Please note that numbering/ordering does not imply priority. Recent updates are shown in green. Greyed out means no longer current, but these issues can be relevant when examining archived forecasts.
Any enquiries related to the content of this page should be raised via the ECMWF Support Portal (mentioning the "Known AIFS ENS forecasting issues page").
Topic / title | Description | Related activities / comments |
|---|---|---|
General issues | ||
| G1. Artefacts at long lead times | At long lead times, particularly beyond 10 days, unphysical artefacts can emerge in the model, particularly under areas of high elevation. These are particularly visible for mean sea level pressure and temperature at 1000hPa.
1000hPa temperature artefact beneath the surface of the Andes at 360 hours into the forecast. | Investigations are underway to understand and fix this issue in future cycles. |
| G2. Over-dispersion | On average, ensemble standard deviation is larger than the RMSE of the ensemble mean for a range of variables.
Spread and error evolution for 850hPa temperature showing over-dispersion between days 2 and 8. | IFS-ENS and AIFS-CRPS share the same initial condition perturbation amplitudes. Re-scaling is under investigation. |
Precipitation | ||
| P1. Very small values in dry regions | Very small values (e.g. <0.1mm/6h) of precipitation can occur in arid regions, in what appears to be an unphysical way. This is particularly noticeable when looking at long accumulation periods.
240h accumulated precipitation | Investigations are underway to understand and fix this issue in future cycles. |
Clouds | ||
| C1. Reduced spatial resolution in cloud fields | In general, AIFS ENS significantly improves on the representation of fine scale features compared with AIFS Single. However cloud fields display features at a lower spatial resolution than many of the other fields predicted by the AIFS ENS. Features have a resolution closer to the 1-degree resolution of the model processor grid. T+0 fields do not show this behaviour because they are imported from the IFS initialisation.
Example of reduced spatial resolution for cloud fields over Europe in an AIFS ENS forecast.
Energy spectra for total cloud cover in AIFS ENS at day 1 (blue line), showing reduced energy at small scales (=high wavenumbers, on the right of the plot) compared with the IFS analysis (black). Energy can be loosely interpreted as frequency of occurrence. | Investigations are underway to understand and fix this issue in future cycles. |
