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20051026: NCDC to Unidata NEXRAD II converter

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  • Subject: 20051026: NCDC to Unidata NEXRAD II converter
  • Date: 26 Oct 2005 16:03:40 -0600
Art,

We don't do any formatting to the Level II files you can
obtain via the IDD. The BZIP2 block compression is specified by the 
ROC ICD and done at the source.

Note that some files which you obtain via the web are compressed as
files (or tarfiles), and this is not the same as files which employ
data compression within them. If you obtained tarfiles or gzipped/bzip2
compressed files for download, then these need to be unpacked and/or
uncompressed. If you do an "od -c" on the file, you should see that
the first 9 bytes are ARCHIVE2. or AR20001. If not, then thats not a
valid format.

The Unidata GEMPAK release does handle both the uncompressed as well as
bzip2 compressed Level II files. In fact, before I added the bzip2
capability within the GEMPAK routines, I provided dcnexr2 decoder to
uncompress the bzip2 to products into their uncompressed versions. This
isn't needed now as the bzip2 routines are linked in. The dcnexr2
program did another thing however. It added the 4 character station ID
into bytes 21-24 of the ARCHIVE2.0 header since otherwise, those files
did not have any station location information (ID or lat/lon). If bytes
21-24 are null/blank, then the files should use the supplied file naming
template convention for NEXRII in datatype.tbl so that the site ID can
be determined.

The newer files which have the AR2V0001.0 header do have the station ID
in bytes 21-24

Steve Chiswell
Unidata User Support



On Wed, 2005-10-26 at 13:58, Arthur A. Person wrote:
> Hi...
> 
> Does anyone have or know of a program to convert NCDC plain level II 
> nexrad data into the Unidata formatted files?
> 
> Also, does anyone know whether the gempak and/or nmap2 packages are 
> supposed to be able to read the plain uncompressed NCDC nexrad II files, 
> or do they only work with the Unidata formatted bzip2 compressed files? 
> I tried the plain files with nmap2 but it didn't seem to recognize them.
> 
>                            Thanks.
> 
>                              Art.
> 
> Arthur A. Person
> Research Assistant, System Administrator
> Penn State Department of Meteorology
> email:  address@hidden, phone:  814-863-1563