The Structure and Evolution of Midlatitude Cyclones

由挪威气象学家学派在20世纪第二个十年首创的描述性气旋模式长期以来一直是中纬度天气预报的基石。在这一范例中，极地空气和热带空气(极地锋面)之间环绕文字的边界地带是行动的焦点，该锋面上的波形成、演变和消亡；在它们的一生中产生典型的天气模式和变化。后来延伸到对流层的观测网络的发展，急流和行星尺度波的动力学理论，以及数值天气预报模式的出现，都使锋面气旋模式变得复杂和黯然失色。这在一定程度上是因为，在每一种情况下，处理都是在水平方向上过于粗略地网状分布，无法捕捉到狭窄的锋区。最近，雷达和卫星图像对与气旋有关的中尺度特征的描述，以及具有中尺度分辨率的数值研究模式的发展，为更详细地描述中纬度锋面气旋提供了可能性。MASS建议使用广泛使用的中尺度模式(MM4模式)，结合常规的粗粒度业务数据集，对一组五到六个这样的气旋(爆炸性发展和正常发展的海洋气旋、平坦地形上的大陆气旋、穿过落基山脉背风并向其移动的气旋)生成详细的定量四维描述。对这些数据集的分析将包括空气轨迹计算和复杂的三维图形。MASS预计，这些分析将有助于建立一种新的范式，以修正有用但不完整的挪威模式。这将有助于改进短期、当地天气预报，并有助于发展中尺度数值模式的业务版本。

The descriptive cyclone model originated by the Norwegian school of meteorologists in the second decade of the 20th century has long served as a cornerstone of weather forecasting in the middle latitudes. In this paradigm, a word-girdling boundary zone between polar and tropical air (the polar front) is the focal line of action, with waves on this front forming, evolving and dying; producing typical weather patterns and changes during their lifetime. The later development of observational networks extending through the troposphere, dynamical theorys of jet streams and planetary scale waves, and the advent of Numerical Weather Predic- tion models have both complicated and overshadowed the frontal cyclone model. This is due, in part, to the fact that in each case, the treatment is too coarse-meshed in the horizontal to capture the narrow frontal zone. More recently, radar and satellite-image depiction of mesoscale features associated with cyclones, and the development of numerical research models with mesoscale resolution, offers the possibility of describing mid-latitude frontal cyclones in much finer detail. Mass proposes to use a widely-used mesoscale model (the MM4 model), together with conventional coarse-grained operational data sets, to generate detailed quantitative four- dimensional descriptions of a sample set of five or six cases of such cyclones (explosively developing and normally developing marine cyclones, a continental cyclone over level terrain, and cyclones moving across and to the lee of the Rocky Mountains). Analyses of these data sets will include air trajectory computations and sophisticated three-dimensional graphics. Mass expects that these analyses will contribute to the establishment of a new paradigm to modify the useful, but incomplete, Norwegian model. This will contribute to the improvement of short-range, local weather forecasts and to the development of operational versions of numerical mesoscale models.