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Evolution and Structure of the Mesoscale Convection and Its Environment: A Case Study during the Early Onset of the Southeast Asian Summer Monsoon

机译:中尺度对流及其环境的演变,结构-以东南亚夏季风初爆发为例

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摘要

The evolution and structure of mesoscale convection in the South China Sea (SCS) region are documented for the first time mainly using the dual-Doppler radar dataset collected during the South China Sea Monsoon Experiment (SCSMEX) in 1998. In particular, this study focuses on the convection associated with a subtropical frontal passage during the early onset of the southeast Asian monsoon (SEAM). For the case of 15 May 1998. interaction between the tropical monsoon flow and frontal circulation played an important role in the evolution and structure of mesoscale convection. In the prefrontal region, the southwesterly monsoon flow converged with the southwesterly frontal flow to generate northeast-to-southwest-oriented convection. In the postfrontal region, the southwesterly monsoon flow converged with the northerly frontal flow to produce a wide convective line with an east-to-west orientation. In addition, the convergence between the southerly monsoon flow and the northerly postfrontal flow generated deeper and stronger low-level convergence. The postfrontal convection was more intense and deeper than the prefrontal convection. The precipitation and kinematic structure of mesoscale convection were studied with special attention to significant departures from archetypal tropical oceanic convection. On 15 May, prefrontal convection showed a straight upward rainfall and updraft pattern with little tilt as a result of moderate vertical wind shear. The maximum low-level convergence and updraft were 20―30 km behind instead of within 1―2 km of the leading edge. Although the convection was intense with maximum reflectivity over 50 dBZ, both pre- and postfroatal convection had a very limited stratiform region as a result of a dry environmental upper layer. The observed mesoscale convection had a tendency to form stratiform rain ahead of the convective rain, and two different modes of leading stratiform structure were found separately in pre- and postfrontal convection.
机译:首次主要利用1998年南海季风试验(SCSMEX)期间收集的双多普勒雷达数据集记录了南海(SCS)地区中尺度对流的演变和结构。特别是,该研究重点是东南亚季风(SEAM)爆发初期与亚热带额叶通道有关的对流。以1998年5月15日为例,热带季风流与额叶环流之间的相互作用在中尺度对流的演变和结构中起着重要作用。在前额叶区域,西南季风流与西南额叶流汇合,产生东北向西南方向的对流。在后额叶地区,西南季风流与北额锋流汇合,形成一条东西向的宽对流线。此外,南风季风流与北风后额流之间的汇合产生了更深,更强的低层汇合。后额对流比额前对流更激烈和更深。对中尺度对流的降水和运动学结构进行了研究,并特别注意与典型热带对流的重大偏离。 5月15日,由于适度的垂直风切变,前额对流显示出笔直的向上降雨和上升气流模式,几乎没有倾斜。最大的低层收敛和上升气流落后于前沿20至30公里,而不是前沿1-2公里之内。尽管对流很强,最大反射率超过50 dBZ,但由于干燥的环境上层,前和后对流都具有非常有限的层状区域。观测到的中尺度对流有在对流降雨之前形成层状雨的趋势,并且在前对流和后额对流中分别发现了两种不同的主导层状结构模式。

著录项

  • 来源
    《Monthly Weather Review》 |2004年第5期|p.1104-1120|共17页
  • 作者

    JIAN-JIAN WANG;

  • 作者单位

    Mesoscale Atmospheric Processes Branch, NASA Goddard Space Flight Center, Greenbelt, MD 20771;

  • 收录信息
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 大气科学(气象学);
  • 关键词

  • 入库时间 2022-08-18 00:04:38

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