SCIENCE OF SEASONAL CLIMATE PREDICTION

The scientific basis of seasonal climate prediction
by Scott Power, Bureau of Meteorology

Dr Scott Power is a Principal Research Scientist in the Bureau of Meteorology Research Centre. He led the development of the Bureau of Meteorology’s first coupled atmosphere-ocean climate model, which was used to perform Australia’s first transient global warming experiment. He then led the development of the Bureau’s second model, which was subsequently used to conduct Australia’s first climate model-based seasonal to interannual climate predictions. He has published extensively in the international literature on El Niño, climate change, climate prediction and climate services. He has worked in the Bureau of Meteorology for 15 years (as Head of Operational Climate Monitoring and Prediction, as Acting Head National Climate Centre, and as a Research Scientist).

There is a huge body of evidence collectively indicating that seasonal climate anomalies linked to the El Niño-Southern Oscillation (ENSO) phenomenon can be predicted to some extent. The evidence from:

• observational analyses,
• mathematical models representing the physical processes underpinning climate variability (‘climate models’),
• theoretical considerations, and from
• assessments of ENSO-based prediction schemes on independent data, will be reviewed here.

We will begin by reviewing observational analyses that provide insights into the cause and predictability of ENSO, and the impact that ENSO has on Australia. We will see that there are robust associations between ENSO and both synchronous and subsequent changes in climate generally, and Australian climate in particular. The lagged associations underpin predictability.

We will then turn our attention to the dynamics and predictability of ENSO itself. We will briefly review the progress that has been made in our understanding of ENSO, and the truly remarkable progress that has been made in our ability to simulate ENSO over the past twenty years. We will see that ENSO owes its existence to instabilities that exist naturally in the coupled atmosphereocean climate system and that predictability is also a feature of ENSO in mathematical models of the earth’s climate.

Theoretical models used to encapsulate physical processes thought crucial for ENSO dynamics will then be described. The predictability of these simplified systems will be examined.

We will finish our review of the evidence underpinning predictability of seasonal climate anomalies linked to ENSO by briefly describing the success that ENSO-based forecast systems have had in predicting climate variability. A final comment on sources of predictability other than ENSO will be made.