Re: read ECHAM5 (Gaussian Latitude/Longitude Grid)

Hello Mehmet,

I don't know what is happening in your case. I'm not an
expert in either NCL or CDO. Also, in a previous message
someone has told (I think it was Dennis) that there was
some issue with your files related to the initial warning
message you got - warning:GdsGAGrid:

I can tell you that I've used CDO to remap ECHAM5 data
(and other models) from Gaussian grid (T63) to the fixed
grid (2.5 x 2.5) and it works fine. This remapping (or
regridding) can also be done with NCL using for example
function "g2fsh", but only in the case of global data. I
have compared the results of remapping global data from
Gaussian grids to the fixed grid (2.5 x 2.5) using both
CDO (that uses a conservative remapping scheme) and NCL
(uses spherical harmonics) and they are fairly similar.

Carlos

Em Thu, 01 Apr 2010 10:44:29 +0200
  Mehmet Coskun <mehmet.coskun@ufz.de> escreveu:
> Hello Carlos,
>
> Thank you,
>
> cdo works well after converting netcdf I think I got
>values, but
> attribute names were totally changed ,
>
> for example when I read grb file with NCL
>
> Total Size: 64 bytes
> 8 values
> Number of Dimensions: 1
> Dimensions and sizes: [8]
> Coordinates:
> (0) forecast_time0
> (1) g4_lon_2
> (2) g4_lat_1
> (3) initial_time3
> (4) initial_time3_encoded
> (5) initial_time3_hours
> (6) A_PCP_GDS4_SFC_10
> (7) A_PCP_GDS4_SFC
>
> But after converting netcdf attributes names;
>
> Total Size: 32 bytes
> 4 values
> Number of Dimensions: 1
> Dimensions and sizes: [4]
> Coordinates:
> (0) prec
> (1) time
> (2) lat
> (3) lon
>
>
> dimension of time variables increase from 2884 to 2892
>
> netcdf: time(2892) from 15 to 88008.5,
> Dimensions and sizes: [time | 2892]
> Coordinates:
> time: [ 15..88008.5]
> Number Of Attributes: 2
> units : days since 1860-01-01 00:00:00
> calendar : proleptic_gregorian
>
> but
> grib: initial_time3_encoded(2884) from 1860091600 to
>2100121612
>
> grid type Gaussian Latitude/Longitude Grid (24 x 58),
>should I remap this grid, does it not contain same
>geographic coordinate which meteorological station has,
>
> thank you
>
>
> Best regard
>
> mehmet
>
>
>
>
>
> Carlos A. F. Marques wrote:
>> Hi Mehmet,
>>
>> You can easily remap the ECHAM5 Gaussian grid to a fixed
>>grid with the
>> Climate Data Operators (CDO), freely available at:
>> http://www.mpimet.mpg.de/fileadmin/software/cdo/
>>
>> Example: Using CDO to remap data from Gaussian grid to a
>>fixed grid
>> (say, 2.5 by 2.5 => r144x73).
>>
>> First you can convert the grib files to netCDF as:
>>
>> cdo -f nc copy ECHAM5_in.grb ECHAM5_in.nc
>>
>>
>> For the remapping use:
>>
>> cdo gencon,r144x73, ECHAM5_in.nc weights.nc
>> cdo remap,r144x73,weights.nc ECHAM5_in.nc ECHAM5_out.nc
>>
>> The data in ECHAM5_out.nc will be in a 2.5 by 2.5 fixed
>>grid.
>>
>> Good luck
>>
>> Carlos
>>
>>
>>
>> Em Wed, 31 Mar 2010 17:07:34 +0200
>> Mehmet Coskun <mehmet.coskun@ufz.de> escreveu:
>>> Hi,
>>> I tried to read ECHAM5 grib file which is Gaussian
>>>Latitude/Longitude
>>> Grid , I got a warning message;
>>>
>>> !! warning:GdsGAGrid: Gaussian latitude coordinate array
>>>is partially
>>> or wholly undefined
>>>
>>>
>>> Also my lattitute are not geographic latitute, How can I
>>>convert
>>> Gaussian Latitude/Longitude Grid to regular grid?
>>>
>>> 1.440558e+32
>>> 8.547921e-44
>>> 2.224632e-37
>>> 0
>>> 2.224708e-37
>>> 0
>>> 0
>>> 0
>>> 0
>>> 0
>>> 0
>>> 0
>>> 2.224697e-37
>>> 0
>>> 0
>>> 0
>>> 0
>>> 0
>>> 6.866362e-44
>>> 0
>>> 1.853472e-37
>>> 0
>>> 2.22465e-37
>>> 0
>>>
>>> thanks
>>>
>>> Best regard
>>>
>>> mehmet
>>
>> _________________________________
>> Physics Department
>> University of Aveiro.
>> Campus Universitário de Santiago
>> 3810-193 Aveiro.
>> Portugal
>> _________________________________
>

_________________________________
Physics Department
University of Aveiro.
Campus Universitário de Santiago
3810-193 Aveiro.
Portugal
_________________________________
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Received on Thu Apr 1 03:53:46 2010