Journal Article

Enhancing Turbulent Mixing and Microphysical Uniformity in a Tall Convection‐Cloud Chamber Through Idealized Heterogeneity of Boundaries

Pressel, Kyle G., Ovchinnikov, Mikhail, Shaw, Raymond A., Thomas, Lois, Yang, Fan, Wang, Aaron

2025

Overview

A large convection cloud chamber has been proposed for exploring aerosol–cloud–drizzle interactions under well‐controlled turbulent conditions. Recent theoretical and numerical studies suggest that a convection cloud chamber with two heated and two cooled sidewalls can significantly enhance the liquid water content and thus benefit drizzle initiation. However, a chamber with such a sidewall configuration develops stable stratification and extremely weak turbulence therein. In this study, we conduct large‐eddy simulations of a tall convection chamber with five different sidewall configurations consisting of alternating warm and cold patches. For each configuration, the total surface area of warm patches equals that of cold patches, resulting in the same expected cloud‐free supersaturation based on a flux budget model. Results show that changing the sidewall configuration, while keeping all other factors constant, can substantially enhance turbulent mixing and improve the uniformity of thermodynamic and cloud microphysical properties in the bulk region of the chamber. In addition, turbulence strength is positively correlated with liquid water content and negatively correlated with cloud droplet number concentration, consistent with theoretical predictions. Our results highlight the advantage of building a large cloud chamber using modular patches with individually controllable temperature and humidity to achieve well‐mixed conditions. Plain Language Summary Theoretical and numerical studies have suggested that cloud droplets in a tall convection cloud chamber with a height of about 10 m can collide with each other to form drizzle drops naturally—a key, but still not fully understood, process for warm rain precipitation. Due to the large height‐to‐width ratio, a previous study shows that a tall convection chamber with two hot sidewalls and another two cold sidewalls is needed to achieve high supersaturation and liquid water content that can benefit drizzle initiation. However, such a sidewall configuration would lead to weak turbulence and stable stratification in the bulk region of the chamber. This study shows that using tiled sidewalls consisting of alternating hot and cold patches can enhance turbulent mixing and the uniformity of cloud microphysical properties, while keeping other factors constant. In addition, increasing turbulent strength increases liquid water content but decreases cloud droplet number concentration, and their scaling relationships from the simulation are consistent with theoretical predictions. Key Points We conduct large‐eddy simulations of a tall convection chamber with tiled sidewalls configured with alternating warm and cold patches Changing tiled sidewall patterns alone can enhance turbulent mixing and microphysical uniformity in a convection cloud chamber Enhanced mixing correlates positively with liquid water content but negatively with number concentration, matching theoretical predictions

• Publisher: John Wiley & Sons, Inc,American Geophysical Union (AGU)
• Subject: Aerosol-cloud interactions / Aerosols / Atmospheric boundary layer / Boundary conditions / Cloud Chamber / Cloud chambers / Cloud droplet concentration / Cloud droplets / Cloud Microphysics / Cold / Convection / Drizzle / ENVIRONMENTAL SCIENCES / Heterogeneity / Large-eddy Simulation / Liquid water content / Moisture content / sidewall / Simulation / Stratification / Supersaturation / Temperature / Turbulence / Turbulent mixing / uniformity / Water content