WW3/w3flx4md_8F90_source.html

#include "w3macros.h"

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

MODULE w3flx4md

  !/

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

  !/                  | WAVEWATCH III           NOAA/NCEP |

  !/                  |           H. L. Tolman            |

  !/                  |           S. Zieger               |

  !/                  |           Q. Liu                  |

  !/                  |                        FORTRAN 90 |

  !/                  | Last update :         24-Nov-2017 |

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

  !/

  !/    03-Jul-2006 : Origination.                        ( version 3.09 )

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

  !/    15-Mar-2011 : Implementation of Hwang (2011)

  !/                  parameterization.

  !/    24-Nov_2017 : Modifying CDFAC                     ( Q. Liu)

  !/

  !/    Copyright 2009 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 to Hwang ( 2011).

  !

  !     References:

  !          Hwang 2011: J Atmos Ocean Tech 28(3)  436-443

  !

  !  2. Variables and types :

  !

  !  3. Subroutines and functions :

  !

  !      Name      Type  Scope    Description

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

  !      W3FLX4    Subr. Public   Stresses according to Hwang (JTech, 2011)

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

  !

  !  4. Subroutines and functions used :

  !

  !      Name      Type  Module   Description

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

  !      STRACE    Subr. W3SERVMD Subroutine tracing.

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

  !

  !  5. Remarks :

  !

  !  6. Switches :

  !

  !     !/S  Enable subroutine tracing.

  !

  !  7. Source code :

  !/

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

  !/

  PUBLIC

  !/

CONTAINS

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

  SUBROUTINE w3flx4 ( ZWND, U10, U10D, UST, USTD, Z0, CD )

    !/

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

    !/                  | WAVEWATCH III           NOAA/NCEP |

    !/                  |           H. L. Tolman            |

    !/                  |                        FORTRAN 90 |

    !/                  | Last update :         03-Jul-2006 |

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

    !/

    !/    03-Jul-2006 : Origination.                        ( version 3.09 )

    !/

    !  1. Purpose :

    !

    !     Flux/stress computations according to Hwang (JTECH, 2011)

    !

    !  2. Method :

    !

    !     CD    = 1E-4 ( -0.016 U10**2 + 0.967U10 + 8.058)

    !     USTAR = U10 * SQRT( U10 )

    !

    !  3. Parameters :

    !

    !     Parameter list

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

    !       ZWND    Real   I   Wind height.

    !       U10     Real   I   Wind speed.

    !       U10D    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 w3odatmd, ONLY: ndse, iaproc, naperr

    USE w3gdatmd, ONLY: flx4a0

    USE w3servmd, ONLY: extcde

#ifdef W3_S

    USE w3servmd, ONLY: strace

#endif

    !/

    IMPLICIT NONE

    !/

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

    !/ Parameter list

    !/

    REAL, INTENT(IN)        :: ZWND, U10, U10D

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

    !/

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

    !/ Local parameters

    !/

#ifdef W3_S

    INTEGER, SAVE           :: IENT = 0

#endif

    !/

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

    !/

#ifdef W3_S

    CALL strace (ient, 'W3FLX4')

#endif

    !

    ! 1.  Tests ---------------------------------------------------------- *

    !

    IF ( abs(zwnd-10.) .GT. 0.01 ) THEN

      IF ( iaproc .EQ. naperr ) WRITE (ndse,1000) zwnd

      CALL extcde (1)

    END IF

    !

    ! 2.  Computation ---------------------------------------------------- *

    !

    !     To prevent the drag coefficient from dropping to zero at extreme

    !     wind speeds, we use a simple modification UST = 2.026 m/s for

    !     U10 greater than 50.33 m/s.

    !

    IF (u10 .GE. 50.33) THEN

      ust = 2.026 * sqrt(flx4a0)

      cd  = (ust/u10)**2

    ELSE

      cd  = flx4a0 * ( 8.058 + 0.967*u10 - 0.016*u10**2 ) * 1e-4

      ust = u10 * sqrt(cd)

    END IF

    !

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

    ustd   = u10d

    !

    RETURN

    !

    ! Formats

    !

1000 FORMAT (/' *** WAVEWATCH III ERROR IN W3FLX4 : '/               &

         '     HIGHT OF WIND SHOULD BE 10m IN THIS APPRACH '/   &

         '     ZWND =',f8.2,'m'/)

    !/

    !/ End of W3FLX4 ----------------------------------------------------- /

    !/

  END SUBROUTINE w3flx4

  !/

  !/ End of module W3FLX4MD -------------------------------------------- /

  !/

END MODULE w3flx4md