The weight of air pressing down on the earth is called the air pressure.
Air pressure is caused by the earth’s gravity, which acts like a downward force.
Pressure can be measured by a barometer and can be recorded by a barograph.
Pressure readings can be used to predict: storms,low pressure areas,
high pressure areas,weather fronts,and wind fields.
The barometer is the most useful weather forecasting tool for small vessels.
There are two types of barometers, mercury and aneroid.