BISMARCK, ND (KFYR) – Water and food coloring are all you need to do simple science experiments at home that explain how our atmosphere works with fronts, convection and thunderstorms! All of this is possible because the atmosphere is a fluid — it’s a mixture of gases that behaves like a liquid. Like water, the pressure at the bottom of the atmosphere near the ground is greater than the pressure near the top of the atmosphere. Fluids move in response to pressure differences, always flowing from high to low pressure. It is the same for the liquid as for the air in our atmosphere. Therefore, we can use water to represent our atmosphere and the different temperatures of this water to create movements and circulations.
Our first experiment will represent what weather fronts look like in 3D and how air density plays a role in our atmosphere.
You will need a fairly deep clear baking sheet (or clear storage container), a glass of ice cold water with blue food coloring and a glass of hot water with red food coloring . Fill the transparent tray with lukewarm water – something between the temperature of your ice water and your hot water.
Be prepared to simultaneously pour cold water on one side of the tray and hot water on the other side of the tray. Pour them in slowly and watch what happens when the two colors meet in the middle.
As the different water temperatures and their respective colors meet in the middle of the tray, you will notice that the cold water passes under the hot water. This sloping surface with cold, dense water at the bottom and warm, less dense water rising and over the colder water is a good example of a weather front.
As shown in the 3D cold front diagram below, a front is an inclined surface with dense cold air advancing undercutting less dense warm air, which is pushed higher into the atmosphere. This upward and upward movement of warm air is what forms the clouds, precipitation, and thunderstorms along these fronts.
A warm front is similar, but in this case warm air moves forward and slides over cooler, denser air. Usually with warm fronts, precipitation is more regular and more widespread than with cold fronts, although thunderstorms can also occur with warm fronts.
The main concept we learned from this simple science experiment is that cold air is denser than warm air (the same goes for our cold water and our warm water) and that weather fronts are sloping surfaces , cold air undermining warm air. This is why you see active weather, and sometimes severe weather, where areas of warm and cold air meet, usually along these fronts.
Our second simple science experiment will demonstrate convection in our atmosphere, which is the process that forms thunderstorms.
You will need the same fairly deep transparent baking tray (or transparent storage container), fill it with cool (but not too cold) water and place it over a few empty glasses, one at each corner. Next, fill another glass to the top with hot water and put some red food coloring in it. Slide this glass under the tray towards the center.
Place a few drops of blue food coloring on either side of the cold water tray and a few drops of red food coloring in the center of the tray, just above the glass of hot water that sits under the tray. The food coloring drops will start to sink to the bottom and scatter. You’ll have to be a little patient with this experience, but watch what happens carefully. As the hot water in the glass under the center of the tray heats the water in the center of the tray, the water and red food coloring will begin to rise to the surface as the water gets hotter and less dense than its surroundings. To replace the rising water, cooler water and blue food coloring sink to the bottom of the tray and move to the center. As this cooler water is drawn into the center of the tray, it is heated by the glass of hot water below, rises to the top, and the process continues. It’s a convection current, and it’s similar to the process that happens in our atmosphere.
Below is a close up of the food coloring rising from the bottom of the tray to the top of the tray above the heat source, which is the glass of hot water. Then the water and food coloring spread across the top of the tray, simulating the top of our atmosphere. Rising air forms clouds and thunderstorms, but these clouds can only reach a certain height before the top of our atmosphere extends to the tops of the clouds.
The convection current in our experiment will continue for a while, but the food coloring colors will start to mix over time. Be sure to check out all the cool things the different water colors and temperatures do in the tank!
Convection, which we demonstrated in this second experiment, is an important part of our atmospheric processes that form clouds and precipitation. It is a process that begins first with the radiation of the sun, which heats the ground. But the ground is heated unevenly across the world, so some regions end up being warmer than others. The warm ground then heats the air around it through the process of conduction. Then this warmer, less dense air rises in the process of convection. As warm air rises, it encounters cooler layers of the atmosphere which allow water vapor molecules to condense into clouds. And when the water droplets in the clouds combine, they become heavy enough to form raindrops. If the rising air, or updrafts, are strong enough, thunderstorms can form.
The convection current we demonstrated in our experiment translates into our atmosphere with warm air rising to form clouds, spreading out as it reaches the top of the atmosphere, and then warmer air cool flows around her. The cooler air near the ground warms and also begins to rise, increasing the size of the cloud as the warmer, humid air rises. This forms an essentially endless loop as long as the sun provides a heat source to warm the ground (which is similar to our glass of hot water under the shelf as a heat source in our experiment).
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