source: LMDZ6/branches/Amaury_dev/libf/dyn3d_common/ppm3d.f90 @ 5185

! $Id: ppm3d.f90 5160 2024-08-03 12:56:58Z abarral $

!From lin@explorer.gsfc.nasa.gov Wed Apr 15 17:44:44 1998
!Date: Wed, 15 Apr 1998 11:37:03 -0400
!From: lin@explorer.gsfc.nasa.gov
!To: Frederic.Hourdin@lmd.jussieu.fr
!Subject: 3D transport module of the GSFC CTM and GEOS GCM


!This code is sent to you by S-J Lin, DAO, NASA-GSFC

!Note: this version is intended for machines like CRAY
!-90. No multitasking directives implemented.


! ********************************************************************

! TransPort Core for Goddard Chemistry Transport Model (G-CTM), Goddard
! Earth Observing System General Circulation Model (GEOS-GCM), and Data
! Assimilation System (GEOS-DAS).

! ********************************************************************

! Purpose: given horizontal winds on  a hybrid sigma-p surfaces,
!      one CALL to tpcore updates the 3-D mixing ratio
!      fields one time step (NDT). [vertical mass flux is computed
!      internally consistent with the discretized hydrostatic mass
!      continuity equation of the C-Grid GEOS-GCM (for IGD=1)].

! Schemes: Multi-dimensional Flux Form Semi-Lagrangian (FFSL) scheme based
!      on the van Leer or PPM.
!      (see Lin and Rood 1996).
! Version 4.5
! Last modified: Dec. 5, 1996
! Major changes from version 4.0: a more general vertical hybrid sigma-
! pressure coordinate.
! Subroutines modified: xtp, ytp, fzppm, qckxyz
! Subroutines deleted: vanz

! Author: Shian-Jiann Lin
! mail address:
!             Shian-Jiann Lin*
!             Code 910.3, NASA/GSFC, Greenbelt, MD 20771
!             Phone: 301-286-9540
!             E-mail: lin@dao.gsfc.nasa.gov

! *affiliation:
!             Joint Center for Earth Systems Technology
!             The University of Maryland Baltimore County
!             NASA - Goddard Space Flight Center
! References:

! 1. Lin, S.-J., and R. B. Rood, 1996: Multidimensional flux form semi-
!    Lagrangian transport schemes. Mon. Wea. Rev., 124, 2046-2070.

! 2. Lin, S.-J., W. C. Chao, Y. C. Sud, and G. K. Walker, 1994: A class of
!    the van Leer-type transport schemes and its applications to the moist-
!    ure transport in a General Circulation Model. Mon. Wea. Rev., 122,
!    1575-1593.

! ****6***0*********0*********0*********0*********0*********0**********72

SUBROUTINE ppm3d(IGD,Q,PS1,PS2,U,V,W,NDT,IORD,JORD,KORD,NC,IMR, &
        JNP,j1,NLAY,AP,BP,PT,AE,fill,dum,Umax)

  IMPLICIT NONE

  ! rajout de déclarations
  !  integer Jmax,kmax,ndt0,nstep,k,j,i,ic,l,js,jn,imh,iad,jad,krd
  !  integer iu,iiu,j2,jmr,js0,jt
  !  real dtdy,dtdy5,rcap,iml,jn0,imjm,pi,dl,dp
  !  real dt,cr1,maxdt,ztc,d5,sum1,sum2,ru

  ! ********************************************************************

  ! =============
  ! INPUT:
  ! =============

  ! Q(IMR,JNP,NLAY,NC): mixing ratios at current time (t)
  ! NC: total # of constituents
  ! IMR: first dimension (E-W); # of Grid intervals in E-W is IMR
  ! JNP: 2nd dimension (N-S); # of Grid intervals in N-S is JNP-1
  ! NLAY: 3rd dimension (# of layers); vertical index increases from 1 at
  !   the model top to NLAY near the surface (see fig. below).
  !   It is assumed that 6 <= NLAY <= JNP (for dynamic memory allocation)

  ! PS1(IMR,JNP): surface pressure at current time (t)
  ! PS2(IMR,JNP): surface pressure at mid-time-level (t+NDT/2)
  ! PS2 is replaced by the predicted PS (at t+NDT) on output.
  ! Note: surface pressure can have any unit or can be multiplied by any
  !   const.

  ! The pressure at layer edges are defined as follows:

  !    p(i,j,k) = AP(k)*PT  +  BP(k)*PS(i,j)          (1)

  ! Where PT is a constant having the same unit as PS.
  ! AP and BP are unitless constants given at layer edges
  ! defining the vertical coordinate.
  ! BP(1) = 0., BP(NLAY+1) = 1.
  ! The pressure at the model top is PTOP = AP(1)*PT

  ! For pure sigma system set AP(k) = 1 for all k, PT = PTOP,
  ! BP(k) = sige(k) (sigma at edges), PS = Psfc - PTOP.

  ! Note: the sigma-P coordinate is a subset of Eq. 1, which in turn
  ! is a subset of the following even more general sigma-P-thelta coord.
  ! currently under development.
  !  p(i,j,k) = (AP(k)*PT + BP(k)*PS(i,j))/(D(k)-C(k)*TE**(-1/kapa))

  !              /////////////////////////////////
  !          / \ ------------- PTOP --------------  AP(1), BP(1)
  !           |
  !    delp(1)    |  ........... Q(i,j,1) ............
  !           |
  !  W(1)    \ / ---------------------------------  AP(2), BP(2)



  ! W(k-1)   / \ ---------------------------------  AP(k), BP(k)
  !           |
  !    delp(K)    |  ........... Q(i,j,k) ............
  !           |
  !  W(k)    \ / ---------------------------------  AP(k+1), BP(k+1)



  !          / \ ---------------------------------  AP(NLAY), BP(NLAY)
  !           |
  !  delp(NLAY)   |  ........... Q(i,j,NLAY) .........
  !           |
  !   W(NLAY)=0  \ / ------------- surface ----------- AP(NLAY+1), BP(NLAY+1)
  !             //////////////////////////////////

  ! U(IMR,JNP,NLAY) & V(IMR,JNP,NLAY):winds (m/s) at mid-time-level (t+NDT/2)
  ! U and V may need to be polar filtered in advance in some cases.

  ! IGD:      grid type on which winds are defined.
  ! IGD = 0:  A-Grid  [all variables defined at the same point from south
  !               pole (j=1) to north pole (j=JNP) ]

  ! IGD = 1  GEOS-GCM C-Grid
  !                                  [North]

  !                                   V(i,j)
  !                                      |
  !                                      |
  !                                      |
  !                         U(i-1,j)---Q(i,j)---U(i,j) [EAST]
  !                                      |
  !                                      |
  !                                      |
  !                                   V(i,j-1)

  !     U(i,  1) is defined at South Pole.
  !     V(i,  1) is half grid north of the South Pole.
  !     V(i,JMR) is half grid south of the North Pole.

  !     V must be defined at j=1 and j=JMR if IGD=1
  !     V at JNP need not be given.

  ! NDT: time step in seconds (need not be constant during the course of
  !  the integration). Suggested value: 30 min. for 4x5, 15 min. for 2x2.5
  !  (Lat-Lon) resolution. Smaller values are recommanded if the model
  !  has a well-resolved stratosphere.

  ! J1 defines the size of the polar cap:
  ! South polar cap edge is located at -90 + (j1-1.5)*180/(JNP-1) deg.
  ! North polar cap edge is located at  90 - (j1-1.5)*180/(JNP-1) deg.
  ! There are currently only two choices (j1=2 or 3).
  ! IMR must be an even integer if j1 = 2. Recommended value: J1=3.

  ! IORD, JORD, and KORD are integers controlling various options in E-W, N-S,
  ! and vertical transport, respectively. Recommended values for positive
  ! definite scalars: IORD=JORD=3, KORD=5. Use KORD=3 for non-
  ! positive definite scalars or when linear correlation between constituents
  ! is to be maintained.

  !  _ORD=
  !    1: 1st order upstream scheme (too diffusive, not a useful option; it
  !       can be used for debugging purposes; this is THE only known "linear"
  !       monotonic advection scheme.).
  !    2: 2nd order van Leer (full monotonicity constraint;
  !       see Lin et al 1994, MWR)
  !    3: monotonic PPM* (slightly improved PPM of Collela & Woodward 1984)
  !    4: semi-monotonic PPM (same as 3, but overshoots are allowed)
  !    5: positive-definite PPM (constraint on the subgrid distribution is
  !       only strong enough to prevent generation of negative values;
  !       both overshoots & undershoots are possible).
  !    6: un-constrained PPM (nearly diffusion free; slightly faster but
  !       positivity not quaranteed. Use this option only when the fields
  !       and winds are very smooth).

  ! *PPM: Piece-wise Parabolic Method

  ! Note that KORD <=2 options are no longer supported. DO not use option 4 or 5.
  ! for non-positive definite scalars (such as Ertel Potential Vorticity).

  ! The implicit numerical diffusion decreases as _ORD increases.
  ! The last two options (ORDER=5, 6) should only be used when there is
  ! significant explicit diffusion (such as a turbulence parameterization). You
  ! might get dispersive results otherwise.
  ! No filter of any kind is applied to the constituent fields here.

  ! AE: Radius of the sphere (meters).
  ! Recommended value for the planet earth: 6.371E6

  ! fill(logical):   flag to do filling for negatives (see note below).

  ! Umax: Estimate (upper limit) of the maximum U-wind speed (m/s).
  ! (220 m/s is a good value for troposphere model; 280 m/s otherwise)

  ! =============
  ! Output
  ! =============

  ! Q: mixing ratios at future time (t+NDT) (original values are over-written)
  ! W(NLAY): large-scale vertical mass flux as diagnosed from the hydrostatic
  !      relationship. W will have the same unit as PS1 and PS2 (eg, mb).
  !      W must be divided by NDT to get the correct mass-flux unit.
  !      The vertical Courant number C = W/delp_UPWIND, where delp_UPWIND
  !      is the pressure thickness in the "upwind" direction. For example,
  !      C(k) = W(k)/delp(k)   if W(k) > 0;
  !      C(k) = W(k)/delp(k+1) if W(k) < 0.
  !          ( W > 0 is downward, ie, toward surface)
  ! PS2: predicted PS at t+NDT (original values are over-written)

  ! ********************************************************************
  ! NOTES:
  ! This forward-in-time upstream-biased transport scheme reduces to
  ! the 2nd order center-in-time center-in-space mass continuity eqn.
  ! if Q = 1 (constant fields will remain constant). This also ensures
  ! that the computed vertical velocity to be identical to GEOS-1 GCM
  ! for on-line transport.

