06 Nov 2020

06 Nov 2020

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

Increasing the spatial resolution of cloud property retrievals from Meteosat SEVIRI by use of its high-resolution visible channel: implementation and examples

Hartwig Deneke1, Carola Barrientos-Velasco1, Sebastian Bley2, Anja Hünerbein1, Stephan Lenk1, Andreas Macke1, Jan Fokke Meirink3, Marion Schroedter-Homscheidt4, Fabian Senf1, Ping Wang3, Frank Werner5, and Jonas Witthuhn1 Hartwig Deneke et al.
  • 1Leibniz Institute for Tropospheric Research, Permoserstraße 15, 04318 Leipzig, Germany
  • 2ESA Centre for Earth Observation, Largo Galileo Galilei, 1, 00044 Frascati RM, Italy
  • 3Royal Netherlands Meteorological Institute, Utrechtseweg 297, 3731 GA De Bilt
  • 4German Aerospace Center (DLR), Institute of Networked Energy Systems, Carl-von-Ossietzky-Straße 15, 26129 Oldenburg, Germany
  • 5Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA

Abstract. The modification of an existing cloud property retrieval scheme for the Spinning Enhanced Visible and Infrared Imager (SEVIRI) instrument onboard the geostationary METEOSAT satellites is described to utilize its high-resolution visible (HRV) channel for increasing the spatial resolution of its physical outputs. This results in products with a nadir spatial resolution of 1 × 1 km2, compared to the standard 3 × 3 km2 resolution offered by the narrowband channels. This improvement thus greatly reduces the resolution gap between current geostationary and polar-orbiting meteorological satellite imagers. In the first processing step, cloudiness is determined from the HRV observations by a threshold-based cloud masking algorithm. Subsequently, a linear model that links the 0.6 μm, 0.8 μm, and HRV reflectances provides a physical constraint to incorporate the spatial high-frequency component of the HRV observations into the retrieval of cloud optical depth. The implementation of the method is described, including the ancillary datasets used. It is demonstrated that the omission of high-frequency variations in the cloud-absorbing 1.6 μm channel results in comparatively large uncertainties in the retrieved cloud effective radius, likely due to the mismatch in channel resolutions. A newly developed downscaling scheme for the 1.6 μm reflectance is therefore applied to mitigate the effects of this scale mismatch. Benefits of the increased spatial resolution of the resulting SEVIRI products are demonstrated for three example applications: (i) for a convective cloud field, it is shown that significantly better agreement between the distributions of cloud optical depth retrieved from SEVIRI and from collocated MODIS observations is achieved; (ii) the temporal evolution of cloud properties for a growing convective storm at standard and HRV spatial resolutions are compared, illustrating an improved contrast in growth signatures resulting from the use of the HRV channel; (iii) an example of surface solar irradiance, determined from the retrieved cloud properties, is shown, where the HRV channel helps to better capture the large spatio-temporal variability induced by convective clouds. These results suggest that incorporating the HRV channel in the retrieval has potential for improving METEOSAT-based cloud products for several application domains.

Hartwig Deneke et al.

Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

Hartwig Deneke et al.

Hartwig Deneke et al.


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Short summary
The SEVIRI instrument flown on the European geostationary METEOSAT satellites acquires multi-spectral images at a relatively coarse pixel resolution of 3 × 3 km2. SEVIRI also has a broadband high-resolution visible channel with 1 × 1 km2 spatial resolution. In the present study, the modification of an existing cloud property and solar irradiance retrieval to use this channel to improve the spatial resolution of its output products, and resulting benefits for applications are described.