Three ways clouds form (teach)


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Describes three ways that clouds are formed.

I placed a short video clip in this slide show and would like to have someone confirm that it plays. If anyone downloads this show, pleas let me know if the convection video plays as you go through the show.

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Three ways clouds form (teach)

  1. 1. How Warm Moist Air is Lifted to Form Cloudsis Lifted to How Warm Moist Air Form Clouds By Moira Whitehouse PhDFree clip art
  2. 2. Clouds form when warm moist air is liftedand cooled. Previously we said that thislifting action for the water cycle wasprovided by convection. Here we willlook at all three ways that air is liftedand cooled to form clouds: Convection Mountain lifting Air Mass movement
  3. 3. We really need to understand two thingsfor this “cloud making” lesson to makesense.First, the temperature of the air goes downas the elevation gets higher. Roughly, forevery 1000 feet we go up the temperaturegets about 2 degrees F cooler.Second, the temperature of the airdetermines how much water vapor(molecules of water in the gaseous form) theair can hold. Warmer air holds more water.
  4. 4. 1. Convection In cold air the molecules are closer together and the air is therefore, more dense and heavier than warm air. Because it is heavier, gravity pulls harder on cold air which then forces the lighter warm air up and out of its way. As a result, the warmer air is pushed up (lifted) into cooler zones above the surface.
  5. 5. Following is a simple demonstration ofconvection where a candle is used to heatthe air and a piece of burning rope is usedto show the air’s movement. Notice that air over the candle rises and is replaced by cool air coming down the other chimney.Note: There is a short video on the next slide after the still shot(Quicktime may be required to view the video).
  6. 6. Quick time
  7. 7. In our world, the Sun’s heat replaces thecandle, heating the ground which heats the warm moist air allowing it to be pushed up by the cooler air. As the warm air goes up it gets cooled. Cool air cannot hold as much water vapor as warm air. As the warm moist air is cooled, the vapor changes totiny droplets of liquid, the stuff of clouds.
  8. 8. 2. Mountain lifting When warm moist air meets a mountain, it is pushed upward into cooler temperatures by the slope of the mountain itself. As this warm, moist air moves up the mountain, it is cooled and cannot hold as much water vapor. Once again, the vapor changes into tiny droplets; exactly what is needed to make a cloud.
  9. 9. As wind or air mass movement pushes thiswarm moist air toward the mountain, the slope of the mountain forces it up into higher cooler air.In this cooler environment, the air justcan’t hold as much water vapor, andclouds are formed as the vapor changes toliquid droplets.
  10. 10. 3. Air Mass movement Clouds formed because of air mass lifting are pretty much like clouds formed by mountains, except that the lifting is forced by another mass of air instead of the mountain. Air mass lifting can occur with both warm and cold front movement but it is always the warm air that gets lifted.
  11. 11. When a cool air mass moves into a mass ofwarm moist air, the mass of warm air isquickly forced up and thundercloudsdevelop. Thunderstorms often occur.
  12. 12. When a warm air mass moves into a massof cold air, it slides over top of the cold air,is cooled and stratus clouds form. Agentler longer rain often follows.
  13. 13. In order for these clouds to form, watervapor had be lifted up into the colder atmosphere. Can you remember the three ways they might have been lifted?