Contents
USAGE:
[IPV_vs_fNsquared_ratio_CT25, p_mid, in_funnel] =
gsw_IPV_vs_fNsquared_ratio_CT25(SA,CT,p,pr)
DESCRIPTION:
Calculates the ratio of the vertical gradient of potential density to
the vertical gradient of locally-referenced potential density. This
ratio is also the ratio of the planetary Isopycnal Potential
Vorticity (IPV) to f times N^2, hence the name for this variable,
IPV_vs_fNsquared_ratio_CT25 (see Eqn. (3.20.5) of IOC et al. (2010)).
The reference sea pressure of the potential density surface must have
a constant value.
IPV_vs_fNsquared_ratio_CT25 is evaluated at the mid pressure between
the individual data points in the vertical. This function uses the
computationally-efficient 25-term expression for density in terms of
SA, CT and p (McDougall et al., 2010).
INPUT:
SA = Absolute Salinity [ g/kg ]
CT = Conservative Temperature [ deg C ]
p = sea pressure [ dbar ]
(ie. absolute pressure - 10.1325 dbar)
pr = reference sea pressure of the potential density surface
[ dbar ]
SA & CT need to have the same dimensions.
p & pr may have dimensions 1x1 or 1xN or MxN, where SA & CT are MxN.
OUTPUT:
IPV_vs_fNsquared_ratio_CT25
= The ratio of the vertical gradient of potential
density referenced to pr, to the vertical gradient
of locally-referenced potential density.
IPV_vs_fNsquared_ratio_CT25 is ouput on the same
vertical (M-1)xN grid as p_mid.
IPV_vs_fNsquared_ratio_CT25 is dimensionless
[ unitless ]
p_mid = mid pressure between the individual points of the
p grid. That is, p_mid is on a (M-1)xN grid.
p_mid has units of dbar. [ dbar ]
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;]
pr = 0;
[IPV_vs_fNsquared_ratio_CT25, p_mid, in_funnel] = ...
gsw_IPV_vs_fNsquared_ratio_CT25(SA,CT,p,pr)
IPV_vs_fNsquared_ratio_CT25 =
0.999732065602075
0.996910961630710
0.986201941290951
0.931201954034279
0.859810378247326
p_mid =
1.0e+002 *
0.300000000000000
0.875000000000000
1.875000000000000
4.250000000000000
8.000000000000000
in_funnel =
1
1
1
1
1
AUTHOR:
Trevor McDougall and Paul Barker [ help_gsw@csiro.au ]
VERSION NUMBER:
2.0 (23rd 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 Eqn. (3.20.5) 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.
The software is available from http://www.TEOS-10.org