东亚寒潮活动对下游爆发性气旋生成的影响

THE INFLUENCE OF THE ACTIVITY OF COLD WAVE IN EAST ASIA ON THE EXPLOSIVE CYCLONE AT ITS DOWN STREAM

本文研究了东亚寒潮过程与下游爆发性气旋之间的关系。通过对一个强寒潮过程及随后在西北太平洋上爆发性气旋生成的个例分析发现,寒潮过程相伴随的大环流调整给下游气旋猛烈发展提供了极好的背景条件。当超长波槽与长波槽耦合加深时,槽前气旋迅速发展。大槽的加深使高空急流不断加速,大风区向低层扩展。出口区的次级环流也随着急流的加强而加强,它促使北侧低层气旋发展。对93次爆发性气旋作统计分析进一步证实了上述结论。绝大多数过程皆伴有上游的强冷高压活动。高压中心越强相应的爆发气旋也越强,甚至可以发生连续的爆发。绝大多数爆发性气旋发生在超长波槽前,强高空急流出口区的向极侧。

A case study indicates that the circulation adjustment associated with the strong cold wave provides a favourable background for the explosive development of the cyclone. When the coupling of ultralong and long wave troughs occurs in the coast of east Asia, the cyclone beneath the southwest current of the trough will develop rapidly. The deepening of the trough accelarates the upper level jet obviously. Then the area of the jet stream expands downwards. The secondary circulation around the exit area of the jet strengthens with the speeding up the jet, which tends to faster the development of the cyclone. Most explosive cyclones occur ahead of large-scale major trough at the north fringe of the exit area of jet.