# gsw_SA_from_SP

    Absolute Salinity from Practical Salinity

## Contents

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

## USAGE:

    [SA, in_ocean] = gsw_SA_from_SP(SP,p,long,lat)

## DESCRIPTION:

    Calculates Absolute Salinity from Practical Salinity.  Since SP is
    non-negative by definition, this function changes any negative
    input values of SP to be zero.

    Click for a more detailed description of calculating
    Absolute Salinity from Practical Salinity.

## INPUT:

    SP   =  Practical Salinity  (PSS-78)                        [ unitless ]
    p    =  sea pressure                                            [ dbar ]
            ( ie. absolute pressure - 10.1325 dbar )
    long =  longitude in decimal degrees                      [ 0 ... +360 ]
                                                       or  [ -180 ... +180 ]
    lat  =  latitude in decimal degrees north                [ -90 ... +90 ]

    p, lat & long may have dimensions 1x1 or Mx1 or 1xN or MxN,
    where SP is MxN.

## OUTPUT:

    SA        =  Absolute Salinity                                  [ g/kg ]
    in_ocean  =  0, if long and lat are a long way from the ocean
              =  1, if long and lat are in the ocean
      Note. This flag is only set when the observation is well and truly on
        dry land; often the warning flag is not set until one is several
        hundred kilometres inland from the coast.

## EXAMPLE:

    SP =   [34.5487; 34.7275; 34.8605; 34.6810; 34.5680; 34.5600;]
    p =    [     10;      50;     125;     250;     600;    1000;]
    lat =  [      4;       4;       4;       4;       4;       4;]
    long = [    188;     188;     188;     188;     188;     188;]

    If the profile data refers to one location (one station) is it
    acceptable to enter the station location once.
    (i.e. the following will produce the same result as the input above).

    SP =   [34.5487; 34.7275; 34.8605; 34.6810; 34.5680; 34.5600;]
    p =    [     10;      50;     125;     250;     600;    1000;]
    lat =  4;
    long = 188;

    [SA, in_ocean] = gsw_SA_from_SP(SP,p,long,lat)

    SA =                         in_ocean =

     34.711779712893147              1
     34.891523721622328              1
     35.025547737221643              1
     34.847230081708567              1
     34.736629598766619              1
     34.732361864645107              1

## AUTHOR:

    David Jackett, Trevor McDougall & Paul Barker [ help_gsw@csiro.au ]

## VERSION NUMBER:

    2.0 (23rd July, 2010)

## 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 2.5 and appendices A.4 and A.5 of this TEOS-10 Manual.

    McDougall, T.J., D.R. Jackett and F.J. Millero, 2010: An algorithm
     for estimating Absolute Salinity in the global ocean.  Submitted to
     Ocean Science. A preliminary version is available at Ocean Sci. Discuss.,
     6, 215-242.
     http://www.ocean-sci-discuss.net/6/215/2009/osd-6-215-2009-print.pdf

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