Storm surge

Let's take a look!

What type of experiment is this?

Experimental procedure and explanation:

• During a typhoon or strong cyclone, a weather forecast may broadcast a “storm surge” warning. What is a storm surge?
• High waves and storm surges refer to distinct phenomena. A high wave is a tall wave that forms when the wind is strong, while a storm surge occurs when the air pressure drops near the center of a typhoon or cyclone, causing the sea level to rise throughout the surrounding area. When a strong typhoon strikes, the combination of strong winds generating high waves and low atmospheric pressure causing storm surges can lead to significant damage.
• Here, let’s try a storm surge experiment. Fill a cylindrical container with water and place a square board in the water to prevent the water from swirling. Vertically erect a straw and mark it to note the height.
• Use a hair dryer to blow air diagonally near the outer periphery of the cylinder to create a swirling flow (vortex) inside.
• In a vortex, the pressure is low at the center and high on the outer periphery, causing the water surface near the center to be pulled up by low-pressure air; more precisely, the outer surface of the water gets pushed upwards by the atmospheric pressure, and the surface of the water at the center gets pushed upwards because the pressure at the periphery is lower than that near the center. This same effect can be seen in a storm surge, where the water level rises due to the same phenomenon.
• This video of the experiment was produced with the support of JSPS KAKENHI 18K03956.

[Keywords]	Vortex, atmospheric pressure, typhoon
[Related items]	Free vortex and forced vortex、Remove a ball from a deep location 2
[Reference]	“The Wonders of Flow,” Japan Society of Mechanical Engineering, Kodansha Blue Backs, p. 52–59.

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