资源环境科技发展态势分析平台

The skill in predicting intraseasonal characteristics of synoptic type occurrences at the seasonal time scale over the all-year rainfall region of South Africa (35 degrees-33 degrees S and 21 degrees-27 degrees E) is assessed by utilizing an ensemble of simulations performed using the GloSea5 coupled ocean-atmosphere model. Hindcasts of daily sea-level pressure fields of 14 austral spring [September-October-November (SON)] and summer [December-January-February (DJF)] seasons, initialized in August and November, respectively, are analysed. The skill assessment is achieved through the use of self-organizing maps. Deterministic and probabilistic assessment of synoptic type frequency forecasts indicate that intraseasonal circulation variability over the Cape south coast region is marginally predictable at seasonal time scales, more so during SON than DJF. In particular, the results obtained demonstrate that there is potential for the skillful seasonal prediction of the anomalous frequency of occurrence of high-impact rainfall events associated with cut-off lows within SON seasons.