occasion of three years of TROPOMI data, global data sets have been released for the main atmospheric molecules that BIRA-IASB has worked on. The data is available as L3 data in GeoTiff format, representing data averaged over a period from 2.5 to just over 3 years, depending on the molecule. The data can be consulted as global maps through the links provided further down on this page.

There are 6 molecules for which data is available:

• Formaldehyde (HCHO) is an intermediate product of the chemical oxidation of a wide range of volatile hydrocarbon molecules, which play an important role in the formation of tropospheric ozone and aerosols. Although these hydrocarbons cannot generally be detected from space, the formaldehyde content can be mapped globally. The Sentinel-5P/TROPOMI instrument provides formaldehyde maps with unprecedented sensitivity and spatial resolution. This leads to a better understanding of hydrocarbon emissions and their role in air quality and climate-related processes.

• Atmospheric glyoxal (CHOCHO) is a hydrocarbon gas that can be traced back to a wide range of both natural and anthropogenic sources. Although it can be injected directly into the atmosphere in case of fire events, it is usually found as an intermediate component in chemical oxidation chains of other hydrocarbons, many of which are relevant to air quality and climate studies. With a relatively short lifetime of several hours, glyoxal is found close to hydrocarbon sources and its global monitoring from space helps constraining the source inventories used in atmospheric chemistry transport models.

• Sulphur dioxide (SO2) is emitted in the atmosphere through both natural and anthropogenic processes. Human activity accounts for about twothirds of the total budget, mainly via fossil fuel combustion and smelting. Through the formation of sulphate aerosols and sulphuric acid, sulphur dioxide plays an important role in the chemistry at local and global scales and its impact ranges from short-term pollution to climate forcing. This map shows the average SO2 signal from three years of Sentinel-5P/TROPOMI satellite measurements, showing a large number of pollution and volcanic sources.

• Atmospheric nitrogen dioxide (NO2) is a pollutant gas that originates from both natural sources and human activity, the latter accounting for about 65% of the total amount. This map shows total vertical column amounts of nitrogen dioxide, as detected by the Sentinel-5P/TROPOMI instrument, launched in 2017. The NO2 signal was here averaged over a three-year period, revealing a large range of pollution sources from major urban areas down to smaller cities and individual industrial plants.

• Carbon monoxide (CO) has both natural and anthropogenic sources, with is known to contribute to pollution in urban areas through fossil fuel combustion. In natural environments, oxidation with hydrocarbons or biomass-burning are the most relevant sources. Carbon monoxide has a relatively long lifetime (weeks to months), which allows for CO clouds to be followed over long distances. This explains the more diffuse CO distribution over the oceans in this global carbon dioxide map, that is an average over all S-5P/TROPOMI measurements between end 2017 and end 2020.

• After carbon dioxide (CO2), methane (CH4) is the second most important greenhouse gas. Although the atmospheric content is less, methane is about 25 times more effective in warming the atmosphere than carbon dioxide, and knowledge on its atmospheric sources and sinks are therefore of the utmost importance in climate studies. This global map shows the average methane content of 3 years of S-5P/TROPOMI data.