Just to expand a bit on what Dennis said: NCL now handles
reduced grids by interpolating extra points to produce a
rectangular array where the number of points along the reduced
dimension is equal to the row with the greatest number of
points. The interpolation routine is adapted from code supplied
by ECMWF. Both standard and Gaussian reduced grids are supported.
Theoretically standard grids may be reduced along either the
latitude or longitude direction, though no latitudinally-reduced
examples have been observed or tested. If you encounter a
GRIB file where NCL reports a size of 65535 for a dimension,
then it's probably a reduced dimension and the new version of NCL
On Mon, 27 Jan 2003, Dennis Shea wrote:
> >I am trying to read JMA forecast files in GRIB format with NCL.
> >The number of longitudinal grids reduced toward the poles
> >thus grids are not rectilinear.
> >These files do not follow NCL's convection and
> >does not provide gridx and gridy.
> >Longitude grid arrays are problematic as below.
> >Is there anything I can do in the script?
> >Otherwise I will preprocess the files with other tools.
> Hello Takeshi,
> The new version of NCL [a028] will handle these GRIB
> "quasi-regular" grids (ie: reduced grids). It autonatically
> unpacks the grid into 1.25 x 1.25 degree grids.
> The "lat_37" and "lon_37" variables will look like:
> printVarSummary (lon_37)
> Variable: lon_37
> Type: float
> Total Size: 292 bytes
> 73 values
> Number of Dimensions: 1
> Dimensions and sizes: [lon_37 | 73]
> lon_37: [-30..60]
> Number Of Attributes: 8
> GridType : Cylindrical Equidistant Projection Grid (Quasi-Regular)
> units : degrees_east
> Dj : 1.25
> Di : 1.25
> Lo2 : 60
> La2 : 90
> Lo1 : -30
> La1 : 0
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