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Weather

Weather. Click HERE for Discovery Channel Guide to Extreme Weather (50 min). Weather -It’s what’s happening outside NOW!. Weather. All weather is a result of humidity, condensation and pressure. Water Cycle. Humidity—Water Vapor in the Air.

hayden-fulton
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Weather

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  1. Weather

  2. Click HERE forDiscovery ChannelGuide to Extreme Weather (50 min)

  3. Weather-It’s what’s happening outside NOW!

  4. Weather All weather is a result of humidity, condensation and pressure.

  5. Water Cycle

  6. Humidity—Water Vapor in the Air • Specific humidity: actual amount of water vapor in the air at a given time & place (grams of vapor per kilogram of air) • Warmer air can hold more water vapor

  7. Humidity Relative humidity: how close the air is to reaching its maximum capacity of water vapor • expressed as a percentage • 100% means it has reached maximum capacity

  8. Humidity Measured with a psychrometer A psychrometer has two thermometers to determine humidity. The dry bulb thermometer measures the room temperature, and wet bulb thermometer is wrapped in a wet cloth. Air is passed through the psychrometer to evaporate moisture on the wet bulb. The readings on the dry bulb thermometer and the wet bulb thermometer are then compared to determine the actual humidity.

  9. Condensation When water changes from a gas to a liquid • Dew point: the temperature at which the air becomes saturated with water vapor & condensation occurs • If air cools below the dew point, water starts condensing into a liquid, forming dew or cloud droplets

  10. Condensation • Fog & clouds form only when there are condensation nuclei (like dust particles) for the water to condense on • Air must cool below its dew point

  11. Condensation Nuclei

  12. NASA View of Windblown Sands off Coast of Africa

  13. NASA Views of Ash from Volcanic Eruption

  14. NASA Views of Smoke and Ash from California Fires

  15. Smog over LA from car exhaust

  16. Cloud Formation • When warm, wet air from the surface rises, it begins to cool. Eventually, the temperature drops to its dew point, and the water vapor can condense onto the condensation nuclei • Condensation level: the atmospheric level at which condensation occurs

  17. Warm air rises taking the water vapor along with it. Once it cools, it condenses forming a cloud.

  18. Cloud Types Classified by altitudeand shape

  19. Explain the process of cloud formation

  20. UFOs or what?What happened?

  21. Cloud Types Stratus: clouds that form inlayers Cirrus: high,featheryice clouds Cumulus: fluffyclouds with flat bases Nimbus: darkrainclouds

  22. Cloud types

  23. Precipitation Any form of water that falls from a cloud to Earth’s surface

  24. Types of Precipitation • Rain • Snow • Sleet: raindrops that refroze on their way to the surface • Freezing Rain: raindrops that only freeze when they hit the surface • Hail: when frozen raindrops are bounced up & down in the cloud until they fall in a huge ball of ice

  25. Types of Precipitation depend on the temperature of the atmosphere, both at the surface & on the way down snow sleet freezing rain

  26. Measuring Precipitation • Rain gauge: measures liquid precipitation • Measuring stick: measures frozen precipitation

  27. Where is Precipitation?

  28. Where is Precipitation? Rain Shadow effect: near a mountain range, the windward side gets lots of rain and the leeward side gets little/no rain – the rain shadow

  29. Explain the Rain Shadow Effect

  30. Extreme Weather1 minute video • http://science.discovery.com/videos/against-the-elements-mashups-devastating-winds.html

  31. Air Mass • A large body of air in the lower troposphere that has similar characteristics throughout • Temperature & humidity depend on origin and move with the air mass

  32. Types of Air Masses Continental: dryPolar: cold Maritime: wetTropical: warm • Continental polar (cP): cold & dry • Maritime polar (mP): cold & wet • Continental tropical (cT): warm & dry • Maritime tropical (mT): warm & wet

  33. Types of Air Masses

  34. Types of Air Masses

  35. Fronts—boundary between two air masses

  36. Fronts • Cold Front: boundary between advancing cold air mass & a warmer air mass it is displacing • Rising warm air usually produces precipitation if wet • Air becomes colder after front passes

  37. Fronts • Warm Front: boundary between advancing hot air mass & a colder air mass it is displacing • 1st clouds days in advance, then RAIN • Air becomes warmer after front passes

  38. Fronts • Occluded Front: when cold front ‘catches up’ to a warm front, producing clouds & precipitation

  39. Fronts Stationary front: when a front stops moving forward, producing clouds & precipitation – causes floods if stationary too long

  40. Station Model

  41. Surface Weather Map

  42. Locating a Front • Wind direction changes • Temperature changes sharply • Dew Point changes sharply

  43. Weather Forecasting • Satellites • Radiosondes • Surface observations

  44. Forecasting • Computer models take current data & plug it into equations to predict weather • Meteorologists take computer models & tweak them to fit their experience with local conditions

  45. Forecasting Trend Method: using past movement of a front & precipitation to predict future movement

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