gsw_z_from_p

height from pressure (75-term equation)

Contents

USAGE:

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

DESCRIPTION:

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)
Note. Height z is NEGATIVE in the ocean. ie. 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". 
TEOS-10
Click for a more detailed description of calculating
height from pressure.

INPUT:

p    =  sea pressure                                            [ dbar ]
        ( ie. absolute pressure - 10.1325 dbar )
lat  =  latitude in decimal degrees north                [ -90 ... +90 ]
OPTIONAL:
geo_strf_dyn_height = dynamic height                          [ m2/s^2 ]
sea_surface_geopotental = geopotential at zero sea pressure  [ m^2/s^2 ]
lat may have dimensions 1x1 or Mx1 or 1xN or MxN, where p is MxN.
geo_strf_dyn_height and geo_strf_dyn_height, if provided, must have 
dimensions MxN, which are the same as p.

OUTPUT:

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.

EXAMPLE:

p =  [   10;   50;  125;  250;  600; 1000;]
lat = 4;
z = gsw_z_from_p(p,lat)
z =
  1.0e+002 *
  -0.099445834469453
  -0.497180897012550
  -1.242726219409978
  -2.484700576548589
  -5.958253480356214
  -9.920919060719987

AUTHOR:

Trevor McDougall, Claire Roberts-Thomson & Paul Barker.
                                                   [ help@teos-10.org ]

VERSION NUMBER:

3.05 (16th February, 2015)

REFERENCES:

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 http://www.TEOS-10.org