Snow parameterizations

struct FractionalSnowCover{NF} <: Terrarium.AbstractSnowCover{NF}

Simple fractional snow cover parameterization f_snow = W_snow/(W_snow + W_ref) where W_snow is the current snow water equivalent (SWE) within any given finite area and W_ref is the reference SWE at which the area would be expected to be 50% covered. The function is smooth and differentiable, with f_snow → 0 as W_snow → 0 and f_snow → 1 as W_snow → ∞.

Default SWE level for half_coverage is set to 0.01 m following [11].

Properties:

• half_coverage::Any: Reference snow water equivalent level W_ref

References

• [11] Douville et al., Climate Dynamics (1995)

compute_snow_cover_fraction(
    cover::FractionalSnowCover{NF},
    swe
) -> Any

Sub-grid snow-covered area fraction f_snow = W_snow/(W_snow + W_ref) ∈ [0,1) from the snow water equivalent W_snow [m] and the reference level W_ref (half_coverage), clamping negative SWE (which can occur transiently in the prognostic state) to zero cover.

struct ConstantSnowDensity{NF} <: Terrarium.AbstractSnowDensity{NF}

Constant, spatially homogeneous bulk snow density ρ_snow. This is the default (and currently only) snow density scheme for SingleLayerSnow. Default bulk snow density follows [12].

Properties:

• density::Any: Bulk snow density ρ_snow

References

• [12] Westermann et al., Geoscientific Model Development (2016)

snow_density(snow::SingleLayerSnow) -> Any

Bulk snow density ρ_snow [kg/m³] of the snowpack, delegating to the process's density scheme.

compute_snow_depth(
    _::Terrarium.AbstractSnow,
    W_snow,
    ρ_snow,
    ρ_w
) -> Any

Snow layer depth d_snow = W_snow·ρ_w/ρ_snow [m], converting the water-equivalent depth W_snow [m] to the physical snow depth using the water density ρ_w and the bulk snow density ρ_snow.

struct PowerLawSnowThermalConductivity{NF} <: Terrarium.AbstractSnowThermalConductivity{NF}

Power law parameterization for snow thermal conductivity as a function of density following [13, Eq. (34)].

Properties:

• conductivity_coefficient::Any: Coefficient a in the thermal conductivity power law κ = a·(ρ_snow/ρ_w)^b

• conductivity_exponent::Any: Exponent b in the thermal conductivity power law κ = a·(ρ_snow/ρ_w)^b

References

• [13] Yen et al. 1981

struct LogarithmicSnowThermalConductivity{NF} <: Terrarium.AbstractSnowThermalConductivity{NF}

Logarithmic snow thermal conductivity parameterization of [14].

Properties:

• scale::Any

• shift::Any

References

• [14]

struct QuadraticSnowThermalConductivity{NF} <: Terrarium.AbstractSnowThermalConductivity{NF}

Piecewise quadratic snow thermal conductivity parameterization of [14]. Default conductivity of ice from [15].

Properties:

• func_hi::Terrarium.QuadraticFunction

• func_lo::Terrarium.QuadraticFunction

• threshold::Any

• κ_max::Any

References

• [14] Sturm et al., Journal of Glaciology (1997)
• [15] Weller & Schwerdtfeger, Journal of Glaciology (1971)

compute_thermal_conductivity(
    snow::SingleLayerSnow,
    constants::MaterialConstants,
    ρ_snow
) -> Any

Bulk snow thermal conductivity κ_snow [W/m/K], delegating to the process's thermal conductivity scheme with the bulk density ρ_snow.

struct ConstantSnowHydraulics{NF} <: Terrarium.AbstractSnowHydraulics{NF}

Constant, spatially homogeneous snow hydraulic properties: a saturated hydraulic conductivity K_sat and a capillary retention L_c, setting the Darcy-type meltwater outflow (see compute_meltwater_outflow). Default values follow [3].

Properties:

• saturated_conductivity::Any: Hydraulic conductivity at saturation

• capillary_retention::Any: Capillary retention liq_c: liquid fraction held against gravity before meltwater drains

References

• [3] Tarboton, Chowdhury and Jackson (1994)

compute_snow_properties!(
    out,
    i,
    j,
    grid,
    fields,
    snow::SingleLayerSnow,
    constants::PhysicalConstants
)

Compute the snow depth, cover fraction, and thermal conductivity at grid cell i, j.