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Thunderstorms

Thunderstorms. Mr. Beavers’ Earth Science On Line!. We have a new class website – you will find class information, assignments, and this powerpoint there! http://mr-beavers.wikispaces.com/ (there’s not a “www”). Air Density. What is the formula for density?

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Thunderstorms

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  1. Thunderstorms

  2. Mr. Beavers’ Earth Science On Line! • We have a new class website – you will find class information, assignments, and this powerpoint there! • http://mr-beavers.wikispaces.com/ • (there’s not a “www”)

  3. Air Density • What is the formula for density? • What factors determine the density of air in this room? • What factors determine the density of air in a balloon?

  4. Balloon Experiment • Two balloon experiment – one warm and one cool… what will happen?

  5. Plastic Bag Experiment • How does temperature effect the density of air? • What happens to the plastic bag filled with room temp air? • What happens to the plastic bag filled with warmer than room temp air?

  6. Thunderstorms!!! • What do you know now? • Where in the US are thunderstorms most likely? • How do thunderstorms form? • Write down what you know now. The exit slip for the day will be to compare where you started and what you learned.

  7. Thunderstorms and Rising Air • Thunder storms are started when air rises, cools and starts to loose its moisture. • That’s really basic! We’ll get more in depth soon!

  8. Density and Rising Air As air warms, it becomes less dense than surrounding air so it rises (things that are less dense rise or float) • 4 ways to cause air to rise: • you will need to be able to explain how each one works

  9. Convection • 1) Convection: air motion due to different air temperatures (causing different densities). • Warmer air rises through colder air – this is the first part of convection • When air cools, it sinks. • This creates a cycle, or convection cell

  10. Air convection

  11. Orographic Lifting • 2) Orographic lifting: land features like mountains force air upward • Wind blows toward a mountain, the ground forces it up to higher elevation

  12. Orographic Uplift

  13. Frontal Wedge • 3) Frontal wedging: a front is a transition between air masses (temperature and/or humidity). Cold air wedges its way under less dense warm air, forcing it up

  14. Frontal wedging

  15. Convergence • 4) Convergence: where 2 air masses meet head to head and have nowhere to go but up

  16. Convergence

  17. 4 Ways Air is Lifted • 1) Convection: air motion due to different air temperatures (causing different densities). • 2) Orographic lifting: land features like mountains force air upward • 3) Frontal wedging: a front is a transition between air masses (temperature and/or humidity). Cold air wedges its way under less dense warm air, forcing it up • 4) Convergence: where 2 air masses meet head to head and have nowhere to go but up

  18. 4 types of air masses • 1) Continental: warm, dry air masses formed over land • 2) Maritime: cold, humid air masses that form over ocean • 3) Polar: really cold, dry air masses that form at high latitudes • 4) Tropical: warm, wet air masses that form at low latitudes

  19. What is a front? • Front - transition zone between 2 different air masses • One air mass is a big body of air with the same temperature and humidity (moisture content)

  20. The edge of a front

  21. Warm and cold fronts

  22. Front convergence • If colder air advances while warmer air retreats, it is called a cold front (blue triangles)

  23. Cold Front

  24. Warm front • If warm humid air advances and cold drier air retreats, it’s called a warm front – red ½ circles

  25. Warm Front

  26. 4 Front Types

  27. Thunderstorm Development • Basically, T-storms are caused by rising humid air along either a warm or cold front. • The greater the temperature differences, the more quickly the storm forms • T-storms are rather short lived; usually the cycle lasts an hour or less

  28. 3 parts to a T-storm • 1) Cumulus: is when cumulus clouds build upwards and laterally. Rising air expands and cools accordingly. Cooling causes condensation (formation of water droplets)

  29. Eventually cumulonimbus clouds form.

  30. 2) Mature • Once precipitation (hail, snow, rain) occurs, the storm is in the mature phase

  31. Falling rain drags air downwards causing a downdraft • During the mature phase, precipitation is heaviest, lightning and hail prevalent, and tornadoes may even occur.

  32. 3) Dissipation • Is when the precipitation starts to end, clouds shrink and severe weather decreases.

  33. Formation – rising air • Mature – precipitation/bad weather • Dissipation – clouds disappear

  34. ??? • Why is that storm going in a circle? Wind blows in a straight line…

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