摘要
首先根据Oman关于北大西洋涛动(NAO)指数冬季平均值的年际变化挑选出强NAO年,然后利用NCEP/NCAR逐日再分析资料,分析了在强NAO年北半球冬季阻塞发生频率和生命期的统计特征,最后通过对强NAO年大气斜压性进行冬季气候平均,合成得到了三个区域(北大西洋、欧洲和北太平洋)对流层平均大气斜压性随纬度的分布情况。结果发现:北大西洋在NAO负位相时下游阻塞发生频率更高,持续时间更长;NAO正位相则有利于欧洲长生命阻塞的发生和维持;北太平洋阻塞在NAO负位相发生频率明显更高,在NAO正位相阻塞的平均持续时间更长。大气斜压性随纬度的分布与阻塞的发生有较好的对应关系,过强的大气斜压性会抑制阻塞的发生。
First strong NAO years are selected according to the annual variation of North Atlantic Oscillation （NAO） index by Oman. Then the statistical characteristics of wintertime blockings during strong NAO years in the Northern Hemisphere are investigated based on daily mean NCEP/NCAR reanalysis datum. After that, by calculating the climatological values of baroclinicity in wintertime in strong NAO years, the composite latitudinal variation of average baroclinicity of the troposphere in North Atlantic Ocean, European region and North Pacific Ocean is received. It is found that the blocking frequency is higher and lifetime of blocking is longer during the strong negative phase of the NAO in North Atlantic Ocean, the strong positive phase of the NAO is in favor of the occurrence and persistence of blockings in European region. It is also known that the blocking frequency is higher during the strong negative phase of the NAO and the lifetime of blocking is longer during the strong positive phase of the NAO in North Pacific Ocean. There are some interesting relationships between the average baroclinicity of the troposphere and the blockings in the Northern Hemisphere. The excess of baroclinicity is unfavorable for the development and persistence of blockings.
出处
《热带气象学报》
CSCD
北大核心
2009年第5期615-620,共6页
Journal of Tropical Meteorology
基金
国家自然科学基金资助项目(4057016)资助
关键词
阻塞环流
北大西洋涛动
大气斜压性
blocking
North Atlantic Oscillation（NAO）
baroclinicity
