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The vertical structure of tangential winds in tropical cyclones: Observations, theory, and numerical simulations.

机译：热带气旋切向风的垂直结构：观测，理论和数值模拟。

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摘要

The vertical structure of the tangential wind field in tropical cyclones is investigated through observations, theory, and numerical simulations. First, a dataset of Doppler radar wind swaths obtained from NOAA/AOML/HRD is used to create azimuthal mean tangential wind fields for 7 storms on 17 different days. Three conventional wisdoms of vertical structure are reexamined: the outward slope of the Radius of Maximum Winds (RMW) decreases with increasing intensity, the slope increases with the size of the RMW, and the RMW is a surface of constant absolute angular momentum (M). The slopes of the RMW and of M surfaces are objectively determined. The slopes are found to increase linearly with the size of the low-level RMW, and to be independent of the intensity of the storm. While the RMW is approximately an M surface, M systematically decreases with height along the RMW.The steady-state analytical theory of Emanuel (1986) is shown to make specific predictions regarding the vertical structure of tropical cyclones. It is found that in this model, the slope of the RMW is a linear function of its size and is independent of intensity, and that the RMW is almost exactly an M surface. A simple time-dependent model which is governed by the same assumptions as the analytical theory yields the same results.Idealized hurricane simulations are conducted using the Weather Research and Forecasting (WRF) model. The assumptions of Emanuel's theory, slantwise moist neutrality and thermal wind balance, are both found to be violated. Nevertheless, the vertical structure of the wind field itself is generally well predicted by the theory. The percentage rate at which the winds decay with height is found to be nearly independent of both size and intensity, in agreement with observations and theory. Deviations from this decay profile are shown to be due to gradient wind imbalance. The slope of the RMW increases linearly with its size, but is systematically too large compared to observations. Also in contrast to observations, M generally increases with height along the RMW.
机译：通过观测，理论和数值模拟研究了热带气旋切向风场的垂直结构。首先，从NOAA / AOML ​​/ HRD获得的多普勒雷达风幅数据集用于为17个不同日期的7次风暴创建方位角平均切向风场。重新审视了垂直结构的三种常规知识：最大风半径（RMW）的向外坡度随强度增加而减小，坡度随RMW的大小而增加，并且RMW是恒定的绝对角动量（M）的表面。客观确定RMW和M曲面的斜率。发现坡度随低级RMW的大小线性增加，并且与风暴强度无关。当RMW近似为M面时，M沿RMW随高度而系统地减小。Emanuel（1986）的稳态分析理论表明，对热带气旋的垂直结构做出了特定的预测。发现在该模型中，RMW的斜率是其大小的线性函数，并且与强度无关，并且RMW几乎恰好是M曲面。一个简单的与时间相关的模型，该模型由与分析理论相同的假设所控制，得出相同的结果。使用“天气研究与预报”（WRF）模型进行了理想的飓风模拟。伊曼纽尔理论的假设，即偏向湿性中性和热风平衡均被违反。尽管如此，理论上通常可以很好地预测风场本身的垂直结构。根据观察和理论，发现随高度衰减的风的百分率几乎与大小和强度无关。该衰减曲线的偏差表明是由于梯度风的不平衡引起的。 RMW的斜率随其大小线性增加，但与观测值相比，系统地太大。同样与观察相反，M通常沿RMW随高度增加。

著录项

  • 作者

    Stern, Daniel P.;

  • 作者单位

    University of Miami.;

  • 授予单位 University of Miami.;
  • 学科 Atmospheric Sciences.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 432 p.
  • 总页数 432
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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