Backward snow depth reconstruction at high spatial resolution based on time-lapse photography

We report a methodology for reconstructing the daily snow depth distribution at high spatial resolution in a small Pyrenean catchment using time-lapse photographs and snow depletion rates derived from an on-site measuring meteorological station. The results were compared with the observed snow depth distribution, determined on a number of separate occasions using a terrestrial laser scanner (TLS). The time-lapse photographs were projected onto a digital elevation model of the study site, and converted into snow presence/absence information. The melt-out date (MOD; first occurrence of melt out after peak snow accumulation) was obtained from the projected photograph series. Commencing the backward reconstruction for each grid cell at the MOD, the method uses simulated snow depth depletion rates using a temperature index approach, which are extrapolated to the grid cells of the domain to arrive at the snow distribution of the previous day. Two variants of the reconstruction techniques were applied (1) using a spatially constant degree day factor (DDF) for calculating the daily expected snow depth depletion rate, and (2) allowing a spatially distributed DDF calculated from two consecutive TLS acquisitions compared to the snow depth depletion rate observed at the meteorological station. Validation revealed that both methods performed well (average R2 = 0.68; standard RMSE = 0.58), with better results obtained from the spatially distributed approach. Nevertheless, the spatially corrected DDF reconstruction, which requires TLS data, suggests that the constant DDF approach is an efficient, and for most applications sufficiently accurate and easily reproducible method. The results highlight the usefulness of time-lapse photography for not only determining the snow covered area, but also for estimating the spatial distribution of snow depth. Copyright © 2016 John Wiley & Sons, Ltd.

This study was supported by the research projects ‘Hidrología nival en el Pirineo Central Español: Variabilidad espacial, importancia hidrológica y respuesta a la variabilidad y cambio climático (CGL2011-27536/HID, Hidronieve)’ and ‘IBERNIEVE: estudio del manto de nieve en la montaña española, y su respuesta a la variabilidad y cambio climatico (CGL2014-52599-P)’, financed by the Spanish Commission of Science and Technology and FEDER; and ‘El glaciar de Monte Perdido: Monitorización y estudio de su dinámica actual y procesos criosféricos asociados como indicadores de procesos de cambio global 844/2013’, financed by MAGRAMA National Parks. The first author is a recipient under the pre-doctoral FPU grant programme 2010 (Spanish Ministry of Education Culture and Sports).

Peer reviewed