MODULE module_sf_noah_seaice 2
USE module_model_constants
, only : CP, R_D, XLF, XLV, RHOWATER, STBOLT
use module_sf_noahlsm, only : RD, SIGMA, CPH2O, CPICE, LSUBF, EMISSI_S, &
& HSTEP
PUBLIC SFLX_SEAICE
PRIVATE CSNOW
PRIVATE HRTICE
PRIVATE PENMAN
PRIVATE SHFLX
PRIVATE SNOPAC
PRIVATE SNOWPACK
PRIVATE SNOWZ0
PRIVATE SNOW_NEW
INTEGER, PRIVATE :: ILOC
INTEGER, PRIVATE :: JLOC
!$omp threadprivate(iloc, jloc)
REAL, PARAMETER, PRIVATE :: TFREEZ = 273.15
!
CONTAINS
!
SUBROUTINE SFLX_SEAICE (IILOC, JJLOC, SEAICE_ALBEDO_OPT, SEAICE_ALBEDO_DEFAULT, & !C 1,7
& SEAICE_SNOWDEPTH_OPT, SEAICE_SNOWDEPTH_MAX, & !C
& SEAICE_SNOWDEPTH_MIN, & !C
& FFROZP,DT,ZLVL,NSOIL, & !C
& SITHICK, &
& LWDN,SOLNET,SFCPRS,PRCP,SFCTMP,Q2, & !F
& TH2,Q2SAT,DQSDT2, & !I
& SNOALB,TBOT, Z0BRD, Z0, EMISSI, & !S
& T1,STC,SNOWH,SNEQV,ALBEDO, CH, & !H
& ALBEDOSI, SNOWONSI, &
& ETA,SHEAT,ETA_KINEMATIC,FDOWN, & !O
& ESNOW,DEW,ETP,SSOIL,FLX1,FLX2,FLX3, & !O
& SNOMLT,SNCOVR, & !O
& RUNOFF1,Q1,RIBB)
! ----------------------------------------------------------------------
! SUBROUTINE SFLX_SEAICE
! ----------------------------------------------------------------------
! SUB-DRIVER FOR "Noah LSM" FAMILY OF PHYSICS SUBROUTINES FOR A SEA-ICE
! LAND-SURFACE MODEL TO UPDATE ICE TEMPERATURE, SKIN TEMPERATURE,
! SNOWPACK WATER CONTENT, SNOWDEPTH, AND ALL TERMS OF THE SURFACE ENERGY
! BALANCE (EXCLUDING INPUT ATMOSPHERIC FORCINGS OF DOWNWARD RADIATION
! AND PRECIP)
! ----------------------------------------------------------------------
! SFLX_SEAICE ARGUMENT LIST KEY:
! ----------------------------------------------------------------------
! C CONFIGURATION INFORMATION
! F FORCING DATA
! I OTHER (INPUT) FORCING DATA
! S SURFACE CHARACTERISTICS
! H HISTORY (STATE) VARIABLES
! O OUTPUT VARIABLES
! D DIAGNOSTIC OUTPUT
! ----------------------------------------------------------------------
! 1. CONFIGURATION INFORMATION (C):
! ----------------------------------------------------------------------
! DT TIMESTEP (SEC) (DT SHOULD NOT EXCEED 3600 SECS, RECOMMEND
! 1800 SECS OR LESS)
! ZLVL HEIGHT (M) ABOVE GROUND OF ATMOSPHERIC FORCING VARIABLES
! NSOIL NUMBER OF SOIL LAYERS (AT LEAST 2, AND NOT GREATER THAN
! PARAMETER NSOLD SET BELOW)
! ----------------------------------------------------------------------
! 3. FORCING DATA (F):
! ----------------------------------------------------------------------
! LWDN LW DOWNWARD RADIATION (W M-2; POSITIVE, NOT NET LONGWAVE)
! SOLNET NET DOWNWARD SOLAR RADIATION ((W M-2; POSITIVE)
! SFCPRS PRESSURE AT HEIGHT ZLVL ABOVE GROUND (PASCALS)
! PRCP PRECIP RATE (KG M-2 S-1) (NOTE, THIS IS A RATE)
! SFCTMP AIR TEMPERATURE (K) AT HEIGHT ZLVL ABOVE GROUND
! TH2 AIR POTENTIAL TEMPERATURE (K) AT HEIGHT ZLVL ABOVE GROUND
! Q2 MIXING RATIO AT HEIGHT ZLVL ABOVE GROUND (KG KG-1)
! FFROZP FRACTION OF FROZEN PRECIPITATION
! ----------------------------------------------------------------------
! 4. OTHER FORCING (INPUT) DATA (I):
! ----------------------------------------------------------------------
! Q2SAT SAT SPECIFIC HUMIDITY AT HEIGHT ZLVL ABOVE GROUND (KG KG-1)
! DQSDT2 SLOPE OF SAT SPECIFIC HUMIDITY CURVE AT T=SFCTMP
! (KG KG-1 K-1)
! ----------------------------------------------------------------------
! 5. CANOPY/SOIL CHARACTERISTICS (S):
! ----------------------------------------------------------------------
! SNOALB UPPER BOUND ON MAXIMUM ALBEDO OVER DEEP SNOW (E.G. FROM
! ROBINSON AND KUKLA, 1985, J. CLIM. & APPL. METEOR.)
! TBOT BOTTOM SOIL TEMPERATURE (LOCAL YEARLY-MEAN SFC AIR
! TEMPERATURE)
! Z0BRD Background fixed roughness length (M)
! Z0 Time varying roughness length (M) as function of snow depth
!
! EMISSI Surface emissivity (between 0 and 1)
! ----------------------------------------------------------------------
! 6. HISTORY (STATE) VARIABLES (H):
! ----------------------------------------------------------------------
! T1 GROUND/CANOPY/SNOWPACK) EFFECTIVE SKIN TEMPERATURE (K)
! STC(NSOIL) SOIL TEMP (K)
! SNOWH ACTUAL SNOW DEPTH (M)
! SNEQV LIQUID WATER-EQUIVALENT SNOW DEPTH (M)
! NOTE: SNOW DENSITY = SNEQV/SNOWH
! ALBEDO SURFACE ALBEDO
! CH SURFACE EXCHANGE COEFFICIENT FOR HEAT AND MOISTURE
! (M S-1); NOTE: CH IS TECHNICALLY A CONDUCTANCE SINCE
! IT HAS BEEN MULTIPLIED BY WIND SPEED.
! ----------------------------------------------------------------------
! 7. OUTPUT (O):
! ----------------------------------------------------------------------
! OUTPUT VARIABLES NECESSARY FOR A COUPLED NWP MODEL. FOR THIS APPLICATION,
! THE REMAINING OUTPUT/DIAGNOSTIC/PARAMETER BLOCKS BELOW ARE NOT
! NECESSARY. OTHER APPLICATIONS MAY REQUIRE DIFFERENT OUTPUT VARIABLES.
! ETA ACTUAL LATENT HEAT FLUX (W m-2: NEGATIVE, IF UP FROM
! SURFACE)
! ETA_KINEMATIC actual latent heat flux in Kg m-2 s-1
! SHEAT SENSIBLE HEAT FLUX (W M-2: NEGATIVE, IF UPWARD FROM
! SURFACE)
! FDOWN Radiation forcing at the surface (W m-2) = SOLDN*(1-alb)+LWDN
! ----------------------------------------------------------------------
! ESNOW SUBLIMATION FROM (OR DEPOSITION TO IF <0) SNOWPACK (W m-2)
! DEW DEWFALL (OR FROSTFALL FOR T<273.15) (M)
! ----------------------------------------------------------------------
! ETP POTENTIAL EVAPORATION (W m-2)
! SSOIL SOIL HEAT FLUX (W M-2: NEGATIVE IF DOWNWARD FROM SURFACE)
! ----------------------------------------------------------------------
! FLX1 PRECIP-SNOW SFC (W M-2)
! FLX2 FREEZING RAIN LATENT HEAT FLUX (W M-2)
! FLX3 PHASE-CHANGE HEAT FLUX FROM SNOWMELT (W M-2)
! ----------------------------------------------------------------------
! SNOMLT SNOW MELT (M) (WATER EQUIVALENT)
! SNCOVR FRACTIONAL SNOW COVER (UNITLESS FRACTION, 0-1)
! ----------------------------------------------------------------------
! RUNOFF1 SURFACE RUNOFF (M S-1), NOT INFILTRATING THE SURFACE
! ----------------------------------------------------------------------
! 8. DIAGNOSTIC OUTPUT (D):
! ----------------------------------------------------------------------
! Q1 Effective mixing ratio at surface (kg kg-1), used for
! diagnosing the mixing ratio at 2 meter for coupled model
! Documentation SNOABL2 ?????
