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snowpack_code.f
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snowpack_code.f
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c snowpack_code.f
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE SNOWPACK_CODE(nx,ny,Tair_grid,rh_grid,ro_nsnow,
& dt,swe_depth,Tsfc,snow_d,prec_grid,runoff,Qm,rain,
& sprec,iter,w_balance,sum_prec,sum_runoff,xro_snow,
& undef,ro_snow,ro_snow_grid,soft_snow_d,sum_sprec,
& snow_depth,windspd_grid,Qsi_grid,sum_Qcs,canopy_int,
& Qcs,vegtype,forest_LAI,albedo,glacier_melt,
& canopy_unload,sum_unload,sum_glacmelt,run_snowtran,
& swemelt,d_canopy_int,sum_d_canopy_int,snow_d_init,
& sfc_pressure,Qe,sfc_sublim_flag,sum_sfcsublim,
& sum_swemelt,corr_factor,icorr_factor_index,swesublim,
& swe_depth_old,canopy_int_old,JJ,max_layers,melt_flag,
& ro_snowmax,tsls_threshold,dz_snow_min,tslsnowfall,
& change_layer,dy_snow,swe_lyr,ro_layer,T_old,gamma,
& multilayer_snowpack,seaice_run,seaice_conc,
& fc_param,t_avg)
implicit none
include 'snowmodel.inc'
integer nx,ny,iter,i,j,max_iter
integer max_layers,multilayer_snowpack,k,n_tsteps_in_day,irec
integer JJ(nx_max,ny_max)
integer melt_flag(nx_max,ny_max,nz_max)
real ro_snowmax,tsls_threshold,dz_snow_min,Cp_snow,
& fc_param,t_avg
real tslsnowfall(nx_max,ny_max)
real change_layer(nx_max,ny_max)
real dy_snow(nx_max,ny_max,nz_max)
real swe_lyr(nx_max,ny_max,nz_max)
real ro_layer(nx_max,ny_max,nz_max)
real T_old(nx_max,ny_max,nz_max)
real gamma(nx_max,ny_max,nz_max)
real layerFlux(nx_max,ny_max,nz_max)
real ml_ret(nx_max,ny_max,nz_max)
real liqfracml(nx_max,ny_max,nz_max)
real icefracml(nx_max,ny_max,nz_max)
integer melt_flag_z(nz_max)
real dy_snow_z(nz_max)
real swe_lyr_z(nz_max)
real ro_layer_z(nz_max)
real T_old_z(nz_max)
real gamma_z(nz_max)
c real layerFlux_z(nz_max)
real ml_ret_z(nz_max)
c real liqfrac_z(nz_max)
c real icefrac_z(nz_max)
real Tair_grid(nx_max,ny_max)
real rh_grid(nx_max,ny_max)
real prec_grid(nx_max,ny_max)
real windspd_grid(nx_max,ny_max)
real Qsi_grid(nx_max,ny_max)
real vegtype(nx_max,ny_max)
real albedo(nx_max,ny_max)
real glacier_melt(nx_max,ny_max)
real canopy_unload(nx_max,ny_max)
real sum_unload(nx_max,ny_max)
real sum_glacmelt(nx_max,ny_max)
real sum_swemelt(nx_max,ny_max)
real swemelt(nx_max,ny_max)
real swesublim(nx_max,ny_max)
real snow_d_init(nx_max,ny_max)
real swe_depth_old(nx_max,ny_max)
real canopy_int_old(nx_max,ny_max)
real seaice_conc(nx_max,ny_max)
real ro_nsnow(nx_max,ny_max),snow_d(nx_max,ny_max),
& runoff(nx_max,ny_max),rain(nx_max,ny_max),
& sprec(nx_max,ny_max),w_balance(nx_max,ny_max),
& sum_prec(nx_max,ny_max),sum_runoff(nx_max,ny_max),
& xro_snow(nx_max,ny_max),sfc_pressure(nx_max,ny_max),
& ro_snow_grid(nx_max,ny_max),swe_depth(nx_max,ny_max),
& Tsfc(nx_max,ny_max),Qm(nx_max,ny_max),
& soft_snow_d(nx_max,ny_max),sum_sprec(nx_max,ny_max),
& ro_snow,snow_depth(nx_max,ny_max),sum_Qcs(nx_max,ny_max),
& canopy_int(nx_max,ny_max),Qcs(nx_max,ny_max),
& d_canopy_int(nx_max,ny_max),sum_d_canopy_int(nx_max,ny_max),
& Qe(nx_max,ny_max),sum_sfcsublim(nx_max,ny_max)
real dt,undef,Cp,xLf,Tf,A1,A2,ro_water,xLs,ro_ice,Twb,
& run_snowtran,sfc_sublim_flag,seaice_run,Cp_water
real corr_factor(nx_max,ny_max,max_obs_dates+1)
integer icorr_factor_index(max_time_steps)
integer nftypes
parameter (nftypes=5)
real forest_LAI(nftypes)
print *,' solving the snow-cover evolution'
c Define the constants used in the computations.
