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Glossary of Terms
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| Acid rain |
Rain which is acidic as a result of pollution |
| Air pressure |
The weight of the air in the atmosphere pressing down
on the Earth |
| Anemometer |
An instrument that measures the speed or force of the
wind |
| Atmosphere |
The layer of air that surrounds the Earth and is held
there by the pull of the |
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Earth's gravity. It is made up of various gases,
mainly nitrogen and oxygen |
| Axis |
An imaginary line about which the Earth spins every 24
hours |
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| Barometer |
An instrument that measures air pressure |
| Beaufort scale |
A scale of numbers representing different wind speeds
and a description of their |
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effects on land or sea. It was invented by
Admiral Beaufort in the early 19th |
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century. |
| Blizzard |
A winter storm with strong winds and heavy snow |
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| Climate |
The usual pattern of weather in a particular place |
| Compressed air |
Air which has been squeezed into a small space |
| Condense |
To change from a gas or vapour to a liquid, through
cooling |
| Cyclone |
The name for a tropical storm originating in the
Indian Ocean |
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| Depression |
An area of low pressure |
| Drought |
A prolonged period with very little or no rain |
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| Equator |
An imaginary line around the Earth midway between the
North and South Poles |
| Evaporation |
The process by which a liquid becomes a gas due to
heating |
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| Forecast |
Something that tells us what the weather is going to
be like |
| Front |
The boundary between two masses of air with different
temperatures (ie: a mass of cold air and a mass of warm air) |
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| Glacier |
A slow-moving mass of ice and snow |
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| Hail |
Pieces of ice that sometimes form in high clouds |
| High Pressure |
A mass of air that presses down strongly on the
surface of the Earth because it is being cooled and is therefore more dense |
| Humidity |
The amount of water vapour held in the air |
| Hurricane |
A violent, spiralling storm that forms over the
Atlantic Ocean, with winds over 120 kph |
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| Ice Age |
A period approximately 18,000 years ago when ice
covered a large part of the Earth's surface |
| Isobar |
A line on a weather map linking areas with equal air
pressure |
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| Low Pressure |
A mass of air that presses down only weakly on the
surface of the Earth because it is being warmed and it therefore less dense |
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| Millibar |
A unit used to measure atmospheric pressure |
| Monsoon |
A seasonal wind that brings rain to many places of the
world, for example India and Southern Asia |
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| Occluded Front |
An area where warm air is pushed upwards as a cold
front overtakes a warm front and pushes underneath it |
| Orbit |
The path of the Earth around the sun, or of satellites
around the Earth |
| Ozone |
The gas found in the stratosphere that protects us
from the Sun's harmful ultra-violet (UV) radiation |
| Ozone Layer |
A layer of air in the atmosphere that contains a
relatively high concentration of the gas ozone |
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| Pressure Centre |
A region of high or low pressure |
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| Radiation |
A wave of energy sent across space. Examples
include heat and light energy |
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| Satellite |
Device that circles high above the Earth and can be
used for monitoring the weather |
| Stevenson Screen |
A white box with ventilated sides that is used to
house weather instruments and protect them from direct sunlight |
| Stratosphere |
The second layer in the atmosphere above the Earth's
surface. It extends up to 50 km and contains the ozone layer |
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| Temperature |
A measure of how hot or cold something is |
| Thermometer |
An instrument for measuring the temperature of
something, for example the air |
| Tornado |
A funnel-shaped whirlwind which extends to the ground
from storm clouds |
| Tropics |
An area on the Earth's surface that lies between 30º
north and 30º south of the equator |
| Troposphere |
The lowest region of the atmosphere in which all the
Earth's weather takes place |
| Typhoon |
The name for a tropical storm originating in the
Pacific Ocean, usually the China Sea |
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| Ultra-violet Radiation |
The radiation found in the Sun's rays beyond the
violet part of the visible spectrum. It can be harmful to both plant and animal life |
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| Vapour |
The gaseous form of a substance that is normally a
liquid, for example water vapour |
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| Wind |
A moving mass of air. The movement of the air
causes the weather |
| Wind Vane |
An instrument for showing wind direction |
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