# gsw_pt_from_CT

**potential temperature from Conservative Temperature**

## Contents

## USAGE:

pt = gsw_pt_from_CT(SA,CT)

## DESCRIPTION:

Calculates potential temperature (with a reference sea pressure of zero
dbar) from Conservative Temperature. This function uses 1.5 iterations
through a modified Newton-Raphson (N-R) iterative solution proceedure,
starting from a rational-function-based initial condition for both pt
and dCT_dpt (McDougall and Wotherspoon, 2013).

## INPUT:

SA = Absolute Salinity [ g/kg ]
CT = Conservative Temperature [ deg C ]

SA & CT need to have the same dimensions.

## OUTPUT:

pt = potential temperature referenced to a sea [ deg C ]
pressure of zero dbar (ITS-90)

## 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;]

pt = gsw_pt_from_CT(SA,CT)

pt =

28.783177048624573
28.420955597191984
22.784953468087107
10.230534394434429
6.829216587061605
4.324534835990236

## AUTHOR:

Trevor McDougall, David Jackett, Claire Roberts-Thomson & 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 sections 3.1 and 3.3 of this TEOS-10 Manual.

McDougall, T.J., and S.J. Wotherspoon, 2014: A simple modification of
Newtonâ€™s method to achieve convergence of order "1 + sqrt(2)". *Applied
Mathematics Letters*, **29**, 20-25.
http://dx.doi.org/10.1016/j.aml.2013.10.008

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