MET 260 Lecture Notes - Lecture 8: Ice Crystals, Cumulus Cloud, Vertical Draft
Document Summary
Precipitation- any form of water that falls from a cloud and reaches the ground. Condensation alone is not enough to produce precipitation. Cloud droplets must grow (cid:883)(cid:882)(cid:882)x"s larger to become the size of a typical raindrop. Water molecules evaporate from a curved surface. Smaller droplets (without nuclei) have greater curvature, and thus more evaporation takes place than in larger droplets. Condensation will not be able to keep up with evaporation in the struggle to maintain saturation: very small droplets will evaporate. Condensation being on cloud condensation nuclei, often with rh around 78% An inseparable solution forms between water and nuclei. Any increase in rh will result in vapor molecules attaching themselves at a faster rate than they leave: causing the droplet to grow. Larger drops that contain nuclei grow at the expense of smaller drops that do not contain nuclei. But the droplets will still be too small to fall as rain.
