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ISSN 1006-9895

CN 11-1768/O4

平流层NAM事件中阻塞高压发生及其调制地面温度异常型的统计特征
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1.天津市气象灾害防御技术中心;2.中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室;3.南京信息工程大学 气象灾害教育部重点实验室/气候与环境变化国际合作联合实验室/气象灾害预报预警与评估协同创新中心/大气科学学院

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42075052, 91837311,江苏省自然科学基金资助项目(项目编号:BK20211288)


Statistical characteristics of occurrence of blocking highs and their modulation on surface air temperature during anomalous stratospheric northern annular mode events
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1.State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics;2.Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD), Nanjing University of Information Science &3.Technology

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    摘要:

    本文利用1979–2020年ERA5逐日再分析数据,分析了在平流层北半球环状模(NAM)正负事件中,阻塞高压(简称阻高)发生及其调制地面温度异常型的统计特征。结果表明,北半球的四个阻高系统分别趋于在NAM事件的不同阶段发生,其中格陵兰阻高(GB)和北太平洋阻高(NPB)更趋于出现在正NAM事件的发展阶段和负NAM事件的衰减阶段,乌拉尔山阻高(UB)多出现在正NAM事件的衰减阶段和负NAM事件的发展阶段,而大西洋–欧洲阻高(AEB)则多发生在正、负NAM事件的衰减阶段。尽管NAM事件过程中有阻高发生的天数远少于无阻高发生的天数,但阻高的存在对平流层NAM影响下的地面温度异常空间型有显著的调制作用,特别是在正NAM事件中,GB的出现可导致欧亚大陆从整体偏暖或北暖–南冷型变为北冷–南暖型,同时导致北美大陆则从整体偏冷或北冷–南暖型变为北暖–南冷型;此外在负NAM事件衰减阶段出现的UB,不仅可导致欧亚大陆的北冷–南暖型反转为北暖–南冷型,亦可使北美大陆由北暖–南冷型转为南暖–北冷型。相比之下,AEB和NPB两阻高发生时地面温度异常型多由平流层NAM的影响所主导,即阻高的调制作用并不显著。在NAM影响以及各阻高的协同作用下,从正NAM事件峰值至负NAM事件发展阶段,整个中纬度地区欧亚大陆偏冷/北美偏暖;从负NAM事件衰减阶段至正NAM事件的初始阶段则相反;两大陆地区的温度异常多呈中–高纬南北反位相变化特征。本文进一步通过蒙特卡洛随机取样检验,证实了上述关于阻高调制地面温度异常型的结论。

    Abstract:

    Using 1979–2020 ERA5 daily reanalysis data, this paper analyzes the statistical characteristics of blocking and its modulation on surface air temperature anomalies (SATA) during stratospheric northern annular mode events (NAMs). The results show that the four blocking highs in the northern hemisphere tend to occur in different stages of NAMs. Greenland blocking (GB) and North Pacific blocking (NPB) occur more frequently in the development stage of positive NAMs and the decay stage of negative NAMs. Ural blocking (UB) tends to occur in the decay stage of positive NAMs and the development stage of negative NAMs. The Atlantic-Europe blocking (AEB) is more likely to occur in the decay stage of both positive and negative NAMs. Although the number of days with blocking high is far less than that without blocking high during NAMs, the blocking high has a significant modulation effect on the spatial pattern of SATA related to the NAMs. When GB occurs during positive NAMs, the SATA in Eurasia changed from “overall warm” or “North warm-South cold” to “North cold-South warm” in the extratropics, while the SATA in North American changed from the “overall cold” or “North cold-South warm” to “North warm-South cold”. The UB in the decay stage of negative NAMs can not only reverse the “North cold-South warm” SATA pattern to “North warm-South cold” pattern in Eurasia, but also lead to the SATA pattern in North American changing from “North warm-South cold” to “South warm-North cold”. However, the modulation effect of AEB and NPB on the spatial patterns of SATA in most stages of NAM is not significant, that is, the spatial patterns of SATA is mainly dominated by NAMs. Under the influence of NAMs and the modulation of blocking high, Eurasia is colder and North America is warmer in mid latitudes from the peak stage of positive NAMs to the developing stage of negative NAMs, while it is the opposite from the decay stage of negative NAMs to the initial stage of positive NAMs. The dominant patterns of SATA in Eurasia and North America tend to the South-North dipole pattern between mid- and high- latitudes during NAMs. These conclusions are verified by Monte Carlo random sampling test.

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  • 收稿日期:2022-03-23
  • 最后修改日期:2022-07-09
  • 录用日期:2022-11-04
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