15 Jan 2024
 | 15 Jan 2024

Preliminary evaluation of the effect of electro-coalescence with conducting sphere approximation on the formation of warm cumulus clouds using SCALE-SDM version 0.2.5-2.3.0

Ruyi Zhang, Limin Zhou, Shin-ichiro Shima, and Huawei Yang

Abstract. The analytic expression for electro-coalescence with the accurate electrostatic force for a pair of droplets with opposite sign charges is established by treating the droplets as conducting spheres (CSs). Then, the weak electric effect on a cumulus cloud is investigated by size resolved cloud model with particle treatment of the super-droplet method. The results show that with CS treatment, the electrostatic force contributes a larger effect on cloud evolution than previous research. With a 3 % lower charge limit of the maximum charge amount of the droplet, the domain total precipitation with CS treatment for droplets with opposite signs is 52.5 % higher than that with the no charge (NC) setting. Compared with previous work by Khain et al. (2004), with the multi-image-dipole treatment of CS, the amount of precipitation is 5.42 % higher. It is found that the charged droplets could affect cloud formation even when the droplet charge is lower charge limit. High pollution levels result in greater sensitivity to electro-coalescence. The results show that when the charges ratio between two droplets is over 100, the short-range attractive electric force due to the multi-image dipole would also significantly enhance precipitation for the cumulus. It is indicated that although the accurate treatment of the electrostatic force with CS method would require 30 % longer computation time than before, it is worthwhile to include it in cloud, weather, and climate models.

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Ruyi Zhang, Limin Zhou, Shin-ichiro Shima, and Huawei Yang

Status: final response (author comments only)

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Ruyi Zhang, Limin Zhou, Shin-ichiro Shima, and Huawei Yang

Data sets

Ruyizhang2333/SCALE-SDM-electro-coalescence: SCALE-SDM-electro-coalescence Ruyi Zhang

Model code and software

Ruyizhang2333/SCALE-SDM-electro-coalescence: SCALE-SDM-electro-coalescence Ruyi Zhang

Ruyi Zhang, Limin Zhou, Shin-ichiro Shima, and Huawei Yang


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Short summary
Solar activity weakly ionizes Earth's atmosphere, charging cloud droplets. Oppositely charged droplets tend to stick together, phenomenon called electro-coalescence. We introduced an analytical expression of electro-coalescence probability, used it in a warm cumulus cloud simulation. Results show charge cases increase rain and droplet size, the new method outperforming previous ones. While new method requires longer computation time, its impact on rain justifies inclusion in meteorology models.