# gsw_entropy_first_derivatives

**first derivatives of entropy**

## Contents

## USAGE:

[eta_SA, eta_CT] = gsw_entropy_first_derivatives(SA,CT)

## DESCRIPTION:

Calculates the following two partial derivatives of specific entropy (eta)
(1) eta_SA, the derivative with respect to Absolute Salinity at
constant Conservative Temperature, and
(2) eta_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:

eta_SA = The derivative of specific entropy with respect to
Absolute Salinity (in units of g/kg) at constant Conservative
Temperature. The eta_SA output has units of:
[ J/(kg K(g/kg))] or [ J/(g K) ]
eta_CT = The derivative of specific entropy with respect to
Conservative Temperature at constant Absolute Salinity.
The eta_CT output has units of: [ J/(kg K^2) ]

## 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;]

[eta_SA, eta_CT] = gsw_entropy_first_derivatives(SA,CT)

eta_SA =

-0.263286800711655
-0.263977276574528
-0.255367497912925
-0.238066586439561
-0.234438260606436
-0.232820684341694

eta_CT =

13.221031210083824
13.236911191313675
13.489004628681361
14.086599016583795
14.257729576432077
14.386429945649411

## AUTHOR:

Trevor McDougall. [ 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.12.8) and (P.14a, c) of this TEOS-10 Manual.

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