Bias error
Added by ray kettaren about 2 years ago
Hi everyone!
I need help if maybe someone has ever done it before. I want to make a bias error ((Observation-ModelProjection)/Observation)*100.
I wanna make it in percentage. All the data are already mean value so no time step. This is my command:
cdo -sub djf_eobs_rr_newdom.nc pr_djf.nc sub_bias_pr.nc
cdo div sub_bias_pr.nc djf_eobs_rr_newdom.nc bias_pr_djf.nc
I dont know why but it seems incorrect.
Thank you!
djf_eobs_rr_newdom.nc (361 KB) djf_eobs_rr_newdom.nc | |||
pr_djf.nc (701 KB) pr_djf.nc |
Replies (4)
RE: Bias error - Added by ray kettaren about 2 years ago
I have already corrected it but it seems still unrealistic value for the precipitation. This are the commands:
First I substract my ensemble RCM projection (pr_djf.nc) by the E-OBS data (djf_rr_newdom.nc).
After that I'll divide the result with the E-OBS again and multiply it with 100 for making it in percentage.
cdo sub pr_djf.nc djf_eobs_rr_newdom.nc sub_bias_pr.nc
cdo mulc,100 -div sub_bias_pr.nc djf_eobs_rr_newdom.nc bias_pr_djf.nc
The values are not realistic.If anyone can help please ! Thank you
RE: Bias error - Added by Ralf Mueller about 2 years ago
hm, I am nor sure if both physical quantities are comparable
djf_eobs_rr_newdom.nc
holds an amount of rain in mmpr_djf.nc
hold a precipitation flux in mm per 450sec
I can see in the history that you multiplied this by the daylength in seconds (-mulc,86400
) and reset the unit.
So all-in-all the values are not reliable for me. Further more you show in your table some error numbers which cannot be checked with files you uploaded. your uploads have only a single filestep whereas you show errors for different seasons.
In case your error number are in %
these number might be fine. I cannot check the original values myself, so it;s very hard to comment on that
cheers
ralf
RE: Bias error - Added by ray kettaren about 2 years ago
Hello Ralf!
Thank you for the response. The pr_djf.nc data is from 5 ensemble RCM simulation. It is daily data that's why I multiply it with 86400.
But my question is it in mm per 450sec, how can I convert it into mm/daily?
Thank you very much
RE: Bias error - Added by Ralf Mueller about 2 years ago
In essence you best check the simulation code or ask the developers if possible. I see two options
- the unit is correct (flux in mm per 450sec)
- in this case data can a be instantaneous values: then your are lost because only 450 sec of the whole day is covered or
- it is a mean values: then you might multiply it with 192 (=86400/450) to get to the complete flux of the day
- the unit is not correct
- the values are already accumulated for a day and someone forgot about correcting the unit: in that case you can use the plain values for further daily analysis
- the rest is too much guessing - go back and check the model
best wishes
ralf