Waves and Instabilities of the Midlatitude Atmosphere: An Observational Analysis using Potential Vorticity

小行星9313785 在中纬度地区，一天和两天的天气预报在天气尺度或更大的尺度上是非常准确的，而长期预报则模拟大气的一般行为，如果不是细节的话。 尽管如此，天气尺度波和不稳定性的动力学还没有完全得到很好的理解。 此外，天气尺度的波和不稳定性还有待于作为行星尺度过程的参数化，尽管有证据表明，这些波在时间尺度上与行星波处于统计准平衡状态，时间尺度超过几周。 这项研究工作涉及两个相关的目标，旨在提高我们对斜压情况下所涉及的动力学过程的理解。 第一种是利用比准地转高阶的平衡近似，推导出Rossby波有效折射率的数学表达式。 第二个目标是发展和应用一种方法，根据观测结果计算这种有效折射率（位涡的函数）的气候分布，而不是一个简单的任务，因为真实的大气中的位涡分布极不均匀。 一旦确定了这些参数，PI就可以更好地了解波在大气中的传播特性。 他们的目的是将其结果应用于大气阻塞事件和低频变率的研究。 ***

9313785 Emanuel One and two day forecasts of weather in the midlatitudes at the synoptic-scale and greater are highly accurate, and longer- range forecasts simulate the general behavior, if not the details, of the atmosphere. Despite this, the dynamics of synoptic-scale waves and instabilities are not altogether well understood. Moreover, synoptic-scale waves and instabilities are yet to be parameterized as in terms of planetary-scale processes, even though there is evidence that these waves are in a state of statistical quasi-equilibrium with the planetary waves on time scales longer than a few weeks. This research effort involves two related objectives which are directed at improving our understanding of the dynamical processes involved in baroclinic situations. The first is to deduce a mathematical expression of an effective refractive index for Rossby waves using balance approximations of order higher than quasi- geostrophy. The second is to develop and apply a methodology for calculating climatological distributions of this effective refractive index (a function of potential vorticity) from observations, not a straight-forward task given the extremely inhomogeneous distributions potential vorticity in the real atmosphere. Once these are determined, the PIs can better understand the wave propagation characteristics in the atmosphere. Their intention is to apply their results to the study of atmospheric blocking events and low-frequency variability. ***