Warm-rain initiation: an overview of microphysical mechanisms

Abstract

Rain triggering mechanisms are evaluated in three microphysical steps: droplet activation on cloud condensation nuclei, droplet growth by condensation, and droplet growth by coalescence. Aircraft instruments are becoming available with the potential to measure the very largest particles and cloud droplets at the concentration of raindrops. Recent advances in sampling and analysis techniques have extended observations of cloud microstructure to smaller scales, providing new insight on the growth of droplets by mixing. Continued progress in laboratory research should furnish collection efficiencies for the droplets sizes critical to warm-rain initiation. -from Authors