Re: netCDF and WRF grids

Hi Robert:

I have no doubt that you are finding real bugs; the WRF projections are quite 
difficult to understand; in earlier versions the parameters are actually 
wrong(!). If you can email sample files and whatever fixes you think are right, 
i will test and see if i can corroborate. I will be gone till next week, so i 
will look at it then.

The NMM E grid is a completely different beast than the ARP grid. I need to 
detect and probably just branch to some new code. I spent a while figuring it 
out but didnt finish, i think because since it was rotated, it violated some 
assumptions in the GeoGrid code. I think theres some 2D arrays we could use 
instead that might be a workaround, but i forget the details. I can look at 
that again next week also.

John

Robert B. Schmunk wrote:
> John,
>
> A couple questions/problems regarding using the NJ libraries to
> read some sample WRF datasets which have been provided me by
> a group at NOAA.
>
> First, I have enabled my Panoply application to recognize WRF
> (polar) stereographic data and use the NJ libraries to project it
> onto a standard grid. This seems to work just great for northern
> hemisphere data, but it turns out that southern hemisphere data
> (e.g., Tasmania) is distorted. I have looked at the code for the
> Stereographic class, and that seems okay, but I am wondering if
> the calculation of "scaleFactor" in line 185 of the WRFConvention
> is correct. I note that it doesn't seem to adjust for the change
> of sign when lat1 is less than 0 (i.e., in the S.H.), and so
> for example, if lat1 = -90deg, scaleFactor would be 0.
>
> If you need it, I can e-mail you the sample S.H. stereographic
> dataset. It's about 2 MB.
>
> The second issue regards another WRF grid which apparently is
> not yet handled by the NJ libraries, the WRF NMM "E" grid, also
> identified as MAP_PROJ=203. The comments in the the WRFConvention
> class seem to suggest that dealing with this grid is a hairball,
> i.e., I see the scary phrase "special processing". Does this
> mean that the likelihood of the NJ libraries being able to
> re-project this grid in the foreseeable future is dim?
>
> Also regarding the NMM "E" grid, the sample NOAA dataset I have
> is causing WRFConvention to puke a NullPointerException at line
> 144. Checking the file metadata, I find it contains neither the
> GLAT variable which s supposed to be created at line 143 of
> WRFConvention, nor the GLON variable to be created further down
> at line 149. Is this something that WRFConvention needs to trap
> for?
>
> rbs
>
> --
> Robert B. Schmunk, address@hidden
> NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025