pressure2depth

 Depth   Computes depth given the pressure at some latitude
         Z=Depth(P,LAT) gives the Depth Z (m) for a pressure P
             (dbars) at some latitude LAT (degrees).

         Fofonoff and Millard (1982). UNESCO Tech Paper #44.

 Notes:  (ETP3, MBARI)
         This algorithm was originally compiled by RP @ WHOI.
         It was copied from the UNESCO technical report.
         The algorithm was endorsed by SCOR Working Group 51.
         The equations were originally developed by Saunders
             and Fofonoff (1976).  DSR 23: 109-111.
         The parameters were re-fit for the 1980 equation of
             state for seawater (EOS80).

 CHECKVALUE: Z = 9712.653 M FOR P=10000 DECIBARS, LAT=30 DEG

 CALCULATON ASSUMES STD OCEAN: T = 0 DEG C; S = 35 (IPSS-78)

0001 function Z=Depth(P,LAT)
0002 % Depth   Computes depth given the pressure at some latitude
0003 %         Z=Depth(P,LAT) gives the Depth Z (m) for a pressure P
0004 %             (dbars) at some latitude LAT (degrees).
0005 %
0006 %         Fofonoff and Millard (1982). UNESCO Tech Paper #44.
0007 %
0008 % Notes:  (ETP3, MBARI)
0009 %         This algorithm was originally compiled by RP @ WHOI.
0010 %         It was copied from the UNESCO technical report.
0011 %         The algorithm was endorsed by SCOR Working Group 51.
0012 %         The equations were originally developed by Saunders
0013 %             and Fofonoff (1976).  DSR 23: 109-111.
0014 %         The parameters were re-fit for the 1980 equation of
0015 %             state for seawater (EOS80).
0016 %
0017 % CHECKVALUE: Z = 9712.653 M FOR P=10000 DECIBARS, LAT=30 DEG
0018 %
0019 % CALCULATON ASSUMES STD OCEAN: T = 0 DEG C; S = 35 (IPSS-78)
0020 
0021 
0022   X = sin(LAT/57.29578);
0023   X = X.*X;
0024 
0025 % GR= GRAVITY VARIATION WITH LAT: ANON (1970) BULLETIN GEODESIQUE
0026 
0027   GR = 9.780318*(1.0+(5.2788E-3+2.36E-5*X).*X) + 1.092E-6.*P;
0028 
0029   Z = (((-1.82E-15*P+2.279E-10).*P-2.2512E-5).*P+9.72659).*P;
0030   Z = Z./GR;