Divergence / Vorticity (uv2dv problem)

Dear all,

I have been trying to figure out how to get divergence and vorticity from U-wind and V-wind. I read that in the documentation for uv2dv the data need to be in a regular gaussian grid and with the variable names of u and v. But I haven't been able to download my NetCDF files (ERA5 and CORDEX) in a regular gaussian grid. If I download my data as GRIB with a regular gaussian grid, then I can't rename the variables to u and v.

I tried to convert the grib file (that was in a regular gaussian grid) to netCDF using: cdo -f nc copy <input grib> <output netcdf> but then the output.nc was 'converted' to lat_lon.

Thanks in advance for the help you can provide me.

Best,

Ana

PD: I couldn't upload the file, because it was too heavy.

Replies (4)

RE: Divergence / Vorticity (uv2dv problem) - Added by Karin Meier-Fleischer over 4 years ago

Hi Ana,

without the data it's difficult to help.

Try

cdo -f nc -copy -setgridtype,regular infile.grb outfile.nc

-Karin

RE: Divergence / Vorticity (uv2dv problem) - Added by Ana Aguilar over 4 years ago

Thanks Karin for your fast response.

I tried your approach, but it didn't work. I got again the in grid type: lat_lon. But I continue and changed the names using and try to get the divergence/vorticity:

cdo -f nc -copy -setgridtype,regular uv_N320.grb uv_N320.nc
cdo chname,var165,u,var166,v uv_N320.nc uv.nc
cdo uv2dv uv.nc dv.nc

And then I got: U-wind and V-wind not found.

This time I am attaching one month of data in the three possible formats/grids that I can obtain the data.

Thanks again,

Ana

Download all files

uv_F320.grb (18.6 MB) uv_F320.grb	in full (or regular) Gaussian grid N320
uv.nc (23.5 MB) uv.nc	lon_lat netCDF
uv_N320.grb (18.9 MB) uv_N320.grb	ECMWF original reduced Gaussian grid

RE: Divergence / Vorticity (uv2dv problem) - Added by Uwe Schulzweida over 4 years ago

For GRIB files you have to change the code numbers:

cdo uv2dv -chcode,165,131,166,132 -setgridtype,regular uv_N320.grb dv.grb

Unfortunately this won't help you, because the function uv2dv needs the input data on a global Gaussian grid. The global spectral transformation used does not work for regional data, sorry.

RE: Divergence / Vorticity (uv2dv problem) - Added by Ana Aguilar over 4 years ago

Dear Uwe,

Thanks for your response.

For ERA5 data I can get the global, but when I have to move to CORDEX RCMs this will not be possible. But thanks for the information. I can move on to try other solutions.

Thanks,

Ana

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