热带和中高纬地区季节内振荡的特征及其动力学诊断

DIAGNOSTIC STUDY FOR INTRASEASONAL OSCILLATION OF TROPICAL AND MID-HIGH LATITUDES IN A LOW RESOLUTION GLOBAL SPECTRAL MODEL

使用5年低阶全球谱模式资料,对中高纬大气和热带大气季节内振荡的动力学性质和传播特征进行了诊断研究。分析发现模式再现了大气中季节内振荡在热带和中高纬地区的传播特性以及它们之间的差异。热带大气30—60天振荡在速度势场上表现为纬向—波结构和行波特性,而在散度风场上反映了赤道西太平洋—印度洋东西向偶极子型的振荡。中高纬大气30—60天振荡表现为定常波位相和振幅的变化,即波包络的传播特征。它与中高纬地区遥相关型的转换有关,通过遥相关位相和振幅的变化,不仅完成了热带和中高纬地区之间以及热带不同区域之间的能量输送,而且通过这种能量输送过程把南、北半球中高纬地区季节内振荡联系起来。

In this paper, five-year simulated data from a low-resolution global spectral model are analyzed in order to study dynamical features and propagation characteristics of intraseasonal oscillations over the mid-high latitudes and the tropical atmosphere. The simulation shows that there is the 30-50 day periodic oscillation in the low-resolution spectral model and it is found that propagation characters of intraseasonal oscillations over the mid-high latitudes and the tropics are different. In the velocity potential field, the 30-50 day oscillations in the tropical atmosphere act as migrating latitudinal waves with wavenumber at 1, while following the pattern of east-west dipole from equatorial western Pacific to the Indian Ocean in the divergent wind field. On the other hand, the 30-50 day oscillations in mid-high latitudes appear as the variations in phase and amplitude of the standing planetary waves, which are related with the transformation of teleconnecting pattern for the area. The energy is transferred not only between the tropics and the mid- high latitudes, but also between different regions over the tropics. Through the energy transfer, the relationship has been built between the 30-50 day periodic oscillation over the mid-high latitudes and over the tropics.