A barograph is an instrument that makes a continuous graphical record of atmospheric pressure.
A barograph combines a barometer with a recording mechanism. In traditional models, a stack of partially evacuated metal capsules expands or contracts as air pressure changes. A linkage moves a pen across a rotating drum, producing a pressure trace over time.
Meteorologists use pressure records to identify approaching weather systems. A rapid fall often accompanies an approaching low-pressure system or strengthening storm, while rising pressure commonly follows the passage of a front. Modern automated weather stations usually store pressure digitally, but the term barograph remains standard.
A barometer gives a pressure reading, whereas a barograph records pressure continuously. An anemometer measures wind speed, a hygrometer measures humidity, and a ceilometer estimates cloud-base height.