  ! A larger polar cap is used if j1=3 (recommended for C-Grid winds or when
  ! winds are noisy near poles).

  ! Flux-Form Semi-Lagrangian transport in the East-West direction is used
  ! when and where Courant # is greater than one.

  ! The user needs to change the parameter Jmax or Kmax if the resolution
  ! is greater than 0.5 deg in N-S or 150 layers in the vertical direction.
  ! (this TransPort Core is otherwise resolution independent and can be used
  ! as a library routine).

  ! PPM is 4th order accurate when grid spacing is uniform (x & y); 3rd
  ! order accurate for non-uniform grid (vertical sigma coord.).

  ! Time step is limitted only by transport in the meridional direction.
  ! (the FFSL scheme is not implemented in the meridional direction).

  ! Since only 1-D limiters are applied, negative values could
  ! potentially be generated when large time step is used and when the
  ! initial fields contain discontinuities.
  ! This does not necessarily imply the integration is unstable.
  ! These negatives are typically very small. A filling algorithm is
  ! activated if the user set "fill" to be true.

  ! The van Leer scheme used here is nearly as accurate as the original PPM
  ! due to the use of a 4th order accurate reference slope. The PPM imple-
  ! mented here is an improvement over the original and is also based on
  ! the 4th order reference slope.

  ! ****6***0*********0*********0*********0*********0*********0**********72

  ! User modifiable parameters

  INTEGER,parameter :: Jmax = 361, kmax = 150

  ! ****6***0*********0*********0*********0*********0*********0**********72

  ! Input-Output arrays
  !

  REAL :: Q(IMR,JNP,NLAY,NC),PS1(IMR,JNP),PS2(IMR,JNP), &
        U(IMR,JNP,NLAY),V(IMR,JNP,NLAY),AP(NLAY+1), &
        BP(NLAY+1),W(IMR,JNP,NLAY),NDT,val(NLAY),Umax
  INTEGER :: IGD,IORD,JORD,KORD,NC,IMR,JNP,j1,NLAY,AE
  INTEGER :: IMRD2
  REAL :: PT
  LOGICAL :: cross, fill, dum

  ! Local dynamic arrays

  REAL :: CRX(IMR,JNP),CRY(IMR,JNP),xmass(IMR,JNP),ymass(IMR,JNP), &
        fx1(IMR+1),DPI(IMR,JNP,NLAY),delp1(IMR,JNP,NLAY), &
        WK1(IMR,JNP,NLAY),PU(IMR,JNP),PV(IMR,JNP),DC2(IMR,JNP), &
        delp2(IMR,JNP,NLAY),DQ(IMR,JNP,NLAY,NC),VA(IMR,JNP), &
        UA(IMR,JNP),qtmp(-IMR:2*IMR)

  ! Local static  arrays

  REAL :: DTDX(Jmax), DTDX5(Jmax), acosp(Jmax), &
        cosp(Jmax), cose(Jmax), DAP(kmax),DBK(Kmax)
  data NDT0, NSTEP /0, 0/
  data cross /.TRUE./
  REAL :: DTDY, DTDY5, RCAP
  INTEGER :: JS0, JN0, IML, JMR, IMJM
  SAVE DTDY, DTDY5, RCAP, JS0, JN0, IML, &
        DTDX, DTDX5, ACOSP, COSP, COSE, DAP,DBK

  INTEGER :: NDT0, NSTEP, j2, k,j,i,ic,l,JS,JN,IMH
  INTEGER :: IU,IIU,JT,iad,jad,krd
  REAL :: r23,r3,PI,DL,DP,DT,CR1,MAXDT,ZTC,D5
  REAL :: sum1,sum2,ru

  JMR = JNP -1
  IMJM  = IMR*JNP
  j2 = JNP - j1 + 1
  NSTEP = NSTEP + 1

  ! *********** Initialization **********************
  IF(NSTEP==1) THEN

  WRITE(6,*) '------------------------------------ '
  WRITE(6,*) 'NASA/GSFC Transport Core Version 4.5'
  WRITE(6,*) '------------------------------------ '

  WRITE(6,*) 'IMR=',IMR,' JNP=',JNP,' NLAY=',NLAY,' j1=',j1
  WRITE(6,*) 'NC=',NC,IORD,JORD,KORD,NDT

  ! controles sur les parametres
  IF(NLAY<6) THEN
    WRITE(6,*) 'NLAY must be >= 6'
    stop
  ENDIF
  IF (JNP<NLAY) THEN
     WRITE(6,*) 'JNP must be >= NLAY'
    stop
  ENDIF
  IMRD2=mod(IMR,2)
  IF (j1==2.AND.IMRD2/=0) THEN
     WRITE(6,*) 'if j1=2 IMR must be an even integer'
    stop
  ENDIF


  IF(Jmax<JNP .OR. Kmax<NLAY) THEN
    WRITE(6,*) 'Jmax or Kmax is too small'
    stop
  ENDIF

  DO k=1,NLAY
  DAP(k) = (AP(k+1) - AP(k))*PT
  DBK(k) =  BP(k+1) - BP(k)
  ENDDO

  PI = 4. * ATAN(1.)
  DL = 2.*PI / REAL(IMR)
  DP =    PI / REAL(JMR)

  IF(IGD==0) THEN
  ! Compute analytic cosine at cell edges
        CALL cosa(cosp,cose,JNP,PI,DP)
  else
  ! Define cosine consistent with GEOS-GCM (using dycore2.0 or later)
        CALL cosc(cosp,cose,JNP,PI,DP)
  ENDIF

  DO J=2,JMR
  acosp(j) = 1. / cosp(j)
  END DO

  ! Inverse of the Scaled polar cap area.

  RCAP  = DP / (IMR*(1.-COS((j1-1.5)*DP)))
  acosp(1)   = RCAP
  acosp(JNP) = RCAP
  ENDIF

  IF(NDT0 /= NDT) THEN
  DT   = NDT
  NDT0 = NDT

    IF(Umax < 180.) THEN
     WRITE(6,*) 'Umax may be too small!'
    endif
  CR1  = abs(Umax*DT)/(DL*AE)
  MaxDT = DP*AE / abs(Umax) + 0.5
  WRITE(6,*)'Largest time step for max(V)=',Umax,' is ',MaxDT
  IF(MaxDT < abs(NDT)) THEN
        WRITE(6,*) 'Warning!!! NDT maybe too large!'
  ENDIF

  IF(CR1>=0.95) THEN
  JS0 = 0
  JN0 = 0
  IML = IMR-2
  ZTC = 0.
  else
  ZTC  = acos(CR1) * (180./PI)

  JS0 = REAL(JMR)*(90.-ZTC)/180. + 2
  JS0 = max(JS0, J1+1)
  IML = min(6*JS0/(J1-1)+2, 4*IMR/5)
  JN0 = JNP-JS0+1
  ENDIF


  DO J=2,JMR
  DTDX(j)  = DT / ( DL*AE*COSP(J) )

  ! PRINT*,'dtdx=',dtdx(j)
  DTDX5(j) = 0.5*DTDX(j)
  enddo
  !

  DTDY  = DT /(AE*DP)
   ! PRINT*,'dtdy=',dtdy
  DTDY5 = 0.5*DTDY

  !  WRITE(6,*) 'J1=',J1,' J2=', J2
  ENDIF

  ! *********** End Initialization **********************

  ! delp = pressure thickness: the psudo-density in a hydrostatic system.
  DO  k=1,NLAY
     DO  j=1,JNP
        DO  i=1,IMR
           delp1(i,j,k)=DAP(k)+DBK(k)*PS1(i,j)
           delp2(i,j,k)=DAP(k)+DBK(k)*PS2(i,j)
        enddo
     enddo
  enddo


  IF(j1/=2) THEN
  DO IC=1,NC
  DO L=1,NLAY
  DO I=1,IMR
  Q(I,  2,L,IC) = Q(I,  1,L,IC)
  Q(I,JMR,L,IC) = Q(I,JNP,L,IC)
  END DO
  END DO
  END DO
  ENDIF

  ! Compute "tracer density"
  DO IC=1,NC
  DO k=1,NLAY
  DO j=1,JNP
  DO i=1,IMR
  DQ(i,j,k,IC) = Q(i,j,k,IC)*delp1(i,j,k)
  END DO
  END DO
  END DO
  END DO

  DO k=1,NLAY

  IF(IGD==0) THEN
  ! Convert winds on A-Grid to Courant # on C-Grid.
  CALL A2C(U(1,1,k),V(1,1,k),IMR,JMR,j1,j2,CRX,CRY,dtdx5,DTDY5)
  else
  ! Convert winds on C-grid to Courant #
  DO j=j1,j2
  DO i=2,IMR
  CRX(i,J) = dtdx(j)*U(i-1,j,k)
  END DO
  END DO


  DO j=j1,j2
  CRX(1,J) = dtdx(j)*U(IMR,j,k)
  END DO

  DO i=1,IMR*JMR
  CRY(i,2) = DTDY*V(i,1,k)
  END DO
  ENDIF

  ! Determine JS and JN
  JS = j1
  JN = j2

  DO j=JS0,j1+1,-1
  DO i=1,IMR
  IF(abs(CRX(i,j))>1.) THEN
        JS = j
        go to 2222
  ENDIF
  enddo
  enddo

2222   continue
  DO j=JN0,j2-1
  DO i=1,IMR
  IF(abs(CRX(i,j))>1.) THEN
        JN = j
        go to 2233
  ENDIF
  enddo
  enddo
2233   continue

  IF(j1/=2) then           ! Enlarged polar cap.
  DO i=1,IMR
  DPI(i,  2,k) = 0.
  DPI(i,JMR,k) = 0.
  enddo
  ENDIF

  ! ******* Compute horizontal mass fluxes ************

  ! N-S component
  DO j=j1,j2+1
  D5 = 0.5 * COSE(j)
  DO i=1,IMR
  ymass(i,j) = CRY(i,j)*D5*(delp2(i,j,k) + delp2(i,j-1,k))
  enddo
  enddo

