Barometric pressure

Barometric pressure is also referred to as 'atmospheric pressure' and refers to the absolute pressure of air in a given location / time.

Air pressure in the atmosphere varies with temperature, location, winds, local and global weather systems... Basically, a whole bunch of things.

To measure barometric pressure, a barometer is used. This often compares the pressure in the air to an absolute vacuum, by method of a pressure gauge or a column of mercury.

Units of atmospheric pressure tend to be in mmHg (read directly from a mercury barometer) or hectopascals (hPa). 1 hPa = 100 Pa. The Pascal (Pa) is the SI Unit for pressure, and 1 hPa = 100 Pa.

Air pressure at sea level is generally around 1000 +- 50 hPa.

In dealing with fluid dynamics involving air, barometric pressure is important in determining absolute pressure from gauge pressure.