Contents
USAGE:
[h_SA, h_CT, h_P] = gsw_enthalpy_first_derivatives(SA,CT,p)
DESCRIPTION:
Calculates the following three derivatives of specific enthalpy (h),
of seawater using the computationally-efficient 75-term expression
for specific volume in terms of SA, CT and p (Roquet et al., 2015).
(1) h_SA, the derivative with respect to Absolute Salinity at
constant CT and p, and
(2) h_CT, derivative with respect to CT at constant SA and p.
(3) h_P, derivative with respect to pressure (in Pa) at constant
SA and CT.
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:
h_SA = The first derivative of specific enthalpy with respect to
Absolute Salinity at constant CT and p.
[ J/(kg (g/kg))] i.e. [ J/g ]
h_CT = The first derivative of specific enthalpy with respect to
CT at constant SA and p. [ J/(kg K) ]
h_P = The first partial derivative of specific enthalpy with
respect to pressure (in Pa) at fixed SA and CT. Note that
h_P is specific volume (1/rho). [ m^3/kg ]
EXAMPLE:
SA = [34.7118; 34.8915; 35.0256; 34.8472; 34.7366; 34.7324;]
CT = [28.7856; 28.4329; 22.8103; 10.2600; 6.8863; 4.4036;]
p = [ 10; 50; 125; 250; 600; 1000;]
[h_SA, h_CT] = gsw_enthalpy_first_derivatives(SA,CT,p)
h_SA =
-0.070175858133742
-0.350930227941697
-0.886796332314973
-1.829592995957160
-4.423460664577400
-7.405099527558439
h_CT =
1.0e+003 *
3.991899705530481
3.992025640520101
3.992210365030743
3.992284150250490
3.992685389122658
3.993014168534175
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.11.18), (A.11.15) and (A.11.12) 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