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


	function uv2vrdvG (
		u  : numeric,  
		v  : numeric   

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



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.


uv2vrdvG takes as input u and v and computes the vorticity and divergence. uv2vrdvG 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 u and v are on a fixed grid, uv2vrdvF should be used. Also, note that uv2vrdvG is the function version of uv2vrdvg.

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

See Also

uv2vrdvg, uv2vrdvF, uv2vrdvf, uv2vr_cfd, uv2vrG, uv2vrg, uv2vrF, uv2vrf, vr2uvG, dv2uvG, vrdv2uvG, uv2sfvpG


Example 1

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

  nlat  =  64                                       ; dimensions
  mlon  = 128
  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   

   work = fbinrecread(fbfile,i  ,(/nlat,mlon1/),"float")
   u    = work(:,0:mlon-1)
   work = fbinrecread(fbfile,i+1,(/nlat,mlon1/),"float")
   v    = work(:,0:mlon-1)

   vrdvx = uv2vrdvG (u,v)             ; u,v ==> div and vort 
   uvd   = dv2uvG (dv)                ; dv  ==> divergent  wind components
   uvr   = vr2uvG (vr)                ; vr  ==> rotational wind components
   uuvv  = vrdv2uvG (vr,dv)           ; vr,dv > reconstruct original wind
  end do


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)