The General Circulation of the Atmosphere

Introduction

Tank Experiment

Two rotating tank experiments were set up. Tank rotation speed was the important parameter varied: one tank rotated at a speed of 1  $//<![CDATA[ \begin{array}{l}\mathrm{rad\,s^{-1}}\end{array} //]]>$ and the other at 0.1  $//<![CDATA[ \begin{array}{l}\mathrm{rad\,s^{-1}}\end{array} //]]>$. 

Slow Rotation Experiment

A metal canister of radius 12 $//<![CDATA[ \begin{array}{l}\mathrm{cm}\end{array} //]]>$ was placed in the center of a tank of radius 22  $//<![CDATA[ \begin{array}{l}\mathrm{cm}\end{array} //]]>$. Six HOBO temperature sensors were taped to the tank in the arrangement shown in the figure below. The thermometer cables were taped along the bottom and edge of the tank to minimize interference with water flow. The tank was filled with still water to a height of 12.6  $//<![CDATA[ \begin{array}{l}\mathrm{cm}\end{array} //]]>$.

The rotating table was spun up to 0.1  $//<![CDATA[ \begin{array}{l}\mathrm{rad\,s^{-1}}\end{array} //]]>$ and allowed to spin until a paper dot placed on the surface of the water appeared motionless to the overhead corotating camera, which was physically attached to the rotating table. The canister was filled with ice until full and then with water.

The surface speed of the water was measured by tracking black paper dots in the Particle Tracker application. The speed on the tank floor was measured by tracking the purple pigment trails from granules of potassium permanganate using timecoded screenshots in the Particle Tracker.  Water speed shear between the top and bottom of the tank was measured with drops of blue food dye. 

Fast Rotation Experiment

A metal canister of radius 18  $//<![CDATA[ \begin{array}{l}\mathrm{cm}\end{array} //]]>$ was placed in the center of a tank of radius 31 $//<![CDATA[ \begin{array}{l}\mathrm{cm}\end{array} //]]>$. Again six HOBO temperature sensors were taped to the tank in the arrangement shown in the figure below. The arrangement differs from the first experiment: thermometers 1 through 5 were placed in a line radially from the tank center; thermometer 6 was placed between 3 and 4, on the bottom of the tank but 10 $//<![CDATA[ \begin{array}{l}\mathrm{cm}\end{array} //]]>$ further in the clockwise direction. This arrangement was devised to capture thermal signatures of the eddies that were hypothesized to form. The speed of the corotating camera was synced electronically with the table rotation speed through a computer interface.