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C $Header: /u/gcmpack/MITgcm/pkg/zonal_filt/zonal_filt_init.F,v 1.5 2001/12/11 14:50:14 jmc Exp $ |
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C $Name: $ |
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#include "ZONAL_FILT_OPTIONS.h" |
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SUBROUTINE ZONAL_FILT_INIT(myThid) |
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C /==========================================================\ |
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C | S/R ZONAL_FILT_INIT | |
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C | o Initialise FFT filter for latitude circle. | |
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C |==========================================================| |
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C | The details of particular FFT libraries may differ. | |
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C | Changing to a different library may entail modifying the | |
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C | code here. However, the broad process is usually the | |
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C | same. | |
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C | Note - Fourier modes for sNx and sNx+1 are damped in the | |
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C | same way. This is because we have not implemented | |
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C | a scheme that sets the damping factor for the | |
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C | highest wave number for odd sNx. Instead the | |
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C | highest wave number for odd sNx. Instead only | |
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C | wave numbers 1:INT(sNx/2) are partially damped. | |
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C | Wave number sNx/2 (if it exists) is removed | |
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C | altogether. | |
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C \==========================================================/ |
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IMPLICIT NONE |
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C == Global data == |
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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 "GRID.h" |
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#include "ZONAL_FILT.h" |
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#include "FFTPACK.h" |
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C == Routine arguments == |
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C myThid - Thread number of this instance of FILTER_LATCIRC_FFT_INIT |
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INTEGER myThid |
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#ifdef ALLOW_ZONAL_FILT |
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C == Local variables == |
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C alpha - Used to evaluate frequency and latitude dependent |
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C amplitude damping factor. |
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C wvNum - Wave number |
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C lat - Temporary holding latitude |
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C nWv - No. of waves that fit on grid. |
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_RL alpha, wvNum, lat |
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INTEGER I, J, bi, bj, nPoints, nWv |
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_RL one |
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PARAMETER( one = 1.0 ) |
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_RS ampfact,Y |
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ampfact(Y,I) = min( one, |
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& ( cos( abs(Y)*deg2rad ) |
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& /cos( zonal_filt_lat*deg2rad ) )**zonal_filt_cospow |
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& /(sin( PI*float(I)/float(Nx) ) )**zonal_filt_sinpow |
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& ) |
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_BEGIN_MASTER(myThid) |
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C o Initialise specific library FFT package |
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DO bj=1,nSy |
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C CALL R8FFTI( Nx, FFTPACKWS(1,bj) ) |
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CALL R8FFTI1( Nx, FFTPACKWS2(1,bj), FFTPACKWS3(1,bj) ) |
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ENDDO |
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C o Set amplitude scale factor as function of latitude and mode number |
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DO bj=1,nSy |
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DO bi=1,nSx |
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DO j=1-oLy,sNy+Oly |
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ampFactor(1,J,bi,bj) = one |
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ampFactorV(1,J,bi,bj) = one |
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DO i=1,Nx/2-1 |
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ampFactor(2*I,J,bi,bj) = ampfact( yC(1,J,bi,bj) , I ) |
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C IF (ampFactor(2*I,J,bi,bj).LE..9) ampFactor(2*I,J,bi,bj)=0. |
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ampFactor(2*I+1,J,bi,bj) = ampFactor(2*I,J,bi,bj) |
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ampFactorV(2*I,J,bi,bj) = ampfact( yG(1,J,bi,bj) , I ) |
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C IF (ampFactorV(2*I,J,bi,bj).LE..9) ampFactorV(2*I,J,bi,bj)=0. |
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ampFactorV(2*I+1,J,bi,bj) = ampFactorV(2*I,J,bi,bj) |
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ENDDO |
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I=Nx/2 |
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IF ( zonal_filt_mode2dx.EQ.0 ) THEN |
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ampFactor(Nx,J,bi,bj) = ampfact( yC(1,J,bi,bj) , I ) |
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ampFactorV(Nx,J,bi,bj) = ampfact( yG(1,J,bi,bj) , I ) |
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ELSE |
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ampFactor(Nx,J,bi,bj) = 0. |
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ampFactorV(Nx,J,bi,bj) = 0. |
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ENDIF |
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ENDDO |
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ENDDO |
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ENDDO |
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_END_MASTER(myThid) |
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CALL BAR2(myThid) |
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CALL WRITE_REC_XY_RL( 'ampFactor', ampFactor, 1, 0, myThid ) |
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#endif /* ALLOW_ZONAL_FILT */ |
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RETURN |
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END |
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