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gsw_SA_from_SP.m
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function [SA, in_ocean] = gsw_SA_from_SP(SP,p,long,lat)
% 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.
%
% INPUT:
% SP = Practical Salinity (PSS-78) [ unitless ]
% p = sea pressure [ dbar ]
% ( i.e. 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.
%
% AUTHOR:
% David Jackett, Trevor McDougall & Paul Barker [ [email protected] ]
%
% VERSION NUMBER: 3.05 (27th January 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 http://www.TEOS-10.org
% 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
%
%==========================================================================
%--------------------------------------------------------------------------
% Check variables and resize if necessary
%--------------------------------------------------------------------------
if ~(nargin==4)
error('gsw_SA_from_SP: Requires four inputs')
end %if
[ms,ns] = size(SP);
[mp,np] = size(p);
if (mp == 1) & (np == 1) % p is a scalar - fill to size of SP
p = p*ones(size(SP));
elseif (ns == np) & (mp == 1) % p is row vector,
p = p(ones(1,ms), :); % copy down each column.
elseif (ms == mp) & (np == 1) % p is column vector,
p = p(:,ones(1,ns)); % copy across each row.
elseif (ns == mp) & (np == 1) % p is a transposed row vector,
p = p.'; % transposed then
p = p(ones(1,ms), :); % copy down each column.
elseif (ms == mp) & (ns == np)
% ok
else
error('gsw_SA_from_SP: Inputs array dimensions arguments do not agree')
end %if
[mla,nla] = size(lat);
if (mla == 1) & (nla == 1) % lat is a scalar - fill to size of SP
lat = lat*ones(size(SP));
elseif (ns == nla) & (mla == 1) % lat is a row vector,
lat = lat(ones(1,ms), :); % copy down each column.
elseif (ms == mla) & (nla == 1) % lat is a column vector,
lat = lat(:,ones(1,ns)); % copy across each row.
elseif (ns == mla) & (nla == 1) % lat is a transposed row vector,
lat = lat.'; % transposed then
lat = lat(ones(1,ms), :); % copy down each column.
elseif (ms == mla) & (ns == nla)
% ok
else
error('gsw_SA_from_SP: Inputs array dimensions arguments do not agree')
end %if
[mlo,nlo] = size(long);
long(long < 0) = long(long < 0) + 360;
if (mlo == 1) & (nlo == 1) % long is a scalar - fill to size of SP
long = long*ones(size(SP));
elseif (ns == nlo) & (mlo == 1) % long is a row vector,
long = long(ones(1,ms), :); % copy down each column.
elseif (ms == mlo) & (nlo == 1) % long is a column vector,
long = long(:,ones(1,ns)); % copy across each row.
elseif (ns == mlo) & (nlo == 1) % long is a transposed row vector,
long = long.'; % transposed then
long = long(ones(1,ms), :); % copy down each column.
elseif (ms == nlo) & (mlo == 1) % long is a transposed column vector,
long = long.'; % transposed then
long = long(:,ones(1,ns)); % copy down each column.
elseif (ms == mlo) & (ns == nlo)
% ok
else
error('gsw_SA_from_SP: Inputs array dimensions arguments do not agree')
end %if
if ms == 1
SP = SP.';
p = p.';
lat = lat.';
long = long.';
transposed = 1;
else
transposed = 0;
end
% remove out of range values.
SP(p < 100 & SP > 120) = NaN;
SP(p >= 100 & SP > 42) = NaN;
% change standard blank fill values to NaN's.
SP(abs(SP) == 99999 | abs(SP) == 999999) = NaN;
p(abs(p) == 99999 | abs(p) == 999999) = NaN;
long(abs(long) == 9999 | abs(long) == 99999) = NaN;
lat(abs(lat) == 9999 | abs(lat) == 99999) = NaN;
if any(p < -1.5 | p > 12000)
error('gsw_SA_from_SP: pressure is out of range')
end
if any(long < 0 | long > 360)
error('gsw_SA_from_SP: longitude is out of range')
end
if any(abs(lat) > 90)
error('gsw_SA_from_SP: latitude is out of range')
end
%--------------------------------------------------------------------------
% Start of the calculation
%--------------------------------------------------------------------------
% This ensures that SP is non-negative.
SP(SP < 0) = 0;
[Iocean] = find(~isnan(SP + p + lat + long));
SA = nan(size(SP));
SAAR = SA;
in_ocean = SA;
% The following function (gsw_SAAR) finds SAAR in the non-Baltic parts of
% the world ocean. (Actually, this gsw_SAAR look-up table returns values
% of zero in the Baltic Sea since SAAR in the Baltic is a function of SP,
% not space.
[SAAR(Iocean), in_ocean(Iocean)] = gsw_SAAR(p(Iocean),long(Iocean),lat(Iocean));
SA(Iocean) = gsw_uPS*SP(Iocean).*(1 + SAAR(Iocean));
% Here the Practical Salinity in the Baltic is used to calculate the
% Absolute Salinity there.
SA_baltic(Iocean) = gsw_SA_from_SP_Baltic(SP(Iocean),long(Iocean),lat(Iocean));
if any(~isnan(SA_baltic(Iocean)))
[Ibaltic] = find(~isnan(SA_baltic(Iocean)));
SA(Iocean(Ibaltic)) = SA_baltic(Iocean(Ibaltic));
end
if transposed
SA = SA';
in_ocean = in_ocean';
end
end