Biweekly and 21–30-Day Variations of the Subtropical Summer Monsoon Rainfall over the Lower Reach of the Yangtze River Basin
Biweekly and 21–30-Day Variations of the Subtropical Summer Monsoon Rainfall over the Lower Reach of the Yangtze River Basin
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DOI：
10.1175/2009jcli3005.1
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发表时间：
2010-03
影响因子：
4.9
通讯作者：
Jing Yang;Bin Wang;Q. Bao
中科院分区：
文献类型：
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作者：
Jing Yang;Bin Wang;Q. Bao
摘要长江下游位于梅雨、白锋的中心地带，是亚热带东亚夏季风的代表。基于新发布的日降水资料，在北寒带夏季（5 - 8月）确定了两种主要的季节内变化（ISV）模式，光谱峰值出现在第15天（双周模式）和第24天（21 - 30天模式）。这两种模式具有可比较的强度，它们共同占季节内总方差的57%以上。两种ISV模态在LYRB的极端阶段都表现出斜压结构。然而，与这两种模式相关的起源和演化是不同的。考虑到它们在LYRB上空极端湿相的成因，双周模态是由一个向东南移动的中纬度急流涡度异常引发的，而21 - 30天模态主要与来自……的反气旋异常的低空向西传播有关。
Abstract The lower reach of the Yangtze River basin (LYRB) is located at the central region of the mei-yu and baiu front, which represents the subtropical East Asian (EA) summer monsoon. Based on the newly released daily rainfall data, two dominant intraseasonal variation (ISV) modes are identified over the LYRB during boreal summer (May–August), with spectral peaks occurring on day 15 (the biweekly mode) and day 24 (the 21–30-day mode). These two modes have comparable intensities, and together they account for above about 57% of the total intraseasonal variance. Both ISV modes exhibit baroclinic structures over the LYRB at their extreme phases. However, the genesis and evolutions associated with the two modes are different. Considering the genesis of their extreme wet phases over the LYRB, the biweekly mode is initiated by a midlatitude jet stream vorticity anomaly moving southeastward, while the 21–30-day mode is primarily associated with a low-level westward propagation of an anticyclonic anomaly from ...