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Cloud Formation and Types

Cloud Formation and Types. Why Do Clouds Form?. Clouds need three things to form: Cooling Condensation Nuclei Saturated Air. What Causes Cooling?. There are Four Processes that lead to the cooling of air- #1 Convective Cooling Rising air expands because pressure decreases

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Cloud Formation and Types

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  1. Cloud Formation and Types

  2. Why Do Clouds Form? • Clouds need three things to form: • Cooling • Condensation Nuclei • Saturated Air

  3. What Causes Cooling? There are Four Processes that lead to the cooling of air- • #1 Convective Cooling Rising air expands because pressure decreases Expansion causes the air to become cooler • Adiabatic Temperature Changesare changes in temperature from the expansion or compression of air

  4. Adiabatic Temperature Change(Convective Cooling Continued) • For dry air, temperature changes 1ºC every 100 meters in elevation change • 5.4ºF for every 1000 feet • For moist air, the cooling rate varies from 0.5ºC per 100 m for air with a high moisture content to 0.9ºC per 100 m for air with a very low moisture content • Average is 0.7ºC per 100 m

  5. Convective Cooling (Continued) • When the rising air reaches the dew point temperature, water vapor begins to condense • The condensation level is the height above the ground at which condensation takes place

  6. #2 Forceful Lifting • An event occurs that forces the air to rise • Air moving up and over a mountain

  7. #3Temperature Changes • Two air masses with different temperatures mix • The temperature change of the combined air masses may be cooler than the dew point

  8. #4 Advective Cooling • Warm, moist air moving over cool land or water causes the air temperature to drop • Forms low clouds or fog

  9. Cloud Condensation Level

  10. Condensation Nuclei • The water vapor needs a surface on which to condense. • Condensation nuclei are tiny, less than 0.001 mm in diameter. There MUST be solid particles in the air for the water vapor to condense onto. • Examples include: • Suspended particles of atmospheric dust • mineral particles • ash from fires • volcanic dust • microscopic organisms • vaporized meteors • salt from sea spray

  11. Saturated Air • Air temperature must be equal to the dew point. • Thus, 100% humidity. . . Clouds form!

  12. Let’s Make a Cloud! Magic?!. . . No, science.

  13. Cloud Types 1 • Stratus Clouds • sheet-like, or layered. • Cumulus Clouds • puffy, like cotton balls. • Cirrus Clouds • thin and wispy.

  14. Cloud Types 2 • High Clouds (above 6,000 m) • Cirrus • Cirrostratus • Mid-level Clouds • Altostratus • Altocumulus • Low-level Clouds • Stratus • Cumulus, Cumulonimbus

  15. Cirrus Clouds (thin and wispy)

  16. Cirrostratus Clouds

  17. Altocumulus Clouds

  18. Fair-Weather Cumulus Clouds

  19. Cumulonimbus 1

  20. Cumulonimbus 2

  21. Finally, what do we call a cloud on the ground? FOG!

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