  DO j=j1,j2
  DO i=1,IMR
  DPI(i,j,k) = (ymass(i,j) - ymass(i,j+1)) * acosp(j)
  END DO
  END DO

  ! Poles
  sum1 = ymass(IMR,j1  )
  sum2 = ymass(IMR,J2+1)
  DO i=1,IMR-1
  sum1 = sum1 + ymass(i,j1  )
  sum2 = sum2 + ymass(i,J2+1)
  enddo

  sum1 = - sum1 * RCAP
  sum2 =   sum2 * RCAP
  DO i=1,IMR
  DPI(i,  1,k) = sum1
  DPI(i,JNP,k) = sum2
  enddo

  ! E-W component

  DO j=j1,j2
  DO i=2,IMR
  PU(i,j) = 0.5 * (delp2(i,j,k) + delp2(i-1,j,k))
  enddo
  enddo

  DO j=j1,j2
  PU(1,j) = 0.5 * (delp2(1,j,k) + delp2(IMR,j,k))
  enddo

  DO j=j1,j2
  DO i=1,IMR
  xmass(i,j) = PU(i,j)*CRX(i,j)
  END DO
  END DO

  DO j=j1,j2
  DO i=1,IMR-1
  DPI(i,j,k) = DPI(i,j,k) + xmass(i,j) - xmass(i+1,j)
  END DO
  END DO

  DO j=j1,j2
  DPI(IMR,j,k) = DPI(IMR,j,k) + xmass(IMR,j) - xmass(1,j)
  END DO

  DO j=j1,j2
  DO i=1,IMR-1
  UA(i,j) = 0.5 * (CRX(i,j)+CRX(i+1,j))
  enddo
  enddo

  DO j=j1,j2
  UA(imr,j) = 0.5 * (CRX(imr,j)+CRX(1,j))
  enddo
  !cccccccccccccccccccccccccccccccccccccccccccccccccccccc
  ! Rajouts pour LMDZ.3.3
  !cccccccccccccccccccccccccccccccccccccccccccccccccccccc
  DO i=1,IMR
     DO j=1,JNP
         VA(i,j)=0.
     enddo
  enddo

  DO i=1,imr*(JMR-1)
  VA(i,2) = 0.5*(CRY(i,2)+CRY(i,3))
  enddo

  IF(j1==2) THEN
    IMH = IMR/2
  DO i=1,IMH
  VA(i,      1) = 0.5*(CRY(i,2)-CRY(i+IMH,2))
  VA(i+IMH,  1) = -VA(i,1)
  VA(i,    JNP) = 0.5*(CRY(i,JNP)-CRY(i+IMH,JMR))
  VA(i+IMH,JNP) = -VA(i,JNP)
  enddo
  VA(IMR,1)=VA(1,1)
  VA(IMR,JNP)=VA(1,JNP)
  ENDIF

  ! ****6***0*********0*********0*********0*********0*********0**********72
  DO IC=1,NC

  DO i=1,IMJM
  wk1(i,1,1) = 0.
  wk1(i,1,2) = 0.
  enddo

  ! E-W advective cross term
  DO j=J1,J2
  IF(J>JS  .AND. J<JN) GO TO 250

  DO i=1,IMR
  qtmp(i) = q(i,j,k,IC)
  enddo

  DO i=-IML,0
  qtmp(i)       = q(IMR+i,j,k,IC)
  qtmp(IMR+1-i) = q(1-i,j,k,IC)
  enddo

  DO i=1,IMR
  iu = UA(i,j)
  ru = UA(i,j) - iu
  iiu = i-iu
  IF(UA(i,j)>=0.) THEN
  wk1(i,j,1) = qtmp(iiu)+ru*(qtmp(iiu-1)-qtmp(iiu))
  else
  wk1(i,j,1) = qtmp(iiu)+ru*(qtmp(iiu)-qtmp(iiu+1))
  ENDIF
  wk1(i,j,1) = wk1(i,j,1) - qtmp(i)
  END DO
250   continue
  END DO

  IF(JN/=0) THEN
  DO j=JS+1,JN-1

  DO i=1,IMR
  qtmp(i) = q(i,j,k,IC)
  enddo

  qtmp(0)     = q(IMR,J,k,IC)
  qtmp(IMR+1) = q(  1,J,k,IC)

  DO i=1,imr
  iu = i - UA(i,j)
  wk1(i,j,1) = UA(i,j)*(qtmp(iu) - qtmp(iu+1))
  enddo
  enddo
  ENDIF
  ! ****6***0*********0*********0*********0*********0*********0**********72
  ! Contribution from the N-S advection
  DO i=1,imr*(j2-j1+1)
  JT = REAL(J1) - VA(i,j1)
  wk1(i,j1,2) = VA(i,j1) * (q(i,jt,k,IC) - q(i,jt+1,k,IC))
  enddo

  DO i=1,IMJM
  wk1(i,1,1) = q(i,1,k,IC) + 0.5*wk1(i,1,1)
  wk1(i,1,2) = q(i,1,k,IC) + 0.5*wk1(i,1,2)
  enddo

    IF(cross) THEN
  ! Add cross terms in the vertical direction.
    IF(IORD >= 2) THEN
            iad = 2
    else
            iad = 1
    endif

    IF(JORD >= 2) THEN
            jad = 2
    else
            jad = 1
    endif
  CALL xadv(IMR,JNP,j1,j2,wk1(1,1,2),UA,JS,JN,IML,DC2,iad)
  CALL yadv(IMR,JNP,j1,j2,wk1(1,1,1),VA,PV,W,jad)
  DO j=1,JNP
  DO i=1,IMR
  q(i,j,k,IC) = q(i,j,k,IC) + DC2(i,j) + PV(i,j)
  enddo
  enddo
  ENDIF

  CALL xtp(IMR,JNP,IML,j1,j2,JN,JS,PU,DQ(1,1,k,IC),wk1(1,1,2) &
        ,CRX,fx1,xmass,IORD)

  CALL ytp(IMR,JNP,j1,j2,acosp,RCAP,DQ(1,1,k,IC),wk1(1,1,1),CRY, &
        DC2,ymass,WK1(1,1,3),wk1(1,1,4),WK1(1,1,5),WK1(1,1,6),JORD)

  END DO
  END DO

  ! ******* Compute vertical mass flux (same unit as PS) ***********

  ! 1st step: compute total column mass CONVERGENCE.

  DO j=1,JNP
  DO i=1,IMR
  CRY(i,j) = DPI(i,j,1)
  END DO
  END DO

  DO k=2,NLAY
  DO j=1,JNP
  DO i=1,IMR
  CRY(i,j)  = CRY(i,j) + DPI(i,j,k)
  END DO
  END DO
  END DO

  DO j=1,JNP
  DO i=1,IMR

  ! 2nd step: compute PS2 (PS at n+1) using the hydrostatic assumption.
  ! Changes (increases) to surface pressure = total column mass convergence

  PS2(i,j)  = PS1(i,j) + CRY(i,j)

  ! 3rd step: compute vertical mass flux from mass conservation principle.

  W(i,j,1) = DPI(i,j,1) - DBK(1)*CRY(i,j)
  W(i,j,NLAY) = 0.
  END DO
  END DO

  DO k=2,NLAY-1
  DO j=1,JNP
  DO i=1,IMR
  W(i,j,k) = W(i,j,k-1) + DPI(i,j,k) - DBK(k)*CRY(i,j)
  END DO
  END DO
  END DO

  DO k=1,NLAY
  DO j=1,JNP
  DO i=1,IMR
  delp2(i,j,k) = DAP(k) + DBK(k)*PS2(i,j)
  END DO
  END DO
  END DO

    KRD = max(3, KORD)
  DO IC=1,NC

  !****6***0*********0*********0*********0*********0*********0**********72

  CALL FZPPM(IMR,JNP,NLAY,j1,DQ(1,1,1,IC),W,Q(1,1,1,IC),WK1,DPI, &
        DC2,CRX,CRY,PU,PV,xmass,ymass,delp1,KRD)
  !

  IF(fill) CALL qckxyz(DQ(1,1,1,IC),DC2,IMR,JNP,NLAY,j1,j2, &
        cosp,acosp,.FALSE.,IC,NSTEP)

  ! Recover tracer mixing ratio from "density" using predicted
  ! "air density" (pressure thickness) at time-level n+1

  DO k=1,NLAY
  DO j=1,JNP
  DO i=1,IMR
        Q(i,j,k,IC) = DQ(i,j,k,IC) / delp2(i,j,k)
         ! PRINT*,'i=',i,'j=',j,'k=',k,'Q(i,j,k,IC)=',Q(i,j,k,IC)
  enddo
  enddo
  enddo

  IF(j1/=2) THEN
  DO k=1,NLAY
  DO I=1,IMR
  ! j=1 c'est le pôle Sud, j=JNP c'est le pôle Nord
  Q(I,  2,k,IC) = Q(I,  1,k,IC)
  Q(I,JMR,k,IC) = Q(I,JNP,k,IC)
  END DO
  END DO
  ENDIF
  END DO

  IF(j1/=2) THEN
  DO k=1,NLAY
  DO i=1,IMR
  W(i,  2,k) = W(i,  1,k)
  W(i,JMR,k) = W(i,JNP,k)
  END DO
  END DO
  ENDIF

  RETURN
END SUBROUTINE ppm3d

!****6***0*********0*********0*********0*********0*********0**********72
SUBROUTINE FZPPM(IMR,JNP,NLAY,j1,DQ,WZ,P,DC,DQDT,AR,AL,A6, &
        flux,wk1,wk2,wz2,delp,KORD)
  IMPLICIT NONE
  INTEGER,parameter :: kmax = 150
  REAL,parameter :: R23 = 2./3., R3 = 1./3.
  INTEGER :: IMR,JNP,NLAY,J1,KORD
  REAL :: WZ(IMR,JNP,NLAY),P(IMR,JNP,NLAY),DC(IMR,JNP,NLAY), &
        wk1(IMR,*),delp(IMR,JNP,NLAY),DQ(IMR,JNP,NLAY), &
        DQDT(IMR,JNP,NLAY)
  ! Assuming JNP >= NLAY
  REAL :: AR(IMR,*),AL(IMR,*),A6(IMR,*),flux(IMR,*),wk2(IMR,*), &
        wz2(IMR,*)
  INTEGER :: JMR,IMJM,NLAYM1,LMT,K,I,J
  REAL :: c0,c1,c2,tmp,qmax,qmin,a,b,fct,a1,a2,cm,cp

