Lateral Influences on Madden-Julian Oscillation (MJO) Initiations

马登朱利安振荡（MJO）是热带大气逐月变化的主要模态。 它的影响延伸到温带天气和热带气旋的形成。尽管它的重要性，MJO的许多方面还没有得到很好的理解，它在大多数全球模型中的模拟很差。这项研究的动机是张的两个初步发现：首先，他指出，虽然在自然界中，风的MJO变化与雷暴活动密切相关，但风和雷暴在模型中的MJO中往往表现得不连贯。 其次，他发现热带模式中MJO事件的开始与观测结果相匹配，并且事件的时间由模式的横向边界而不是内部热带的初始条件决定。 这些结果提出了几个问题，是要解决在这个项目中：什么功能的横向边界条件启动MJO事件，这种启动的机制是什么，横向边界启动如何与其他机制的MJO启动，以及如何重要，总体而言，是横向边界启动的MJO？将使用在先前NSF支持下开发的通道配置中的热带中尺度大气模型。 模型实验将隔离这些功能的边界条件是必不可少的启动MJO。 将模拟许多MJO事件，有和没有随时间变化的横向边界条件，以确定MJO事件从边界开始的频率。 其他实验将确定MJO引发对边界条件的敏感性，并探索加热和边界条件之间的相互作用。 最后一组实验将测试这样的边界条件是否真的是一个必要和充分条件MJO initiation.Brother影响这个项目的重要性MJO的季节内预测。 将培训一名研究生和一名博士后研究员。

The Madden Julian oscillation (MJO) is the leading mode of month-to-month variability in the tropical atmosphere. Its influences extend to extratropical weather and the initiation of tropical cyclones. Despite its importance, many aspects of the MJO are not well understood, and it is poorly simulated in most global models. The research is motivated by Zhang's two preliminary findings: first, he noted that, while in nature the MJO variability of the wind is closely tied to that in thunderstorm activity, winds and thunderstorms often behave incoherently in MJOs in models. Secondly, he found that the initiation of MJO events in a tropical model matched observations and that the timing of the events was determined by the lateral boundaries of the model rather than initial conditions in the interior tropics. These results raise several questions that are to be addressed in this project: what features in the lateral boundary conditions initiate MJO events, what are the mechanisms for this initiation, how does lateral boundary initiation interact with other mechanisms of MJO initiation, and how important, overall, is lateral boundary initiation of the MJO?A tropical mesoscale atmospheric model in a channel configuration, developed under prior NSF support, will be used. Model experiments will isolate those features in the boundary conditions that are essential for the initiation of MJO. Many MJO events will be simulated, with and without time-dependent lateral boundary conditions, in order to determine how often MJO events are initiated from the boundaries. Additional experiments will determine the sensitivity of MJO initiation to the boundary conditions and to explore interactions between heating and boundary conditions. A final set of experiments will test whether such a boundary condition is truly a necessary and sufficient condition for MJO initiation.Broader impacts of this project are in the importance of the MJO for intraseasonal prediction. A graduate student and a post-doctoral investigator will be trained.