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Convective organizing and upscale development processes explored through idealized numerical experiments.

机译：通过理想的数值实验探索了对流组织和高端发展过程。

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摘要

Deep convective systems over many parts of the globe organize into similar complexes with a common evolution. The purpose of this study is to gain insight into basic fundamental processes responsible for convection organizing into large clusters such as Mesoscale Convective Complexes (MCCs) and to find a dynamically meaningful distinction between MCC-like clusters and other deep convection. These matters are investigated through idealized numerical experiments using a cloud-resolving, nonhydrostatic model. Modeling issues involving convective initiation and heterogeneous nonuniformly sheared base states with Coriolis effect are addressed.; The hypothesis of organization and growth by mesoscale shear instability was studied with dry experiments and explicit cloud microphysics in a linearly unstable vertical shear profile. The shear instability was not manifested. Instead, the dry box experiments gave Rayleigh rolls and the moist experiment resulted in a heavy-raining convective system organized by short gravity waves, the cold dome, and a mesoscale crossover downdraft. The mesoscale downdraft occurred beneath patches of negative potential vorticity (PV), suggesting importance of the PV signature in mesoscale organization.; The PV signature and mesoscale circulations as a response to thermal forcing were studied in more detail through dry, initially barotropic experiments with specified, spatially fixed heating distributions and with heating proportional to vertical motion. Particular attention was given to warm core vortex structures resembling those other investigators found associated with MCCs and serving as seeds for tropical cyclones.; Warm core vortices were produced in many of the experiments through a variety of mechanisms. Some interesting scenarios producing mesoscale vortices were a layer of cooling resembling melting from an MCC anvil, a line of deep heating, and favorably arranged cloud-scale heating centers. Heating inside a pre-existing warm core vortex favored intensification due to radial (horizontal) vorticity contributions to PV generation.; The experiments provide an interesting basis for discussing balance or lack of it and the adjustment process for mesoscale disturbances. Thin, slow internal waves can reduce the Rossby radius to the vortex scale.; This research suggests that production or organization around a rotationally balanced mesovortex is the dynamically distinguishing factor of MCC-like systems.
机译：全球许多地方的深层对流系统组成具有共同演化的类似复合体。这项研究的目的是深入了解对流组织成大型集群（如中尺度对流复合体（MCC））的基本基本过程，并找到类似于MCC的集群与其他深对流之间的动态有意义的区别。这些问题是通过使用云解析非静水模型进行的理想化数值实验研究的。解决了涉及对流引发和具有科里奥利效应的非均匀非均匀剪切基态的建模问题。中尺度剪切不稳定性对组织和生长的假设是通过干实验和显式云微观物理学研究的，其线性不稳定的垂直剪切剖面中。没有表现出剪切不稳定性。取而代之的是，干箱实验给出了瑞利滚子，而潮湿实验则产生了由短重力波，冷穹顶和中尺度交叉降落气流组成的大雨对流系统。中尺度下降气流发生在负潜在涡度（PV）斑块之下，表明PV信号在中尺度组织中很重要。 PV签名和中尺度循环作为对热强迫的响应，是通过干燥的，最初的正压实验进行了更详细的研究，该实验具有特定的，空间固定的加热分布以及与垂直运动成比例的加热。尤其注意了温暖的核心涡旋结构，该结构类似于与MCC相关的其他研究者，并用作热带气旋的种子。在许多实验中，通过各种机制产生了温暖的核心涡旋。产生中尺度涡旋的一些有趣场景是类似于MCC砧的融化层一样的冷却层，深层加热线以及布置良好的云级加热中心。由于径向（水平）涡对PV产生的贡献，预先存在的暖核涡内部的加热有利于强化。实验为讨论平衡的平衡或缺乏以及中尺度干扰的调节过程提供了有趣的基础。缓慢的内部细波可以将Rossby半径减小到涡旋尺度。这项研究表明，围绕旋转平衡的中涡的产生或组织是MCC类系统的动态区分因素。

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  • 作者

    Jascourt, Stephen D.;

  • 作者单位

    The University of Wisconsin - Madison.;

  • 授予单位 The University of Wisconsin - Madison.;
  • 学科 Physics Atmospheric Science.
  • 学位 Ph.D.
  • 年度 1997
  • 页码 281 p.
  • 总页数 281
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 大气科学（气象学）;
  • 关键词

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