On the Marsupial Theory for Tropical Cyclogenesis Within Tropical Wave and Monsoon Trough Environments: A Multiscale Observational, Modeling and Theoretical Study

弱旋转对流区何时、何地以及如何发展成为全面的热带气旋，仍然是大气动力学中一个基本上尚未解决的问题，尽管这是一个对预报高影响天气具有异常重大影响的问题。在这个项目中，Montomgery和他的团队将探索他的“有袋类假说”，该假说将热带气旋发生与热带波的临界层联系起来。“有袋类假说”包括三个子假说：1)形成热带气旋的雷暴弱旋转区域在热带行波的临界层或转向层形成。在这个高度，波速等于背景风的波速，因此流体，包括弱旋转的“原涡旋”，随着波浪移动。2)对于较强的波浪，临界高度演变成一个临界层，形成一个封闭的流线口袋。在这个口袋中，发展中的涡旋部分地被隔离或保护(因此是“有袋类”理论)，不受干燥空气的卷吸和垂直切变的有害影响。3)热带波被与这些原始涡旋相关的潜热释放放大。这些假设将在观测分析和模拟程序中得到验证。对大气数据的初步分析表明，正如假设的那样，非洲东风波的临界层是热带气旋发展的首选区域，波槽内的对流有助于维持该波。这些分析将扩展到季风槽个例，气旋发生个例将与不发生气旋发生的零个例相平衡。热带再分析的问题--结果受到积云参数化方案的强烈制约--将通过分析来自其他来源的数据来绕过，包括热带降雨测量任务(TRMM)卫星数据和2008年夏秋T-PARC(观测系统研究和可预报性实验(THORPEX)太平洋亚洲区域运动)现场活动期间获得的现场数据。模式试验将使用天气研究和预报(WRF)模式进行。干实验将研究热带波产生原始涡旋时的涡旋脱落。对积云对流进行标准处理的潮湿试验将检查波放大，云尺度模拟将考虑原涡旋的增长。该项目的广泛影响源于对热带气旋发生的更好理解的社会效益以及这种理解对预测的潜在影响。蒙哥马利的团队将与美国国家海洋和大气局飓风研究部在他们的年度实地研究计划中进行合作。将对军队的研究生进行培训。

When, where, and how weakly rotating convective regions develop into full-blown tropical cyclones remains an essentially unsolved problem in atmospheric dynamics, albeit a problem with unusually significant implications for forecasting high-impact weather. In this project Montomgery and his group will explore his "marsupial hypothesis," which relates tropical cyclogenesis to the critical layers of tropical waves. The "marsupial hypothesis" comprises three sub-hypotheses:1) The weakly rotating regions of thunderstorms that develop into tropical cyclones form at the critical level, or steering level, of tropical traveling waves. At this level the wave speed equals that of the background wind, so that fluid, including the the weakly rotating "proto-vortex," moves with the wave.2) For stronger waves, the critical level evolves into a critical layer, which forms a pocket of closed streamlines. In this pocket, the developing vortex is partially isolated or protected (thus "marsupial" theory) from the entrainment of dry air and the deleterious affects of vertical shear.3) Tropical waves are amplified by the latent heat release associated with these proto-vortices.These hypotheses will be tested in a program of observational analyses and modeling. Preliminary analyses of atmospheric data indicates that critical layers of African easterly waves are, as hypothesized, preferred regions for tropical cyclone development, and that convection within the wave trough helps to maintain the wave. These analyses will be extended to monsoon trough cases, and cyclogenesis cases will be balanced with null cases, in which cyclogenesis does not occur. Problems with reanalyses in the tropics - that the results are strongly conditioned by the cumulus parameterization scheme - will be circumvented by analyzing data from other sources, including the Tropical Rainfall Measurement Mission (TRMM) satellite data, and in-situ data obtained during the summer-fall 2008 T-PARC (THe Observing System Research and Predictability Experiment (THORPEX) Pacific Asian Regional Campaign) field campaigns.Model experiments will be carried out using the Weather Research and Forecasting (WRF) model. Dry experiments will examine the vortex shedding from tropical waves that produces proto-vortices. Moist experiments with standard treatments of cumulus convection will examine wave-amplification, and cloud-scale modeling will consider the growth of proto-vortices.Broader impacts of this project derive from the societal benefits of improved understanding of tropical cyclogenesis and the potential impact of such understanding on prediction. Montgomery's group will collaborate with NOAA's Hurricane Research Division in their annual field program of research. Graduate students from the military services will be trained.