WW3/w3flx3md_8F90_source.html

#include "w3macros.h"

!/ ------------------------------------------------------------------- /

MODULE w3flx3md

  !/

  !/                  +-----------------------------------+

  !/                  | WAVEWATCH III           NOAA/NCEP |

  !/                  |           H. L. Tolman            |

  !/                  |                        FORTRAN 90 |

  !/                  | Last update :         20-Apr-2010 |

  !/                  +-----------------------------------+

  !/

  !/    05-Jul-2006 : Origination.                        ( version 3.09 )

  !/    29-May-2009 : Preparing distribution version.     ( version 3.14 )

  !/    20-Apr-2010 : Fix INTENT of UST.                ( version 3.14.1 )

  !/

  !/    Copyright 2009-2010 National Weather Service (NWS),

  !/       National Oceanic and Atmospheric Administration.  All rights

  !/       reserved.  WAVEWATCH III is a trademark of the NWS.

  !/       No unauthorized use without permission.

  !/

  !  1. Purpose :

  !

  !     FLux/stress computations according Tolman and Chalikov (1996).

  !     Cap on flux added compared to W3FLX2.

  !

  !  2. Variables and types :

  !

  !  3. Subroutines and functions :

  !

  !      Name      Type  Scope    Description

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

  !      W3FLX3    Subr. Public   Stresses according to TC (1996).

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

  !

  !  4. Subroutines and functions used :

  !

  !      Name      Type  Module   Description

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

  !      STRACE    Subr. W3SERVMD Subroutine tracing.

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

  !

  !  5. Remarks :

  !

  !     - Originally used with source term !/ST2.

  !

  !  6. Switches :

  !

  !     !/S  Enable subroutine tracing.

  !

  !  7. Source code :

  !/

  !/ ------------------------------------------------------------------- /

  PUBLIC

  !/

CONTAINS

  !/ ------------------------------------------------------------------- /

  SUBROUTINE w3flx3 ( ZWIND, DEPTH, FP, U, UDIR, UST, USTD, Z0, CD )

    !/

    !/                  +-----------------------------------+

    !/                  | WAVEWATCH III           NOAA/NCEP |

    !/                  |           H. L. Tolman            |

    !/                  |                        FORTRAN 90 |

    !/                  | Last update :         10-Jan-2014 |

    !/                  +-----------------------------------+

    !/

    !/    05-Jul-2006 : Origination.                        ( version 3.09 )

    !/    20-Apr-2010 : Fix INTENT of UST.                ( version 3.14.1 )

    !/    10-Jan-2014 : Add max on division by UST          ( version 4.18 )

    !/                  (This was already done for W3FLX2 on 16 Sep 2011)

    !/    10-Jan-2014 : Add a min value for FP              ( version 4.18 )

    !/

    !  1. Purpose :

    !

    !     FLux/stress computations according Tolman and Chalikov (1996).

    !     Cap on flux added compared to W3FLX2.

    !

    !  2. Method :

    !

    !  3. Parameters :

    !

    !     Parameter list

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

    !       ZWIND   Real   I   Hight of wind.

    !       DEPTH   Real   I   Depth.

    !       FP      Real   I   Peak frequency.

    !       U       Real   I   Wind speed.

    !       UDIR    Real   I   Wind direction.

    !       UST     Real   O   Friction velocity.

    !       USTD    Real   0   Direction of friction velocity.

    !       Z0      Real   O   z0 in profile law.

    !       CD      Real   O   Drag coefficient.

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

    !

    !  4. Subroutines used :

    !

    !      Name      Type  Module   Description

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

    !      STRACE    Subr. W3SERVMD Subroutine tracing.

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

    !

    !  5. Called by :

    !

    !      Name      Type  Module   Description

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

    !      W3SRCE    Subr. W3SRCEMD Source term integration.

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

    !

    !  6. Error messages :

    !

    !       None.

    !

    !  7. Remarks :

    !

    !  8. Structure :

    !

    !     See source code.

    !

    !  9. Switches :

    !

    !     !/S  Enable subroutine tracing.

    !

    ! 10. Source code :

    !

    !/ ------------------------------------------------------------------- /

    USE constants

    USE w3gdatmd, ONLY: nittin, cinxsi, cd_max, cap_id

    USE w3odatmd, ONLY: ndse, iaproc, naperr

    USE w3servmd, ONLY: extcde

#ifdef W3_S

    USE w3servmd, ONLY: strace

#endif

    USE w3dispmd, ONLY: dsie, n1max, ewn1

    !/

    IMPLICIT NONE

    !/

    !/ ------------------------------------------------------------------- /

    !/ Parameter list

    !/

    REAL, INTENT(IN)        :: ZWIND, DEPTH, FP, U, UDIR

    REAL, INTENT(INOUT)     :: UST

    REAL, INTENT(OUT)       :: USTD, Z0, CD

    !/

    !/ ------------------------------------------------------------------- /

    !/ Local parameters

    !/

    INTEGER                 :: I1, ITT

#ifdef W3_S

    INTEGER, SAVE           :: IENT = 0

#endif

    REAL                    :: SQRTH, SIX, R1, WNP, CP, UNZ, ALPHA, &

         RDCH, AFP

    !/

    !/ ------------------------------------------------------------------- /

    !/

#ifdef W3_S

    CALL strace (ient, 'W3FLX3')

#endif

    !

    ! 1.  Peak phase velocity -------------------------------------------- *

    !

    ! ----- start of inlined and reduced WAVNU1 -----

    !

    afp    = tpi * max( fp, 0.001)

    !

    sqrth  = sqrt( depth )

    six    = afp * sqrth

    i1     = int( six / dsie )

    IF (i1.LE.n1max) THEN

      r1 = six/dsie - real(i1)

      wnp    = ( (1.-r1)*ewn1(i1) + r1*ewn1(i1+1) ) / depth

    ELSE

      wnp    = afp * afp / grav

    END IF

    !

    ! -----  end of inlined and reduced WAVNU1  -----

    !

    cp     = afp / wnp

    !

    ! 2.  Itterative stress computation ---------------------------------- *

    !

    unz    = max( 0.01 , u )

    ustd   = udir

    !

    DO itt=1, nittin

      alpha  = 0.57 / ( cp / max(ust,0.0001) )**(1.5)

      rdch   = max( 0. ,                                           &

           log( ( zwind * grav) / ( cinxsi * sqrt(alpha) * unz**2) ) )

      cd     = 0.001 * ( 0.021 + 10.4 / (rdch**1.23+1.85) )

      ust    = sqrt(cd) * unz

      z0    = zwind * exp( -0.4 / sqrt(cd) )

    END DO

    !

    ! 3.  Apply limit to drag coefficient -------------------------------- *

    !

    IF ( cap_id .EQ. 0 ) THEN

      cd     = min( cd_max, cd )

    ELSE

      cd     = cd_max * tanh( cd / cd_max )

    END IF

    !

    ust    = sqrt(cd) * unz

    z0     = zwind * exp( -0.4 / sqrt(cd) )

    !

    RETURN

    !

    ! Formats

    !

    !/

    !/ End of W3FLX3 ----------------------------------------------------- /

    !/

  END SUBROUTINE w3flx3

  !/

  !/ End of module W3FLX3MD -------------------------------------------- /

  !/

END MODULE w3flx3md