Computation/
div.pro
compute the horizontal divergence of a vectors field located on Arakawa C-grid.
div
Calculation
result = div(uu, vv, DIREC=scalar string, MILLION=scalar: 0 or 1, _EXTRA=_EXTRA)
Return value
the divergence of the input data (with the same size) located at T
point (see restrictions).
Parameters
uu
Matrix representing the zonal coordinates (at U point) of a field of vectors
A 2D (xy), 3D (xyz or yt) or a structure readable by litchamp and containing
a 2D (xy), 3D (xyz or yt) array (4D case is not coded yet).
note that the dimension of the array must suit the domain dimension.
vv
Matrix representing the meridional coordinates (at V point) of a field of vectors
A 2D (xy), 3D (xyz or yt) or a structure readable by litchamp and containing
a 2D (xy), 3D (xyz or yt) array (4D case is not coded yet).
note that the dimension of the array must suit the domain dimension.
Keywords
DIREC
type: scalar string
Use if you want to call moyenne or
grossemoyenne after the div computation
(stupid ?) with a mean done in the DIREC direction
MILLION
type: scalar: 0 or 1
default: 0
Activate to multiply returned array by 1.e6
_EXTRA
Used to declare that this routine accepts inherited keywords
Examples
IDL> @tst_initorca2
IDL> plt, div(dist(jpi,jpj), dist(jpi,jpj))
Version history
Version
$Id: div.pro 378 2008-08-12 12:35:46Z pinsard $
History
Guillaume Roullet (grlod@ipsl.jussieu.fr): creation; spring 1998
Sebastien Masson (smasson@lodyc.jussieu.fr)
adaptation to work with a reduce domain; 12/1/2000
Known issues
Todo items
code the 4D case
Restrictions
- Works only for Arakawa C-grid.
- UU must be on U grid, VV must be on V grid
- 4D case is not coded yet
- the common variable jpt is used to differ xyz (jpt=1) and xyt (jpt=1) cases.
- U and V arrays are cut in the same geographic domain. Because of the shift between
T, U, V and F grids, it is possible that these two arrays do not have the same
size and refer to different indexes. In this case, arrays are re-cut on
common indexes. To avoid these re-cuts, use the keyword /memeindice in
domdef
- When computing the divergence, we update, vargrid, varname, varunits and the
grid position parameters (firstxt, lastxt, nxt, firstyt, lastyt, nyt).
- points that cannot be computed (domain boundaries, coastline) are set to NaN
Other attributes
Uses routines
cm_4cal
cm_4data
cm_4mesh
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