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# vrdv2uvG

Computes the wind components via spherical harmonics, given vorticity and divergence on a gaussian grid.

## Prototype

```	function vrdv2uvG (
vr  : numeric,
dv  : numeric
)

return_val [2,dimsizes(vr)] :  float or double
```

## Arguments

vr

vorticity array (input, array with two or more dimensions, last two dimensions must be nlat x nlon)

• input values must be in ascending latitude order
• input array must be on a global grid

dv

divergence array (input, same dimensions as vr)

• values must be in ascending latitude order
• input array must be on a global grid

## Return value

The returned array will be dimensioned 2 x dimsizes (vr), where the 0-th element of the leftmost dimension contains the u component and the 1-th element of the leftmost dimension contains the v component (both in ascending latitude order). The returned array will be of type double if the input is double, and float otherwise.

## Description

vrdv2uvG computes the wind components given the vorticity and divergent arrays vr and dv. vrdv2uvG operates on a gaussian grid.

This function does not handle missing values (defined by the _FillValue attribute). If any missing values are encountered in a particular 2D input grid, then all of the values in the corresponding output grids will be set to the missing value defined by the output grids' _FillValue attributes.

Input arrays should not include the cyclic (wraparound) points when invoking this function, or any procedure or function which uses spherical harmonics (Spherepack).

If the input arrays vr and dv are on a fixed grid, vrdv2uvF should be used. Also, note that vrdv2uvG is the function version of vrdv2uvg.

## Examples

Example 1

Given the wind components u and v (on a gaussian grid), compute the relative vorticity and divergence, and then reconstruct the wind components from the vorticity and divergence fields.

```begin
nlat  = 128                                       ; dimensions
mlon  = 256
mlon1 = mlon+1
fbfile = "uv300.hs"

nrec  = fbinnumrec(fbfile)       ; total number of records in the file
ntim  = nrec/2                       ; number of time steps in dataset

uvmsg = 1e+36

work  = new ( (/nlat,mlon1/), float, uvmsg )
u     = new ( (/nlat,mlon /), float, uvmsg )  ; source u
v     = new ( (/nlat,mlon /), float, uvmsg )  ; source v

do i = 0,nrec-1,2
month = 1                         ; January
if (i .ge. 2) then
month = 7                     ; July
end if

u    = work(:,0:mlon-1)
v    = work(:,0:mlon-1)

vrdvx = uv2vrdvG (u,v)              ; u,v ==> div and vort
uvx   = vrdv2uvG (vrdvx(0,:,:), \   ; vr,dv > reconstruct original wind
vrdvx(1,:,:))
end do
end
```

## Errors

If jer or ker is equal to:

1 : error in the specification of nlat
2 : error in the specification of nlon
4 : error in the specification of N (jer only)