降雨过程中气溶胶湿沉降的数值模拟

为了参数化降雨湿去除气溶胶的过程,首先定量计算了雨滴和气溶胶的碰撞效率与它们尺度之间的依存关系,以及雨滴尺度谱满足对数正态分布时气溶胶的清除系数与其尺度的依存关系;然后利用多重Monte Carlo算法模拟了降雨过程中气溶胶尺度谱的时间演变过程,考察了气溶胶湿沉降过程与降雨类型和雨强的相关性.当雨滴尺度谱和气溶胶尺度谱均满足对数正态分布时,数值模拟的结果表明,典型的小雨、中雨和大雨过程对中等尺度气溶胶的湿去除效果均不理想,但都可以有效地湿去除大尺度气溶胶和小尺度气溶胶;3种降雨类型对大尺度气溶胶的湿去除效果均依次好于小尺度气溶胶和中等尺度气溶胶;对于任何尺度的气溶胶,雨强的增加将有利于其湿沉降.

Numerical simulation of wet removal of aerosols when raindrop falling

In order to parameterize wet removal of aerosols by precipitation, collision efficiency between aerosol and raindrop as a function of aerosol size and raindrop size is quantitatively calculated, as well as scavenging coefficient of aerosol as a function of aerosol size for log-normal raindrop size distribution. Then multi-Monte Carlo method was used to simulate time evolution of aerosol size distribution when raindrop falling, and the relations were researched between the effect of aerosol wet scavenging and precipitation style as well as rainfall intensity. Numerical simulations showed that, for log-normal raindrop size distribution and log-normal aerosol size distribution, (a) three typical precipitation styles, light, moderate and heavy precipitation, have a weak effect of aerosol wet on scavenging for intermediate aerosols, however scavenging effectively large aerosols and small aerosols; (b) any precipitation styles scavenge large aerosols more effectively than small and intermediate aerosols (both in that order); (c) any size aerosols are scavenged more effectively by raindrop so long as rainfall intensity increases.