04 Jul 2022
04 Jul 2022
Status: this preprint is currently under review for the journal AMT.

Intercomparison of Sentinel-5P TROPOMI cloud products for tropospheric trace gas retrievals

Miriam Latsch1, Andreas Richter1, Henk Eskes2, Maarten Sneep2, Ping Wang2, Pepijn Veefkind2, Ronny Lutz3, Diego Loyola3, Athina Argyrouli3,7, Pieter Valks3, Thomas Wagner4, Holger Sihler4, Michel van Roozendael5, Nicolas Theys5, Huan Yu5, Richard Siddans6, and John P. Burrows1 Miriam Latsch et al.
  • 1Institute of Environmental Physics, University of Bremen (IUP-UB), Otto-Hahn-Allee 1, 28359 Bremen, Germany
  • 2KNMI, Royal Netherlands Meteorological Institute, De Bilt, the Netherlands
  • 3Remote Sensing Technology Institute, German Aerospace Centre (DLR), Wessling, Germany
  • 4Max Planck Institute for Chemistry (MPIC), Mainz, Germany
  • 5Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
  • 6Science and Technology Facilities Council, Rutherford Appleton Laboratory (RAL), Chilton, UK
  • 7Technical University of Munich, Department of Civil, Geo and Environmental Engineering, Munich, Germany

Abstract. Clouds have a strong impact on satellite measurements of tropospheric trace gases in the ultraviolet, visible, and near-infrared spectral ranges from space. Therefore, trace gas retrievals rely on information on cloud fraction, cloud albedo, and cloud height from cloud products. In this study, the cloud parameters from different cloud retrieval algorithms for Sentinel-5 Precursor (S5P) TROPOMI are compared: the OCRA a priori cloud fraction, the ROCINN CAL cloud fraction and cloud top and base height, the ROCINN CRB cloud fraction and cloud height, the FRESCO cloud fraction, the interpolated FRESCO cloud height from the TROPOMI NO2 product, the cloud fraction from the NO2 fitting window, the O2-O2 cloud fraction and cloud height, the MICRU cloud fraction, and the VIIRS cloud fraction. Two different versions of the TROPOMI cloud products OCRA/ROCINN, FRESCO, and the TROPOMI NO2 product are included in the comparisons (processor version 1.x and 2.x). Overall, the cloud parameters retrieved by the different algorithms show qualitative consistency in version 1.x and good agreement in version 2.x with the exception of the VIIRS cloud fraction, which cannot be directly compared to the other data. Differences between the cloud retrievals are found especially for small cloud heights with a cloud fraction threshold of 0.2, i.e., clouds that are particularly relevant for tropospheric trace gas retrievals. The cloud fractions of the different version 2 cloud products primarily differ over snow- and ice-covered pixels and scenes with sun glint, for which only MICRU includes an explicit treatment. All cloud parameters show some systematic problems related to the across-track dependence, where larger values are found at the edges of the satellite view. The consistency between the cloud parameters from different algorithms depends strongly on how the data is filtered for the comparison, e.g., what quality value is used or whether snow- and ice-covered pixels are excluded from the analysis. In summary, clear differences were found between the results of various algorithms, but these differences are reduced in the most recent versions of the cloud data.

Miriam Latsch et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-122', Anonymous Referee #3, 19 Jul 2022
  • RC2: 'Comment on amt-2022-122', Anonymous Referee #4, 27 Jul 2022

Miriam Latsch et al.

Miriam Latsch et al.


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Short summary
The article investigates different S5P TROPOMI cloud retrieval algorithms for tropospheric trace gas retrievals. The cloud products show differences primarily over snow and ice and for scenes under sun glint. Some issues regarding across-track dependence are found for the cloud fractions as well as for the cloud heights.