  JMR = JNP - 1
  IMJM = IMR*JNP
  NLAYM1 = NLAY - 1

  LMT = KORD - 3

  ! ****6***0*********0*********0*********0*********0*********0**********72
  ! Compute DC for PPM
  ! ****6***0*********0*********0*********0*********0*********0**********72

  DO k=1,NLAYM1
  DO i=1,IMJM
  DQDT(i,1,k) = P(i,1,k+1) - P(i,1,k)
  END DO
  END DO

  DO k=2,NLAYM1
  DO I=1,IMJM
   c0 =  delp(i,1,k) / (delp(i,1,k-1)+delp(i,1,k)+delp(i,1,k+1))
   c1 = (delp(i,1,k-1)+0.5*delp(i,1,k))/(delp(i,1,k+1)+delp(i,1,k))
   c2 = (delp(i,1,k+1)+0.5*delp(i,1,k))/(delp(i,1,k-1)+delp(i,1,k))
  tmp = c0*(c1*DQDT(i,1,k) + c2*DQDT(i,1,k-1))
  Qmax = max(P(i,1,k-1),P(i,1,k),P(i,1,k+1)) - P(i,1,k)
  Qmin = P(i,1,k) - min(P(i,1,k-1),P(i,1,k),P(i,1,k+1))
  DC(i,1,k) = sign(min(abs(tmp),Qmax,Qmin), tmp)
  END DO
  END DO


  ! ****6***0*********0*********0*********0*********0*********0**********72
  ! Loop over latitudes  (to save memory)
  ! ****6***0*********0*********0*********0*********0*********0**********72

  DO j=1,JNP
  IF((j==2 .OR. j==JMR) .AND. j1/=2) goto 2000

  DO k=1,NLAY
  DO i=1,IMR
  wz2(i,k) =   WZ(i,j,k)
  wk1(i,k) =    P(i,j,k)
  wk2(i,k) = delp(i,j,k)
  flux(i,k) = DC(i,j,k)  !this flux is actually the monotone slope
  enddo
  enddo

  !****6***0*********0*********0*********0*********0*********0**********72
  ! Compute first guesses at cell interfaces
  ! First guesses are required to be continuous.
  ! ****6***0*********0*********0*********0*********0*********0**********72

  ! three-cell parabolic subgrid distribution at model top
  ! two-cell parabolic with zero gradient subgrid distribution
  ! at the surface.

  ! First guess top edge value
  DO i=1,IMR
  ! three-cell PPM
  ! Compute a,b, and c of q = aP**2 + bP + c using cell averages and delp
  a = 3.*( DQDT(i,j,2) - DQDT(i,j,1)*(wk2(i,2)+wk2(i,3))/ &
        (wk2(i,1)+wk2(i,2)) ) / &
        ( (wk2(i,2)+wk2(i,3))*(wk2(i,1)+wk2(i,2)+wk2(i,3)) )
  b = 2.*DQDT(i,j,1)/(wk2(i,1)+wk2(i,2)) - &
        R23*a*(2.*wk2(i,1)+wk2(i,2))
  AL(i,1) =  wk1(i,1) - wk2(i,1)*(R3*a*wk2(i,1) + 0.5*b)
  AL(i,2) =  wk2(i,1)*(a*wk2(i,1) + b) + AL(i,1)

  ! Check if change sign
  IF(wk1(i,1)*AL(i,1)<=0.) THEN
             AL(i,1) = 0.
         flux(i,1) = 0.
    else
         flux(i,1) =  wk1(i,1) - AL(i,1)
    endif
  END DO

  ! Bottom
  DO i=1,IMR
  ! 2-cell PPM with zero gradient right at the surface

  fct = DQDT(i,j,NLAYM1)*wk2(i,NLAY)**2 / &
        ( (wk2(i,NLAY)+wk2(i,NLAYM1))*(2.*wk2(i,NLAY)+wk2(i,NLAYM1)))
  AR(i,NLAY) = wk1(i,NLAY) + fct
  AL(i,NLAY) = wk1(i,NLAY) - (fct+fct)
  IF(wk1(i,NLAY)*AR(i,NLAY)<=0.) AR(i,NLAY) = 0.
  flux(i,NLAY) = AR(i,NLAY) -  wk1(i,NLAY)
  END DO


  !****6***0*********0*********0*********0*********0*********0**********72
  ! 4th order interpolation in the interior.
  !****6***0*********0*********0*********0*********0*********0**********72

  DO k=3,NLAYM1
  DO i=1,IMR
  c1 =  DQDT(i,j,k-1)*wk2(i,k-1) / (wk2(i,k-1)+wk2(i,k))
  c2 =  2. / (wk2(i,k-2)+wk2(i,k-1)+wk2(i,k)+wk2(i,k+1))
  A1   =  (wk2(i,k-2)+wk2(i,k-1)) / (2.*wk2(i,k-1)+wk2(i,k))
  A2   =  (wk2(i,k  )+wk2(i,k+1)) / (2.*wk2(i,k)+wk2(i,k-1))
  AL(i,k) = wk1(i,k-1) + c1 + c2 * &
        ( wk2(i,k  )*(c1*(A1 - A2)+A2*flux(i,k-1)) - &
        wk2(i,k-1)*A1*flux(i,k)  )
   ! PRINT *,'AL1',i,k, AL(i,k)
  END DO
  END DO

  DO i=1,IMR*NLAYM1
  AR(i,1) = AL(i,2)
   ! PRINT *,'AR1',i,AR(i,1)
  END DO

  DO i=1,IMR*NLAY
  A6(i,1) = 3.*(wk1(i,1)+wk1(i,1) - (AL(i,1)+AR(i,1)))
   ! PRINT *,'A61',i,A6(i,1)
  END DO

  !****6***0*********0*********0*********0*********0*********0**********72
  ! Top & Bot always monotonic
  CALL lmtppm(flux(1,1),A6(1,1),AR(1,1),AL(1,1),wk1(1,1),IMR,0)
  CALL lmtppm(flux(1,NLAY),A6(1,NLAY),AR(1,NLAY),AL(1,NLAY), &
        wk1(1,NLAY),IMR,0)

  ! Interior depending on KORD
  IF(LMT<=2) &
        CALL lmtppm(flux(1,2),A6(1,2),AR(1,2),AL(1,2),wk1(1,2), &
        IMR*(NLAY-2),LMT)

  !****6***0*********0*********0*********0*********0*********0**********72

  DO i=1,IMR*NLAYM1
  IF(wz2(i,1)>0.) THEN
    CM = wz2(i,1) / wk2(i,1)
    flux(i,2) = AR(i,1)+0.5*CM*(AL(i,1)-AR(i,1)+A6(i,1)*(1.-R23*CM))
  else
     ! PRINT *,'test2-0',i,j,wz2(i,1),wk2(i,2)
    CP= wz2(i,1) / wk2(i,2)
     ! PRINT *,'testCP',CP
    flux(i,2) = AL(i,2)+0.5*CP*(AL(i,2)-AR(i,2)-A6(i,2)*(1.+R23*CP))
     ! PRINT *,'test2',i, AL(i,2),AR(i,2),A6(i,2),R23
  ENDIF
  END DO

  DO i=1,IMR*NLAYM1
  flux(i,2) = wz2(i,1) * flux(i,2)
  END DO

  DO i=1,IMR
  DQ(i,j,   1) = DQ(i,j,   1) - flux(i,   2)
  DQ(i,j,NLAY) = DQ(i,j,NLAY) + flux(i,NLAY)
  END DO

  DO k=2,NLAYM1
  DO i=1,IMR
  DQ(i,j,k) = DQ(i,j,k) + flux(i,k) - flux(i,k+1)
  END DO
  END DO
2000   continue
  END DO
  RETURN
END SUBROUTINE fzppm

SUBROUTINE xtp(IMR,JNP,IML,j1,j2,JN,JS,PU,DQ,Q,UC, &
        fx1,xmass,IORD)
  IMPLICIT NONE
  INTEGER :: IMR,JNP,IML,j1,j2,JN,JS,IORD
  REAL :: PU,DQ,Q,UC,fx1,xmass
  REAL :: dc,qtmp
  INTEGER :: ISAVE(IMR)
  dimension UC(IMR,*),DC(-IML:IMR+IML+1),xmass(IMR,JNP) &
        ,fx1(IMR+1),DQ(IMR,JNP),qtmp(-IML:IMR+1+IML)
  dimension PU(IMR,JNP),Q(IMR,JNP)
  INTEGER :: jvan,j1vl,j2vl,j,i,iu,itmp,ist,imp
  REAL :: rut

  IMP = IMR + 1

  ! van Leer at high latitudes
  jvan = max(1,JNP/18)
  j1vl = j1+jvan
  j2vl = j2-jvan

  DO j=j1,j2

  DO i=1,IMR
  qtmp(i) = q(i,j)
  enddo

  IF(j>=JN .OR. j<=JS) goto 2222
  ! ************* Eulerian **********

  qtmp(0)     = q(IMR,J)
  qtmp(-1)    = q(IMR-1,J)
  qtmp(IMP)   = q(1,J)
  qtmp(IMP+1) = q(2,J)

  IF(IORD==1 .OR. j==j1 .OR. j==j2) THEN
  DO i=1,IMR
  iu = REAL(i) - uc(i,j)
  fx1(i) = qtmp(iu)
  END DO
  ELSE
  CALL xmist(IMR,IML,Qtmp,DC)
  DC(0) = DC(IMR)

  IF(IORD==2 .OR. j<=j1vl .OR. j>=j2vl) THEN
  DO i=1,IMR
  iu = REAL(i) - uc(i,j)
  fx1(i) = qtmp(iu) + DC(iu)*(sign(1.,uc(i,j))-uc(i,j))
  END DO
  else
  CALL fxppm(IMR,IML,UC(1,j),Qtmp,DC,fx1,IORD)
  ENDIF

