气溶胶对热带气旋强度及电过程影响的数值模拟研究

将详细的气溶胶活化方案和非感应起电参数化方案耦合到WRF模式的Morrison微物理方案中,在此基础上模拟了理想的热带气旋个例,讨论了气溶胶对热带气旋强度及电活动的影响。研究发现气溶胶对热带气旋强度和电活动的影响在不同发展阶段是不同的。在热带气旋发展阶段,气溶胶增加使云内的云滴数浓度增加,云滴尺度降低,抑制了暖雨过程,未降落的小云滴粒子上升到冻结层之上,冻结形成了更多的冰相粒子,冻结过程释放潜热,激发云系对流发展,使热带气旋强度增强,电活动更为剧烈。而在热带气旋成熟阶段,污染个例中的冰相粒子降落,形成更多的降水,降水粒子在下落过程中对上升气流产生拖曳作用,抑制对流强度。降水粒子在海平面蒸发吸收了大量潜热,使该区域温度降低,这也阻碍了外部暖湿能量向内输送,抑制了对流发展,从而使热带气旋强度降低。而由于污染个例中的冰粒子较少,参与起电过程的冰粒子减少,热带气旋的电活动强度降低。

Numerical simulation of the effects of aerosol on the intensity and electrification of tropical cyclone

The effects of aerosol on intensity and electrification of an idealized tropical cyclone were investigated by coupling an explicit treatment of aerosol activation and electrification parameterizations with Weather Research and Forecasting(WRF) model. Results show that the effects of aerosol on the intensity and electrification of tropical cyclone at different development stages were distinctive. At the developmental stage of tropical cyclone, the increase of aerosol concentration led to the formation of more but smaller cloud droplets, which suppressed warm rain by collision-coalescence process. The smaller cloud droplets were transported to the mixed-phase region and formed more ice particles. The freezing process released more latent heat, which promoted the development of tropical cyclone eyewall and enhanced the intensity and electrification of tropical cyclone. At the mature stage, more ice particles melted into rain water and the rainfall particles dragged the updraft in the falling process. The evaporating effect of rainfall particles at the sea surface absorbed more latent heat and made the temperature decrease in this area. The low temperature area blocked the transportation of warm and wet air into tropical cyclone, and redueed the intensity of tropical cyclone. The electrification process was weaker at mature stage because of less ice particles in the cloud.