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WeatherWise - Glossary |
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Acid Rain: |
Rain that is more acidic than normal precipitation because water vapour has condensed on to particles of sulphate or nitrogen oxide. |
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Adiabatic: |
Changes in temperature caused by the expansion (cooling) or compression (warming) of a body of air as it rises or descends in the atmosphere, with no exchange of heat with the surrounding air. |
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Advection: |
The transfer of heat by the horizontal movement of air or water, such as a warm wind or ocean current. |
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Advection Fog: |
Fog caused by the condensation of water vapour when warm, moist air crosses cold ground or sea. |
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Air: |
A naturally occurring mixture of gases, chiefly nitrogen and oxygen with small amounts of argon, carbon dioxide, and water vapour. Air also usually contains dust and pollen. |
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Air Mass: |
A large body of air with the fairly uniform temperature and humidity of its source region. |
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Air Pressure: |
The weight of the atmosphere pressing down on the Earth's surface. The effect is caused by gravity. Also called 'atmospheric pressure'. |
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Albedo: |
The measure of the reflectivity of a surface. |
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Anabatic: |
Rising, as when air moves up a hillside. |
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Anemometer: |
An instrument for measuring the force and speed of wind. |
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Angular Momentum: |
The energy of motion of a spinning body or mass of air or water. Its value depends on the mass of the body, its radius of spin, and its rate of spin. |
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Angular Velocity: |
The rate at which a spinning body, such as a planet, rotates. The Earth rotates at 15 degrees per hour, which is its angular velocity. |
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Anticyclone: |
A large area of high atmospheric pressure, characterised by outward-spiralling winds - a "high". |
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Atmosphere: |
A layer of gases surrounding a planet - on the Earth, chiefly made up of the gases Oxygen, Hydrogen and Nitrogen. |
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Atmospheric Pressure: |
The weight of the atmosphere pressing down on the Earth's surface. The effect is caused by gravity. Also called 'air pressure'. |
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Atoms: |
The smallest parts of an element - such as hydrogen or oxygen. |
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