  ENDIF

  DO i=1,IMR
  fx1(i) = fx1(i)*xmass(i,j)
  END DO

  goto 1309

  ! ***** Conservative (flux-form) Semi-Lagrangian transport *****

2222   continue

  DO i=-IML,0
  qtmp(i)     = q(IMR+i,j)
  qtmp(IMP-i) = q(1-i,j)
  enddo

  IF(IORD==1 .OR. j==j1 .OR. j==j2) THEN
  DO i=1,IMR
  itmp = INT(uc(i,j))
  ISAVE(i) = i - itmp
  iu = i - uc(i,j)
  fx1(i) = (uc(i,j) - itmp)*qtmp(iu)
  END DO
  ELSE
  CALL xmist(IMR,IML,Qtmp,DC)

  DO i=-IML,0
  DC(i)     = DC(IMR+i)
  DC(IMP-i) = DC(1-i)
  enddo

  DO i=1,IMR
  itmp = INT(uc(i,j))
  rut  = uc(i,j) - itmp
  ISAVE(i) = i - itmp
  iu = i - uc(i,j)
  fx1(i) = rut*(qtmp(iu) + DC(iu)*(sign(1.,rut) - rut))
  END DO
  ENDIF

  DO i=1,IMR
  IF(uc(i,j)>1.) THEN
  !DIR$ NOVECTOR
    DO ist = ISAVE(i),i-1
    fx1(i) = fx1(i) + qtmp(ist)
    enddo
  elseIF(uc(i,j)<-1.) THEN
    DO ist = i,ISAVE(i)-1
    fx1(i) = fx1(i) - qtmp(ist)
    enddo
  !DIR$ VECTOR
  ENDIF
  END DO
  DO i=1,IMR
  fx1(i) = PU(i,j)*fx1(i)
  enddo

  ! ***************************************

1309   fx1(IMP) = fx1(1)
  DO i=1,IMR
  DQ(i,j) =  DQ(i,j) + fx1(i)-fx1(i+1)
  END DO

  ! ***************************************

  END DO
  RETURN
END SUBROUTINE xtp

SUBROUTINE fxppm(IMR,IML,UT,P,DC,flux,IORD)
  IMPLICIT NONE
  INTEGER :: IMR,IML,IORD
  REAL :: UT,P,DC,flux
  REAL,parameter ::  R3 = 1./3., R23 = 2./3.
  DIMENSION UT(*),flux(*),P(-IML:IMR+IML+1),DC(-IML:IMR+IML+1)
  REAL :: AR(0:IMR),AL(0:IMR),A6(0:IMR)
  INTEGER :: LMT,IMP,JLVL,i
   ! LOGICAL first
   ! data first /.TRUE./
   ! SAVE LMT
   ! IF(first) THEN

  ! correction calcul de LMT a chaque passage pour pouvoir choisir
  ! plusieurs schemas PPM pour differents traceurs
  !  IF (IORD.LE.0) THEN
  !        IF(IMR.GE.144) THEN
  !              LMT = 0
  !        elseif(IMR.GE.72) THEN
  !              LMT = 1
  !        else
  !              LMT = 2
  !        endif
  !  else
  !        LMT = IORD - 3
  !  ENDIF

  LMT = IORD - 3
   ! WRITE(6,*) 'PPM option in E-W direction = ', LMT
   ! first = .FALSE.
   ! END IF

  DO i=1,IMR
  AL(i) = 0.5*(p(i-1)+p(i)) + (DC(i-1) - DC(i))*R3
  END DO

  DO i=1,IMR-1
  AR(i) = AL(i+1)
  END DO
  AR(IMR) = AL(1)

  DO i=1,IMR
  A6(i) = 3.*(p(i)+p(i)  - (AL(i)+AR(i)))
  END DO

  IF(LMT<=2) CALL lmtppm(DC(1),A6(1),AR(1),AL(1),P(1),IMR,LMT)

  AL(0) = AL(IMR)
  AR(0) = AR(IMR)
  A6(0) = A6(IMR)

  DO i=1,IMR
  IF(UT(i)>0.) THEN
  flux(i) = AR(i-1) + 0.5*UT(i)*(AL(i-1) - AR(i-1) + &
        A6(i-1)*(1.-R23*UT(i)) )
  else
  flux(i) = AL(i) - 0.5*UT(i)*(AR(i) - AL(i) + &
        A6(i)*(1.+R23*UT(i)))
  ENDIF
  enddo
  RETURN
END SUBROUTINE fxppm

SUBROUTINE xmist(IMR,IML,P,DC)
  IMPLICIT NONE
  INTEGER :: IMR,IML
  REAL,parameter :: R24 = 1./24.
  REAL :: P(-IML:IMR+1+IML),DC(-IML:IMR+1+IML)
  INTEGER :: i
  REAL :: tmp,pmax,pmin

  DO i=1,IMR
  tmp = R24*(8.*(p(i+1) - p(i-1)) + p(i-2) - p(i+2))
  Pmax = max(P(i-1), p(i), p(i+1)) - p(i)
  Pmin = p(i) - min(P(i-1), p(i), p(i+1))
  DC(i) = sign(min(abs(tmp),Pmax,Pmin), tmp)
  END DO
  RETURN
END SUBROUTINE xmist

SUBROUTINE ytp(IMR,JNP,j1,j2,acosp,RCAP,DQ,P,VC,DC2 &
        ,ymass,fx,A6,AR,AL,JORD)
  IMPLICIT NONE
  INTEGER :: IMR,JNP,j1,j2,JORD
  REAL :: acosp,RCAP,DQ,P,VC,DC2,ymass,fx,A6,AR,AL
  dimension P(IMR,JNP),VC(IMR,JNP),ymass(IMR,JNP) &
        ,DC2(IMR,JNP),DQ(IMR,JNP),acosp(JNP)
  ! Work array
  DIMENSION fx(IMR,JNP),AR(IMR,JNP),AL(IMR,JNP),A6(IMR,JNP)
  INTEGER :: JMR,len,i,jt,j
  REAL :: sum1,sum2

  JMR = JNP - 1
  len = IMR*(J2-J1+2)

  IF(JORD==1) THEN
  DO i=1,len
  JT = REAL(J1) - VC(i,J1)
  fx(i,j1) = p(i,JT)
  END DO
  else

  CALL ymist(IMR,JNP,j1,P,DC2,4)

  IF(JORD<=0 .OR. JORD>=3) THEN
  CALL fyppm(VC,P,DC2,fx,IMR,JNP,j1,j2,A6,AR,AL,JORD)

  else
  DO i=1,len
  JT = REAL(J1) - VC(i,J1)
  fx(i,j1) = p(i,JT) + (sign(1.,VC(i,j1))-VC(i,j1))*DC2(i,JT)
  END DO
  ENDIF
  ENDIF

  DO i=1,len
  fx(i,j1) = fx(i,j1)*ymass(i,j1)
  END DO

  DO j=j1,j2
  DO i=1,IMR
  DQ(i,j) = DQ(i,j) + (fx(i,j) - fx(i,j+1)) * acosp(j)
  END DO
  END DO

  ! Poles
  sum1 = fx(IMR,j1  )
  sum2 = fx(IMR,J2+1)
  DO i=1,IMR-1
  sum1 = sum1 + fx(i,j1  )
  sum2 = sum2 + fx(i,J2+1)
  enddo

  sum1 = DQ(1,  1) - sum1 * RCAP
  sum2 = DQ(1,JNP) + sum2 * RCAP
  DO i=1,IMR
  DQ(i,  1) = sum1
  DQ(i,JNP) = sum2
  enddo

  IF(j1/=2) THEN
  DO i=1,IMR
  DQ(i,  2) = sum1
  DQ(i,JMR) = sum2
  enddo
  ENDIF

  RETURN
END SUBROUTINE ytp

subroutine  ymist(IMR,JNP,j1,P,DC,ID)
  IMPLICIT NONE
  INTEGER :: IMR,JNP,j1,ID
  REAL,parameter :: R24 = 1./24.
  REAL :: P(IMR,JNP),DC(IMR,JNP)
  INTEGER :: iimh,jmr,ijm3,imh,i
  REAL :: pmax,pmin,tmp

  IMH = IMR / 2
  JMR = JNP - 1
  IJM3 = IMR*(JMR-3)

  IF(ID==2) THEN
  DO i=1,IMR*(JMR-1)
  tmp = 0.25*(p(i,3) - p(i,1))
  Pmax = max(p(i,1),p(i,2),p(i,3)) - p(i,2)
  Pmin = p(i,2) - min(p(i,1),p(i,2),p(i,3))
  DC(i,2) = sign(min(abs(tmp),Pmin,Pmax),tmp)
  END DO
  ELSE
  DO i=1,IMH
  ! J=2
  tmp = (8.*(p(i,3) - p(i,1)) + p(i+IMH,2) - p(i,4))*R24
  Pmax = max(p(i,1),p(i,2),p(i,3)) - p(i,2)
  Pmin = p(i,2) - min(p(i,1),p(i,2),p(i,3))
  DC(i,2) = sign(min(abs(tmp),Pmin,Pmax),tmp)
  ! J=JMR
  tmp=(8.*(p(i,JNP)-p(i,JMR-1))+p(i,JMR-2)-p(i+IMH,JMR))*R24
  Pmax = max(p(i,JMR-1),p(i,JMR),p(i,JNP)) - p(i,JMR)
  Pmin = p(i,JMR) - min(p(i,JMR-1),p(i,JMR),p(i,JNP))
  DC(i,JMR) = sign(min(abs(tmp),Pmin,Pmax),tmp)
  END DO
  DO i=IMH+1,IMR
  ! J=2
  tmp = (8.*(p(i,3) - p(i,1)) + p(i-IMH,2) - p(i,4))*R24
  Pmax = max(p(i,1),p(i,2),p(i,3)) - p(i,2)
  Pmin = p(i,2) - min(p(i,1),p(i,2),p(i,3))
  DC(i,2) = sign(min(abs(tmp),Pmin,Pmax),tmp)
  ! J=JMR
  tmp=(8.*(p(i,JNP)-p(i,JMR-1))+p(i,JMR-2)-p(i-IMH,JMR))*R24
  Pmax = max(p(i,JMR-1),p(i,JMR),p(i,JNP)) - p(i,JMR)
  Pmin = p(i,JMR) - min(p(i,JMR-1),p(i,JMR),p(i,JNP))
  DC(i,JMR) = sign(min(abs(tmp),Pmin,Pmax),tmp)
  END DO

  DO i=1,IJM3
  tmp = (8.*(p(i,4) - p(i,2)) + p(i,1) - p(i,5))*R24
  Pmax = max(p(i,2),p(i,3),p(i,4)) - p(i,3)
  Pmin = p(i,3) - min(p(i,2),p(i,3),p(i,4))
  DC(i,3) = sign(min(abs(tmp),Pmin,Pmax),tmp)
  END DO
  ENDIF

  IF(j1/=2) THEN
  DO i=1,IMR
  DC(i,1) = 0.
  DC(i,JNP) = 0.
  enddo
  else
  ! Determine slopes in polar caps for scalars!

