[Met_help] [Fwd: Re: Points of clarification for data conversion/usage in MODE]
Tressa Fowler
tressa at ucar.edu
Tue Mar 16 16:52:28 MDT 2010
Hi Matt,
I'm not an expert at copygb, but I think you are not specifying the
grid you actually want. Your command line asks for NCEP grid #27.
Here's the description of that grid.
4225-point (65x65) N. Hemisphere polar stereographic grid oriented
80W; Pole at (33,33).
Perhaps you should see the NCEP web page to choose a different grid? http://www.nco.ncep.noaa.gov/pmb/docs/on388/tableb.html
Thanks,
Tressa
On Mar 16, 2010, at 4:07 PM, John Halley Gotway wrote:
> Matt,
>
> I'm forwarding your message to the "met_help at ucar.edu" email address.
> Unfortunately, I'm out of the office at all week. I'm with my son's
> who's
> recovering from a burst appendix. He's recovering nicely, but we'll
> be
> here with him all week.
>
> Perhaps Tressa, Randy, or Paul could help you debug the issues you're
> experiencing. I should be available to help out sometime next week.
>
> Thanks,
> John
>
> ---------------------------- Original Message
> ----------------------------
> Subject: Re: Points of clarification for data conversion/usage in MODE
> From: "Matthew Souders" <matt.souders at gmail.com>
> Date: Tue, March 16, 2010 1:29 pm
> To: "John Halley Gotway" <johnhg at ucar.edu>
> --------------------------------------------------------------------------
>
> OK...never mind about the last problem...my apologies for bothering
> you. I
> got PCP_Combine to run, but there is definitely something wrong with
> the
> copygb-converted GRIB file, because I am not getting all of the
> northern
> hemisphere when I use NCView to look at the resulting .nc file...it
> should
> produce a 91 by 360 pole-centered grid...instead it produces a 65X65
> square
> centered on Italy (roughly) that only reveals most of Europe and north
> Africa (and the Middle East).
>
> The precip data looks odd too...3-hourly values with little areas of
> 5+
> inches...hard to fathom that.
>
> On 3/15/10, Matthew Souders <matt.souders at gmail.com> wrote:
>>
>> I'm probably missing something ridiculously obvious, but I am
>> trying to run
>> a quick experiment using a GFS .grb file I acquired today. I ran the
> copygb
>> utility on grid 003 GFS global domain (gave it the following
>> command:
>> copygb -xg 27 gfs_3_20100313_0000_003.grb
>> gfs_27_20100313_0000_003.grb),
> and
>> that may or may have worked properly (it produced a file, but the
>> size of
>> that file was an order of magnitude smaller...which I don't think is
>> right...and it gave me a handful of messages about remaining memory
>> being
>> allocated to some file called polatev0.f)...but I decided to see
>> what it
>> looked like by running the PCP_Combine utility...I got into the
>> METv2.0
> main
>> directory and issued this command:
>>
>> bin/pcp_combine \ -sum 20100313_030000 3 20100313_030000 3 \
>> test_ncfile_gfs.nc
>>
>> I only have a single time step in my .grb, so all this should do is
>> add up
>> one time step and re-output the data in .nc format.
>>
>> It's giving me this error though:
>>
>> ERROR: process_sum_args() -> The init_time and valid_time command
>> line
>> arguments must be in the form YYYYMMDD_HHMMSS
>>
>> What confuses me...is that my arguments ARE in that format. Not
>> sure why
>> it's giving me that error. Any ideas?
>>
>>
>> On 3/12/10, John Halley Gotway <johnhg at ucar.edu> wrote:
>>>
>>> Matt,
>>>
>>> Yeah, polar stereographic is fine. Actually, *northern* polar
>>> stereographic is currently supported in MET - not southern yet for
>>> some
>>> reason. You just need to figure out what to put in the NetCDF
>>> header to define it. If you can get your hands on a GRIB file,
>>> you could
>>> run it through the copygb tool to interpolate it a polar
>>> stereographic
>>> projection. Then run it through the PCP-Combine tool
>>> (the operation you do with PCP-Combine doesn't really matter).
>>> And then
>>> look at the NetCDF output file.
>>>
>>> Just let me know if you get stuck anywhere.
