近40年5—6月东北亚和北半球其他区域阻塞高压活动特征及其联系

基于美国环境预报中心/国家大气研究中心（NCEP/NCAR-Ⅰ）再分析资料，按照国际通行的阻塞高压（阻高）定义，采用计算机自动识别和天气图人工主、客观相结合的检测方法，获得了1979—2018年5月和6月逐日北半球中高纬度阻高活动的无缝隙分布；并利用线性相关和信息流因果关系等统计方法，研究了东北亚（鄂霍次克海）阻高与北半球其他阻高活动区特征及其联系。根据阻高活动集中程度与占北半球活动总天数的百分比，选定8个5月阻高主要活动区和10个6月阻高主要活动区。从统计结果来看，5月北太平洋、北美和乌拉尔山阻高活动占前3位，6月东北亚阻高活动天数跃升第1位。值得注意的是，初夏在贝加尔湖以南、青藏高原以北地区出现了明显的阻塞形势，称为青藏高原北阻高。5月和6月北半球各阻高活动中心集中的纬度分布，自西向东具有“正弦波”特征，其主要活动区引起的同期北半球500 hPa高度场的异常虽不尽相同，但均具有一定的遥相关特征；5月和6月东北亚阻高活动天数的年际变化分量具有明显的相对独立性。5月东北亚阻高是6月贝加尔湖阻高活动年际变化的稳定影响源，是6月青藏高原北阻高活动年际变化的不稳定影响源；唯有5月北太平洋阻高是6月东北亚阻高年际变化的稳定影响源。2019年6月北半球阻高活动异常的区域位于欧洲，达19 d，为气候平均值（7 d）的2.7倍，也是导致欧洲大陆初夏高温的主要影响系统。 

Characteristics of blocking high in Northeast Asia and other areas of the northern Hemisphere and their relationships during May to June in recent 40 years

Based on NCEP/NCAR-Ⅰ reanalysis and the internationally accepted definition of blocking high, the northern Hemisphere blocking high distribution maps were obtained from May to June over the 40-year period of 1979—2018 using subjective and objective detection methods. Linear correlation and information flow statistical methods are used to study interannual and interdecadal relationships between anomalous variations of blocking highs over Northeast Asia and other areas in the northern Hemisphere. According to the concentration of blocking high activities and their percentages of total days in the northern Hemisphere, 8 major areas in May and 10 major areas in June are selected. In May, the North Pacific blocking, the North America blocking, and the Ural blocking are the top three. In June, the number of days for the Northeast Asia blocking jumps to the top. It is worth noting that in the early summer, there is a significant increase in blocking to the south of the Baikal Lake and north of the Tibetan Plateau, which is called the North Tibetan Plateau blocking high. The latitude distribution of the northern Hemisphere blocking high activity centers in May and June shows a "sine wave" characteristic. Although the 500 hPa height field anomalies caused by blockings in their main active areas in the northern Hemisphere show different characteristics in May and June, they demonstrate teleconnection characteristics. The interannual variation of the Northeast Asia blocking high in May and June shows an obvious independence. The Northeast Asia blocking high in May is a source of the interannual variation of Lake Baikal blocking high in June; it is also an unstable source of the interannual variation of the North Tibetan Plateau blocking high in June. The North Pacific blocking in May is the only stable source of the interannual variation of the Northeast Asia blocking in June. In June 2019, the area of most frequent and abnormal blocking high activities in the northern Hemisphere remains in Europe for 19 d, which is 2.7 times the climatological average of 7 d. The blockings are also the main influence system leading to the early summer high temperature in Europe.