Simulation and prediction of the Southern Annular Mode and its influence on Australian intra-seasonal climate in POAMA
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- Marshall, A.G., Hudson, D., Wheeler, M.C. et al. Clim Dyn (2012) 38: 2483. doi:10.1007/s00382-011-1140-z
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We assess the ability of the Predictive Ocean Atmosphere Model for Australia (POAMA) to simulate and predict the Southern Annular Mode (SAM) and its influence on Australian intra-seasonal climate using a 27-year hindcast dataset. The analysis consists of three stages: (1) prediction of the SAM, (2) simulation of SAM climate anomalies over Australia, and (3) prediction of Australian climate anomalies in association with the SAM. POAMA achieves skilful prediction of the SAM index for lead times out to about 2 weeks with little skill seen beyond 3 weeks when calculated over all hindcast start months; the inherent strong persistence of the SAM appears to be a key factor for its extended-range predictability in a dynamical forecast model. POAMA also simulates SAM climate anomalies over Australia reasonably well despite notable biases in its representation of the SAM to the south and east of the continent. The model reproduces Australian rainfall anomalies most effectively throughout June–November, and least effectively throughout March–May. Skilful prediction of the SAM index, together with realistic simulation of SAM climate anomalies over Australia, translates into more skilful forecasts of rainfall and maximum temperature at intra-seasonal timescales during austral winter and spring. When the SAM is strong in the initial conditions, there is higher skill in forecasting rainfall anomalies over eastern Australia and maximum temperature anomalies over most of the continent during June–November at lead times of 2–3 weeks, compared with when the SAM is weak. The SAM thus contributes to intra-seasonal prediction skill in the Australian region in POAMA.