Abstract In this study, comparison of blocking climatological behaviors is presented for the two periods of 1959–1988 and 1989–2018 in a part of the Northern Hemisphere including the Atlantic Ocean, Europe and West Asia regions. Blocking events were detected using a modified blocking index that is based on vertically integrated potential vorticity. By applying this index, the characteristics of detected blocking events such as frequency, duration, intensity and area were determined and compared for both the periods. According to the results, on average, 16 and 15 blocking events per year were identified in the first and second periods, respectively. The trend analysis shows that the number of blocking events in the period 1959–1988 was significantly decreased, while it was slightly increased in the period 1989–2018. Blocking activity was most prevalent from the eastern Atlantic through Europe to West Asia, but this longitude band exhibits a relatively eastward shift in the second period. In addition, the seasonal distributions are similar to those found in previous studies with the higher occurrence of blocking events during winter and autumn seasons and the lowest frequency in summer, as well as long-lasting events and greater intensity and extension in winter than the summer time, especially in the second period. These seasonal variations of blocking frequency may be due to synoptic scale eddies and planetary waves which are more active and stronger in the colder seasons than the other seasons. On the other hand, a comparison between the two periods shows that the blocking events tend to be more frequent over West Asia especially during summer in recent years. Although discrepancies between the two periods are not significant, they could be partly due to the impacts of climate change in recent decades.

中文翻译：

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1959-2018年欧洲-大西洋和西亚阻塞气候行为研究

摘要 本研究比较了1959-1988年和1989-2018年两个时期北半球部分地区包括大西洋、欧洲和西亚地区的阻塞气候行为。阻塞事件是使用基于垂直积分位涡的修正阻塞指数检测到的。通过应用该指数，确定并比较两个时期的检测到的阻塞事件的特征，例如频率、持续时间、强度和面积。根据结果​​，在第一和第二阶段，平均每年分别识别出 16 和 15 次阻塞事件。趋势分析表明，1959-1988年期间阻塞事件数量显着减少，而1989-2018年期间略有增加。从东大西洋到欧洲再到西亚，阻塞活动最为普遍，但该经度带在第二个时期表现出相对向东的移动。此外，季节分布与以往研究相似，冬季和秋季阻塞事件发生率较高，夏季发生频率最低，且事件持续时间长，冬季强度和延伸范围大于夏季。时间，尤其是在第二阶段。阻塞频率的这些季节性变化可能是由于天气尺度涡和行星波在较冷的季节比其他季节更活跃和更强。另一方面，两个时期的比较表明，近年来西亚地区特别是夏季的阻塞事件往往更加频繁。虽然这两个时期之间的差异并不显着，但部分原因可能是近几十年来气候变化的影响。