Preprints
https://doi.org/10.5194/amt-2021-377
https://doi.org/10.5194/amt-2021-377

  15 Dec 2021

15 Dec 2021

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

DARCLOS: a cloud shadow detection algorithm for TROPOMI

Victor Trees1,2, Ping Wang1, Piet Stammes1, Lieuwe G. Tilstra1, David P. Donovan1,2, and A. Pier Siebesma1,2 Victor Trees et al.
  • 1Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands
  • 2Delft University of Technology, Delft, the Netherlands

Abstract. Cloud shadows are observed by the TROPOMI satellite instrument as a result of its high spatial resolution as compared to its predecessor instruments. These shadows contaminate TROPOMI's air quality measurements, because shadows are generally not taken into account in the models that are used for aerosol and trace gas retrievals. If the shadows are to be removed from the data, or if shadows are to be studied, an automatic detection of the shadow pixels is needed. We present the Detection AlgoRithm for CLOud Shadows (DARCLOS) for TROPOMI, which is the first cloud shadow detection algorithm for a spaceborne spectrometer. DARCLOS raises potential cloud shadow flags (PCSFs), and actual cloud shadow flags (ACSFs). The PCSFs indicate the TROPOMI ground pixels that are potentially affected by cloud shadows based on a geometric consideration with safety margins. The ACSFs are a refinement of the PCSFs using spectral reflectance information of the PCSF pixels, and identify the TROPOMI ground pixels that are confidently affected by cloud shadows. We validate DARCLOS with true color images made by the VIIRS instrument on board of Suomi NPP orbiting in close constellation with TROPOMI on board of Sentinel 5-P. We conclude that the PCSF can be used to exclude cloud shadow contamination from TROPOMI data, while the ACSF can be used to select pixels for the scientific analysis of cloud shadow effects.

Victor Trees et al.

Status: open (until 19 Jan 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-377', Anonymous Referee #1, 15 Dec 2021 reply
  • RC2: 'Comment on amt-2021-377', Anonymous Referee #2, 20 Dec 2021 reply

Victor Trees et al.

Victor Trees et al.

Viewed

Total article views: 273 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
204 64 5 273 5 2
  • HTML: 204
  • PDF: 64
  • XML: 5
  • Total: 273
  • BibTeX: 5
  • EndNote: 2
Views and downloads (calculated since 15 Dec 2021)
Cumulative views and downloads (calculated since 15 Dec 2021)

Viewed (geographical distribution)

Total article views: 253 (including HTML, PDF, and XML) Thereof 253 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 15 Jan 2022
Download
Short summary
Cloud shadows are observed by the TROPOMI satellite instrument as a result of its high spatial resolution. These shadows contaminate TROPOMI's air quality measurements, because shadows are generally not taken into account in the models that are used for aerosol and trace gas retrievals. We present the Detection AlgoRithm for CLOud Shadows (DARCLOS) for TROPOMI, which is the first cloud shadow detection algorithm for a satellite spectrometer.