Meteogram error

[Jennifer Adams]

Drawing meteograms with grib2 data highlights the principal drawback
of the compressed data format -- you must read and uncompress a
global grid in order to extract data values at a single grid point.
The time series plots and especially the Z-T panel at the top of the
meteogram require a significant amount of memory and I/O when using
grib2 data. My experience is that even on local data files, it can
take 10+ minutes to draw a meteogram. When using data that is behind
GDS ... I'm not sure whether the request would timeout before the I/O
was finished. Haven't tried it.

My workaround for drawing the meteograms at wxmaps.org was to use
fwrite to extract the required data first, then draw the meteograms
based on the fwritten data set. There were other issues too that were
solved with fwrite scripts: the precip fields are 3hr accumulations
at 3hr forecast intervals and 6hr accumulations at 6hr forecast
intervals. I will try to post a generalized script solution to the
grib2 meteogram problem as soon as I can.

The other problem you have is unrelated to the above. I believe the
"Unable to open file" error message might come from a missing null
terminator at the end of the string variable that contains the data
set name. (The behavior of strncpy() does not seem to be the same on
all systems.) This was a bug that was reported by Hoop after he tried
out the 2.0.a1 builds. The patch is a one-line bit of code that will
be in 2.0.a2 (coming out very soon). If you are using a pre-compiled
binary downloaded from COLA, I suggest you try downloading a fresh
copy -- Hoop's builds of 2.0.a1 for 32-bit linux (that are posted on
COLA's FTP server) contain the fix, but they were re-posted a few
days after the release of 2.0.a1.

Jennifer

On Mar 1, 2008, at 12:53 PM, Fil wrote:

> Hi all,
>
> I'm trying to use the meteogram scripts available at IGES ftp
> server but I
> always get the following error:
>
> ga-> meteogram_gfsb Boston 2008030112 -71 42 e
> No hardcopy metafile open
> All files closed; all defined objects released;
> All GrADS attributes have been reinitialized
> NetCDF Error (nc_open): Unable to open file
> http://monsoondata.org:9090/dods/gfs2/gfs.2008030112b
> read_metadata: gaopnc failed
> gadsdf: Couldn't ingest SDF metadata.
>
> I'm using gradsdap 2.0.a1 on i686 32b Linux system. Anyone knows
> what the
> problem is?
>
> Regards.

--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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