Tropical Intraseasonal Variability in Models and Observations

了解热带季节内变化是气候动力学中的一个重要问题。这个项目的目标是加强对Madden-Julian振荡(MJO)基本动力学的理解。这一努力的更广泛影响非常高。与NCAR合作，PI将把新开发的面向过程的诊断纳入诊断包，该诊断包将应用于NCAR的社区地球系统模型(CESM)的不同版本，以评估--并最终改进--MJO的表示。此外，还有研究生和博士后培训以及诊断能力的发展，气候科学界可以利用这些能力来潜在地改进模式模拟。本项目将检验的主要假设是，需要风蒸发和辐射反馈来破坏MJO的稳定，同时还需要弱正的垂直总湿稳定。并假设水平平流对MJO向东传播是至关重要的。拟议工作将解决的具体问题包括：1)什么过程组合对MJO的失稳负责，包括垂直平流、地面通量和/或辐射反馈？2)平均流、异常流和高频扰动的水汽平流对MJO的东传有什么贡献？3)受列综合MSE预算启发的选定的基于过程的指标如何与模式MJO性能有关，这些关系告诉我们关于MJO动力学的什么？4)列综合MSE预算中失稳和传播因子的划分如何比较模式和观测之间的关系，这种划分中的差异与模型平均状态偏差有何关系？

Understanding tropical intraseasonal variability is an important problem in climate dynamics. The goal of this project is to enhance understanding of the basic dynamics of the Madden-Julian oscillation (MJO). The broader impacts of this effort are very high. In collaboration with NCAR, the PI will incorporate newly developed process-oriented diagnostics into a diagnostics package that will be applied to different versions of NCAR's Community Earth System Model (CESM) to evaluate--and eventually improve--the representation of the MJO. In addition, there will graduate student and postdoc training as well as the development of diagnostic capabilities that could be used by the climate science community to potentially improve model simulations.The leading hypothesis that will be examined in this project is that wind-evaporation and radiative feedbacks are required to destabilize the MJO, in conjunction with weakly positive vertical gross moist stability. It is also hypothesized that horizontal advection is critical to eastward MJO propagation. Specific questions that the proposed work will address include: 1) What combination of processes is responsible for destabilization of the MJO, including vertical advection, surface fluxes, and/or radiative feedbacks? 2) What are the contributions of moisture advection by the mean flow, anomalous flow, and higher frequency disturbances to eastward propagation of the MJO? 3) How do selected process-based metrics inspired by the column-integrated MSE budget relate to model MJO performance, and what do these relationships tell us about MJO dynamics? 4) How does the partitioning of destabilization and propagation factors in the column-integrated MSE budget compare between models and observations, and how do differences in this partitioning relate to model mean state bias?