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To better understand Hadley circulation, a tank experiment was set up to mimic these atmospheric conditions in a controlled environment. A metal container filled with ice was placed in the center of a slowly rotating circular tank. The low rotation rate, 1.28 RPM, and correspondingly low Rossby number (f = 2Ω) was chosen to replicate the low latitude regions where the Hadley Cell forms. Five thermometers (labelled A through E) were placed on the outside of the ice bucket and along the sides and bottom of the plastic tank, in order to measure the generated temperature gradient.
Surface Flow:
Particle tracking software was used to track the motion of paper dots on the surface of the water, in order to determine how velocity varied as a function of distance. The tracks of the five particles studied, along with the plot of their velocities (in meters per millisecond) as a function of distance from the center of the tank, are included below. These surface flows in the tank correspond to the trade winds on Earth.
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This relationship relates the fluid horizontal speed in the tank to the tank’s rotation rate and temperature gradient. By plugging in the calculated value for the ∂T/∂r term into this thermal wind relation, we can try to approximate the velocity at the bottom of the tank. Integrating both sides of the equation, we find:
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