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The velocity data above can be compared with the thermal wind velocity prediction. Thermal wind relates wind speeds to temperature gradients. The most reliable place to measure a temperature gradient is along the base of the tank. The equation for thermal wind is:
∂u/∂z=gα/2Ω ∂T/∂r, 
for which α (the coefficient of thermal expansion) is 2.17*10-4 assuming that the average water temperature along the base of the tank is 21°C, g is 9.81 m/s2, and Ω is .101 rad/sec. The difference in temperature between the two sensors along the base was usually 2°, the distance apart was 8cm, and the depth of the water was 9cm. By plugging these values into the thermal wind equation, the predicted difference in speed between the surface and base of the water is 2.37cm/s. Because the temperature gradient chosen was between the two base sensors, this prediction is for the particle speed between those sensors (between 9 and 17 cm radius). The surface particle speeds observed were much smaller than 2.37cm/s, meaning that there was likely a significant clockwise flow at the base of the tank