# gsw_isopycnal_slope_ratio_CT25

    ratio of the slopes of isopycnals on the
    SA-CT diagram for p and pr
    (25-term equation)

## Contents

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

## USAGE:

    [isopycnal_slope_ratio_CT25, in_funnel] = gsw_isopycnal_slope_ratio_CT25(SA,CT,p,pr)

## DESCRIPTION:

    Calculates the ratio of alpha_CT/beta_CT at pressure p to that at
    pressure pr.  This function uses the computationally-efficient 25-term
    expression for density in terms of SA, CT & p (McDougall et al., 2010).

    Click for a more detailed description of the isopycnal
    slope ratio.

## INPUT:

    SA  =  Absolute Salinity                                        [ g/kg ]
    CT  =  Conservative Temperature                                [ deg C ]
    p   =  sea pressure                                             [ dbar ]
           (ie. absolute pressure - 10.1325 dbar)
    pr  =  reference pressure                                       [ dbar ]
           (ie. absolute reference pressure - 10.1325 dbar)

    SA & CT need to have the same dimensions.
    p & pr may have dimensions 1x1 or Mx1 or 1xN or MxN, where SA & CT
    are MxN

## OUTPUT:

    isopycnal_slope_ratio_CT25
                         =  The ratio of alpha_CT/beta_CT evaluated at
                            pressure p to that at pressure pr.  [ unitless ]
    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;

    [isopycnal_slope_ratio_CT25, in_funnel] = ...
                    gsw_isopycnal_slope_ratio_CT25(SA,CT,p,pr)

    isopycnal_slope_ratio_CT25 =         in_funnel =

     1.000443300473299                    1
     1.002247196919216                    1
     1.007323843523325                    1
     1.033841543679809                    1
     1.113488165501534                    1
     1.257603349708546                    1

## AUTHOR:

    Trevor McDougall, Paul Barker & David Jackett [ gsw_help@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 Eqn. (3.17.2) 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.

    This software is available from http://www.TEOS-10.org