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Snow albedo snowmelt rad #156

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Snow albedo snowmelt rad #156

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7e8d12c
Fix missing snow albedo component snow melt
Aug 28, 2024
418d84f
Added small comments related to the units.
Sep 18, 2024
89c7148
Added comment with names as suggested by Raj.
aranhax Sep 19, 2024
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31 changes: 29 additions & 2 deletions cwatm/hydrological_modules/snow_frost.py
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@
# -------------------------------------------------------------------------

from cwatm.management_modules.data_handling import *
import numpy as np

class snow_frost(object):

Expand Down Expand Up @@ -203,6 +204,13 @@ def initial(self):
# initial snow depth in elevation zones A, B, and C, respectively [mm]
self.var.SnowCover = np.sum(self.var.SnowCoverS,axis=0) / self.var.numberSnowLayersFloat + globals.inZero


# SnowAge
self.var.SnowAge = []
for i in range(self.var.numberSnowLayers):
self.var.SnowAge.append(globals.inZero)


# if the EMO dataset for meteo data is used, only rd is given, so we need additional data like elevation and latitude
# it is loaded in evapopot, but not always evapopot is calculated
if self.var.only_radiation:
Expand Down Expand Up @@ -345,20 +353,37 @@ def dynamic(self):
# radiation part from evaporationPot -> snowmelt has now a temperature part and a radiation part
# from Erlandsen et al. Hydrology Research 52.2 2021
if self.var.snowmelt_radiation:
# R Shrestha and A. Lima: added albedo decay as a function of snow age based on VIC model (Liang et al., 1994)
nosnowtoday = (SnowS<0.01).astype(int)
# if snowday -> snowage = 0 otherwise it is added up
self.var.SnowAge[i] = self.var.SnowAge[i] * nosnowtoday + nosnowtoday

# if it melts snow is decaying faster - snow decay from
# Livneh et al 2010 https://doi.org/10.1175/2009JHM1174.1
SnowAlb = np.where(TavgS >= self.var.TempSnow,
np.maximum((0.85 * 0.82 ** (self.var.SnowAge[i] ** 0.46)),
0.4),
np.maximum((0.85 * 0.94 ** (self.var.SnowAge[i] ** 0.58)),
0.4))

SnowAlb = np.minimum(SnowAlb, 0.85)
# For radiation (RNup, Rsdl, Rsds) there is a conversion from W/m2 to MJ/m2/d
RNup = 4.903E-9 * (TavgS + 273.16) ** 4
# if only radiation is given like in the EMO meteo dataset:
if self.var.only_radiation:
RLN = RNup * RSNet
else:
RLN = RNup - self.var.Rsdl
RN = (self.var.Rsds - RLN) / 334.0

RN = (self.var.Rsds* (1 - SnowAlb) - RLN) / 334.0
# latent heat of fusion = 0.334 mJKg-1 * desity of water = 1000 khm-3

SnowMeltS = (TavgS - self.var.TempMelt) * SeasSnowMeltCoef + self.var.SnowMeltRad * RN
SnowMeltS = SnowMeltS * (1 + 0.01 * RainS) * self.var.DtDay
else:
# without radiation
SnowMeltS = (TavgS - self.var.TempMelt) * SeasSnowMeltCoef * (1 + 0.01 * RainS) * self.var.DtDay

SnowMeltS = np.maximum(SnowMeltS, globals.inZero)

# for which layer the ice melt is calculated with the middle temp.
Expand All @@ -374,7 +399,9 @@ def dynamic(self):
# Check snowcover and snowmelt
IceMeltS = np.maximum(IceMeltS, globals.inZero)

SnowIceMeltS = np.maximum(np.minimum(SnowMeltS + IceMeltS + snowIceM_surplus, self.var.SnowCoverS[i]), globals.inZero)
SnowIceMeltS = np.maximum(np.minimum(SnowMeltS + IceMeltS + snowIceM_surplus,
self.var.SnowCoverS[i]),
globals.inZero)

# snowIceM_surplus: each elevation band snow melt potential is collected -> one way to melt additianl snow which might
# be colleted in the valley because of snow retribution
Expand Down
1 change: 1 addition & 0 deletions cwatm/metaNetcdf.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -478,6 +478,7 @@
<metanetcdf varname="IceMeltCoef" unit="-" standard_name="" long_name="" description="Ice melt coefficnet - default 0.007" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="TempMelt" unit="deg C" standard_name="" long_name="" description="Average temperature at which snow melts" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="SnowCoverS" unit="m" standard_name="" long_name="" description="snow cover for each layer" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="SnowAge" unit="d" standard_name="" long_name="" description="Age of snow" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="Kfrost" unit="m-1" standard_name="" long_name="" description="Snow depth reduction coefficient, (HH, p. 7.28)" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="Afrost" unit="-" standard_name="" long_name="" description="Daily decay coefficient, (Handbook of Hydrology, p. 7.28)" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="FrostIndexThreshold" unit="-" standard_name="" long_name="" description="Degree Days Frost Threshold (stops infiltration, percolation and capillary rise)" title="CWATM" author="IIASA WAT" />
Expand Down
1 change: 1 addition & 0 deletions cwatm/variable_documentation/metaNetcdf.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -697,6 +697,7 @@
<metanetcdf varname="IceMeltCoef" unit="-" standard_name="" long_name="" description="Ice melt coefficnet - default 0.007" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="TempMelt" unit="C" standard_name="" long_name="" description="Average temperature at which snow melts" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="SnowCoverS" unit="m" standard_name="" long_name="" description="snow cover for each layer" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="SnowAge" unit="d" standard_name="" long_name="" description="Age of snow" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="Kfrost" unit="m-1" standard_name="" long_name="" description="Snow depth reduction coefficient, (HH, p. 7.28)" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="Afrost" unit="-" standard_name="" long_name="" description="Daily decay coefficient, (Handbook of Hydrology, p. 7.28)" title="CWATM" author="IIASA WAT" />
<metanetcdf varname="FrostIndexThreshold" unit="-" standard_name="" long_name="" description="Degree Days Frost Threshold (stops infiltration, percolation and capillary rise)" title="CWATM" author="IIASA WAT" />
Expand Down