Preprints
https://doi.org/10.5194/amt-2020-502
https://doi.org/10.5194/amt-2020-502

  01 Feb 2021

01 Feb 2021

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

Directionally dependent Lambertian-equivalent reflectivity (DLER) of the Earth's surface measured by the GOME-2 satellite instruments

Lieuwe G. Tilstra, Olaf N. E. Tuinder, Ping Wang, and Piet Stammes Lieuwe G. Tilstra et al.
  • Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands

Abstract. In this paper we introduce the new concept of directionally dependent Lambertian-equivalent reflectivity (DLER) of the Earth's surface retrieved from satellite observations. This surface DLER describes Lambertian (isotropic) surface reflection which is extended with a dependence on the satellite viewing geometry. We apply this concept to data of the GOME-2 satellite instruments, to create a global database of the reflectivity of the Earth's surface, providing surface DLER for 26 wavelength bands between 328 and 772 nm as a function of the satellite viewing angle via a second-degree polynomial parameterisation. The resolution of the database grid is 0.25 by 0.25 degrees but the real, intrinsic spatial resolution varies over the grid from 1.0 by 1.0 degrees to 0.5 by 0.5 degrees down to 0.25 by 0.25 degrees by applying dynamic gridding techniques. The database is based on more than ten years (2007–2018) of GOME-2 data from the MetOp-A and MetOp-B satellites.

The relation between surface DLER and surface BRDF is studied using radiative transfer simulations. For the shorter wavelengths (λ < 500 nm), there are significant differences between the two. For instance, at 463 nm the difference can go up to 6 % at 30° solar zenith angle. The study also shows that, although BRDF and DLER are different properties, they are comparable for the longer wavelengths (λ > 500 nm). Based on this outcome, the GOME-2 surface DLER is compared with MODIS surface BRDF data from MODIS band 1 (centred around 645 nm), using both case studies and global comparisons. The conclusion of this validation is that the GOME-2 DLER compares well to MODIS BRDF, and that it does so much better than the non-directional LER database. The DLER approach for describing surface reflectivity is therefore an important improvement over the standard isotropic (non-directional) LER approaches used in the past.

The GOME-2 surface DLER database can be used for the retrieval of atmospheric properties from GOME-2 and from previous satellite instruments like GOME and SCIAMACHY. It will also be used to support retrievals from the future Sentinel-5/UVNS satellite instrument.

Lieuwe G. Tilstra et al.

Status: open (until 29 Mar 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2020-502', Anonymous Referee #3, 01 Mar 2021 reply
  • RC2: 'Comment on amt-2020-502', Ruediger Lang, 02 Mar 2021 reply

Lieuwe G. Tilstra et al.

Lieuwe G. Tilstra et al.

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Short summary
In this paper we introduce the new concept of directionally dependent Lambertian-equivalent reflectivity (DLER) of the Earth's surface retrieved from satellite observations. We apply this concept to data of the GOME-2 satellite instruments, to create a global database of the reflectivity of the Earth's surface, providing surface DLER for 26 wavelength bands between 328 and 772 nm as a function of the satellite viewing angle via a second-degree polynomial parameterisation.