Glossary
Acid Rain – Rain or precipitation that is acidic due to pollution. Oxides of sulphur and nitrogen mix with water vapour in the atmosphere to become an acid.
Air Mass – A large body of air covering much of a continent or ocean in which the temperature, surface pressure and humidity are fairly constant.
Air pressure – The force of air pressing down on Earth, measured in millibars (mb)
Atmosphere – The layer of gases surrounding the Earth, stretching about 1,000 km (600 miles) into space. All weather takes place in the lowest layer.
Barometer – Device used to measure atmospheric pressure.
Carbon sink – The concept of carbon sinks is based on the natural ability of trees, other plants and the soil to soak up carbon dioxide and temporarily store the carbon in wood, roots, leaves and the soil.
Coal – A hard black or brown sedimentary rock formed by the decomposition of plant material, widely used as fuel.
Climate – The normal pattern of weather conditions in a particular place or region, averaged over a long period of time.
Clouds – Masses of condensed water vapour and ice particles floating in the sky. Ten types of cloud have been categorized, all based on three basic cloud forms: cumulus, stratus and cirrus.
Cloud cover – The amount of sky seen to be covered by cloud in any given place.
Cold front – A boundary at the head of a cold air mass.
Condensation – The change from a gas, such as water vapour, to a liquid, such as water.
Coriolis effect – The effect caused by the Earth’s spinning, which makes winds and currents follow a curved path across the Earth’s surface.
Depression – Another term for an area of low pressure, or cyclone.
Dew point – The temperature at which water vapour turns back into liquid.
Emissions trading – Emissions trading is a market-based scheme for environmental improvement that allows parties to buy and sell permits for emissions or credits for reductions. Emissions trading schemes are now operating in many countries and across a range of pollutants.
Fossil Fuel – Any carbon-containing fuel, e.g. coal, peat, petroleum, and natural gas derived from the decomposed remains of prehistoric plants and animals.
Front – The boundary between two air masses with different basic characteristics. Fronts can be warm, cold or occluded.
Geothermal energy – Heat energy from underground rocks, used to generate electricity by heating water to steam, which turns turbines.
Global Warming – A long-term increase in the temperature of the atmosphere, possibly caused by the greenhouse effect.
Greenhouse Effect – The warming up of the Earth’s surface, caused by radiation from the sun being trapped by gases in the lower atmosphere, just as heat is trapped in a greenhouse by the glass roof.
Hemisphere – Half of the Earth. There are northern and southern hemispheres.
Humidity – The amount of water vapour that is in the air.
Hydrosphere – A collective name for all the water on and around Earth.
LEDC – Is a less economically developed country (poorer or less wealthy). Most of the poorer countries (LEDCs) are in the Tropics and the Southern Hemisphere.
Ice – Frozen form of water. Ice has a specific gravity (0.91666) that is slightly less than water. This difference in specific gravity causes ice to float on water.
Ice Cap – Large dome-shaped glacier found covering a large expanse of land. Smaller than an ice sheet.
Isobar – A line on a weather map connecting points of equal atmospheric pressure.
LNG – Liquefied natural gas is a natural gas that has been processed to remove impurities and heavy hydrocarbons and then condensed into a liquid at atmospheric pressure by cooling it to approximately -160º C. LNG is transported by specially designed vessels and stored in specially designed tanks.
LPG – Liquefied petroleum gas is a mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles, and increasingly replacing fluorocarbons as an aerosol propellant and a refrigerant to reduce damage to the ozone layer. LPG is widely used as a “green” fuel for internal combustion engines as it decreases exhaust emissions.
MEDC – Is a more economically developed country (more wealthy). Most of the richer countries (MEDCs) are in the Northern hemisphere (apart from Australia and New Zealand).
Meteorology – The scientific study of weather, both in the atmosphere and at the surface of the Earth.
Microclimate – A climate within a very small area.
Natural resources – Can be classified as renewable or non-renewable. Renewable resources will not run out: wind, sun etc. Non-renewable are finite: coal, oil, natural gas etc.
Occluded front – A type of front created by a warm front and a cold front joining together.
Oceanic Ridge – A submarine mountain system found in all of the oceans; it is composed of volcanic rock (mostly basalt) and displays features produced by tension.
Okta – A measurement of cloud cover, with 8 oktas being the highest.
Ozone Layer – A thin layer of ozone gas in the upper atmosphere that filters out harmful ultraviolet radiation from the Sun before it reaches the Earth.
Polar air mass – A cold air mass that forms in polar areas.
Precipitation – All forms of water that fall to the ground or form on or near it, such as rain, snow, dew and fog.
Prevailing winds – The most frequent direction of winds in any given area.
Solar panels – Smooth flat panels which gather energy from the Sun.
Solar radiation or solar energy – Radiation from the Sun, made up of high-energy ultraviolet rays, visible light and low-energy infrared rays.
Storm – Strong winds, between gale and hurricane force, of 103 –121 kph (64-75 mph), which uproot trees and overturn cars.
Synoptic chart - A chart drawn up by meteorologists, containing detailed information about the weather in the form of symbols.
The Kyoto Agreement – Drawn up in 1997, is an attempt on the part of the world community to reduce emissions of carbon dioxide as a first step towards addressing the problem of global warming.
Thermal – A rising current of warm air.
Trade winds – Winds which blow in the Tropics, normally from east to west.
Typhoon – A tropical cyclone that occurs over the Pacific Ocean.
Warm front – A boundary at the head of a warm air mass.
Weathering – The physical, chemical, and biological processes by which rock is broken down into smaller pieces.
Wind Chill – The sensation that the air temperature is lower than it really is because of the effect of the wind.