An anemometer is an instrument which measures the speed of wind. This instrument must be placed high above the ground and away from anything that can obstruct the flow of air. Even though there are several different types of anemometers, the Robinson Anemometer is the most commonly used because it works well under a great number of conditions. The wind speed is determined by the number of turns of the wheel in a certain length of time. The gas molecules found in the troposphere constantly move around causing air pressure.
Air pressure is the force of air against a unit of area.
This movement of air creates a push towards the earth. A great way to explain air pressure to children is by using a balloon as an example. When the air is blown into a balloon it will expand as far as the wall, or as far as the balloon will allow it to go. Air in the troposphere acts exactly like that inside the balloon. Air pressure is measured with an instrument called a barometer.