CALL CONSTS_SNOWPACK(Cp,xLs,ro_ice,xLf,Tf,A1,A2,ro_water,
& Cp_snow,ro_snowmax,Cp_water)
c Run the snowpack evolution sub-model.
do j=1,ny
do i=1,nx
c Extract the vertical column for this i,j point, and send it
c to the subroutine. *** Note that I should use f95, then I would
c not have to do this (I could pass in subsections of the arrays).
if (multilayer_snowpack.eq.1) then
do k=1,nz_max
melt_flag_z(k) = melt_flag(i,j,k)
dy_snow_z(k) = dy_snow(i,j,k)
swe_lyr_z(k) = swe_lyr(i,j,k)
ro_layer_z(k) = ro_layer(i,j,k)
T_old_z(k) = T_old(i,j,k)
gamma_z(k) = gamma(i,j,k)
c J.PFLUG
c variables for multilayer percolation investigation
c layerFlux_z(k) = layerFlux(i,j,k)
ml_ret_z(k) = ml_ret(i,j,k)
c liqfrac_z(k) = liqfracml(i,j,k)
c icefrac_z(k) = icefracml(i,j,k)
c END J.PFLUG
enddo
endif
CALL SNOWPACK_CORE(Twb,Tf,Tair_grid(i,j),rh_grid(i,j),xLs,
& Cp,sfc_pressure(i,j),ro_nsnow(i,j),dt,ro_snow,
& swe_depth(i,j),Tsfc(i,j),A1,A2,snow_d(i,j),ro_water,
& ro_ice,prec_grid(i,j),runoff(i,j),Qm(i,j),xLf,rain(i,j),
& sprec(i,j),iter,w_balance(i,j),sum_prec(i,j),
& sum_runoff(i,j),xro_snow(i,j),undef,
& soft_snow_d(i,j),sum_sprec(i,j),ro_snow_grid(i,j),
& snow_depth(i,j),windspd_grid(i,j),Qsi_grid(i,j),
& sum_Qcs(i,j),canopy_int(i,j),Qcs(i,j),vegtype(i,j),
& forest_LAI,albedo(i,j),canopy_unload(i,j),
& sum_unload(i,j),sum_glacmelt(i,j),run_snowtran,
& swemelt(i,j),d_canopy_int(i,j),sum_d_canopy_int(i,j),
& snow_d_init(i,j),Qe(i,j),glacier_melt(i,j),
& sfc_sublim_flag,sum_sfcsublim(i,j),sum_swemelt(i,j),
& corr_factor(i,j,-icorr_factor_index(iter)),
& icorr_factor_index(iter),swesublim(i,j),
& swe_depth_old(i,j),canopy_int_old(i,j),JJ(i,j),
& max_layers,melt_flag_z,ro_snowmax,tsls_threshold,
& dz_snow_min,tslsnowfall(i,j),change_layer(i,j),dy_snow_z,
& swe_lyr_z,ro_layer_z,T_old_z,gamma_z,multilayer_snowpack,
& Cp_snow,seaice_run,fc_param,t_avg,Cp_water,ml_ret_z)
c Re-build the 3-D arrays. See note above about using f95 to avoid this.
if (multilayer_snowpack.eq.1) then
do k=1,nz_max
melt_flag(i,j,k) = melt_flag_z(k)
dy_snow(i,j,k) = dy_snow_z(k)
swe_lyr(i,j,k) = swe_lyr_z(k)
ro_layer(i,j,k) = ro_layer_z(k)
T_old(i,j,k) = T_old_z(k)
gamma(i,j,k) = gamma_z(k)
c layerFlux(i,j,k) = layerFlux_z(k)
ml_ret(i,j,k) = ml_ret_z(k)
c liqfracml(i,j,k) = liqfrac_z(k)
c icefracml(i,j,k) = icefrac_z(k)
enddo
endif
enddo
enddo
if (run_snowtran.eq.0.0) then
do j=1,ny
do i=1,nx
swe_depth_old(i,j) = swe_depth(i,j)
canopy_int_old(i,j) = canopy_int(i,j)
enddo
enddo
endif
c Read in the sea ice concentration. These are daily data, so
c first calculate which record in the data file this time step
c corresponds to.
if (seaice_run.ne.0.0) then
n_tsteps_in_day = nint(86400.0 / dt)
if (mod(iter-1,n_tsteps_in_day).eq.0) then
irec = int((real(iter) - 0.5) * dt / 86400.0) + 1
print *,'sea ice irec =',irec
read (445,rec=irec) ((seaice_conc(i,j),i=1,nx),j=1,ny)
endif
endif
c If this simulation is not running SnowTran-3D, then zero out
c the ocean grid cells that have no sea ice here. If it is
c running with SnowTran-3D, then do this in the SnowTran-3D
c subroutine.
