Turbulence is ineffective in causing raindrop growth in polluted clouds

TL;DR

This study demonstrates that turbulence does not significantly promote raindrop growth in polluted clouds unless droplets have a broad size distribution, highlighting the need for better microphysical models.

Contribution

It provides experimental evidence that turbulence's role in droplet growth is limited and depends on droplet size distribution, challenging previous assumptions.

Findings

Turbulence does not always enhance droplet collision and coalescence.

Broader droplet size distributions are necessary for turbulence to influence growth.

Improved parameterisations are needed for accurate cloud microphysics modeling.

Abstract

Aerosol-cloud interactions represent the largest uncertainty in climate-change assessment, and while cloud turbulence is considered crucial for droplet growth, its precise role remains unclear. Our laboratory-controlled studies show that turbulence does not always enhance collision and coalescence; instead, its influence emerges only when droplets have a sufficiently broad size distribution. The dissipative-scale droplet behaviour underscores the importance of improved parameterisations to accurately model cloud microphysics.