Dynamics of Low Frequency Phenomena

低频现象的动力学

• 批准号: 9214840
• 负责人: Peter Webster
• 金额: $ 76万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-09-01 至 1996-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9214840&HistoricalAwards=false
• 关键词: Dynamics; Low; Frequency; Phenomena

The research into the dynamics of large-scale, low frequency phenomena of the coupled ocean-atmosphere system has an emphasis on planetary scale motions with time scales ranging from weeks to years. The four main areas of this research are: (I) The annual cycle of the low-latitude coupled ocean-atmosphere system: Mounting evidence indicates that the annual cycle plays an integral role in the longer period, interannual variability of the coupled ocean-atmosphere system. The annual cycle itself is a complicated combination of interactive, large amplitude asymmetric (monsoon) and symmetric (Walker) components. If these components are out-of-phase, as appears to be the case, then certain types of interaction may be expected. Therefore, the interactive structure of these components will be investigated with a combination of diagnostic and modeling techniques. (II) Equatorial Wave Propagation in Inhomogeneous Flows: Earlier studies indicate that equatorial transients are significantly modified by the latitudinal and longitudinal structure of the basic flow. Both the sign and latitudinal shear of the basic flow tend to determine the degree of equatorial trapping and lateral extension (emanation) of the transients while the longitudinal stretching deformation determines the degree to which transient modes are trapped longitudinally. This research will be expanded from the past studies by explicitly including the strong vertical shear found in the tropical atmosphere. This research will also take advantage of the more complete ECMWF 31-level global operational model now available. (III) Interhemispheric and Extratropical-tropical Interaction: Abundant evidence exists to show that extratropical modes influence the tropical regions or even extend to the other hemisphere through the equatorial westerly duct regions. Further theoretical studies in this area will use conservative potential vorticity on an isentropic surface (IPV) as a basic tool in an exhaustive diagnostic investigation of regional equatorial propagation. A pilot study appears to identify new phenomena and unexplained processes which may have considerable relevance in latitudinal interactions. (IV) Rapid Development of Ultra-long Equatorial Anomalies: Tropical Bursts and Surges: A common view of the tropics is that the large scale fields are weak and slowly varying and that only small scale convective disturbances have rapid development. However, a contrary view is suggested by new analyses which show that rapid development appears to occur on the largest scales, thousands of kilometers, especially in the warm pool regions of the tropical Indian and Pacific oceans. A combined diagnostic and modeling activity, aimed at understanding these tropical bursts and their role in the coupled ocean-atmosphere interactions, will be undertaken. Research in each of these four areas will proceed first with detailed diagnostic studies which will be used to pose hypotheses. Then the hypotheses will be tested by experimentation with a hierarchy of theoretical numerical models. This approach has proven to be very successful in past research. This research is important because it focuses on understanding the behavior of the coupled ocean-atmosphere system on time scales of weeks to years. This understanding is key to determining whether the coupled system is predictable on time scales of months to years, one of the specific scientific goals of the TOGA (Tropical Ocean Global Atmosphere) Program which is aimed at studying the prediction of climate phenomena.

大尺度低频动力学研究 海气耦合系统的现象，重点是 行星尺度的运动，时间尺度从几周到 年 这项研究的四个主要领域是： (I)低纬海气耦合的年循环 系统：越来越多的证据表明，年度周期起着重要的作用。 在较长时期内的整体作用，年际变化的 海气耦合系统 年周期本身是一个 复杂的互动组合，大幅度不对称 （季风）和对称（步行者）分量。 如果这些部件 是异相的，就像看起来的那样，那么某些类型的 可以期待互动。 因此，互动结构 这些组件将进行调查的组合， 诊断和建模技术。 (II)非均匀流中的赤道波传播：早期 研究表明，赤道瞬变是显著的， 由基本的纬度和经度结构修改 流 基流的符号和纬向切变都倾向于 以确定赤道捕获和横向的程度 瞬态的延伸（发散），而纵向 拉伸变形决定了瞬态 模式被纵向捕获。 这项研究将扩大 从过去的研究中明确包括强垂直 热带大气中的切变。 这项研究也将 利用更完整的ECMWF 31级全球 现在的运营模式。 (III)半球间和热带外-热带相互作用： 大量的证据表明， 影响热带地区，甚至延伸到其他地区， 西半球通过赤道西风导管区。 进一步 在这方面的理论研究将使用保守势 等熵面上的涡量（IPV）作为一种基本工具， 区域赤道详尽诊断调查 传播 一项试点研究似乎发现了新的现象， 无法解释的过程，可能有相当大的相关性， 纬度的相互作用 (IV)超长赤道异常的快速发展： 热带爆发和浪涌：对热带的一个普遍看法是， 大尺度场是微弱的，变化缓慢， 小尺度对流扰动发展迅速。 然而，新的分析表明， 快速发展似乎发生在最大的规模上， 数千公里，特别是在暖池地区， 热带印度洋和太平洋。 一种综合诊断和 建模活动，旨在了解这些热带爆发， 它们在耦合的海洋-大气相互作用中的作用将是 进行。 这四个领域的研究将首先进行， 详细的诊断研究，将用于提出假设。 然后，将通过实验对假设进行测试， 理论数值模型的层次结构。 这种方法有 在过去的研究中非常成功。 这项研究很重要，因为它侧重于了解 时间尺度上的海气耦合系统的行为 几周到几年 这种理解是确定是否 耦合系统可以在几个月的时间尺度上预测， 年，TOGA（热带）的具体科学目标之一 海洋全球大气）计划，该计划旨在研究 预测气候现象。