阻塞过程中大气运动不同时间尺度分量的演变及其相互作用

VARIATIONS OF THE DIFFERENT TIME—SCALE COMPONENTS OF THE ATMOSPHERIC MOTION DURING THE PROCESS OF A BLOCKING

对阻塞过程中的大气运动进行5天高通和低通滤波分析,发现大气阻塞形势的建立、维持和崩溃主要是由时间尺度大于5天的慢变波决定的。在阻塞建立和维持阶段,时间尺度小于5天的高频波向东传播进入急流分支处时被东西向压缩、南北向拉长。通过计算不同时间尺度分量之间的能量输送,发现慢变波与高频波的相互作用是阻塞形势建立和崩溃的重要机制。另外,阻塞过程的时间尺度也受大气准两周振荡控制。

The high and low pass filter analyses of the atmatmospheric motion in the process of a blocking for five days show that the genesis,maintenance and collapse of the atmospheric blocking depend chiefly upon the slow variable waves whose time scale is more than five days. At the stage of the genesis and maintenance of the blocking, the high—frequency waves which last less than 5 days show east—west contraction and north—south extension when they propagate eastward into the jet stream branch. Calculations of the energy transfer between different time—scale components indicate that the interaction between the slow variable waves and the high—frequency waves is the important mechanism of the genesis and collapse of the blocking pattern. And the time scale of the blocking is governed by the quasi—two—week oscillation of the atmosphere.