if (run_snowtran.eq.0.0) then
if (seaice_run.ne.0.0) then
CALL ZERO_SEAICE_SNOW(nx,ny,snow_depth,ro_snow_grid,
& ro_snow,swe_depth,swe_depth_old,canopy_int_old,JJ,
& tslsnowfall,dy_snow,swe_lyr,ro_layer,T_old,
& multilayer_snowpack,tsls_threshold,seaice_conc)
endif
endif
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE SNOWPACK_CORE(Twb,Tf,Tair,rh,xLs,
& Cp,sfc_pressure,ro_nsnow,dt,ro_snow,
& swe_depth,Tsfc,A1,A2,snow_d,ro_water,
& ro_ice,prec,runoff,Qm,xLf,rain,
& sprec,iter,w_balance,sum_prec,
& sum_runoff,xro_snow,undef,
& soft_snow_d,sum_sprec,ro_snow_grid,
& snow_depth,windspd,Qsi,
& sum_Qcs,canopy_int,Qcs,vegtype,
& forest_LAI,albedo,canopy_unload,
& sum_unload,sum_glacmelt,run_snowtran,
& swemelt,d_canopy_int,sum_d_canopy_int,
& snow_d_init,Qe,glacier_melt,
& sfc_sublim_flag,sum_sfcsublim,sum_swemelt,
& corr_factor,
& icorr_factor_index,swesublim,
& swe_depth_old,canopy_int_old,JJ,
& max_layers,melt_flag,ro_snowmax,tsls_threshold,
& dz_snow_min,tslsnowfall,change_layer,dy_snow,
& swe_lyr,ro_layer,T_old,gamma,multilayer_snowpack,
& Cp_snow,seaice_run,fc_param,t_avg,
& Cp_water,ml_ret)
implicit none
include 'snowmodel.inc'
integer iter,icorr_factor_index
integer JJ,max_layers,multilayer_snowpack
real ro_snowmax,tsls_threshold,dz_snow_min,tslsnowfall,Cp_snow,
& Cp_water
integer melt_flag(nz_max)
real change_layer
real dy_snow(nz_max)
real swe_lyr(nz_max)
real ro_layer(nz_max)
real T_old(nz_max)
real gamma(nz_max)
real ml_ret(nz_max)
real Twb,Tf,Tair,rh,xLs,Cp,ro_nsnow,dt,ro_snow,swe_depth,
& Tsfc,A1,A2,snow_d,ro_water,ro_ice,prec,runoff,Qm,xLf,rain,
& sprec,w_balance,sum_prec,sum_runoff,xro_snow,undef,
& soft_snow_d,sum_sprec,ro_snow_grid,snow_depth,sprec_grnd,
& windspd,Qsi,sum_Qcs,canopy_int,Qcs,canopy_unload,
& vegtype,albedo,glacier_melt,sum_unload,sum_glacmelt,
& run_snowtran,swemelt,d_canopy_int,sfc_pressure,
& sum_d_canopy_int,snow_d_init,Qe,sfc_sublim_flag,
& sum_sfcsublim,sum_swemelt,corr_factor,swesublim,
& swe_depth_old,canopy_int_old,sprec_grnd_ml,seaice_run,
& mLayerVolFracLiqTrial,fc_param,t_avg
integer nftypes
parameter (nftypes=5)
real forest_LAI(nftypes)
c Calculate the canopy sublimation, loading and unloading. Note
c that here I have assumed that evergreen trees are type 1.
if (vegtype.le.5.0) then
CALL CANOPY_SNOW(rh,Tair,windspd,Qsi,sum_Qcs,albedo,
& canopy_int,sprec,Qcs,dt,canopy_unload,
& forest_LAI(nint(vegtype)),sum_unload,d_canopy_int,
& sum_d_canopy_int)
sprec_grnd = sprec + canopy_unload - d_canopy_int
sprec_grnd_ml = sprec - d_canopy_int
else
Qcs = 0.0
sprec_grnd = sprec
sprec_grnd_ml = sprec
endif
c Solve for the wet bulb temperature.
CALL SOLVEWB(Twb,Tf,Tair,rh,xLs,Cp,sfc_pressure)
c Compute the new snow density.
CALL NSNOWDEN(ro_nsnow,Twb,Tf,dt)
c Call the multi-layer snowpack model.
if (multilayer_snowpack.eq.1) then
CALL MULTI_LAYER_SNOW(JJ,ro_layer,Tf,dt,ro_water,
& ro_ice,T_old,dy_snow,swe_lyr,Qm,ro_snowmax,rain,
& xLf,Cp_snow,melt_flag,runoff,tslsnowfall,ro_nsnow,
& sprec,Tsfc,tsls_threshold,gamma,max_layers,change_layer,
& dz_snow_min,snow_depth,swe_depth,undef,canopy_unload,
& vegtype,glacier_melt,sum_glacmelt,sum_swemelt,snow_d,
& Qe,sfc_sublim_flag,sum_sfcsublim,soft_snow_d,ro_snow,
& sum_sprec,sprec_grnd_ml,sum_prec,prec,sum_runoff,
& ro_snow_grid,xro_snow,swesublim,A1,A2,
& fc_param,Cp_water,ml_ret,icorr_factor_index,corr_factor)
c Call the original single-layer snowpack model.
else
c Compute the snow density change due to settling.
