Why does barometric pressure change?

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bandmanjoe eNotes educator| Certified Educator

Barometric pressure is the sam thing as atmospheric pressure.  It is an indication of the amount of air pressure at that temperature per given unit of volume at sea level.  Barometric pressure is a major indicator in meteorlogy, the study and prediction of Earth's weather patterns.  The jet stream, the only global wind that has no stationary pattern and constantly changes, is a major influence in changing the barometric pressure across the Earth.

There are four types of air masses: continental polar, continental tropical, maritime polar, and tropical polar.  The continental part of the designation indicates the air mass formed over land and has lower water vapor content.  The maritime part indicates the air mass formed over water and has high water vapor content.  The tropical is an indication of a warm air mass, while a polar is an indication of a cold air mass.  Air masses tend to have high barometric pressure when of the cold type as opposed to the warm type.  They are more dense, meaning they have more air molecules packed together within the same unit of volume than do warm air masses.