Enhanced rainfall in North China in July 2021: Role of the North Pacific SST gradient

IF 2.3 4区 地球科学 Q3 METEOROLOGY & ATMOSPHERIC SCIENCES Atmospheric and Oceanic Science Letters Pub Date : 2024-03-01 DOI:10.1016/j.aosl.2023.100444
Zhaoyang Du , Lian-Tong Zhou , Kui Liu , Xiaoxue Yin
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Abstract

The rainfall over North China (NC) in July 2021 was the most since 1980, and coincided with a meridional gradient of sea surface temperature anomaly (MGSSTA) in the Pacific. The present study shows that the gradient between the positive sea surface temperature anomaly (SSTA) over the northwestern Pacific and the negative SSTA over the tropical central Pacific was the main reason for the enhanced rainfall in NC in July 2021 because of its influence on the anomalous northward movements of the western North Pacific anticyclone (WNPAC) and its southern cyclone. The associated easterly wind anomalies along the southern flank of the WNPAC converged with the anomalous easterly along the north flank of the anomalous cyclone, transporting more moisture from south to NC. Meanwhile, the MGSSTA likely induced an anomalous reversed Hadley circulation accompanied by distinct southerly wind anomalies in the low troposphere. These anomalies favored a strong monsoon circulation, which is often accompanied by a rain band in a more northern location.

摘要

2021年7月, 华北地区的降水量突破1980年以来的极值, 这与太平洋海温异常的经向梯度相吻合. 研究表明, 西北太平洋正海温异常与热带中太平洋负海温异常之间的梯度是2021年7月华北地区降水异常偏多的主要原因, 该梯度使得西北太平洋反气旋及其南部的气旋北移, 汇合的偏东风将大量水汽从海洋输送到华北地区, 使得华北地区降水偏多. 同时, 太平洋海温异常的经向梯度可能在对流层低层触发异常的反向哈德利环流, 伴随着南风异常, 使得季风环流增强, 雨带偏北.

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2021 年 7 月华北降雨增强:北太平洋 SST 梯度的作用
2021年7月华北降雨量为1980年以来最多,与太平洋海面温度异常经向梯度(MGSSTA)相吻合。本研究表明,西北太平洋海面温度异常的正梯度和热带中太平洋海面温度异常的负梯度是 2021 年 7 月华北降雨量增加的主要原因,因为它影响了北太平洋西部反气旋及其南部气旋的异常北移。沿西北太平洋反气旋南侧的相关偏东风异常与沿异常气旋北侧的异常偏东风汇合,将更多水汽从南部输送到北卡罗来纳州。同时,MGSSTA 可能诱发了异常的反向哈德利环流,并在对流层低层伴有明显的偏南风异常。摘要 2021 年 7 月,华北地区的降水量突破 1980 年以来的极值,这与太平洋海温异常的经向梯度相吻合。研究表明, 西北太平洋正海温异常与热带中太平洋负海温异常之间的梯度是 2021 年 7 月华北地区降水异常偏多的主要原因, 该梯度使得西北太平洋反气旋及其南部的气旋北移, 汇合的偏东风将大量水汽从海洋输送到华北地区, 使得华北地区降水偏多。同时, 太平洋海温异常的经向梯度可能在对流层低层触发异常的反向哈德利环流, 伴随着南风异常, 使得季风环流增强, 雨带偏北.
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来源期刊
Atmospheric and Oceanic Science Letters
Atmospheric and Oceanic Science Letters METEOROLOGY & ATMOSPHERIC SCIENCES-
CiteScore
4.20
自引率
8.70%
发文量
925
审稿时长
12 weeks
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