Skip to main content

Geophysical assessment of tropical tropospheric ozone

Research Topic Chapter
News flash intro
Monitoring ozone in the global troposphere is a challenge, but key to verifying whether scientific understanding and resulting (inter)national regulations are sufficient to protect public health and ecosystems. Designed with high-resolution capabilities for tropospheric ozone monitoring, the Sentinel-5p TROPOMI Instrument has been acquiring since 2017 a valuable Climate Data Record. BIRA-IASB researchers have demonstrated the unprecedented accuracy of the TROPOMI data, and its value for international scientific assessments like IGAC TOAR-II.
Body text

Measuring tropospheric ozone is essential, but still challenging

High levels of ozone in the troposphere have detrimental effects on humans and ecosystems, as an air pollutant and climate variable. (Inter)national environmental regulations have therefore been put in place to control ozone and its precursors.

The scientific community regularly assesses the effectiveness of these protocols, hereby relying on accurate, well-characterised measurements at the best possible resolution and covering the global scale over several decades. Meeting these requirements is a true challenge, but needed to fuel progress in understanding the processes controlling ozone in the troposphere.

TROPOMI raises standards

The TROPOspheric Monitoring Instrument, launched into space in 2017 aboard the Copernicus Sentinel-5p satellite, is the European flagship to monitor ozone and its precursors at unequalled resolution. TROPOMI records tropospheric ozone observations daily over the tropical belt.

BIRA-IASB researchers are responsible to validate this (and other) TROPOMI data record(s) and have developed an operational system that evaluates data quality continuously and nearly in real-time. They have recently concluded a comprehensive assessment of the first two years of TROPOMI tropospheric ozone data.

Assessing the quality of TROPOMI data

In-depth comparisons to reference measurements are key in assessments of data quality. BIRA-IASB researchers used correlative data from balloon-borne ozonesondes and from two other satellite sounders to establish that the biases and precision of TROPOMI tropospheric ozone data are better than 15% and 8-13%, respectively.

It was furthermore demonstrated that the high resolution of TROPOMI enables much more detailed studies of geophysical structures and phenomena such as:

  • biomass burning effects
  • Madden-Julian Oscillation
  • Zonal wave-one

TROPOMI indeed offers superior tropospheric ozone data over past and recent satellite sounders, and is acquiring a valuable ozone Climate Data Record.

International scientific assessments of tropospheric ozone

BIRA-IASB researchers are extending their TROPOMI analysis to other satellite data records. They are investigating possible causes of long-standing differences between the data sets, with a particular attention to smoothing and sampling issues. Reconciling the data sets is necessary to progress with the understanding of the spatial distribution and temporal evolution of tropospheric ozone.

In this way, BIRA-IASB is committed to community-wide activities of the Committee on Earth Observation Satellites (CEOS) and of the second Tropospheric Ozone Assessment Report (TOAR-II), which will form the scientific basis for informed amendments to regulations related to air quality and climate change.



Hubert, D., Heue, K.-P., Lambert, J.-C., Verhoelst, T., Allaart, M., Compernolle, S., Cullis, P. D., Dehn, A., Félix, C., Johnson, B. J., Keppens, A., Kollonige, D. E., Lerot, C., Loyola, D., Maata, M., Mitro, S., Mohamad, M., Piters, A., Romahn, F., Selkirk, H. B., da Silva, F. R., Stauffer, R. M., Thompson, A. M., Veefkind, J. P., Vömel, H., Witte, J. C., and Zehner, C.: TROPOMI tropospheric ozone column data: Geophysical assessment and comparison to ozonesondes, GOME-2B and OMI, Atmos. Meas. Tech. Discuss.,, in review, 2020.

Figure 2 body text
Figure 2 caption (legend)
Comparison of TROPOMI (black) and ozonesonde (red) data at Natal (Brazil), a location that is affected annually by strong enhancements of tropospheric ozone due to biomass burning.
Figure 3 body text
Figure 3 caption (legend)
Observation by TROPOMI of elevated tropospheric ozone levels (>30 DU) around the Atlantic basin in the first half of November 2019, clearly linked to biomass burning on the African and South American continents.
Publication date