Collaborative Research: Environmental Control of Tropical Cyclone Activity

该奖项是根据2009年《美国复苏和再投资法》(公法111-5)资助的。最近的研究表明，海洋流域综合的热带气旋活动的年际至年代际变化的很大一部分甚至大部分是由风暴形成的大尺度大气和海洋环境控制的。大西洋热带气旋活动的统计和基于模型的事后预测捕捉了热带气旋频率年际变化的65%，尽管很少或根本没有考虑到潜在的启动扰动，如非洲东风波。然而，这些同样的技术在应用于全球变暖情景时产生了截然不同的结果。这突出表明需要更好地了解热带气旋与气候之间的联系。该项目将使用几种不同但互补的方法寻求这样的理解。第一个是利用云尺度模式，研究在具有切变的辐射-对流平衡的大尺度环境中，热带气旋由种子气旋扰动形成或未能形成的情况。这种方法以前的结果将扩展到更广泛的风廓线，包括速度和方向切变，从而允许仔细研究现实环境中的气旋生成(或失败)，这些环境仍然可以进行系统调整和比较。第二种方法建立在创世潜力指数(GPI)成功的基础上，当应用于历史数据时，该指数已被证明解释了热带气旋活动的大部分年际变化和长期趋势。在这里，它将被用来理解在模拟全球变暖反应的气候模型中，导致GPI预测变化的物理因素。该指数将使用云解析模型模拟的结果进行改进。最后，将对云解析模式中的一到两个成因进行一些深入的分析，试图检验热带气旋只能在几乎饱和于对流层大部分的中尺度斑块中发展的假设。更广泛的影响是促进对热带气候和热带气旋活动之间关系的理解。这可能导致对热带气旋活动可能或不会随着气候变化而变化的更好和更有用的评估。这项工作还可能产生对热带气旋形成过程的更基本的理解，最终导致对热带低气压和风暴形成的更好的短期预测。该项目将支持对一名年轻科学家或博士后和一名研究生的培训，并将有助于在广泛使用的天气研究和预报(WRF)模型的基础上进一步开发灵活的理想化飓风建模系统。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Recent research has established that much and perhaps most of the interannual to interdecadal variation of tropical cyclone activity integrated over ocean basins is controlled by the large-scale atmospheric and oceanic environment in which the storms develop. Statistical and model-based hindcasts of Atlantic tropical cyclone activity capture as much as 65% of the interannual variance of tropical cyclone frequency, despite taking little or no account of potential initiating disturbances, such as African easterly waves. These same techniques, however, produce greatly divergent results when applied to global warming scenarios. This highlights the need for a better physical understanding of the link between tropical cyclones and climate. This project will seek such an understanding using several different, but complementary, approaches. The first is an investigation, using a cloud-scale model, of the formation, or failure to form, of tropical cyclones from seed cyclonic disturbances in large-scale environments of radiative-convective equilibrium with shear. Previous results with this method will be extended to a wider range of wind profiles that include speed and directional shear, allowing for a careful study of cyclogenesis (or failure) in realistic environments that still can be systematically adjusted and compared. A second approach builds on the success of the Genesis Potential Index (GPI), which, when applied to historical data, has been shown to explain much of the interannual variance and long-term trend in tropical cyclone activity. Here it will be used to understand the physical factors responsible for predicted variations in the GPI in climate models simulating the response to global warming. The index will be improved using results from the cloud-resolving model simulations. Finally, one or two cases of genesis in the cloud-resolving model will be analyzed in some depth, in an attempt to test the hypothesis that tropical cyclones can develop only in mesoscale patches that are nearly saturated through most of the troposphere.Broader impacts are in advancing understanding of the relationships between tropical climate and tropical cyclone activity. This could lead to better and more useful assessments of how tropical cyclone activity may or may not change with a changing climate. This work may also yield a more fundamental understanding of the process of tropical cyclone formation, ultimately leading to better short-term forecasts of the formation of tropical depressions and storms. The project will support the training of a young scientist or post-doc and a graduate student and will contribute to further development of a flexible idealized hurricane modeling system based on the widely-used Weather Research and Forecasting (WRF) model.