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Chapter 5 Clouds What are the Basic Elements of Weather & Climate (list 6) Temperature Humidity Clouds Precipitation Pressure Wind Precipitation List 6 forms of precipitation: What is graupel? Clouds: • A visible aggregate of minute droplets of water or tiny ice crystals (or both). For Clouds to form, TWO conditions must exist: 1. Air is lifted, cooled adiabatically, until the air is SATURATED. Then water vapor can condense into water droplets What do all these pictures have to do with clouds? Cloud Condensation Nuclei 2. Water vapor needs to condense (stick) onto a SURFACE. A “surface” can be microscopic dust particles, smoke, salt, pollen, volcanic ash, soot from combustion or forest fires. Without the condensation nuclei surface, the air needs to be greater than 100% humidity or very, very low temperatures (so the water vapor has very little KE and the particles can slow down enough to collide and stick together. 2 types of condensation nuclei Hygroscopic nuclei • “Water-seeking” • Effective sites for water vapor to condense into droplets. • Form larger water droplets • • • • • Example: salt particles Hydrophobic nuclei “water-repelling” Not efficient for forming water droplets only if the relative humidity reaches 100% Form smaller droplets Initially, cloud droplet formation is rapid, but it slows as the water vapor in the air is used up The size of cloud droplets can vary. It takes about a million cloud droplets to form a single raindrop. Classification High Clouds Prefix: ____________ _____________meters Middle Clouds Prefix: ___________ ____________meters Low Clouds Prefix: ____________ _____________meters Clouds of Vertical Development Cloud Types Height Composition Description Cloud Types: height and form Pg. 134 Cirrus Clouds Cirrostratus Cirrocumulus Aircraft Contrails: Condensation trails of ice crystals Altocumulus Altostratus Nimbostratus Cumulus Clouds Cumulonimbus: Dark, dense, towering clouds with anvil-tops that reach heights of 30,000 ft. and produce thunderstorms, hail and tornados. • Why are high clouds always so thin compared to low clouds? Lenticular Clouds