index calculate
Added by Noelia Otero about 11 years ago
Hi!
I am trying to calculate a WAMI index, (as the difference between the wind modulus at 925hPa and the zonal wind at 200 hPa).
but I have a question about the result (because I'm merging two pressure level), so would it be correct to do?
cdo masklonlatbox,-30,50,7.5,0 -sellevel,92500 mod_meanJAS.nc mod925.nc
cdo masklonlatbox,-30,50,7.5,0 -sellevel,20000 ua_meanJAS.nc ua200.nc
cdo sub mod925.nc -timmean mod925.nc anom925.nc
cdo div anom925.nc -timstd anom925.nc anom925std.nc
cdo sub ua200.nc -timmean ua200.nc anom200.nc
cdo div anom200.nc -timstd anom200.nc anom200std.nc
cdo -merge anom925std.nc anom200std.nc temp.nc
cdo expr , ’WAMI=mod - ua;' temp.nc wami.nc
when I open the wami.nc file, it contains the 92500 level....(I 've just to started whit cdo and I don't totally understand if this calculate would be ok ).
Many thanks for your help!
Replies (1)
RE: index calculate - Added by Jaison-Thomas Ambadan about 11 years ago
Hi,
when I open the wami.nc file, it contains the 92500 level...
I'm not sure if I understood correctly - I think your CDO operations are correct. If you simply inter-change the order of your input files while "merge"-ing and then apply "cdo expr,'WAMI=mod-ua;' temp.nc wami.nc, you can see that the output level is 20000. CDO uses the level info from the input file/variable for the output variable/info - it's just a meta info for the output file.
If you would like to change the level info, then use the "setlevel" operator
Cheers,
J