Barometer — Science definition
An instrument that measures air pressure, useful for tracking whether weather is likely to clear or worsen.
Where it is taught
- Air Masses, Fronts & Pressure — Atmosphere & Weather, Earth & Space Science, Grade 9
In use
Fronts don't wander on their own — they're steered by patterns of air pressure, the weight of the atmosphere pressing down on a given spot, which we measure with a barometer.
Air Masses, Fronts & Pressure
Questions using barometer
Problem 1
Standard sea-level air pressure is about 1013 millibars. A barometer reading of 998 millibars most likely signals...
- A low-pressure system, with cloudier, stormier weather ahead
- A high-pressure system, with clear, calm weather ahead
- No change in the weather at all
- A broken barometer
Answer and explanation
A low-pressure system, with cloudier, stormier weather ahead
A reading well below the roughly 1013-millibar average indicates lower-than-average pressure, which is associated with rising air and increasing clouds or storms.