# gsw_SA_from_rho

    Absolute Salinity from density
    (48-term equation)

## Contents

- USAGE:
- DESCRIPTION:
- INPUT:
- OUTPUT:
- EXAMPLE:
- AUTHOR:
- VERSION NUMBER:
- REFERENCES:

## USAGE:

    SA = gsw_SA_from_rho(rho,CT,p)

## DESCRIPTION:

    Calculates the Conservative Temperature of maximum density of seawater.
    This function returns the Conservative Temperature at which the density
    of seawater is a maximum, at given Absolute Salinity, SA, and sea
    pressure, p (in dbar).  This function uses the computationally-
    efficient 48-term expression for density in terms of SA, CT and p
    (McDougall et al., 2013)

    Note that the 48-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. (2013).  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".

    Click for a more detailed description of calculating the
    Absolute Salinty from density.

## INPUT:

    rho =  density of a seawater sample (e.g. 1026 kg/m^3)        [ kg/m^3 ]
       Note. This input has not had 1000 kg/m^3 subtracted from it.
         That is, it is 'density', not 'density anomaly'.
    CT  =  Conservative Temperature (ITS-90)                       [ deg C ]
    p   =  sea pressure                                             [ dbar ]
           ( i.e. absolute pressure - 10.1325 dbar )

    rho & CT need to hve the same dimensions.
    p may have dimensions 1x1 or Mx1 or 1xN or MxN, where SA is MxN.

## OUTPUT:

    SA  =  Absolute Salinity                                        [ g/kg ]

## EXAMPLE:

     rho = [1021.8482; 1022.2647; 1024.4207; 1027.7841; 1029.8287; 1031.9916;]
    CT =  [ 28.7856;  28.4329;  22.8103;  10.2600;   6.8863;   4.4036;]
    p =   [     10;      50;     125;     250;     600;    1000;]

    SA = gsw_SA_from_rho(rho,CT,p)

    SA =

      34.711382887931144
      34.891005107845949
      35.025429483046373
      34.846708947660034
      34.736425587999484
      34.732694768360886

## AUTHOR:

    Trevor McDougall & Paul Barker                      [ help@teos-10.org ]

## VERSION NUMBER:

    3.02 (17th November, 2012)

## 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 section 3.42 of this TEOS-10 Manual.

    McDougall T.J., P.M. Barker, R. Feistel and D.R. Jackett, 2013:  A
     computationally efficient 48-term expression for the density of
     seawater in terms of Conservative Temperature, and related properties
     of seawater.  To be submitted to J. Atm. Ocean. Technol., xx, yyy-zzz.

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