CH 6 – Air Pressure and Winds

Atmospheric Pressure

Weight of the air above a certain altitude.

Mercury Barometer

An instrument that measures atmospheric pressure using the height of mercury in a tube.

Aneroid Barometer

A device that reacts to changes in atmospheric pressure without using liquid.

Isobars

Lines on a weather map that connect points of equal atmospheric pressure.

Coriolis Effect

The apparent deflection of moving objects caused by the Earth's rotation.

Pressure Gradient Force (PGF)

The force that causes wind to move from high pressure to low pressure.

Geostrophic Wind

Winds that blow parallel to isobars in the upper atmosphere, unaffected by friction.

Buys Ballot's Law

States that in the Northern Hemisphere, low pressure is to the left and high pressure is to the right when standing with your back to the wind.

Prevailing Wind

Wind that consistently blows from a particular direction.

Sea Breeze

A wind that blows from the sea to the land, typically occurring during the day.

Land Breeze

A wind that blows from the land to the sea, typically occurring at night.

Hydraulic Pressure

Pressure exerted by a fluid in a confined space.

Horizontal Pressure Gradient

The difference in pressure that occurs along the same horizontal line.

Upper Atmosphere Pressure

Pressure systems that exist higher in the atmosphere influencing weather patterns.

Ridges and Troughs

Ridges are associated with high pressure and warm, dry air; troughs are associated with low pressure and cool, wet weather.

Wind Vane

A device used to measure wind direction.

Cup Anemometer

An instrument used to measure wind speed.

Radar Altimeter

An instrument that determines height above the ground by measuring distance to the surface.

Wind Sock

A type of weather instrument used to estimate wind speed and direction.

Density

Mass per unit volume; important in understanding temperature vs pressure relationships.

Air Mass

A large body of air with uniform temperature and humidity characteristics.