! What categories of arguments do these variables fall into ????
! Documentation for RIBB ?????
! What category of argument does RIBB fall into ?????
! ----------------------------------------------------------------------
IMPLICIT NONE
! ----------------------------------------------------------------------
integer, intent(in) :: iiloc, jjloc
INTEGER, INTENT(IN) :: SEAICE_ALBEDO_OPT
REAL, INTENT(IN) :: SEAICE_ALBEDO_DEFAULT
INTEGER, INTENT(IN) :: SEAICE_SNOWDEPTH_OPT
REAL, INTENT(IN) :: SEAICE_SNOWDEPTH_MAX
REAL, INTENT(IN) :: SEAICE_SNOWDEPTH_MIN
LOGICAL :: FRZGRA, SNOWNG
INTEGER,INTENT(IN) :: NSOIL
REAL, INTENT(IN) :: DT,DQSDT2,LWDN,PRCP, &
Q2,Q2SAT,SFCPRS,SFCTMP,SNOALB,ALBEDOSI, &
SOLNET,TBOT,TH2,ZLVL, &
FFROZP
REAL, INTENT(OUT) :: ALBEDO
REAL, INTENT(INOUT):: CH, &
SNEQV,SNCOVR,SNOWH,T1,Z0BRD, &
EMISSI
REAL, INTENT(IN) :: SNOWONSI
REAL, INTENT(IN) :: SITHICK
REAL, INTENT(INOUT):: RIBB
REAL, DIMENSION(1:NSOIL), INTENT(INOUT) :: STC
REAL,DIMENSION(1:NSOIL):: ZSOIL
REAL,INTENT(OUT) :: ETA_KINEMATIC,DEW,ESNOW,ETA, &
ETP,FLX1,FLX2,FLX3,SHEAT,RUNOFF1, &
SSOIL, &
SNOMLT, &
FDOWN,Q1,Z0
REAL :: DF1,DF1A, &
DSOIL,DTOT,FRCSNO,FRCSOI, &
RCH,RR, &
SNDENS,SNCOND,SN_NEW, &
T24,T2V,TH2V,TSNOW
REAL :: RHO
INTEGER :: KZ, K
REAL :: ALB_SNOW
REAL :: ALB_ICE
REAL :: Z0N
REAL :: SNCOVRR
! ----------------------------------------------------------------------
! DECLARATIONS - PARAMETERS
! ----------------------------------------------------------------------
REAL, PARAMETER :: LVH2O = 2.501E+6
REAL, PARAMETER :: LSUBS = 2.83E+6
REAL, PARAMETER :: R = 287.04
iloc = iiloc
jloc = jjloc
! ----------------------------------------------------------------------
! INITIALIZATION
! ----------------------------------------------------------------------
RUNOFF1 = 0.0
SNOMLT = 0.0
! ----------------------------------------------------------------------
! SEA-ICE LAYERS ARE EQUAL THICKNESS AND SUM TO <SITHICK> METERS
! ----------------------------------------------------------------------
DO KZ = 1,NSOIL
ZSOIL (KZ) = -SITHICK * FLOAT (KZ) / FLOAT (NSOIL)
END DO
! ----------------------------------------------------------------------
Z0BRD = 0.001
! ALB = 0.82 ! Arctic pre-melt spring and post-melt autumn
! ALB = 0.80 ! Antarctica
! ALB = 0.50 ! Arctic mid-summer (ice and melt ponds)
! ALB = 0.65 ! Arctic bare ice with no snow and no melt ponds
! ----------------------------------------------------------------------
! INITIALIZE PRECIPITATION LOGICALS.
! ----------------------------------------------------------------------
SNOWNG = .FALSE.
FRZGRA = .FALSE.
! ----------------------------------------------------------------------
! OVER SEA-ICE, IF S.W.E. (SNEQV) BELOW THRESHOLD LOWER
! BOUND (0.01 M FOR SEA-ICE, 0.10 M FOR GLACIAL-ICE), THEN SET AT LOWER
! BOUND
! ----------------------------------------------------------------------
! FOR SEA-ICE CASE, ASSIGN DEFAULT WATER-EQUIV SNOW ON TOP
! ----------------------------------------------------------------------
SELECT CASE ( SEAICE_ALBEDO_OPT )
CASE DEFAULT
IF ( SNEQV < 0.01 ) THEN
SNEQV = 0.01
SNOWH = 0.05
ENDIF
CASE ( 1 ) ! Arctic sea-ice albedo from Mills (2011)
IF ( SNEQV < 0.0001 ) THEN
SNEQV = 0.0001
SNOWH = 0.0005
ENDIF
END SELECT
IF ( SEAICE_SNOWDEPTH_OPT == 0 ) THEN
!
! Enforce bounds on snow depth, maintaining original snow density.
!
SNDENS = SNEQV / SNOWH
SNOWH = MAX ( SEAICE_SNOWDEPTH_MIN , MIN ( SNOWH , SEAICE_SNOWDEPTH_MAX ) )
SNEQV = SNOWH * SNDENS
ELSEIF ( SEAICE_SNOWDEPTH_OPT == 1 ) THEN
!
! Regardless of the assignments above, we want to enforce
! a specified snow depth and density on sea ice.
!
SNDENS = 0.3
SNOWH = SNOWONSI
SNEQV = SNOWH * SNDENS
ENDIF
! ----------------------------------------------------------------------
! IF INPUT SNOWPACK IS NONZERO, THEN COMPUTE SNOW DENSITY "SNDENS" AND
! SNOW THERMAL CONDUCTIVITY "SNCOND"
! ----------------------------------------------------------------------
SNDENS = SNEQV / SNOWH
IF(SNDENS > 1.0) THEN
CALL wrf_error_fatal ( 'Physical snow depth is less than snow water equiv.' )
ENDIF
CALL CSNOW (SNCOND,SNDENS)
! ----------------------------------------------------------------------
! DETERMINE IF IT'S PRECIPITATING AND WHAT KIND OF PRECIP IT IS.
! IF IT'S PRCPING AND THE AIR TEMP IS COLDER THAN 0 C, IT'S SNOWING!
! IF IT'S PRCPING AND THE AIR TEMP IS WARMER THAN 0 C, BUT THE GRND
! TEMP IS COLDER THAN 0 C, FREEZING RAIN IS PRESUMED TO BE FALLING.
! ----------------------------------------------------------------------
IF (PRCP > 0.0) THEN
! snow defined when fraction of frozen precip (FFROZP) > 0.5,
! passed in from model microphysics.
IF (FFROZP .GT. 0.5) THEN
SNOWNG = .TRUE.
ELSE
IF (T1 <= TFREEZ) FRZGRA = .TRUE.
END IF
END IF
! ----------------------------------------------------------------------
! IF EITHER PRCP FLAG IS SET, DETERMINE NEW SNOWFALL (CONVERTING PRCP
! RATE FROM KG M-2 S-1 TO A LIQUID EQUIV SNOW DEPTH IN METERS) AND ADD
! IT TO THE EXISTING SNOWPACK.
! ----------------------------------------------------------------------
IF ( SNOWNG .OR. FRZGRA ) THEN
SN_NEW = PRCP * DT * 0.001
SNEQV = SNEQV + SN_NEW
! ----------------------------------------------------------------------
! UPDATE SNOW DENSITY BASED ON NEW SNOWFALL, USING OLD AND NEW SNOW.
