摘要: |
利用卫星观测、ERA5和 GDAS再分析数据等对东亚冬季风冷涌引发的一次马来西亚极端暴雨洪水事件进行了分析。结果表明:在东亚冬季风背景下,东亚大槽重建、地面冷高压加强以及日本岛-西北太平洋爆发性气旋发展等为冷涌形成提供了有利的环流背景;热带气旋“雷伊”影响及中高纬度冷空气的持续补充进一步延长了冷涌维持时间。冷涌与热带气旋外围环流、热带东风气流、“海洋性大陆”(Maritime Continent)西部地形等之间的相互作用导致了冷涌涡旋(Borneo Vortex)的产生和维持,为强降水提供了持续的涡旋动力条件。冷涌气流与赤道偏东气流之间的辐合以及与马来半岛海岸线地形的相互作用进一步促进低层动力条件的增强,导致多阶段动力辐合条件的接连作用。冷涌气流所构建的从南海到马来半岛的水汽通道是降水的主要水汽源,其中偏东分量的水汽输入最强、其次为偏北分量,导致对流层低层强水汽辐合条件的产生。冷涌气流南侵过程中,受广阔海洋影响,温湿条件不断增加,且越低层越明显,从而导致不稳定条件的产生和加强。在对流层低层高温、高不稳定能量以及整层高湿环境下,有利于中尺度对流系统发展和高效暖云降水的产生。 |
关键词: 冷涌 冷涌涡旋;暴雨洪水;水汽 |
DOI:10.16032/j.issn.1004-4965.2024.062 |
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Causes of an East Asian Winter Cold Surge and Its Impact on a Flash Flood Event in Malaysiaia |
YANG Shunan1,2, ZHOU Ningfang1
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1. National Meteorological Center, Beijing 100081, China;2. CMA-HHU (China Meteorological Administration-Hohai University) Joint Laboratory for Hydrometeorological Studies, Beijing 100081, China
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Abstract: |
This study analyzed the impact of a cold surge during the East Asian winter monsoon on an extreme flash flood event in Malaysia using satellite observations and reanalysis data including ERA5 from the European Centre for Medium-Range Weather Forecasts and data from the Global Data Assimilation System. The results indicate that, with the East Asian winter monsoon in the Northern Hemisphere, the redevelopment of the East Asian trough, the strengthening of surface cold high pressure, and the development of explosive cyclones over Japan and Northwestern Pacific jointly provided favorable large- scale circulation background for the cold surge formation. The impact of Tropical Cyclone Rai and the continuous influx of cold air from mid and high latitudes prolonged the duration of the cold surge. Interactions between the cold surge, the peripheral circulation of the tropical cyclone, the easterly airflow in tropical regions, and the topography of the western Maritime Continent led to the formation and maintenance of the Borneo Vortex, providing continuous dynamic conditions for heavy precipitation. The convergence between the cold surge and the equatorial easterly airflow, along with the interaction between the cold surge and the topography of the Malay Peninsula’s coastline, further enhanced low-level dynamic conditions, which then led to the continuous influence of multi-stage dynamic convergence. The water vapor channel established by the cold surge from the South China Sea to the Malay Peninsula was the main source of precipitation moisture, with the easterly component contributing the strongest water vapor input, followed by the northerly component. This pathway created strong water vapor convergence conditions in the lower troposphere near the Malay Peninsula. As the cold surge moved southward, its temperature and humidity conditions are intensified by the vast ocean surface, particularly in the lower layers, leading to the generation and strengthening of unstable conditions. The warm, energetic, and highly humid environment in the lower troposphere was conducive to the development of mesoscale convective systems and the generation of efficient warm-cloud precipitation. |
Key words: cold surge Borneo Vortex flash flood water vapor |