Atmospheric Frontal Dynamics

温带地区冬季的大部分恶劣天气都与冷锋有关。这些南部暖空气和北部冷空气之间的过渡区是天气预报的重点。大多数气象服务使用的模式通常对这些天气系统作出准确的预报，但是，当出现错误时，可能部分地与发生在比数值模式在空间和时间上的分辨率小的尺度上的运动有关。减轻数值预报模型误差的一种方法是开展研究项目，观察小尺度、高频运动，并利用这些信息以物理上真实的方式参数化它们的影响，从而引入亚网格尺度效应。拟议的调查利用了两个观测项目的观测结果，这两个项目部分得到了美国国家科学基金会的支持：风暴规模业务研究气象锋面实验系统测试（STORM-FEST, 1992）和微锋面，1995。利用声波风速计和热线风速计积累了从几十公里到毫米尺度的锋面观测资料。主要目的是记录地球边界层锋面附近湍流动能的耗散。来自microfront的数据服务于这一目的，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。在空间和时间上了解湍流耗散过程是必要的，以便为预报和研究模式提供更真实的边界层耗散参数化。第二个目标与经典理论模型的改进有关，该模型提供了额叶收缩过程的物理解释，即所谓的额叶生成。该模式忽略了在STORM-FEST期间发生的锋生事件中观测到的某些特征：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。这些解没有考虑到当锋面在边界层内时变得重要的耗散过程。正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，要么根本不处理这些效应，这是本研究的一个长期目标

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.***