Hi Steve,
Thanks for reporting the problem, it will be on the list of Grib problems to fix. For future reference, I'm no longer working on the Grib library but included the Grib library developer in this response.
Robb...
On Thu, 7 Oct 2010, Steve Ansari wrote:
Hi David, Jack,
I've cc-ed Robb at Unidata who I believe is the lead GRIB guy.
Robb - see below - we have having issues reading some RTMA GRIB files.
Thanks! Steve
David Miller wrote:Steve,
The only thing I can think of is that the Java API may be getting confused between the Dewpoint temperature and the Dewpoint temperature error that are both in the file. There's a subtle difference that distinguishes the two and that is the generation process, which is contained in GRIB2 template 4.0, Table 4.3, Octet 12. The parameter category is still the same (template 4.0, table 4.2-0-0, Octet 11), and that's 6 - Dew point Temperature. Here is the first table I'm referring to.
http://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_table4-3.shtml
I see from what you gave in ncdump that this generation process isn't mentioned. For regular dew point grids, it is 6 but for error analysis it is 7. So, if the Java API isn't expecting to deal with this within the file, it may be getting confused here because it can't distinguish between the two.
The MDL degribber handles this okay, BTW. So must be something in the Java API and may be related to what I just stated.
The error grids are not contained in the 2dvarges grids and this is perhaps another indication that the error grids are causing the problem in the 2dvaranl grids.
Dave
On 10/6/2010 5:45 PM, Steve Ansari wrote:Hi Dave, Jack,
I've been trying to debug the RTMA problems and I'm running into some trouble.
I'm using the NetCDF for Java API, which supports GRIB1 and GRIB2.
However, I'm getting errors reading the actual files and it seems
that the API is getting lost somewhere inside the file. I updated my
NetCDF for Java version to the new stable 4.2 release, this seems to
have solved the errors. However, the invalid dew point temperatures
still exist for the 2dvaranl files. The '2dvarges' files seem to be ok.
I'm attaching the 'ncdump' below which should show some of the GRIB parameters. I'm working with the current files available on: ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/rtma/prod/rtma.20101005
I'm not sure what to make of this. I don't think there is much else I can do on my end to configure the GRIB decoders, but feedback can be given to Unidata, who develop and maintain the API.
Thanks, Steve
rtma.t23z.2dvaranl_ndfd.grb2:
float Dew_point_temperature(time=1, height_above_ground1=1, y=689, x=1073); :units = "K"; :long_name = "Dew_point_temperature @ height_above_ground"; :missing_value = NaNf; // float :grid_mapping = "Lambert_Conformal"; :GRIB_param_discipline = "Meteorological_products"; :GRIB_param_category = "Temperature"; :GRIB_param_name = "Dew_point_temperature"; :GRIB_param_id = 2, 0, 0, 6; // int :GRIB_product_definition_template = 0; // int :GRIB_product_definition_template_desc = "Analysis/forecast at horizontal level/layer at a point in time"; :GRIB_level_type = 103; // int :GRIB_level_type_name = "height_above_ground"; :GRIB_VectorComponentFlag = "gridRelative";
rtma.t23z.2dvarges_ndfd.grb2:
float Dew_point_temperature(time=1, height_above_ground1=1, y=689, x=1073); :units = "K"; :long_name = "Dew_point_temperature @ height_above_ground"; :missing_value = NaNf; // float :grid_mapping = "Lambert_Conformal"; :GRIB_param_discipline = "Meteorological_products"; :GRIB_param_category = "Temperature"; :GRIB_param_name = "Dew_point_temperature"; :GRIB_param_id = 2, 0, 0, 6; // int :GRIB_product_definition_template = 0; // int :GRIB_product_definition_template_desc = "Analysis/forecast at horizontal level/layer at a point in time"; :GRIB_level_type = 103; // int :GRIB_level_type_name = "height_above_ground"; :GRIB_VectorComponentFlag = "gridRelative";
Jack Settelmaier wrote:
Dave,
I just popped open a new instance of the W&CT and pointed to the RTMA data directory, and this time I got no errors ( I think the errors that popped up earlier were cache errors, and it still displayed after that âwarningâ), and a pop-up window immediately showed me the available fields, time steps, etc., to select to display so Iâm guessing we just hit a burp when we tested this earlier, and this functionality to reveal the fields and time steps in the GRIB file exists. Iâll retry your LAMP data file next and paste below this image; actually Iâll put that in the next email, to save from having too much in one email shipment.
Unfortunately, what Iâm seeing in this 1^st screen capture, Steve, is that Iâm supposedly displaying RTMA Dewpoint from 12UTC this morning (you can see the place/file Iâm pointing to), but yet the units displayed in the legend, and apparently, to my eye, what is displayed in the image is not observed dewpoint, but perhaps more likely the dewpoint uncertainty field.
Now that I think about I, these RTMA Analysis files contain both the observed field and the uncertainty in the observation, and my guess is, in the GRIB, they donât properly distinguish between those two different fields, hence your code only shows me one of them (likely the uncertainty) in the field listing.
In fact, in using deGRIB on this RTMA file, you can see the differing short and long name fields in the GRIB file, but my guess is, Steve, your code only looks at some other âcolumnâ of information and canât distinguish between short names TMP and TMPERR, and only lists the latter listing (errors) in your list.
Can you take a look at this and see if this is a bug in your code, or bad coding on behalf of these GRIB creators?
BTW, Steve, Dave Miller and I will be working together on some of his GRIB data (see next email), and we expect to use your Beta code and feedback things we find to you. I honestly havenât toyed with your code since I was more on this back in the spring and early summer. But Dave has reinvigorated me to explore your command line functionality for potential automated KML/KMZ creation. I canât recall if this functionality is expected to work from the command line or not.
Thanks for any comments you can provide on what Iâve described here, and command line functionality and KML/KMZ expectations.
-- Steve Ansari Physical Scientist NOAA's National Climatic Data Center Veach-Baley Federal Building 151 Patton Avenue Asheville, NC 28801 Ph: 828-271-4611 Fax: 828-271-4328
-- Steve Ansari Physical Scientist NOAA's National Climatic Data Center Veach-Baley Federal Building 151 Patton Avenue Asheville, NC 28801 Ph: 828-271-4611 Fax: 828-271-4328
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Robb Kambic Unidata Program Center Software Engineer III Univ. Corp for Atmospheric Research address@hidden WWW: http://www.unidata.ucar.edu/ ===============================================================================
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