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Clouds and precipitation

Clouds and precipitation. Identify cloud types from photos Define prefixes and suffixes for cloud types Associate general weather conditions with cloud types Describe different fog types and how they form Explain the collision coalescence process and the Bergeron process

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Clouds and precipitation

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  1. Clouds and precipitation • Identify cloud types from photos • Define prefixes and suffixes for cloud types • Associate general weather conditions with cloud types • Describe different fog types and how they form • Explain the collision coalescence process and the Bergeron process • Describe the basic role naturally occurring atmospheric aerosols play in precipitation formation • Describe how air pollution impacts cloud formation and precipitation • Explain the logic behind weather modification

  2. Clouds

  3. Click on the image to access the NOAA Cloud Chart: http://www.nws.noaa.gov/om/brochures/cloudchart.pdf

  4. Three kinds of fog • Radiation fog • Advection fog • Evaporation fog Evaporation fog on the Kentucky River

  5. Inland radiation fog

  6. Advection fog, California coast

  7. Maine evaporation fog

  8. Evaporation fog

  9. Virga

  10. Precipitation • Collision coalescence process of precipitation formation • Water droplets collide and increase in size until large enough for gravity to pull them out of the cloud • Occurs in tropics and warmer midlatitudes • Precip leaves cloud as liquid water

  11. Collision coalescence process requires presence of condensation nuclei • In clean air, RH must equal 120% for condensation to occur • Air would be considered supersaturated with water vapor • Presence of condensation nuclei allows condensation at 100% humidity

  12. http://www.youtube.com/watch?v=E8AvfXar9zs

  13. Bergeron process of precipitation formation • Occurs in midlatitudes to poles • All three states of water present • Supercooled water crystallizes upon contact with freezing nuclei • Ice crystals form around freezing nuclei and grow through deposition at the expense of water droplets • Precipitation leaves cloud as ice crystal

  14. Precipitation types under Bergeron conditions • Rain – ice crystal melts and liquid water reaches surface • Sleet – warm layer melts ice but refreezes as “pellet”. Winter phenomena. • Snow – ice crystal falls to ground intact • Freezing rain – supercooled liquid water freezes at surface • Hail – summertime thunderstorm phenomena.

  15. Sleet profile Snow temperature profile Freezing rain profile

  16. Aerosol air pollution and its effects on, clouds and precipitation

  17. Clouds last longer in polluted atmosphere Albedo greater in polluted atmosphere

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