[ncl-talk] Wrong time decoding on grib2

Nicolas GASNIER ngprod41 at gmail.com
Tue Aug 4 03:50:33 MDT 2015


Hello NCL users,

I'm facing another GRIB problem with the new Meteo France datasets.

This is the ARPEGE and AROME model outputs, freely available as GRIB2 
files. Datas are stored in different grib sets for surface data and 
pressure level/height data, with a set for a group of 12 and 6 hours 
forecasts respectively.

NCL can read correctly the first time set (00H12H for ARPEGE for 
example), but it starts to bug for further forecasts. It seems like NCL 
doesn't interpret correctly the time variable, and that problem seems to 
increase as the forecast time increase.

For example, for the first surface dataset for ARPEGE (SP1), if you 
print ncl_filedump, the dimension of forecast_time0 variable
is 12 for the 00H12H echeances and the dimension of the TPRATE variable 
is (time, lat, lon). It has only 4 for the next 13H24H, and for the 
latest sets (75H84H or 85H96H) it alternates between 1 and 2. The TPRATE 
variable is 2D only (lat, lon). The expected result is 12 forecast hours 
for every set, and the TPRATE variable shoud be always (forecast_time, 
lat, lon), as one can see with a wgrib2 ouput (see example output at end 
of mail).

I can convert to netcdf, using wgrib2 or grib_to_netcdf utility : the 
time dimension becomes correct. But that process crash sometimes - maybe 
due to particularities of the dataset. Anyway, it is too disk and CPU 
intensive to be reasonable for my application.

I hope this issue can be worked around. Any clue about that will be much 
appreciated, even solutions involving source patching and compiling !

The files are too big to be included, but one can get the datasets 
directly on MF web site for a test (use SP1 dataset for example) :

For ARPEGE :
https://donneespubliques.meteofrance.fr/?fond=produit&id_produit=130&id_rubrique=51

For AROME
https://donneespubliques.meteofrance.fr/?fond=produit&id_produit=131&id_rubrique=51

Thanks for any help.

Regards

Nicolas Gasnier

-------------------------------------------------
Result for the 00H12H dataset :

$ ncl_filedump ARPEGE_0.1_00H12H_SP1.grib2
  Copyright (C) 1995-2015 - All Rights Reserved
  University Corporation for Atmospheric Research
  NCAR Command Language Version 6.3.0
  The use of this software is governed by a License Agreement.
  See http://www.ncl.ucar.edu/ for more details.

Variable: f
Type: file
filename:    ARPEGE_0.1_00H12H_SP1
path:    ARPEGE_0.1_00H12H_SP1.grib2
    file global attributes:
    dimensions:
       forecast_time0 = 13
       lat_0 = 521
       lon_0 = 741
       forecast_time1 = 12
    variables:

...

       float TPRATE_P8_L1_GLL0_acc ( forecast_time1, lat_0, lon_0 )
          center :    French Weather Service - Toulouse
          production_status :    Operational products
          long_name :    Total precipitation rate
          units :    kg m-2s-1
          _FillValue :    1e+20
          grid_type :    Latitude/longitude
          parameter_discipline_and_category :    Meteorological 
products, Moisture
          parameter_template_discipline_category_number :    ( 8, 0, 1, 52 )
          level_type :    Ground or water surface
          type_of_statistical_processing :    Accumulation
          statistical_process_duration :    initial time to forecast time
          initial_time :    08/04/2015 (00:00)

       integer forecast_time1 ( forecast_time1 )
          long_name :    Forecast offset from initial time
          units :    hours
...

$ wgrib2 ARPEGE_0.1_00H12H_SP1.grib2
1:0:d=2015080400:PRES:mean sea level:anl:
...
144:36148384:d=2015080400:TPRATE:surface:0-1 hour acc fcst:
145:36345772:d=2015080400:TPRATE:surface:0-2 hour acc fcst:
146:36550429:d=2015080400:TPRATE:surface:0-3 hour acc fcst:
147:36778596:d=2015080400:TPRATE:surface:0-4 hour acc fcst:
148:36995319:d=2015080400:TPRATE:surface:0-5 hour acc fcst:
149:37226250:d=2015080400:TPRATE:surface:0-6 hour acc fcst:
150:37469285:d=2015080400:TPRATE:surface:0-7 hour acc fcst:
151:37723534:d=2015080400:TPRATE:surface:0-8 hour acc fcst:
152:37989302:d=2015080400:TPRATE:surface:0-9 hour acc fcst:
153:38266837:d=2015080400:TPRATE:surface:0-10 hour acc fcst:
154:38556419:d=2015080400:TPRATE:surface:0-11 hour acc fcst:
155:38821541:d=2015080400:TPRATE:surface:0-12 hour acc fcst:
...


