Contents
USAGE:
[geo_strf_Montgomery, in_funnel] = gsw_geo_strf_Montgomery(SA,CT,p,interp_style)
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 at the sea surface. 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 25-term expression for specific volume of
McDougall et al. (2010).
Under the default setting, this function evaluates the pressure integral
of specific volume using SA and CT “interploted” with respect to pressure
using a scheme based on the method of Reiniger and Ross (1968). Our
method uses a weighted mean of (i) values obtained from linear
interpolation of the two nearest data points, and (ii) a linear
extrapolation of the pairs of data above and below. This "curve fitting"
method resembles the use of cubic splines. If the option “linear” is
chosen, the function interpolates Absolute Salinity and Conservative
Temperature linearly with presure in the vertical between “bottles”.
INPUT:
SA = Absolute Salinity [ g/kg ]
CT = Conservative Temperature [ deg C ]
p = sea pressure [ dbar ]
( ie. absolute pressure - 10.1325 dbar )
OPTIONAL:
interp_style = interpolation technique.
= if nothing is entered the programme defaults to "curved"
interpolation between bottles in the vertical.
= if "linear" or "lin" is entered then the programme
interpolates linearly between bottles in the
vertical.
SA & CT need to have the same dimensions.
p may have dimensions Mx1 or 1xN or MxN, where SA & CT are MxN.
OUTPUT:
geo_strf_Montgomery = Montgomery geostrophic streamfunction [ m^2/s^2 ]
in_funnel = 0, if SA, CT and p are outside the "funnel"
= 1, if SA, CT and p are inside the "funnel"
Note. The term "funnel" describes the range of SA, CT and p over which
the error in the fit of the computationally-efficient 25-term
expression for density was calculated (McDougall et al., 2010).
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;]
[geo_strf_Montgomery, in_funnel] = gsw_geo_strf_Montgomery(SA,CT,p)
geo_strf_Montgomery = in_funnel =
0.6009 1
-0.0091 1
-1.5948 1
-6.4287 1
-8.0176 1
-10.2415 1
AUTHOR:
Trevor McDougall and Paul Barker [ help_gsw@csiro.au ]
VERSION NUMBER:
2.0 (26th August, 2010)
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, P. M. Barker, C. Roberts-Thomson, R.
Feistel and R. W. Hallberg, 2010: A computationally efficient 25-term
expression for the density of seawater in terms of Conservative
Temperature, and related properties of seawater. To be submitted
to Ocean Science Discussions.
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