中国气象科学研究院刘煜团队近日研究了湍流对云滴到雨滴自转换率的影响。该项研究成果发表在2025年8月21日出版的《中国科学：地球科学》杂志上。

研究组基于云滴的随机碰撞-聚并方程和云滴到雨滴的自转换率（ARCR）的定义，分析并推导了碰撞-聚并过程的自转换率方程。该方程缩小了随机碰撞-聚并方程的积分范围，为准确高效地计算ARCR提供了理论依据。利用湍流碰撞核和湍流碰撞效率的结果，结合ARCR方程，建立了精确、高效的ARCR模型。

模拟结果表明：(1) 自动转化率(ARCR)随湍流增强而增加。湍流耗散率介于0–20 cm² s^-3时增长率最快，20–50 cm² s^-3时增速减缓，50–500 cm² s^-3时增长幅度居中。(2) 与无湍流情况相比，当湍流耗散率为100 cm² s^-3时，自动转化率提升约20%；当耗散率达500 cm² s^-3时，增幅超过100%。因此，仅当湍流耗散率超过100 cm² s^-3时，湍流对自动转化率才会产生显著影响。(3) 湍流对自动转化率的影响随云水含量增加而增强。无湍流条件下，当云水含量超过0.68 g m^-3时，云水含量与自动转化率呈强线性关系。(4) 湍流对自动转化率的影响随云滴数浓度增加而快速减弱。(5) 随着形状参数减小（即云滴谱相对离散度增大，对应云滴谱拓宽），湍流对自动转化率的增强效应更加显著。

附：英文原文

Title: Impact of turbulence on the autoconversion rate from cloud droplets to raindrops

Author: Yu LIU

Issue&Volume: 2025/08/21

Abstract: Based on the stochastic collision-coalescence equation for cloud droplets and the definition of the autoconversion rate from cloud droplets to raindrops (ARCR), this study analyzes and derives an ARCR equation from the collision-coalescence process. This equation narrows the integration range of the stochastic collision-coalescence equation, providing a theoretical basis for accurately and efficiently calculating the ARCR. Utilizing the results of the turbulent collision kernel and turbulent collision efficiency, as well as the ARCR equation, an accurate and efficient model for the ARCR was established. Modeling results indicate the following: (1) The ARCR increases with the enhancement of turbulence. The rate of increase was fastest when the turbulent dissipation rate was between 0 and 20cm2s3, slower when it was between 20 and 50cm2s3, and intermediate when it was between 50 and 500cm2s3. (2) Compared to the case without turbulence, the ARCR increased by approximately 20% when the turbulent dissipation rate was 100cm2s3, and by over 100% when it was 500cm2s3. Therefore, turbulence has a significant impact on the ARCR only when the turbulent dissipation rate exceeds 100cm2s3. (3) The influence of turbulence on ARCR results increases with an increase in cloud water content. When there was no turbulence and the cloud water content exceeded 0.68gm3, a strong linear relationship existed between cloud water content and the ARCR. (4) The effect of turbulence on the ARCR results decreases rapidly with an increase in the cloud droplet number concentration. (5) The impact of turbulence on the ARCR becomes stronger with a decrease in the shape parameter, which corresponds to the increase in the relative dispersion of the cloud droplet spectrum (i.e., as the cloud droplet spectrum broadens).

DOI: 10.1007/s11430-025-1633-1

Source: https://www.sciengine.com/SCES/doi/10.1007/s11430-025-1633-1