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vr2uvg

Computes the rotational wind components via spherical harmonics, given an array containing relative vorticity on a gaussian grid.

Prototype

	procedure vr2uvg (
		vor  : numeric,  
		ur   : float,    ; or double
		vr   : float     ; or double
	)

Arguments

vor

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
array must be on a global grid

ur
vr

non-divergent wind components (output, same dimensions as vor, values will be in ascending latitude order)

Description

vr2uvg computes the rotational wind components given an array, vor, containing relative vorticity. The results are stored in the arrays ur and vr. vr2uvg operates on a gaussian grid.

This procedure 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 procedure, or any procedure or function which uses spherical harmonics (Spherepack).

If the input array vr is on a fixed grid, vr2uvf should be used. Also, note that vr2uvg is the procedural version of vr2uvG.

Examples

Example 1

Compute relative vorticity from the wind component arrays u and v (on a gaussian grid), and then compute the rotational wind components.

begin
  nlat  = 128                                       ; dimensions
  mlon  = 256
  mlon1 = mlon+1
  fbfile = "uv300.hs"
                                       ; Generic Workstation setup 
  nrec  = fbinnumrec(fbfile)           ; total number of records in the file
  ntim  = nrec/2                       ; number of time steps in dataset

  uvmsg = 1e+20
  vort  = new ( (/nlat,mlon /), float, uvmsg )  ; vorticity  (relative)
  ur    = new ( (/nlat,mlon /), float, uvmsg )
  vr    = new ( (/nlat,mlon /), float, uvmsg )

  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)

   uv2vrg   (u,v,vort)               ; u,v ==> vorticity (rel)
   vr2uvg   (vort,ur,vr)             ; ur,vr > rotational wind components
  end do
end

Errors

If jer or ker is equal to: