【摘要】 利用NCEP/NCAR再分析资料和大气环流模式(CCSR/NIES AGCM Ver.5.6),对北半球冬季准定常行星波活动的年际变化进行了分析和模拟。基于以前对EP通量散度的遥相关分析,作者将EP通量散度的EOF第一分量时间序列T1定义为年际变化指数。对应于T1的高指数,在对流层和平流层低层,准定常行星波更多地折向赤道传播,从而在对流层出现一个EP通量散度的偶极子型异常,这一形势主要来自2波和3波的贡献;而折向高纬度经极地波导向上传播的行星波活动减弱了,在高纬度产生异常辐散,这一形势主要来自1波和2波的贡献。相关和回归分析发现,准定常行星波的年际变化与北极涛动有密切联系,与T1对应的纬向平均流场以及位势高度场的异常分布都与北极涛动下的异常形势非常相似。利用大气环流模式模拟的结果显示,模式在对流层可以很好地模拟准定常行星波的年际变化以及北极涛动形势,并且二者同样密切相关。但是模式还不能很好地模拟行星波经极地波导向平流层传播的年际变化,对可能的成因也进行了探讨。更多还原

【Abstract】 Recent study indicates that the stratospheric and tropospheric circulations are not isolated, and are dynamically linked in fact. There is evidence that the troposphere-stratosphere coupling interaction is closely associated with the quasi-stationary planetary wave activity. However, the study of the variation of quasi-stationary planetary wave activity is absent now. The interannual variation of quasi-stationary planetary wave in the Northern Hemisphere winter is analyzed by using NCEP/NCAR reanalysis data and simulated with the CCSR/NIES AGCM Ver.5.6. Based on the former study, time series of the first EOF component of EP flux divergence (T1) is defined as the interannual variation index. Data reanalysis result shows that the planetary wave propagates more equatorward in the troposphere and lower stratosphere with the positive T1, thus, there is a dipole of anomalous EP flux divergence in the midlatitudes of the troposphere. While the upward and poleward wave refraction into the polar waveguide is reduced with the positive T1, and there is anomalous divergence in high latitudes. It suggests interaction between meridional propagation and upward propagation through the polar wave guide of quasi-stationary planetary wave. Detailed analysis shows that the dipole pattern of EP flux divergence anomalies in mid-latitude troposphere comes basically from wavenumber 3, and wavenumber 2 mainly contributes to positive anomalies of the dipole pattern. Compared with wavenumber 2 and wavenumber 3, wavenumber 1 almost does not impact the pattern in the troposphere. However, the anomalous EP flux divergence through polar wave guide in high latitudes is mainly attributed to wavenumber 1 and wavenumber 2. Especially in stratosphere, wavenumber 1 and wavenumber 2 have similar contribution to the anomalous EP flux divergence, and display positive correlation with T1. However, the anomalous propagation of wavenumber 1 and wavenumber 2 displays different correlation with T1. With the positive T1, wavenumber 1 propagates more poleward and its upward propagation is obviously reduced, while wavenumber 2 more propagates to middle and low latitudes. The regression and correlation analysis shows that the anomalies of zonal mean zonal wind display an equivalent barotropic dipole pattern, which extends from the troposphere to the stratosphere, and the zonal mean temperature anomalies pattern also displays similar structure. The regression of geopotential height on T1 displays the south-north oscillation between the arctic region and middle latitudes. All these anomalies patterns with T1 resemble to the Arctic Oscillation (AO) anomalies, especially the correlation coefficient of T1 and winter AO index is 0.87, which is by far exceeding the 99% significance level. The results suggest that the interannual variation of quasi-stationary planetary wave is closely associated with the Arctic Oscillation. Simulation by AGCM shows that the interannual variation of quasi-stationary planetary wave, the corresponding patterns of zonal mean zonal wind, zonal mean temperature and geopotential heights, and the Arctic Oscillation in the Northern winter are all well simulated by the AGCM in the troposphere. Simulation result also shows that there is close correlation between the interannual variation of quasi-stationary planetary wave and the Arctic Oscillation in the troposphere. But in the stratosphere the simulation is not successful, and there is an obvious discrepancy between the reanalysis and the model.更多还原