# gsw_geo_strf_PISH

Pressure intergrated steric height PISH (75-term equation)

## Contents

## USAGE:

geo_strf_PISH = gsw_geo_strf_PISH(SA,CT,p,p_ref)

## DESCRIPTION:

Calculates pressure-integrated steric height PISH as the integral of pressure multiplied by specific volume anomaly from the pressure p of the “bottle” to the reference pressure p_ref, divided by the constant value of the gravitational acceleration, 9.7963 m s^-2, this being the gravitational acceleration averaged over the surface of the global ocean (see page 46 of Griffies, 2004).

This function evaluates the pressure integral of specific volume using SA and CT interpolated with respect to the intergral of bouyancy frequency N2 using the method of Barker et al. (2017). This "curve fitting" method uses a Piecewise Cubic Hermite Interpolating Polynomial to produce a smooth curve with minimal artificial watermasses between the observed data points.

The reference values used for the specific volume anomaly are SSO = 35.16504 g/kg and CT = 0 deg C. This function calculates specific volume anomaly using the computationally efficient expression for specific volume of Roquet et al. (2015).

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). For dynamical oceanography we may take the 75-term rational function expression for specific volume as essentially reflecting the full accuracy of TEOS-10. 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 PISH. |

## INPUT:

SA = Absolute Salinity [ g/kg ] CT = Conservative Temperature [ deg C ] p = sea pressure [ dbar ] ( i.e. absolute pressure - 10.1325 dbar ) p_ref = reference pressure [ dbar ] ( i.e. reference absolute pressure - 10.1325 dbar )

SA & CT need to have the same dimensions. p may have dimensions Mx1 or 1xN or MxN, where SA & CT are MxN. p_ref needs to be a single value, it can have dimensions 1x1 or Mx1 or 1xN or MxN.

## OUTPUT:

geo_strf_PISH = Pressure intergrated steric height [ kg s^2 ] The output geo_strf_PISH has dimensions 1xN, where N is the number of profiles in the input data. Note. If p_ref exceeds the pressure of the deepest “bottle” on a vertical profile, then the pressure-integrated steric height is returned as NaN.

## EXAMPLE 1:

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 = [ 10; 50; 125; 250; 600; 1000;] p_ref = 1000

geo_strf_PISH = gsw_geo_strf_PISH(SA,CT,p,p_ref)

geo_strf_PISH =

5.766680282284854e+06

## AUTHOR:

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

## VERSION NUMBER:

3.06 (15th May, 2017)

## REFERENCES:

Barker, P.M., T.J. McDougall and S.J. Wotherspoon, 2017: An interpolation method for oceanographic data.J. Atmosph. Ocean. Tech.(To be submitted).

Griffies, S. M., 2004: Fundamentals of Ocean Climate Models. Princeton, NJ: Princeton University Press, 518 pp + xxxiv.

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 Eqn. (3.31.4) and section 3.31 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 and P.M. Barker, 2015: Accurate polynomial expressions for the density and specific volume of seawater using the TEOS-10 standard.Ocean Modelling,90, pp. 29-43. http://dx.doi.org/10.1016/j.ocemod.2015.04.002

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