10 Jun 2021

10 Jun 2021

Review status: this preprint is currently under review for the journal AMT.

Glyoxal tropospheric column retrievals from TROPOMI, multi-satellite intercomparison and ground-based validation

Christophe Lerot1, François Hendrick1, Michel Van Roozendael1, Leonardo M. A. Alvarado2,3, Andreas Richter3, Isabelle De Smedt1, Nicolas Theys1, Jonas Vlietinck1, Huan Yu1, Jeroen Van Gent1, Trissevgeni Stavrakou1, Jean-François Müller1, Pieter Valks4, Diego Loyola4, Hitoshi Irie5, Vinod Kumar6, Thomas Wagner6, Stefan F. Schreier7, Vinayak Sinha8, Ting Wang9, Pucai Wang9, and Christian Retscher10 Christophe Lerot et al.
  • 1Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
  • 2Alfred Wegner Institute, Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany
  • 3University of Bremen, Institute of Environmental Physics, Bremen, Germany
  • 4Institut für Methodik der Fernerkundung (IMF), Deutsches Zentrum für Luft und Raumfahrt (DLR), Oberpfaffenhofen, Germany
  • 5Center for Environmental Remote Sensing, Chiba University, Japan
  • 6Max Planck Institute for Chemistry (MPIC), Mainz, Germany
  • 7Institute of Meteorology and Climatology, University of Natural Resources and Life Sciences, Vienna, Austria
  • 8Indian Institute of Science Education and Research Mohali, Mohali, India
  • 9Institute of Atmospheric Physics, Chinese Academy of Sciences (CAS), Beijing, China
  • 10European Space Agency, ESRIN, Frascati, Italy

Abstract. We present the first global glyoxal (CHOCHO) tropospheric column product derived from the TROPOspheric Monitoring Instrument (TROPOMI) on board of the Sentinel-5 Precursor satellite. Atmospheric glyoxal results from the oxidation of other non-methane volatile organic compounds (NMVOCs) and from direct emissions caused by combustion processes. Therefore, this product is a useful indicator of VOC emissions. It is generated with an improved version of the BIRA-IASB scientific retrieval algorithm relying on the Differential Optical Absorption Spectroscopy (DOAS) approach. Among the algorithmic updates, the DOAS fit now includes corrections to mitigate the impact of spectral misfits caused by scene brightness inhomogeneity and strong NO2 absorption. The product comes along with a full error characterization, which allows providing random and systematic error estimates for every observation. Systematic errors are typically in the range of 1–3 × 1014 molec/cm2 (~30–70 % in emission regimes). Random errors are larger (> 6 × 1014 molec/cm2) but can be reduced by averaging observations in space and/or time. Benefiting from a high signal-to-noise ratio and a large number of small-size observations, TROPOMI provides glyoxal tropospheric column fields with an unprecedented level of details.

Using the same retrieval algorithmic baseline, glyoxal column data sets are also generated from the Ozone Monitoring Instrument (OMI) on Aura and from the Global Ozone Monitoring Experiment-2 (GOME-2) on board of Metop-A and Metop-B. Those four data sets are intercompared over large-scale regions worldwide and show a high level of consistency. The satellite glyoxal columns are also compared to glyoxal columns retrieved from ground-based Multi-Axis (MAX-) DOAS instruments at nine stations in Asia and Europe. In general, the satellite and MAX-DOAS instruments provide consistent glyoxal columns both in terms of absolute values and variability. Correlation coefficients between TROPOMI and MAX-DOAS glyoxal columns range between 0.61 and 0.87. The correlation is only poorer at one mid-latitude station, where satellite data appears low biased during wintertime. The mean absolute glyoxal columns from satellite and MAX-DOAS generally agree well for low/moderate columns with differences less than 1 × 1014 molec/cm2. A larger bias is identified at two sites where the MAX-DOAS columns are very large. Despite this systematic bias, the consistency of the satellite and MAX-DOAS glyoxal seasonal variability is excellent.

Christophe Lerot et al.

Status: open (until 05 Aug 2021)

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Christophe Lerot et al.

Christophe Lerot et al.


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Short summary
Global measurements of glyoxal tropospheric columns from the satellite instrument TROPOMI are presented. Such measurements can contribute to the estimation of atmospheric emissions of volatile organic compounds. This new glyoxal product has been fully characterized with a comprehensive error budget, with comparison with other satellite data sets as well as with validation based on independent ground-based remote sensing glyoxal observations.