Preprints
https://doi.org/10.5194/gmd-2020-442
https://doi.org/10.5194/gmd-2020-442

Submitted as: development and technical paper 09 Mar 2021

Submitted as: development and technical paper | 09 Mar 2021

Review status: a revised version of this preprint was accepted for the journal GMD.

A versatile method for computing optimized snow albedo from spectrally fixed radiative variables: VALHALLA v1.0

Florent Veillon1,2, Marie Dumont2, Charles Amory1,3, and Mathieu Fructus2 Florent Veillon et al.
  • 1Laboratory of Climatology, Department of Geography, SPHERES, University of Liège, Liège, Belgium
  • 2Université Grenoble Alpes, Université de Toulouse, Météo-France, CNRS, CNRM, Centre d’Etudes de la Neige, 38000 Grenoble, France
  • 3Université Grenoble Alpes, CNRS, Institut des Géosciences de l’Environnement, 38000, Grenoble, France

Abstract. In climate models, the snow albedo scheme generally calculates only a narrowband or broadband albedo, which leads to significant uncertainties. Here, we present the Versatile ALbedo calculation metHod based on spectrALLy fixed radiative vAriables (VALHALLA, version 1.0), to optimize spectral snow albedo calculation. For this optimization, the energy absorbed by the snowpack is calculated by the spectral albedo model Two-streAm Radiative TransfEr in Snow (TARTES) and the spectral irradiance model Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART). This calculation takes into account the spectral characteristics of the incident radiation and the optical properties of the snow, based on an analytical approximation of the radiative transfer of snow. For this method, 30 wavelengths, called tie points (tps), and 16 reference irradiance profiles are calculated to incorporate the absorbed energy and the reference irradiance. The absorbed energy is then interpolated for each wavelength between two tps with adequate kernel functions derived from radiative transfer theory for snow and the atmosphere. We show that the accuracy of the absorbed energy calculation primarily depends on the adaptation of the irradiance of the reference profile to that of the simulation (absolute difference < 1 W m−2 for broadband absorbed energy and absolute difference < 0.005 for broadband albedo). In addition to the performance in accuracy and calculation time, the method is adaptable to any atmospheric input (broadband, narrowband), and is easily adaptable for integration into a radiative scheme of a global or regional climate model.

Florent Veillon 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 gmd-2020-442', Joseph Cook, 23 Mar 2021
  • RC2: 'Comment on gmd-2020-442', Christiaan van Dalum, 14 Apr 2021
  • AC1: 'AC to Joseph Cook comments', Marie Dumont, 27 Aug 2021

Florent Veillon et al.

Florent Veillon et al.

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Short summary
In climate models, the snow albedo scheme generally calculates only a narrowband or broadband albedo. Therefore, we have developed the VALHALLA method to optimize snow spectral albedo calculations through the determination of spectrally fixed radiative variables. The development of VALHALLA v1.0 with the use of the snow albedo model TARTES and the spectral irradiance model SBDART indicates a considerable reduction in calculation time while maintaining an adequate accuracy of albedo values.