plots Absolute Salinity - Conservative Temperature
profiles on a SA-CT diagram including freezing line and
selected potential density contours.(75-term equation)





Produces a plot of Absolute Salinity - Conservative Temperature
profiles.  The diagram also plots the Conservative Temperature freezing 
point for p = 0 dbar assuming the seawater is completely saturated with
dissolved air and user defined potential density contours.  This 
function uses the computationally-efficient 75-term expression for 
specific volume in terms of SA, CT and p (Roquet et al.,2015). 
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". 


SA    =  Absolute Salinity                                     [ g/kg ]
CT    =  Conservative Temperature                             [ deg C ]
p     =  sea pressure                                          [ dbar ]
         ( i.e. absolute pressure - 10.1325 dbar )


p_ref = reference sea pressure for the isopycnals [ dbar ] (i.e. absolute reference pressure - 10.1325 dbar) If it is not suppled a default of 0 dbar is used. isopycs = isopycnals, can be either an array of isopynals or the number of isopynals to appear on the plot. If it is not supplied the programme defaults to 5 isopynals. title_string = title text to appear at the top of the plot.
SA & CT need to have the same dimensions.
p_ref should be a scalar, (i.e. have dimensions 1x1).
isopycs can be either 1x1 or 1xN or Mx1


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;]
p =  [     10;      50;     125;     250;     600;    1000;]
p_ref = 1000
isopycs = [24:0.5:33];
gsw_SA_CT_plot(SA,CT,p_ref,isopycs,'\it{S}\rm_A - {\Theta} diagram')


Rich Pawlowicz                                 [ ]
Note. This function was extracted and adapted from Rich Pawlowicz's 
 ocean toolbox.
Paul Barker & Trevor McDougall


3.05 (21st May, 2015)


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.
This software is available from