Unsurprisingly the different M-climates associated with IFS and AIFS show some discrepancies.   Broadly there is a tendency:

• for upper tails of AIFS to be warmer than IFS In mid-latitudes.
• lower tails of AIFS to be colder than IFS in northern latitudes (e.g. Arctic Canada).

This implies AIFS M-climate has a larger range than IFS M-climate.  This  difference tends to generally increase with forecast lead time.

Broadly the AIFS M-climate range is closer to the range of the observation climate than IFS M-climate, (though this is not necessarily true everywhere). 

The differing behaviour (different biases) of AIFS M-climate and AIFS M-climate can be a problem for EFI.

An extreme example from Sri Lanka.  At the station shown, both IFS and AIFS ensemble forecasts of daily mean temperature are quite similar and agree well with the observation.  But there is a striking difference between AIFS M-climate and IFS M-climate.  The AIFS M-climate is much warmer than the IFS M-climate.   The AIFS ensemble forecasts are completely lower than the corresponding AIFS M-climate - AIFS EFI is -100%.  The IFS forecast (and the AIFS forecast) is much closer to the IFS M climate -  IFS EFI is +31%.   The verifying station is reliable.

This is an extreme example of difference between the IFS M-climate and AIFS M-climate.  Although the verifying station is in a mountainous area but this does't explain but both IFS M-climate and AIFS M-climate have the same orography.

Fig5.3.6-1: An extreme example of difference between the IFS M-climate and AIFS M-climate.  Both IFS (blue) and AIFS (red) ensemble forecasts of daily mean temperature are quite similar and agree well with the observation.  The AIFS M-climate is much warmer than the IFS M-climate.   The AIFS ensemble forecasts (blue) are completely lower than the corresponding AIFS M-climate (grey) - AIFS EFI is -100%.  The IFS forecast (red), and the AIFS forecast (blue) is much closer to the IFS M climate (black) -  IFS EFI is +31%.