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uv2sfvpg

Computes the stream function and velocity potential via spherical harmonics given u and v on a gaussian grid.

Prototype

	procedure uv2sfvpg (
		u   : numeric,          
		v   : numeric,          
		sf  : float or double,  
		vp  : float or double   
	)

Arguments

u
v

wind components (input, arrays with two or more dimensions, rightmost two dimensions must be nlat x nlon)

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

stream function (output, same dimensions as u and v, values will be in ascending latitude order)

velocity potential (output, same dimensions as u and v, values will be in ascending latitude order)

Description

Given wind components u and v, uv2sfvpg computes the stream function and the velocity potential and returns the results in the arrays sf and vp. uv2sfvpg 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.

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 fixed grid, uv2sfvpf should be used. Also, note that uv2sfvpg is the procedural version of uv2sfvpG.

Examples

Example 1

Compute the stream function and velocity potential, given the u and v wind components on a gaussian grid.

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

  sf    = new ( (/nlat,mlon /), float, uvmsg )  ; stream function
  vp    = new ( (/nlat,mlon /), float, uvmsg )  ; velocity potential

  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)

   uv2sfvpg (u,v, sf,vp)             ; u,v ==> stream function + velocity pot
  end do
end

Errors

If jer or ker is equal to: