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

了解马登-朱利安振荡 (MJO) 的基本动力学和可预测性

• 批准号: 1540783
• 负责人: Bin Wang
• 金额: $ 50万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-12-15 至 2020-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1540783&HistoricalAwards=false
• 关键词: Understanding; Essential; Dynamics; Predictability; Madden

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.

该研究的总体目标是增进对控制马登-朱利安振荡（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。将通过多模型诊断分析和使用耦合气候模型的数值实验来研究 MJO 缓慢向东传播和启动/增强的根本原因。还将研究 MJO 遥相关反馈其自身向东传播的过程。将要检验的第一个假设侧重于决定 MJO 向东传播的机制。耦合的开尔文-罗斯比波结构以及 MJO 对流与低压异常之间的相位差表明，MJO 缓慢向东传播可能本质上是由与低频赤道波相关的动力过程的对流相互作用驱动的。因此，低频波与摩擦湿气辐合产生的大尺度对流复合体（包络线）的耦合可能成为MJO东移的基本驱动力。水分的局部变化、水分平流、平均态湿静态能量（即SST）分布、表面熵通量交换、动量、热量和水分的高档涡流传递、环境垂直切变和平流、温带涡流活动通量以及大气-海洋混合层相互作用都可以在不同程度上进一步改变传播速度。第二个假设涉及负责 MJO 强化和维持的机制。对流与波浪动力学的相互作用本身不会产生不稳定。然而，额外的摩擦湿气会聚与浅层和浓密云中释放的潜热相互作用，可以通过将平均态可用湿静态能量转换为MJO可用势能和动能，为MJO强化产生行星尺度的不稳定性。水分平流、地表蒸发-风反馈、MJO 与热量、水分和动量的高档涡流传输之间的相互作用、来自热带地区外部的能量传播对于 MJO 的启动和放大也可能很重要。