function [ro]=ro(S,T,r)
% W J Schulz 22 Dec 2009
% Modified by B. Barrett and J. Beattie Jan 2010
% SO 513 Lab 1
%
% Computes the density for sea water at one standard 
% atmospheric pressure, i.e. the ocean surface, per
% Pond and Pickard's "Introductory Dynamical Oceanography", 2nd Ed.
%
% Variables:
%   r = array of coefficients for the density calculation
%   ro = 'rho zero' = density of sea water at surface
%   in kg/m^3
%   input:
%       S= salinity in practical salinity units 
%       T = Temperature in degrees Celsius
%   
%

%calculate the density at the surface
%
ro = r(1) ...
+r(2).*T.^2 + r(3).*T.^4 ...
+r(4).*S + r(5).*S.*T.^2 ...
+r(6).*S.*T.^4 + r(7).*T.*S.^(3/2) ...
+r(8).*S.^2 + r(9).*T ...
+r(10).*T.^3 + r(11).*T.^5 ...
+r(12).*T.*S ...
+r(13).*S.*T.^3+r(14).*S.^(3/2) ...
+r(15).*T.^2.*S.^(3/2);
%end function