! UPDATE SNOW THERMAL CONDUCTIVITY
! ----------------------------------------------------------------------
CALL SNOW_NEW ( SFCTMP , SN_NEW , SNOWH , SNDENS )
!
! kmh 09/04/2006 set Snow Density at 0.2 g/cm**3
! for "cold permanent ice" or new "dry" snow
!
IF ( SNCOVR .GT. 0.99 ) THEN
!
! if soil temperature less than 268.15 K, treat as typical
! Antarctic/Greenland snow firn
!
IF ( STC(1) .LT. (TFREEZ - 5.) ) SNDENS = 0.2
IF ( SNOWNG .AND. (T1.LT.273.) .AND. (SFCTMP.LT.273.) ) SNDENS=0.2
ENDIF
CALL CSNOW (SNCOND,SNDENS)
END IF
! ----------------------------------------------------------------------
! ALBEDO OF SEA ICE
! ----------------------------------------------------------------------
SELECT CASE ( SEAICE_ALBEDO_OPT )
CASE DEFAULT
SNCOVR = 1.0
EMISSI = 0.98
ALBEDO = SEAICE_ALBEDO_DEFAULT
! ALBEDO = 0.82 ! Arctic pre-melt spring and post-melt autumn
! ALBEDO = 0.80 ! Antarctica
! ALBEDO = 0.50 ! Arctic mid-summer (ice and melt ponds)
! ALBEDO = 0.65 ! Arctic bare ice with no snow and no melt ponds
CASE ( 1 ) ! Arctic sea-ice albedo from Mills (2011)
!
! Make albedo of snow on sea-ice a function of skin temperature:
!
IF (T1 < 268.15) THEN
alb_snow = 0.8
ELSEIF ( ( T1 >= 268.15 ) .AND. ( T1 < 273.15 ) ) then
alb_snow = 0.65 - ( 0.03 * (T1 - 273.15) )
ELSE
alb_snow = 0.65
ENDIF
!
! Make albedo of snow-free sea-ice a function of air temperature
!
IF ( SFCTMP <= 273.15 ) THEN
alb_ice = 0.65
ELSEIF ( ( SFCTMP > 273.15 ) .and. ( SFCTMP < 278.15 ) ) THEN
alb_ice = 0.65 - ( 0.04 * (SFCTMP - 273.15) )
ELSE
alb_ice = 0.45
ENDIF
!
! Define a snow-cover fraction for use only with Mills sea-ice albedo
!
Z0N = 0.10 ! Approximate roughness length of snow-covered surface
SNCOVRR = SNOWH / ( SNOWH + Z0N )
!
! Final albedo over sea-ice point is a combination of the snow
! albedo and the snow-free ice albedo, weighted by the snow cover.
!
ALBEDO = (SNCOVRR * alb_snow ) + ( ( 1.0 - SNCOVRR) * alb_ice )
CASE ( 2 ) ! Seaice albedo from 2d field
SNCOVR = 1.0
EMISSI = 0.98
ALBEDO = ALBEDOSI
END SELECT
! ----------------------------------------------------------------------
! THERMAL CONDUCTIVITY FOR SEA-ICE CASE
! ----------------------------------------------------------------------
DF1 = 2.2
DSOIL = - (0.5 * ZSOIL (1))
DTOT = SNOWH + DSOIL
FRCSNO = SNOWH / DTOT
! 1. HARMONIC MEAN (SERIES FLOW)
! DF1 = (SNCOND*DF1)/(FRCSOI*SNCOND+FRCSNO*DF1)
FRCSOI = DSOIL / DTOT
! 2. ARITHMETIC MEAN (PARALLEL FLOW)
! DF1 = FRCSNO*SNCOND + FRCSOI*DF1
! 3. GEOMETRIC MEAN (INTERMEDIATE BETWEEN HARMONIC AND ARITHMETIC MEAN)
! DF1 = (SNCOND**FRCSNO)*(DF1**FRCSOI)
! weigh DF by snow fraction
DF1A = FRCSNO * SNCOND + FRCSOI * DF1
! ----------------------------------------------------------------------
! CALCULATE SUBSURFACE HEAT FLUX, SSOIL, FROM FINAL THERMAL DIFFUSIVITY
! OF SURFACE MEDIUMS, DF1 ABOVE, AND SKIN TEMPERATURE AND TOP
! MID-LAYER SOIL TEMPERATURE
! ----------------------------------------------------------------------
DF1 = DF1A * SNCOVR + DF1 * ( 1.0 - SNCOVR )
SSOIL = DF1 * ( T1 - STC(1) ) / DTOT
! ----------------------------------------------------------------------
! DETERMINE SURFACE ROUGHNESS OVER SNOWPACK USING SNOW CONDITION FROM
! THE PREVIOUS TIMESTEP.
! ----------------------------------------------------------------------
CALL SNOWZ0 (SNCOVR,Z0,Z0BRD,SNOWH)
! ----------------------------------------------------------------------
! CALCULATE TOTAL DOWNWARD RADIATION (SOLAR PLUS LONGWAVE) NEEDED IN
! PENMAN EP SUBROUTINE THAT FOLLOWS
! ----------------------------------------------------------------------
FDOWN = SOLNET + LWDN
! ----------------------------------------------------------------------
! CALC VIRTUAL TEMPS AND VIRTUAL POTENTIAL TEMPS NEEDED BY SUBROUTINES
! PENMAN.
! ----------------------------------------------------------------------
T2V = SFCTMP * (1.0+ 0.61 * Q2 )
T24 = SFCTMP * SFCTMP * SFCTMP * SFCTMP
RHO = SFCPRS / ( RD * T2V )
! RCH = RHO * CP * CH
RCH = RHO * 1004.6 * CH ! CP is defined different in subroutine PENMAN.
! Pulling this computation out of PENMAN changed
! the results. So I'm hard-coding the PENMAN
! value here, but perhaps this should go back
! into PENMAN for now.
! ----------------------------------------------------------------------
! CALL PENMAN SUBROUTINE TO CALCULATE POTENTIAL EVAPORATION (ETP), AND
! OTHER PARTIAL PRODUCTS AND SUMS FOR LATER CALCULATIONS.
! ----------------------------------------------------------------------
CALL PENMAN (SFCTMP,SFCPRS,CH,TH2,PRCP,FDOWN,T24,SSOIL, &
Q2,Q2SAT,ETP,RCH,RR,SNOWNG,FRZGRA, &
DQSDT2,FLX2,EMISSI,T1)
ESNOW = 0.0
CALL SNOPAC (ETP,ETA,PRCP,SNOWNG, &
NSOIL,DT,DF1, &
Q2,T1,SFCTMP,T24,TH2,FDOWN,SSOIL,STC, &
SFCPRS,RCH,RR,SNCOVR,SNEQV,SNDENS, &
SNOWH,ZSOIL,TBOT, &
SNOMLT,DEW,FLX1,FLX2,FLX3,ESNOW,EMISSI,RIBB, &
SEAICE_ALBEDO_OPT)
ETA_KINEMATIC = ESNOW
IF ( SEAICE_SNOWDEPTH_OPT == 0 ) THEN
!
! Set bounds on snow depth, maintaining snow density.
!
SNDENS = SNEQV / SNOWH
SNOWH = MAX ( SEAICE_SNOWDEPTH_MIN , MIN ( SNOWH , SEAICE_SNOWDEPTH_MAX ) )
SNEQV = SNOWH * SNDENS
ELSEIF ( SEAICE_SNOWDEPTH_OPT == 1 ) THEN
!
! Regardless of the results of snopac, we want to enforce
! a specified snow depth and density on sea ice.
!
SNDENS = 0.3
SNOWH = SNOWONSI
SNEQV = SNOWH * SNDENS
ENDIF
! Calculate effective mixing ratio at ground level (skin)
Q1=Q2+ETA_KINEMATIC*CP/RCH
!
