全球扰动的结构、演变及其球面Rossby波包表示

Evolution of the Structure of the Global Disturbance and Its Expression in Spherical Rossby Wave Envelope

利用按谱函数展开的方法,计算和分析了正压球面Rossby波的连续谱和离散谱的波包结构、演变和传播特征,发现无论是结构、演变还是传播,连续谱波包和离散谱波包都很不相同。连续谱波包的传播速度不仅大小而且方向都随纬度变化;离散谱波包的传播速度只有大小随纬度变化,其方向在任何纬度上都是向西的。连续谱的波包和离散谱的波包在初始时刻虽然都表现为子午圈上不规则的波动,但随着时间的增加,二者的变化规律不同,连续谱的波包具有局部特征,主要表现在两个半球的中高纬地区,且随时间振幅迅速衰减;而离散谱的波包具有全球性质。将二者与整个扰动波包进行比较,发现:在中高纬度地区,连续谱波包的结构与扰动波包的结构相似,而在赤道地区,离散谱的波包与扰动波包相似。

The wave envelopes of the continuous and discrete spectrum of the barotropic spherical Rossby wave are calculated using the method of spectrum function expanding. And the characteristics of their structure, evolvement and propagation are analyzed. The results show that the characteristics of the continuous spectrum are different from that of the discrete spectrum whether in structure, evolvement or propagation. In the propagation of the wave envelopes of the continuous spectrum, the speed and the direction vary with latitude. The propagation speed of the discrete spectrum envelopes vary with latitude, but its direction is westward at any latitude. Both envelopes present anomalous waves on the meridian circle in initial time. But the change rules with time are different. The continuous spectrum envelope appears local characteristic, and it presents middle and high latitude in the two hemispheres. Its amplituderapidly weakens with time. The discrete spectrum envelope presents global characteristic. When comparing them with the disturbance envelope, it can be found that the structure of the continuous spectrum envelope is similar to that of the disturbance envelope in middle and high latitude, while the structure of the discrete spectrum envelope is similar to that of the disturbance envelope in the equator region.