Analysis of Coupling between Oceanic Kelvin Waves and Atmospheric Convection, and Its Impacts on Weather over the Tropical Pacific

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。马登-朱利安涛动(MJO)的西风阶段经常在赤道西太平洋引发海洋开尔文波。这些波动偶尔与向东移动的暖海表温度(SST)异常有关。异常温暖的海洋使大气不稳定为对流耦合波，与之相关的增强的深层对流加速了开尔文波峰以西的西风；这反过来又放大了开尔文波。这种模式表明，海洋开尔文波和大气对流是耦合的。初步结果表明，这种耦合组织了热带太平洋上的高影响天气事件，包括西风暴发和热带气旋。虽然这样的天气事件可以在海洋开尔文波发展之前发生在MJO内，但这些波会影响天气的进一步发展。这种与海洋的耦合不包括在MJO的传统观点中。在这个项目中，将研究与这些对流耦合海洋波相关的大气结构的演变，以及它们与高影响天气的联系。这类耦合事件的观测将被分析以诊断它们在大气中的三维空间结构的细节及其随时间的演变。将特别注意开尔文波附近天气事件的演变，以确定这些事件如何参与耦合过程。方法是准备和分析许多事件的组合，分析个别案例，并对所有事件的人口进行普查。研究结果将有助于建立耦合事件的天气动力学模式及其与相关天气的联系。这项研究将加深我们对海洋开尔文波与MJO、一些西风暴发和热带气旋相互作用的理解。该项目的更广泛影响包括预测耦合事件的发展及其相关的极端天气的可能性。这项工作将导致进一步分析季节内耦合和厄尔尼诺演变之间的潜在联系。该项目将支持一名初级调查员的工作和一名研究生的培训。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The westerly wind phase of the Madden-Julian Oscillation (MJO) often triggers oceanic Kelvin waves in the equatorial West Pacific Ocean. Occasionally these waves are associated with eastward moving warm sea surface temperature (SST) anomalies. The anomalously warm ocean destabilizes the atmosphere to convectively coupled waves, and the associated enhanced deep convection accelerates westerly winds to the west of the Kelvin wave crests; this, in turn, amplifies the Kelvin waves. This pattern suggests that oceanic Kelvin waves and atmospheric convection are coupled. Preliminary results indicate that this coupling organizes high impact weather events across the tropical Pacific, including westerly wind bursts and tropical cyclones. While such weather events can occur within the MJO prior to the development of oceanic Kelvin waves, the waves influence the further development of weather. Such coupling to the ocean is not included in traditional views of the MJO. In this project the evolutions of atmospheric structures associated with these convectively coupled oceanic waves will be investigated, as well as their associations with high-impact weather.Observations of such coupled events will be analyzed to diagnose the details of their three dimensional spatial structures in the atmosphere and their evolution over time. Particular attention will be paid to the evolution of weather events in the vicinity of the Kelvin waves, in order to determine how these events participate in the coupling process. The approach is to prepare and analyze composites of many events, to analyze individual cases, and to make a census of the population of all events. Results will contribute to a synoptic-dynamic model for the coupled events and their links with the associated weather.This study will enhance our understanding of the interactions of oceanic Kelvin waves with the MJO, some westerly wind bursts, and tropical cyclones. Broader impacts of this project include the potential to predict the development of coupled events along with their associated extreme weather. This work should lead to further analyses of the potential connections between the intraseasonal coupling and the evolution of El Nino. The project will support the work of a beginning investigator and the training of a graduate student.