CALL DDENSITY(ro_snow_grid,swe_depth,Tf,Tsfc,dt,A1,A2,
& snow_depth,ro_water,ro_ice)
c Compute the melt, rain, and snow contributions to modifying
c the snowpack depth, density, and snow water equivalent.
CALL SNOWPACK(swe_depth,snow_d,ro_snow_grid,
& prec,ro_water,ro_nsnow,runoff,Qm,xLf,dt,rain,sprec,
& sum_prec,sum_runoff,soft_snow_d,sum_sprec,ro_snow,
& snow_depth,sprec_grnd,vegtype,glacier_melt,sum_glacmelt,
& swemelt,canopy_unload,Qe,sfc_sublim_flag,sum_sfcsublim,
& sum_swemelt,corr_factor,icorr_factor_index,swesublim,
& ro_snowmax)
c Post process the data for output.
CALL POSTPROC(ro_snow_grid,xro_snow,snow_depth,undef)
endif
c Perform a water balance check (see notes in this subroutine).
if (seaice_run.eq.0.0) then
if (run_snowtran.eq.0.0) then
CALL WATERBAL_SNOWPACK(w_balance,prec,Qcs,runoff,
& d_canopy_int,swe_depth,glacier_melt,swe_depth_old,iter,
& swesublim,canopy_unload,canopy_int_old,canopy_int)
c CALL WATERBAL_SNOWPACK_sums(w_balance,sum_prec,sum_Qcs,
c & sum_runoff,canopy_int,swe_depth,sum_glacmelt,iter,
c & snow_d_init,ro_snow,ro_water,sum_sfcsublim)
endif
endif
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE CANOPY_SNOW(rh,Tair,windspd,Qsi,sum_Qcs,albedo,
& canopy_int,sprec,Qcs,dt,canopy_unload,
& forest_LAI,sum_unload,d_canopy_int,
& sum_d_canopy_int)
implicit none
real rh,Tair,windspd,V_s,Qsi,forest_LAI,dt,xImax,canopy_int,
& d_canopy_int,Qcs,Ce,sprec,C_0,unload_melt,canopy_unload,
& sum_Qcs,albedo,sum_unload,sum_d_canopy_int
c Note that all of this must deal with the (kg/m2)=(mm), => (m)
c issues. Precip is in (m), all of these equations are in
c (kg/m2), and I want the outputs to be in (m).
c Compute the sublimation loss rate coefficient for canopy snow.
CALL SUBLIM_COEF(rh,Tair,windspd,V_s,Qsi,albedo)
c Maximum interception storage.
xImax = 4.4 * forest_LAI
c Change in canopy load due to snow precipitation during this time
c step. Convert the canopy interception to mm.
canopy_int = 1000.0 * canopy_int
d_canopy_int = 0.7 * (xImax - canopy_int) *
& ( 1.0 - exp((- sprec)*1000.0/xImax))
c Update the interception load.
canopy_int = canopy_int + d_canopy_int
c Canopy exposure coefficient.
if (canopy_int.eq.0.0) then
Ce = 0.0
else
c Pomeroy's k_c value
c Ce = 0.0114 * (canopy_int/xImax)**(-0.4)
c My k_c value.
Ce = 0.00995 * (canopy_int/xImax)**(-0.4)
endif
c Canopy sublimation (kg/m2), (a negative mumber). Make sure that
c you don't sublimate more than is available.
Qcs = Ce * canopy_int * V_s * dt
Qcs = -min(canopy_int,-Qcs)
c Remove the sublimated moisture from the canopy store.
canopy_int = canopy_int + Qcs
c Save the sublimation in (m).
Qcs = Qcs / 1000.0
sum_Qcs = sum_Qcs + Qcs
c Perform a second unloading due to melt. Assume an unloading rate
c of 5.0 mm/day/C.
C_0 = 5.0 / 86400.0
unload_melt = C_0 * max(0.0,Tair-273.16) * dt
unload_melt = min(canopy_int,unload_melt)
canopy_int = canopy_int - unload_melt
c Keep track of the unloaded snow that reached the ground during
c this time step (m) (this will add to the snow depth).
canopy_unload = unload_melt / 1000.0
d_canopy_int = d_canopy_int / 1000.0
c Save a summing array of this unloaded snow.
sum_unload = sum_unload + canopy_unload
c Save a summing array of the change in canopy load.
sum_d_canopy_int = sum_d_canopy_int + d_canopy_int
c Save the interception load for the next time step. Convert to m.
canopy_int = canopy_int / 1000.0
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE SUBLIM_COEF(rh,Tair,windspd,V_s,Qsi,albedo)
c Compute the sublimation loss rate coefficient for canopy snow.
implicit none
real pi,ro_ice,xM,R,R_dryair,vonKarman,visc_air,h_s,xlamdaT,
& D,ro_sat,sigma,V_s,radius,xmass,windspd,rh,Tair,Qsi,Sp,
& xN_r,xNu,xSh,top,bottom,omega,albedo
c Constants.
pi = 2.0 * acos(0.0)
ro_ice = 917.0
xM = 18.01
R = 8313.
