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ISSN 1006-9895

CN 11-1768/O4

两类厄尔尼诺背景下MJO对太平洋阻塞频率的调节作用
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南京信息工程大学

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江苏省自然科学基金项目(BK20210660,BK20191404),热带海洋环境国家重点实验室(中国科学院南海海洋研究所)开放课题(LTO2116),国家自然科学基金项目(41975048,42075032)


The Impact of Madden-Julian Oscillation on Pacific Blocking Frequency during Two Types of El Ni?o
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Nanjing University of Information Science and Technology

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    摘要:

    本文基于1979–2019年ERA-interim逐日再分析数据和二维阻塞指数,探究了两类(中部型和东部型)厄尔尼诺背景下热带季节内振荡(MJO)对太平洋地区阻塞频率的调节作用。本研究选取出现频次较高且平均振幅较强的位相3和7进行研究。结果表明,在两类厄尔尼诺背景下MJO第3位相期间,MJO激发的遥相关位置相似,均对应极地地区(白令海地区)正(负)的位势高度异常,从而使高纬度太平洋地区均出现正的阻塞频率异常。在东部型厄尔尼诺背景下MJO第7位相(EP7)期间中高纬太平洋地区存在正的阻塞频率异常。但是在中部型厄尔尼诺背景下MJO第7位相(CP7)期间没有大范围显著的异常阻塞频率。这是因为EP7期间副热带西风急流偏北,使得MJO的遥相关可以传至50°N以北,引起中高纬度地区有利于阻塞频率增加的位势高度异常。然而CP7期间西风急流偏南,使得对应的遥相关仅能传至40°–50°N之间,对高纬度地区的位势高度影响较小,导致该时期内没有大范围显著的阻塞频率异常。最后本文使用ECHAM4.6气候模式验证了上述结论。

    Abstract:

    Based on ERA-interim reanalysis daily data during 1979–2019, the impact of Madden-Julian Oscillation (MJO) on Pacific blocking frequency during two types of El Ni?o (Eastern and Central El Ni?o) is examined using a two-dimensional blocking index. Phase 3 and 7 with the higher frequency and the stronger amplitude are selected in this study. It is found that the locations of MJO teleconnections are similar in MJO phase 3 during the Eastern and Central El Ni?o years (EP3 and CP3), corresponding to a positive (negative) geopotential height anomaly in the polar region (the Bering Sea). Thus there are positive blocking frequency anomalies in the high-latitude Pacific sector during the EP3 and CP3. The blocking frequency anomalies over the mid-high-latitudinal Pacific are significantly positive in MJO Phase 7 during the Eastern El Ni?o years (EP7), but are not largely significant in MJO Phase 7 during the Central El Ni?o years (CP7). Because the subtropical westerly jet shifted to the north in the EP7, the MJO teleconnection locates in the north of 50°N. This teleconnection corresponds to the geopotential height anomalies, which increase the Pacific blocking frequency, in the Pacific sector. However, the subtropical westerly jet shifted to the south in the CP7. The teleconnection locates between 40°N and 50°N, resulting in weak influence to geopotential height in the Pacific region. So there are not largely significant blocking frequency anomalies over the Pacific region in the CP7. Finally, the ECHAM4.6 model is used to verify the above conclusions.

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  • 收稿日期:2021-06-24
  • 最后修改日期:2021-12-06
  • 录用日期:2022-02-28
  • 在线发布日期: 2022-02-28
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