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It is possible to numerically verify the shear created by the Hadley cell by applying the thermal "wind" equation for water which varies in temperature,
Where α is the thermal coefficient of expansion of water and Ω is the rotation rate of the tank. By taking the temperature difference between the two bottom sensors (approximately 2K over 8cm), we may obtain a value for ΔT, which may be substituted into the thermal wind equation to calculate the expected shear, 2.45 m/s per meter. As the depth of the water in the tank was 9 cm, the speed of the rotation of the dots observed on the top of the water would be expected to be approximately 0.22 m/s.
Several particles were tracked on the surface of the tank. These tracks can be used to plot the azimuthal velocity of the dots relative to the distance from the center of rotation (as averaged over a one second period around a given point in time).
What is surprising about this plot is the order of magnitude difference of the observed velocities (about 0.5–1 cm/s) and the expected velocity of 22 cm/s. Although we did not measure temperatures throughout the water column, the difference of the bottom temperatures from the side-temperatures suggests that the cool temperatures are only observable in a thin layer very close to the bottom of the water column. Assuming a perfect adherence to the thermal wind equation, the height of the cool water would then be only 4 mm.