拉萨夏季大气热源10～20d的振荡特征

The 10—20 d oscillation characteristics of summer atmospheric heat source in Lhasa

利用逐日大气热源资料分析1950—2006年拉萨夏季大气热源的气候及其异常特征。结果表明:1)拉萨夏季大气热源的气候平均值为88W·m-2,明显低于亚洲季风槽区夏季热源的气候平均值,是一般强度的大气热源区。20世纪90年代中期拉萨夏季大气热源趋于减弱,21世纪初其值接近于0。2)拉萨夏季57a大气热源10～20d振荡强度约为季节内振荡平均强度的2倍,显著年数(33a)占总年数的57.6%,因此10～20d振荡是拉萨夏季大气热源季节内振荡的重要分量。3)拉萨夏季大气热源10～20d振荡强度存在明显的季节内变化(7月上旬前后振荡最强)和明显的年代际差异(20世纪50年代末—60年代中、80—90年代前期是两个强振荡阶段)。

The climatic and anomalous characteristics of summer atmospheric heat source in Lhasa are investigated by using the daily atmospheric heat source data from 1950 to 2006. On this basis, the basic features of 10--20 d oscillation of summer atmospheric heat source in Lhasa are analyzed especially. The results are as follows ： 1 ） The climatic mean of summer atmospheric heat source in Lhasa is 88 W ～ m^-2 ,which is obviously lower than that in the Asia monsoon trough area. So Lhasa is an atmospheric heat source area with the general intensity. But the summer atmospheric heat source in Lhasa shows an obvious declining tendency in the mid-1990s, and it is close to 0 at the beginning of 21 century. 2）The intensity of 10--20 d oscillation is about two times as much as the mean intensity of the intraseasonal oscillations of summer atmospheric heat source in Lhasa from 1950 to 2006. The significant 33 years account for 57.6% of the total 57 years, so the 10--20 d oscillation is an important component for intraseasonal oscillations of the summer atmospheric heat source in Lhasa. 3 ） There is an obvious intraseasonal variation for 10--20 d oscillation of summer atmospheric heat source in Lhasa, which is the strongest during the 20 days before or after the beginning of July. There is also an obvious interdecadal variation, with two stronger stages from the end of 1950s to the middle of 1960s, and from 1980s to the early of 1990s.