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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/amt-2020-63
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/amt-2020-63
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 06 Mar 2020

Submitted as: research article | 06 Mar 2020

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This preprint is currently under review for the journal AMT.

1.5 years of TROPOMI CO measurements: Comparisons to MOPITT and ATom

Sara Martínez-Alonso1, Merritt Deeter1, Helen Worden1, Tobias Borsdorff2, Ilse Aben2, Róisin Commane3, Bruce Daube7, Gene Francis1, Maya George4, Jochen Landgraf2, Debbie Mao1, Kathryn McKain5,6, and Steven Wofsy7 Sara Martínez-Alonso et al.
  • 1Atmospheric Chemistry Observations and Modeling (ACOM), National Center for Atmospheric Research (NCAR), Boulder, CO, USA
  • 2SRON Netherlands Institute for Space Research, Utrecht, Netherlands
  • 3Lamont-Doherty Earth Observatory, Columbia University, NY, USA
  • 4LATMOS/IPSL, Sorbonne University, UVSQ, CNRS, Paris, France
  • 5Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO, USA
  • 6Earth System Research Laboratory, Global Monitoring Division (GMD), National Oceanic and Atmospheric Administration, Boulder, CO, USA
  • 7School of Engineering and Applied Science and Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA

Abstract. We have analyzed TROPOspheric Monitoring Instrument (TROPOMI) carbon monoxide (CO) data acquired between November 2017 and March 2019 with respect to other satellite (MOPITT, Measurement Of Pollution In The Troposphere) and airborne (ATom, Atmospheric Tomography mission) datasets to understand better TROPOMI’s contribution to the global tropospheric CO record (2000 to present). TROPOMI and MOPITT are currently the only satellite instruments deriving CO from solar reflected radiances. Therefore, it is particularly important to understand how these two datasets compare. Our results indicate that TROPOMI CO retrievals over land show excellent agreement with respect to MOPITT: relative biases and their standard deviation (i.e., accuracy and precision) are on average −3.73 ± 11.51, −2.24 ± 12.38, and −3.22 ± 11.13 %, compared to the MOPITT TIR (thermal infrared), NIR (near infrared), and TIR+NIR (multispectral) products, respectively. TROPOMI and MOPITT data also show good agreement in terms of temporal and spatial patterns.

Despite depending on solar reflected radiances for its measurements, TROPOMI can also retrieve CO over bodies of water if clouds are present, by approximating partial columns under cloud tops using scaled, model-based reference CO profiles. We quantify the bias of TROPOMI total column retrievals over bodies of water with respect to colocated in situ ATom CO profiles after smoothing the latter with the TROPOMI column averaging kernels (AK), which account for signal attenuation under clouds (relative bias and its standard deviation = 3.25 ± 11.46 %). In addition, we quantify enull (the null-space error), which accounts for differences between the shape of the TROPOMI reference profile and that of the ATom true profile (enull = 2.16 ± 2.23 %). For comparisons of TROPOMI and MOPITT retrievals over open water, we adopt a simpler approach, since smoothing with TROPOMI AK does not apply for MOPITT retrievals. To this effect, we compare TROPOMI total CO columns (above and below cloud tops) and partial CO columns (above cloud top) to their colocated MOPITT TIR counterparts. (This approximation would be most accurate for optically thick clouds.) We find very small changes in relative bias between TROPOMI and MOPITT TIR retrievals if total columns are considered instead of partial above-cloud-top columns (< 1 percentage point).

Sara Martínez-Alonso et al.

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Latest update: 06 Apr 2020
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Short summary
CO is of great importance in climate and air quality studies. To understand newly available TROPOMI data in the frame of the global CO record, we compared those to satellite (MOPITT) and airborne (ATom) CO datasets. The MOPITT dataset is the longest to date (2000-present) and is well characterized. We used ATom to validate cloudy TROPOMI data over oceans and investigate TROPOMI’s vertical sensitivity to CO. Our results show that TROPOMI CO data are in excellent agreement with the other datasets.
CO is of great importance in climate and air quality studies. To understand newly available...
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