Preprints
https://doi.org/10.5194/amt-2022-103
https://doi.org/10.5194/amt-2022-103
 
29 Mar 2022
29 Mar 2022
Status: a revised version of this preprint is currently under review for the journal AMT.

Validation of Copernicus Sentinel-3/OLCI Level 2 LAND Integrated Water Vapour product

Niilo Kalakoski1, Viktoria Sofieva1, René Preusker2, Claire Henocq3, Matthieu Denisselle3, Steffen Dransfeld4, and Silvia Scifoni5 Niilo Kalakoski et al.
  • 1Finnish Meteorological Institute, Helsinki, Finland
  • 2Institute for Space Sciences, Freie Universität Berlin (FUB), Germany
  • 3ACRI-ST, Sophia-Antipolis, France
  • 4European Space Research Institute (ESRIN), Frascati, Italy
  • 5Serco Italia SpA for European Space Agency (ESA), European Space Research Institute (ESRIN), Frascati, Italy

Abstract. Geophysical validation of the Integrated Water Vapour (IWV) from Sentinel-3 Ocean and Land Colour Instrument (OLCI) was performed as a part of “ESA/Copernicus Space Component Validation for Land Surface Temperature, Aerosol Optical Depth and Water Vapour Sentinel-3 Products” (LAW) project. The IWV was compared with reference observations from two networks: GNSS (Global Navigation Satellite System) derived precipitable water vapour from the SUOMINET network and integrated lower tropospheric columns from radio-soundings from the IGRA (Integrated Radiosonde Archive) database.

Results for cloud-free matchups over land show a wet bias of 7–10 % for OLCI, with a high correlation against the reference observations (0.98 against SUOMINET and 0.90 againts IGRA). Both OLCI-A and -B instruments show almost identical results, apart from an anomaly observed in camera 3 of the OLCI-B instrument, where observed biases are lower than in other cameras in either instrument. The wavelength drift in sensors was investigated, and biases in different cameras were found to be independent of wavelength. Effect of cloud proximity was found to have almost no effect on observed biases, indicating that cloud-flagging in the OLCI IWV product is sufficiently robust. We performed validation of random uncertainty estimates and found them to be consistent with the statistical a posteriori estimates, but somewhat higher.

Niilo Kalakoski 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-2022-103', Anonymous Referee #1, 13 Apr 2022
    • AC1: 'Reply on RC1', Niilo Kalakoski, 23 Jun 2022
  • RC2: 'Comment on amt-2022-103', Anonymous Referee #2, 22 Apr 2022
    • AC2: 'Reply on RC2', Niilo Kalakoski, 23 Jun 2022

Niilo Kalakoski et al.

Niilo Kalakoski et al.

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Short summary
Geophysical validation of the Integrated Water Vapour (IWV) from Sentinel-3 Ocean and Land Colour Instrument (OLCI) was performed against reference observations from SUOMINET and IGRA databases. Results for cloud-free matchups over land show a wet bias of 7–10 % for OLCI, with a high correlation against the reference observations (0.98 against SUOMINET and 0.90 againts IGRA). Special attention is given to validation of uncertainty estimates and cloud-flagging.