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f2fshv

Interpolates a vector quantity from one fixed grid to another.

Prototype

	procedure f2fshv (
		ua  : numeric,  
		va  : numeric,  
		ub  : float,    ; or double
		vb  : float     ; or double
	)

Arguments

ua
va

Vector arrays of 2 or more dimensions whose rightmost two dimensions must be latitude x longitude. The values must be in ascending latitude order.

ub
vb

(output)
Vector arrays of 2 or more dimensions whose rightmost two dimensions must be latitude x longitude. Values will be in ascending latitude order. All but the two rightmost dimensions must be the same as all but the two rightmost dimensions of ua and va.

Since f2fshv is a procedure, the user must explicitly preallocate memory for these return arrays.

Description

f2fshv interpolates a vector pair from one fixed grid (ua,va) to another (ub,vb) using spherical harmonics (via the Spherepack code).

Arrays which have dimensions [...] x nlata x nlona should not include the cyclic (wrap-around) points when invoking this procedure. For example, if arrays u and v have dimensions nlata = 64 and nlona = 129, where the "129" represents the cyclic point, then the user should pass the data to f2fshv via:

  z = f2fshv(u(...,0:nlona-2), v(...,0:nlona-2),...)  ; does not include cyclic points

This procedure can only be used on grids that span the globe. It cannot be used for limited area grids.

Please read the caveats that you should be aware of when using spherical harmonic regridding.

Use f2fshv_Wrap if retention of metadata is desired.

See Also

f2foshv, f2gshv, fo2fshv, g2fshv, g2gshv

Examples

Example 1

Assume u and v are dimensioned nt x nlat x nlon, and that they are of type float or double.

The code below interpolates from a fixed 2.5 degree grid (nlat=73, nlon=144) to a fixed 2.5 x 5.0 degree grid (jlat=73,ilon=72):

  uNew = new ( (/nt,jlat,ilon/), typeof(u) ) 
  vNew = new ( (/nt,jlat,ilon/), typeof(v) ) 

  f2fshv (u,v, uNew,vNew)

Errors

ier is equal to:

4 or 10 if nlona (ilon) is less than 4
5 or 10 if nlata (jlat) is less than 3
8 if nlonb is less than 4
9 if nlatb is less than 3