  DO i=1,IMH
  ! South
  tmp = 0.25*(p(i,2) - p(i+imh,2))
  Pmax = max(p(i,2),p(i,1), p(i+imh,2)) - p(i,1)
  Pmin = p(i,1) - min(p(i,2),p(i,1), p(i+imh,2))
  DC(i,1)=sign(min(abs(tmp),Pmax,Pmin),tmp)
  ! North.
  tmp = 0.25*(p(i+imh,JMR) - p(i,JMR))
  Pmax = max(p(i+imh,JMR),p(i,jnp), p(i,JMR)) - p(i,JNP)
  Pmin = p(i,JNP) - min(p(i+imh,JMR),p(i,jnp), p(i,JMR))
  DC(i,JNP) = sign(min(abs(tmp),Pmax,pmin),tmp)
  END DO

  DO i=imh+1,IMR
  DC(i,  1) =  - DC(i-imh,  1)
  DC(i,JNP) =  - DC(i-imh,JNP)
  END DO
  ENDIF
  RETURN
END SUBROUTINE ymist

SUBROUTINE fyppm(VC,P,DC,flux,IMR,JNP,j1,j2,A6,AR,AL,JORD)
  IMPLICIT NONE
  INTEGER :: IMR,JNP,j1,j2,JORD
  REAL,parameter :: R3 = 1./3., R23 = 2./3.
  REAL :: VC(IMR,*),flux(IMR,*),P(IMR,*),DC(IMR,*)
  ! Local work arrays.
  REAL :: AR(IMR,JNP),AL(IMR,JNP),A6(IMR,JNP)
  INTEGER :: LMT,i
  INTEGER :: IMH,JMR,j11,IMJM1,len
   ! LOGICAL first
   ! data first /.TRUE./
   ! SAVE LMT

  IMH = IMR / 2
  JMR = JNP - 1
  j11 = j1-1
  IMJM1 = IMR*(J2-J1+2)
  len   = IMR*(J2-J1+3)
   ! IF(first) THEN
   ! IF(JORD.LE.0) THEN
   !       IF(JMR.GE.90) THEN
   !             LMT = 0
   !       elseif(JMR.GE.45) THEN
   !             LMT = 1
   !       else
   !             LMT = 2
   !       endif
   ! else
   !       LMT = JORD - 3
   ! END IF

  !  first = .FALSE.
  !  ENDIF

  ! modifs pour pouvoir choisir plusieurs schemas PPM
  LMT = JORD - 3

  DO i=1,IMR*JMR
  AL(i,2) = 0.5*(p(i,1)+p(i,2)) + (DC(i,1) - DC(i,2))*R3
  AR(i,1) = AL(i,2)
  END DO

  !Poles:

  DO i=1,IMH
  AL(i,1) = AL(i+IMH,2)
  AL(i+IMH,1) = AL(i,2)

  AR(i,JNP) = AR(i+IMH,JMR)
  AR(i+IMH,JNP) = AR(i,JMR)
  ENDDO

  !cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
  !   Rajout pour LMDZ.3.3
  !ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
  AR(IMR,1)=AL(1,1)
  AR(IMR,JNP)=AL(1,JNP)
  !cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc


  DO i=1,len
  A6(i,j11) = 3.*(p(i,j11)+p(i,j11)  - (AL(i,j11)+AR(i,j11)))
  END DO

  IF(LMT<=2) CALL lmtppm(DC(1,j11),A6(1,j11),AR(1,j11) &
        ,AL(1,j11),P(1,j11),len,LMT)
  !

  DO i=1,IMJM1
  IF(VC(i,j1)>0.) THEN
  flux(i,j1) = AR(i,j11) + 0.5*VC(i,j1)*(AL(i,j11) - AR(i,j11) + &
        A6(i,j11)*(1.-R23*VC(i,j1)) )
  else
  flux(i,j1) = AL(i,j1) - 0.5*VC(i,j1)*(AR(i,j1) - AL(i,j1) + &
        A6(i,j1)*(1.+R23*VC(i,j1)))
  ENDIF
  END DO
  RETURN
END SUBROUTINE fyppm

  SUBROUTINE yadv(IMR,JNP,j1,j2,p,VA,ady,wk,IAD)
    IMPLICIT NONE
    INTEGER :: IMR,JNP,j1,j2,IAD
    REAL :: p(IMR,JNP),ady(IMR,JNP),VA(IMR,JNP)
    REAL :: WK(IMR,-1:JNP+2)
    INTEGER :: JMR,IMH,i,j,jp
    REAL :: rv,a1,b1,sum1,sum2

    JMR = JNP-1
    IMH = IMR/2
    DO j=1,JNP
    DO i=1,IMR
    wk(i,j) = p(i,j)
    enddo
    enddo
  ! Poles:
    DO i=1,IMH
    wk(i,   -1) = p(i+IMH,3)
    wk(i+IMH,-1) = p(i,3)
    wk(i,    0) = p(i+IMH,2)
    wk(i+IMH,0) = p(i,2)
    wk(i,JNP+1) = p(i+IMH,JMR)
    wk(i+IMH,JNP+1) = p(i,JMR)
    wk(i,JNP+2) = p(i+IMH,JNP-2)
    wk(i+IMH,JNP+2) = p(i,JNP-2)
    enddo
     ! WRITE(*,*) 'toto 1'
  ! --------------------------------
  IF(IAD==2) THEN
  DO j=j1-1,j2+1
  DO i=1,IMR
   ! WRITE(*,*) 'avt NINT','i=',i,'j=',j
  JP = NINT(VA(i,j))
  rv = JP - VA(i,j)
   ! WRITE(*,*) 'VA=',VA(i,j), 'JP1=',JP,'rv=',rv
  JP = j - JP
   ! WRITE(*,*) 'JP2=',JP
  a1 = 0.5*(wk(i,jp+1)+wk(i,jp-1)) - wk(i,jp)
  b1 = 0.5*(wk(i,jp+1)-wk(i,jp-1))
   ! WRITE(*,*) 'a1=',a1,'b1=',b1
  ady(i,j) = wk(i,jp) + rv*(a1*rv + b1) - wk(i,j)
  enddo
  enddo
   ! WRITE(*,*) 'toto 2'

  ELSEIF(IAD==1) THEN
    DO j=j1-1,j2+1
  DO i=1,imr
  JP = REAL(j)-VA(i,j)
  ady(i,j) = VA(i,j)*(wk(i,jp)-wk(i,jp+1))
  enddo
  enddo
  ENDIF

    IF(j1/=2) THEN
    sum1 = 0.
    sum2 = 0.
  DO i=1,imr
  sum1 = sum1 + ady(i,2)
  sum2 = sum2 + ady(i,JMR)
  enddo
    sum1 = sum1 / IMR
    sum2 = sum2 / IMR

  DO i=1,imr
  ady(i,  2) =  sum1
  ady(i,JMR) =  sum2
  ady(i,  1) =  sum1
  ady(i,JNP) =  sum2
  enddo
    else
  ! Poles:
    sum1 = 0.
    sum2 = 0.
  DO i=1,imr
  sum1 = sum1 + ady(i,1)
  sum2 = sum2 + ady(i,JNP)
  enddo
    sum1 = sum1 / IMR
    sum2 = sum2 / IMR

  DO i=1,imr
  ady(i,  1) =  sum1
  ady(i,JNP) =  sum2
  enddo
    endif

    RETURN
END SUBROUTINE yadv

  SUBROUTINE xadv(IMR,JNP,j1,j2,p,UA,JS,JN,IML,adx,IAD)
    IMPLICIT NONE
    INTEGER :: IMR,JNP,j1,j2,JS,JN,IML,IAD
    REAL :: p(IMR,JNP),adx(IMR,JNP),qtmp(-IMR:IMR+IMR),UA(IMR,JNP)
    INTEGER :: JMR,j,i,ip,iu,iiu
    REAL :: ru,a1,b1

    JMR = JNP-1
  DO j=j1,j2
  IF(J>JS  .AND. J<JN) GO TO 1309

  DO i=1,IMR
  qtmp(i) = p(i,j)
  enddo

  DO i=-IML,0
  qtmp(i)       = p(IMR+i,j)
  qtmp(IMR+1-i) = p(1-i,j)
  enddo

  IF(IAD==2) THEN
  DO i=1,IMR
  IP = NINT(UA(i,j))
  ru = IP - UA(i,j)
  IP = i - IP
  a1 = 0.5*(qtmp(ip+1)+qtmp(ip-1)) - qtmp(ip)
  b1 = 0.5*(qtmp(ip+1)-qtmp(ip-1))
  adx(i,j) = qtmp(ip) + ru*(a1*ru + b1)
  enddo
  ELSEIF(IAD==1) THEN
  DO i=1,IMR
  iu = UA(i,j)
  ru = UA(i,j) - iu
  iiu = i-iu
  IF(UA(i,j)>=0.) THEN
  adx(i,j) = qtmp(iiu)+ru*(qtmp(iiu-1)-qtmp(iiu))
  else
  adx(i,j) = qtmp(iiu)+ru*(qtmp(iiu)-qtmp(iiu+1))
  ENDIF
  enddo
  ENDIF

  DO i=1,IMR
  adx(i,j) = adx(i,j) - p(i,j)
  enddo
1309   continue
  END DO

  ! Eulerian upwind

  DO j=JS+1,JN-1

  DO i=1,IMR
  qtmp(i) = p(i,j)
  enddo

  qtmp(0)     = p(IMR,J)
  qtmp(IMR+1) = p(1,J)

  IF(IAD==2) THEN
  qtmp(-1)     = p(IMR-1,J)
  qtmp(IMR+2) = p(2,J)
  DO i=1,imr
  IP = NINT(UA(i,j))
  ru = IP - UA(i,j)
  IP = i - IP
  a1 = 0.5*(qtmp(ip+1)+qtmp(ip-1)) - qtmp(ip)
  b1 = 0.5*(qtmp(ip+1)-qtmp(ip-1))
  adx(i,j) = qtmp(ip)- p(i,j) + ru*(a1*ru + b1)
  enddo
  ELSEIF(IAD==1) THEN
  ! 1st order
  DO i=1,IMR
  IP = i - UA(i,j)
  adx(i,j) = UA(i,j)*(qtmp(ip)-qtmp(ip+1))
  enddo
  ENDIF
  enddo

