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Glossary
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Absorbed
With reference to light: absorbed light is the fraction which is neither
reflected or transmitted.Sharpe (1990)
Active surface
The term active surface is used in the text to denote the general attributes
of any form of surface.
Aerosol
Colloidal substance, either natural or manmade, that is suspended in the
air because the small size (0.01–10 µm) of its particles makes
them fall slowly. Aerosols in the troposphere are usually removed by precipitation
and their residence time is measured in days or weeks. Aerosols that are
carried into the stratosphere usually remain there much longer Allaby
& Allaby. (1990).
Albedo
The ratio (usually expressed as a percentage) between the quantity of
radiation falling on to a surface, and the amount that is reflected. For
certain surfaces, notably water, the albedo varies greatly depending on
the angle of incidence. Dunlop (2001).
Altitude
Height above sea level. Chambers (1994)
Anthropogenic
Applied to substances, processes, etc. of human origin, or that result
from human activity. Allaby & Allaby (1990).
Anticyclone
An area of high pressure around which the wind blows clockwise in the
northern hemisphere and counter-clockwise in the southern hemisphere.
Also called a high. Ahrens (1994)
Atmosphere
The gaseous envelope surrounding planets. The term is generally applied
to the whole body of terrestrial air. The Earth's atmosphere is composed
mainly of nitrogen, oxygen, argon and carbon dioxide.
Atmospheric Lapse Rate
Rate of decease of temperature per unit height in the atmosphere. In the
troposphere the average rate is approximately 6.5oC per 1000m. Allaby
and Allaby (1990)
Aurora
Illumination of the sky, somtimes in brilliant colours, as a result of
high-speed solar particlesentering the ionosphere. Called ‘aurora
borealis’ or ‘northern lights’ in the northern hemisphere,
and ‘aurora australis’ or ‘southern lights’ in
the southern hemisphere. Allaby and Allaby (1990)
Biosphere
The zone of air, land, and water (both in lakes and in the sea) at the
surface of the Earth that is occupied by organisms.
Black bodies
Perfect absorbers of radiation.
Carbon
The basic element of organic life which, together with hydrogen and oxygen,
forms the fundamental molecules involved in organic structures.
Carbon cycle
The cycling of carbon in nature. Carbon dioxide is produced when plants
and animals respire and is consumed by green plants during photosynthesis.
Carbon dioxide also dissolves in the oceans and precipitates as limestone
or dolomite.
Carbon dioxide
A colourless, odourless gas at normal temperatures, composed of one atom
of carbon and two of oxygen. It makes up about 0.03% of the atmosphere
by weight. Carbon dioxide is consumed in photosynthesis by green plants
and produced by the respiration of plants and animals and the burning
of fossil fuel.
Chemical reactivity
The tendency for two or more reactants to engage in a chemical reaction,
forming a new product or products.
Chlorofluorocarbons
(Also referred to as CFCs) Gases whose molecules contain chlorine, fluorine
and carbon. They have been used as propellants in spray cans and as foaming
agents for polystyrene, and are still widely used as refrigerants. They
are implicated in both ozone destruction and global warming. ReVelle and
ReVelle (1992)
Climatic climax
A relatively stable, long-lasting ecosystem which is established after
a successional series, usually best suited to the climate of the area.
Comet
A small body composed of meteoric dust and frozen ice in a highly elliptical
or parabolic orbit around the Sun.Allaby and Allaby (1990)
Condensation nuclei
Tiny particles upon whose surfaces condensation of water vapour begins
in the atmosphere. Ahrens (1994)
Conduction
The transfer of heat from points of higher temperature to those of lower
temperature through the collision of atoms or molecules that possess a
high kinetic energy (energy of motion) with those of lesser energy. Dunlop
(2001).
Convection
The process whereby heat is transferred from one part of a liquid or gas
to another, by movement of the fluid itself. Mayhew (1997)
Coriolis Force
An apparent force acting on moving objects that results from the Earth’s
rotation. It causes the objects in motion, and oceanic and atmospheric
currents, to be deflected to the right in the northern hemisphere and
to the left in the southern hemisphere. The force varies from zero at
the equator to a maximum at the poles. Allaby and Allaby (1990)
Cosmic rays
Ionizing radiation from space, comprised principally of protons and alpha
particles (helium nuclei). Allaby and Allaby (1990)
Cumulonimbus
An exceptionally dense and vertically developed cloud, often with a top
in the shape of an anvil. The cloud is frequently accompanied by heavy
showers, lightning, thunder and sometimes hail. It is also known as a
‘thunderstorm cloud’. Ahrens (1994)
Cyclones
Systems of winds blowing spirally inwards towards a centre of low pressue.
