南方极端雨雪冰冻过程东亚冬季风环流特征及与EINino/La Nina事件的关系

Circulation Characteristic of East Asia Winter Monsoon of Extremely Low Temperature and Snow-ice Weather in Southern China and Its correlation with EI Nino/La Nina events

根据南方极端雨雪冰冻过程的定义,确定1964、1969、1977、1984、2008年的强降水、降温过程为南方极端雨雪冰冻过程。对发生在EINino/LaNina事件之后的南方极端雨雪冰冻过程的分析表明:EINino/LaNina是造成中国东部1月降水异常的一个主要原因,但不能解释气温异常。前一年秋季热带中东太平洋发生暖事件时,利于1月降水黄河流域偏少,长江以南偏多,而发生冷事件时,则利于1月降水黄河流域偏多,长江以南偏少。南方极端雨雪冰冻过程期间对流层低层和高层矢量风距平场表明:发生月对流层低层在1977、1984年南方极端雨雪冰冻过程中,北太平洋出现大范围气旋环流异常,中国长江中下游及以南至菲律宾出现气旋环流异常,长江中下游及以南为东风距平控制。1964、1969、2008年北太平洋出现大范围反气旋环流异常,中国长江中下游及以南出现大片偏南风距平。其共同点是均存在洋面上空暖湿空气向长江中下游及以南地区的输送。南方极端雨雪冰冻过程的前一年11月北太平洋无一例外地出现大范围气旋环流异常,发生月对流层高层副热带西风急流在中国黄海至日本一带较常年都有不同程度的偏强。

Some selected heavy rain and detemperature events during 1964、1969、1977、1984、2008 are deemed as extremely low temperature and snow-ice weather in Southern China according to its definition. Through the contrast analysis of those low temperature and snow-ice weather events during 1969、1977、2008 occurred after EI Nino/La Nina events, it is revealed that EI Nino/La Nina event is a major cause of rainfall anomaly over the eastern China in January, while it has no business with temperature anomaly. When warm events take place in the middle and eastern of equatorial Pacific during the last autumn, it facilitates to have less rainfall over the Yellow River valley while more rainfall over the south of the Yangtze River in January of the following year. And when cold events take place, it leads to reverse result. Wind departure field during extremely low temperature and snow-ice weather over the Southern China shows that as for low convective layer in the occurring month of 1977、 1984, large-scale anomalous cyclonic circulation is observed in the north of Pacific, anomalous cyclonic circulation is observed from the middle and lower reaches of the Yangtze River southerly to Philippines, easterly anomalies were observed in the middle and lower reaches of the Yangtze River and the area south to it. While in 1964、1969、2008 large scale anomalous anticyclonic circulation is observed in the north Pacific, southerly anomalies are observed in the middle and lower reaches of the Yangtze River and the area south to it. It is common that there is moist air transportation from over the sea to the middle and lower reaches of the Yangtze River and the area south to it. In the last November of all the years of 1964、1969、1977、1984、2008, large scale anomalous cyclonic circulations are observed in the north Pacific. In the occurring month of these years, upper-level subtropical westerly jet stream is stronger to some extent from the Huanghai Sea of China to Japan.