# gsw_pt_first_derivatives

**first derivatives of potential temperature**

## Contents

## USAGE:

[pt_SA, pt_CT] = gsw_pt_first_derivatives(SA,CT)

## DESCRIPTION:

Calculates the following two partial derivatives of potential
temperature (the regular potential temperature whose reference sea
pressure is 0 dbar)
(1) pt_SA, the derivative with respect to Absolute Salinity at
constant Conservative Temperature, and
(2) pt_CT, the derivative with respect to Conservative Temperature at
constant Absolute Salinity.

## INPUT:

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

SA & CT need to have the same dimensions.

## OUTPUT:

pt_SA = The derivative of potential temperature with respect to
Absolute Salinity at constant Conservative Temperature.
[ K/(g/kg)]
pt_CT = The derivative of potential temperature with respect to
Conservative Temperature at constant Absolute Salinity.
pt_CT is dimensionless. [ 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;]

[pt_SA, pt_CT] = gsw_pt_first_derivatives(SA,CT)

pt_SA =

0.041863223165431
0.041452303483011
0.034682095247246
0.018711079068408
0.014079958329844
0.010577326129948

pt_CT =

0.997192967140242
0.997451686508335
0.998357568277750
0.999996224076267
1.000283719083268
1.000525947028218

## 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 Eqns. (A.12.6), (A.12.3), (P.6) and (P.8) of this TEOS-10 Manual.

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