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# depth_to_pres

Convert ocean depth to pressure.

Available in version 6.1.0 and later.

## Prototype

function depth_to_pres (
z       : numeric,
opt [1] : logical
)

return_val  :  numeric

## Arguments

z

Ocean depth (meters)

opt

Options. Currently not used, set to False.

## Return value

The returned array will have units of bars. It will be the same size, shape and type as z.

## Description

Calculate ocean pressure (bars) from user specified depth (meters). The equation used is consistent with that used in the POP model (2012).

This function computes pressure in dekabar from depth in meters using a mean density derived from depth-dependent global average temperatures and salinities from Levitus 1994, and integrating using hydrostatic balance.

References

Levitus, S., R. Burgett, and T.P. Boyer, 1994
World Ocean Atlas
Volume 3: Salinity, NOAA Atlas NESDIS 3, US Dept. of Commerce

Dukowicz, J. K., 2000
Reduction of Pressure and Pressure
Gradient Errors in Ocean Simulations, J. Phys. Oceanogr.,

## Examples

Example 1

d    = (/ 7321.45, 9712.65/)                     ; meters
pd   = depth_to_pres(d,False) ; pd = (/ 749.937, 1000.19/) bars

Example 2

z        = f->z_t            ; cm
z        = z*0.01            ; convert to meters
z@units  = "meters"

pz       = depth_to_pres(z,False)        ; pz(kz); kz=dimsizes(z)
pz@units = "bars"
The output:
z          pz
(0)          5.01      0.498
(1)         15.07      1.500
(2)         25.28      2.519
(3)         35.76      3.568
(4)         46.61      4.656
(5)         57.98      5.797
[snip]
(34)      4125.00    419.486
(35)      4375.00    445.163
(36)      4625.00    470.869
(37)      4875.00    496.602
(38)      5125.00    522.365
(39)      5375.00    548.156