Timeseries extraction from grib files

Added by Gerhard Totschnig over 13 years ago

Dear CDO users,
I have hourly data of the wind speeds over Europe in the grib1 format(lambert grid).
For each hour the data is in a seperate grib file (87600 hourly files = 10 Years) covering whole europe.
I want to extract wind speed time series data form these files for all grid 150000 points.
Its 1 TB of data.

How to do it?
- I could use the CDO cat comand to stack the hourly grip files together.
- And then split the large file covering europe into 1000 smaller grip files of 1GB covering smaller areas. To make it easier to handle?
Which comand can I use for this splitting?
- And then somehow exctract the timseries for each specific grid point for data calculations (weibull statistics and other)
How can I exctract a timseries form the stacked grip files(generated by cat as said before)?
Will the themporal ordering be correct?

Or do you have some other suggestions on how to extract the timeseries from this data?

Thanks a lot!!
Gerhard

Replies (2)

RE: Timeseries extraction from grib files - Added by Uwe Schulzweida over 13 years ago

Dear Gerhard,
I think your suggestion is the most efficient way to process your data files.

You can use CDO cat or UNIX cat to stack the hourly GRIB files together.
(It could be a problem to do it in one step (87600 files) because of the limitation of the command line length)
```
  cdo cat smallfiles*.grb  bigfile.grb
```
Use selindexbox for splitting the horizontal domains. Your have to convert the lambert projection to geographical coordinates. Use netCDF to store the geographical coordinates correctly. Here is an example for a grid with nlon=1500 and nlat=1000:
```
 LOOP J=1,1000
   cdo -f nc selindexbox,1,1500,J,J -setgridtype,curvilinear  bigfile.grb  domain_J.nc
```

Then you can extract the timeseries with:

 LOOP J=1,1000
 LOOP I=1,1500
   cdo -f grb selindexbox,I,I,1,1 domain_J.nc timeseries_IJ.grb

Best regards,
Uwe

RE: Timeseries extraction from grib files - Added by Gerhard Totschnig over 13 years ago

Thank You!
We are now trying to implement this.
Best greetings Gerhard

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