How do clouds form?

Introduction

Cloud formation is a complex atmospheric process influenced by various physical and chemical factors. Understanding how clouds form involves examining the roles of water vapor, atmospheric dynamics, and other environmental conditions.

Key Insights

Water Vapor and Condensation Nuclei:
- Clouds form when water vapor in the air condenses onto cloud condensation nuclei (CCN) or ice nuclei (IN) . The presence of foreign nuclei allows cloud formation at lower supersaturation levels.
Atmospheric Dynamics:
- Vertical and horizontal movements in the atmosphere, driven by heat from the sun and differential motion, play crucial roles in cloud formation. Vertical motion causes the lower air to expand and rise, leading to condensation and cloud formation .
- Turbulence and advection (the horizontal transfer of heat and moisture) also significantly influence cloud development.
Thermal Instability and Radiation:
- Thermal instability in a radiatively heated and cooled medium can lead to cloud formation. Radiation forces can accelerate clouds, especially when ions recombine and opacity increases.
Experimental Observations:
- Experimental setups simulating cloud formation show that the interaction of warm vapor with cold air leads to the formation of turbulent plumes and the gradual growth of clouds as temperature drops.
Molecular Clouds:
- Molecular clouds in space may form through the agglomeration of dense phases of the interstellar medium, rather than by in situ cooling of atomic gas.

Conclusion

Cloud formation is primarily driven by the condensation of water vapor onto nuclei, influenced by atmospheric dynamics such as vertical and horizontal movements, turbulence, and advection. Thermal instability and radiation forces also play significant roles, particularly in space environments. Experimental studies and observations further support these mechanisms, highlighting the complex interplay of factors involved in cloud formation.

How do clouds form?

Summary

Introduction

Key Insights

Conclusion

Sources and full results

On the Forms of Clouds

The paper explains that diminished specific gravity, differential horizontal motion, and sun's heat expansion contribute to the formation of various cloud forms, including cumulus, stratus, and cirro-cumulus.

The formation of molecular clouds

Molecular clouds may form not by in situ cooling of atomic gas, but rather by the agglomeration of the dense phase of the interstellar medium, much of which is already in molecular form.

A Remarkable Form of Cloud

Cirro-filum, or ice-cloud disposed in threads, is a remarkable cloud formation, and its formation is well-researched in papers by Linn and myself.

Cloud Formation and the Possible Significance of Charge for Atmospheric Condensation and Ice Nuclei

Solar variability may influence cloud formation through ionization and changes to cloud condensation nuclei and ice nuclei, but definitive experimental work is needed for confirmation.

Experimental Study of Cloud Formation

This study demonstrates the turbulent nature of convection and gradual growth of cumulus clouds in an experimental setup, aiding in cloud formation prediction for known environmental conditions.

Dynamic factors in the formation of the earth’s cloud field

This study developed a general approach to cloud formation, considering heat and water-vapor flow equations in a turbulent atmosphere, to better understand the formation and development of various cloud types in nature.

The microphysics of clouds

Recent research reveals that artificial stimulation of clouds may be possible, with a new theory on ice crystal formation and potential for rain formation in tropical clouds.

CLOUD FORMATION AND ACCELERATION IN A RADIATIVE ENVIRONMENT

Thermal instability can form long-lived clouds and accelerate them to supersonic velocities, but single cloud morphology cannot be maintained due to destructive processes.

Boundary Layer Clouds

Boundary layer clouds alter short and long-wave radiative flux divergence, modulate BL dynamics, turbulence generation, and evolution, and play a significant role in climate change.

Reshaping the Theory of Cloud Formation

Current estimates of indirect aerosol forcing may be too low, as current insights into cloud formation suggest that current estimates may be too low.

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