Understanding Essential Dynamics and Predictability of Madden-Julian Oscillation (MJO)

该研究的总体目标是促进对Madden-Julian振荡（MJO）传播和发展的基本机制的理解，并提高动力学模型模拟和预测季节内变化的能力。将通过多模式诊断分析和使用耦合气候模式的数值试验来研究MJO缓慢东传播和启动/加强的根本原因。还将研究MJO遥相关反馈到其自身东向传播的过程。第一个假设，将被测试的重点是机制确定MJO向东传播。耦合Kelvin-Rossby波结构和MJO对流和低压异常之间的相位差表明，MJO的缓慢向东传播可能主要是由与低频赤道波相关的动力学过程的对流相互作用驱动的。因此，低频波与摩擦水汽辐合形成的大尺度对流复合体（包层）的耦合可能是MJO东移的基本驱动力。水汽的局地变化、水汽平流、平均状态湿静力能（SST）分布、地面熵通量交换、动量、热量和水汽的高阶涡动输送、环境垂直切变和平流、大气外涡动活动通量以及大气-海洋混合层相互作用都能不同程度地改变传播速度。第二个假设涉及负责MJO的强化和维持的机制。仅对流与波动动力学的相互作用不会产生不稳定性。然而，额外的摩擦水汽辐合与释放的潜热在浅和congestus云相互作用，可以产生行星尺度的不稳定性MJO加强通过转换的平均状态可用湿静力能量MJO可用的潜力和动能。水汽平流、地面蒸发-风反馈、MJO与高尺度涡旋的热、湿、动量输送的相互作用以及来自热带外的能量传播对MJO的产生和放大也可能是重要的。

The overall goal of the research is to advance understanding of fundamental mechanisms governing the propagation and development of Madden-Julian Oscillation (MJO) and to improve the ability of dynamical models to simulate and predict intraseasonal variability. Fundamental causes for slow eastward propagation and initiation/intensification of the MJO will be investigated through multi-model diagnostic analysis, and numerical experiments using coupled climate models. Processes through which the MJO teleconnection may feedback to its own eastward propagation will also be examined. The first hypothesis that will be tested focuses on mechanisms determining eastward propagation of the MJO. The coupled Kelvin-Rossby wave structure and the phase difference between the MJO convection and the low pressure anomaly suggest that slow eastward propagation of MJO may be essentially driven by convective interaction with dynamical processes associated with low-frequency equatorial waves. Thus, the coupling low frequency waves and the large scale convective complex (envelope) by frictional moisture convergence may serve as a basic driver for the MJO moving eastward. The local change of moisture, moisture advection, mean state moist static energy (thus SST) distribution, surface entropy flux exchange, upscale eddy transport of momentum, heat and moisture, environmental vertical shear and advection, the extratropical eddy activity flux, and atmosphere-ocean mixed layer interaction can all further modify propagation speed to various degrees. The second hypothesis deals with mechanisms responsible for intensification and maintenance of the MJO. The convective interaction with wave dynamics alone does not generate instability. However, the additional frictional moisture convergence interacting with the latent heat released in shallow and congestus clouds can generate planetary scale instability for MJO intensification through conversion of mean state available moist static energy to MJO available potential and kinetic energy. The moisture advection, the surface evaporation-wind feedback, the interaction between MJO and upscale eddy transport of heat, moisture and momentum, the energy propagation from outside of the tropics may also important for initiation and amplification of the MJO.