Estimating Fractional Snow Cover in Open Terrain from Sentinel-2 Using the Normalized Difference Snow Index

Simon Gascoin (1) , Zacharie Barrou Dumont (1) , César Deschamps-Berger (1, 2) , Florence Marti (3) , Germain Salgues (3) , Juan Ignacio López-Moreno (4) , Jesús Revuelto (4) , Timothée Michon (5) , Paul Schattan (6) , Olivier Hagolle (1)

1 CESBIO - Centre d'études spatiales de la biosphère
2 CEN - Centre d'Etudes de la Neige
3 Magellium
4 CSIC - Consejo Superior de Investigaciones Científicas [Spain]
5 Tenevia
6 Leopold Franzens Universität Innsbruck - University of Innsbruck

Sentinel-2 provides the opportunity to map the snow cover at unprecedented spatial and temporal resolutions on a global scale. Here we calibrate and evaluate a simple empirical function to estimate the fractional snow cover (FSC) in open terrains using the normalized difference snow index (NDSI) from 20 m resolution Sentinel-2 images. The NDSI is computed from flat surface reflectance after masking cloud and snow-free areas. The NDSI-FSC function is calibrated using Pléiades very high-resolution images and evaluated using independent datasets including SPOT 6/7 satellite images, time lapse camera photographs, terrestrial lidar scans and crowd-sourced in situ measurements. The calibration results show that the FSC can be represented with a sigmoid-shaped function 0.5 × tanh(a × NDSI + b) + 0.5, where a = 2.65 and b = −1.42, yielding a root mean square error (RMSE) of 25%. Similar RMSE are obtained with different evaluation datasets with a high topographic variability. With this function, we estimate that the confidence interval on the FSC retrievals is 38% at the 95% confidence level.

Mots clés: snow; snow cover area; fractional snow cover; Sentinel-2

Domaines: Sciences du Vivant [q-bio]

Simon Gascoin, Zacharie Barrou Dumont, César Deschamps-Berger, Florence Marti, Germain Salgues, et al.. Estimating Fractional Snow Cover in Open Terrain from Sentinel-2 Using the Normalized Difference Snow Index. Remote Sensing, 2020, 12 (18), pp.2904. ⟨10.3390/rs12182904⟩. ⟨hal-02990463⟩