夏季西太平洋副高脊线的活动特征及其可能的机制

Ridge Movement and Potential Mechanism of Western Pacific Subtropical High in Summer

通过对多年平均的逐日资料的分析表明 ,夏季不同区域副热带高压脊轴的垂直结构和活动特征存在明显不同 ,这与空间非均匀加热的分布密切相关。西太平洋地区副高脊轴随高度向北倾斜 ,而 1 60°E～ 1 80°地区向南倾斜 ;北太平洋中、西部副高在北进期的脊线活动均存在显著的 1 0～ 2 0 d周期低频振荡 ,东亚季风区还具有明显的准 40 d振荡周期。分析表明 :副高的季节性南北移动主要受太阳辐射的影响 ,而空间非均匀加热起着调节副高移动速率以及改变副高强度的作用 。

The analysis of 40-year mean daily data shows that marked differences lie in vertical structure and movement of subtropical high ridge (STH) between 120～150°E and 160°E～180°, which are closly related to nonuniform heating.The ridge line slopes northward with hight while southward in 160°E～180°.The ridge movement has 10～20-day low-frequency oscillation during its northward over central and western Pacific,particularly in East-Asian monsoon area with quasi-40-day oscillation period.The analysis shows that solar radiation is the main factor of STH movement and that nonuniform heating plays a very important role in its moving speed and change of strength,especially for its abnormality.