Verification of the multi-layer SNOWPACK model with different water transport schemes

• Main Authors: Wever, N., Schmid, L., Heilig, A., Eisen, Olaf, Fierz, C., Lehning, M.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2015
• Subjects: The Cryosphere; The Cryosphere Discussions
• Online Access: https://epic.awi.de/id/eprint/37963/; https://doi.org/10.5194/tcd-9-2655-2015; https://hdl.handle.net/10013/epic.45550

The widely-used detailed SNOWPACK model has undergone constant development over the years. A notable recent extension is the introduction of a Richards Equation (RE) solver as an alternative for the bucket-type approach for describing water transport in the snow and soil layers. In addition, continuous updates of snow settling and new snow density parametrisations have changed model behaviour. This study presents a detailed evaluation of model performance against a comprehensive multi-year data set from Weissfluhjoch near Davos, Switzerland. The data set is collected by automatic meteorological and snowpack measurements and manual snow profiles. During the main winter season, snow height (RMSE: <4.2 cm), snow water equivalent (SWE, RMSE: <40 mm w.e.), snow temperature distributions (typical deviation with measurements: <1.0 °C) and snow density (typical deviation with observations: <50 kg m−3) as well as their temporal evolution are well simulated in the model and the influence of the two water transport schemes is small. The RE approach reproduces internal differences over capillary barriers but fails to predict enough grain growth since the growth routines have been calibrated using the bucket scheme in the original SNOWPACK model. The agreement in both density and grain size is sufficient to parametrise the hydraulic properties. In the melt season, a more pronounced underestimation of typically 200 mm w.e. in SWE is found. The discrepancies between the simulations and the field data are generally larger than the differences between the two water transport schemes. Nevertheless, the detailed comparison of the internal snowpack structure shows that the timing of internal temperature and water dynamics is adequately and better represented with the new RE approach when compared to the conventional bucket scheme. On the contrary, the progress of the meltwater front in the snowpack as detected by radar and the temporal evolution of the vertical distribution of melt forms in manually observed snow ...