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首页> 外文学位 >The roles of wave-zonal flow interaction and orographic forcing on the generation of low-frequency variability in a newly developed GCM.
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The roles of wave-zonal flow interaction and orographic forcing on the generation of low-frequency variability in a newly developed GCM.

机译：在新开发的GCM中，波-地流相互作用和地形强迫对低频变化的产生的作用。

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摘要

A full-Galerkin GCM is developed for mechanistic studies on the generation mechanisms of low-frequency variability. The numerical implementation and baroclinic dynamics of this newly developed GCM are carefully tested, and its sensitivity to vertical resolution and to parameterized physics are also investigated.; The role of wave-zonal flow interaction in generating low-frequency variability is studied in a GCM simulation with zonally symmetric forcing. Low-frequency variations are observed in the strength and the location of the zonal mean jet. A zonal index based on EOF analysis is used to describe this low-frequency phenomenon. Composite analysis shows that both the zonal mean circulations and the eddy properties are changed during the zonal flow vacillation. The Eulerian-mean angular momentum budget analysis indicates that wave-zonal flow interaction through eddy momentum flux convergence is the dominant process to maintain the zonal flow vacillation. Eddy forcing associated with eddy heat flux convergence tends to destroy the zonal wind anomalies associated with the zonal flow vacillation. Comparison between eddy forcing from various time-scales of eddies shows that synoptic time-scale of eddies provide most of the forcing to maintain zonal flow vacillation. Wind anomalies in the low-index and the high-index phases of the vacillation are self maintained by the interaction between the zonal flow and this time-scale eddies. This self-maintenance mechanism is demonstrated by two lifecycle experiments. A time-lag phenomenon in the establishment of zonal wind anomalies suggests that the mechanism to trigger the atmosphere to shift between the self-maintained phases may operate in higher latitudes.; Analyses of variability in the mountain simulations show that a large-scale mountain not only affects the geographical distribution but also the amount of atmospheric variability. Orographic forcing influences the amplitudes of high-frequency transients and affects the propagation of intermediate-frequency transients. As a results of its different influences on various time-scales of variability, the high-, intermediate-, and low-frequency variability are separated into three different geographic locations. More high-frequency and low-frequency variability is localized in the jet exit region, while the intermediate-frequency variability is concentrated in the upstream region of the mountain. Although the amounts of high-frequency and intermediate-frequency variability are reduced by the orographic forcing, additional of low-frequency variability is generated by the orographic forcing. Barotropic instability of the orographically forced stationary waves and the direct interaction between the zonal flow vacillation and the mountain itself are possible mechanisms responsible for the increase. EOF analyses shows that zonal flow vacillation generated through the wave-zonal flow vacillation is still an important mechanism to generate low-frequency variability in the mountain hemisphere, but this process is localized in the region of the storm track.
机译：开发了全Galerkin GCM，用于研究低频可变性的产生机理。仔细测试了这种新开发的GCM的数值实现和斜压动力学，并研究了其对垂直分辨率和参数化物理学的敏感性。在具有区域对称强迫的GCM模拟中，研究了波-地流相互作用在产生低频变化中的作用。在区域平均射流的强度和位置中观察到低频变化。基于EOF分析的区域索引用于描述这种低频现象。综合分析表明，在纬向流量波动过程中，纬向平均环流和涡流特性均发生了变化。欧拉平均角动量预算分析表明，涡流动量通量收敛引起的波-地流相互作用是维持地带水流波动的主要过程。与涡流热通量收敛相关的强迫涡流倾向于破坏与纬向气流波动相关的纬向风异常。从不同时间尺度的涡流强迫之间的比较表明，天气总尺度的涡流提供了大部分的强迫作用，以维持区域气流的波动。波动的低指数和高指数阶段的风异常是通过纬向流与该时间尺度涡旋之间的相互作用自行维持的。通过两个生命周期实验证明了这种自我维护机制。在纬向风异常建立过程中存在时滞现象，这表明触发大气层在自保持相之间转换的机制可能在较高纬度上起作用。山区模拟中的变异性分析表明，大型山区不仅影响地理分布，而且还会影响大气变异性。地形强迫影响高频瞬变的幅度，并影响中频瞬变的传播。由于其对各种时间尺度的可变性的不同影响，高，中和低频可变性被分为三个不同的地理位置。更多的高频和低频可变性位于喷射出口区域，而中频可变性则集中在山脉的上游区域。尽管通过地形强迫减少了高频和中频可变性的量，但是通过地形强迫产生了额外的低频可变性。地形强迫静波的正压失稳以及地层水流波动与山脉本身之间的直接相互作用可能是造成这种增加的原因。 EOF分析表明，通过波带流波动产生的带流波动仍然是在山半球产生低频变化的重要机制，但这一过程局限于风暴路径区域。

著录项

  • 作者

    Yu, Jin-Yi.;

  • 作者单位

    University of Washington.;

  • 授予单位 University of Washington.;
  • 学科 Physics Atmospheric Science.
  • 学位 Ph.D.
  • 年度 1993
  • 页码 251 p.
  • 总页数 251
  • 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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