# gsw_geo_strf_Montgomery

Montgomery geostrophic streamfunction (75-term equation)

## Contents

## USAGE:

geo_strf_Montgomery = gsw_geo_strf_Montgomery(SA,CT,p,p_ref)

## DESCRIPTION:

Calculates the Montgomery geostrophic streamfunction (see Eqn. (3.28.1) of IOC et al. (2010)). This is the geostrophic streamfunction for the difference between the horizontal velocity at the pressure concerned, p, and the horizontal velocity on the pressure surface, p_ref. The Montgomery geostrophic streamfunction is the geostrophic streamfunction for flow in a specifc volume anomaly surface. The reference values used for the specific volume anomaly are SA = SSO = 35.16504 g/kg and CT = 0 deg C. This function calculates specific volume anomaly using the computationally efficient 75-term expression for specific volume of Roquet et al. (2015).

Note that p_ref, is the reference pressure to which the streamfunction is referenced. When p_ref is zero, "gsw_geo_strf_Montgomery" returns the Montgomery geostrophic streamfunction with respect to the sea surface, otherwise, the function returns the geostrophic streamfunction with respect to the (deep) reference pressure p_ref.

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 Montgomery streamfunction. |

## INPUT:

SA = Absolute Salinity [ g/kg ] CT = Conservative Temperature [ deg C ] p = sea pressure [ dbar ] ( i.e. absolute pressure - 10.1325 dbar ) p_ref = sea reference pressure [ dbar ] ( i.e. absolute reference 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_Montgomery = Montgomery geostrophic streamfunction [ m^2/s^2 ]

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

geo_strf_Montgomery = gsw_geo_strf_Montgomery(SA,CT,p,p_ref)

geo_strf_Montgomery =

17.430178569934043 17.347742601355499 15.797901315278487 11.254606618695270 9.838213724187165 7.638338957772513

## AUTHOR:

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

## VERSION NUMBER:

3.06.12 (15th June, 2020)

## 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 section 3.28 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.

Montgomery, R. B., 1937: A suggested method for representing gradient flow in isentropic surfaces. Bull. Amer. Meteor. Soc. 18, 210-212.

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