雨滴下落过程谱分布演变的数值模拟

Spectrum evolution in the raindrop falling process: Numerical simulation

利用一维雨滴分档模式,以飞机观测的空中雨滴谱和边界层气象要素廓线作为模式的初始背景场,模拟了雨滴在出云后下落过程中谱分布的演变。结果表明,一维雨滴分档模式能较好地模拟雨滴在下落过程中的蒸发、碰并和破碎过程;模拟的滴谱呈多峰分布。蒸发作用使得雨滴的直径变小,对小雨滴的消耗较大雨滴更为明显,并能增大中等大小雨滴的数浓度,但在整体上并不会改变雨滴的谱型。碰并和破碎机制可以使得雨滴谱呈现多峰分布,并增大了滴谱的谱型变化。

By using a one-dimensional raindrop category model and taking the aircraft observations of raindrop size distribution in the air and meteorological elements＇ profiles in the boundary layer as the initial background field, the evolution of raindrop size distribution during the falling process was simula- ted and analyzed. The results showed that the one-dimensional raindrop category model could simulate the evaporation, coalescence and breakup processes of the raindrop properly. The simulated raindrop spectra presented a multi-peak distribution. Evaporation would make the diameters of raindrops smaller. It affected small size raindrops more seriously than big size raindrops and increased the concentration of number of medium-sized raindrops, but it would not to change the overall spectral shape of raindrops. The multi-peak raindrop size distribution was caused by the coalescence and breakup mechanism, which were key factors in the change of raindrop spectra.