Fortran: Module Interface eqstate -- the equation of state (Source File: eqstate.F90)

INTERFACE:

    MODULE eqstate

DESCRIPTION:

Computes the density, ${\langle \rho \rangle}$, and buoyancy from the salinity, $S$, the temperature, $\Theta$, and the thermodynamic pressure, $P$, according to an equation of state,

$${\langle \rho \rangle} = \hat{\rho} (S,\Theta,P) \quad .$$ (242)

The following remark on the thermodynamic interpretation of density, temperature, and pressure is useful here. If $\Theta$ is identified with the in-situ temperature, and $P$ with the in-situ pressure, then ${\langle \rho \rangle}$ will be the in-situ density. On the other hand, if $P$ is identified with the surface pressure, and $\Theta$ with the potential temperature, the same equation of state, (242), will yield ${\langle \rho \rangle}$ as the potential density. Note that the quantity sigma_t found in the GOTM output is simply computed from ${\langle \rho \rangle}$ - 1000 kg m$^{-3}$, and may therefore adopt different meanings.

At present, two different models for the equation of state ("modes"), and four different "methods" how to evalute the equation of state are implemented.

Modes:

1. The UNESCO equation of state according to Fofonoff and Millard (1983)
2. The Jackett et al. (2005) equation of state

Methods:

1. the full equation of state -- including pressure effects
2. the full equation of state -- without pressure effects
3. the linearised equation of state
4. a general linear form of the equation of state

USES:

    IMPLICIT NONE
 
    default: all is private.
    private

PUBLIC MEMBER FUNCTIONS:

    public init_eqstate,eqstate1,eos_alpha,eos_beta,unesco,rho_feistel

REVISION HISTORY:

    Original author(s): Hans Burchard & Karsten Bolding
    $Log: eqstate.F90,v $
    Revision 1.9  2010-09-17 12:53:53  jorn
    extensive code clean-up to ensure proper initialization and clean-up of all variables
    Revision 1.8  2008-08-01 07:33:14  lars
    modified documentation
    Revision 1.7  2007-01-06 11:49:13  kbk
    namelist file extension changed .inp --> .nml
    Revision 1.6  2005/06/27 13:44:07  kbk
    modified + removed traling blanks
    Revision 1.5  2003/03/28 09:20:36  kbk
    added new copyright to files
    Revision 1.4  2003/03/28 08:06:33  kbk
    removed tabs
    Revision 1.3  2003/03/10 08:54:16  gotm
    Improved documentation and cleaned up code
    Revision 1.2  2001/11/27 19:44:32  gotm
    Fixed an initialisation bug
    Revision 1.1.1.1  2001/02/12 15:55:58  gotm
    initial import into CVS