Wind
Experiment 2

Creating "Wind" In a Bowl of Water

In this activity we will create an example wind circulation. This example can be used to demonstrate several concepts, however we will stick to only one.

Consider the beach on a hot summer day. The land and water warm at different rates. The land heats much more quickly and during the middle part of the day that air will rise. The ocean water however, will not warm much if at all during the day. Thus, there will be a contrast in temperature along the coast between warmer land temperatures and somewhat cooler ocean temperatures.

Rising air over the land will continue to rise until it reaches air that is warmer than it is, perhaps the Tropopause. Cool air from the upper atmosphere can sink all of the way to the surface of the Earth but we still have not found the breeze, or its direction.

Materials:
Ice
Water
Red food coloring
Blue food coloring
Hot plate (portable stove burner works very well)
Pyrex dish (rectangular bottom and deeper will work best)
2 or 3 hardback books (to use as a support, other objects will work)

Procedure:
Step 1: Turn on the hot plate
Step 2: Fill the pyrex dish with water until 2/3 full
Step 3: Place one end of the dish on the hot plate and the other end on a support to keep it level (towl, block, book or anything stable that will keep the dish level)
Step 4: The hot plate should now be heating the bottom of only one side of the dish
Step 5: Place a 2 or 3 ice cubes in the water on the opposite end of the dish from the hot plate
Step 6: Place Blue dye in the water around the ice cubes
Step 7: Place Red dye in the water above the hot plate
Step 8: Record your results

What you should see:
As the ice cubes cool the water on one side of the dish, the water will begin to sink. As the cool water reaches the bottom of the dish it can not go any lower and is forced to move toward the hot side (because it can not go through the bottom or side of the dish). Water warmed by the hot plate rises, when this warmer water reaches the top it can not go any further upward so it moves toward the cool side.

This circulation effect is represents how wind is created along a coastline. The rising and sinking also illustrates how parts of the atmosphere rise and fall due to the heating and cooling of air.

Question: If the warm side of the dish represents warm land in the afternoon and the cool side of the dish represents the ocean, which way would the wind be blowing on the beach?