(See anticyclone) Chambers (1994)
Diurnal
Happening daily, or during the course of a day. Chambers (1994).
Doldrums
The oceanic equatorial zone, which has low pressure and light, variable
winds. The zone moves seasonally north and south of the equator. Allaby
and Allaby (1990)
Eccentricity
The variation in the shape of the ellipsoid orbit of the Earth around
the sun.
Ecosystem
A specific biological community and its physical environment interacting
in an exchange of matter and energy.
Einstein
A unit of radient energy. One mole of photons. Sharpe (1990)
Electrons
The smallest particle carrying a negative charge. Electrons are normally
encountered orbiting the nucleus of an atom.
Ellipse
An oval shape. With reference to Earth’s orbit around the sun: the
orbit describes an oval shape, and is therefore further away from, or
closer to, the sun, depending on its position on the ellipse.
Energy barrier
The energy barrier is the amount of energy required to enable certain
reactions to occur.
Equatorial Trough
An elongated area of low pressure where the trade winds converge. Also
known as the Intertropical Convergence Zone (ITCZ). Ahrens (1994)
Erosion
The process of wearing away the land surface, by processes which transport
rock debris. Erosion frequently refers to the loss of soil due to wind
or as a result of washing away by water.
Exosphere
The outer region of the upper atmosphere, extending from a base of 500
- 750 km altitude. The zone has a very low concentration of gases which
can escape into space. The exosphere forms part of the magnetosphere.
Fossil fuel
A fuel derived from the remains of ancient plant or animal life. The main
forms used are oil, gas and coal.
Free oxygen
Oxygen which is not chemically combined with other elements.
Freshwater
Water in the global hydrological cycle which has a low content of dissolved
solids (less than 1gl-1), as is found in most rivers, lakes and as ice.
Front
The transition zone between two distinct air masses. Ahrens (1994)
Gamma-rays
Electromagnetic radiation of very short wavelengths emitted from atomic
nuclei.
Geological erosion
See Erosion
Global warming
This term refers to the increase in the Earth's mean atmospheric temperature
and is associated with periodic variations in the Earth's orbit, ice agesand
atmospheric composition. In recent years the focus of attention and research
has been upon the effects of pollution and fossil fuel use on this cyclicity.
Greenhouse effect
The absorption and re-radiation of terrestrial infrared radiation by atmospheric
water vapour, carbon dioxide and ozone. The greenhouse effect suggests
the Earth will undergo a warming trend as carbon dioxide from fossil fuel
combustion and other heat trapping gases accumulate in the atmosphere.
A notable argument has arisen as to the importance of the role this effect
will play in global climatic change and warming.
Greenhouse gases
The effect of heat retention in the lower atmosphere as a result of absorption
and re-radiation by clouds and gases (e.g. water vapour, carbon dioxide,
methane and CFCs). Allaby and Allaby (1990)
Hadley cell
A thermal circulation proposed by George Hadley to explain the movement
of the trade winds. It consists of rising air near the equator and sinking
air near 30o latitude. Ahrens (1994)
Halocarbons
Compounds that contain carbon and halogen atoms and (sometimes) hydrogen.
Chlorofluorocarbons (CFCs) contain carbon, chlorine, and fluorine. Similar
to these are hydrochlorofluorocarbons (HCFCs), which contain carbon, chlorine,
fluorine, and hydrogen, and the hydrofluorocarbons (HFCs), which contain
carbon, fluorine, and hydrogen. The halons are a class of halocarbons
that contain bromine. Daintith (2000).
Horse Latitudes
Subtropical latitudes coinciding with a major anticyclonic belt; they
are characterized by generally settled weather and light or moderate winds.
Allaby and Allaby (1990)
Hurricane
A severe tropical cyclone having winds in excess of 74 miles per hour.
Ahrens (1994)
Hydrological cycle
The circulation of water - in liquid, solid, or vapour form - through
a series of reservoirs in the environment.
Hydrosphere
The total body of water of the Earth, i.e. the oceans, rivers, lakes,
underground and atmospheric water.
Hygroscopic
Readily absorbing moisture. Chambers (1994)
Hygroscopic nucleus
A microscopic particle (e.g. of sulfur dioxide, salt, dust, or smoke)
in the free air, on to which water vapour may condense to form droplets.
