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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.
Explain (1)
• Cold air is more dense than warm air, so it moves faster.
• The frontal surface of a cold front is steep due to friction.
• Cold fronts produce cumulus clouds and often heavy, shortterm precipitation.
• Typical ratio of vertical rise to horizontal distance is 1:50
Explain (2)
• Warm air moves slower because it is less dense than cold air.
• Warm fronts have long, shallow-sloping frontal surfaces.
• Warm fronts produce stratus clouds and precipitation can last a
very long time.
• Typical ratio of vertical rise to horizontal distance is 1:300
Explain (3)
Cold and Warm Fronts with the Jet Stream
Explain (4)
Cold Front
Warm Front
Elaborate
1.
Your plans for this weekend include seeing a movie and going
to a picnic. There’s 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?
Evaluate