2012年汛期气候预测的先兆信号和应用

Overview of Precursory Signals of Seasonal Climate Prediction and Its Application in Summer 2012

本文基于动力、统计预测方法提供的信息回顾了发布2012年汛期预测时考虑的先兆信号。2012年前期拉尼娜事件在冬季达到盛期、冬季北极海冰异常偏少、南极涛动强度是自1979年以来次强、青藏高原积雪偏多但气温偏高,这些特征对后期夏季风有明显影响。通过分析归纳,国家气候中心比较准确地预测了东亚夏季风偏强、我国夏季多雨带偏北、大部分地区气温偏高,6—8月热带气旋活跃的总体特征,以及南海夏季风爆发偏早、长江中下游梅雨偏少、华北雨季提前且雨量偏多的季节内过程演变趋势。最后讨论了汛期气候预测的可预报性和困难,提出今后需要深入研究的科学问题和业务应用问题。

In this paper, the possible predictors of the summer climate in 2012 in China are reviewed based on both the dynamic forecasts and the statistical predictions. In the winter of 2011/2012, the La Nina event reaches its peak, the Arctic sea ice area is much less than its climatology, the intensity of the Ant- arctic oscillation is the second higher since 1979, and the snow cover over the Tibetan Plateau is more but warmer than normal. Under the influence of these abnormal features, the East Asian monsoon becomes stronger in the following summer and the main rainfall belt locates in northern China. These basic charac- teristics have been captured successfully in the prediction issued by the National Climate Centre of CMA in early April. Besides, the air temperatures in most regions in the country are warmer, the tropical cyclones are more active in June--August, the onset date of the South China Sea summer monsoon is earlier, the Chinese Meiyu along the middle-low reaches of Yangtze River Valley is less, and the rainfall in North Chi- na is earlier and more. In the last part of this paper, the predictability and the difficulty of the seasonal rainfall forecast are discussed, and the scientific questions together with the operational problems are also listed.