uv2dvG

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

Prototype

	function uv2dvG (
		u  : numeric,  
		v  : numeric   
	)

	return_val [dimsizes(u)] :  float or double

Arguments

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

Return value

This function returns a double array if u or v are double; a float array otherwise. Divergence is returned in an array dimensioned dimsizes(u).

Description

Given wind components u and v, uv2dvG computes the divergence. This function operates on a gaussian grid.

This function does not allow for missing data (defined by the _FillValue attribute) to be present. If any missing values are encountered in a particular 2D input grid, then all of the values in the corresponding output grid will be set to the default missing value appropriate to the type of the output.

Note, if the input arrays are not global or contain missing data, then it is recommended that uv2dv_cfd be used.

Note: For the arrays whose rightmost 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, uv2dvF should be used. Also, note that uv2dvG is the function version of uv2dvg.

Use the uv2dvG_Wrap function if metadata retention is desired. The interface is identical.

See Also

uv2dvG_Wrap, uv2dvF, uv2dvg, uv2dvf, uv2dv_cfd, dv2uvG

Examples

Example 1

Calculate the divergence from the wind components u,v, and then calculate the divergent wind components. u and v are on a gaussian grid.

begin
   a = addfile("/cgd/cas/shea/MURPHYS/ATMOS/80.nc","r")
   u = a->U(:,0,:,:)
   v = a->V(:,0,:,:)
   dv    = uv2dvG (u,v)               ; u,v ==> divergence

   ; Use uv2dvG_Wrap if metadata retention is desired
   ; dv    = uv2dvG_Wrap (u,v)               ; u,v ==> divergence

   uvd   = dv2uvG (dv)                ; dv  ==> divergent  wind components
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)