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C $Header: /u/gcmpack/MITgcm/pkg/seaice/seaice_freedrift.F,v 1.2 2010/10/07 19:54:45 gforget Exp $ |
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C $Name: $ |
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|
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#include "SEAICE_OPTIONS.h" |
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|
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CBOP |
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SUBROUTINE SEAICE_FREEDRIFT( myTime, myIter, myThid ) |
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C /==========================================================\ |
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C | SUBROUTINE SEAICE_FREEDRIFT | |
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C | o Solve ice approximate momentum equation analytically | |
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C \==========================================================/ |
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IMPLICIT NONE |
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|
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C === Global variables === |
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#include "SIZE.h" |
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#include "EEPARAMS.h" |
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#include "PARAMS.h" |
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#include "DYNVARS.h" |
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#include "GRID.h" |
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#include "SEAICE.h" |
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#include "SEAICE_PARAMS.h" |
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|
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#ifdef ALLOW_AUTODIFF_TAMC |
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# include "tamc.h" |
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#endif |
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|
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C === Routine arguments === |
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C myTime :: Simulation time |
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C myIter :: Simulation timestep number |
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C myThid :: my Thread Id. number |
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_RL myTime |
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INTEGER myIter |
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INTEGER myThid |
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CEOP |
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|
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#ifdef SEAICE_ALLOW_FREEDRIFT |
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#ifdef SEAICE_CGRID |
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|
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C === Local variables === |
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INTEGER i, j, kSrf, bi, bj |
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|
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_RL tmpscal1,tmpscal2,tmpscal3,tmpscal4 |
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|
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_RL taux_onIce_cntr, tauy_onIce_cntr, uvel_cntr, vvel_cntr |
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_RL mIceCor, rhs_x, rhs_y, rhs_n, rhs_a, sol_n, sol_a |
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|
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_RL uice_cntr(1-Olx:sNx+Olx,1-Oly:sNy+Oly,nSx,nSy) |
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_RL vice_cntr(1-Olx:sNx+Olx,1-Oly:sNy+Oly,nSx,nSy) |
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|
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|
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kSrf=1 |
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|
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c initialize fields: |
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c ================== |
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|
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DO bj=myByLo(myThid),myByHi(myThid) |
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DO bi=myBxLo(myThid),myBxHi(myThid) |
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DO j=1-OLy,sNy+OLy |
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DO i=1-OLx,sNx+OLx |
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uice_fd(i,j,bi,bj)=0. _d 0 |
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vice_fd(i,j,bi,bj)=0. _d 0 |
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uice_cntr(i,j,bi,bj)=0. _d 0 |
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Vice_cntr(i,j,bi,bj)=0. _d 0 |
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ENDDO |
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ENDDO |
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ENDDO |
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ENDDO |
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|
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CALL EXCH_UV_XY_RL( TAUX, TAUY, .TRUE., myThid ) |
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|
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|
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DO bj=myByLo(myThid),myByHi(myThid) |
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DO bi=myBxLo(myThid),myBxHi(myThid) |
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DO j=1,sNy |
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DO i=1,sNx |
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|
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c preliminary computations: |
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c ========================= |
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c factor to convert air-sea stress to air-ice stresss |
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IF ( YC(I,J,bi,bj) .LT. ZERO ) THEN |
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tmpscal1 = SEAICE_drag_south/OCEAN_drag |
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ELSE |
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tmpscal1 = SEAICE_drag /OCEAN_drag |
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ENDIF |
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c air-ice stress at cell center |
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taux_onIce_cntr= |
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& tmpscal1*HALF*(TAUX(i,j,bi,bj)+TAUX(i+1,j,bi,bj)) |
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tauy_onIce_cntr= |
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& tmpscal1*HALF*(TAUY(i,j,bi,bj)+TAUY(i,j+1,bi,bj)) |
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c mass of ice per unit area (kg/m2) times coriolis f |
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mIceCor=SEAICE_rhoIce*HEFF(i,j,bi,bj)*_fCori(I,J,bi,bj) |
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c ocean velocity at cell center |
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uvel_cntr=HALF*(uvel(i,j,kSrf,bi,bj)+uvel(i+1,j,kSrf,bi,bj)) |
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vvel_cntr=HALF*(vvel(i,j,kSrf,bi,bj)+vvel(i,j+1,kSrf,bi,bj)) |
