A concept of a convection-cloud chamber to study aerosol-cloud-drizzle interactions

Bulletin of the American Meteorological Society · 2026-04-28

Abstract Understanding and quantifying the full chain of processes from aerosol activation to drizzle formation, and the associated feedbacks to the aerosol chemical and physical properties, all within a turbulent cloud are some of the toughest challenges in atmospheric chemistry and physics and are keys to the cloud-precipitation puzzle. This paper describes a concept for a new type of research facility consisting of a cloud chamber plus associated instrumentation and computational models, to explore aerosol-cloud interactions and processing, cloud optical properties, entrainment-cloud interactions, and quantitative assessment of drizzle onset. The envisioned design is for a 3-m by 3-m by 9-meter chamber, such that the height is sufficient to achieve long lifetimes for aerosol processing and for significant drizzle growth by collision and coalescence. A suite of computational tools for simulating microphysical properties in the chamber provides a digital twin for designing the chamber and a range of example experiments. Theory and test results from novel remote sensing systems for exploring chemical and physical interactions and evolution of aerosols, cloud droplets, and drizzle within turbulent clouds are described. Testing of technology needed for operation of a large-volume chamber, including aerosol generation methods and novel materials for water-vapor boundary conditions are described. Simulations suggest that spatially uniform turbulence and microphysical properties can be sustained in steady-state, with reasonable aerosol and water vapor fluxes, and that substantial drizzle can be produced through collision and coalescence of cloud droplets. Remaining challenges for more detailed engineering design, and a discussion of possible first-light experiments are described.

Generating a stratocumulus-like cloud top in a convection-cloud chamber

Proceedings of the National Academy of Sciences · 2026-03-12

Stratocumulus-topped boundary layers play a crucial role in influencing daily weather and earth energy balance. Entrainment at the stratocumulus cloud top affects the cloud's lifetime, precipitation, and radiative properties, but our understanding remains limited due to the lack of resolution in both field observations and numerical simulations. A recently proposed convection-cloud chamber with detailed control of sidewall temperatures can provide a unique opportunity to explore this mechanism in a laboratory setting. In this work, we use numerical simulations to demonstrate that this design can produce a cloud top that mimics the entrainment interfacial layer in a stratocumulus cloud. Our results show that a steady-state cloud can be formed by cooling the lower portions of the sidewalls and warming the bottom surface, while a temperature inversion at the cloud top can be generated by keeping the upper sidewalls and top surface warmer than the bottom. The turbulent kinetic energy profile and budget are similar to those found in a convective boundary layer, and inhomogeneous mixing near the cloud top can be observed. These findings significantly enhance the scientific value of constructing the tall convection-cloud chamber.

A Prospective Comparison of the Environmental Impact, Cost, and Surgical Site Infection Rate of 1 Versus 2 Trays in Mohs Micrographic Surgery

Dermatologic Surgery · 2026-03-09

LES output for the work "Generating a Stratocumulus-Like Cloud Top in a Convection-Cloud Chamber"

Open MIND · 2025-07-10

This is the LES output for the work "Generating a Stratocumulus-Like Cloud Top in a Convection-Cloud Chamber". The Wang2025CloudTop_profiles.tar.gz file contains only the vertical profiles, and the Wang2025CloudTop.tar.gz file contains the entire 3D output. BL_3m and BL_6m represent the mixed-layer depth.UpperDry and UpperAdiabatic indicate that the upper walls are dry or hydrophobic (i.e., adiabatic with respect to moisture). Under BL_6m:_weakLSC and _strongLSC mean that the across-side-wall ΔT is 2 K and 4 K, respectively.DryChamber means the entire chamber is dry (i.e., dry convection).PassiveTracer contains runs with artificial passive tracers to investigate the entrainment rate. Under PassiveTracer:_constant means that C above z = 6 m is kept at 1.

Why is height-dependent mixing observed in stratocumulus clouds?

Atmospheric chemistry and physics · 2025-12-18

Abstract. Recent aircraft measurements in stratocumulus clouds suggest that entrainment mixing is inhomogeneous (IM) near cloud top and homogeneous (HM) within the cloud. However, this proposed height-dependence of mixing transition is uncertain because of artifacts involved in the aircraft measurements. In this study, we use the Explicit Mixing Parcel Model to simulate mixing scenarios in stratocumulus clouds and reconstruct the virtual aircraft measurements to investigate the mixing signature. Results show that, from the aircraft-measurement perspective, the mixing signature always exhibits IM characteristic near cloud top and HM characteristic within cloud, independent of the types of the local entrainment-mixing process. The appearance of the vertical IM-to-HM transition is essentially a collective behavior of multiple parcels sampled at the same height, experiencing distinct entrainment-mixing-evaporation histories. This bulk view of mixing process, which is widely used for aircraft measurements, could lead to misinterpretations of the true mixing mechanism occurring in clouds. Our result underscores the limitations of using aircraft measurements to identify the entrainment-mixing mechanism at the process level.

Why Is Height-Dependent Mixing Observed in Stratocumulus?

