C $Header: /u/gcmpack/MITgcm/pkg/land/land_albedo.F,v 1.2 2007/01/31 23:02:06 dfer Exp $ C $Name: $ #include "LAND_OPTIONS.h" CBOP C !ROUTINE: LAND_DIAGNOSTICS C !INTERFACE: SUBROUTINE LAND_ALBEDO( I land_frc, grnd_alb, O alb_land, I bi,bj, myTime, myIter, myThid ) C !DESCRIPTION: \bv C *==========================================================* C | S/R LAND_ALBEDO C | o Calculate snow albedo over land C *==========================================================* C \ev C !USES: IMPLICIT NONE C == Global variables === C-- size for MITgcm & Land package : #include "LAND_SIZE.h" #include "EEPARAMS.h" #include "PARAMS.h" #include "LAND_PARAMS.h" #include "LAND_VARS.h" C !INPUT/OUTPUT PARAMETERS: C == Routine arguments == C land_frc :: land fraction [0-1] C grnd_alb :: ground albedo [0-1] C alb_land :: albedo of land (including snow effect) [0-1] C bi,bj :: Tile index C myTime :: Current time of simulation ( s ) C myIter :: Current iteration number in simulation C myThid :: Number of this instance of the routine _RS land_frc(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RS grnd_alb(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy) _RL alb_land(sNx,sNy) INTEGER bi, bj, myIter, myThid _RL myTime CEOP #ifdef ALLOW_LAND C == Local Variables == C i,j :: Loop counters C albSnow :: albedo of snow C ageSnow :: age of snow [days] INTEGER i,j _RL albSnow, ageSnow, hSnow, Tsf C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----| C- Compute albedo of snow and then albedo of land. DO j=1,sNy DO i=1,sNx alb_land(i,j) = grnd_alb(i,j,bi,bj) IF ( land_frc(i,j,bi,bj).GT.0. ) THEN Tsf = land_skinT(i,j,bi,bj) C snow age (units = days): ageSnow = land_snowAge(i,j,bi,bj)/86400. _d 0 hSnow = land_hSnow(i,j,bi,bj) C-------------------------------------------- C--- taken from thsice/thsice_albedo.F : C- New snow: (linear) transition between tempSnowAlbL (oC) and 0.oC C from cold/dry snow albedo to warm/wet snow albedo IF ( tempSnowAlbL.LT.0. _d 0 ) THEN albSnow = albColdSnow & + (albWarmSnow - albColdSnow) & *MAX( 0. _d 0, MIN(1. _d 0 - Tsf/tempSnowAlbL, 1. _d 0) ) ELSE albSnow = albColdSnow ENDIF C- albedo of snow is function of snow-age albSnow = albOldSnow & +(albSnow-albOldSnow)*exp(-0.2 _d 0*ageSnow) C- layer of snow over the ground: alb_land(i,j) = albSnow & +(alb_land(i,j)-albSnow)*exp(-hSnow/hAlbSnow) C-------------------------------------------- ENDIF ENDDO ENDDO C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----| #endif /* ALLOW_LAND */ RETURN END