Dynamics of the midlatitude atmosphere

这项研究计划与气象学家直接合作，应用现代流体力学的数学方法来提高我们对支配中纬度(包括北美)大气天气的基本物理过程的知识。拟议的工作集中在我们在理论理解中存在重要空白的两个大气特征上：对流层涡旋(高、低压单体)的动力学，以及重力波的产生和稳定。A)众所周知，我们在北美经历的大尺度天气系统的起源是对流层顶上的小尺度涡度-一个约10公里高的过渡区，标志着大气天气产生层的顶部。这些小尺度扰动通过涡旋合并的湍流过程演变成大尺度天气结构。这项研究计划旨在开发计算模式，专门了解对流层顶上的涡旋的生命周期。B)重力波是一种大气运动，其速度比控制大陆天气模式的大气运动速度更快，而且通常尺度要小得多。作为一种局部现象，重力波的表现形式直接被认为是“晴空湍流”，或者是引发高山地区降水的垂直运动。作为一种全球现象，重力波可以作为能量级联到小尺度湍流的途径，这是大气中混合和消散的主要机制。研究人员最近的一项理论发现是，通过专门的计算机模型进一步研究了大尺度山波的不稳定性，以确定它们在大气湍流动力学中的作用。

In direct collaboration with meteorologists, this program of research applies modern mathematical methods of fluid mechanics to improve our knowledge of the basic physical processes that govern atmospheric weather in the midlatitudes (which includes North America).  The proposed work focusses on two features of the atmosphere for which there exist important gaps in our theoretical understanding: the dynamics of tropospheric vortices (high- and low-pressure cells), and the generation and stability of gravity waves. a)  It is well known to meteorologists that the large-scale weather systems we experience in North America have their origins as small-scale vorticity on the tropopause --- a transition zone about 10km high which marks the top of the weather producing layer of the atmosphere.  These small-scale disturbances evolve into large-scale weather structures via a turbulent process of vortex mergers.  This program of research seeks to develop computational models to specifically understand this lifecycle of vortices on the tropopause. b)  Gravity waves are motions of the atmosphere which are faster, and typically of much smaller scale than those governing the continental weather pattern.  As a local phenomenon, the manifestations of gravity waves are directly experienced as "clear air turbulence", or are responsible for vertical motions that trigger precipitation in alpine regions.  As a global phenomenon, these waves can serve as a pathway for energy to cascade to small-scale turbulence, which is the primary mechanism for mixing and dissipation in the atmosphere.  A recent theoretical discovery, by the researchers, of the instability of large-scale mountain waves are further investigated by specialized computer models to ascertain their role in the turbulent dynamics of the atmosphere.