# gsw_SA_from_SP

`Absolute Salinity from Practical Salinity`

## 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 =`
```  34.711778344814114              1
34.891522618230098              1
35.025544862476920              1
34.847229026189588              1
34.736628474576051              1
34.732363065590846              1```

## AUTHOR:

`Trevor McDougall, Paul Barker & David Jackett      [ 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 section 2.5 and appendices A.4 and A.5 of this TEOS-10 Manual.```
```McDougall, T.J., D.R. Jackett, F.J. Millero, R. Pawlowicz and
P.M. Barker, 2012: A global algorithm for estimating Absolute Salinity.
Ocean Science, 8, 1123-1134.
http://www.ocean-sci.net/8/1123/2012/os-8-1123-2012.pdf```
`The software is available from http://www.TEOS-10.org`