Allaby (1994).
Infra-red Radiation
Radiation of frequency less than about 1013 per second. It is invisible
to the human eye. Heat-seeking and night-viewing devices rely on detection
of infra-red radiation. Sharp (1990)
Ionosphere
The part of the atmosphere that lies above 80 km altitude, with the highest
concentrations of ions and free electrons. This allows radio waves to
be transmitted around the curved surface of the Earth. Allaby and Allaby
(1990)
Intertropical Convergence Zone (ITCZ)
See Equatorial Trough.
Jet streams
Relatively strong winds concentrated within a narrow band in the atmosphere,
near the tropopause. Ahrens (1994)
Kinetic energy (symbol K)
Energy that an object possesses because it is in motion. Chambers (1994).
Latitude
Parallels of latitude are imaginary circles drawn round the earth parallel
to the equator. The parallels are numbered according to the angle formed
between a line from the line of latitude to the centre of the earth and
a line from the centre of the earth to the equator. Those regions lying
within the Arctic and Antarctic circles, having values of 66.5° to
90° are termed high latitudes. Low latitudes lie between 23.5°
north and south of the equator, i.e. within the tropics. Mid-latitudes,
also known as temperate latitudes lie between the two. Mayhew (1997)
Laws of Thermodynamics
Thermodynamics is concerned with the study of the transformation of energy,
in particular its transformation into work and vice versa. The basic priciples
are embodied in the three Laws. Atkins (1992)
Long-wave radiation
With reference to the greenhouse effect: The infrared energy emitted by
the Earth and the atmosphere. Ahrens (1994)
Magnetosphere
The region around the Earth in which the Earth’s magnetic field
plays a dominant part in controlling the physical processes that take
place.Ahrens (1994)
Meridional
A type of atmospheric circulation pattern in which the north-south component
of the wind is pronounced. Ahrens (1994)
Mesosphere
Upper-atmospheric layer above the stratopause (at 50 km) through which
temperature decreases with height up to about 80 km, where temperature
reaches a minimum of about -90oC. Allaby and Allaby (1990)
Meteorites
Small, extraterrestrial bodies, most of which probably originate in the
asteroid belt, that enter the Earth’s atmosphere and land on the
surface. Most are only a few centimetres in size. Allaby and Allaby (1990)
Meteorology
The study of weather and climate patterns.
Methane
A colourless, odourless gas. It is the chief constituent of natural gas
and occurs in coal mines and landfill sites. Sharp (1990)
Milankovitch theory
An explanation for changes in the seasons which result from changes in
the earth's orbit around the sun.
Mole
A mole is 6 x 1023 free atoms or molecules. It is a chemical measure of
an amount of substance which allows for all substances to be measured
against a scale of relative atomic masses: the standard is the oxygen
atom for which 1 mole = 16.00grams.
Molecule
A molecule is composed of two or more bonded atoms. Molecules are converted
into other molecules during chemical reactions by breaking chemical bonds
between atoms: new chemical bonds between different atoms are usually
formed to create the product of a chemical reaction.
Noctilucent
With reference to clouds: luminous night clouds, occuring at 80-85 km
altitude, near the upper limit of the stratosphere, characterized by a
blue to yellow hue. They are seen on summer nights at latitudes between
about 50 and 65 in both northern and southern hemispheres. Allaby and
Allaby (1990)
Oblique axis of rotation
With reference to the Earth: Rotation which is not parallel to the vertical.Chambers
(1994)
Oblique radiation
With reference to the Earth: radiation from the sun which strikes the
Earth at an angle which is not perpendicular to the Earth’s surface.
Obliquity
The angle between the plane of the Earth’s orbit and that of its
equator.Chambers (1994)
Orbital parameters
See Eccentricity, Obliquity,
Precession and Tilt.
Oxygen (O)
A gas without taste, colour or smell, forming part of the air, water,
etc., supporting most forms of life and also necessary for combustion.
(Atomic number 8; symbol O). Chambers (1994)
Ozone (O3)
A highly reactive molecule formed from three oxygen atoms (O3).
In the lower atmosphere it forms a dangerous pollutant but in the stratosphere
(upper atmosphere) ozone is essential for the continuation of life of
Earth because it forms an ultraviolet absorbing shield which is needed
to protect the biosphere from mutagenic radiation. Most atmospheric ozone
forms at altitudes that are between 15 and 36 kilometers, when oxygen
absorbs ultravoilet radiation (UV).In the longer wavelength region of
the uiltraviolet radiation band, which is called UV-B, absorption by oxygen
and ozone is only partial and is very sensitive to changes in ozone concentration.
