Recent Decadal Weakening of the Summertime Rainfall Interannual Variability Over Yellow-Huaihe River Valley Attributable to the Western Pacific Cooling
Recent Decadal Weakening of the Summertime Rainfall Interannual Variability Over Yellow-Huaihe River Valley Attributable to the Western Pacific Cooling
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DOI：
10.3389/feart.2022.946252
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发表时间：
2022-07
期刊：
影响因子：
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通讯作者：
Wei Lu;Yimin Zhu;Y. Ha;Zhong Zhong-Zhong;Yijia Hu
中科院分区：
文献类型：
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作者：
Wei Lu;Yimin Zhu;Y. Ha;Zhong Zhong-Zhong;Yijia Hu
研究了黄淮流域夏季降水年际变化的年代际转换特征。结果表明，2000年代后期以后，长江流域夏季降水的年际变率明显减弱。在2000年代后期之前的十年（以下简称P1），方差为1.28 m m d − 1，年际变率的平均值为1.49 m m d − 1。在2000年代后期之后的十年（P2），方差为0.35 m m d − 1，年际变率的平均值为0.62 m m d − 1。自2000年代后期以来，夏季降水年际变率的方差和平均值分别显著减少了72.7%和58.4%。上述年代际转换的原因进行了探讨。结果表明，东亚急流轴的年代际偏移和西太平洋副热带高压是导致夏季降水年际变化年代际转换的两个主要因素。北移的急流轴，这类似于太平洋-日本（PJ）模式，抑制了夏季降水的发展在YHRV。P1的西太平洋副高年际振荡比P2的显著，这与P2夏季降水年际变率减弱是一致的。进一步的分析表明，赤道中东太平洋的厄尔尼诺衰减阶段和P1期间海洋大陆和西太平洋的变暖是造成上述变化的调制因子。而在P2，主要的调制因子是赤道中东太平洋处于发展阶段的拉尼娜。在P1正年夏季降水增长的机制上，WP暖池和处于衰减阶段的厄尔尼诺加强了热带太平洋的步行者环流，并诱发Hadley环流，其在YHRV上空的上升分支为降水的发展提供了有利条件。与此同时，Rossby波的北向传播也抑制了西北太平洋的对流活动，从而间接加强了西太平洋副高。触发了PJ型，为降水的发展提供了有利的大尺度环流条件。
This study focuses on the interdecadal transition of summer rainfall interannual variability over the Yellow-Huaihe River valley (YHRV). It is found that the interannual variability of summer rainfall over the YHRV becomes significantly weakened after the late 2000s. In the decade before the late 2000s (hereafter P1), the variance is 1.28 m m d − 1 and the mean value of interannual variability is 1.49 m m d − 1 . In the decade after the late 2000s (P2), the variance is 0.35 m m d − 1 and the mean value of interannual variability is 0.62 m m d − 1 . The variance and mean value of summer rainfall interannual variability have considerably decreased by 72.7% and 58.4% since the late 2000s, respectively. The reasons for the aforementioned interdecadal transition are explored. The results show that the interdecadal shift of the East Asian jet stream axis and the western Pacific subtropical high (WPSH) are two major factors leading to the interdecadal transition of summer rainfall interannual variability over the YHRV. The northward shift of the jet stream axis, which resembles the Pacific-Japan (PJ) pattern, suppresses the development of summer rainfall over the YHRV. The interannual oscillation of WPSH in P1 is more significant than that in P2, which is consistent with the weakened interannual variability of summer rainfall in P2. Further analysis reveals that the modulation factors responsible for the above changes are El Niño in its decaying phase in the equatorial central eastern Pacific and the warming in the Maritime continent and the western Pacific (WP) in P1. While in P2, the primary modulation factor is La Niña in its developing phase in the equatorial central eastern Pacific. As for the mechanism of the growth of summer rainfall in P1 positive years, the WP warm pool and El Niño in its decaying phase strengthen the Walker circulation in the tropical Pacific and induce Hadley circulation, whose ascending branch over the YHRV provides a favorable condition for the development of rainfall. At the same time, the northward propagation of Rossby waves in response to the above SSTA pattern suppresses convective activities over the Northwestern Pacific (NWP), which indirectly intensifies the WPSH. As a result, the PJ pattern is triggered and provides a favorable large-scale circulation condition for the growth of rainfall.