-------------------------------------------------
Result for the 73H84H dataset :

$ ncl_filedump ARPEGE_0.1_73H84H_SP1.grib2
  Copyright (C) 1995-2015 - All Rights Reserved
  University Corporation for Atmospheric Research
  NCAR Command Language Version 6.3.0
  The use of this software is governed by a License Agreement.
  See http://www.ncl.ucar.edu/ for more details.

Variable: f
Type: file
filename:    ARPEGE_0.1_73H84H_SP1
path:    ARPEGE_0.1_73H84H_SP1.grib2
    file global attributes:
    dimensions:
       forecast_time0 = 12
       lat_0 = 521
       lon_0 = 741
    variables:
...
       float TPRATE_P8_L1_GLL0_acc ( lat_0, lon_0 )
          center :    French Weather Service - Toulouse
          production_status :    Operational products
          long_name :    Total precipitation rate
          units :    kg m-2 s-1
          _FillValue :    1e+20
          grid_type :    Latitude/longitude
          parameter_discipline_and_category :    Meteorological 
products, Moisture
          parameter_template_discipline_category_number :    ( 8, 0, 1, 52 )
          level_type :    Ground or water surface
          type_of_statistical_processing :    Accumulation
          statistical_process_duration :    initial time to forecast time
          forecast_time :    72
          forecast_time_units :    hours
          initial_time :    08/04/2015 (00:00)
...

$ wgrib2 ARPEGE_0.1_73H84H_SP1.grib2
...
133:34691684:d=2015080400:TPRATE:surface:0-73 hour acc fcst:
134:35059823:d=2015080400:TPRATE:surface:0-74 hour acc fcst:
135:35429187:d=2015080400:TPRATE:surface:0-75 hour acc fcst:
136:35799682:d=2015080400:TPRATE:surface:0-76 hour acc fcst:
137:36171501:d=2015080400:TPRATE:surface:0-77 hour acc fcst:
138:36544719:d=2015080400:TPRATE:surface:0-78 hour acc fcst:
139:36919171:d=2015080400:TPRATE:surface:0-79 hour acc fcst:
140:37294798:d=2015080400:TPRATE:surface:0-80 hour acc fcst:
141:37671824:d=2015080400:TPRATE:surface:0-81 hour acc fcst:
142:38049918:d=2015080400:TPRATE:surface:0-82 hour acc fcst:
143:38429238:d=2015080400:TPRATE:surface:0-83 hour acc fcst:
144:38809833:d=2015080400:TPRATE:surface:0-84 hour acc fcst:
...


-------------------------------------------------
Result for the 85H96H dataset :

$ ncl_filedump ARPEGE_0.1_85H96H_SP1.grib2
  Copyright (C) 1995-2015 - All Rights Reserved
  University Corporation for Atmospheric Research
  NCAR Command Language Version 6.3.0
  The use of this software is governed by a License Agreement.
  See http://www.ncl.ucar.edu/ for more details.

Variable: f
Type: file
filename:    ARPEGE_0.1_85H96H_SP1
path:    ARPEGE_0.1_85H96H_SP1.grib2
    file global attributes:
    dimensions:
       forecast_time0 = 12
       lat_0 = 521
       lon_0 = 741
       forecast_time1 = 2
    variables:
...
       float TPRATE_P8_L1_GLL0_acc ( forecast_time1, lat_0, lon_0 )
          center :    French Weather Service - Toulouse
          production_status :    Operational products
          long_name :    Total precipitation rate
          units :    kg m-2 s-1
          _FillValue :    1e+20
          grid_type :    Latitude/longitude
          parameter_discipline_and_category :    Meteorological 
products, Moisture
          parameter_template_discipline_category_number :    ( 8, 0, 1, 52 )
          level_type :    Ground or water surface
          type_of_statistical_processing :    Accumulation
          statistical_process_duration :    initial time to forecast time
          initial_time :    08/04/2015 (00:00)

$ wgrib2 ARPEGE_0.1_85H96H_SP1.grib2
...
133:33228276:d=2015080400:TPRATE:surface:0-85 hour acc fcst:
134:33612201:d=2015080400:TPRATE:surface:0-86 hour acc fcst:
135:33997998:d=2015080400:TPRATE:surface:0-87 hour acc fcst:
136:34385885:d=2015080400:TPRATE:surface:0-88 hour acc fcst:
137:34775283:d=2015080400:TPRATE:surface:0-89 hour acc fcst:
138:35165904:d=2015080400:TPRATE:surface:0-90 hour acc fcst:
139:35557513:d=2015080400:TPRATE:surface:0-91 hour acc fcst:
140:35949966:d=2015080400:TPRATE:surface:0-92 hour acc fcst:
141:36343265:d=2015080400:TPRATE:surface:0-93 hour acc fcst:
142:36737384:d=2015080400:TPRATE:surface:0-94 hour acc fcst:
143:37132325:d=2015080400:TPRATE:surface:0-95 hour acc fcst:
144:37528229:d=2015080400:TPRATE:surface:0-4 day acc fcst:




More information about the ncl-talk mailing list