!> @file
!> @brief Flux/stress computations according to Hwang (2011).
!>
!> @author H. L. Tolman
!> @author S. Zieger
!> @author Q. Liu
!> @date 24-Nov-2017
!>
#include "w3macros.h"
!/ ------------------------------------------------------------------- /
!>
!> @brief Flux/stress computations according to Hwang ( 2011).
!>
!> @details Hwang 2011: J Atmos Ocean Tech 28(3) 436-443.
!>
!> @author H. L. Tolman
!> @author S. Zieger
!> @author 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.
!>
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
!/ ------------------------------------------------------------------- /
!>
!> @brief Flux/stress computations according to Hwang (JTECH, 2011).
!>
!> @verbatim
!> CD = 1E-4 ( -0.016 U10**2 + 0.967U10 + 8.058)
!> USTAR = U10 * SQRT( U10 )
!> @endverbatim
!>
!> @param[in] ZWND Wind height.
!> @param[in] U10 Wind speed.
!> @param[in] U10D Wind direction.
!> @param[out] UST Friction velocity.
!> @param[out] USTD Direction of friction velocity.
!> @param[out] Z0 Z0 in profile law.
!> @param[out] CD Drag coefficient.
!>
!> @author H. L. Tolman
!> @date 03-Jul-2006
!>
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