球面二维傅里叶级数在热带外平-对流层行星波时空变率研究中的应用

The extratropical atmospheric circulation in both troposphere and stratosphere is closely linked with planetary waves, and their space-time variability has important implications for changes in the weather and climate over the extratropical regions. Both theoretical and observational studies suggest that it is necessary to depict the horizontal structures of planetary waves from the angle of two-dimensional waves on a sphere. However, the existing one-dimensional wave decomposition along latitude circles has little consideration for the meridional structure of planetary waves, and thus is unable to reveal the laws of planetary wave evolutions on a sphere comprehensively. By using the two-dimensional wave decomposition method on a sphere, performing diagnostic analyses on the long-term observations, and combining with the theoretical analysis and numerical simulations, we expect to explore the dominant meridional structures of stratospheric and tropospheric planetary waves over the extratropical regions and their variations, to investigate the influence of basic flow on the meridional structures of stratospheric and tropospheric planetary waves, to analyze the propagation features of planetary waves with different meridional structures, and finally to evaluate the roles of planetary waves with different meridional structures in the stratosphere-troposphere coupling processes. The implement of relevant work could not only improve the understanding of the laws of stratospheric and tropospheric planetary wave evolutions, also would provide some scientific references for further recognition of the climatic effects of stratospheric and tropospheric planetary waves, thus it would be helpful in both the scientific endeavor and practical significance.

热带外地区平-对流层大气环流演变的重要表现形式是行星波的活动，它的时空变率对热带外天气、气候变化有重要影响。理论和资料诊断研究都表明有必要从球面二维波动的角度描述行星波的水平结构，而现有的沿纬圈的一维波分解方法对行星波的经向结构考虑不足，因此不能全面地反映热带外地区行星波在球面上的演变规律。本项目将基于球面二维波分解方法(球面二维傅里叶级数)，通过对长期的观测资料进行诊断，并结合理论分析和数值模拟，围绕行星波的经向结构，分析热带外地区平流层和对流层行星波主导的经向结构及其时变特征，理论探讨平-对流层基本气流对行星波经向尺度的影响，考察不同经向结构的行星波在平-对流层的传播特征，揭示行星波的经向结构在行星波上传过程中的作用。相关工作的开展，将有利于增强我们对平-对流层行星波演变规律的认识，并且将为理解平-对流层行星波的气候效应提供科学参考，具有重要的科学和现实意义。

热带外地区平-对流层大气环流演变的重要表现形式是行星波的活动，它的时空变率对热带外天气、气候变化有重要影响。理论和资料诊断研究都表明有必要从球面二维波动的角度描述行星波的水平结构，而现有的沿纬圈的一维波分解方法对行星波的经向结构考虑不足，因此不能全面地反映热带外地区行星波在球面上的演变规律。热带外地区行星波活动与大尺度遥相关型（如北大西洋涛动NAO）存在紧密联系，有必要从波动力学的角度研究热带外遥相关型变化的动力学机理及其气候影响。本项目利用发展的球面二维谱分析方法，阐明热带外大气平-对流层的时空变率，揭示平对流层行星波传播的特征及差异，并提出合理的动力学解释，研究了中高纬行星波活动与大尺度气候变率的关联，揭示了大尺度遥相关型变化的动力学机理及其对区域气候的影响。项目研究取得的成果对认识大气环流系统变化和理解热带外大气-海洋相互作用机制提供重要的理论依据和物理参考，对提高热带外气候预测水平具有重要的指导意义。