Hindcasts

A set of parallel hindcasts are requested from stratosphere resolving and stratosphere non-resolving models. A stratosphere resolving model is defined here to have:
- A domain extending to 1hPa (~50km) or higher
- At least 15 model levels between the tropopause and 1hPa/50km
The use of existing HFP data as the non-stratosphere resolving hindcasts is welcomed. Either coupled ocean-atmosphere model or two-tier forecasts are welcome.

Atmospheric initial conditions are at the choice of the participant but must not include any information from the future.

Land initial conditions are at the choice of the participant but must not include any information from the future.
- Option 1: use "reanalysis" land surface data modified to your model (recommended)
- Option 2: use model climatologies from an AMIP run.

SST and sea-ice initial conditions - SST must not contain information from the future with respect to the forecast
- Option 1: persist the observed SSTA anomaly from the month preceding the forecast period (i.e., this anomaly is added to the climatological seasonal cycle of SST's)
- Option 2: statistical or other objective forecast of SSTA which is not developed with nor makes use of future information (e.g. climatology, relaxation of anomalies toward zero with some time scale, other statistical forecast, anomalies from an ocean model initialized and run separately, etc.)

Sea ice initial conditions: based on the associated sea ice data but containing no future information.