    IF(j1/=2) THEN
  DO i=1,IMR
  adx(i,  2) = 0.
  adx(i,JMR) = 0.
  enddo
    endif
  ! set cross term due to x-adv at the poles to zero.
  DO i=1,IMR
  adx(i,  1) = 0.
  adx(i,JNP) = 0.
  enddo
    RETURN
END SUBROUTINE xadv

SUBROUTINE lmtppm(DC,A6,AR,AL,P,IM,LMT)
  IMPLICIT NONE

  ! A6 =  CURVATURE OF THE TEST PARABOLA
  ! AR =  RIGHT EDGE VALUE OF THE TEST PARABOLA
  ! AL =  LEFT  EDGE VALUE OF THE TEST PARABOLA
  ! DC =  0.5 * MISMATCH
  ! P  =  CELL-AVERAGED VALUE
  ! IM =  VECTOR LENGTH

  ! OPTIONS:

  ! LMT = 0: FULL MONOTONICITY
  ! LMT = 1: SEMI-MONOTONIC CONSTRAINT (NO UNDERSHOOTS)
  ! LMT = 2: POSITIVE-DEFINITE CONSTRAINT

  REAL,parameter :: R12 = 1./12.
  REAL :: A6(IM),AR(IM),AL(IM),P(IM),DC(IM)
  INTEGER :: IM,LMT
  INTEGER :: i
  REAL :: da1,da2,a6da,fmin

  IF(LMT==0) THEN
  ! Full constraint
  DO i=1,IM
  IF(DC(i)==0.) THEN
        AR(i) = p(i)
        AL(i) = p(i)
        A6(i) = 0.
  else
  da1  = AR(i) - AL(i)
  da2  = da1**2
  A6DA = A6(i)*da1
  IF(A6DA < -da2) THEN
        A6(i) = 3.*(AL(i)-p(i))
        AR(i) = AL(i) - A6(i)
  elseif(A6DA > da2) THEN
        A6(i) = 3.*(AR(i)-p(i))
        AL(i) = AR(i) - A6(i)
  ENDIF
  ENDIF
  END DO
  elseif(LMT==1) THEN
  ! Semi-monotonic constraint
  DO i=1,IM
  IF(abs(AR(i)-AL(i)) >= -A6(i)) go to 150
  IF(p(i)<AR(i) .AND. p(i)<AL(i)) THEN
        AR(i) = p(i)
        AL(i) = p(i)
        A6(i) = 0.
  elseif(AR(i) > AL(i)) THEN
        A6(i) = 3.*(AL(i)-p(i))
        AR(i) = AL(i) - A6(i)
  else
        A6(i) = 3.*(AR(i)-p(i))
        AL(i) = AR(i) - A6(i)
  ENDIF
150   continue
  END DO
  elseif(LMT==2) THEN
  DO i=1,IM
  IF(abs(AR(i)-AL(i)) >= -A6(i)) go to 250
  fmin = p(i) + 0.25*(AR(i)-AL(i))**2/A6(i) + A6(i)*R12
  IF(fmin>=0.) go to 250
  IF(p(i)<AR(i) .AND. p(i)<AL(i)) THEN
        AR(i) = p(i)
        AL(i) = p(i)
        A6(i) = 0.
  elseif(AR(i) > AL(i)) THEN
        A6(i) = 3.*(AL(i)-p(i))
        AR(i) = AL(i) - A6(i)
  else
        A6(i) = 3.*(AR(i)-p(i))
        AL(i) = AR(i) - A6(i)
  ENDIF
250   continue
  END DO
  ENDIF
  RETURN
END SUBROUTINE lmtppm

SUBROUTINE A2C(U,V,IMR,JMR,j1,j2,CRX,CRY,dtdx5,DTDY5)
  IMPLICIT NONE
  INTEGER :: IMR,JMR,j1,j2
  REAL :: U(IMR,*),V(IMR,*),CRX(IMR,*),CRY(IMR,*),DTDX5(*),DTDY5
  INTEGER :: i,j

  DO j=j1,j2
  DO i=2,IMR
  CRX(i,J) = dtdx5(j)*(U(i,j)+U(i-1,j))
  END DO
  END DO

  DO j=j1,j2
  CRX(1,J) = dtdx5(j)*(U(1,j)+U(IMR,j))
  END DO

  DO i=1,IMR*JMR
  CRY(i,2) = DTDY5*(V(i,2)+V(i,1))
  END DO
  RETURN
END SUBROUTINE a2c

SUBROUTINE cosa(cosp,cose,JNP,PI,DP)
  IMPLICIT NONE
  INTEGER :: JNP
  REAL :: cosp(*),cose(*),PI,DP
  INTEGER :: JMR,j,jeq
  REAL :: ph5
  JMR = JNP-1
  DO j=2,JNP
    ph5  =  -0.5*PI + (REAL(J-1)-0.5)*DP
    cose(j) = cos(ph5)
  END DO

  JEQ = (JNP+1) / 2
  IF(JMR == 2*(JMR/2) ) THEN
  DO j=JNP, JEQ+1, -1
   cose(j) =  cose(JNP+2-j)
  enddo
  else
  ! cell edge at equator.
   cose(JEQ+1) =  1.
  DO j=JNP, JEQ+2, -1
   cose(j) =  cose(JNP+2-j)
   enddo
  ENDIF

  DO j=2,JMR
  cosp(j) = 0.5*(cose(j)+cose(j+1))
  END DO
  cosp(1) = 0.
  cosp(JNP) = 0.
  RETURN
END SUBROUTINE cosa

SUBROUTINE cosc(cosp,cose,JNP,PI,DP)
  IMPLICIT NONE
  INTEGER :: JNP
  REAL :: cosp(*),cose(*),PI,DP
  REAL :: phi
  INTEGER :: j

  phi = -0.5*PI
  DO j=2,JNP-1
  phi  =  phi + DP
  cosp(j) = cos(phi)
  END DO
    cosp(  1) = 0.
    cosp(JNP) = 0.

  DO j=2,JNP
    cose(j) = 0.5*(cosp(j)+cosp(j-1))
  END DO

  DO j=2,JNP-1
   cosp(j) = 0.5*(cose(j)+cose(j+1))
  END DO
  RETURN
END SUBROUTINE cosc

SUBROUTINE qckxyz(Q,qtmp,IMR,JNP,NLAY,j1,j2,cosp,acosp, &
        cross,IC,NSTEP)

  REAL,parameter :: tiny = 1.E-60
  INTEGER :: IMR,JNP,NLAY,j1,j2,IC,NSTEP
  REAL :: Q(IMR,JNP,NLAY),qtmp(IMR,JNP),cosp(*),acosp(*)
  LOGICAL :: cross
  INTEGER :: NLAYM1,len,ip,L,icr,ipy,ipx,i
  REAL :: qup,qly,dup,sum

  NLAYM1 = NLAY-1
  len = IMR*(j2-j1+1)
  ip = 0

  ! Top layer
  L = 1
    icr = 1
  CALL filns(q(1,1,L),IMR,JNP,j1,j2,cosp,acosp,ipy,tiny)
  IF(ipy==0) goto 50
  CALL filew(q(1,1,L),qtmp,IMR,JNP,j1,j2,ipx,tiny)
  IF(ipx==0) goto 50

  IF(cross) THEN
  CALL filcr(q(1,1,L),IMR,JNP,j1,j2,cosp,acosp,icr,tiny)
  ENDIF
  IF(icr==0) goto 50

  ! Vertical filling...
  DO i=1,len
  IF( Q(i,j1,1)<0.) THEN
  ip = ip + 1
      Q(i,j1,2) = Q(i,j1,2) + Q(i,j1,1)
      Q(i,j1,1) = 0.
  ENDIF
  enddo

50   continue
  DO L = 2,NLAYM1
  icr = 1

  CALL filns(q(1,1,L),IMR,JNP,j1,j2,cosp,acosp,ipy,tiny)
  IF(ipy==0) goto 225
  CALL filew(q(1,1,L),qtmp,IMR,JNP,j1,j2,ipx,tiny)
  IF(ipx==0) go to 225
  IF(cross) THEN
  CALL filcr(q(1,1,L),IMR,JNP,j1,j2,cosp,acosp,icr,tiny)
  ENDIF
  IF(icr==0) goto 225

  DO i=1,len
  IF( Q(I,j1,L)<0.) THEN

  ip = ip + 1
  ! From above
      qup =  Q(I,j1,L-1)
      qly = -Q(I,j1,L)
      dup  = min(qly,qup)
      Q(I,j1,L-1) = qup - dup
      Q(I,j1,L  ) = dup-qly
  ! Below
      Q(I,j1,L+1) = Q(I,j1,L+1) + Q(I,j1,L)
      Q(I,j1,L)   = 0.
  ENDIF
  ENDDO
225   CONTINUE
  END DO

  ! BOTTOM LAYER
  sum = 0.
  L = NLAY

  CALL filns(q(1,1,L),IMR,JNP,j1,j2,cosp,acosp,ipy,tiny)
  IF(ipy==0) goto 911
  CALL filew(q(1,1,L),qtmp,IMR,JNP,j1,j2,ipx,tiny)
  IF(ipx==0) goto 911

  CALL filcr(q(1,1,L),IMR,JNP,j1,j2,cosp,acosp,icr,tiny)
  IF(icr==0) goto 911

  DO  I=1,len
  IF( Q(I,j1,L)<0.) THEN
  ip = ip + 1

  ! From above

      qup = Q(I,j1,NLAYM1)
      qly = -Q(I,j1,L)
      dup = min(qly,qup)
      Q(I,j1,NLAYM1) = qup - dup
  ! From "below" the surface.
      sum = sum + qly-dup
      Q(I,j1,L) = 0.
   ENDIF
  ENDDO

911   continue

  IF(ip>IMR) THEN
  WRITE(6,*) 'IC=',IC,' STEP=',NSTEP, &
        ' Vertical filling pts=',ip
  ENDIF

