Large-Scale Influences on Tropical Cyclogenesis

该项目的目的是研究热带气旋的形成，特别是不同的环境流在其中所起的作用。将采取三个研究途径。第一个是利用PI积极参与的东太平洋气候过程调查（EPIC）实验数据和NOAA的输出长波辐射（OLR）数据来研究东太平洋的热带气旋形成。重点是热带气旋形成前的热带辐合带与东风波之间的关系。对于第二种途径，PI将尝试调和西太平洋和墨西哥湾热带气旋形成的两种范式，即季风槽中旋涡的自旋上升与与马登朱利安涛动（MJO）相互作用的东风波作为气旋形成的前兆。工作假设是，热带气旋形成通常发生在以下情况下：1)一个活跃的MJO产生一个强大的季风槽，其南面有西风带；2)上游波到达活跃的MJO，振幅增加，最终成为低压形成的场所。这样，MJO、季风槽和上游波共同参与气旋的形成并相互作用。第三种方法是使用浅水和正压模式进行数值模拟，使用理想背景状态和从MJO信号观测数据中提取的状态来验证工作假设。热带气旋形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，增加对环境流动如何影响成因的理解是很重要的。计划中的研究有可能对这一领域有所启示，并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.