# 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rightmost dimension sizes have been replaced by the sizes of *lat2d*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.*

## 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)

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)