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

9313785伊曼纽尔对中纬度天气的一天和两天天气预报在天气尺度和更大范围内是高度准确的，较长期的预报模拟了大气的一般行为，如果不是细节的话。尽管如此，天气尺度波的动力学和不稳定性并没有完全被很好地理解。此外，天气尺度的波动和不稳定性尚未像行星尺度的过程那样被参数化，尽管有证据表明，这些波动在时间尺度上与行星波处于统计准平衡状态，时间尺度长于几周。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的动力过程的理解。第一种方法是利用比准地转法高一阶的平衡近似，推导出Rossby波的有效折射率的数学表达式。第二是开发和应用一种从观测中计算这种有效折射率(位涡的函数)的气候学分布的方法，而不是一项直接的任务，因为实际大气中的位涡分布极其不均匀。一旦确定了这些参数，PI就可以更好地了解大气中的波传播特性。他们的目的是将他们的结果应用于大气阻塞事件和低频变化的研究。***

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. ***