! ----------------------------------------------------------------------
! DETERMINE SENSIBLE HEAT (H) IN ENERGY UNITS (W M-2)
! ----------------------------------------------------------------------
SHEAT = - (CH * CP * SFCPRS)/ (R * T2V) * ( TH2- T1 )
! ----------------------------------------------------------------------
! CONVERT EVAP TERMS FROM KINEMATIC (KG M-2 S-1) TO ENERGY UNITS (W M-2)
! ----------------------------------------------------------------------
ESNOW = ESNOW * LSUBS
ETP = ETP*((1.-SNCOVR)*LVH2O + SNCOVR*LSUBS)
IF (ETP .GT. 0.) THEN
ETA = ESNOW
ELSE
ETA = ETP
ENDIF
! ----------------------------------------------------------------------
! CONVERT THE SIGN OF SOIL HEAT FLUX SO THAT:
! SSOIL>0: WARM THE SURFACE (NIGHT TIME)
! SSOIL<0: COOL THE SURFACE (DAY TIME)
! ----------------------------------------------------------------------
SSOIL = -1.0* SSOIL
! ----------------------------------------------------------------------
! FOR THE CASE OF SEA-ICE, ADD ANY
! SNOWMELT DIRECTLY TO SURFACE RUNOFF (RUNOFF1) SINCE THERE IS NO
! SOIL MEDIUM, AND THUS NO CALL TO SUBROUTINE SMFLX (FOR SOIL MOISTURE
! TENDENCY).
! ----------------------------------------------------------------------
RUNOFF1 = SNOMLT/DT
! ----------------------------------------------------------------------
END SUBROUTINE SFLX_SEAICE
! ----------------------------------------------------------------------
SUBROUTINE CSNOW (SNCOND,DSNOW) 7
! ----------------------------------------------------------------------
! SUBROUTINE CSNOW
! FUNCTION CSNOW
! ----------------------------------------------------------------------
! CALCULATE SNOW TERMAL CONDUCTIVITY
! ----------------------------------------------------------------------
IMPLICIT NONE
REAL, INTENT(IN) :: DSNOW
REAL, INTENT(OUT):: SNCOND
REAL :: C
REAL, PARAMETER :: UNIT = 0.11631
! ----------------------------------------------------------------------
! SNCOND IN UNITS OF CAL/(CM*HR*C), RETURNED IN W/(M*C)
! CSNOW IN UNITS OF CAL/(CM*HR*C), RETURNED IN W/(M*C)
! BASIC VERSION IS DYACHKOVA EQUATION (1960), FOR RANGE 0.1-0.4
! ----------------------------------------------------------------------
C = 0.328*10** (2.25* DSNOW)
! CSNOW=UNIT*C
! ----------------------------------------------------------------------
! DE VAUX EQUATION (1933), IN RANGE 0.1-0.6
! ----------------------------------------------------------------------
! SNCOND=0.0293*(1.+100.*DSNOW**2)
! CSNOW=0.0293*(1.+100.*DSNOW**2)
! ----------------------------------------------------------------------
! E. ANDERSEN FROM FLERCHINGER
! ----------------------------------------------------------------------
! SNCOND=0.021+2.51*DSNOW**2
! CSNOW=0.021+2.51*DSNOW**2
! SNCOND = UNIT * C
! double snow thermal conductivity
SNCOND = 2.0 * UNIT * C
! ----------------------------------------------------------------------
END SUBROUTINE CSNOW
! ----------------------------------------------------------------------
SUBROUTINE HRTICE (RHSTS,STC,TBOT,NSOIL,ZSOIL,YY,ZZ1,DF1,AI,BI,CI) 2
! ----------------------------------------------------------------------
! CALCULATE THE RIGHT HAND SIDE OF THE TIME TENDENCY TERM OF THE SOIL
! THERMAL DIFFUSION EQUATION IN THE CASE OF SEA-ICE (ICE=1) OR GLACIAL
! ICE (ICE=-1). COMPUTE (PREPARE) THE MATRIX COEFFICIENTS FOR THE
! TRI-DIAGONAL MATRIX OF THE IMPLICIT TIME SCHEME.
!
! (NOTE: THIS SUBROUTINE ONLY CALLED FOR SEA-ICE OR GLACIAL ICE, BUT
! NOT FOR NON-GLACIAL LAND (ICE = 0).
! ----------------------------------------------------------------------
IMPLICIT NONE
INTEGER, INTENT(IN) :: NSOIL
INTEGER :: K
REAL, INTENT(IN) :: DF1,YY,ZZ1
REAL, DIMENSION(1:NSOIL), INTENT(OUT):: AI, BI,CI
REAL, DIMENSION(1:NSOIL), INTENT(IN) :: STC, ZSOIL
REAL, DIMENSION(1:NSOIL), INTENT(OUT):: RHSTS
REAL, INTENT(IN) :: TBOT
REAL :: DDZ,DDZ2,DENOM,DTSDZ,DTSDZ2,SSOIL, &
ZBOT
REAL :: HCPCT
REAL :: DF1K
REAL :: DF1N
REAL :: ZMD
! ----------------------------------------------------------------------
! SET A NOMINAL UNIVERSAL VALUE OF THE SEA-ICE SPECIFIC HEAT CAPACITY,
! HCPCT = 1880.0*917.0.
! ----------------------------------------------------------------------
! Sea-ice values
HCPCT = 1.72396E+6
! ----------------------------------------------------------------------
! THE INPUT ARGUMENT DF1 IS A UNIVERSALLY CONSTANT VALUE OF SEA-ICE
! THERMAL DIFFUSIVITY, SET IN ROUTINE SNOPAC AS DF1 = 2.2.
! ----------------------------------------------------------------------
! SET ICE PACK DEPTH. USE TBOT AS ICE PACK LOWER BOUNDARY TEMPERATURE
! (THAT OF UNFROZEN SEA WATER AT BOTTOM OF SEA ICE PACK). ASSUME ICE
! PACK IS OF N=NSOIL LAYERS SPANNING A UNIFORM CONSTANT ICE PACK
! THICKNESS AS DEFINED BY ZSOIL(NSOIL) IN ROUTINE SFLX.
! ----------------------------------------------------------------------
! ----------------------------------------------------------------------
! CALC THE MATRIX COEFFICIENTS AI, BI, AND CI FOR THE TOP LAYER
! ----------------------------------------------------------------------
ZBOT = ZSOIL (NSOIL)
DDZ = 1.0 / ( -0.5 * ZSOIL (2) )
AI (1) = 0.0
CI (1) = (DF1 * DDZ) / (ZSOIL (1) * HCPCT)
! ----------------------------------------------------------------------
! CALC THE VERTICAL SOIL TEMP GRADIENT BTWN THE TOP AND 2ND SOIL LAYERS.
! RECALC/ADJUST THE SOIL HEAT FLUX. USE THE GRADIENT AND FLUX TO CALC
! RHSTS FOR THE TOP SOIL LAYER.
! ----------------------------------------------------------------------
BI (1) = - CI (1) + DF1/ (0.5 * ZSOIL (1) * ZSOIL (1) * HCPCT * &
ZZ1)
DTSDZ = ( STC (1) - STC (2) ) / ( -0.5 * ZSOIL (2) )
SSOIL = DF1 * ( STC (1) - YY ) / ( 0.5 * ZSOIL (1) * ZZ1 )
! ----------------------------------------------------------------------
! INITIALIZE DDZ2
! ----------------------------------------------------------------------
RHSTS (1) = ( DF1 * DTSDZ - SSOIL ) / ( ZSOIL (1) * HCPCT )
! ----------------------------------------------------------------------
! LOOP THRU THE REMAINING SOIL LAYERS, REPEATING THE ABOVE PROCESS
! ----------------------------------------------------------------------
DDZ2 = 0.0
DF1K = DF1
DF1N = DF1
DO K = 2,NSOIL
! ----------------------------------------------------------------------
! CALC THE VERTICAL SOIL TEMP GRADIENT THRU THIS LAYER.
! ----------------------------------------------------------------------
IF (K /= NSOIL) THEN
DENOM = 0.5 * ( ZSOIL (K -1) - ZSOIL (K +1) )
! ----------------------------------------------------------------------
! CALC THE MATRIX COEF, CI, AFTER CALC'NG ITS PARTIAL PRODUCT.
