资源环境科技发展态势分析平台

We assess the ability of the Bureau of Meteorology's new ACCESS-S1 dynamical forecast system to predict the MJO using retrospective forecasts for the period 1990-2012. Compared to the benchmark POAMA-2 system, ACCESS-S1 demonstrates improved skill in predicting the ensemble mean bivariate RMM index by about 4days lead time in austral summer and 5days in boreal summer. Probabilistic forecast scores further demonstrate improved skill in predicting MJO amplitude by at least 7days, and MJO phase by about 9days. However, the ensemble from ACCESS-S1 for the MJO is underdispersed, indicating further gains in forecast skill can still be achieved. Improvements in the regional depiction of MJO rainfall in ACCESS-S1 over POAMA-2 include a more realistic southward extension of austral summer rainfall over Northern Australia, and a better overall spatial distribution and eastward extension of boreal summer rainfall over the tropical Indo-Pacific region. Both models depict well the northward propagation of boreal summer rainfall over the Indian Ocean warm pool. Overall, ACCESS-S1 simulates the MJO signature in global rainfall at least as well as, if not better than, POAMA-2.