Extratropical extended-range precursors near the tropopause preceding persistent strong precipitation in South China: a climatology
Extratropical extended-range precursors near the tropopause preceding persistent strong precipitation in South China: a climatology
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DOI：
10.1007/s00382-020-05437-6
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发表时间：
2020-09
期刊：
影响因子：
4.6
通讯作者：
Liang Zhao;Haiwen Liu;Yamin Hu;Huhua Cheng;Ziniu Xiao
中科院分区：
文献类型：
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作者：
Liang Zhao;Haiwen Liu;Yamin Hu;Huhua Cheng;Ziniu Xiao
夏初雨季（PSRS; 4 - 6月）是华南地区强降水最频繁的时期。持续性强降水事件（PSPEs）造成的生命和财产损失比短时间强降水更大。利用等熵位涡（IPV）的CISO分析方法，研究了PSRS期间两次持续正气候季节内振荡（PPCISOs）降水前对流层顶附近的扩展范围信号。结果发现，前驱信号可以更好地看到在IPV CISO比在未经过滤的IPV。第一场暴雨PPCISO是由高IPV CISO沿动力对流层顶沿着向东传播引起的，该动力对流层顶来自北极地区和青藏高原西部。第二个是最持久的（13天）。它的高IPV CISO起源于北极地区和热带季风地区，分别在降雨CISO峰值前20天或更长时间。青藏高原西部和东亚西风急流北方对流层顶附近区域是对流层外高IPV对流层顶对流层季风引起的南向高IPV CISO和北向正IPV CISO在降水高峰前10天左右开始相互作用。从那时起，相互作用导致一个狭窄的三角形正PV通道上倾斜的345 K等熵表面。一个特定的CISO模式，其特征在于由三个负IPV CISO（南亚，鄂霍次克和西太平洋副热带高压）隔离的细长的高IPV CISO，是第二次降雨PPCISO持续时间长的原因。
The pre-summer rainy season (PSRS; April–June) is the period of most frequent strong precipitation in South China (SC). Persistent strong precipitation events (PSPEs) can cause greater loss of life and property than short-lived strong precipitation. This paper investigates extended-range signals near the tropopause preceding two persistent positive climatological intraseasonal oscillations (PPCISOs) in precipitation corresponding to two climatological PSPEs in SC during the PSRS, using the CISO analysis of isentropic potential vorticity (IPV). It is found that precursor signals can be better seen in IPV CISOs than in unfiltered IPV. The first rainfall PPCISO is caused by an eastward propagation of high-IPV CISOs along the dynamical tropopause originating from the Arctic region and west of the Tibetan Plateau. The second is the most persistent (13 days). Its high-IPV CISOs originate over the Arctic region and the tropical monsoon region, respectively, 20 or more days prior to the rainfall CISO peak. The west of the Tibetan Plateau and the northern region of the East Asian westerly jet near the tropopause are two transit points where extratropical high-IPV CISOs strengthen and then change their propagation direction. The southward high-IPV CISOs and the northward positive IPV CISO caused by the monsoon begin to interact about 10 days prior to rainfall peak. Since then, the interaction leads a narrow meridional positive PV channel on the inclined 345 K isentropic surface. A specific CISO pattern, characterized by an elongated high-IPV CISO isolated by three negative IPV CISOs (the South Asian, the Okhotsk and the western Pacific subtropical highs), is responsible for the long duration of the second rainfall PPCISO.