浓积云型与层状云型两种对流影响热带大气季节内振荡的机理研究

The tropical atmospheric intraseasonal oscillation, the Madden-Julian Oscillation (MJO), is the dominant mode of the atmospheric intraseasonal variability. Despite its importance in intraseasonal prediction, the understanding of the physical mechanisms for the eastward propagation and the maintenance of the MJO is still limited. In particular, most of the previous MJO theories only consider the atmospheric deep convection and the associated first baroclinic mode of the tropical atmospheric motion, while neglecting the congestus convection and stratiform convection and the associated second baroclinic mode of the tropical atmospheric motion. However, the observational studies and numerical studies indicate that the congestus convection and stratiform convection can significantly affect the MJO. In this research, we will theoretically study how the congestus convection and stratiform convection affect the MJO, with focus on the physical mechanisms by which they affect the eastward propagation and the maintenance of the MJO. The results of this research will not only advance our knowledge in the essential physical mechanisms for the eastward propagation and the maintenance of the MJO, but also can provide theoretical guidance on improving the numerical model’s ability in simulating the MJO, so as to improve the MJO prediction. Therefore, this research is significant.

热带大气季节内振荡Madden-Julian oscillation（简称MJO）是大气季节内变率的主要模态。尽管其对季节内尺度预报非常重要，但是对导致MJO向东传播及维持的物理机制的理解仍存在重要缺陷。特别地，以往的MJO理论大多只考虑大气中的深对流及对应的热带大气运动第一斜压模态，而忽略了浓积云型对流（congestus convection）和层状云型对流（stratiform convection）及它们对应的大气运动第二斜压模态。然而观测研究和数值模拟表明，浓积云型对流和层状云型对流可以显著地影响MJO。本研究将从理论上研究浓积云型对流和层状云型对流对MJO的作用，着重研究它们影响MJO传播和维持的物理机制。本研究的结果不仅可以进一步提高对MJO传播和维持的物理机制的理解，而且可以为改善数值模式对MJO的模拟提供理论指导，从而有助于提高MJO的预测，因此具有重要意义。

本项目从大尺度对流-环流相互作用角度，系统研究了浓积云型对流(congestus convection，简称CC)和层状云型对流(stratiform convection，简称SC)对大气热带季节内振荡Madden-Julian oscillation(简称MJO)的作用，并阐明了其作用机理。.本研究的主要研究成果包括：1、建立了包含第一和第二斜压模态的理论模型，该模型不仅能够刻画深对流对MJO的作用，也能够刻画CC和SC的作用；2、揭示了CC和SC影响MJO传播的物理机制，表明强的CC和SC能增强热力场的东-西不对称性，从加速MJO的向东传播；3、揭示了CC和SC对MJO发展和维持的作用，证明了强的CC和SC能够通过增强低层水汽异常和相应的深对流异常而增加MJO的不稳定性，且温度反馈和边界层辐合反馈（对应CC）的相互作用对MJO的维持有重要影响；4、系统研究了MJO的传播多样性的特征、形成机理、对热带外地区的影响，表明CC和SC的强度差异能够通过影响MJO的热力结构造成MJO向东传播的多样性，但是MJO在北半球夏季的向北传播多样性与CC和SC无关。.本研究的结果不仅进一步提高了对MJO传播和维持机制的理解，为改进数值模式对MJO的模拟提供了理论指导，同时也揭示了影响MJO传播和遥相关的前兆因子，为提高季节内尺度预测提供了理论和观测依据。.