Snow#
Note
Simulation of the snow dynamics is calculated such that each \(0.5° \times 0.5°\) grid cell is subdivided into 100 non-localized subgrids that are assigned different land surface elevations according to GTOPO30 (U.S. Geological Survey, 1996) [1]. The daily temperature of each subgrid is calculated from the daily temperature at the \(0.5° \times 0.5°\) cell by applying an adiabatic lapse rate of 0.6 \(°C/100m\) [2]. The daily snow water balance is computed for each of the subcells such that within a \(0.5° \times 0.5°\) cell there may be subcells with and without snow cover or snowfall [3]. Subgrid values are then aggregated to \(0.5° \times 0.5°\) cell values. See section 4.3 of Müller Schmied et al 2021 [3].
Water balance#
Snow storage \({S}_{sn}\) \([mm]\) is calculated as:
where \({P}_{sn}\) is the part of throughfall \(({P}_{t})\) that falls as snow \([mm/d]\), \(M\) is snowmelt \([mm/d]\) and \({E}_{sn}\) is sublimation \([mm/d]\).
Note
Snow storage is also corrected with land area fraction.
Inflows#
Snow fall from throughfall \({P}_{sn}\) is calculated as:
where \(T\) is daily air temperature \([°C]\), and \({T}_{f}\) is snow freeze temperature, set to \(0 °C\). To prevent excessive snow accumulation, when snow storage \({S}_{sn}\) reaches \(1000 mm\) in a subcell, the temperature in this subcell is increased to the temperature in the highest subcell with a temperature above \({T}_{f}\) [2].
Outflows#
Snow melt \({M}\) is calculated with a land-cover-specific degreeday factor \({D}_{F}\) \([{mmd^−1} {°C^-1})\) (Table C2) [3] when the temperature \(T\) in a subgrid surpasses melting temperature \(T_m = 0 (°C)\) as:
Sublimation \({E}_{sn}\) is calculated as the fraction of \({E}_{pot}\) that remains available after \({E}_{c}\). For calculating \({E}_{pot}\), land-cover-specific albedo values are used if \({S}_{sn}\) surpasses \(3 mm\) in the \(0.5° \times 0.5°\) cell (Table C2) [3]. See potential evapotranspiration under Potential evaporation and canopy evapotranspiration under Canopy evaporation.