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The following demonstration illustrates what happens when a warm air mass collides with and replaces a cold air mass. The cooking oil represents a warm air mass and the colored water represents cold air mass. Corn syrup was used in place of the water to slow down the interacting air masses. Activity 1. Cut the cardboard so that it forms a tight barrier between the right and left sides of the cooking dish. Wrap it with plastic wrap and seal the edges together as tight as possible. Place the barrier into the dish as shown in the drawing. 2. On the right side of the barrier, pour cooking oil into the dish so that it almost fills the right side. 3. On the left side of the barrier, pour water into the dish so that it almost fills the left side. Add a few drops of blue food dye to the water. 4. When the liquids appear calm, quickly lift the barrier and watch what happens. Closure Have the students describe what they saw happen. (The cooking oil rose above the colored water when the barrier was lifted.) Explain that the cooking oil was like a warm air mass and the water was the cold air mass. Oil is less dense than water, just as warm air is less dense than cold air. Thus, when the two air masses of different temperatures met, the warmer one rose over the colder one. Tell the students that on Earth, warm and cold air masses are in constant motion due to the winds, particularly those winds in the upper atmosphere. Explore

Cold air is more dense than warm air, so it moves faster. Cold air is more dense than warm air, so it moves faster. The frontal surface of a cold front is steep due to friction. The frontal surface of a cold front is steep due to friction. Cold fronts produce cumulus clouds and often heavy, short- Cold fronts produce cumulus clouds and often heavy, short- term precipitation. term precipitation. Typical ratio of vertical rise to horizontal distance is 1:50 Typical ratio of vertical rise to horizontal distance is 1:50 Explain (1)

Warm air moves slower because it is less dense than cold air. Warm air moves slower because it is less dense than cold air. Warm fronts have long, shallow-sloping frontal surfaces. Warm fronts have long, shallow-sloping frontal surfaces. Warm fronts produce stratus clouds and precipitation can last a Warm fronts produce stratus clouds and precipitation can last a very long time. very long time. Typical ratio of vertical rise to horizontal distance is 1:300 Typical ratio of vertical rise to horizontal distance is 1:300 Explain (2)

Cold and Warm Fronts with the Jet Stream Explain (3)

Cold Front Warm Front Explain (4)

1. Your plans for this weekend include seeing a movie and going to a picnic. Theres a warm front forecasted to come through on Saturday and then a cold front early Sunday morning. How would you schedule your weekend to reflect the approaching weather conditions? 2. In the distance you see very high cirrostratus clouds. Soon after, you see altostratus clouds rolling in. What type of weather can you expect over the next day or two? What types of clouds would you expect to see during this same time period? Elaborate

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