w3flx4md Module Reference

Flux/stress computations according to Hwang ( 2011). More...

Functions/Subroutines
subroutine	w3flx4 (ZWND, U10, U10D, UST, USTD, Z0, CD)
	Flux/stress computations according to Hwang (JTECH, 2011). More...

Detailed Description

Flux/stress computations according to Hwang ( 2011).

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

Author

H. L. Tolman

S. Zieger

Q. Liu

Date

24-Nov-2017

Copyright

Copyright 2009-2022 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.

Function/Subroutine Documentation

w3flx4()

subroutine w3flx4md::w3flx4	(	real, intent(in)	ZWND,
		real, intent(in)	U10,
		real, intent(in)	U10D,
		real, intent(out)	UST,
		real, intent(out)	USTD,
		real, intent(out)	Z0,
		real, intent(out)	CD
	)

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

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

Parameters

[in]	ZWND	Wind height.
[in]	U10	Wind speed.
[in]	U10D	Wind direction.
[out]	UST	Friction velocity.
[out]	USTD	Direction of friction velocity.
[out]	Z0	Z0 in profile law.
[out]	CD	Drag coefficient.

Author

H. L. Tolman

Date

03-Jul-2006

Definition at line 106 of file w3flx4md.F90.

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

References w3servmd::extcde(), w3gdatmd::flx4a0, w3odatmd::iaproc, w3odatmd::naperr, w3odatmd::ndse, and w3servmd::strace().

Referenced by gxexpo(), w3exnc(), w3expo(), and w3srcemd::w3srce().