The north edge of the East Asian summer monsoon (EASM) is defined by using the isoline with average total column water vapor (TCWV) equal to 25 mm, and the relationship between the north edge of the EASM and summer extreme precipitation in North China (NC) from 1961 to 2020 is discussed. Self-Organizing Maps (SOM) method is used to cluster extreme precipitation in the abnormal years of the north edge in NC, and the circulation characteristics of different types of extreme precipitation are discussed. The results show that the north edge of the EASM is closely related to extreme precipitation in NC. When the north edge is northerly, both the frequency and total amount of extreme precipitation increase significantly in the monsoon marginal zone. Based on different monsoon circulation background, summer extreme precipitation events in NC are divided into four categories, namely, the central type and southern type in the northerly years of north edge, and the central type and eastern type in the southerly years of north edge. The occurrence of different types of extreme precipitation is closely related to the different characteristics of local trough, the western Pacific subtropical high (WPSH), and wave trains in the middle and high latitudes. Specifically, the central type extreme precipitation is affected by the mid-latitude wave train in the northerly years of north edge. As for the central type extreme precipitation in the southerly years of north edge, both high-latitude and mid-latitude wave trains transfer from west to east and converge over NC. However, the wave disturbance energy is relatively weak, leading to the extreme precipitation with weak intensity.

中文翻译：

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东亚夏季风北缘年际变率与华北极端降水的关系


使用平均总柱状水汽 （TCWV） 等于 25 mm 的等值线定义东亚夏季风 （EASM） 北缘，并讨论了 EASM 北缘与 1961 年至 2020 年华北夏季极端降水 （NC） 的关系。采用自组织图（SOM）方法对北缘北缘异常年份的极端降水进行聚类，讨论了不同类型极端降水的环流特征。结果表明：EASM北缘与北卡罗来纳州的极端降水密切相关。当北缘偏北时，季风边缘区极端降水的频率和总量均显著增加。根据不同的季风环流背景，将北卡罗来纳州夏季极端降水事件分为4类，即北缘北缘北年中部型和南端型，北缘南年中部型和东端型。不同类型极端降水的发生与局地槽、西太平洋副热带高压 （WPSH） 和中高纬度地区波列的不同特征密切相关。具体而言，中部型极端降水受北缘北纬年份中纬度波列的影响。对于北缘南风年中部型极端降水，高纬度和中纬度波列均由西向东转移，并在北卡罗来纳上交汇。然而，波浪扰动能量相对较弱，导致极端降水强度较弱。