# gsw_geo_strf_Cunningham

    Cunningham geostrophic streamfunction (75-term equation)

## Contents

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

## USAGE:

    geo_strf_Cunningham = gsw_geo_strf_Cunningham(SA,CT,p,p_ref)

## DESCRIPTION:

    Calculates the Cunningham geostrophic streamfunction (see Eqn. (3.29.2)
    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.  This
    function calculates specific volume anomaly using the computationally
    efficient 75-term expression for specific volume (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_Cunningham" returns
    the Cunningham 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 the Cunningham
    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 = 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_Cunningham = Cunningham 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_Cunningham = gsw_geo_strf_Cunningham(SA,CT,p,p_ref)

    geo_strf_Cunningham =

      18.035182792737032
      17.964351021728362
      16.390453892774531
      11.424814317026176
       9.580191747536446
       7.123551681892423

## AUTHOR:

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

## VERSION NUMBER:

    3.06 (15th May, 2017)

## REFERENCES:

    Cunningham, S.A., 2000: Circulation and volume flux of the North
     Atlantic using syoptic hydrographic data in a Bernoulli inverse.
     J. Marine Res., 58, 1-35.

    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 3.29 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