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Added snow albedo function for snowmelt radiation #133

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Added snow albedo function for snowmelt radiation #133

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10 changes: 9 additions & 1 deletion 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 pandas as pd

class snow_frost(object):

Expand Down Expand Up @@ -281,9 +282,16 @@ 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: added albedo decay as a function of snow age based on VIC model (Liang et al., 1994), Minimum snowfall to refresh snow albedo [10 mm/d]
# max snow albedo 0.85, min 0.50 (0.23 vegetation canopy albedo)
sn0=pd.Series((SnowS<0.01).astype(int))
sngrp = sn0.eq(0).cumsum()
SnowAge = sn0.eq(1).groupby(sngrp).cumsum().to_numpy()
#Different SnowAlb decay coefficient under frozen and melting conditions based on TempSnow, VIC uses snow temperature not TavgS.
SnowAlb = np.where(SnowAge >= 1, np.where(TavgS >= self.var.TempSnow, np.maximum((0.85 * 0.82 ** (SnowAge ** 0.46)), 0.5), np.maximum((0.85 * 0.94 ** (SnowAge ** 0.58)), 0.5)), 0.85)
RNup = 4.903E-9 * (TavgS + 273.16) ** 4
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
Expand Down