摘要
为了研究东亚夏季风北界与我国东部夏季降水异常的关系,本文利用夏季850 hPa上20°N以北105°～125°E之间平均南风风速2 m/s所在的纬度,定义了一个新的东亚夏季风北界指数。初步分析表明：东亚夏季风北界在1976年之前（含1976年）位置偏北,而1976年之后位置偏南,具有明显的年代际变化,较好地反映了我国东部夏季降水异常分布型的变化。对应于东亚夏季风北界的异常,东亚夏季风强度、西北太平洋副热带高压位置与面积、亚洲大陆热低压等也发生了相应的变化,它们之间的关系如下：东亚夏季风北界位置偏北（南）时,对流层低层亚洲大陆热低压偏强（弱）,东亚夏季风偏强（弱）,西北太平洋副热带高压位置偏北（南）、面积偏小（大）,南亚高压偏弱（强）,长江中下游地区气流以下沉（上升）为主,降水偏少（多）;华北地区气流以上升（下沉）为主,降水偏多（少）。
In order to study the relationship of the northern boundary of East Asia summer monsoon and summer precipitation anomalies in the eastern part of China,a new northern boundary indices of East Asia summer monsoon is defined,using the latitude of 2 m/s southerly north of 20°N,which is the mean meridional wind over 105°～125°E at 850 hPa.The results show that the northern boundary of East Asia summer monsoon lies far north than normal before 1976 and far south after 1976,and has an obvious inter-decadal variability,and is close related with summer precipitation anomalies in the East part of China.Corresponding to the anomaly of East Asia summer monsoon northern boundary,the east Asia summer monsoon intensity,subtropical high in the northwest Pacific and warm low pressure over the Asia continent have also the relevant changes,their correlations are as follows： When the northern boundary of East Asia summer monsoon reaches far north than normal,the Asian continent warm low pressure in tropospheric lower layer,stronger;the East Asia summer monsoon,stronger;the ridge and northern boundary of tropical high in the northwest Pacific,far north;its area,bigger;the South Asia high,weaker,the dominant air flow is sinking and rainfall is less in the mid-and lower valley of the Yangtze River,while the dominant air flow is rising and rainfall is richer in North China,and vice versa.
出处
《高原气象》
CSCD
北大核心
2008年第2期325-330,共6页
Plateau Meteorology
基金
江苏省气象灾害重点实验室(南京信息工程大学)开放课题(KLME0508)
国家重点基础研究发展计划(2007CB411801)共同资助
关键词
东亚夏季风北界
大气环流
夏季降水
年代际变化
副热带高压
Northern boundary of East Asian summer monsoon
General atmosphere circulation
Summer preicipitation
Interdecadal variation
Subtropical high
