Differences between decadal decreases of boreal summer rainfall in southeastern and southwestern China in the early 2000s
Differences between decadal decreases of boreal summer rainfall in southeastern and southwestern China in the early 2000s
复制标题
2000年代初期中国东南部和西南地区夏季降水年代际减少的差异
DOI：
10.1007/s00382-018-4408-8
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发表时间：
2019
期刊：
影响因子：
4.6
通讯作者：
Sun Yuan
中科院分区：
文献类型：
--
作者：
Ha Yao;Zhong Zhong;Hu Yijia;Zhu Yimin;Zang Zengliang;Zhang Yun;Yao Yao;Sun Yuan
在年代际尺度上，2003-2012年华南夏季（6-8月）降雨量较上一时期1993-2002年显着减少。本研究调查了自 2000 年代初以来中国东南部 (SEC) 和中国西南部 (SWC) 夏季降雨量逐年减少的不同过程。还探讨了这些变化的可能机制。结果表明，2003-2012年，SEC（SWC）地区的小、中、强（轻、中）三个等级的日降雨总量显着低于前期1993-2002年的14.4%（8.2%）。由轻、中、重（轻、中）等级变化引起的历时降雨量变化占 1993-2002 年和 2003-2012 年 SEC（SWC）夏季总降雨量差异的 90%（86%）。通过回归和综合分析发现，2000年代初夏季降水年代际变化的原因对于两个地区来说是不同的。 SEC 降雨量减少的原因是来自南海的西南气流减少了水汽输送，这是由于西太平洋副热带高压 (WPSH) 向北移动，以及北太平洋西部 (WNP) 到日本东部的海面温度 (SST) 变冷所致。 SWC 降雨量减少可以用从孟加拉湾西南/西风输送的水汽减少来解释，这是由 2000 年代初以来南亚季风减弱引起的，这可能与北印度洋 (NIO) 的海温变暖有关。此外，与NIO变暖和WNP冷却相关的异常反气旋环流形成了西南-东北方向的高压带。副高向北移动，从日本东部延伸至孟加拉湾。 SEC和SWC位于“哑铃形”副热带高压带南翼，盛行东北风。因此，自2003年以来，从南海和孟加拉湾到SEC和SWC的水汽输送在年代际时间尺度上均有所减少。虽然两个不同区域的降雨变化涉及不同的物理动力过程，但年代际尺度上夏季降雨的减少与2000年代初发生的全球尺度海温异常格局和背景大气环流的变化密切相关。
On decadal time scale, the boreal summer (June–August) rainfall over southern China significantly decreased during the epoch 2003–2012 compared to that in the preceding epoch 1993–2002. This study investigates different processes involved in the decadal decreases in summer rainfall over southeastern China (SEC) and southwestern China (SWC) since the early 2000s. Possible mechanisms for these changes are also explored. Results show that the daily total amount of rainfall in light, moderate and heavy (light and moderate) grades during 2003–2012 is significantly lower than that in the preceding period 1993–2002 by 14.4% (8.2%) over SEC (SWC) region. The epochal rainfall change caused by changes in the light, moderate and heavy (light and moderate) grades accounts for 90% (86%) of total summer rainfall difference between the epoch 1993–2002 and 2003–2012 over SEC (SWC). Based on regression and composite analyses, it is found that the reasons for decadal changes in summer rainfall in the early 2000s are different for the two regions. The rainfall decrease over SEC is attribute to reduced moisture transport by the southwesterly flow from the South China Sea, which is caused by the northward-shift of the western Pacific subtropical high (WPSH) in association with the sea surface temperature (SST) cooling over the western North Pacific (WNP) to the east of Japan. The rainfall decrease over SWC can be explained by reduced moisture transported by the southwesterly/westerly from the Bay of Bengal, which induced by the weakened South Asian monsoon since the early 2000s that is plausibly related to SST warming over the northern Indian Ocean (NIO). Furthermore, the anomalous anticyclonic circulations connected to the NIO warming and WNP cooling make a southwest-northeast-oriented high pressure band. WPSH shifts northward, extending from east of Japan to the Bay of Bengal. SEC and SWC are located along the southern flank of the “dumbbell-shaped” subtropical high band, where the northeasterly prevails. As a result, moisture transports from the South China Sea and the Bay of Bengal to SEC and SWC both decrease on the decadal time scale since 2003. Although different physical-dynamical processes are involved in rainfall changes over the two different regions, the summer rainfall decreases on the decadal time scale are closely related to the shifts in SSTA pattern and background atmospheric circulation on global-scale that occurred in the early 2000s.