Atmospheric Frontal Dynamics

在温带地区，大多数冬季的恶劣天气都与冷锋有关。这些南来的暖空气和北来的冷空气之间的过渡带是天气预报的重点。大多数气象服务机构使用的模型往往能对这些天气系统做出准确的预报，但当出现错误时，可能部分与尺度上的运动有关，这些运动在空间和时间上的分辨率低于数值模型。减少数值预报模式误差的一种方法是开展研究方案，观察小尺度、高频运动，并利用这一信息，以物理上真实的方式将亚网格尺度效应参数化，从而引入亚网格尺度效应。 拟议的调查使用的观测数据已得到支持，部分由国家科学基金会的两个观测计划：风暴尺度业务研究气象学前沿实验系统测试（STORM-FEST，1992年）和MICROFRONTS，1995年。从几十公里到毫米尺度的锋面观测是通过声波风速计和热线风速计积累的。一个主要目标是记录在地球边界层的正面附近的湍流动能耗散。来自MICROFRONTS的数据用于此目的，这些数据将用于验证与耗散过程相关的各种理论的准确性。 湍流耗散过程的知识，在空间和时间，是必要的，以提供更现实的参数化边界层耗散用于预测和研究模式。 第二个目标是与一个经典的理论模型，提供了一个物理解释的锋面收缩过程，所谓的锋生的改进。该模型忽略了在风暴节期间发生的锋生事件中观察到的某些特征：周期约为17小时的惯性振荡。这些振荡对锋生和伴随运动的影响将包括在理论发展中。该解决方案不考虑耗散过程，成为重要时，前线是在边界层内。如前一项研究所确定的那样，将耗散过程混合到理论模型中，这些模型要么粗略地处理这些效应，要么根本不处理，这是本研究的长期目标。

Most winter time severe weather in temperate latitudes is associated with cold fronts. These transition zones between warm air to the south and cold air to the north represent the focus of weather forecasts. The models used by most weather services often produce accurate forecasts of these weather systems, but errors, when they occur, may in part be associated with motions that occur on scales that are less than the resolution, in space and time, of the numerical models. One way to alleviate errors in numerical forecasting models is to carry out research programs to observe small-scale, high-frequency motions and to use this information to introduce sub-grid scale effects by parameterizing their effects in a physically realistic manner. The proposed investigation makes use of observations obtained from two observational programs that have been supported, in part, by the National Science Foundation: the Stormscale Operational Research Meteorology-Fronts Experiment Systems Test (STORM-FEST, 1992) and MICROFRONTS, 1995. Observations on the scale of fronts from tens of kilometers down to millimeter scale were accumulated by means of both sonic and hot-wire anemometers. A principal objective is to document the dissipation of turbulent kinetic energy near frontal surfaces in the Earth's boundary layer. The data from MICROFRONTS serves this purpose, and these data will be used to verify the accuracy of various theories associated with dissipative processes. Knowledge of turbulent dissipative processes, in both space and time, is necessary to provide more realistic parameterizations of boundary layer dissipation for use in forecast and research models. A second objective is associated with the improvement of a classical theoretical model that provides a physical explanation of the frontal contraction process, so-called frontogenesis. This model neglects certain features that have been observed in a frontogenesis event that occurred during STORM-FEST: inertial oscillations with periods of about 17 hours. The effect of these oscillations on frontogenesis and the accompanying motions will be included in a theoretical development. The solutions do not take account of dissipative processes that become important when the front is within the boundary layer. The blending of dissipative processes, as determined by the former investigation, into theoretical models that either handle such effects crudely or not at all, is a long-range goal of this research.***