Gutiérrez Manuel Santos, Chekroun Mickaël David, Koren Ilan
Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel.
Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, CA 90095, USA.
Sci Adv. 2024 Nov 15;10(46):eadq7518. doi: 10.1126/sciadv.adq7518.
Cloud microphysics studies include how tiny cloud droplets grow and become rain. This is crucial for understanding cloud properties like size, life span, and impact on climate through radiative effects. Small weak-updraft clouds near the haze-to-cloud transition are especially difficult to measure and understand. They are abundant but hard to capture by satellites. Köhler's theory explains initial droplet growth but struggles with large particle groups. Here, we present a stochastic, analytical framework building on Köhler's theory to account for (monodisperse) aerosols and cloud droplet interaction through competitive growth in a limited water vapor field. These interactions are modeled by sink terms, while fluctuations in supersaturation affecting droplet growth are modeled by nonlinear white noise terms. Our results identify hysteresis mechanisms in the droplet activation and deactivation processes. Our approach allows for multimodal cloud's droplet size distributions supported by laboratory experiments, offering a different perspective on haze-to-cloud transition and small cloud formation.
云微物理学研究包括微小云滴如何生长并变成雨滴。这对于理解云的属性（如大小、寿命以及通过辐射效应对气候的影响）至关重要。靠近霾 - 云过渡区的小型弱上升气流云尤其难以测量和理解。它们数量众多，但卫星难以捕捉。科勒理论解释了初始液滴的生长，但对于大粒子群却难以适用。在此，我们基于科勒理论提出一个随机分析框架，以解释（单分散）气溶胶与云滴在有限水汽场中的竞争生长过程中的相互作用。这些相互作用通过汇项进行建模，而影响液滴生长的过饱和度波动则通过非线性白噪声项进行建模。我们的结果确定了液滴激活和失活过程中的滞后机制。我们的方法在实验室实验的支持下能够实现多模态云滴尺寸分布，为霾 - 云过渡和小云形成提供了不同的视角。
