Jim,
Sorry, it looks like the URL only gives the calling sequence for the
qu2reg3 routine. However, if you were so inclined you could
download the whole GRIBEX package from
http://www.ecmwf.int/publications/manuals/libraries/gribex/
gribexIntroduction.html
-dave
On Nov 11, 2008, at 4:32 PM, David Brown wrote:
> Hi Jim,
> PyNIO automatically expands reduced (quasi-regular in GRIB-speak)
> grids using (by default) a cubic interpolation algorithm.
> The code is from the ECMWF GRIBEX package, and the specific
> function is qu2reg3.F. You can examine the source at this URL:
>
> http://www.ecmwf.int/publications/manuals/libraries/gribex/
> qu2reg3.F.html
>
> The NIO library modifies this code slightly in order to dynamically
> allocate some work arrays from the calling C code and to
> adjust the error handling.
>
> There is a GRIB-specific file option ('ThinnedGridInterpolation')
> that allows you to switch the interpolation mode between 'cubic'
> and 'linear'. This just adjusts the qu2reg3 KCODE argument. Note
> that if there are any missing values in the data, then the 'linear'
> method is forced.
>
> I would be interested to know how the values differ. Dave
> Stepaniak, from the Data Support Services here at NCAR has done some
> fairly rigorous testing of the ECMWF code and concluded that the
> qu2reg3 'cubic' method was significantly more accurate than the
> 'linear'
> method and as good as another candidate method. That is why 'cubic'
> is the default in PyNIO.
> -dave
>
>
> On Nov 11, 2008, at 3:51 PM, James Boyle wrote:
>
>> I have a grid file from ECMWF. The CDO ( Climate Data operators)
>> say that it contains a reduced gaussian grid.
>> I can expand the grid using the CDOs to a full gaussian grid.
>>
>> when I read a variable using pyNIO from the expanded full gaussian
>> grid file and the original 'reduced?' grid, both variables are on
>> the full grid.
>> but the values are not the same
>>
>> What does pyNIO do with variables on a reduced grid? I fully
>> expected to get an error when I read a reduced grid file.
>>
>> --Jim
>> _______________________________________________
>> pyngl-talk mailing list
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/pyngl-talk
>
> _______________________________________________
> pyngl-talk mailing list
> List instructions, subscriber options, unsubscribe:
> http://mailman.ucar.edu/mailman/listinfo/pyngl-talk
_______________________________________________
pyngl-talk mailing list
List instructions, subscriber options, unsubscribe:
http://mailman.ucar.edu/mailman/listinfo/pyngl-talk
Received on Tue Nov 11 2008 - 16:38:45 MST
This archive was generated by hypermail 2.2.0 : Fri Nov 14 2008 - 16:43:44 MST