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uv2vrF_Wrap

Computes the vorticity via spherical harmonics, given the u and v wind components on a fixed grid (retains metadata).

Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"

	function uv2vrF_Wrap (
		u  : numeric,  
		v  : numeric   
	)

	return_val [dimsizes(u)] :  float or double

Arguments

u
v

wind components (input, arrays 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

Return value

A double array is returned if u or v are double; a float array is returned otherwise. The returned array will be of dimension size dimsizes (u).

Description

Given wind components u and v, uv2vrF_Wrap computes the vorticity and returns it as an array with the same dimensions as u and v (values will be in ascending latitude order). uv2vrF_Wrap operates on a fixed grid. This function is identical to the built-in function uv2vrF, except it retains metadata.

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 default missing value appropriate to the type of the output.

Note: For the arrays whose last two dimensions are nlat x nlon, the rest of the dimensions (if any) are collectively referred to as N. If the input/output arrays are just two dimensions, then N can either be considered equal to 1 or nothing at all.

Arrays which have dimensions N x nlat x nlon should not include the cyclic (wraparound) points when invoking the procedures and functions which use spherical harmonics (Spherepack).

If the input arrays u and v are on a gaussian grid, uv2vrG_Wrap should be used.

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

Examples

Example 1

Compute the vorticity given u and v on a fixed grid. Also, compute the rotational wind components.

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   

   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)

   vr    = uv2vrF_Wrap (u,v)               ; u,v ==> vorticity (rel)
   uvr   = vr2uvF_Wrap (vr)                ; vr  ==> rotational wind components
  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)