# gsw_enthalpy_diff_CT

    difference of enthalpy at two pressures

## Contents

- USAGE:
- DESCRIPTION:
- INPUT:
- OUTPUT:
- EXAMPLE:
- AUTHOR:
- VERSION NUMBER:
- REFERENCES:

## USAGE:

    enthalpy_diff_CT = gsw_enthalpy_diff_CT(SA,CT,p_shallow,p_deep)

## DESCRIPTION:

    Calculates the difference of the specific enthalpy of seawater between
    two different pressures, p_deep (the deeper pressure) and p_shallow
    (the shallower pressure), at the same values of SA and CT.  The output
    (enthalpy_diff) is the specific enthalpy evaluated at (SA,CT,p_deep)
    minus the specific enthalpy at (SA,CT,p_shallow).

    Note that this function uses the full Gibbs function.  There is an
    alternative to calling this function, namely
    gsw_enthalpy_diff_CT25(SA,CT,p), which uses the computationally
    efficient 25-term expression for density in terms of SA, CT and p
    (McDougall et al., (2010)).  For SA, CT and p values which fall inside
    the oceanographic "funnel" (McDougall et al., 2010), this
    computationally efficient (i. e. faster) 25-term version fits the
    underlying laboratory density data almost as well as does the density
    derived from the full TEOS-10 Gibbs function.

    Click for a more detailed description of the difference
    of enthalpy between two pressures.

## INPUT:

    SA         =  Absolute Salinity                                 [ g/kg ]
    CT         =  Conservative Temperature                         [ deg C ]
    p_shallow  =  upper sea pressure                                [ dbar ]
                  (ie. shallower absolute pressure - 10.1325 dbar)
    p_deep     =  lower sea pressure                                [ dbar ]
                  (ie. deeper absolute pressure - 10.1325 dbar)

    p_shallow and p_deep may have dimensions Mx1 or 1xN or MxN,
    where SA and CT are MxN.

## OUTPUT:

    enthalpy_diff_CT  =  difference of specific enthalpy          [ J/kg ]
                           (deep minus shallow)

## EXAMPLE:

    SA =         [34.7118; 34.8915; 35.0256; 34.8472; 34.7366; 34.7324;]
    CT =         [28.8099; 28.4392; 22.7862; 10.2262;  6.8272;  4.3236;]
    p_shallow =  [     10;      50;     125;     250;     600;    1000;]
    p_deep    =  [    110;     150;     225;     350;     700;    1100;]

    enthalpy_diff_CT = gsw_enthalpy_diff_CT(SA,CT,p_shallow,p_deep)

    enthalpy_diff_CT =

    1.0e+002 *

     9.784255933006788
     9.780212984387035
     9.759516776633390
     9.727494888619550
     9.708138965635516
     9.687770207718350

## AUTHOR:

     Trevor McDougall and Paul Barker       [ help_gsw@csiro.au ]

## VERSION NUMBER:

    2.0 (29th September, 2010)

## REFERENCES:

    IOC, SCOR and IAPSO, 2010: The international thermodynamic equation of
     seawater - 2010: Calculation and use of thermodynamic properties.
     Intergovernmental Oceanographic Commission, Manuals and Guides No. 56,
     UNESCO (English), 196 pp.  Available from the TEOS-10 web site.
      See Eqns. (3.32.2) of this TEOS-10 Manual.

    McDougall T. J., D. R. Jackett, P. M. Barker, C. Roberts-Thomson, R.
     Feistel and R. W. Hallberg, 2010:  A computationally efficient 25-term
     expression for the density of seawater in terms of Conservative
     Temperature, and related properties of seawater.  To be submitted
     to Ocean Science Discussions.

    The software is available from http://www.TEOS-10.org