Our planet – which includes us as
well as everything on the earth’s
surface – is surrounded by a layer of
air several kilometres thick. This layer
of air is known as the earth’s
atmosphere or, more simply, the
atmosphere. Gravity causes the
weight of this mass of air to exert
pressure on the earth’s surface.
The pressure generated is known as
atmospheric pressure or air pressure.
Our atmospheric conditions can also
be compared with conditions under
water. We live at the bottom of a “sea
of air”.
The gravitational force of the air above
us generates pressure which we call
air pressure.
At present, the official unit of
measurement for air pressure is hPa.
This abbreviation stands for
hectopascal (1 hPa = 1 mbar
On average, the air pressure at sea
level is 1,013.25 mbar. If we imagine
an air column with a cross-section
area of 1 m2, which extends from the
earth’s surface (sea level) to the
outermost edge of the atmosphere,
the air exerts pressure on this 1 m2 of
the earth’s surface with a mass
of 10,000 kg approx