Weather in a Tank
Why do some clouds have swirling, spiral patterns? How do garbage patches of plastic form in the ocean? You can learn about these phenomena and more with Weather in a Tank.
Earth Image (NASA): On September 4, 2019, a satellite image captured four tropical cyclones in the Atlantic Ocean.
Weather in a Tank is an apparatus with a tank of water on a rotating platform, and it can be used to perform rotating fluid experiments and demonstrations. It was developed at the Massachusetts Institute of Technology (MIT) and is used in university classrooms to help students understand how air and water circulate in the atmosphere and ocean, and different phenomena associated with rotating fluids.
At PRI, we use Weather in a Tank to run demonstrations about weather, climate, and ocean circulation for visitors in the Museum of the Earth.
Learn more about the wide range of experiments one can run with this apparatus on MIT’s Weather in a Tank page.
Acquisition of Weather in a Tank was funded by NSF Grant #1742178 to Professor Gang Chen (Department of Atmospheric and Oceanic Sciences, UCLA)
Weather in a Tank in the Museum of the Earth
Ocean Gyres and Plastic Pollution
By rotating a tank of water to simulate the rotation of the Earth, and setting up fans to simulate the trade winds and westerlies that blow across the Pacific Ocean, we can use Weather in a Tank to produce a vortex or gyre that is similar to what exists in the ocean.
Across the North Pacific, the trade winds and westerlies push on the surface ocean water, driving currents. These ocean currents are then deflected sideways from their direction of motion because of the Earth’s rotation, a phenomenon known as the Coriolis effect. The rotating currents are bounded by Asia to the west and North America to the east, and they are called gyres.
Plastic pollution—things like plastic bags, bottles, and containers—washes into creeks and rivers and eventually reaches the ocean, getting broken into smaller particles along the way. This plastic litter enters the ocean and breaks down even more, and gets trapped in the ocean’s gyres. The “garbage patches” you might have heard of are huge collections of small bits of plastic (microplastics) suspended in the water.
With Weather in a Tank and a set of two fans, the wind blown by the fans represents the trade winds and the westerlies. We sprinkle in bits of paper from the sides of the tank that don’t have fans attached, representing the western shores of North America and the eastern shores of Asia. The bits of paper represent plastic particles.
Monitor with camera image, from above the tank. The tank is not turning yet, and the bits of paper move around the edges of the tank, along with surface water currents created by the wind from the fans.
Now the tank is turning, and a gyre forms. The bits of paper have been pushed toward the center of the tank by the Coriolis force.
As the tank continues turning, the bits of paper get trapped in the center of the gyre.