R_dryair = 287.
vonKarman = 0.4
visc_air = 13.e-6
h_s = 2.838e6
xlamdaT = 0.024
c Particle radius.
radius = 5.0e-4
c Particle mass.
xmass = 4.0/3.0 * pi * ro_ice * radius**3
c Diffusivity of water vapor in the atmosphere.
D = 2.06e-5 * (Tair/273.)**(1.75)
c Saturation density of water vapor.
ro_sat = 0.622 / (R_dryair * Tair) *
& 611.15 * exp(22.452 * (Tair - 273.16) / (Tair - 0.61))
c Humidity deficit.
sigma = 0.01 * rh - 1.0
sigma = min(0.0,sigma)
sigma = max(-1.0,sigma)
c Reynolds, Nusselt, and Sherwood numbers.
xN_r = 2.0 * radius * windspd / visc_air
xNu = 1.79 + 0.606 * xN_r**(0.5)
xSh = xNu
c Solar radiation absorbed by the snow particle. Here assume that
c the general snow albedo is the same as the snow particle albedo.
Sp = pi * radius**2 * (1.0 - albedo) * Qsi
c Sublimation-loss rate coefficient for an ice sphere.
omega = ((h_s * xM)/(R * Tair) - 1.0) / (xlamdaT * Tair * xNu)
top = 2.0 * pi * radius * sigma - Sp * omega
bottom = h_s * omega + 1.0/(D * ro_sat * xSh)
V_s = (top/bottom)/xmass
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE WATERBAL_SNOWPACK(w_balance,prec,Qcs,runoff,
& d_canopy_int,swe_depth,glacier_melt,swe_depth_old,iter,
& swesublim,canopy_unload,canopy_int_old,canopy_int)
implicit none
integer iter
real w_balance,prec,Qcs,runoff,d_canopy_int,swe_depth_old,
& swe_depth,glacier_melt,swesublim,canopy_unload,canopy_int_old,
& canopy_int
c Note that the following balances should hold. These aren't quite
c right, but it is a place to start.
c Canopy Balance (forest):
c canopy = sprec - unload + Qcs ==> unload = sprec - canopy + Qcs
c
c Snowpack Balance (forest):
c swe_d = unload + rain - runoff ==>
c canopy + swe_d = sprec + rain + Qcs - runoff
c prec = sprec + rain
c sum_rain = sum_sprec - sum_prec
c
c Snowpack Balance (non-forest):
c swe_d = sprec + rain - runoff + subl + salt + susp + subgrid +
c glaciermelt
c
c Everywhere:
c w_balance = sum_prec + sum_Qcs - sum_runoff + sum_subl +
c sum_trans - canopy_int - swe_depth + sum_glacmelt
c
c The related variables that would need to be brought in are:
c d_canopy_int,sum_d_canopy_int,sum_unload
c This subroutine is called for the case where SnowTran-3D is not
c run. The subroutine WATERBAL_SNOWTRAN is used if the model
c simulation includes SnowTran-3D.
c w_balance = swe_depth_old - swe_depth + prec - runoff +
c & glacier_melt - swesublim + canopy_int_old - canopy_int -
c & d_canopy_int + Qcs + canopy_unload
c Do the snowpack.
c w_balance = swe_depth_old - swe_depth + prec - runoff -
c & glacier_melt - swesublim
c Do the canopy.
c w_balance = canopy_int_old - canopy_int + d_canopy_int +
c & Qcs - canopy_unload
c Do the snowpack and canopy store.
w_balance = swe_depth_old - swe_depth + prec - runoff +
& glacier_melt - swesublim + canopy_int_old - canopy_int +
& Qcs
if (abs(w_balance).gt.1.0e-5) then
print*,'water imbalance found, iter =',iter,' ',w_balance
print*,swe_depth_old,swe_depth,prec,runoff,glacier_melt,
& swesublim,canopy_int_old,canopy_int,Qcs
endif
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE WATERBAL_SNOWPACK_sums(w_balance,sum_prec,sum_Qcs,
& sum_runoff,canopy_int,swe_depth,sum_glacmelt,iter,
& snow_d_init,ro_snow,ro_water,sum_sfcsublim)
implicit none
integer iter
real w_balance,sum_prec,sum_Qcs,sum_runoff,canopy_int,
& swe_depth,sum_glacmelt,snow_d_init,ro_snow,ro_water,
& sum_sfcsublim
c Note that the following balances should hold. These aren't quite
c right, but it is a place to start.
