pressure from height (75-term equation)



p = gsw_p_from_z(z,lat,{geo_strf_dyn_height},{sea_surface_geopotental})


Calculates sea pressure from height using computationally-efficient 
75-term expression for specific volume (Roquet et al., 2015).  Dynamic
height anomaly, geo_strf_dyn_height, if provided, must be computed with
its p_ref = 0 (the surface). Also if provided, sea_surface_geopotental 
is the geopotential at zero sea pressure. This function solves 
Eqn.(3.32.3) of IOC et al. (2010) iteratively for p.
Note. Height (z) is NEGATIVE in the ocean.  Depth is -z.  
      Depth is not used in the GSW computer software library. 
Note that the 75-term equation has been fitted in a restricted range of 
parameter space, and is most accurate inside the "oceanographic funnel" 
described in  McDougall et al. (2003).  The GSW library function 
"gsw_infunnel(SA,CT,p)" is avaialble to be used if one wants to test if 
some of one's data lies outside this "funnel". 
Click for a more detailed description of calculating
pressure from height.


z   =  height                                                      [ m ]
 Note. At sea level z = 0, and since z (HEIGHT) is defined
   to be positive upwards, it follows that while z is
   positive in the atmosphere, it is NEGATIVE in the ocean.
lat =  latitude in decimal degrees north                 [ -90 ... +90 ]
geo_strf_dyn_height = dynamic height anomaly                 [ m^2/s^2 ]
  Note that the reference pressure, p_ref, of geo_strf_dyn_height must
   be zero (0) dbar.
lat may have dimensions 1x1 or Mx1 or 1xN or MxN, where z is MxN.
geo_strf_dyn_height and geo_strf_dyn_height, if provided, must have 
dimensions MxN, which are the same as z.


 p  =  sea pressure                                             [ dbar ]
       ( i.e. absolute pressure - 10.1325 dbar )


z   =  [    -10;     -50;    -125;    -250;    -600;   -1000;]
lat = 4;
p = gsw_p_from_z(z,lat)
p =
 1.0e+003 *


Trevor McDougall, Claire Roberts-Thomson and Paul Barker.
                                                [ ]


3.05 (16th February, 2015)


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 the TEOS-10 web site.
McDougall, T.J., D.R. Jackett, D.G. Wright and R. Feistel, 2003: 
 Accurate and computationally efficient algorithms for potential 
 temperature and density of seawater.  J. Atmosph. Ocean. Tech., 20,
 pp. 730-741.
Moritz, 2000: Goedetic reference system 1980. J. Geodesy, 74, 128-133.
Roquet, F., G. Madec, T.J. McDougall, P.M. Barker, 2015: Accurate
 polynomial expressions for the density and specifc volume of seawater
 using the TEOS-10 standard. Ocean Modelling.
Saunders, P. M., 1981: Practical conversion of pressure to depth.
 Journal of Physical Oceanography, 11, 573-574.
This software is available from