# gsw_geo_strf_Montgomery

    Montgomery geostrophic streamfunction (75-term equation)

## Contents

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

## 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 =

      18.035422429373796
      17.970321709767731
      16.423439762656812
      11.497449376660818
       9.869060689172082
       7.638338957772513

## AUTHOR:

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

## VERSION NUMBER:

    3.06 (15th May, 2017)

## 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