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首页> 外文学位 >The role of jet streak regeneration forced by a deepening continental planetary boundary layer in the explosive surface cyclogenesis of 28 March 1984.
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The role of jet streak regeneration forced by a deepening continental planetary boundary layer in the explosive surface cyclogenesis of 28 March 1984.

机译：1984年3月28日，大陆深层行星边界层加深推动的喷气条纹再生在爆炸表面回旋作用中的作用。

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摘要

Numerical modeling studies of the 28-29 March 1984 explosive cyclogenesis case revealed that key features within the antecedent environment can be traced back into Texas 33 hours before the event. Experiments showed that unseasonable lower-tropospheric warming, facilitated by minimal soil moisture, strong surface sensible heating, and down slope flow off the Mexican Plateau, forced the development of a deep Planetary Boundary Layer (PBL) and a reduction of surface pressures over southern Texas. The hydrostatic response to the heating forced a mid-level thickness perturbation and an intensification of the mid-tropospheric pressure gradient force. Large divergence tendencies within the mid-level flow initiated differential vertical motions, folding of the isentropes, and the formation of a Mid-tropospheric Unbalanced Front (MUF).;Coincident with the development in southern Texas, the PBL over the Edwards Plateau deepened to near the 550 mb level. Vertical fluxes of horizontal momentum led to the formation of a lower-tropospheric mesoridge, which resulted in parcel divergence and an acceleration towards the lower surface pressure over southern Texas. The accompanying cold air advection induced an intensification of the mid-level pressure gradient force and a rapid turning of the winds off the Mexican Plateau. The proximity of hot air over elevated Plateau region facilitated frontogenesis by cross-stream confluence deformation. This incipient jet/front system propagated eastward across Texas where it encountered a strong SE to NW directed pressure gradient force. The advancement of the Polar Front at low-levels enhanced the mid-tropospheric pressure gradient force over the Arklatex and accelerated the jet northeastwards into Mississippi by 1200 UTC 28 March.;Mid-tropospheric jet/front system began to decay after 1200 UTC 28 March. The thermally direct circulation about the weakening frontal system sagged southeastwards and phased with a thermodynamically indirect circulation surrounding the large-scale system. This merger of large-scale and subsynoptic scale systems provides a focusing mechanism for the initiation of a squall line. Vertical wind shear, surface sensible heating and weak static stability provide an environment conducive to explosive cyclogenesis.
机译：1984年3月28日至29日爆炸性循环发生案例的数值模型研究表明，在先环境中的关键特征可以追溯到事件发生前33个小时。实验表明，对流层低层变暖是由最低的土壤湿度，强烈的地表感热和墨西哥高原的下坡流造成的，这迫使深层行星边界层（PBL）的发展和德克萨斯州南部的地表压力降低。对加热的静水压力迫使中等厚度的扰动和对流层中压梯度力的增强。中层水流的大趋异趋势引发了不同的垂直运动，等熵线的折叠以及中层对流层不平衡锋（MUF）的形成;;与德克萨斯州南部的发展巧合，爱德华兹高原上的PBL加深到接近550 mb的水平。水平动量的垂直通量导致形成一个较低的对流层中脊，这导致了包裹发散和向德克萨斯南部南部较低表面压力的加速。伴随的冷空气平流引起中层压力梯度作用力的增强，并且使风迅速离开墨西哥高原。热空气在高原地区的接近通过横流汇合变形促进了锋生。这个初始的射流/前部系统向东传播，穿过德克萨斯，在那里遇到了强烈的东南向西北方向的压力梯度力。极地锋的低空推进增强了Arklatex对流层中的压力梯度作用力，并于3月1200 UTC加速了向东北方向进入密西西比的射流； 3月28日1200 UTC之后，中对流层射流/前锋系统开始衰减。 。围绕弱化的额叶系统的热直接循环向东南方向下陷，并与围绕大型系统的热力学间接循环形成阶段。大规模和亚天气尺度系统的这种合并为provides行的启动提供了一种聚焦机制。垂直风切变，表面显热和弱的静态稳定性为爆炸性循环生成提供了有利的环境。

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  • 作者

    Rozumalski, Robert Anthony.;

  • 作者单位

    North Carolina State University.;

  • 授予单位 North Carolina State University.;
  • 学科 Physics Atmospheric Science.
  • 学位 Ph.D.
  • 年度 1997
  • 页码 360 p.
  • 总页数 360
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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