西太平洋副热带高压东西位置异常与华北夏季酷暑

文中研究了副热带高压 (副高 )东西位置异常与中国东部地区夏季气温的关系。发现两者之间有很高的正相关 ,当西太平洋副高偏西时 ,大片的北方地区气温会降低 ;而当副高偏东时 ,该地区的气温将偏高。西太平洋副高东西位置的异常对应着亚洲太平洋地区的长波位置和强度的很大变化 ,从而影响到中国北方地区的气温。更重要的是 ,副高西端位移所产生的扰动还会以波列的形式向极地和北美方向传播 ,从而从更大的范围内影响西风带环流。对 2 0 0 2年夏季中国北方出现的持续高温天气进行了分析。该年夏季副高持续偏东。西风带大槽也处于偏东的位置。西部的大陆副高东移扩展 ,与槽后的高压脊打通 ,造成该地区的持续高温。副高的东西位置决定了季风气流 (也就是水汽的主要通道 )的北向转折的路径。当副高偏东时 ,向北折向的位置随之东移 ,东亚大陆的水汽供应变为负距平 ,特别是中国北方地区 ,变得十分干燥。引起中国北方高温的直接系统是大陆高压中的极强的下沉气流 ,副高的偏东位置为大陆副高的东进和加强提供了大尺度的背景条件

RELATIONSHIP BETWEEN THE ANOMALY LONGITUDINAL POSITION OF SUBTROPICAL HIGH IN THE WESTERN PACIFIC AND SEVERE HOT WEATHER IN NORTH CHINA IN SUMMER

There exists a good relationship between the longitudinal position of the subtropical high in the western Pacific and the temperature in the north China in summertime. A remarkable positive correlation region with a value more than 0.6 at the center indicates that when the subtropical high moves eastward, the temperature in north China would increase and vise versa. The anomalous longitudinal position of the subtropical high is closely associated with the variation of the long wave pattern in the westerlies, hence influences the temperature of north China. Moreover, the perturbation resulting from the change of the longitudinal position of the subtropical high would propagate, as a wave train, northward to the polar region then the North America thus influence the westerlies in a much wider range. A long spell of hot and dry weather in the year of 2002 summer in north China is analyzed. The position of the subtropical high in that summer consistently locates to the east. The continental subtropical high in the west extends eastward to merge with the ridge in the westerlies and covering north China area, bringing about a high temperature there. The longitudinal position of the subtropical high fixes to the northward turning point and the track of the monsoon current , which would also be the path of the water vapor transfer. A eastward displacement of the subtropical high would lead to the eastward shift of the water vapor channel, away from the eastern Asian continent. Therefore, the supply of water vapor would become very poor there, especially in north China, resulting in a very dry weather. The high temperature in this case is directly caused by the intense descending current in the continental subtropical high.