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CN 11-1768/O4

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青藏高原低涡形成、发展和东移影响下游暴雨天气个例的位涡分析
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1.南京信息工程大学气象灾害教育部重点实验室;2.中国科学院大气物理研究所大气科学与地球流体力学数值模拟国家重点实验室;3.中国科学院大学

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国家自然科学基金项目(批准号:41730963,91437219,91637312)、中国科学院前沿科学重点研究项目(QYZDY-SSW-DQC018)


Potential Vorticity diagnosis on the formation, development and eastward movement of a Tibetan Plateau Vortex and it’s influence on the downstream precipitation
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1.State Key Laboratory of Numerical Modelling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG);2.LASG

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    摘要:

    2016年6月28日至7月1日在我国副热带地区发生了一次青藏高原低涡形成、发展及东传引发长江中下游地区暴雨天气的过程。本文利用MERRA2再分析资料和TRMM降水资料对该过程进行位涡诊断分析。结果表明,夏季青藏高原地表加热具有强烈的日变化。高原地表加热由白天感热加热源到夜间辐射冷却源的转变直接影响高原上空非绝热加热率的垂直梯度,使高原近地层白天有位涡耗散,夜间有位涡制造,呈现明显的昼夜循环。当夜间的位涡制造异常强,以至不为白天的耗散所抵消时,通常位涡制造的昼夜循环被破坏,高原低涡形成,低涡周围随之出现降水。当低涡中心移动至高原东部时,中心附近伴随有强烈的降水,显著的凝结潜热加热使位涡中心增强,高原低涡进一步发展。随着低涡系统继续向东移出高原,长江中下游地区中高层出现位涡平流随高度增加的大尺度动力背景,上升运动发展,最终导致强降水发生。

    Abstract:

    During the period of 28 June to 1 July, 2016, a Tibetan Plateau(TP) Vortex was generated, which then developed and moved eastward to subtropical region of China, resulting in precipitation in the lower reaches of the Yangtze River. The potential vorticity (PV) is used to diagnose the process by using the second Modern-Era Retrospective analysis for Research and Applications (MERRA-2) data and the Tropical Rainfall Measuring Mission (TRMM) precipitation data. Results indicate that surface heating over the TP pocesses obvious diurnal variation. It changes from heat source in the daytime to cold source in the night and directly influences the vertical gradient of diabatic heating. Negative PV is generated near the surface in daytime and positive PV is generated in night, demonstrating a prominent diurnal cycle. When the night-time positive PV generation becomes very strong and cannot be compensated for by the daytime negative PV generation, the TP low vortex is formed. By the time the low vortex system moves to the eastern TP, diabatic heating associated with strong precipitation reinforces the vortex. As the low vortex system continues to propagate eastward, the PV advection increasing with height acts as the large circulation background over the middle and lower reaches of the Yangtze River, which is in fever of the development of air ascent, resulting in occurrence of precipitation.

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  • 收稿日期:2018-12-26
  • 最后修改日期:2019-03-21
  • 录用日期:2019-04-11
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