Description about ensemble members ERA5

Datasets and Usage C3S - Datasets and Usage
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1

Dear all, I have a question about ERA5 EDA ensemble members mean and Spread.

When downloading those files in NetCDF experimental format from CDS (Copernicus data storage) I can see that the members are identified by a number ranging from 0 to 9.

If I well understand there is 9 members and an unperturbed control. My question is how can I identify the control ? Is it the number 0 in the ranging?

Also how is calculated the ensemble mean? Is it the mean of the 10 members or the mean of the 9 members excluding the control member?


Thanks for your help.

Thomas

2

Hi,

please have a look at the following link:

ERA5: data documentation#Ensemblemeansandstandarddeviations

Regards

Michela

3

Hi Michela, 


Thanks for your help and the link. But I can't find all the information that I am looking for. 

I understand that "Both these quantities are calculated from all the 10-members (i.e., including the control).", so ok, it is the mean and standard deviation ("spread") of the 10 members, including control. 

However I still don't know how to identify the control member (number"0"?) when downloading Ensemble members. Also when I do the mean or stdev of the 10 members (manual calculation from the 10 members) at a specific time and lon/lat I don't get exacly the same value as the mean or standard deviation directly downloaded from CDS.

So I am wondering how are calculated those values. 


Best regards

Thomas