>>>
>>>
>>> John
>>>
>>>
>>> Matthew Souders wrote:
>>>> Boy...it seems like no matter what alley I drive down, there's an
>>>> acme
>>> anvil
>>>> rigged to fall on my head. I should change my last name to Coyote.
>>>>
>>>> In all seriousness, I do appreciate you going through the various
>>>> tools
>>> and
>>>> ideas with me...at this point...I am thinking it would be a less
>>>> painful
>>>> task to change map projection of my data BEFORE I try to create the
>>> netCDF
>>>> than it would be to convert it later. I al going to have to
>>>> write some
>>> kind
>>>> of MATLAB script to convert every piece of data I have to a
>>>> projection I
>>> can
>>>> use...at which point I can then convert to netCDF and read the
>>>> thing
>>> into
>>>> MODE, I assume? Will MODE recognize a netCDF file in a polar
>>> stereographic
>>>> projection?
>>>>
>>>> On 3/12/10, John Halley Gotway <johnhg at ucar.edu> wrote:
>>>>> Matt,
>>>>>
>>>>> Here's a link regarding that:
>>>>> http://www.unidata.ucar.edu/software/netcdf/docs/faq.html#grib
>>>>>
>>>>> Converting GRIB to NetCDF is pretty easy. The tool
>>>>> "ncl_convert2nc"
>>> does
>>>>> it for you. Going the other way is much more difficult. And
>>>>> really,
>>> I've
>>>>> never done it before.
>>>>>
>>>>>
>>>>> John
>>>>>
>>>>> Matthew Souders wrote:
>>>>>> Unfortunately, I have not used NCL before. Given my time
>>>>>> limmitations
>>> in
>>>>>> completely this analysis, I am thinking that will be
>>>>> impractical. regular
>>>>>> lat/lon doesn't really work because I have to split the grid in
>>>>>> half
>>> and
>>>>>> then track objects that straddle the divide somehow...which
>>>>>> causes
>>> lots
>>>>> of
>>>>>> problems. There is software out there that can convert a
>>>>>> netCDF to a
>>>>> GRIB,
>>>>>> isn't there? I seem to recall that being out there in some form.
>>>>>>
>>>>>> On 3/12/10, John Halley Gotway <johnhg at ucar.edu> wrote:
>>>>>>> Matt,
>>>>>>>
>>>>>>> There is no general tool for regridding NetCDF files from one
>>>>>>> grid to
>>>>>>> another. You may be able to write an NCL (NCAR Command
>>>>>>> Language)
>>> script
>>>>> to
>>>>>>> do so, but there's a learning curve if you haven't
>>>>>>> used NCL before.
>>>>>>>
>>>>>>>
>>>>>>> John
>>>>>>>
>>>>>>>
>>>>>>> Matthew Souders wrote:
>>>>>>>> One reason I started down the long and scary road of trying to
>>> create
>>>>>>> GRIB
>>>>>>>> files was to gain access to the copygb utility in order to
>>>>>>>> convert
>>> my
>>>>>>>> regular lat/lon grid to polar stereographic without too much
>>>>>>> hardship. Is
>>>>>>>> there a way to convert a netCDF file in regular lat/lon to
>>>>>>>> polar
>>>>>>>> stereographic simply?
>>>>>>>>
>>>>>>>> It does seem like using netCDF is a better way to go...I
>>>>>>>> believe
>>> even
>>>>>>> MATLAB
>>>>>>>> (my main dta interface tool) has a netCDF writer...it
>>>>>>>> definitely has
>>>>> (and
>>>>>>> I
>>>>>>>> use) a netCDF reader. But I need to figure out how to change
>>>>>>>> map
>>>>>>>> projections and how exactly to set up the netCDF file so that
>>>>>>>> MODE
>>> can
>>>>>>>> understand it.
>>>>>>>>
>>>>>>>> I will take a look at the output from P2P_Combine...that file
>>>>> definitely
>>>>>>>> created successfully when I ran the test script...I can see
>>>>>>>> it in my
>>>>>>>> directory.
