SGER: Stratosphere-Troposphere Transfer of the Zonal Angular Momentum Associated with the Global Mass Circulation

最近的观测研究表明，冬季平流层环流的变化之后是对流层的变化。这种明显的下行影响是一个活跃的研究领域。在这项探索研究小资助金(SGER)下，CAI将在非常规框架下研究对流层-平流层耦合的动力学，以位温为垂直坐标分析物质环流。纬向平均角动量平衡中的项将根据每日分析计算。这些结果将被用来探索平流层角动量异常向极和向下传播的机制，以及蔡最近发表的工作所揭示的，它们在地球表面附近向赤道传播的机制。这些结果将为蔡有争议的假设提供初步检验，该假说认为这些特征的传播是由最终由加热驱动的全球质量环流的平流造成的。这项工作的更广泛影响在于它对扩展时间尺度上的可预测性的潜在影响，因为角动量异常大约需要50天在平流层中从热带传播到高纬度，然后相反的符号异常需要大约相同的时间在对流层从高纬度传播到亚热带。一名研究生和一名博士后将参与这项研究。

Recent observational studies reveal that changes in the wintertime stratospheric circulation are followed by changes in the troposphere. This apparent downward influence is an active area of research. Under this Small Grant for Exploratory Research (SGER), Cai will investigate the dynamics of troposphere-stratosphere coupling in an unconventional framework, analyzing the mass circulation using the potential temperature as the vertical coordinate. Terms in the zonal mean angular-momentum balance will be calculated from daily analyses. The results will be used to explore the mechanisms responsible for the poleward and downward propagation of angular momentum anomalies in the stratosphere and, as revealed in Cai's recent published work, their equatorward propagation near Earth's surface. The results will provide a preliminary test of Cai's controversial hypothesis that the propagation of these features results from their advection by a global mass circulation that is ultimately driven by heating. Broader impacts of this work are in its potential implication for predictability on extended timescales, since the angular momentum anomalies take about 50 days to propagate in the stratospheres from the tropics to high latitudes, and then opposite signed anomalies take about the same amount of time to propagate in the troposphere from high latitudes to the subtropics. A graduate student and a post-doc will participate in the research.