北半球500hPa高度场定常波不平稳性分析  

An analysis of the anomaly of stationary waves in the Northern Hemisphere 500 hPa height field.

作　　者：周国华[1] 王盘兴[1] 施宁[1] 李巧萍[2] 佘高杰[1] 

机构地区：[1]南京信息工程大学大气科学学院,南京210044 [2]中国气象局国家气候中心,北京100081

出　　处：《气象学报》2009年第2期298-306,共9页Acta Meteorologica Sinica

基　　金：国家自然科学基金资助项目“青藏高原热源结构和振荡特征及其传播和影响机制”(40633018)

摘　　要：提出并阐明Lorenz环流分解意义下的定常波不平稳性概念,它是月平均图上纬向波动分量气候变率与定常波强度相对大小的表征。根据Lorenz环流分解,定义全域(局域)定常波不平稳度Ius(Iu1s),分析了北半球500hPa位势高度场定常波强度较大的30°—60°N纬带的定常波不平稳性,结果表明:(1)全域定常波不平稳带位置存在季节性北进、南退过程。平稳的定常波出现在冬季的35°—55°N的中纬度带和夏季的副热带地区(35°N以南),分别与冬季的东亚大槽、北美槽和较弱的欧洲槽,以及夏季的副热带高压等系统相联系。不平稳度的高值中心出现在春季的35°N和夏季的50°N,这与定常波强度季节变化和月平均图上槽脊位置、强度年际异常有关。(2)局域定常波不平稳度存在着明显的纬向不对称性。平稳带通常位于定常波的强槽强脊所控制的区域,而不平稳带通常位于定常波强度较弱的区域。副热带(35°N及以南)局域定常波不平稳度冬强于夏,中纬度(35°N及以北)则夏强于冬。夏季局域定常波不平稳度地理分布具有复杂的结构。但无论冬夏,北欧是定常波最不平稳的地区,北美大陆附近的定常波则相对平稳。(3)夏季,从华北经东北至北太平洋存在一个定常波不平稳度高值带,其高值中心位于中国黑龙江省东部(45°N,130°E),主要影响中国北方(东北、华北、西北),可能是该区夏季气候脆弱带的环流成因。A definition of stationary wave anomalies is given based on the Lorenz decomposition of the atmospheric circulation, and monthly variations of the zonal component of stationary waves relative to the mean are illustrated. A deviation index Ius（Ius^1） for global （local） stationary waves is used to analyze the stationary wave anomalies in the latitude band 30° -60°N, where the stationary waves in the Northern Hemisphere 500-hPa geopotential height field is significantly strong. The following results are obtained： （1） the devoation index characterizes the spatial-temporal variance of global stationary waves in the 30°- 60°N belt, and this anomalous belt advances southward and then retreats northward in the course of seasonal march. Steady stationary waves occur in mid-latitudes （35°- 55°N） in winter and in the subtropical zone （south of 35°N） in summer. Specifically, they are associated respectively with the major troughs of East Asia and North America and the weaker European trough in winter, and the relatively steady subtropical high system in summer. A high value center of the deviation index appears at 35°N in spring and 50°N in summer, which reflects the seasonal variation of the strength of stationary waves and that of their zonal distributions. （2） The degree of deviation for local stationary waves clearly shows a zonal asymmetry. The steady zones of stationary waves are always located in the areas controlled by strong troughs or ridges, whereas the anomalous ones are in the areas where the stationary wave intensity is weak. The degree of deviation for local stationary waves in the subtropics （south of 35°N） is larger in winter than in summer, and the reverse is true in the mid-latitude region （north of 35°N）. The summertime distribution of the deviation index on the whole shows a rather complicated structure. However, North Europe is the most anomalous area for local stationary waves, as represented by a high value of Ius^1 in both summer and winter, while over

关 键 词：500hPa位势高度场 定常波不平稳性 定常波不平稳度 气候脆弱带 环流成因 

分 类 号：P457.6[天文地球—大气科学及气象学] U468.21[机械工程—车辆工程]