# gsw_ntp_pt_vs_CT_ratio

ratio of gradients of potential temperature
and Conservative Temperature in a neutral
tangent plane (in a locally-referenced
potential density surface) (75-term equation)

## USAGE:

ntp_pt_vs_CT_ratio = gsw_ntp_pt_vs_CT_ratio(SA,CT,p)

## DESCRIPTION:

Calculates the ratio of the two-dimensional gradient of potential
temperature versus that of Conservative Temperature, CT, along the
neutral tangent plane.  The potential temperature is the regular one
which has a reference sea pressure of 0 dbar.  Part of the calculation
uses the computationally-efficient 75-term expression for specific
volume in terms of SA, CT and p (Roquet et al., 2015).
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".

## INPUT:

SA  =   Absolute Salinity                                       [ g/kg ]
CT  =   Conservative Temperature                               [ deg C ]
p   =   sea pressure                                            [ dbar ]
( i.e. absolute pressure - 10.1325 dbar )
SA & CT need to have the same dimensions.
p may have dimensions 1x1 or Mx1 or 1xN or MxN, where SA & CT are MxN.

## OUTPUT:

ntp_pt_vs_CT_ratio  =  The ratio of the spatial gradient of
potential temperature versus that of
Conservative Temperature in the
neutral tangent plane (ntp).         [ unitless ]

## 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;]
ntp_pt_vs_CT_ratio = gsw_ntp_pt_vs_CT_ratio(SA,CT,p)
ntp_pt_vs_CT_ratio =
1.016134758732110
1.016088712417197
1.011784401675508
1.004314345783137
1.003011679980744
1.002334099137641

## AUTHOR:

Trevor McDougall and Paul Barker      [ help@teos-10.org ]

## VERSION NUMBER:

3.05 (16th February, 2015)

## 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. (A.14.5) 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, P.M. Barker, 2015: Accurate
polynomial expressions for the density and specifc volume of seawater
using the TEOS-10 standard. Ocean Modelling.
This software is available from http://www.TEOS-10.org