Balanced Dynamics and Cyclone-Anticyclone Asymmetry

该项目将研究与气旋-反气旋不对称相关的动力学，即，为什么与较弱和范围较广的反气旋相比，气旋往往具有较大的振幅和孤立的核心。该研究将基于一个理想化的理论框架，该框架在rosby数展开中比拟等转（QG）模型高一个阶，即QG+1系统。PI将扩展他先前对以对流层顶为边界的QG+1系统的研究，在此基础上增加一个刚性表面作为另一个边界，使系统中有两个边界（因此命名为2sQG+1系统）。PI将测试假设2sQG+1系统的控制参数是两个边界之间的距离，因为它将调节斜压和正压动力学的相对重要性。第二个有待验证的假设是，2sQG+1系统将显示气旋具有较弱的向大尺度的能量转移，因此将保持局限于边界的坚固结构，而反气旋具有较强的高级能量转移，将跨越对流层。这些假设有助于解释自然界中气旋与反气旋的不对称性。然后，理想化的理论建模工作将用国家环境预测中心（NCEP）使用极低统计数据的分析数据进行测试。这些结果有可能提高我们对斜压和正压动力学之间尺度相互作用的理解，以及气旋-反气旋不对称的性质。计划中的研究将为研究生学习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.