C $Header: /u/gcmpack/MITgcm/pkg/thsice/thsice_albedo.F,v 1.6 2009/07/08 23:35:05 jmc Exp $
C $Name: $
#include "THSICE_OPTIONS.h"
CBOP
C !ROUTINE: THSICE_ALBEDO
C !INTERFACE:
SUBROUTINE THSICE_ALBEDO(
I bi, bj, siLo, siHi, sjLo, sjHi,
I iMin,iMax, jMin,jMax,
I iceMask, hIce, hSnow, tSrf, ageSnw,
O sAlb, sAlbNIR,
I myTime, myIter, myThid )
C !DESCRIPTION: \bv
C *==========================================================*
C | S/R THSICE_ALBEDO
C *==========================================================*
C | Compute surface albedo over sea-ice
C *==========================================================*
C \ev
C !USES:
IMPLICIT NONE
C == Global data ==
#include "EEPARAMS.h"
#include "THSICE_PARAMS.h"
C !INPUT/OUTPUT PARAMETERS:
C == Routine Arguments ==
C siLo,siHi :: size of input/output array: 1rst dim. lower,higher bounds
C sjLo,sjHi :: size of input/output array: 2nd dim. lower,higher bounds
C bi,bj :: tile indices
C iMin,iMax :: computation domain: 1rst index range
C jMin,jMax :: computation domain: 2nd index range
C--- Input:
C iceMask :: sea-ice fractional mask [0-1]
C hIce (hi) :: ice height [m]
C hSnow (hs) :: snow height [m]
C tSrf (Tsf) :: surface (ice or snow) temperature [oC]
C ageSnw (age) :: snow age [s]
C--- Output
C sAlb (albedo) :: surface albedo [0-1]
C sAlbNIR(albedo):: near IR surface albedo [0-1]
C--- Input:
C myTime :: current Time of simulation [s]
C myIter :: current Iteration number in simulation
C myThid :: my Thread Id number
INTEGER siLo, siHi, sjLo, sjHi
INTEGER bi,bj
INTEGER iMin, iMax
INTEGER jMin, jMax
_RL iceMask(siLo:siHi,sjLo:sjHi)
_RL hIce (siLo:siHi,sjLo:sjHi)
_RL hSnow (siLo:siHi,sjLo:sjHi)
_RL tSrf (siLo:siHi,sjLo:sjHi)
_RL ageSnw (siLo:siHi,sjLo:sjHi)
_RL sAlb (siLo:siHi,sjLo:sjHi)
_RL sAlbNIR(siLo:siHi,sjLo:sjHi)
_RL myTime
INTEGER myIter
INTEGER myThid
CEOP
#ifdef ALLOW_THSICE
C !LOCAL VARIABLES:
C--- local copy of input/output argument list variables (see description above)
_RL hi ! ice height
_RL hs ! snow height
_RL Tsf ! surface temperature
_RL age ! snow age
_RL albedo ! surface albedo
C == Local variables ==
C frsnow :: fractional snow cover
C albsno :: albedo of snow
C albice :: albedo of ice
C albNewSnow :: albedo of new (fresh) snow
C albNewSnow :: albedo of new (fresh) snow
C msgBuf :: Informational/error meesage buffer
c _RL frsnow
_RL albsno, albice
_RL albNewSnow
_RL albNIR_ocean, albNIR_thick, albNIR_dsnow
_RL albNIR_ice, albNIR_fHice, recFac_albNIR
INTEGER i,j
CHARACTER*(MAX_LEN_MBUF) msgBuf
C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----|
IF ( thSIce_calc_albNIR ) THEN
C Near-InfraRed albedo
albNIR_ocean = 0.06 _d 0
albNIR_thick = 0.33 _d 0
albNIR_dsnow = 0.68 _d 0
albNIR_fHice = 4. _d 0
recFac_albNIR = 1. _d 0 / ATAN(albNIR_fHice*0.5 _d 0)
ENDIF
DO j = jMin, jMax
DO i = iMin, iMax
IF ( iceMask(i,j).GT.0. _d 0 ) THEN
hi = hIce(i,j)
hs = hSnow(i,j)
Tsf = tSrf(i,j)
age = ageSnw(i,j)
C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----|
C-- Albedo of Bare Sea-Ice
albice = albIceMax + (albIceMin-albIceMax)*EXP(-hi/hAlbIce)
C-- LANL albedo calculation
c frsnow = 0.
c if (hs .gt. 0.) frsnow = 1.
c if (Tsf .lt. 0.) then
c albedo = frsnow*albColdSnow + (1.-frsnow)*albice
c else
c albedo = frsnow*albWarmSnow + (1.-frsnow)*albice
c endif
C-end LANL albedo calculation
C-- GISS model albedo calculation
c albice = 0.7 _d 0
C- New snow: (linear) transition between tempSnowAlb (oC) and 0.oC
C from cold/dry snow albedo to warm/wet snow albedo
IF ( tempSnowAlb.LT.0. _d 0 ) THEN
albNewSnow = albColdSnow
& + (albWarmSnow - albColdSnow)
& *MAX( 0. _d 0, MIN(1. _d 0 - Tsf/tempSnowAlb, 1. _d 0) )
ELSE
albNewSnow = albColdSnow
ENDIF
C- albedo of snow is function of snow-age (make age units into days):
albsno = albOldSnow
& +(albNewSnow-albOldSnow)*EXP(-0.2 _d 0*age/86400. _d 0)
C- layer of snow over the ice:
albedo = albsno + (albice-albsno)*EXP(-hs/hAlbSnow)
IF ( thSIce_calc_albNIR ) THEN
C-- Compute near-infrared albedo
albNIR_ice = albNIR_ocean + (albNIR_thick - albNIR_ocean)*
& MIN( recFac_albNIR*ATAN(albNIR_fHice*hi), 1. _d 0 )
& + 0.075 _d 0 * MIN( -Tsf - 1. _d 0, 0. _d 0 )
sAlbNIR(i,j) = albNIR_ice * ( 1. _d 0 - hs/(hs + 0.02 _d 0) )
& + ( albNIR_dsnow + 0.15 _d 0 *MIN( -Tsf - 1. _d 0, 0. _d 0) )
& * hs/(hs + 0.02 _d 0)
ELSE
sAlbNIR(i,j) = albedo
ENDIF
C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----|
IF (albedo.GT.1. _d 0 .OR. albedo.LT. .2 _d 0) THEN
c print*,'QQ - albedo problem', albedo, age, hs, albsno
WRITE(msgBuf,'(A,I10,4I6)')
& 'THSICE_ALBEDO: Problem at:', myIter,i,j,bi,bj
CALL PRINT_ERROR( msgBuf , myThid)
WRITE(msgBuf,'(A,1P4E17.9)')
& 'THSICE_ALBEDO: albedo=', albedo, age, hs, albsno
CALL PRINT_ERROR( msgBuf , myThid)
STOP 'THSICE_ALBEDO: albedo out of range'
ENDIF
sAlb(i,j) = albedo
ELSE
sAlb(i,j) = 0. _d 0
sAlbNIR(i,j) = 0. _d 0
ENDIF
ENDDO
ENDDO
#endif /* ALLOW_THSICE */
C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----|
RETURN
END