! ----------------------------------------------------------------------
DTSDZ2 = ( STC (K) - STC (K +1) ) / DENOM
DDZ2 = 2. / (ZSOIL (K -1) - ZSOIL (K +1))
CI (K) = - DF1N * DDZ2 / ( (ZSOIL (K -1) - ZSOIL (K))*HCPCT)
! ----------------------------------------------------------------------
! CALC THE VERTICAL SOIL TEMP GRADIENT THRU THE LOWEST LAYER.
! ----------------------------------------------------------------------
ELSE
! ----------------------------------------------------------------------
! SET MATRIX COEF, CI TO ZERO.
! ----------------------------------------------------------------------
DTSDZ2 = (STC (K) - TBOT)/ (.5 * (ZSOIL (K -1) + ZSOIL (K)) &
- ZBOT)
CI (K) = 0.
END IF
! ----------------------------------------------------------------------
! CALC RHSTS FOR THIS LAYER AFTER CALC'NG A PARTIAL PRODUCT.
! ----------------------------------------------------------------------
DENOM = ( ZSOIL (K) - ZSOIL (K -1) ) * HCPCT
! ----------------------------------------------------------------------
! CALC MATRIX COEFS, AI, AND BI FOR THIS LAYER.
! ----------------------------------------------------------------------
RHSTS (K) = ( DF1N * DTSDZ2- DF1K * DTSDZ ) / DENOM
AI (K) = - DF1K * DDZ / ( (ZSOIL (K -1) - ZSOIL (K)) * HCPCT)
BI (K) = - (AI (K) + CI (K))
! ----------------------------------------------------------------------
! RESET VALUES OF DTSDZ AND DDZ FOR LOOP TO NEXT SOIL LYR.
! ----------------------------------------------------------------------
DF1K = DF1N
DTSDZ = DTSDZ2
DDZ = DDZ2
END DO
! ----------------------------------------------------------------------
END SUBROUTINE HRTICE
! ----------------------------------------------------------------------
SUBROUTINE PENMAN (SFCTMP,SFCPRS,CH,TH2,PRCP,FDOWN,T24,SSOIL, & 3
& Q2,Q2SAT,ETP,RCH,RR,SNOWNG,FRZGRA, &
& DQSDT2,FLX2,EMISSI,T1)
! ----------------------------------------------------------------------
! CALCULATE POTENTIAL EVAPORATION FOR THE CURRENT POINT. VARIOUS
! PARTIAL SUMS/PRODUCTS ARE ALSO CALCULATED AND PASSED BACK TO THE
! CALLING ROUTINE FOR LATER USE.
! ----------------------------------------------------------------------
IMPLICIT NONE
LOGICAL, INTENT(IN) :: SNOWNG, FRZGRA
REAL, INTENT(IN) :: CH, DQSDT2, FDOWN, PRCP, &
& Q2, Q2SAT, SSOIL, SFCPRS, SFCTMP, &
& TH2,EMISSI
REAL, INTENT(IN) :: T1, T24, RCH
REAL, INTENT(OUT) :: ETP,FLX2,RR
REAL :: ELCP1, LVS, EPSCA, A, DELTA, FNET, RAD
REAL, PARAMETER :: ELCP = 2.4888E+3, LSUBC = 2.501000E+6,CP = 1004.6
REAL, PARAMETER :: LSUBS = 2.83E+6
! ----------------------------------------------------------------------
! PREPARE PARTIAL QUANTITIES FOR PENMAN EQUATION.
! ----------------------------------------------------------------------
IF ( T1 > 273.15 ) THEN
ELCP1=ELCP
LVS=LSUBC
ELSE
ELCP1 = ELCP*LSUBS/LSUBC
LVS = LSUBS
ENDIF
FLX2 = 0.0
DELTA = ELCP1 * DQSDT2
RR = EMISSI * T24 * 6.48E-8 / (SFCPRS * CH) + 1.0
! ----------------------------------------------------------------------
! ADJUST THE PARTIAL SUMS / PRODUCTS WITH THE LATENT HEAT
! EFFECTS CAUSED BY FALLING PRECIPITATION.
! ----------------------------------------------------------------------
IF ( PRCP > 0.0 ) THEN
IF (.NOT. SNOWNG) THEN
RR = RR + CPH2O * PRCP / RCH
ELSE
RR = RR + CPICE * PRCP / RCH
ENDIF
ENDIF
! ----------------------------------------------------------------------
! INCLUDE THE LATENT HEAT EFFECTS OF FREEZING RAIN CONVERTING TO ICE ON
! IMPACT IN THE CALCULATION OF FLX2 AND FNET.
! ----------------------------------------------------------------------
FNET = FDOWN - EMISSI * SIGMA * T24 - SSOIL
IF (FRZGRA) THEN
FLX2 = - LSUBF * PRCP
FNET = FNET - FLX2
END IF
! ----------------------------------------------------------------------
! FINISH PENMAN EQUATION CALCULATIONS.
! ----------------------------------------------------------------------
RAD = FNET / RCH + TH2 - SFCTMP
A = ELCP1 * (Q2SAT - Q2)
EPSCA = (A * RR + RAD * DELTA) / (DELTA + RR)
ETP = EPSCA * RCH / LVS
! ----------------------------------------------------------------------
END SUBROUTINE PENMAN
! ----------------------------------------------------------------------
SUBROUTINE SHFLX (STC,NSOIL,DT,YY,ZZ1,ZSOIL,TBOT,DF1) 4,6
! ----------------------------------------------------------------------
! UPDATE THE TEMPERATURE STATE OF THE SOIL COLUMN BASED ON THE THERMAL
! DIFFUSION EQUATION.
! ----------------------------------------------------------------------
IMPLICIT NONE
INTEGER, INTENT(IN) :: NSOIL
REAL, INTENT(IN) :: DF1,DT,TBOT,YY, ZZ1
REAL, DIMENSION(1:NSOIL), INTENT(IN) :: ZSOIL
REAL, DIMENSION(1:NSOIL), INTENT(INOUT) :: STC
REAL, DIMENSION(1:NSOIL) :: AI, BI, CI, STCF,RHSTS
INTEGER :: I
REAL, PARAMETER :: T0 = 273.15
! ----------------------------------------------------------------------
! HRTICE ROUTINE CALCS THE RIGHT HAND SIDE OF THE SOIL TEMP DIF EQN
! ----------------------------------------------------------------------
CALL HRTICE (RHSTS,STC,TBOT,NSOIL,ZSOIL,YY,ZZ1,DF1,AI,BI,CI)
CALL HSTEP (STCF,STC,RHSTS,DT,NSOIL,AI,BI,CI)
DO I = 1,NSOIL
STC (I) = STCF (I)
END DO
! ----------------------------------------------------------------------
END SUBROUTINE SHFLX
! ----------------------------------------------------------------------
SUBROUTINE SNOPAC (ETP,ETA,PRCP,SNOWNG, & 3,9
NSOIL,DT,DF1, &
Q2,T1,SFCTMP,T24,TH2,FDOWN,SSOIL,STC, &
SFCPRS,RCH,RR,SNCOVR,ESD,SNDENS, &
SNOWH,ZSOIL,TBOT, &
SNOMLT,DEW,FLX1,FLX2,FLX3,ESNOW,EMISSI, &
RIBB, SEAICE_ALBEDO_OPT)
! ----------------------------------------------------------------------
! SUBROUTINE SNOPAC
! ----------------------------------------------------------------------
! CALCULATE SOIL MOISTURE AND HEAT FLUX VALUES & UPDATE SOIL MOISTURE
! CONTENT AND SOIL HEAT CONTENT VALUES FOR THE CASE WHEN A SNOW PACK IS
! PRESENT.
