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# uv2vrdvF

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

## Prototype

```	function uv2vrdvF (
u  : numeric,
v  : numeric
)

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

## Arguments

u
v

wind component (input, two or more dimensions, where the rightmost two dimensions must be lat x lon)

• input 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(u), where the 0-th element of the leftmost dimension contains the vorticity and the 1-th element of the leftmost dimension contains the divergence (both in ascending latitude order). The returned array will be of type double if the input is double, and float otherwise.

## Description

uv2vrdvF takes as input u and v and computes the vorticity and divergence. uv2vrdvF operates on a fixed 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 u and v are on a gaussian grid, uv2vrdvG should be used. Also, note that uv2vrdvF is the function version of uv2vrdvf.

Note, if the input arrays are not global or contain missing data, then it is recommended that uv2vr_cfd be used to compute vorticity.

## Examples

Example 1

Compute the vorticity and divergence given u and v on a fixed grid. Also, compute the rotational wind components and the divergent wind components, and finally reconstruct the original wind from the divergence and vorticity fields.

```begin
nlat  =  73                                       ; dimensions
mlon  = 144
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

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 = uv2vrdvF (u,v)             ; u,v ==> div and vort
uvd   = dv2uvF (dv)                ; dv  ==> divergent  wind components
uvr   = vr2uvF (vr)                ; vr  ==> rotational wind components
uuvv  = vrdv2uvF (vr,dv)           ; vr,dv > reconstruct original wind
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)