Re: Reading Meteosat MPE in GRIB2

Hi Matthew,

I can explain some aspects of your problem, but there are others that
are a mystery and seem to indicate problems. It would be good either
if you can tell us where to download a sample file or else if you can
upload a sample to ftp.cgd.ucar.edu:

(
ftp ftp.cgd.ucar.edu
log in as anonymous;
cd incoming
binary
put <filename>
and then send email telling us the name of the file.
)

Here is what I can tell you:
1) the problem with 5.1.0 is a result of a missing flag in the
compilation of the NCEP-supplied GRIB 2 low-level library. It causes
all GRIB 2 files to seem empty. It only affects 64-bit versions of
NCL so this diagnosis is based on the assumption that you are using a
64-bit NCL.
2) The missing parameter entries are visible in your file as
variables VAR_3_1_98_P30_GLL1 and VAR_3_1_99_P30_GLL1. Coordinate
variables in NCL's representation of GRIB data are always generated
by NCL. They are not found in the code tables and therefore do not
have parameter numbers.
3) The space-view perspective grid is not fully supported yet in NCL.
That is why there are no coordinate variables associated with
dimensions 'lat_0' or 'lon_0'. However,
there should have been a warning indicating this fact and the
dimension names are misleading and seems to indicate a bug. They
should have 'x' and 'y' in their names rather than 'lat' and 'lon'.
Implementing coordinates for the space-view perspective grid is on
the active priority list, and hopefully will be completed soon.
4) The Lo1 and La1 attributes for the lat_1, lon_1 coordinates seem
to be incorrect as well.
  -dave

On May 14, 2009, at 12:09 PM, Matthew Janiga wrote:

> I'm having some peculiar problems reading the Meteosat Multi-sensor
> precipitation files in GRIB2.
>
> http://oiswww.eumetsat.int/~idds/html/grib.html (MET-9 files)
>
> I have tried using NCL version 5.0.1 and 5.1.0. NCL_filedump in
> version 5.0.1 is able to display most of the variables...
>
> Copyright (C) 1995-2008 - All Rights Reserved
> University Corporation for Atmospheric Research
> NCAR Command Language Version 5.0.1-beta
> The use of this software is governed by a License Agreement.
> See http://www.ncl.ucar.edu/ for more details.
> warning: Entry (98) not found in code table file /jm12/carl/
> ncl-5.0.1-beta/lib/n
> carg/grib2_codetables/ecmwf/4/4.2.3.1.table
> warning: Entry (99) not found in code table file /jm12/carl/
> ncl-5.0.1-beta/lib/n
> carg/grib2_codetables/ecmwf/4/4.2.3.1.table
> Variable: f (file variable)
>
> filename: MPE_20090513_0000_M9_00
> path: MPE_20090513_0000_M9_00.grb
> file global attributes:
> dimensions:
> lat_0 = 3712
> lon_0 = 3712
> lat_1 = 24
> lon_1 = 24
> variables:
> float INSTRR_P30_GSV0 ( lat_0, lon_0 )
> center : EUMETSAT Operation Centre
> production_status : Operational test products
> long_name : Instantaneous rain rate
> units : kg m-2 s-1
> _FillValue : -999
> grid_type : Space view perspective or orthographic
> parameter_discipline_and_category : Space products,
> Moisture
> parameter_template_discipline_category_number :
> ( 30, 3, 1, 1 )
> initial_time : 05/13/2009 (00:00)
>
> float VAR_3_1_98_P30_GLL1 ( lat_1, lon_1 )
> center : EUMETSAT Operation Centre
> production_status : Operational test products
> long_name : unknown variable name
> units : unknown
> _FillValue : -999
> grid_type : Latitude/longitude
> parameter_discipline_and_category : Space products,
> Moisture
> parameter_template_discipline_category_number :
> ( 30, 3, 1, 98 )
> initial_time : 05/13/2009 (00:00)
>
> float VAR_3_1_99_P30_GLL1 ( lat_1, lon_1 )
> center : EUMETSAT Operation Centre
> production_status : Operational test products
> long_name : unknown variable name
> units : unknown
> _FillValue : -999
> grid_type : Latitude/longitude
> parameter_discipline_and_category : Space products,
> Moisture
> parameter_template_discipline_category_number :
> ( 30, 3, 1, 99 )
> initial_time : 05/13/2009 (00:00)
>
> float lat_1 ( lat_1 )
> long_name : latitude
> grid_type : Latitude/Longitude
> units : degrees_north
> Dj : 95.97755
> Di : 2.608696
> Lo2 : 60
> La2 : 60
> Lo1 : -1e-06
> La1 : -2147.484
>
> float lon_1 ( lon_1 )
> long_name : longitude
> grid_type : Latitude/Longitude
> units : degrees_east
> Dj : 95.97755
> Di : 2.608696
> Lo2 : 60
> La2 : 60
> Lo1 : -1e-06
> La1 : -2147.484
>
> However, lat_0 and lon_0 are not displayed I assume they are entry 98
> and 99. I also have tried using NCL_filedump from version 5.1.0 which
> results in the following....
>
> Copyright (C) 1995-2009 - All Rights Reserved
> University Corporation for Atmospheric Research
> NCAR Command Language Version 5.1.0
> The use of this software is governed by a License Agreement.
> See http://www.ncl.ucar.edu/ for more details.
> Variable: f (file variable)
>
> filename: MPE_20090513_1500_M9_00
> path: MPE_20090513_1500_M9_00.grb
> file global attributes:
> dimensions:
> variables:
>
> Is NCL simply missing the necessary tables? Since I use NCL for most
> image processing it would be quite helpful if I didn't have to convert
> these files into some other format before reading them into NCL.
>
> Much appreciated!
> Matt
>
> --
> **********************************
> Matthew A. Janiga
> Department of Earth and Atmospheric Sciences, ES 330
> University at Albany / State University of New York
> 1400 Washington Avenue
> Albany, NY 12222
> PH: (847) 962-8397
> Email: janiga_at_atmos.albany.edu
> **********************************
> _______________________________________________
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Received on Thu May 14 2009 - 13:16:15 MDT