Collision Rates of Charged Cloud Droplets in Turbulent Flow

Warm clouds evolve through complex microphysical processes, where turbulence enhances droplet collisions and growth. Electric charges on droplet surfaces further modify these interactions through electrostatic forces. The combined effects of turbulence and electrostatic forces impact collision rates, thus influencing droplet size distribution, precipitation onset, and cloud-climate interactions. We calculate collision rates of charged cloud droplets embedded in a turbulent flow. We characterise the local velocity gradient experienced by sub-Kolmogorov droplet pairs as a linear and stochastic field. We express this velocity gradient as a temporal Fourier series with components constrained to reproduce two-time Lagrangian statistics observed in direct numerical simulation of a homogeneous isotropic turbulent flow. By analysing relative droplet trajectories, we present how the collision rate varies with the electrostatic force relative to the turbulent shear across different size and charge ratios.