Retrievals of glyoxal tropospheric vertical columns from TROPOMI observations

Since its launch in October 2017, TROPOMI records earthshine radiances in spectral ranges from the ultraviolet to the shortwave infrared regions at an unprecedented spatial resolution (3.5 x 7 km² and 3.5 x 5.5 km² after August 2019). A suite of L2 operational products provide key information for the understanding and monitoring of the Earth-atmosphere system, and more particularly of aspects related to ozone layer protection, air quality and climate change.

The ESA S5p+ Innovation activity aims at further exploiting the capability of the TROPOMI instrument by supporting the development of a number of additional scientific products, including glyoxal tropospheric column retrievals. The latter provide information on VOC emissions as glyoxal is mainly released in the atmosphere as an intermediate product of VOC oxidation, but also directly emitted from biomass burning events.

We present here the BIRA-IASB S5p glyoxal product relying on a DOAS approach and its main features. We show how the large amount of TROPOMI data and its high resolution helps to better identify and localize VOC sources. The many intense fire events that occurred in the last years, e.g. in Northern America in 2018 or in Australia in 2019/2020, led to extreme levels of pollution and unprecedentedly high glyoxal columns are measured accordingly. We also highlight the excellent consistency between the TROPOMI and OMI glyoxal products, allowing thus to combine them in a 15-year data record. The validation of satellite glyoxal retrievals is difficult due to the scarcity of independent data and their own limitations caused by the low glyoxal optical depth. Nevertheless, a few ground-based data sets have been collected and preliminary comparisons with the S5p glyoxal product are presented.