c Canopy Balance (forest):
c canopy = sprec - unload + Qcs ==> unload = sprec - canopy + Qcs
c
c Snowpack Balance (forest):
c swe_d = unload + rain - runoff ==>
c canopy + swe_d = sprec + rain + Qcs - runoff
c prec = sprec + rain
c sum_rain = sum_sprec - sum_prec
c
c Snowpack Balance (non-forest):
c swe_d = sprec + rain - runoff + subl + salt + susp + subgrid +
c glaciermelt
c
c Everywhere:
c w_balance = sum_prec + sum_Qcs - sum_runoff + sum_subl +
c sum_trans - canopy_int - swe_depth + sum_glacmelt
c
c The related variables that would need to be brought in are:
c d_canopy_int,sum_d_canopy_int,sum_unload
c This subroutine is called for the case where SnowTran-3D is not
c run. The subroutine WATERBAL_SNOWTRAN is used if the model
c simulation includes SnowTran-3D.
w_balance = sum_prec + sum_Qcs - sum_runoff - canopy_int -
& swe_depth + sum_glacmelt + snow_d_init * ro_snow/ro_water -
& sum_sfcsublim
if (abs(w_balance).gt.1.0e-4)
& print*,'water imbalance found, iter =',iter,' ',w_balance
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc;cccccc
SUBROUTINE SNOWPACK(swe_depth,snow_d,ro_snow_grid,
& prec,ro_water,ro_nsnow,runoff,Qm,xLf,dt,rain,sprec,
& sum_prec,sum_runoff,soft_snow_d,sum_sprec,ro_snow,
& snow_depth,sprec_grnd,vegtype,glacier_melt,sum_glacmelt,
& swemelt,canopy_unload,Qe,sfc_sublim_flag,sum_sfcsublim,
& sum_swemelt,corr_factor,icorr_factor_index,swesublim,
& ro_snowmax)
implicit none
real ro_snowmax,runoff,Qm,swe_depth,potmelt,swemelt,dt,
& ro_water,xLf,snow_depth,ro_snow_grid,snow_d_melt,dz_water,
& soft_snow_d,prec,rain,snow_d,sum_sprec,sum_prec,
& sum_runoff,ro_nsnow,sprec,ro_snow,snow_d_new,sprec_grnd,
& vegtype,glacier_melt,sum_glacmelt,canopy_unload,Qe,
& xLsublim,potsublim,swesublim,snow_d_sublim,sfc_sublim_flag,
& sum_sfcsublim,sum_swemelt,corr_factor,potmelt_tmp
integer icorr_factor_index
runoff = 0.0
c SURFACE SUBLIMATION.
c Whether static-surface (non-blowing snow) sublimation is included
c in the model calculations is controlled by the sfc_sublim_flag.
c I am waiting for the flux-tower data Matthew and I are collecting
c in Alaska, to compare with the model simulations, before
c including this part of the model in all simulations.
c If the sfc_sublim_flag is turned on, the latent heat flux (Qe)
c calculated in ENBAL is used to add/remove snow from the snowpack.
c xLsublim = xLf + xLv = 2.5104x10^6 J/kg + 3.334x10^5 J/kg, and
c potsublim is in m swe.
if (swe_depth.gt.0.0 .and. sfc_sublim_flag.eq.1.0) then
if (Qe.lt.0.0) then
c Compute the snow-surface sublimation (m, swe).
xLsublim = 2.844e6
potsublim = (- dt) * Qe / (ro_water * xLsublim)
swesublim = min(potsublim,swe_depth)
c Save a summing array of the static surface snow sublimation.
sum_sfcsublim = sum_sfcsublim + swesublim
c Compute the change in snow depth. Assume that this sublimated
c snow does not change the snow density and does not change the
c soft snow depth. It only reduces the snow depth and the
c associated swe depth.
swe_depth = swe_depth - swesublim
if (swe_depth.eq.0.0) then
snow_depth = 0.0
else
snow_d_sublim = swesublim * ro_water / ro_snow_grid
snow_depth = snow_depth - snow_d_sublim
endif
else
swesublim = 0.0
endif
else
swesublim = 0.0
endif
c MELTING.
c If melting occurs, decrease the snow depth, and place the melt
c water in the 'runoff' variable. Keep track of the liquid water
c produced.
if (Qm.gt.0.0) then
c Compute the snow melt (m).
potmelt = dt * Qm / (ro_water * xLf)
c Account for any snowmelt data assimilation.
if (icorr_factor_index.lt.0.0) then
potmelt_tmp = potmelt * corr_factor
swemelt = min(potmelt_tmp,swe_depth)
c Handle the case of no snowmelt data assimilation.
else
swemelt = min(potmelt,swe_depth)
endif
c Compute any glacier or permanent snow-field melt (m water equiv.).
if (vegtype.eq.20.0) then
glacier_melt = potmelt - swemelt
else
glacier_melt = 0.0
endif
c Save a summing array of the glacier melt.
sum_glacmelt = sum_glacmelt + glacier_melt
c Save the runoff contribution.
runoff = runoff + glacier_melt
c Save a summing array of the snow melt.
