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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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国家自然科学基金项目 41730963、91637312、91937302,中国科学院前沿科学重点研究项目 QYZDY-SSW-DQC018


Effect of Potential Vorticity on the Formation, Development, and Eastward Movement of a Tibetan Plateau Vortex and Its Influence on Downstream Precipitation
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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(Modern-Era Retrospective analysis for Research and Applications)再分析资料和TRMM(Tropical Rainfall Measurement Mission)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 June 28 to July 1, 2016, a Tibetan Plateau (TP) vortex was generated, which developed and moved eastward to the subtropical region of China, resulting in precipitation in the lower reaches of the Yangtze River. In this study, we used the potential vorticity (PV) to understand this process based on data from the second Modern-Era Retrospective analysis for Research and Applications (MERRA-2) and precipitation data from the Tropical Rainfall Measurement Mission (TRMM). The results indicate that surface heating over the TP causes obvious diurnal variation, changing from a heat source in the daytime to a source of cold at night and directly influencing the vertical gradient of diabatic heating. Negative PV is generated near the surface in the daytime and positive PV is generated at night, which reflects a prominent diurnal cycle. When the nighttime generation of positive PV becomes very strong and cannot be compensated for by the daytime generation of negative PV, a low-vortex forms over the TP. By the time this low-vortex system moves to the eastern TP, diabatic heating associated with strong precipitation reinforces this vortex. As the low-vortex system continues to propagate eastward, the PV advection increases with height and serves as a large circulation background over the middle and lower reaches of the Yangtze River, which favors the development of rising air and results in the occurrence of heavy precipitation.

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马婷,刘屹岷,吴国雄,毛江玉,张冠舜.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.大气科学,2020,44(3):472~486 MA Ting, LIU Yimin, WU Guoxiong, MAO Jiangyu, ZHANG Guanshun. Effect of Potential Vorticity on the Formation, Development, and Eastward Movement of a Tibetan Plateau Vortex and Its Influence on Downstream Precipitation. Chinese Journal of Atmospheric Sciences (in Chinese),2020,44(3):472~486

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  • 收稿日期:2018-12-26
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  • 在线发布日期: 2020-05-26
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