大气浮力频率的时空变化及其影响因子

采用NCEP/NCAR再分析资料，分别将一日4次、日平均、月平均资料作为输入进行计算，分析了浮力频率在不同尺度下的时间变化及空间变化，发现浮力频率的分布与纬度和高度、海洋和陆地、山脉和地形分布等有关。一般认为，浮力频率取决于上下层的温度差。通过对其表达式的推演，指出浮力频率除了与上下层温度差有关外，也与气温本身有关，是两者的非线性函数。针对不同时间尺度及空间的采样样本，研究了气温和垂直温差在浮力频率时空变化中的相对重要性。结果表明，对浮力频率的某些时空变化，在一些区域，气温本身的变化也很重要，其影响甚至能超过上下层温度差的作用。

Dominance analysis of factors influencing temporal-spatial variations of atmospheric buoyancy frequency

Buoyancy frequency is an important concept in atmospheric dynamics.Based on NCEP/NCAR reanalysis data, the data of four times a day, daily average and monthly average are used as inputs to calculate, and the temporal and spatial changes of buoyancy frequency at different scales are analyzed.It is found that the spatial distribution of buoyancy frequency is related to latitude and altitude, ocean and land, mountains and terrain.It is generally believed that the buoyancy frequency depends on the temperature difference between the upper and lower layers.Through the deduction of its expression, it is pointed out that the buoyancy frequency is not only related to the temperature difference between the upper and lower layers, but also related to the temperature itself, which can be expressed as a nonlinear function of the two.The relative importance of air temperature and vertical temperature difference in the temporal and spatial variations of buoyancy frequency is studied by a statistical fitting method.Results show that for some temporal and spatial variations of the buoyancy frequency, the variation of air temperature itself is also very important in some areas, and its influence can even exceed the effect of temperature difference between the upper and lower layers.