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7. Glossary of Common Terms
TERM
DESCRIPTION
ABSOLUTE AIR PRESSURE
ABSOLUTE BAROMETRIC
PRESSURE
Absolute air pressure is the air pressure
registered on a barometer without regard to
altitude.
BAROMETER
A barometer is a device that measures the
pressure of the air pushing on it—this
measurement is called the barometric
pressure. We don’t actually feel the barometric
pressure because the air pressure is pushing
equally in every direction.
BEAUFORT (Bft)
An indicator of wind force strength (not speed)
as it would act on a ship’s sails. Still commonly
in used in some locales to indicate wind force.
DEW POINT
The temperature to which air must be cooled
to become saturated with water vapor. When
further cooled, the airborne water vapor will
condense to form liquid water (dew), or frost if
below freezing.
HEAT INDEX
The heat index (HI) or humiture is an index
that combines air temperature and relative
humidity, in shaded areas, as an attempt to
determine the human-perceived equivalent
temperature, as how hot it would feel if the
humidity were some other value in the shade.
HECTOPASCALS (hPa)
This is an international standard (SI system)
for measuring air pressure. It used to be
referred to as milli-bar (mb) and sometimes still
is. They are equivalent.
HYGROMETER
An instrument that measure relative humidity
of the air. This is expressed as a percentage
