gsw_IPV_vs_fNsquared_ratio_CT25

Ratio of the vertical gradient of potential
density (with reference pressure, pr), to 
the vertical gradient of locally-referenced 
potential density (25-term equation)

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).
TEOS-10
Click for a more detailed description of the
IPV vs fNsquared_ratio.

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