Large-Scale Influences on Tropical Cyclogenesis

本项目的目标是研究热带气旋的形成，特别是不同环境气流在其中所起的作用。 第一个是利用PI积极参与的东太平洋气候过程调查（EPIC）实验的资料和NOAA的输出长波辐射（OLR）资料来研究东太平洋的热带气旋生成。 重点是热带气旋形成前热带辐合带（ITCZ）和东风波之间的关系。 对于第二种途径，PI将试图调和两种范式的热带气旋在西太平洋和墨西哥湾，即旋转的涡在季风槽与东风波相互作用的马登朱利安振荡（MJO）的前光标气旋。 工作假设是热带气旋生成通常发生在以下情况下：1）活跃的MJO产生强烈的季风槽，其南部有西风带; 2）上游波到达活跃的MJO，振幅增加，最终成为低气压形成的地点。 这样，MJO、季风槽和上游波都参与并相互作用于气旋的形成。 第三个途径是利用浅水模式和正压模式进行数值模拟，以检验工作假设，使用理想化的背景状态和从观测资料中提取的MJO信号。热带气旋生成仍然是天气预报中最具挑战性的任务之一。 从预测和建模的角度来看，增加对环境流如何影响成因的理解是很重要的。 计划中的研究有可能在这一领域带来一些光明，研究将为研究生学习提供良好的机会。

The objective of this project is to study tropical cyclongenesis and, in particular, what roles different environmental flows play in it. Three research avenues will be pursued. The first one is to examine tropical cyclogenesis in the eastern Pacific using data from the East Pacific Investigation of Climate Processes (EPIC) experiment in which the PI actively participated and the Outgoing Long-wave Radiation (OLR) data from NOAA. The focus will be the relationship between the intertropical convergence zone (ITCZ) and easterly waves before tropical cyclones form. For the second avenue, the PI will attempt to reconcile two paradigms of tropical cyclogenesis in the western Pacific and Gulf of Mexico, namely, the spin-up of vortices in the monsoon trough versus easterly waves interacting with the Madden Julian Oscillation (MJO) as pre-cursors to cyclogenesis. The working hypothesis is that tropical cyclogenesis often occurs under the following circumstances: 1) an active MJO producing a strong monsoon trough with westerlies to its south and 2) upstream waves reach the active MJO, grow in amplitude, and are ultimately the locus of depression formation. In this way, the MJO, monsoon trough, and upstream waves all participate and interact in cyclone formation. The third avenue is to conduct numerical simulations using shallow water and barotropic models to test the working hypothesis, using both idealized background states and those extracted from observational data with MJO signals.Tropical cyclogenesis remains one of the most challenging tasks in weather prediction. Increasing the understanding of how environmental flows affect genesis is important both from the prediction and modeling perspectives. The planned research has the potential of shedding some light in this area and the research will provide good opportunities for graduate studies.