Document Type

Data

Publication Date

6-8-2026

Abstract

The onset and rate of drizzle remain open problems in atmospheric physics. This study brings together theory, simulations, and observations to analyze the emergence of power-law tails in droplet size distributions as a signature of a dynamic steady state with coalescence growth balanced by sedimentation removal. By applying a collector-mode approximation, analytic solutions are derived, predicting a droplet radius distribution scaling of $n(r) \sim r^{-4}$, assuming a collection kernel $K \sim r^6$. These predictions are validated against large eddy simulations of stratocumulus clouds, which exhibit the expected $r^{-4}$ scaling in the drizzle tail. Furthermore, in-situ measurements from stratocumulus clouds sampled during the ACE-ENA campaign demonstrate robust power-law behavior in the 30--100~$\mu$m range, yielding a power-law exponent of 4.09. The time to reach this steady state is determined by the growth rate at the minimum size droplets experiencing coalescence.

Comments

This work was supported by the US National Science Foundation under grants AGS-2133229 and AGS-2113060. Y. Ren was supported by Simons Foundation grant PD-Grant-01249402. F. Yang was supported by the DOE-SC BER program under contract DE-SC0012704. K. Chandrakar was supported by the NSF National Center for Atmospheric Research, a major facility sponsored by the US National Science Foundation under cooperative agreement No. 1852977.

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