中层和热层大气的湍流结构

本文首先讨论了中层和热层大气湍流谱区的划分,发现对于同样尺度的湍流,在不同高度对应的谱区是不同的。随着高度的增加,愈向耗散区一端移动。其次,从理论上讨论和计算了不同高度的湍谱分布。最后,导出了湍流扩散系数的公式。湍流扩散对于高层大气成份的垂直分布有很大的影响。观测结果表明,并不是所有尺度的湍流对高层大气成份的垂直分布都发生影响,而是具有某一尺度的小尺度湍流起主要作用。我们引出了一个有效湍流尺度的概念,并从理论上计算了湍流扩散系数随高度的分布。结果与观测的氩和氦随高度的分布反推出来的湍流扩散系数相符合,同时也与ALADDN 1试验测量的结果相符合。

ON TURBULENCE STRUCTURE OF MESOSPHERIC AND THERMOSPHERIC ATMOSPHERES

This paper describes the spectral ranges of the turbulences of mesospheric and thermospheric atmospheres. It is found that the corresponding spectral regions at different heights for the turbulences of a similar scale are different from each other. Shift towards the side of the dissipating region occurs with the increase in height. Turbulent spectral distributions at various heights are theoretically calculated. For-mulas of trubulence coefficients are derived and a conceptual idea of effective tur-bulence scales developed. Distributions of turbulence coefficients with height are also computed, which agree very well with those derived from the observed Ar and He dis-tributions at various heights.