Balanced Dynamics and Cyclone-Anticyclone Asymmetry

本项目将调查与气旋-反气旋不对称有关的动力学，即为什么气旋与较弱和较宽的反气旋相比，往往具有更大的幅度和孤立的核心。这项研究将基于一个理想化的理论框架，该理论框架是Rossby数展开中超越准地转(QG)模型的一个阶数，即QG+1系统。PI将扩展他之前关于以对流层顶为边界的QG+1系统的研究，以包括另外一个刚性表面作为系统中具有两个边界的另一边界(因此被称为2sQG+1系统)。PI将检验2sQG+1系统的控制参数是两个边界之间的距离的假设，因为它将调节斜压和正压动力的相对重要性。需要检验的第二个假设是，2sQG+1系统将显示气旋在较大尺度上的能量转移较弱，因此将在边界范围内保持坚固的结构，而具有较强高层能量转移的反气旋将横跨对流层。这些假设解释了气旋-反气旋本质上的不对称性。理想化的理论模拟工作将用国家环境预测中心(NCEP)的分析数据和极地低压的统计数据进行测试。这些结果可能有助于我们更好地理解斜压和正压动力之间的尺度相互作用，以及气旋-反气旋不对称的本质。计划中的研究将为研究生提供良好的教育机会。

This project will investigate the dynamics associated with the cyclone-anticyclone asymmetry, namely, why cyclones tend to have larger amplitude and isolated cores in comparison to weaker and broader anticyclones. The research will be based on an idealized theoretical framework that is valid an order beyond the quasigeostrophic (QG) model in the Rossby number expansion, i.e., the QG+1 system. The PI will extend his prior study on the QG+1 system that has the tropopause as a boundary to include, in addition, a rigid-surface as another boundary to have two boundaries in the system (thus named a 2sQG+1 system). The PI will test the hypothesis that the control parameter of the 2sQG+1 system is the distance between the two boundaries in that it would regulate the relative importance of baroclinic and barotropic dynamics. The second hypothesis to be tested is that the 2sQG+1 system will show that cyclones have a weaker energy transfer to larger scales and thus will maintain robust structures confined to the boundaries, whereas anticyclones, which have a strong upscale energy transfer, will span the troposphere. These hypotheses serve to provide explanations of the cyclone-anticyclone asymmetry in nature. The idealized theoretical modeling work will then be tested with the National Center for Environmental Prediction (NCEP) analysis data using the statistics of polar lows. The results have the potential of improving our understanding of scale interactions between baroclinic and barotropic dynamics, and nature of cyclone-anticyclone asymmetry. The planned research will provide good educational opportunities for graduate studies.