南、北半球环状模月内活动的主要时间尺度

Main Submonthly Timescals of Northern and Southern Hemispheres Annual Modes

基于"大气环状活动带"的概念,利用逐日再分析资料对南、北半球环状模(简称SAM、NAM)的季节活动特征及月内活动的主要时间尺度(Submonthly timescales)进行了研究,结果表明,NAM具有冬季强、夏季弱的年循环特征,而SAM则表现出明显的准半年循环特征。并且,逐年的功率谱分析进一步显示:NAM的月内活动的主要时间尺度以准1周和准2周为主,且它们具有共生性,准3周为相对次要的周期;而SAM的月内活动周期与NAM相似,准2周和准1周较强,准3周次之。NAM和SAM的月内活动在不同特征时间尺度上的空间特征及其时间演变值得进一步研究。

Based on the conception of ＂Annular Belts of Action （ABAs）＂ ,characteristics of the seasonal variation and main submonthly timescales of Northern and Southern hemispheres annular modes （SAM and NAM） are studied in this paper using NCEP/NCAR reanalysis daily data. The results show that NAM is strong in winter and weak in summer while SAM＇s intensity has semi-annual cycle. Furthermore,power spectrum analysis is applied year by year to detect the main submonthly timescals of anular modes,the result shows that NAM has quasi-week period and quasi-two-week period variability,which are inclined to accompany each other,the quasi-three-week period is the following time scale, and SAM exhibits similarity of the main submonthly timescales to NAM,that is,the quasi-two-week period and the quasi-week period are the main periods and the quasi-three-week period is the second period. Both the spatial characteristics of NAM and SAM with different submonthly timescales and their temporal evolvement are worth further researching.