Computation/
div.pro
compute the horizontal divergence of a vectors field
div
Calculation
result = div(uu, vv, DIREC=scalar string)
Return value
RES
the divergence of the input data (with the same size)
Parameters
uu
Matrix representing the zonal coordinates (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 arry must suit the domain dimension.
vv
Matrix representing the meridional coordinates (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 arry 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
Examples
IDL> @tst_initorca2
IDL> plt, div(dist(jpi,jpj), dist(jpi,jpj))
Version history
Version
$Id: div.pro 168 2006-09-06 10:46:29Z 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.pro
- 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 bondaries, coastline) are set to NaN
Other attributes
Uses routines
cm_4cal, cm_4data, cm_4mmesh
Produced by IDLdoc 2.0 on Wed Sep 13 16:32:08 2006.