# gsw_enthalpy_diff

difference of enthalpy between two pressures (75-term equation)

## Contents

## USAGE:

enthalpy_diff = gsw_enthalpy_diff(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. This function uses the computationally-efficient 75-term expression for specific volume in terms of SA, CT and p (Roquet et al., 2015). 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 the 75-term equation has been fitted in a restricted range of parameter space, and is most accurate inside the "oceanographic funnel" described in McDougall et al. (2003). The GSW library function "gsw_infunnel(SA,CT,p)" is avaialble to be used if one wants to test if some of one's data lies outside this "funnel".

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

## EXAMPLE:

SA = [34.7118; 34.8915; 35.0256; 34.8472; 34.7366; 34.7324;] CT = [28.7856; 28.4329; 22.8103; 10.2600; 6.8863; 4.4036;] p_shallow = [ 10; 50; 125; 250; 600; 1000;] p_deep = [ 110; 150; 225; 350; 700; 1100;]

enthalpy_diff = gsw_enthalpy_diff(SA,CT,p_shallow,p_deep)

enthalpy_diff =

1.0e+002 *

9.784180644568052 9.780195056105020 9.759587700515114 9.727552719534447 9.708223170174454 9.687871289079633

## AUTHOR:

Trevor McDougall and Paul Barker [ help@teos-10.org ]

## VERSION NUMBER:

3.05 (16th February, 2015)

## 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) and (A.30.6) of this TEOS-10 Manual.

McDougall, T.J., D.R. Jackett, D.G. Wright and R. Feistel, 2003: Accurate and computationally efficient algorithms for potential temperature and density of seawater. J. Atmosph. Ocean. Tech., 20, pp. 730-741.

Roquet, F., G. Madec, T.J. McDougall, P.M. Barker, 2015: Accurate polynomial expressions for the density and specifc volume of seawater using the TEOS-10 standard. Ocean Modelling.

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