sum_swemelt = sum_swemelt + swemelt
c Compute the change in snow depth.
snow_d_melt = swemelt * ro_water / ro_snow_grid
snow_depth = snow_depth - snow_d_melt
snow_depth = max(0.0,snow_depth)
c Compute the changes in snow density resulting from the melt.
c Assume that the melted snow is redistributed through the new
c snow depth up to a maximum density. Any additional melt water
c is added to the runoff.
if (snow_depth.eq.0.0) then
ro_snow_grid = ro_snowmax
runoff = runoff + swemelt
else
ro_snow_grid = swe_depth * ro_water / snow_depth
endif
if (ro_snow_grid.gt.ro_snowmax) then
dz_water = snow_depth *
& (ro_snow_grid - ro_snowmax) / ro_water
ro_snow_grid = ro_snowmax
swe_depth = snow_depth * ro_snow_grid / ro_water
runoff = runoff + dz_water
else
swe_depth = snow_depth * ro_snow_grid / ro_water
endif
soft_snow_d = 0.0
else
c These prevent values from the previous time step from being
c carried through to the next time step.
swemelt = 0.0
glacier_melt = 0.0
endif
c PRECIPITATION.
c Precipitation falling as rain on snow contributes to a snow
c density increase, precipitation falling as snow adds to the
c snow depth, and rain falling on bare ground contributes to the
c runoff.
c We have precipitation.
if (prec.gt.0.0) then
rain = prec - sprec
c We have rain.
if (rain.gt.0.0) then
c Rain on snow. Note that we can also have snow unloading here.
c Assume this unloading is wet as rain.
if (snow_depth.gt.0.0) then
swe_depth = swe_depth + rain + canopy_unload
ro_snow_grid = swe_depth * ro_water / snow_depth
if (ro_snow_grid.gt.ro_snowmax) then
dz_water = snow_depth * (ro_snow_grid - ro_snowmax) /
& ro_water
ro_snow_grid = ro_snowmax
swe_depth = snow_depth * ro_snow_grid / ro_water
runoff = runoff + dz_water
endif
c Rain on bare ground. Assume any unloading is as wet as rain.
else
runoff = runoff + rain + canopy_unload
endif
c We have snow precipitation (on either snow or bare ground).
else
swe_depth = swe_depth + sprec_grnd
snow_d_new = ro_water / ro_nsnow * sprec_grnd
snow_depth = snow_depth + snow_d_new
ro_snow_grid = ro_water * swe_depth / snow_depth
endif
c Here we handle the case where there is no precipitation, but
c there is snow falling from the canopy to the snowpack.
else
rain = 0.0
if (sprec_grnd.gt.0.0) then
swe_depth = swe_depth + sprec_grnd
snow_d_new = ro_water / ro_snow * sprec_grnd
snow_depth = snow_depth + snow_d_new
ro_snow_grid = ro_water * swe_depth / snow_depth
endif
endif
c The following are set up to be compatible with SnowTran-3D, and
c are in snow-depth units. The sum_sprec corrections are done
c in the SnowTran-3D code.
soft_snow_d = soft_snow_d + sprec_grnd * ro_water / ro_snow
snow_d = swe_depth * ro_water / ro_snow
c sum_sprec = sum_sprec + sprec_grnd * ro_water / ro_snow
sum_sprec = sum_sprec + sprec_grnd
c The following are in swe-depth units.
sum_prec = sum_prec + prec
sum_runoff = sum_runoff + runoff
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE DDENSITY(ro_snow_grid,swe_depth,Tf,Tsfc,dt,A1,A2,
& snow_depth,ro_water,ro_ice)
implicit none
real snow_depth,Tsg,Tf,Tsnow,Tsfc,ro_snow_grid,dt,A1,A2,
& swe_depth_star,ro_ice,ro_water,swe_depth
if (snow_depth.gt.0.0) then
c Assume that the snow-ground interface temperature is -1.0 C.
Tsg = Tf - 1.0
Tsnow = 0.5 * (Tsg + Tsfc)
swe_depth_star= 0.5 * swe_depth
ro_snow_grid = ro_snow_grid + dt *
& (A1 * swe_depth_star * ro_snow_grid *
& exp((- 0.08)*(Tf-Tsnow)) * exp((- A2)*ro_snow_grid))
ro_snow_grid = min(ro_ice,ro_snow_grid)
snow_depth = ro_water * swe_depth / ro_snow_grid
endif
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE SOLVEWB(xnew,Tf,Tair,rh,xLs,Cp,sfc_pressure)
implicit none
real A,B,C,ea,rh,Tair,Tf,tol,old,fprime,xLs,Cp,funct,xnew,
& sfc_pressure
integer maxiter,i
c Coeffs for saturation vapor pressure over water (Buck 1981).
c Note: temperatures for Buck`s equations are in deg C, and
c vapor pressures are in mb. Do the adjustments so that the
c calculations are done with temperatures in K, and vapor
c pressures in Pa.
c Over water.
