% densatp.m by: Edward T Peltzer, MBARI % revised: 29 Jan 98. % % CALCULATE THE DENSITY OF SEAWATER AT A GIVEN S, T and P. % Equation of State is from Millero & Poisson (1981) DSR V28: 625-629. % % INPUT: Salinity (S) in g/kg or pss. % Temperature (T) in degrees C. % Pressure (P) in decibar. % % OUTPUT: Density [rhp] in g/cc: % % rhp = densatp(S,T,P). function [rhp]=densatp(S,T,P) % DEFINE CONSTANTS FOR EQUATION OF STATE R0=+9.99842594E2; R1=+6.793952E-2; R2=-9.095290E-3; R3=+1.001685E-4; R4=-1.120083E-6; R5=+6.536332E-9; A0=+8.24493E-1; A1=-4.0899E-3; A2=+7.6438E-5; A3=-8.2467E-7; A4=+5.3875E-9; B0=-5.72466E-3; B1=+1.0227E-4; B2=-1.6546E-6; C=+4.8314E-4; % CALCULATE RHO SR=sqrt(S); RHO0=R0+T.*(R1+T.*(R2+T.*(R3+T.*(R4+T.*R5)))); A=A0+T.*(A1+T.*(A2+T.*(A3+T.*A4))); B=B0+T.*(B1+T.*B2); RHO=RHO0+S.*(A+B.*SR+C.*S); % DEFINE CONSTANTS FOR SECANT BULK MODULUS D0=+1.965221E+4; D1=+1.484206E+2; D2=-2.327105E+0; D3=+1.360477E-2; D4=-5.155288E-5; E0=+5.46746E+1; E1=-6.03459E-1; E2=+1.09987E-2; E3=-6.1670E-5; F0=+7.944E-2; F1=+1.6483E-2; F2=-5.3009E-4; G0=+3.239908E+0; G1=+1.43713E-3; G2=+1.16092E-4; G3=-5.77905E-7; H0=+2.2838E-3; H1=-1.0981E-5; H2=-1.6078E-6; H3=+1.91075E-4; I0=+8.50935E-5; I1=-6.12293E-6; I2=+5.2787E-8; J0=-9.9348E-7; J1=+2.0816E-8; J2=+9.1697E-10; % CORRECT P IN DECI-BARS TO BARS Pc=P./10.; % CALCULATE K H=H0+T.*(H1+T.*H2)+H3.*SR; J=J0+T.*(J1+T.*J2); K1=D0+T.*(D1+T.*(D2+T.*(D3+T.*D4))); K2=E0+T.*(E1+T.*(E2+T.*E3)); K3=F0+T.*(F1+T.*F2); K4=G0+T.*(G1+T.*(G2+T.*G3))+S.*H; K5=I0+T.*(I1+T.*I2)+S.*J; K=K1+S.*(K2+SR.*K3)+Pc.*(K4+Pc.*K5); % CORRECT FOR PRESSURE RHP=RHO.*(1./(1-Pc./K)); % CONVERT KG/M3 TO g/cc rhp = RHP ./ 1000;