我国北方500hPa春、夏季平均长波年际异常的EOF分析

EOF Analysis on Interannual Variation of 500hPa Long Wave in Northern China in Spring and Summer

利用1958—2008年全球逐日2.5°×2.5°NCEP/NCAR再分析资料,采用经验正交函数分解(EOF)和谐波分析方法对我国北方地区春、夏季平均长波进行了分析。结果表明:(1)我国北方春季平均长波主要表现为亚洲北部从咸海到日本存在一个完整的长波:巴尔喀什湖到我国罗布泊地区以长波脊活动为主,我国东北地区以长波槽活动为主,长波槽、脊的强度均呈增强趋势;夏季平均长波主要表现为乌拉尔山、贝加尔湖及鄂霍次克海地区的长波脊、槽、脊分布,蒙古国到我国北部地区多为长波槽活动,近51年来长波槽存在减弱趋势。(2)春季平均长波的距平变化主要表现为我国西北、华北地区与其上游和下游邻近地区存在反相关关系;夏季平均长波距平变化和春季相比有所东移,即我国北方大部分地区距平变化与其上游和下游地区存在反相关关系。

The spatial distribution and time evolution of long wave in Northern China in spring and summer were calculated by Empirical Orthogonal Function（EOF） and harmonic wave analyses to daily data from the National Center for Environmental Prediction/National Center for Atmospheric Research（NCEP/NCAR） Reanalysis for 1958-2008.The results showed that：（1） In spring,a complete wave lies from Aral Sea to Japan,that is to say,there is a ridge acting mostly from Lake Balkhash to Lop Nur and a trough in Northeast China,both of ridge and trough enhanced.In summer,there is a ridge in Ural Mountain and the Okhotsk Sea,and a trough in Lake Baikal,the trough acting mostly from Mongolia to North China,however,the trough weakened in the past 51 years.（2） The long wave departure has an anti-correlation relationship between Northwest China and North China and their upper and lower regions in spring,and in summer,the center of long wave departure moves toward east comparing with the spring.