Preprints
https://doi.org/10.5194/amt-2021-141
https://doi.org/10.5194/amt-2021-141

  07 Jul 2021

07 Jul 2021

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

Retrieving H2O/HDO columns over cloudy and clear-sky scenes from the Tropospheric Monitoring Instrument (TROPOMI)

Andreas Schneider1,a, Tobias Borsdorff1, Joost aan de Brugh1, Alba Lorente1, Franziska Aemisegger2, David Noone3, Dean Henze4, Rigel Kivi5, and Jochen Landgraf1 Andreas Schneider et al.
  • 1Earth science group, SRON Netherlands Institute for Space Research, Utrecht, the Netherlands
  • 2Atmospheric Dynamics group, Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland
  • 3Department of Physics, University of Auckland, Auckland, New Zealand
  • 4Department of Ocean, Earth and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, United States of America
  • 5Earth Observation Research Unit, Finnish Meteorological Institute, Sodankylä, Finland
  • anow at: Earth Observation Research Unit, Finnish Meteorological Institute, Sodankylä, Finland

Abstract. This paper presents an extension of the scientific HDO/H2O column data product from the Tropospheric Monitoring Instrument (TROPOMI) including clear-sky and cloudy scenes. The retrieval employs a forward model which accounts for scattering, and the algorithm infers the trace gas column information, surface properties and effective cloud parameters from the observations. The extension to cloudy scenes greatly enhances coverage, particularly enabling data over oceans. The data set is validated against co-located ground-based Fourier transform infrared (FTIR) observations by the Total Carbon Column Observing Network (TCCON). The median bias for clear-sky scenes is 1.4 × 1021 molec cm−2 (2.9 %) in H2O columns and 1.1 × 1017 molec cm−2 (−0.3 %) in HDO columns, which corresponds to −17 ‰ (9.9 %) in a posteriori δD. The bias for cloudy scenes is 4.9 × 1021 molec cm−2 (11 %) in H2O, 1.1 × 1017 molec cm−2 (7.9 %) in HDO, and −20 ‰ (9.7 %) in a posteriori δD. At low-altitude stations in low and middle latitudes the bias is small, and has a larger value at high latitude stations. At high altitude stations, an altitude correction is required to compensate for different partial columns seen by the station and the satellite. The bias in a posteriori δD after altitude correction depends on sensitivity due to shielding by clouds, and on realistic prior profile shapes for both isotopologues. Cloudy scenes generally involve low sensitivity below the clouds, and since the information is filled up by the prior, it plays an important role in these cases. Over oceans, aircraft measurements with the Water Isotope System for Precipitation and Entrainment Research (WISPER) instrument from a field campaign in 2018 are used for validation, yielding a bias of −3.9 % in H2O and −3 ‰ in δD over clouds. To demonstrate the added value of the new data set, a short case study of a cold air outbreak over the Atlantic Ocean in January 2020 is presented, showing the daily evolution of the event with single overpass results.

Andreas Schneider et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Referee comment on amt-2021-141', Anonymous Referee #1, 15 Jul 2021
  • RC2: 'Comment on amt-2021-141', Anonymous Referee #3, 09 Sep 2021

Andreas Schneider et al.

Andreas Schneider et al.

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Short summary
This paper presents an extended H2O/HDO total column data set from short-wave infrared measurements by TROPOMI including cloudy and clear-sky scenes. Coverage is tremendously increased compared to previous TROPOMI HDO data sets. The new data set is validated against recent ground-based FTIR measurements from the TCCON network and against aircraft measurements over the ocean. The use of the new data set is demonstrated with a case study of a cold air outbreak in January 2020.