# gsw_geo_strf_Cunningham

Cunningham geostrophic streamfunction (75-term equation)

## Contents

## 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