A = 6.1121 * 100.0
B = 17.502
C = 240.97
c Over ice.
c A = 6.1115 * 100.0
c B = 22.452
c C = 272.55
c Atmospheric vapor pressure from relative humidity data.
ea = rh / 100.0 * A * exp((B * (Tair - Tf))/(C + (Tair - Tf)))
c Solve for the wet bulb temperature.
tol = 1.0e-2
maxiter = 20
old = Tair
do i=1,maxiter
fprime = 1.0 + xLs/Cp * 0.622/sfc_pressure * log(10.0) *
& 2353. * (10.0**(11.40 - 2353./old)) / old**2
funct = old - Tair + xLs/Cp * 0.622/sfc_pressure *
& (10.0**(11.40-2353./old) - ea)
xnew = old - funct/fprime
if (abs(xnew - old).lt.tol) return
old = xnew
end do
c If the maximum iterations are exceeded, send a message and set
c the wet bulb temperature to the air temperature.
write (*,102)
102 format('max iteration exceeded when solving for Twb')
xnew = Tair
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE NSNOWDEN(ro_nsnow,Twb,Tf,dt)
implicit none
real Twgmax,Tf,Twb,ro_nsnow,scalefact,dt,wt
Twgmax = Tf + 1.0
if (Twb.ge.258.16 .and. Twb.le.Twgmax) then
ro_nsnow = 50. + 1.7 * (Twb - 258.16)**1.5
elseif (Twb.lt.258.16) then
ro_nsnow = 50.0
else
ro_nsnow = 158.8
endif
c For one day time steps, this equation gives a new snow density at
c the end of the 24 hour period which is too low, by an approximate
c factor of X. Thus, for a daily time step, I scale the density by
c X before returning it to the main program.
scalefact = 1.0
if (dt.eq.86400.0) then
if (ro_nsnow.le.158.8) then
wt = 1.0 + (50.0 - ro_nsnow) / 108.8
ro_nsnow = wt * scalefact * ro_nsnow + ro_nsnow
ro_nsnow = min(158.8,ro_nsnow)
endif
endif
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE POSTPROC(ro_snow_grid,xro_snow,snow_depth,undef)
implicit none
real snow_depth,xro_snow,undef,ro_snow_grid
if (snow_depth.eq.0.0) then
xro_snow = undef
else
xro_snow = ro_snow_grid
endif
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE CONSTS_SNOWPACK(Cp,xLs,ro_ice,xLf,Tf,A1,A2,ro_water,
& Cp_snow,ro_snowmax,Cp_water)
implicit none
real Cp,xLs,ro_ice,xLf,Tf,A1,A2,ro_water,Cp_snow,ro_snowmax,
& Cp_water
Cp = 1004.
xLs = 2.500e6
ro_ice = 917.0
xLf = 3.34e5
Tf = 273.16
A1 = 0.0013
A2 = 0.021
ro_water = 1000.0
Cp_snow = 2106.
ro_snowmax = 550.0
Cp_water = 4180.0
return
end
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
SUBROUTINE MULTI_LAYER_SNOW(JJ,ro_layer,Tf,dt,ro_water,
& ro_ice,T_old,dy_snow,swe_lyr,Qm,ro_snowmax,rain,
& xLf,Cp_snow,melt_flag,runoff,tslsnowfall,ro_nsnow,
& sprec,Tsfc,tsls_threshold,gamma,max_layers,change_layer,
& dz_snow_min,snow_depth,swe_depth,undef,canopy_unload,
& vegtype,glacier_melt,sum_glacmelt,sum_swemelt,snow_d,
& Qe,sfc_sublim_flag,sum_sfcsublim,soft_snow_d,ro_snow,
& sum_sprec,sprec_grnd_ml,sum_prec,prec,sum_runoff,
& ro_snow_grid,xro_snow,swesublim,A1,A2,fc_param,
& Cp_water,ml_ret,icorr_factor_index,corr_factor)
implicit none
include 'snowmodel.inc'
integer JJ,max_layers
integer melt_flag(nz_max)
integer i,j
integer icorr_factor_index
real dy_snow(nz_max)
real swe_lyr(nz_max)
real ro_layer(nz_max)
real T_old(nz_max)
real gamma(nz_max)
real ml_ret(nz_max)
real Tf,dt,ro_water,ro_ice,Qm,ro_snowmax,rain,xLf,Cp_snow,
& runoff,tslsnowfall,ro_nsnow,sprec,Tsfc,tsls_threshold,
& dz_snow_min,snow_depth,swe_depth,undef,change_layer,
& canopy_unload,vegtype,glacier_melt,sum_glacmelt,sum_swemelt,
& soft_snow_d,Qe,sfc_sublim_flag,sum_sfcsublim,snow_d,
& ro_snow,sum_sprec,sprec_grnd_ml,sum_prec,prec,sum_runoff,
& ro_snow_grid,xro_snow,swesublim,A1,A2,Tk,fc_param,Cp_water,