# gsw_p_from_z

    pressure from height (48-term equation)

## Contents

- USAGE:
- DESCRIPTION:
- INPUT:
- OUTPUT:
- EXAMPLE:
- AUTHOR:
- VERSION NUMBER:
- REFERENCES:

## USAGE:

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

## DESCRIPTION:

    Calculates sea pressure from height using computationally-efficient
    48-term expression for density, in terms of SA, CT and p (McDougall et
    al., 2011).  Dynamic height anomaly, geo_strf_dyn_height, if provided,
    must be computed with its p_ref = 0 (the surface).

    Note. Height (z) is NEGATIVE in the ocean.  Depth is -z.
          Depth is not used in the GSW computer software library.

    Note that the 48-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. (2011).  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.

## INPUT:

    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 ]

    OPTIONAL:
    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, if provided, must have dimensions MxN, which is
    the same as z.

## OUTPUT:

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

## EXAMPLE:

    z   =  [     10;      50;     125;     250;     600;    1000;]
    lat = 4;

    p = gsw_p_from_z(z,lat)

    p =
     1.0e+003 *

      -0.010055235976847
      -0.050271267635044
      -0.125655128514602
      -0.251233371685054
      -0.602442093622451
      -1.003079508920876

## AUTHOR:

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

## VERSION NUMBER:

    3.01 (26th August, 2010)

## 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, P. M. Barker, C. Roberts-Thomson, R.
     Feistel and R. W. Hallberg, 2010:  A computationally efficient 25-term
     expression for the density of seawater in terms of Conservative
     Temperature, and related properties of seawater.  To be submitted
     to Ocean Science Discussions.

    Saunders, P. M., 1981: Practical conversion of pressure to depth.
     Journal of Physical Oceanography, 11, 573-574.

    Moritz (2000) Goedetic reference system 1980. J. Geodesy, 74, 128-133.

    This software is available from http://www.TEOS-10.org