Living in Arkansas, we've all experienced the familiar phenomenon known as weather fronts. Whether it be a cold front sweeping in, giving us a blustery northerly wind, or a warm front accompanied by a gusty southerly wind. When two air masses meet, weather can change quickly. Sometimes fronts are weak, others not so weak, leading to significant weather differences. Our science experiment today will cover the aspect of two air masses meeting, specifically a cold and warm air mass.
As portrayed in the graphic above, a warm air mass is currently in place over the mid-south. A cold front is quickly sweeping from the west, northwest, due to a strong area of low pressure. What happens when these two air masses finally encounter? Cold air is much more dense than warm air, as the colder air undercuts the warm air, the warmer less dense air will begin to rise. This lifting motion is responsible for cloudy, rainy, and even stormy weather. A hot-air balloon is able to rise due to this interaction of air. Warmer air will continue to rise so long as the air surrounding it is colder, or more dense.
So how do we put this into view, and illustrate this with a science experiment? For this experiment you will need a few things:
- Rectangular glass tank-does not have to be very large
- Two cups
- Plastic insert for the glass tank
- Access to water (warm and cold)
- Instant Coffee grounds
For this experiment place your glass tank on a level surface. Fill this glass tank up with tap water, and let the water set in room temperature for 15 minutes or so. Take your plastic insert and place it in the middle, effectively separating the water inside the tank into two sections. Next, you'll need your cups, fill one cup with hot water and the other with cold water. Take the instant coffee grounds and pour them in your cup of cold water.
Pour the hot and cold water into their own respective sections inside the glass tank. Let the water set for a couple of seconds, and then remove the plastic insert. Watch as the warmer water begins to slowly override the colder water. The colder water will slowly begin to undercut the warmer water before both ultimately mixing together. The motion of fronts in the real atmosphere is complicated and effects which are not included in this simple experiment come into play. This includes earth's rotation/Coriolis effect, and many other factors.
We have included a video example of this experiment below, courtesy of Met Office (Youtube). We hope you enjoyed this simple and easy experiment, have fun!
-AW Team
