GEOG 2110L Lecture Notes - Freezing Rain, Cloud Condensation Nuclei, Nimbostratus Cloud
17 Mar 2014
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Document Summary
* rain: water vapor condenses into liquid water droplets forming clouds. These droplets coalesce (join together) and become heavy enough to be pulled down by gravity as precipitation and do not evaporate before they hit the ground as a raindrop. * snow: water vapor condenses into liquid water droplets forming clouds. But also within the clouds water vapor changes to ice crystals by deposition. These ice crystals coalesce (join together) and become heavy enough to be pulled down by gravity as precipitation and do not melt before they hit the ground as a snowflake. * cloud droplet avg. size is about 20 microns in diameter & fall very slowly, 1000 m/48 hrs; usually evaporate. * 1 raindrop = about 1 million cloud droplets. * so cloud droplets must coalesce or join together into a raindrop to avoid evaporation. * primary process for forming rain in the middle & high latitudes and only process to form snow.
