西北太平洋热带气旋活动影响区域大尺度环流的数值模拟研究

The impact of tropical cyclone activities over the western North Pacific on the large-scale regional circulation:a numerical investigation

本文利用"模式手术"方法研究了西北太平洋热带气旋(TC)对东亚—西北太平洋区域大尺度环流的影响.结果表明,夏季频繁的西北太平洋TC活动导致东亚夏季风增强,季风槽加深;西太平洋副热带高压东退,位置偏北;东亚副热带高空急流强度增强,北太平洋(东亚大陆)上急流轴偏北(偏南);热带地区(副热带地区)的对流层中低层出现异常上升气流(下沉气流),并且从低纬向高纬呈现异常上升气流和异常下沉气流交替分布特征.在中国东南沿海,TC降水导致夏季降水量明显增加;而在长江中下游和华北地区,TC活动引起的异常下沉气流使夏季降水量显著减少.因此,夏季西北太平洋TC活动对东亚—西北太平洋区域气候有显著影响.

The impact of tropical cyclone (TC) activities over the western North Pacific on the East Asia-western North Pacific large-scale regional circulation is investigated by use of the "modeling surgery" method. Our results show that the summertime frequent TC activities over the western North Pacific strengthen the East Asian summer monsoon and deepen the monsoon trough. Meanwhile,the Western Pacific subtropical high retreats further eastward and shifts further northward. Moreover,the East Asian subtropical upper-level jet intensifies,with the northward (southward) shift of the jet axis over the North Pacific (the East Asia). The abnormal ascending motion (descending motion) in the middle and lower troposphere induced by TC activities occurs over the tropics (subtropics). Furthermore,the abnormal ascending flows and the abnormal descending flows alternate from the low latitudes to high latitudes. As a result,frequent TC activities can bring abundant precipitation to coastal regions of the southeastern China,leading to more precipitation there in summer. However,in the lower and middle reaches of the Yangtze River valley and North China,the summertime precipitation decreases due to the abnormal descending motion induced by TC activities. Therefore,the East Asia-western North Pacific regional climate is significantly affected by the summertime TC activities over the western North Pacific.