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M. D. Petters coauthored a single-parameter description of aerosol hygroscopic growth and cloud-condensation activity with S. M. Kreidenweis. The hygroscopicity parameter summarizes how dissolved material changes a droplet's water activity.

Combining that parameter with dry particle diameter estimates the critical supersaturation for activation. The construction connects chemical composition with droplet formation through a measurable, compact model.^[ref]

S. M. Kreidenweis coauthored a hygroscopicity framework with M. D. Petters for relating aerosol water uptake to cloud-condensation activity. The framework balances solute effects with the curvature contribution to droplet vapor pressure.

A particle's dry diameter and hygroscopicity jointly affect its activation threshold. Thus two equally sized particles need not form cloud droplets at the same supersaturation if their compositions differ.^[ref]