四层模式热成风适应
ON THE FORMATION OF THE THERMAL WIND IN THE FOUR-LAYER BAROCLINIC ATMOSPHERIC MODEL
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摘要: 本文用四层模式分析了热成风适应。在适应过程中将发生四种波速不同的惯性波来调节流场和温度场的关系。它们的前阵面的速度分别为306米/秒,114米/秒,36.2米/秒,19.2米/秒。层次愈高,快速惯性波的作用愈大;惯性外波在750毫巴以下才有它的重要性。计算指出:大气中辐合辐散以及垂直运动在垂直方向上互相迭置的现象,是一定条件下热成风适应的结果。本文计算了各种情况的初始条件下温度场和气压场的相互调整。例如375毫巴上单纯非地转风的流场的反气旋涡旋,适应后可建立起对流层暖性、平流层是冷性的高压系统。将初始非热成风的暖温度中心,放在对流层下层和放在对流层中层适应后的结果将不一样。前者只能在对流层下层形成一浅薄的热低压,而后者可在对流层上层建立起一个强大的反气旋,甚至一直影响到平流层。最后,结合气旋发展时所产生的非热成风的特点,讨论了它们的适应。Abstract: A four-layer baroclinic atmosphcric model is adopted to investigate how the nonthermal wind adjusts itself to the thermal wind state.The adjusting process is performed by four gravitational inertial waves whose wave front speeds are about 306 m/sec,114 m/sec, 36 m/sec, and 19 m/sec respectively. It is found that the higher the level the more important is the faster internal inertial wave in the process of adjustment,and that the external wave may be important only below the 750 mb level. The calculated results also indicate that the alternation of the divergence and convergence in the vertical, which is normally termed Dines' compensation, results from the formation of thermal wind under certain initial condition.Calculations of the adjusting process with different initial non-geostrophic states are carried out in order to study the development of the large scale weather system. For example, a non-geostrophic vortex in wind field on the 375 mb level can result in a high with the warm center in the troposphere and the cold center in the stratosphere. Two cases of non-geostrophic state with the same temperature distribution but situated at different layers of the troposphere will result in quite different flow patterns through the adjusting process. A warm center not in geostrophic equilibrium at lower layer, can only give result to a shallow warm low in the lower troposphere, but in the case of warm center not in geostrophic equilibrium at middle layer, an intense anticyclone forms in the high troposphere and even in the lower stratosphere. Finally a preliminary discussion is given to the adjustment of the non-thermal wind which is produced by the process of the formation of the extratropical cyclone.
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