densatp

 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).

0001 % densatp.m                                      by:  Edward T Peltzer, MBARI
0002 %                                                  revised:  29 Jan 98.
0003 %
0004 % CALCULATE THE DENSITY OF SEAWATER AT A GIVEN S, T and P.
0005 % Equation of State is from Millero & Poisson (1981) DSR V28: 625-629.
0006 %
0007 % INPUT:           Salinity (S) in g/kg or pss.
0008 %        Temperature (T) in degrees C.
0009 %        Pressure (P) in decibar.
0010 %
0011 % OUTPUT:    Density [rhp] in g/cc:
0012 %
0013 %            rhp = densatp(S,T,P).
0014 
0015 function [rhp]=densatp(S,T,P)
0016 
0017 % DEFINE CONSTANTS FOR EQUATION OF STATE
0018 
0019   R0=+9.99842594E2;
0020   R1=+6.793952E-2;
0021   R2=-9.095290E-3;
0022   R3=+1.001685E-4;
0023   R4=-1.120083E-6;
0024   R5=+6.536332E-9;
0025 
0026   A0=+8.24493E-1;
0027   A1=-4.0899E-3;
0028   A2=+7.6438E-5;
0029   A3=-8.2467E-7;
0030   A4=+5.3875E-9;
0031 
0032   B0=-5.72466E-3;
0033   B1=+1.0227E-4;
0034   B2=-1.6546E-6;
0035 
0036   C=+4.8314E-4;
0037 
0038 % CALCULATE RHO
0039 
0040     SR=sqrt(S);
0041 
0042     RHO0=R0+T.*(R1+T.*(R2+T.*(R3+T.*(R4+T.*R5))));
0043     A=A0+T.*(A1+T.*(A2+T.*(A3+T.*A4)));
0044     B=B0+T.*(B1+T.*B2);
0045 
0046     RHO=RHO0+S.*(A+B.*SR+C.*S);
0047 
0048 % DEFINE CONSTANTS FOR SECANT BULK MODULUS
0049 
0050   D0=+1.965221E+4;
0051   D1=+1.484206E+2;
0052   D2=-2.327105E+0;
0053   D3=+1.360477E-2;
0054   D4=-5.155288E-5;
0055 
0056   E0=+5.46746E+1;
0057   E1=-6.03459E-1;
0058   E2=+1.09987E-2;
0059   E3=-6.1670E-5;
0060 
0061   F0=+7.944E-2;
0062   F1=+1.6483E-2;
0063   F2=-5.3009E-4;
0064 
0065   G0=+3.239908E+0;
0066   G1=+1.43713E-3;
0067   G2=+1.16092E-4;
0068   G3=-5.77905E-7;
0069 
0070   H0=+2.2838E-3;
0071   H1=-1.0981E-5;
0072   H2=-1.6078E-6;
0073   H3=+1.91075E-4;
0074 
0075   I0=+8.50935E-5;
0076   I1=-6.12293E-6;
0077   I2=+5.2787E-8;
0078 
0079   J0=-9.9348E-7;
0080   J1=+2.0816E-8;
0081   J2=+9.1697E-10;
0082 
0083 % CORRECT P IN DECI-BARS TO BARS
0084 
0085     Pc=P./10.;
0086 
0087 % CALCULATE K
0088 
0089     H=H0+T.*(H1+T.*H2)+H3.*SR;
0090     J=J0+T.*(J1+T.*J2);
0091 
0092     K1=D0+T.*(D1+T.*(D2+T.*(D3+T.*D4)));
0093     K2=E0+T.*(E1+T.*(E2+T.*E3));
0094     K3=F0+T.*(F1+T.*F2);
0095     K4=G0+T.*(G1+T.*(G2+T.*G3))+S.*H;
0096     K5=I0+T.*(I1+T.*I2)+S.*J;
0097 
0098     K=K1+S.*(K2+SR.*K3)+Pc.*(K4+Pc.*K5);
0099 
0100 % CORRECT FOR PRESSURE
0101 
0102     RHP=RHO.*(1./(1-Pc./K));
0103 
0104 % CONVERT KG/M3 TO g/cc
0105 
0106     rhp = RHP ./ 1000;