! ----------------------------------------------------------------------
IMPLICIT NONE
INTEGER, INTENT(IN) :: NSOIL
INTEGER :: K
LOGICAL, INTENT(IN) :: SNOWNG
REAL, INTENT(IN) :: DF1, &
& DT,FDOWN, &
& PRCP,Q2, &
& RCH,RR,SFCPRS, SFCTMP, &
& T24, &
& TBOT,TH2,EMISSI
REAL, INTENT(INOUT) :: ESD,FLX2,SNOWH,SNCOVR, &
& SNDENS, T1, RIBB, ETP
REAL, INTENT(OUT) :: DEW,ESNOW, &
& FLX1,FLX3, SSOIL,SNOMLT
REAL, DIMENSION(1:NSOIL),INTENT(IN) :: ZSOIL
REAL, DIMENSION(1:NSOIL), INTENT(INOUT) :: STC
REAL :: DENOM,DSOIL,DTOT,ETA, &
& ESNOW1, ESNOW2, ETA1,ETP1,ETP2, &
& ETANRG, EX, SEH, &
& SNCOND,T12, T12A, &
& T12B, T14, YY, ZZ1
INTEGER, INTENT(IN) :: SEAICE_ALBEDO_OPT
REAL, PARAMETER :: ESDMIN = 1.E-6, LSUBC = 2.501000E+6, &
LSUBS = 2.83E+6, SNOEXP = 2.0
! ----------------------------------------------------------------------
! SNOWCOVER FRACTION = 1.0, AND SUBLIMATION IS AT THE POTENTIAL RATE.
! ----------------------------------------------------------------------
! INITIALIZE EVAP TERMS.
! ----------------------------------------------------------------------
! conversions:
! ESNOW [KG M-2 S-1]
! ESNOW1 [M S-1]
! ESNOW2 [M]
! ETP [KG M-2 S-1]
! ETP1 [M S-1]
! ETP2 [M]
! ----------------------------------------------------------------------
DEW = 0.
ESNOW = 0.
ESNOW1 = 0.
ESNOW2 = 0.
! ----------------------------------------------------------------------
! CONVERT POTENTIAL EVAP (ETP) FROM KG M-2 S-1 TO ETP1 IN M S-1
! ----------------------------------------------------------------------
! ----------------------------------------------------------------------
! IF ETP<0 (DOWNWARD) THEN DEWFALL (=FROSTFALL IN THIS CASE).
! ----------------------------------------------------------------------
IF (ETP <= 0.0) THEN
IF ( ( RIBB >= 0.1 ) .AND. ( FDOWN > 150.0 ) ) THEN
ETP=(MIN(ETP*(1.0-RIBB),0.)*SNCOVR/0.980 + ETP*(0.980-SNCOVR))/0.980
ENDIF
ETP1 = ETP * 0.001
DEW = -ETP1
ESNOW2 = ETP1*DT
ETANRG = ETP*((1.-SNCOVR)*LSUBC + SNCOVR*LSUBS)
ELSE
ETP1 = ETP * 0.001
ESNOW = ETP
ESNOW1 = ESNOW*0.001
ESNOW2 = ESNOW1*DT
ETANRG = ESNOW*LSUBS
ESNOW = ETP*SNCOVR
ESNOW1 = ESNOW*0.001
ESNOW2 = ESNOW1*DT
ETANRG = ESNOW*LSUBS
END IF
! ----------------------------------------------------------------------
! IF PRECIP IS FALLING, CALCULATE HEAT FLUX FROM SNOW SFC TO NEWLY
! ACCUMULATING PRECIP. NOTE THAT THIS REFLECTS THE FLUX APPROPRIATE FOR
! THE NOT-YET-UPDATED SKIN TEMPERATURE (T1). ASSUMES TEMPERATURE OF THE
! SNOWFALL STRIKING THE GROUND IS =SFCTMP (LOWEST MODEL LEVEL AIR TEMP).
! ----------------------------------------------------------------------
FLX1 = 0.0
IF (SNOWNG) THEN
FLX1 = CPICE * PRCP * (T1- SFCTMP)
ELSE
IF (PRCP > 0.0) FLX1 = CPH2O * PRCP * (T1- SFCTMP)
! ----------------------------------------------------------------------
! CALCULATE AN 'EFFECTIVE SNOW-GRND SFC TEMP' (T12) BASED ON HEAT FLUXES
! BETWEEN THE SNOW PACK AND THE SOIL AND ON NET RADIATION.
! INCLUDE FLX1 (PRECIP-SNOW SFC) AND FLX2 (FREEZING RAIN LATENT HEAT)
! FLUXES. FLX1 FROM ABOVE, FLX2 BROUGHT IN VIA COMMOM BLOCK RITE.
! FLX2 REFLECTS FREEZING RAIN LATENT HEAT FLUX USING T1 CALCULATED IN
! PENMAN.
! ----------------------------------------------------------------------
END IF
DSOIL = - (0.5 * ZSOIL (1))
DTOT = SNOWH + DSOIL
DENOM = 1.0+ DF1 / (DTOT * RR * RCH)
! surface emissivity weighted by snow cover fraction
! T12A = ( (FDOWN - FLX1 - FLX2 - &
! & ((SNCOVR*EMISSI_S)+EMISSI*(1.0-SNCOVR))*SIGMA *T24)/RCH &
! & + TH2 - SFCTMP - ETANRG/RCH ) / RR
T12A = ( (FDOWN - FLX1 - FLX2 - EMISSI * SIGMA * T24)/ RCH &
+ TH2 - SFCTMP - ETANRG / RCH ) / RR
T12B = DF1 * STC (1) / (DTOT * RR * RCH)
! ----------------------------------------------------------------------
! IF THE 'EFFECTIVE SNOW-GRND SFC TEMP' IS AT OR BELOW FREEZING, NO SNOW
! MELT WILL OCCUR. SET THE SKIN TEMP TO THIS EFFECTIVE TEMP. REDUCE
! (BY SUBLIMINATION ) OR INCREASE (BY FROST) THE DEPTH OF THE SNOWPACK,
! DEPENDING ON SIGN OF ETP.
! UPDATE SOIL HEAT FLUX (SSOIL) USING NEW SKIN TEMPERATURE (T1)
! SINCE NO SNOWMELT, SET ACCUMULATED SNOWMELT TO ZERO, SET 'EFFECTIVE'
! PRECIP FROM SNOWMELT TO ZERO, SET PHASE-CHANGE HEAT FLUX FROM SNOWMELT
! TO ZERO.
! ----------------------------------------------------------------------
! SUB-FREEZING BLOCK
! ----------------------------------------------------------------------
T12 = (SFCTMP + T12A + T12B) / DENOM
IF (T12 <= TFREEZ) THEN
T1 = T12
SSOIL = DF1 * (T1- STC (1)) / DTOT
! ESD = MAX (0.0, ESD- ETP2)
ESD = MAX(0.0, ESD-ESNOW2)
FLX3 = 0.0
EX = 0.0
SNOMLT = 0.0
! ----------------------------------------------------------------------
! IF THE 'EFFECTIVE SNOW-GRND SFC TEMP' IS ABOVE FREEZING, SNOW MELT
! WILL OCCUR. CALL THE SNOW MELT RATE,EX AND AMT, SNOMLT. REVISE THE
! EFFECTIVE SNOW DEPTH. REVISE THE SKIN TEMP BECAUSE IT WOULD HAVE CHGD
! DUE TO THE LATENT HEAT RELEASED BY THE MELTING. CALC THE LATENT HEAT
! RELEASED, FLX3. ADJUSTMENT TO T1 TO ACCOUNT FOR SNOW PATCHES.
! CALCULATE QSAT VALID AT FREEZING POINT. NOTE THAT ESAT (SATURATION
! VAPOR PRESSURE) VALUE OF 6.11E+2 USED HERE IS THAT VALID AT FRZZING
! POINT. NOTE THAT ETP FROM CALL PENMAN IN SFLX IS IGNORED HERE IN
! FAVOR OF BULK ETP OVER 'OPEN WATER' AT FREEZING TEMP.
! UPDATE SOIL HEAT FLUX (S) USING NEW SKIN TEMPERATURE (T1)
! ----------------------------------------------------------------------
! ABOVE FREEZING BLOCK
! ----------------------------------------------------------------------
ELSE
T1 = TFREEZ * SNCOVR ** SNOEXP + T12 * (1.0- SNCOVR ** SNOEXP)
SSOIL = DF1 * (T1- STC (1)) / DTOT
! ----------------------------------------------------------------------
! IF POTENTIAL EVAP (SUBLIMATION) GREATER THAN DEPTH OF SNOWPACK.