  IF(sum>1.e-25) THEN
  WRITE(6,*) IC,NSTEP,' Mass source from the ground=',sum
  ENDIF
  RETURN
END SUBROUTINE qckxyz

SUBROUTINE filcr(q,IMR,JNP,j1,j2,cosp,acosp,icr,tiny)
  IMPLICIT NONE
  INTEGER :: IMR,JNP,j1,j2,icr
  REAL :: q(IMR,*),cosp(*),acosp(*),tiny
  INTEGER :: i,j
  REAL :: dq,dn,d0,d1,ds,d2
  icr = 0
  DO j=j1+1,j2-1
  DO i=1,IMR-1
  IF(q(i,j)<0.) THEN
  icr =  1
  dq  = - q(i,j)*cosp(j)
  ! N-E
  dn = q(i+1,j+1)*cosp(j+1)
  d0 = max(0.,dn)
  d1 = min(dq,d0)
  q(i+1,j+1) = (dn - d1)*acosp(j+1)
  dq = dq - d1
  ! S-E
  ds = q(i+1,j-1)*cosp(j-1)
  d0 = max(0.,ds)
  d2 = min(dq,d0)
  q(i+1,j-1) = (ds - d2)*acosp(j-1)
  q(i,j) = (d2 - dq)*acosp(j) + tiny
  ENDIF
  END DO
  IF(icr==0 .AND. q(IMR,j)>=0.) goto 65
  DO i=2,IMR
  IF(q(i,j)<0.) THEN
  icr =  1
  dq  = - q(i,j)*cosp(j)
  ! N-W
  dn = q(i-1,j+1)*cosp(j+1)
  d0 = max(0.,dn)
  d1 = min(dq,d0)
  q(i-1,j+1) = (dn - d1)*acosp(j+1)
  dq = dq - d1
  ! S-W
  ds = q(i-1,j-1)*cosp(j-1)
  d0 = max(0.,ds)
  d2 = min(dq,d0)
  q(i-1,j-1) = (ds - d2)*acosp(j-1)
  q(i,j) = (d2 - dq)*acosp(j) + tiny
  ENDIF
  END DO
  ! *****************************************
  ! i=1
  i=1
  IF(q(i,j)<0.) THEN
  icr =  1
  dq  = - q(i,j)*cosp(j)
  ! N-W
  dn = q(IMR,j+1)*cosp(j+1)
  d0 = max(0.,dn)
  d1 = min(dq,d0)
  q(IMR,j+1) = (dn - d1)*acosp(j+1)
  dq = dq - d1
  ! S-W
  ds = q(IMR,j-1)*cosp(j-1)
  d0 = max(0.,ds)
  d2 = min(dq,d0)
  q(IMR,j-1) = (ds - d2)*acosp(j-1)
  q(i,j) = (d2 - dq)*acosp(j) + tiny
  ENDIF
  ! *****************************************
  ! i=IMR
  i=IMR
  IF(q(i,j)<0.) THEN
  icr =  1
  dq  = - q(i,j)*cosp(j)
  ! N-E
  dn = q(1,j+1)*cosp(j+1)
  d0 = max(0.,dn)
  d1 = min(dq,d0)
  q(1,j+1) = (dn - d1)*acosp(j+1)
  dq = dq - d1
  ! S-E
  ds = q(1,j-1)*cosp(j-1)
  d0 = max(0.,ds)
  d2 = min(dq,d0)
  q(1,j-1) = (ds - d2)*acosp(j-1)
  q(i,j) = (d2 - dq)*acosp(j) + tiny
  ENDIF
  ! *****************************************
65   continue
  END DO

  DO i=1,IMR
  IF(q(i,j1)<0. .OR. q(i,j2)<0.) THEN
  icr = 1
  goto 80
  ENDIF
  enddo

80   continue

  IF(q(1,1)<0. .OR. q(1,jnp)<0.) THEN
  icr = 1
  ENDIF

  RETURN
END SUBROUTINE filcr

SUBROUTINE filns(q,IMR,JNP,j1,j2,cosp,acosp,ipy,tiny)
  IMPLICIT NONE
  INTEGER :: IMR,JNP,j1,j2,ipy
  REAL :: q(IMR,*),cosp(*),acosp(*),tiny
  REAL :: DP,CAP1,dq,dn,d0,d1,ds,d2
  INTEGER :: i,j
   ! LOGICAL first
   ! data first /.TRUE./
   ! save cap1

  !  IF(first) THEN
  DP = 4.*ATAN(1.)/REAL(JNP-1)
  CAP1 = IMR*(1.-COS((j1-1.5)*DP))/DP
   ! first = .FALSE.
   ! END IF

  ipy = 0
  DO j=j1+1,j2-1
  DO i=1,IMR
  IF(q(i,j)<0.) THEN
  ipy =  1
  dq  = - q(i,j)*cosp(j)
  ! North
  dn = q(i,j+1)*cosp(j+1)
  d0 = max(0.,dn)
  d1 = min(dq,d0)
  q(i,j+1) = (dn - d1)*acosp(j+1)
  dq = dq - d1
  ! South
  ds = q(i,j-1)*cosp(j-1)
  d0 = max(0.,ds)
  d2 = min(dq,d0)
  q(i,j-1) = (ds - d2)*acosp(j-1)
  q(i,j) = (d2 - dq)*acosp(j) + tiny
  ENDIF
  END DO
  END DO

  DO i=1,imr
  IF(q(i,j1)<0.) THEN
  ipy =  1
  dq  = - q(i,j1)*cosp(j1)
  ! North
  dn = q(i,j1+1)*cosp(j1+1)
  d0 = max(0.,dn)
  d1 = min(dq,d0)
  q(i,j1+1) = (dn - d1)*acosp(j1+1)
  q(i,j1) = (d1 - dq)*acosp(j1) + tiny
  ENDIF
  enddo

  j = j2
  DO i=1,imr
  IF(q(i,j)<0.) THEN
  ipy =  1
  dq  = - q(i,j)*cosp(j)
  ! South
  ds = q(i,j-1)*cosp(j-1)
  d0 = max(0.,ds)
  d2 = min(dq,d0)
  q(i,j-1) = (ds - d2)*acosp(j-1)
  q(i,j) = (d2 - dq)*acosp(j) + tiny
  ENDIF
  enddo

  ! Check Poles.
  IF(q(1,1)<0.) THEN
  dq = q(1,1)*cap1/REAL(IMR)*acosp(j1)
  DO i=1,imr
  q(i,1) = 0.
  q(i,j1) = q(i,j1) + dq
  IF(q(i,j1)<0.) ipy = 1
  enddo
  ENDIF

  IF(q(1,JNP)<0.) THEN
  dq = q(1,JNP)*cap1/REAL(IMR)*acosp(j2)
  DO i=1,imr
  q(i,JNP) = 0.
  q(i,j2) = q(i,j2) + dq
  IF(q(i,j2)<0.) ipy = 1
  enddo
  ENDIF

  RETURN
END SUBROUTINE filns

SUBROUTINE filew(q,qtmp,IMR,JNP,j1,j2,ipx,tiny)
  IMPLICIT NONE
  INTEGER :: IMR,JNP,j1,j2,ipx
  REAL :: q(IMR,*),qtmp(JNP,IMR),tiny
  INTEGER :: i,j
  REAL :: d0,d1,d2

  ipx = 0
  ! Copy & swap direction for vectorization.
  DO i=1,imr
  DO j=j1,j2
  qtmp(j,i) = q(i,j)
  END DO
  END DO

  DO i=2,imr-1
  DO j=j1,j2
  IF(qtmp(j,i)<0.) THEN
  ipx =  1
  ! west
  d0 = max(0.,qtmp(j,i-1))
  d1 = min(-qtmp(j,i),d0)
  qtmp(j,i-1) = qtmp(j,i-1) - d1
  qtmp(j,i) = qtmp(j,i) + d1
  ! east
  d0 = max(0.,qtmp(j,i+1))
  d2 = min(-qtmp(j,i),d0)
  qtmp(j,i+1) = qtmp(j,i+1) - d2
  qtmp(j,i) = qtmp(j,i) + d2 + tiny
  ENDIF
  END DO
  END DO

  i=1
  DO j=j1,j2
  IF(qtmp(j,i)<0.) THEN
  ipx =  1
  ! west
  d0 = max(0.,qtmp(j,imr))
  d1 = min(-qtmp(j,i),d0)
  qtmp(j,imr) = qtmp(j,imr) - d1
  qtmp(j,i) = qtmp(j,i) + d1
  ! east
  d0 = max(0.,qtmp(j,i+1))
  d2 = min(-qtmp(j,i),d0)
  qtmp(j,i+1) = qtmp(j,i+1) - d2

  qtmp(j,i) = qtmp(j,i) + d2 + tiny
  ENDIF
  END DO
  i=IMR
  DO j=j1,j2
  IF(qtmp(j,i)<0.) THEN
  ipx =  1
  ! west
  d0 = max(0.,qtmp(j,i-1))
  d1 = min(-qtmp(j,i),d0)
  qtmp(j,i-1) = qtmp(j,i-1) - d1
  qtmp(j,i) = qtmp(j,i) + d1
  ! east
  d0 = max(0.,qtmp(j,1))
  d2 = min(-qtmp(j,i),d0)
  qtmp(j,1) = qtmp(j,1) - d2

  qtmp(j,i) = qtmp(j,i) + d2 + tiny
  ENDIF
  END DO

  IF(ipx/=0) THEN
  DO j=j1,j2
  DO i=1,imr
  q(i,j) = qtmp(j,i)
  END DO
  END DO
  else

  ! Poles.
  IF(q(1,1)<0 .OR. q(1,JNP)<0.) ipx = 1
  ENDIF
  RETURN
END SUBROUTINE filew

SUBROUTINE zflip(q,im,km,nc)
  IMPLICIT NONE
  ! This routine flip the array q (in the vertical).
  INTEGER :: im,km,nc
  REAL :: q(im,km,nc)
  ! local dynamic array
  REAL :: qtmp(im,km)
  INTEGER :: IC,k,i

  DO IC = 1, nc

  DO k=1,km
  DO i=1,im
  qtmp(i,k) = q(i,km+1-k,IC)
  END DO
  END DO

  DO i=1,im*km
  q(i,1,IC) = qtmp(i,1)
  END DO
  END DO
  RETURN
END SUBROUTINE zflip