Effect of small-scale snow surface roughness on snow albedo and
reflectance

Manninen, Terhikki; Anttila, Kati; Jääskeläinen, Emmihenna; Riihelä, Aku; Peltoniemi, Jouni; Räisänen, Petri; Lahtinen, Panu; Siljamo, Niilo; Thölix, Laura; Meinander, Outi; Kontu, Anna; Suokanerva, Hanne; Pirazzini, Roberta; Suomalainen, Juha; Hakala, Teemu; Kaasalainen, Sanna; Kaartinen, Harri; Kukko, Antero; Hautecoeur, Olivier; Roujean, Jean-Louis

doi:https://doi.org/10.5194/tc-2020-154

Preprints

https://doi.org/10.5194/tc-2020-154
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Preprints

30 Jul 2020

Effect of small-scale snow surface roughness on snow albedo and reflectance

Terhikki Manninen¹, Kati Anttila¹, Emmihenna Jääskeläinen¹, Aku Riihelä¹, Jouni Peltoniemi², Petri Räisänen¹, Panu Lahtinen¹, Niilo Siljamo¹, Laura Thölix¹, Outi Meinander¹, Anna Kontu¹, Hanne Suokanerva¹, Roberta Pirazzini¹, Juha Suomalainen², Teemu Hakala², Sanna Kaasalainen², Harri Kaartinen^2,3, Antero Kukko^2,4, Olivier Hautecoeur^5,a, and Jean-Louis Roujean⁶ Terhikki Manninen et al.

¹Finnish Meteorological Institute, Helsinki, P.O. Box 503, 00101, Finland
²Finnish Geospatial Research Institute/National Land Survey, Geodeetinrinne 2, 02430 Masala, Finland
³University of Turku, Department of Geography and Geology, 20500 Turku, Finland
⁴Aalto University, Department of Built Environment, 02150 Espoo, Finland
⁵Météo-France
⁶Centre d’Etudes Spatiales de la BIOsphère (CESBIO) - UMR 5126 - 31401 Toulouse, France
^acurrently at: Exostaff GmbH/EUMETSAT

Received: 08 Jun 2020 – Accepted for review: 29 Jul 2020 – Discussion started: 30 Jul 2020

Abstract. The primary goal of this paper is to present a model of snow surface albedo accounting for small-scale surface roughness effects. The model is based on photon recollision probability and it can be combined with existing bulk volume albedo models, such as TARTES. The model is fed with in situ measurements of surface roughness from plate profile and laser scanner data, and it is evaluated by comparing the computed albedos with observations. It provides closer results to empirical values than volume scattering based albedo simulations alone. The impact of surface roughness on albedo increases with the progress of the melting season and is larger for larger solar zenith angles. In absolute terms, surface roughness can decrease the total albedo by up to about 0.1. As regards the bidirectional reflectance factor (BRF), it is found that surface roughness increases backward scattering especially for large solar zenith angle values.

Terhikki Manninen et al.