! SNOWPACK HAS SUBLIMATED AWAY, SET DEPTH TO ZERO.
! ----------------------------------------------------------------------
IF (ESD-ESNOW2 <= ESDMIN) THEN
ESD = 0.0
EX = 0.0
SNOMLT = 0.0
FLX3 = 0.0
! ----------------------------------------------------------------------
! SUBLIMATION LESS THAN DEPTH OF SNOWPACK
! SNOWPACK (ESD) REDUCED BY ESNOW2 (DEPTH OF SUBLIMATED SNOW)
! ----------------------------------------------------------------------
ELSE
ESD = ESD-ESNOW2
SEH = RCH * (T1- TH2)
T14 = ( T1 * T1 ) * ( T1 * T1 )
FLX3 = FDOWN - FLX1- FLX2- EMISSI*SIGMA * T14- SSOIL - SEH - ETANRG
IF (FLX3 <= 0.0) FLX3 = 0.0
! ----------------------------------------------------------------------
! SNOWMELT REDUCTION DEPENDING ON SNOW COVER
! ----------------------------------------------------------------------
EX = FLX3*0.001/ LSUBF
! ----------------------------------------------------------------------
! ESDMIN REPRESENTS A SNOWPACK DEPTH THRESHOLD VALUE BELOW WHICH WE
! CHOOSE NOT TO RETAIN ANY SNOWPACK, AND INSTEAD INCLUDE IT IN SNOWMELT.
! ----------------------------------------------------------------------
SNOMLT = EX * DT
IF (ESD- SNOMLT >= ESDMIN) THEN
ESD = ESD- SNOMLT
ELSE
!
! SNOWMELT EXCEEDS SNOW DEPTH
!
EX = ESD / DT
FLX3 = EX *1000.0* LSUBF
SNOMLT = ESD
ESD = 0.0
ENDIF
ENDIF
! ----------------------------------------------------------------------
! END OF 'T12 .LE. TFREEZ' IF-BLOCK
! ----------------------------------------------------------------------
ENDIF
! ----------------------------------------------------------------------
! FOR SEA-ICE, THE SNOWMELT WILL BE ADDED TO SUBSURFACE
! RUNOFF/BASEFLOW LATER NEAR THE END OF SFLX (AFTER RETURN FROM CALL TO
! SUBROUTINE SNOPAC)
! ----------------------------------------------------------------------
! ----------------------------------------------------------------------
! SET THE EFFECTIVE POTNL EVAPOTRANSP (ETP1) TO ZERO SINCE THIS IS SNOW
! CASE, SO SURFACE EVAP NOT CALCULATED FROM EDIR IN SMFLX (BELOW).
! IF SEAICE (ICE==1) SKIP CALL TO SMFLX, SINCE NO SOIL MEDIUM FOR SEA-ICE
! ----------------------------------------------------------------------
! ----------------------------------------------------------------------
! BEFORE CALL SHFLX IN THIS SNOWPACK CASE, SET ZZ1 AND YY ARGUMENTS TO
! SPECIAL VALUES THAT ENSURE THAT GROUND HEAT FLUX CALCULATED IN SHFLX
! MATCHES THAT ALREADY COMPUTED FOR BELOW THE SNOWPACK, THUS THE SFC
! HEAT FLUX TO BE COMPUTED IN SHFLX WILL EFFECTIVELY BE THE FLUX AT THE
! SNOW TOP SURFACE.
! ----------------------------------------------------------------------
ZZ1 = 1.0
YY = STC (1) -0.5* SSOIL * ZSOIL (1)* ZZ1/ DF1
! ----------------------------------------------------------------------
! SHFLX WILL CALC/UPDATE THE ICE TEMPS.
! ----------------------------------------------------------------------
CALL SHFLX (STC,NSOIL,DT,YY,ZZ1,ZSOIL,TBOT,DF1)
! ----------------------------------------------------------------------
! SNOW DEPTH AND DENSITY ADJUSTMENT BASED ON SNOW COMPACTION. YY IS
! ASSUMED TO BE THE SOIL TEMPERTURE AT THE TOP OF THE SOIL COLUMN.
! ----------------------------------------------------------------------
SELECT CASE ( SEAICE_ALBEDO_OPT )
CASE DEFAULT
IF (ESD .GE. 0.01) THEN
CALL SNOWPACK (ESD,DT,SNOWH,SNDENS,T1,YY)
ELSE
ESD = 0.01
SNOWH = 0.05
!KWM???? SNDENS =
!KWM???? SNCOND =
SNCOVR = 1.0
ENDIF
CASE ( 1 ) ! Arctic sea-ice albedo from Mills (2011)
IF ( ESD >= 0.0001 ) THEN
CALL SNOWPACK (ESD,DT,SNOWH,SNDENS,T1,YY)
ELSE
ESD = 0.0001
SNOWH = 0.0005
SNCOVR = 0.005
ENDIF
END SELECT
! ----------------------------------------------------------------------
END SUBROUTINE SNOPAC
! ----------------------------------------------------------------------
SUBROUTINE SNOWPACK (ESD,DTSEC,SNOWH,SNDENS,TSNOW,TSOIL) 4
! ----------------------------------------------------------------------
! SUBROUTINE SNOWPACK
! ----------------------------------------------------------------------
! CALCULATE COMPACTION OF SNOWPACK UNDER CONDITIONS OF INCREASING SNOW
! DENSITY, AS OBTAINED FROM AN APPROXIMATE SOLUTION OF E. ANDERSON'S
! DIFFERENTIAL EQUATION (3.29), NOAA TECHNICAL REPORT NWS 19, BY VICTOR
! KOREN, 03/25/95.
! ----------------------------------------------------------------------
! ESD WATER EQUIVALENT OF SNOW (M)
! DTSEC TIME STEP (SEC)
! SNOWH SNOW DEPTH (M)
! SNDENS SNOW DENSITY (G/CM3=DIMENSIONLESS FRACTION OF H2O DENSITY)
! TSNOW SNOW SURFACE TEMPERATURE (K)
! TSOIL SOIL SURFACE TEMPERATURE (K)
! SUBROUTINE WILL RETURN NEW VALUES OF SNOWH AND SNDENS
! ----------------------------------------------------------------------
IMPLICIT NONE
INTEGER :: IPOL, J
REAL, INTENT(IN) :: ESD, DTSEC,TSNOW,TSOIL
REAL, INTENT(INOUT) :: SNOWH, SNDENS
REAL :: BFAC,DSX,DTHR,DW,SNOWHC,PEXP, &
TAVGC,TSNOWC,TSOILC,ESDC,ESDCX
REAL, PARAMETER :: C1 = 0.01, C2 = 21.0, G = 9.81, &
KN = 4000.0
! ----------------------------------------------------------------------
! CONVERSION INTO SIMULATION UNITS
! ----------------------------------------------------------------------
SNOWHC = SNOWH *100.
ESDC = ESD *100.
DTHR = DTSEC /3600.
TSNOWC = TSNOW -273.15
TSOILC = TSOIL -273.15
! ----------------------------------------------------------------------
! CALCULATING OF AVERAGE TEMPERATURE OF SNOW PACK
! ----------------------------------------------------------------------
! ----------------------------------------------------------------------
! CALCULATING OF SNOW DEPTH AND DENSITY AS A RESULT OF COMPACTION
! SNDENS=DS0*(EXP(BFAC*ESD)-1.)/(BFAC*ESD)
! BFAC=DTHR*C1*EXP(0.08*TAVGC-C2*DS0)
! NOTE: BFAC*ESD IN SNDENS EQN ABOVE HAS TO BE CAREFULLY TREATED
! NUMERICALLY BELOW:
! C1 IS THE FRACTIONAL INCREASE IN DENSITY (1/(CM*HR))
! C2 IS A CONSTANT (CM3/G) KOJIMA ESTIMATED AS 21 CMS/G
! ----------------------------------------------------------------------
TAVGC = 0.5* (TSNOWC + TSOILC)
IF (ESDC > 1.E-2) THEN
ESDCX = ESDC
ELSE
ESDCX = 1.E-2
END IF
! DSX = SNDENS*((DEXP(BFAC*ESDC)-1.)/(BFAC*ESDC))
! ----------------------------------------------------------------------
! THE FUNCTION OF THE FORM (e**x-1)/x EMBEDDED IN ABOVE EXPRESSION
! FOR DSX WAS CAUSING NUMERICAL DIFFICULTIES WHEN THE DENOMINATOR "x"
! (I.E. BFAC*ESDC) BECAME ZERO OR APPROACHED ZERO (DESPITE THE FACT THAT
! THE ANALYTICAL FUNCTION (e**x-1)/x HAS A WELL DEFINED LIMIT AS
! "x" APPROACHES ZERO), HENCE BELOW WE REPLACE THE (e**x-1)/x
! EXPRESSION WITH AN EQUIVALENT, NUMERICALLY WELL-BEHAVED
! POLYNOMIAL EXPANSION.
