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。这种明显的向下影响是一个活跃的研究领域。在这项探索性研究小额资助（SGER）下，蔡将在一个非常规的框架下研究对流层-平流层耦合的动力学，利用位势温度作为垂直坐标分析质量环流。纬向平均角动量平衡项将根据日常分析计算。这些结果将用于探索平流层中角动量异常向极地和向下传播的机制，以及蔡先生最近发表的研究成果所揭示的角动量异常在地球表面附近向赤道传播的机制。这一结果将为蔡的有争议的假设提供初步的检验，即这些特征的传播是由全球质量环流的平流造成的，最终是由加热驱动的。由于角动量异常从热带到高纬度在平流层传播大约需要50天，而相反的符号异常从高纬度到亚热带在对流层传播大约需要相同的时间，因此这项工作的更广泛影响在于其对延长时间尺度上的可预测性的潜在含义。一名研究生和一名博士后将参与研究。

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.