gppref.F90

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SUBROUTINE gppref(KPROMA,KSTART,KPROF,KFLEV,PVAH,PVBH,PALPH,PRESH,PRESF)

!**** *GPPREF* - Computes full level pressure

!     Purpose.
!     --------
!           Computes pressures at half and full model levels.

!**   Interface.
!     ----------
!        *CALL* *GPPREF(...)

!        Explicit arguments :
!        --------------------
!                              KPROMA :  dimensioning
!                              KSTART :  start of work
!                              KPROF  :  depth of work
!                              KFLEV     : vert. dimensioning
!                              PVAH(KFLEV),PVBH(KFLEV)- vertical coordinate
!                              PALPH (KPROMA,KFLEV)  - COEFF OF THE HYDROST
!                              PRESH(KPROMA,0:KFLEV) - HALF LEVEL PRESSURE
!                              PRESF(KPROMA,KFLEV)   - FULL LEVEL PRESSURE
!
!        Implicit arguments :  NONE.
!        --------------------

!     Method.
!     -------
!        See documentation

!     Externals.  None.
!     ----------

!     Reference.
!     ----------
!        ECMWF Research Department documentation of the IFS

!                                PHk*ln(PHk) - PHk-1*ln(PHk-1)
!     Full level P: ln(PFk) = [ ------------------------------- - 1. ]
!                                        PHk - PHk-1

!     which simplifies to:  PFk = Pk+1/2 * exp(-ALPHA)

!     In case of NDLNPR=1 it becomes even simpler (no need of LAPRXP any
!     more in principle !) :
!                           PFk = Pk+1/2 * (1.-ALPHA) except at the top
!     level :
!                           PF1 = P1.5 / (2+Cv/R)

!     Author.
!     -------
!        Erik Andersson, Mats Hamrud and Philippe Courtier  *ECMWF*

!     Modifications.
!     --------------
!        Original : 92-11-23
!        Modified : 95-01-31 by Radmila Bubnova: correction in the case
!                            of the other approximation of d (ln p).
!        Modified : 00-11-22 by Agathe Untch: modifications for vertical
!                            finite elements
!        M.Hamrud      01-Oct-2003 CY28 Cleaning
!        Modified : 04-11-15 by K. YESSAD: improve the hierarchy of tests
!        Modified : 15-Feb-2005 by K. YESSAD: ZTOPPRES becomes TOPPRES
!     ------------------------------------------------------------------

USE parkind1  ,ONLY : jpim     ,jprb
USE yomhook   ,ONLY : lhook,   dr_hook

USE yomct0   , ONLY : laprxpk
USE yomdyn   , ONLY : ndlnpr
USE yomcst   , ONLY : rd       ,rcvd
USE yomcver  , ONLY : lvertfe
USE yomgem   , ONLY : vaf      ,vbf      ,toppres

!     ------------------------------------------------------------------

IMPLICIT NONE

INTEGER(KIND=JPIM),INTENT(IN)    :: KPROMA 
INTEGER(KIND=JPIM),INTENT(IN)    :: KFLEV 
INTEGER(KIND=JPIM),INTENT(IN)    :: KSTART 
INTEGER(KIND=JPIM),INTENT(IN)    :: KPROF 
REAL(KIND=JPRB)                  :: PVAH(0:kflev) ! Argument NOT used
REAL(KIND=JPRB)                  :: PVBH(0:kflev) ! Argument NOT used
REAL(KIND=JPRB)   ,INTENT(IN)    :: PALPH(kproma,kflev) 
REAL(KIND=JPRB)   ,INTENT(IN)    :: PRESH(kproma,0:kflev) 
REAL(KIND=JPRB)   ,INTENT(OUT)   :: PRESF(kproma,kflev) 

!     ------------------------------------------------------------------

INTEGER(KIND=JPIM) :: IFIRST, JLEV, JLON
REAL(KIND=JPRB) :: ZMUL
REAL(KIND=JPRB) :: ZHOOK_HANDLE

!     ------------------------------------------------------------------

IF (lhook) CALL dr_hook('GPPREF',0,zhook_handle)

!     ------------------------------------------------------------------

!*       1.    Level to begin normal computations
!              ----------------------------------

! This is introduced to allow the use of GPPREF without the implicit
! assumption that the top level input for pressure is 0 hPa.
! This restriction is only necessary in the case of use of NDLNPR=1.
!
! LVERTFE : .T./.F. Finite element/conventional vertical discretisation.
! NDLNPR  : NDLNPR=0: conventional formulation of delta, i.e. ln(P(l)/P(l-1)).
!           NDLNPR=1: formulation of delta used in non hydrostatic model,
! LAPRXPK : way of computing full-levels pressures in primitive equation
!
lvertfe=.true.    !!!!! A REVOIR (MPL) comment faut-il vraiment calculer PRESF ?

IF ((.NOT.lvertfe).AND.(ndlnpr == 1)) THEN
  IF(presh(kstart,0) <= toppres)THEN
    ifirst=2
  ELSE
    ifirst=1
    DO jlon=kstart,kprof
      IF(presh(jlon,0) <= toppres)THEN
        ifirst=2
        EXIT
      ENDIF
    ENDDO
  ENDIF
ENDIF

!     ------------------------------------------------------------------

!*       2.    COMPUTES FULL LEVEL PRESSURES.
!              ------------------------------

IF (lvertfe) THEN
  DO jlev=1,kflev
!   print *,'GPPREF: LVERTFE KFLEV KSTART KPROF JLEV',LVERTFE,KFLEV,KSTART,KPROF,JLEV
    presf(kstart:kprof,jlev)=vaf(jlev)+vbf(jlev)*presh(kstart:kprof,kflev)  
  ENDDO
ELSE
  IF (ndlnpr == 0) THEN
    IF (laprxpk) THEN
      DO jlev=1,kflev
        DO jlon=kstart,kprof
          presf(jlon,jlev)=(presh(jlon,jlev-1)+presh(jlon,jlev))*0.5_jprb
        ENDDO
      ENDDO
    ELSE
      DO jlev=1,kflev
        DO jlon=kstart,kprof
          presf(jlon,jlev)=exp(-palph(jlon,jlev))*presh(jlon,jlev)
        ENDDO
      ENDDO
    ENDIF
  ELSEIF (ndlnpr == 1) THEN
    DO jlev=ifirst,kflev
      DO jlon=kstart,kprof
        presf(jlon,jlev)=(1.0_jprb-palph(jlon,jlev))*presh(jlon,jlev)
      ENDDO
    ENDDO
    zmul=1.0_jprb/(2.0_jprb+rcvd/rd)
    DO jlev=1,ifirst-1
      DO jlon=kstart,kprof
        presf(jlon,jlev)=presh(jlon,jlev)*zmul
      ENDDO
    ENDDO
  ENDIF
ENDIF

!     ------------------------------------------------------------------

IF (lhook) CALL dr_hook('GPPREF',1,zhook_handle)
END SUBROUTINE gppref