[ncl-talk] Fwd: Conactenate or joint GFS grib2 files

[Rabah Hachelaf]

It work,

Thank you.





2017-07-01 10:58 GMT-04:00 Dennis Shea <shea at ucar.edu>:

> Hi Rabah,
>
> NCL's default mode when importing dimensions of size one is to eliminate
> that dimension. Size one dimensions are considered 'degenerate.' GRIB
> formatted  'gfs' files [ eg: gfs.t00z.pgrb2.0p25.f000 ,
> gfs.t00z.pgrb2.0p25.f006, gfs.t00z.pgrb2.0p25.f012, ...] have two 'size
> one' temporal dimensions: initial_time0_hours and forecast_time0:
>
> initial_time0_hours:   initial time of the forecast; this should be the
> same for each file
> forecast_time0: forecast time [hours offset from the initial_time0_hours];
> 0, 6, 12, ...
>
> For the gfs files you are reading, the 'initial_time0_hours' will be the
> same for all the files but the 'forecast_time0' will will differ.
>
> Try the following:
>
> %> ncl_filedump gfs.t00z.pgrb2.0p25.f006.grb2    | less
> %> ncl_filedump gfs.t00z.pgrb2.0p25.f006.grb2 -ftime    | less
> %> ncl_filedump gfs.t00z.pgrb2.0p25.f006.grb2 -itime -ftime   | less
>
> The -itime and -ftime force NCL to not consider the single element
> dimension sizes as degenerate.
>
> %> ncl_filedump -h
>
> ------
> Your situation
>
> [1]
> grib_files = systemfunc("ls gfs.t00z.pgrb2.0p25.f*") + ".grib2"
> a = addfiles(grib_files,"r")
> print( a[0] )                             ; no 'time' dimensions
>                                               ; 'time information' is
> included but are variable attributes
>
> x = a[:]->....                            ; where ... is some variable on
> your file
> print(x)                                   ; x will be 2-dimension ... no
> time dimension(s)
>                                               ; 'time information' is
> included but are attributes
> ==============
> Start over ...
>
> ... aggregating the 'forecast dimension'
>
> Read 'SingleDimensions' portion of:
>    http://www.ncl.ucar.edu/Document/Functions/Built-in/setfileoption.shtml
>
> [2]
> setfileoption("grb","SingleElementDimensions","forecast_time")
> grib_files = systemfunc("ls gfs.t00z.pgrb2.0p25.f*") + ".grib2"
> a = addfiles(grib_files,"r")
> print( a[0] )
>
> x = a[:]->...
> print(x)
>
> Cheers
>
> On Fri, Jun 30, 2017 at 4:10 PM, Rabah Hachelaf <hachelaf at sca.uqam.ca>
> wrote:
>
>> Hello,
>>
>> Why we can not concatenate or joint GFS 0.25 grib2 file
>> like in this example ?!
>> Any suggestions to solve this issue ?
>>
>> Thank you
>> Rabah
>>
>>
>>
>> grib_files = systemfunc("ls "+gfs_dir+"/gfs*") + ".grib2"
>> a = addfiles(grib_files,"r")
>>
>> ListSetType (a, "join") or ListSetType (a, "cat")
>> rain =a[:]->APCP_P8_L1_GLL0_acc
>> printVarSummary(rain)
>>
>> --------------------------------------------------
>> Variable: rain
>> Type: float
>> Total Size: 4152960 bytes
>>             1038240 values
>> Number of Dimensions: 2
>> Dimensions and sizes:   [lat_0 | 721] x [lon_0 | 1440]
>> Coordinates:
>>             lat_0: [90..-90]
>>             lon_0: [ 0..359.75]
>> Number Of Attributes: 15
>>   center :      US National Weather Service - NCEP (WMC)
>>   production_status :   Operational products
>>   long_name :   Total precipitation
>>   units :       kg m-2
>>   _FillValue :  1e+20
>>   grid_type :   Latitude/longitude
>>   parameter_discipline_and_category :   Meteorological products, Moisture
>>   parameter_template_discipline_category_number :       ( 8, 0, 1, 8 )
>>   level_type :  Ground or water surface
>>   level :        0
>>   type_of_statistical_processing :      Accumulation
>>   statistical_process_duration :        initial time to forecast time
>>   forecast_time :       6
>>   forecast_time_units : hours
>>   initial_time :        06/23/2017 (00:00)
>>
>>
>> --
>> ------------------------------
>> Cordialement,
>> Best regards,
>> Rabah Hachelaf
>>
>>
>>
>>
>>
>>
>>
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>
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