Atmospheric Pressure and Wind
In the previous two modules, you learned that temperature and precipitation have varied considerably over the past 4.6 billion years of our changing Earth, and that they are also agents of that change. The third agent of change in the atmospheric system is wind, the force that moves and distributes energy and water across the globe.
Why do we have wind? How does it develop and why dies it strengthen or weaken? This module addresses the global and local processes that create wind and how the combination of wind, temperature, and precipitation form weather systems at regional to global scales.
To understand wind, you first need to understand pressure. And to understand pressure, you need to watch this cool science experiment. You are HIGHLY encouraged to try this at home (taking all necessary safety precautions, of course).
Why do we have wind? How does it develop and why dies it strengthen or weaken? This module addresses the global and local processes that create wind and how the combination of wind, temperature, and precipitation form weather systems at regional to global scales.
To understand wind, you first need to understand pressure. And to understand pressure, you need to watch this cool science experiment. You are HIGHLY encouraged to try this at home (taking all necessary safety precautions, of course).
WHAT IS GOING ON IN THIS VIDEO?
What caused the can to crush when it hit the water?
Why did the can fill with water when it came in contact with the water in the bowl?
What effect did the heating have on the air inside the can?
What caused the can to crush when it hit the water?
Why did the can fill with water when it came in contact with the water in the bowl?
What effect did the heating have on the air inside the can?
If you want to impress your friends (or make some fast cash), bet them you can crush a can without actually touching it. Then hand them the tongs! What to do:
Why did the can crush itself? Remember that the density of water vapor molecules inside the can was very low. Outside of the can, the density of molecules (water vapor, oxygen, nitrogen, carbon dioxide, etc.) was much higher. This means that air pressure inside the can was lower than the air pressure outside the can, and while the top was right-side up it could try to equalize, but once it was sealed off in the water -- POP! The lower pressure inside the can gave way to the higher pressure pushing in from outside, and the can crushed inwards to equalize.
Air always moves from high to low pressure, and the greater the pressure differential, the faster air moves. Centers of high and low pressure across the globe thus dictate where winds are occurring and the strength of those winds. Log into BBLearn or the textbook resource website and in the Study Area for the textbook, select Interactive Animations. Under Chapter 5, watch the "Development of Wind Patterns" animation to begin learning about how winds form across pressure gradients.
- Add a small (only a few tablespoons) amount of water to an empty soda can.
- Place the soda can over an open flame or on a stover burner to heat the water. You want the water to begin vaporizing, so it needs to heat to near boiling.
- When you see the steam rising out of the can, you will know that the water vapor has completely filled the can, pushing out all other air molecules. Because it is heated, there is actually a low density of water vapor molecules inside the can relative to the air outside of it.
- Remove the can from the heat source and flip it over into a bowl of cold water so that the top of the can forms a seal with the water. POP!! It should instantly crush.
Why did the can crush itself? Remember that the density of water vapor molecules inside the can was very low. Outside of the can, the density of molecules (water vapor, oxygen, nitrogen, carbon dioxide, etc.) was much higher. This means that air pressure inside the can was lower than the air pressure outside the can, and while the top was right-side up it could try to equalize, but once it was sealed off in the water -- POP! The lower pressure inside the can gave way to the higher pressure pushing in from outside, and the can crushed inwards to equalize.
Air always moves from high to low pressure, and the greater the pressure differential, the faster air moves. Centers of high and low pressure across the globe thus dictate where winds are occurring and the strength of those winds. Log into BBLearn or the textbook resource website and in the Study Area for the textbook, select Interactive Animations. Under Chapter 5, watch the "Development of Wind Patterns" animation to begin learning about how winds form across pressure gradients.