Stages in the energetics of baroclinic systems
Stages in the energetics of baroclinic systems
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DOI：
10.3402/tellusa.v47i5.11553
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发表时间：
1995-10
期刊：
影响因子：
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通讯作者：
I. Orlanski;J. Sheldon
中科院分区：
文献类型：
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作者：
I. Orlanski;J. Sheldon
从几个理想化的和案例研究的结果被绘制在一起，形成一个全面的图片“下游斜压演变”使用当地的能量。这种新的观点提供了一个补充替代更传统的描述气旋的发展。这些额外的见解之所以成为可能，主要是因为当地的能量学方法允许人们定义一个能量通量矢量，它准确地描述了能量分散的方向，并量化了邻近系统在当地发展中的作用。在这个观点中，系统的能量学的发展被分为三个阶段。在第1阶段，一个预先存在的扰动以及上游的初始槽失去能量通过非地转位势通量直接通过下游的干预脊，产生一个新的能量中心。在第二阶段，这个新的能量中心蓬勃发展，首先是由于这些通量的收敛，后来通过斜压转换以及。随着中心的成熟，它开始通过位势通量向低压槽东侧输出能量，从而形成另一个能量中心。在第三阶段，这个新的能量中心继续增长，而波谷西侧的能量中心由于来自较老的上游系统的通量的能量供应减少以及其自身向下游输出能量的结果而衰减。随着东部能源中心的成熟，它向下游出口能源，这一顺序重新开始。美国“93暴雪”被用作一个新的案例研究，以测试这种概念序列可能适用的限制，以及增加目前有限的案例研究。结果表明，尽管异常的规模的事件，与暴雪相关的槽的演变符合下游斜压演变的概念图相当好，与位势通量在三个方面起着至关重要的作用。首先，来自太平洋一个老的、正在衰减的系统的通量在北美西海岸汇聚，在那里形成了一个动能中心，并改变了急流，导致整个动能中心大范围延伸到墨西哥。其次，来自西北气流延伸的能量通量在低压槽以东强烈汇聚，在墨西哥湾西北部上空产生动能爆炸性增长，此后不久发生斜压转换。最后，大槽西侧冷平流中强烈的斜压转换所产生的动能通过位势通量非常有效地传递到大槽东侧的能量中心。DOI：10.1034/j.1600-0870.1995.00108.x
The results from several idealized and case studies are drawn together to form a comprehensive picture of “downstream baroclinic evolution” using local energetics. This new viewpoint offers a complementary alternative to the more conventional descriptions of cyclone development. These additional insights are made possible largely because the local energetics approach permits one to define an energy flux vector which accurately describes the direction of energy dispersion and quantifies the role of neighboring systems in local development. In this view, the development of a system's energetics is divided into three stages. In Stage 1, a pre-existing disturbance well upstream of an incipient trough loses energy via ageostrophic geopotential fluxes directed downstream through the intervening ridge, generating a new energy center there. In Stage 2, this new energy center grows vigorously, at first due to the convergence of these fluxes, and later by baroclinic conversion as well. As the center matures, it begins to export energy via geopotential fluxes to the eastern side of the trough, initiating yet another energy center. In Stage 3, this new energy center continues to grow while that on the western side of the trough decays due to a dwinding supply of energy via fluxes from the older upstream system and also as a consequence of its own export of energy downstream. As the eastern energy center matures, it exports energy further downstream, and the sequence begins anew. The USA “Blizzard of'93” is used as a new case study to test the limits to which this conceptual sequence might apply, as well as to augment the current limited set of case studies. It is shown that, despite the extraordinary magnitude of the event, the evolution of the trough associated with the Blizzard fits the conceptual picture of downstream baroclinic evolution quite well, with geopotential fluxes playing a critical role in three respects. First, fluxes from an old, decaying system in the Pacific were convergent over the west coast of North America, creating a kinetic energy center there and modifying the jet, resulting in a large extension of the overall kinetic energy center well into Mexico. Second, energy fluxes from this extension of the northwesterly flow were strongly convergent east of the trough, producing explosive growth of kinetic energy over the northwestern Gulf of Mexico, with baroclinic conversion following shortly thereafter. Lastly, the kinetic energy generated by the vigorous baroclinic conversion in the cold advection on the west side of the trough was very effectively transferred to the energy center on the east side of the trough via geopotential fluxes. DOI: 10.1034/j.1600-0870.1995.00108.x