2025-07-31

Abstract. Recent aircraft measurements in stratocumulus clouds suggest that entrainment mixing is inhomogeneous (IM) near cloud top and homogeneous (HM) within the cloud. However, this proposed height-dependence of mixing transition is uncertain because of artifacts involved in the aircraft measurements. In this study, we use the Explicit Mixing Parcel Model to simulate mixing scenarios in stratocumulus clouds and reconstruct the virtual aircraft measurements to investigate the mixing signature. Results show that, from the aircraft-measurement perspective, the mixing signature always exhibits IH characteristic near cloud top and HM characteristic within cloud, independent of the types of the local entrainment-mixing process. The appearance of the vertical IM-to-HM transition is essentially a collective behavior of multiple parcels sampled at the same height, experiencing distinct entrainment-mixing-evaporation histories. This bulk view of mixing process, which is widely used for aircraft measurements, could lead to misinterpretations of the true mixing mechanism occurring in clouds. Our result underscores the limitations of using aircraft measurements to identify the local entrainment-mixing mechanism at the process level.

A Model Intercomparison Study of Aerosol-cloud-turbulence Interactions in a Cloud Chamber. Part 1: Model Results

2025-06-26

This study presents the first model intercomparison of aerosol-cloud-turbulence interactions in a controlled cloudy Rayleigh-Bénard Convection chamber environment, utilizing the Pi Chamber at Michigan Technological University. We analyzed simulated cloud chamber-averaged statistics of microphysics and thermodynamics in a warm-phase, moist environment under steady-state conditions at varying aerosol injection rates. Simulation results from seven distinct models (DNS, LES, and a 1D turbulence model) were compared. Our findings demonstrate that while all models qualitatively capture observed trends in droplet number concentration, mean radius, and droplet size distributions at both high and low aerosol injection rates, significant quantitative differences were observed. Notably, droplet number concentrations varied by over two orders of magnitude between models, indicating sensitivities to the model treatments in droplet activation and removal and wall fluxes. Furthermore, inconsistencies in vertical relative humidity profiles and in achieving steady-state liquid water content suggest the need for further investigation into the mechanisms driving these variations. Despite these discrepancies, the models generally reproduced consistent power-law relationships between the microphysical variables. This model intercomparison underscores the importance of controlled cloud chamber experiments for validating and improving cloud microphysical parameterizations. Recommendations in future modeling studies are also highlighted, including constraining wall conditions and processes, investigating droplet/aerosol removal (including sidewall losses), and conducting simplified experiments to isolate specific processes contributing to model divergence and reduce model uncertainties.

Scientific Directions for Cloud Chamber Research: Instrumentation, Modeling, New Chambers, and Emerging Chamber Concepts

Bulletin of the American Meteorological Society · 2025-03-17 · 4 citations

Over 75 scientists from 13 countries gathered to learn about and discuss the latest scientific research results from large laboratory cloud chamber facilities, as well as new developments in cloud chamber instrumentation and modeling efforts, and emerging cloud chamber designs that will open new scientific research directions.

A Model Intercomparison Study of Aerosol‐Cloud‐Turbulence Interactions in a Cloud Chamber: 1. Model Results

Journal of Advances in Modeling Earth Systems · 2025-07-01 · 2 citations

Abstract This study presents the first model intercomparison of aerosol‐cloud‐turbulence interactions in a controlled cloudy Rayleigh‐Bénard Convection chamber environment, utilizing the Pi Chamber at Michigan Technological University. We analyzed simulated cloud chamber‐averaged statistics of microphysics and thermodynamics in a warm‐phase, cloudy environment under steady‐state conditions at varying aerosol injection rates. Simulation results from seven distinct models (DNS, LES, and a 1D turbulence model) were compared. Our findings demonstrate that while all models qualitatively capture observed trends in droplet number concentration, mean radius, and droplet size distributions at both high and low aerosol injection rates, significant quantitative differences were observed. Notably, droplet number concentrations varied by over two orders of magnitude between models for the same injection rates, indicating sensitivities to the model treatments in droplet activation and removal and wall fluxes. Furthermore, inconsistencies in vertical relative humidity profiles and in achieving steady‐state liquid water content suggest the need for further investigation into the mechanisms driving these variations. Despite these discrepancies, the models generally reproduced consistent power‐law relationships between the microphysical variables. This model intercomparison underscores the importance of controlled cloud chamber experiments for validating and improving cloud microphysical parameterizations. Recommendations for future modeling studies are also highlighted, including constraining wall conditions and processes, investigating droplet/aerosol removal (including sidewall losses), and conducting simplified experiments to isolate specific processes contributing to model divergence and reduce model uncertainties.

LES output for the work "Generating a Stratocumulus-Like Cloud Top in a Convection-Cloud Chamber"

Zenodo (CERN European Organization for Nuclear Research) · 2025-07-10

This is the LES output for the work "Generating a Stratocumulus-Like Cloud Top in a Convection-Cloud Chamber". The Wang2025CloudTop_profiles.tar.gz file contains only the vertical profiles, and the Wang2025CloudTop.tar.gz file contains the entire 3D output. BL_3m and BL_6m represent the mixed-layer depth.UpperDry and UpperAdiabatic indicate that the upper walls are dry or hydrophobic (i.e., adiabatic with respect to moisture). Under BL_6m:_weakLSC and _strongLSC mean that the across-side-wall ΔT is 2 K and 4 K, respectively.DryChamber means the entire chamber is dry (i.e., dry convection).PassiveTracer contains runs with artificial passive tracers to investigate the entrainment rate. Under PassiveTracer:_constant means that C above z = 6 m is kept at 1.