! NUMBER OF TERMS OF POLYNOMIAL EXPANSION, AND HENCE ITS ACCURACY,
! IS GOVERNED BY ITERATION LIMIT "IPOL".
! IPOL GREATER THAN 9 ONLY MAKES A DIFFERENCE ON DOUBLE
! PRECISION (RELATIVE ERRORS GIVEN IN PERCENT %).
! IPOL=9, FOR REL.ERROR <~ 1.6 E-6 % (8 SIGNIFICANT DIGITS)
! IPOL=8, FOR REL.ERROR <~ 1.8 E-5 % (7 SIGNIFICANT DIGITS)
! IPOL=7, FOR REL.ERROR <~ 1.8 E-4 % ...
! ----------------------------------------------------------------------
BFAC = DTHR * C1* EXP (0.08* TAVGC - C2* SNDENS)
IPOL = 4
PEXP = 0.
! PEXP = (1. + PEXP)*BFAC*ESDC/REAL(J+1)
DO J = IPOL,1, -1
PEXP = (1. + PEXP)* BFAC * ESDCX / REAL (J +1)
END DO
PEXP = PEXP + 1.
! ----------------------------------------------------------------------
! ABOVE LINE ENDS POLYNOMIAL SUBSTITUTION
! ----------------------------------------------------------------------
! END OF KOREAN FORMULATION
! BASE FORMULATION (COGLEY ET AL., 1990)
! CONVERT DENSITY FROM G/CM3 TO KG/M3
! DSM=SNDENS*1000.0
! DSX=DSM+DTSEC*0.5*DSM*G*ESD/
! & (1E7*EXP(-0.02*DSM+KN/(TAVGC+273.16)-14.643))
! & CONVERT DENSITY FROM KG/M3 TO G/CM3
! DSX=DSX/1000.0
! END OF COGLEY ET AL. FORMULATION
! ----------------------------------------------------------------------
! SET UPPER/LOWER LIMIT ON SNOW DENSITY
! ----------------------------------------------------------------------
DSX = SNDENS * (PEXP)
IF (DSX > 0.40) DSX = 0.40
IF (DSX < 0.05) DSX = 0.05
! ----------------------------------------------------------------------
! UPDATE OF SNOW DEPTH AND DENSITY DEPENDING ON LIQUID WATER DURING
! SNOWMELT. ASSUMED THAT 13% OF LIQUID WATER CAN BE STORED IN SNOW PER
! DAY DURING SNOWMELT TILL SNOW DENSITY 0.40.
! ----------------------------------------------------------------------
SNDENS = DSX
IF (TSNOWC >= 0.) THEN
DW = 0.13* DTHR /24.
SNDENS = SNDENS * (1. - DW) + DW
IF (SNDENS >= 0.40) SNDENS = 0.40
! ----------------------------------------------------------------------
! CALCULATE SNOW DEPTH (CM) FROM SNOW WATER EQUIVALENT AND SNOW DENSITY.
! CHANGE SNOW DEPTH UNITS TO METERS
! ----------------------------------------------------------------------
END IF
SNOWHC = ESDC / SNDENS
SNOWH = SNOWHC *0.01
! ----------------------------------------------------------------------
END SUBROUTINE SNOWPACK
! ----------------------------------------------------------------------
SUBROUTINE SNOWZ0 (SNCOVR,Z0, Z0BRD, SNOWH) 4
! ----------------------------------------------------------------------
! SUBROUTINE SNOWZ0
! ----------------------------------------------------------------------
! CALCULATE TOTAL ROUGHNESS LENGTH OVER SNOW
! SNCOVR FRACTIONAL SNOW COVER
! Z0 ROUGHNESS LENGTH (m)
! Z0S SNOW ROUGHNESS LENGTH:=0.001 (m)
! ----------------------------------------------------------------------
IMPLICIT NONE
REAL, INTENT(IN) :: SNCOVR, Z0BRD
REAL, INTENT(OUT) :: Z0
REAL, PARAMETER :: Z0S=0.001
REAL, INTENT(IN) :: SNOWH
REAL :: BURIAL
REAL :: Z0EFF
!m Z0 = (1.- SNCOVR)* Z0BRD + SNCOVR * Z0S
BURIAL = 7.0*Z0BRD - SNOWH
IF(BURIAL.LE.0.0007) THEN
Z0EFF = Z0S
ELSE
Z0EFF = BURIAL/7.0
ENDIF
Z0 = (1.- SNCOVR)* Z0BRD + SNCOVR * Z0EFF
! ----------------------------------------------------------------------
END SUBROUTINE SNOWZ0
! ----------------------------------------------------------------------
SUBROUTINE SNOW_NEW (TEMP,NEWSN,SNOWH,SNDENS) 3
! ----------------------------------------------------------------------
! SUBROUTINE SNOW_NEW
! ----------------------------------------------------------------------
! CALCULATE SNOW DEPTH AND DENSITY TO ACCOUNT FOR THE NEW SNOWFALL.
! NEW VALUES OF SNOW DEPTH & DENSITY RETURNED.
! TEMP AIR TEMPERATURE (K)
! NEWSN NEW SNOWFALL (M)
! SNOWH SNOW DEPTH (M)
! SNDENS SNOW DENSITY (G/CM3=DIMENSIONLESS FRACTION OF H2O DENSITY)
! ----------------------------------------------------------------------
IMPLICIT NONE
REAL, INTENT(IN) :: NEWSN, TEMP
REAL, INTENT(INOUT) :: SNDENS, SNOWH
REAL :: DSNEW, HNEWC, SNOWHC,NEWSNC,TEMPC
! ----------------------------------------------------------------------
! CONVERSION INTO SIMULATION UNITS
! ----------------------------------------------------------------------
SNOWHC = SNOWH *100.
NEWSNC = NEWSN *100.
! ----------------------------------------------------------------------
! CALCULATING NEW SNOWFALL DENSITY DEPENDING ON TEMPERATURE
! EQUATION FROM GOTTLIB L. 'A GENERAL RUNOFF MODEL FOR SNOWCOVERED
! AND GLACIERIZED BASIN', 6TH NORDIC HYDROLOGICAL CONFERENCE,
! VEMADOLEN, SWEDEN, 1980, 172-177PP.
!-----------------------------------------------------------------------
TEMPC = TEMP -273.15
IF (TEMPC <= -15.) THEN
DSNEW = 0.05
ELSE
DSNEW = 0.05+0.0017* (TEMPC +15.)**1.5
END IF
! ----------------------------------------------------------------------
! ADJUSTMENT OF SNOW DENSITY DEPENDING ON NEW SNOWFALL
! ----------------------------------------------------------------------
HNEWC = NEWSNC / DSNEW
IF (SNOWHC + HNEWC .LT. 1.0E-3) THEN
SNDENS = MAX(DSNEW,SNDENS)
ELSE
SNDENS = (SNOWHC * SNDENS + HNEWC * DSNEW)/ (SNOWHC + HNEWC)
ENDIF
SNOWHC = SNOWHC + HNEWC
SNOWH = SNOWHC *0.01
! ----------------------------------------------------------------------
END SUBROUTINE SNOW_NEW
! ----------------------------------------------------------------------
END MODULE module_sf_noah_seaice