WAMSI - Fremantle Sea Level
The Leeuwin Current flows poleward against the prevailing winds and transports warm-fresh tropical water southward along the west coast WA, which has a great impact on local climate and ecosystems. Variations of the current are tightly tied to El Niño/La Niña (weak during El Niño and strong during La Niña). The Current can be monitored by the sea level anomaly at Fremantle, with high sea level implying a stronger current. Skilful seasonal prediction of the Leeuwin Current to 9-month lead time is achieved by empirical downscaling of dynamical coupled model forecasts of El Niño from POAMA seasonal forecast system as described in Hendon and Wang (2009).
Forecast of the anomaly of sea level at Fremantle using the prediction of the Nino34 SST index from the POAMA-2 forecast system together with the observed anomaly of Fremantle sea level at the initial forecast time. Because the Fremantle sea level observation is delayed by at least 2 months, the most recent forecast has to use the sea level observation that is lagged in time. The typical lag is 2 months. In the display, the heavy green curve is the observed Fremantle sea level anomaly up to the most recently available observation, the thin colored curves are the individual forecasts using each of the 30 members of forecasts of Nino34 SST from POAMA and the heavy light green curve is the ensemble mean forecast. The spread of the forecast plume gives some measure of forecast uncertainty.
Hindcast skill of the simplified forecast scheme, including the impact of the delay in obtaining the Fremantle sea level observation, was assessed for period 1985 to 2005 based on the 30 member ensemble of POAMA-2 forecasts that are initialized on the 1st of each month. In realtime, the 30 member ensemble of forecasts is available by the 5th of each month.
The Western Australia Marine Science Institution (WAMSI) is a collaboration of State, Federal, industry and acedemic organisations working together to provide independant marine research.