>>>>>>>>
>>>>>>>> On 3/12/10, John Halley Gotway <johnhg at ucar.edu> wrote:
>>>>>>>>> Matt,
>>>>>>>>>
>>>>>>>>> Creating a GRIB file is a rather ambitious task I have never
>>> actually
>>>>>>> done
>>>>>>>>> myself. If I were in your position, I'd actually reformat
>>>>>>>>> your
>>> binary
>>>>>>> data
>>>>>>>>> into a NetCDF file that looks like the output of
>>>>>>>>> the PCP-Combine tool. MODE can read either GRIB data or the
>>>>>>>>> NetCDF
>>>>>>> output
>>>>>>>>> of PCP-Combine. There are a lot more utilities out there for
>>> writing
>>>>>>> NetCDF
>>>>>>>>> files than there are for writing GRIB files.
>>>>>>>>>
>>>>>>>>> Use the "ncdump" utility to view the NetCDF output from PCP-
>>>>>>>>> Combine
>>> in
>>>>>>> the
>>>>>>>>> "METv2.0/out/pcp_combine" directory. These files are
>>>>>>>>> created when
>>> you
>>>>>>> run
>>>>>>>>> the test script included with MET. And just
>>>>>>>>> mimick the file structure with your data.
>>>>>>>>>
>>>>>>>>> If you choose to go that route, you'll probably need some help
>>>>> choosing
>>>>>>> the
>>>>>>>>> variable name and setting up the grid definition information
>>>>>>>>> in
>>> NetCDF
>>>>>>>>> header. We're working on expanding our support for
>>>>>>>>> NetCDF files for the next release of MET. They're a lot
>>>>>>>>> easier to
>>>>> work
>>>>>>>>> with than GRIB files are.
>>>>>>>>>
>>>>>>>>> Let me know how you plan to proceed and what other questions
>>>>>>>>> you
>>> have.
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>>
>>>>>>>>> John
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Matthew Souders wrote:
>>>>>>>>>> Hello John,
>>>>>>>>>>
>>>>>>>>>> This is Matthew Souders (Stony Brook University) - I
>>>>>>>>>> apologize for
>>>>>>> taking
>>>>>>>>> up
>>>>>>>>>> a bit more of your time, but I am running into some trouble
>>> getting
>>>>>>> data
>>>>>>>>>> read into MODE for which I thought you might have a
>>>>>>>>>> solution on
>>> hand
>>>>> to
>>>>>>>>>> help. My basic data is a single variable on a 2.5 by 2.5
>>>>>>>>>> degree
>>>>>>> regular
>>>>>>>>>> lat/lon grid in fortran direct access BINARY format. I
>>>>>>>>>> have been
>>>>>>> trying
>>>>>>>>> to
>>>>>>>>>> get it intelligibly read into GRIB format (the form MODE
>>>>>>>>>> needs)
>>> for a
>>>>>>>>> month
>>>>>>>>>> now using Wesley Ebusizaki's gribw utility; however, you
>>>>>>>>>> need a
>>>>> rather
>>>>>>>>>> significant background in C scripting to rewrite his basic
>>>>>>>>>> code
>>> and
>>>>>>> make
>>>>>>>>>> proper use of the PDS file writer. As I understand it...MODE
>>> needs
>>>>>>> this
>>>>>>>>> PDS
>>>>>>>>>> file to operate properly. I can create a GRIB using the
>>>>>>>>>> default
>>> PDS
>>>>>>>>> file,
>>>>>>>>>> but that doesn't accurately describe the data in the GRIB.
>>>>>>>>>>
>>>>>>>>>> I tried e-mail Wesley on this matter but he is understandably
>>>>> extremely
>>>>>>>>> busy
>>>>>>>>>> and limits support to installation and debugging issues. He
>>>>> basically
>>>>>>>>> just
>>>>>>>>>> directed me to the GRIB standard release. I was wondering
>>>>>>>>>> if you
>>> had
>>>>>>> any
>>>>>>>>>> experience getting binary data read into MODE or if you knew
>>> someone
>>>>>>> who
>>>>>>>>>> might be able to help?
>>>>>>>>>>
>>>>>>>>>> I also would like to know how exactly the MODE tool uses
>>>>>>>>>> the PDS
>>>>>>> file? I
>>>>>>>>>> ask because I am trying to figure out how picky it is w/r/t
>>>>>>>>>> what
>>> is
>>>>> in
>>>>>>>>> the
>>>>>>>>>> PDS file vs. what is in the actual GRIB file.
>>>>>>>>>>
>>>>>>>>>> Thanks in advance for your time.
>>>>>>>>>>
>>>>>>>>>> Matt Souders.
>>>>>>>>>>
>>>>
>>>
>>
>>
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