Collection and Washout of Airborne Pollens and Spores by Raindrops.

Data on aerodynamic capture of particles are used to estimate efficiency of collection of pollen grains and spores by falling raindrops. Simple probability arguments then yield the fractional removal of airborne pollens and spores by rain. Pollen grains are generally large enough to be washed out by all but the lightest showers of large thunderstorm-type drops; smaller-sized spores experience lower removal rates. Various specialists concerned with pollen dissemination will find rain-scavenging a significant process.