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fo2fshv

Interpolates a vector quantity from a fixed-offset grid to a fixed grid.

Prototype

	procedure fo2fshv (
		uoff  : numeric,  
		voff  : numeric,  
		ureg  : float,    ; or double
		vreg  : float     ; or double
	)

Arguments

uoff
voff

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

ureg
vreg

(output)
Vector arrays of 2 or more dimensions whose rightmost two dimensions must be latitude x longitude. Values will be in ascending latitude order.

The arrays must be the same size as the uoff and voff arrays, except the latitude dimension must have one extra element.

Since fo2fshv is a procedure, the user must explicitly preallocate memory for these return arrays.

Description

fo2fshv interpolates a vector pair on a fixed-offset grid (uoff,voff) (including pole points) to a fixed grid (ureg,vreg) using spherical harmonics (via the Spherepack code). The output array dimensions must be the same as the input array dimensions, except jlat is replaced by jlat+1. For example, a 5 degree fixed-offset grid would have dimensions nlata=36, nlona=72, and the return fixed grid would have dimensions nlatb=37, nlonb=72.

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 fo2fshv via:

  z = fo2fshv(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 the fo2fshv_Wrap procedure if metadata retention is desired. The interface is identical.

See Also

f2foshv, f2fshv, f2gshv, 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 offset 2.5 degree grid (nlat=72, nlon=144) to a fixed grid with 2.5 degree resolution (jlat=73, ilon=144):

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

  fo2fshv (u,v, uNew,vNew)

  ; Use fo2fshv_Wrap if metadata retention is desired
  ; fo2fshv_Wrap (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