add cal_snow_density

Author: kongdd

Diff for: src/BEPS/Base/snow_densty.jl

@@ -0,0 +1,49 @@
+# LoTmpDnsTruncatedAnderson1976
+"""
+    snow_density(Ta::Float64, U10::Float64=NaN; tfrz=0.0, method="LoTmpDnsSlater2017")
+
+Calculate the density of new snow
+
+"Snow fraction depends on the density of snow in CLM4. A 10 cm snowpack has f_snow=1 when density is low
+(50–100 kg m–3), such as may be found in fresh snow, and a smaller snow fraction (f_snow = 0.76)
+when density is high (400 kg m–3)" -- Bonan 2019, P148
+
+Snow compacts over time, increasing to a density of 100–500 kg m–3.
+
+# Reference
+
+- van Kampenhout et al. 2017
+
+- CLM5, <https://github.com/ESCOMP/CTSM/blob/07051e3758addf2f9753d520823be9ebcbfec0aa/src/biogeophys/SnowHydrologyMod.F90#L3729-L3747>
+
+# Examples
+```julia
+Ta = -100.:50
+ρ_snow = snow_density.(Ta, 2.0)
+ρ_snow_chen = @. 67.9 + 51.3 * exp(Ta / 2.6)
+
+# using Plots
+# plot(Ta, ρ_snow)
+# plot!(Ta, ρ_snow_chen)
+```
+"""
+function cal_snow_density(Ta::Float64, U10::Float64=NaN; tfrz=0.0, method="LoTmpDnsSlater2017")
+  if Ta > tfrz + 2.0
+    ρ_snow = 50.0 + 1.7 * (17.0)^1.5
+  elseif Ta > tfrz - 15.0
+    ρ_snow = 50.0 + 1.7 * (Ta - tfrz + 15.0)^1.5
+  else
+    if method == "LoTmpDnsTruncatedAnderson1976"
+      ρ_snow = 50.0
+    elseif method == "LoTmpDnsSlater2017"
+      # ρ_snow = -3.833 * (Ta - tfrz) - 0.0333 * (Ta - tfrz)^2
+      t_for_bifall_degC = Ta > tfrz - 57.55 ? (Ta - tfrz) : -57.55
+      ρ_snow = -(50.0 / 15.0 + 0.0333 * 15.0) * t_for_bifall_degC - 0.0333 * t_for_bifall_degC^2
+    end
+  end
+
+  if U10 > 0.1
+    ρ_snow = ρ_snow + (266.861 * ((1.0 + tanh(U10 / 2)) / 2.0)^8.8)
+  end
+  ρ_snow
+end

Diff for: src/BEPS/evaporation_soil.jl

@@ -7,7 +7,7 @@ Esoil: evaporation from soil
 function evaporation_soil_jl(Tair::FT, Tg::FT, RH::FT, Rn_g::FT, Gheat_g::FT,
   # perc_snow_g::Ref{FT}, 
   perc_snow::Layer3{FT}, 
-  depth_water, depth_snow,
+  depth_water::FT, depth_snow::FT,
   # depth_water::Ref{FT}, depth_snow::Ref{FT},
   mass_water_g::FT, mass_snow::Layer3{FT},
   ρ_snow::FT, swc_g::FT, porosity_g::FT) where {FT<:Real}