Impact of Aerosols on Convective System Over the North China Plain: A Numerical Case Study in Autumn

The effects of aerosols on deep convective systems are highly uncertain. We used a coupled meteorology and chemistry model to investigate the effects of aerosols on a convective precipitation event that took place in North China from 7 to 10 October 2017. A higher concentration of aerosols can lead to more cloud condensation nuclei, which increases the condensation of water vapor and the formation of cloud droplets. Although the auto-conversion from cloud droplets to rain can be inhibited due to the diminished effective radius of cloud droplets, more cloud droplets can be accreted by raindrops, resulting in a larger effective radius of raindrops and making them less likely to evaporate. Besides, aerosols can contribute to the vapor deposition of snow, and a larger number of cloud droplets can provide the resources needed for the riming growth of snow in the cloud, which eventually results in more and larger snow particles. Also, the net latent heat released by these microphysical processes can increase the vertical velocity and facilitate the development of the convective system. Thereby, the precipitation in North China during the study period was ultimately enhanced. We analyzed the influence of aerosols on this precipitation event from a microphysical perspective, which might improve our understanding of complex aerosol-cloud-precipitation interactions. Plain Language Summary The North China Plain is one of the most polluted regions in China, and heavy aerosol pollution often happens in autumn and winter. Aerosols can modulate the development of deep convective systems via complex microphysical processes. Numerous previous studies have revealed the effect of aerosol on convective precipitation during summer, while the role of aerosol played in autumn is far from well-known. Based on the simulation results of a coupled meteorology and chemistry model, we examined the effect of aerosols on a convective precipitation process in North China Plain in October 2017. Aerosols facilitate the transition of water vapor to cloud, rain, and snow, and ultimately lead to more precipitation reaching the surface.