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c right hand side of free drift equation: |
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rhs_x= -taux_onIce_cntr -mIceCor*vvel_cntr |
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rhs_y= -tauy_onIce_cntr +mIceCor*uvel_cntr |
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|
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c norm of angle of rhs |
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tmpscal1=rhs_x*rhs_x + rhs_y*rhs_y |
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if (tmpscal1.GT.0.) then |
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rhs_n=sqrt( rhs_x*rhs_x + rhs_y*rhs_y ) |
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rhs_a=atan2(rhs_y,rhs_x) |
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else |
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rhs_n=0. _d 0 |
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rhs_a=0. _d 0 |
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endif |
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|
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c solve for norm: |
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c =============== |
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IF ( YC(I,J,bi,bj) .LT. ZERO ) THEN |
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tmpscal1 = 1. _d 0 /SEAICE_waterDrag_south |
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ELSE |
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tmpscal1 = 1. _d 0 /SEAICE_waterDrag |
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ENDIF |
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c polynomial coefficients |
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tmpscal2= +tmpscal1*tmpscal1*mIceCor*mIceCor |
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tmpscal3= -tmpscal1*tmpscal1*rhs_n*rhs_n |
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c discriminant |
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tmpscal4=tmpscal2*tmpscal2-4*tmpscal3 |
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if (tmpscal4.GT.0) then |
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sol_n=sqrt(HALF*(sqrt(tmpscal4)-tmpscal2)) |
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else |
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sol_n=0. _d 0 |
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endif |
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|
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c solve for angle: |
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c ================ |
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IF ( YC(I,J,bi,bj) .LT. ZERO ) THEN |
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tmpscal1 = SEAICE_waterDrag_south |
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ELSE |
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tmpscal1 = SEAICE_waterDrag |
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ENDIF |
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c |
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tmpscal2= tmpscal1*sol_n*sol_n |
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tmpscal3= mIceCor*sol_n |
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c |
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tmpscal4=tmpscal2*tmpscal2 + tmpscal3*tmpscal3 |
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if (tmpscal4.GT.0) then |
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sol_a=rhs_a-atan2(tmpscal3,tmpscal2) |
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else |
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sol_a=0. _d 0 |
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endif |
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|
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c compute uice, vice at cell center: |
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c ================================== |
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uice_cntr(i,j,bi,bj)=uvel_cntr-sol_n*cos(sol_a) |
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vice_cntr(i,j,bi,bj)=vvel_cntr-sol_n*sin(sol_a) |
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|
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ENDDO |
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ENDDO |
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ENDDO |
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ENDDO |
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|
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|
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c interpolated to velocity points: |
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c ================================ |
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|
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CALL EXCH_UV_AGRID_3D_RL(uice_cntr,vice_cntr,.TRUE.,1,myThid) |
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|
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DO bj=myByLo(myThid),myByHi(myThid) |
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DO bi=myBxLo(myThid),myBxHi(myThid) |
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DO j=1,sNy |
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DO i=1,sNx |
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uice_fd(i,j,bi,bj)=HALF* |
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& (uice_cntr(i-1,j,bi,bj)+uice_cntr(i,j,bi,bj)) |
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vice_fd(i,j,bi,bj)=HALF* |
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& (vice_cntr(i,j-1,bi,bj)+vice_cntr(i,j,bi,bj)) |
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ENDDO |
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ENDDO |
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ENDDO |
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ENDDO |
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|
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CALL EXCH_UV_XY_RL( uice_fd, vice_fd, .TRUE., myThid ) |
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|
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C Apply masks (same/similar to seaice_evp.F/seaice_lsr.F) |
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DO bj=myByLo(myThid),myByHi(myThid) |
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DO bi=myBxLo(myThid),myBxHi(myThid) |
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DO j=1-Oly,sNy+Oly |
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DO i=1-Olx,sNx+Olx |
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uIce_fd(i,j,bi,bj)=uIce_fd(i,j,bi,bj)* _maskW(i,j,kSrf,bi,bj) |
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vIce_fd(i,j,bi,bj)=vIce_fd(i,j,bi,bj)* _maskS(i,j,kSrf,bi,bj) |
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ENDDO |
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ENDDO |
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ENDDO |
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ENDDO |
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|
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#endif /* SEAICE_CGRID */ |
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#endif /* SEAICE_ALLOW_FREEDRIFT */ |
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RETURN |
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END |
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