GEO 211 1st Edition Lecture 17 Outline of Last Lecture I Chapter 6 determining stability of the atmosphere A By comparing lapse rate curves 3 atmospheric conditions exist 1 Absolutely stable 2 Absolutely unstable 3 Conditionally unstable B Conditions necessary to bring about stable atmosphere C Conditions necessary to bring about unstable atmosphere Outline of Current Lecture II Chapter 7 precipitation A Typical raindrop B Precipitation processes 1 Collision o Terminal velocity 2 Ice crystal Bergeron process Accretion Aggregation C Formation of raindrops in warm clouds depends on D Thin nimbostratus clouds have E Thick cumulonimbus have Current Lecture II Chapter 7 precipitation Typical cloud droplet 20 m in diameter A Typical raindrop 2000 m 100 times larger than dropet Condensation nucleus 0 2 m B Precipitation processes 1 Collision coalescence droplet growth in warm clouds larger droplets accelerated downwards by gravity collide and merge with smaller These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute droplets o Terminal velocity constant speed obtained when upward air resistance balances with downward force of gravity 2 Ice crystal Bergeron process droplet growth in cold clouds with temperatures below 32 F o Middle higher latitude clouds o Cloud droplets don t freeze at 0 C freeze at 40 C Cloud top with only ice crystals is glaciated Growth of droplet crystals is ice crystals Accretion falling ice crystals collide with super cooled cloud droplets and freeze on contact Aggregation falling ice crystals collide and stick together to other ice crystals o Produces snowflakes If snowflake melts continues to fall as raindrop o Thus much rain in cold clouds begins as snow C Formation of raindrops in warm clouds depends on 1 liquid water content major factor 2 range of cloud droplet sizes 3 Electrical charges and fields that bind droplets 4 cloud thickness 5 Speed of updrafts in the cloud D Thin nimbostratus clouds have weak updrafts thus light showers E Thick cumulonimbus have strong updrafts thus heavy showers
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