Contents
USAGE:
SA_out = gsw_stabilise_SA_const_t(SA_in,t,p,{opt_1,opt_2})
DESCRIPTION:
This function stabilises a water column. This is achieved by minimally
adjusting only the Absolute Salinity SA values such that the minimum
stability is made to be within at least 1 x 10^-9 s^-2 of the desired
minimum Nsquared min_Nsquared, the default value is which is about 1/5th
of the square of earth's rotation rate. There are no changes made to
either in-situ temperature or pressure.
This programme requires either Tomlab CPLEX or IBM CPLEX or the
Optimization toolbox. Note that if there are a up to several hundred
data points in the cast then Matlab's Optimization toolbox produces
reasonable results, but if there are thousands of bottles in the cast or
the best possible output is wanted then the CPLEX solver is required.
This programme will determine if a slover is available to the user, if
there is more than one it will use first in the following order Tomlab,
IBM, then Matlab.
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_in = uncorrected Absolute Salinity [ g kg-1 ]
t = in-situ temperature (ITS-90) [ deg C ]
p = sea pressure [ dbar ]
(i.e. absolute pressure - 10.1325 dbar)
OPTIONAL:
opt_1 = Nsquared_lowerlimit [ s-2 ]
Note. If Nsquared_lowerlimit is not supplied, a default minimum
stability of 1 x 10^-9 s^-2 will be applied.
or,
opt_1 = longitude in decimal degrees [ 0 ... +360 ]
or [ -180 ... +180 ]
opt_2 = latitude in decimal degrees north [ -90 ... +90 ]
SA & t need to have the same dimensions.
p may have dimensions 1x1 or Mx1 or 1xN or MxN, where SA & t are MxN.
opt_1 equal to Nsquared_lowerlimit, if provided, may have dimensions 1x1
or (M-1)x1 or 1xN or (M-1)xN, where SA_in & t are MxN.
opt_1 equal to long & opt_2 equal to lat, if provided, may have
Sdimensions 1x1 or (M-1)x1 or 1xN or (M-1)xN, where SA_in & t are MxN.
OUTPUT:
SA_out = corrected stabilised Absolute Salinity [ g kg-1 ]
EXAMPLE (using Tomlab CPLEX):
SA = [34.7118; 34.8915; 35.0256; 31.0472; 34.7366; 34.7324;]
t = [28.7856; 28.4329; 22.8103; 10.2600; 6.8863; 4.4036;]
p = [ 10; 50; 125; 250; 600; 1000;]
SA_out = gsw_stabilise_SA_const_t(SA,t,p)
SA_out =
34.7118
34.8915
34.4080
31.6648
34.7366
34.7324
AUTHOR:
Paul Barker and Trevor McDougall [ help@teos-10.org ]
VERSION NUMBER:
3.06.12 (15th June, 2020)
REFERENCES:
Barker, P.M., and T.J. McDougall, 2017: Stabilizing hydrographic
profiles with minimal change to the water masses.
J. Atmosph. Ocean. Tech., 34, pp. 1935 - 1945.
http://dx.doi.org/10.1175/JTECH-D-16-0111.1
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.
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 and P.M. Barker, 2015: Accurate
polynomial expressions for the density and specific volume of seawater
using the TEOS-10 standard. Ocean Modelling, 90, pp. 29-43.
http://dx.doi.org/10.1016/j.ocemod.2015.04.002
The software is available from http://www.TEOS-10.org
