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ISSN 1006-9895

CN 11-1768/O4

青藏高原三江源和河湾区夏季降水变化特征及对高原夏季风的响应
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中国气象局武汉暴雨研究所

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第二次青藏高原综合科学考察研究项目2019QZKK0105


Variations of summer precipitation over the Three-River Headwaters region and Yarlung Zangbo River basin and response to Tibetan Plateau summer monsoon
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Hubei Key Laboratory for Heavy Rain Monitoring and Warning Research,Institute of Heavy Rain,China Meteorological Administration

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    摘要:

    本文利用1981-2020年观测数据和ERA5再分析资料,将青藏高原腹地三江源和东南重要水汽通道河湾区作为典型研究区域,分析了降水不同时间尺度变化特征及其典型强弱年对高原季风环流系统的响应,结果表明:(1)三江源和河湾区降水的季节变化均呈双峰型分布,峰值出现在7月初和8月下旬。夏季降水在21世纪初发生年代际转折,尤其是三江源降水量在近20年增加明显。两个高原季风指数DPMI(Dynamic Plateau Monsoon Index)和ZPMI(Zhou Plateau Monsoon Index)的夏季风爆发时间均超前于河湾区和三江源降水的明显增加期。三江源夏季降水年际变化与两个高原夏季风指数有较好的相关性。三江源与河湾区虽然相邻很近,但三江源夏季降水受高原季风影响程度远大于河湾区。当高原夏季风增强(减弱)时,三江源降水量偏多(少)。(2)三江源降水偏多年,南亚高压偏东偏强,低层高原主体低压异常,有利于西南风和东南风在三江源区域交汇,南方暖湿空气能够深入高原腹地导致水汽辐合偏强。河湾区降水偏多年,河湾区及整个高原主体附近高度场并没有明显异常,河湾区的水汽输送主要有两条路径,一条来自孟加拉湾沿高原南坡的西南路径,另一条来自中亚地区穿过高原上空的西北路径,两条路径在高原东侧汇合继续向东输送。

    Abstract:

    Based on precipitation and ERA5 reanalysis datasets from 1981 to 2020, this paper analyzed the variation characteristics of precipitation at different time scales over the Three-River Headwaters region (TRHR) and Yarlung Zangbo River basin (YZRB) and their responses to the Tibetan Plateau monsoon. Results show that: (1) The seasonal variation of precipitation over the TRHR and YZRB both show bimodal distribution, the peaks appear in early July and late August. The interdecadal transitions of summer precipitation occur in the early 21st century, especially the TRHR precipitation increases significantly during recent 20 years. The onset time of summer monsoon in Dynamic Plateau Monsoon Index (DPMI) and Zhou Plateau Monsoon Index (ZPMI) are ahead of precipitation increase period over the TRHR and YZRB. The interannual variation of summer precipitation over the TRHR has a good correlation with two plateau summer monsoon indexes.. Although the TRHR is close to the YZRB, the summer precipitation of TRHR is much more affected by the Tibetan plateau monsoon than that of YZRB. When the Tibetan Plateau summer monsoon strengthens (weakens), the TRHR precipitation is more (less). (2) In wet TRHR years, the South Asian High is stronger and more eastward, while the pressure at low-level over the main body of the plateau is lower than in dry years. These situations are conducive to the intersection of southwest wind and southeast wind over the TRHR, so that the warm and humid air from the South can go deep into the hinterland of plateau, resulting in stronger water vapor convergence. In wet YZRB years, there is no obvious anomaly in pressure field near YZRB or the Tibetan Plateau. The water vapor transport over YZRB mainly has two paths, one is the southwest path which from the Bay of Bengal along the south slope of the plateau, and the other one is the northwest path which from Central Asia and through the plateau. The two paths converge at the east side of the plateau and continue to transport eastward.

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  • 收稿日期:2022-05-27
  • 最后修改日期:2022-07-04
  • 录用日期:2022-07-20
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