Peter van Rensch: The stability of Australian seasonal rainfall forecasts in ACCESS-S2
Seasonal forecasts of Australian rainfall at times experience a notable change as lead times shorten, i.e., as forecasts are initialised closer to the target date. Making plans or decisions using forecasts during these times are particularly difficult as you’re effectively planning for a moving target.
In this work, we examined the ACCESS-S2 hindcast dataset to explore the stability of Australian rainfall forecasts in different seasons, regions and over time. We also assessed physical features that were common to variations in forecast stability.
We found rainfall forecasts for the spring season are typically the most stable in eastern Australia. Some La Niña and negative Indian Ocean Dipole events showed increased forecasts stability for eastern Australia rainfall, but it was not a common feature for all those events during 1981-2018. The stability of eastern Australian rainfall forecasts was also associated with the stability of sea surface temperature forecasts to the north and northeast of Australia during the spring months.
These findings will be of interest to seasonal forecast users, and the ACCESS community who care about physical features that affect Australian climate in the model.