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rgrid2rcm

Interpolates data on a rectilinear lat/lon grid to a curvilinear grid like those used by the RCM, WRF and NARR models/datasets.

Prototype

	function rgrid2rcm (
		lat      [*] : numeric,  
		lon      [*] : numeric,  
		fi           : numeric,  
		lat2d [*][*] : numeric,  
		lon2d [*][*] : numeric,  
		Option       : numeric   
	)

	return_val  :  numeric

Arguments

lat

A one-dimensional array that specifies the latitude coordinates of the regular grid. Must be monotonically increasing.

lon

A one-dimensional array that specifies the longitude coordinates of the regular grid. Must be monotonically increasing.

fi

A multi-dimensional array to be interpolated. The rightmost two dimensions (latitude, longitude) are the dimensions to be interpolated.

lat2d

A two-dimensional array that specifies the latitude locations of fi. Because this array is two-dimensional, it is not an associated coordinate variable of fi.

lon2d

A two-dimensional array that specifies the longitude locations of fi. Because this array is two-dimensional, it is not an associated coordinate variable of fi.

Option

Reserved for future use. Currently not used. Set to 1.

Return value

A multi-dimensional array of the same size as fi except that the rightmost dimension sizes have been replaced by the sizes of lat2d and lon2d respectively. Double if fi is double, otherwise float.

Description

Interpolates data on a rectilinear lat/lon grid to a curvilinear grid, such as those used by the RCM (Regional Climate Model), WRF (Weather Research and Forecasting) and NARR (North American Regional Reanalysis) models/datasets. No extrapolation is performed beyond the range of the input coordinates. The method used is simple inverse distance weighting. Missing values are allowed but ignored.

For more robust regridding, see the ESMF regridding examples, which show how to regrid data from and to rectilinear, curvilinear, or unstructured grids. Available in version 6.1.0 and later.

Use the rgrid2rcm_Wrap function if metadata retention is desired. The interface is identical.

See Also

rgrid2rcm_Wrap, rcm2rgrid, rcm2points, linint2, linint2_points, ESMF_regrid

Examples

Example 1

Interpolate from gaussian T42 (64,128) grid. 

   f     = addfile ("some_RCM_file.nc", "r")
   lat2d = f->xlat
   lon2d = f->xlon

   fccm  = addfile ("some_CCM_file.nc", "r")
   x     = fccm->X

   xgrd  = rgrid2rcm (x&lat, x&lon, x, lat2d, lon2d, 0)

   ; Use rgrid2rcm_Wrap if metadata retention is desired
   ; xgrd  = rgrid2rcm_Wrap (x&lat, x&lon, x, lat2d, lon2d, 0)

If the output lat2d and lon2d arrays were of size (nlat,nlon), and if the input x was of size: 

           x(64,128) ==>  xgrd(nlat,nlon)
      x(ntim,64,128) ==>  xgrd(ntim,nlat,nlon) 
 x(ntim,klev,64,128) ==>  xgrd(ntim,klev,nlat,nlon)