UV-B radiation is responsible for sunburn and either causes or contributes
to skin cancer. Hence the concern about 'holes' or changes in the concentration
of the ozone layer.
Photon
A quantum of light or other electromagnetic radiation. Chambers (1994)
Photon Theory
A theory in which radiation is described as a stream of small packages
of energy, rather than a wave. It is used to explain certain phenomena
which cannot be explained by the wave theory. (See Wave Theory).
Photosphere
The visible surface of the sun. The average temperature of the photosphere
is 6000K.
Photosynthesis
The process by which green plants convert light energy into chemical energy
(food), through the use of chlorophyll. The main chemical components are
water and carbon dioxide.
Planck’s Constant
The constant (h) relating to the energy and frequency of radiation. It
has a value of 6.6256 * 1034 JHz-1. Sharp (1990)
Polar front
The main boundary line between polar and tropical air masses along which
depressions develop in mid-latitudes, especially over the oceans.Allaby
and Allaby (1990)
Potential energy
Type of energy an object possesses because of its vertical position in
the Earth's gravitational field; also the energy stored in a system. Chambers
(1994).
Precession
The action of a couple whose axis is perpendicular to the rotational axis
(a torque) on a rotating body causing its axis of rotation to trace out
a path about an average position, instead of having a constant alignment,
i.e. the axis of rotation itself revolves conically about a central point.
The Earth's axis of rotation precesses as a result of several forces,
e.g. changes in mass distribution on its surface, changes in the gravitational
field due to changes in the relative positions of the Moon, Sun, and planets,
etc. Allaby & Allaby (1990).
Precipitation
With reference to the water cycle: Rain, hail, snow etc. Chambers (1994)
Primary productivity
The rate at which biomass is produced by photosynthetic and chemosynthetic
autotrophs (mainly green plants) in the form of organic substances. Allaby
(1994)
Productivity
The rate or efficiency of production of a given thing e.g. biomass.Chambers
(1994)
Products
With referenct to a chemical reaction: Substances obtained from others
by chemical change. Chambers (1994)
Protons
The nucleus of an atom is composed of protons and neutrons. The main characteristic
of the proton is that it carries a positive electrical charge, conventionally
ascribed the value of +1.
Reactants
Substances taking part in a chemical reaction. Chambers (1994)
Respiration
The breakdown of chemicals (food) through oxidation to release energy
for life. The main components of the reaction are water, oxygen and sugars.
Note that nearly all living organisms respire, plants as well as animals.
Rossby Waves
Named after the Swedish-American meteorologist C.G. Rossby. The waves
are in the major belt of westerlies characterized by a long length (typically
2000 km) and significant amplitude. Allaby and Allaby (1990) Ahrens (1994)
Short-wave radiation
Most often used to describe the radiant energy emitted from the sun in
the visible and ultraviolet wavelengths. Ahrens (1994)
Solar constant
The mean intensity of the solar beam in free space (i.e. before penetrating
the Earth’s atmosphere) at the average distance of the Earth from
the sun. The intensity is not strictly constant for all the wavelengths
of radiation involved. The amount of variability is still a subject of
debate, but is certainly very small. Allaby and Allaby (1990)
Solar radiation
The radiation emitted by the sun. Normally refers to the radiation incoming
to the top of the Earth's atmosphere.
Spectrum
Any analagous range of radiation in order of wavelength. Chambers (1994)
Spin axis
A line about which a body rotates. Chambers (1994)
Squall line
A line of thunderstorms that form along a cold front, or out ahead of
it.Ahrens (1994)
Stochastic
Random, or affected by chance. Chambers (1994).
Stratopause
The level that marks the maximum height of the stratosphere, at around
50 km. After high temperatures in the upper stratosphere (about 0oC at
the stratopause) temperature decreases with increasing altitude in the
mesosphere above. Allaby and Allaby (1990)
Stratosphere
The atmospheric layer above the troposphere, which extends from about
10 to 50 km above the Earth’s surface. The stratosphere is a major
stable layer whose base is marked by the tropopause, and where temperatures
overall average approximately -60oC. Allaby and Allaby (1990)
Sub-tropical highs
A semi-permanent high in the sub-tropical high-pressure belt centred near
300 latitude. The ‘Bermuda high’ is located over the Atlantic
Ocean off the east coast of North America. The ‘Pacific high’
is located off the west coast of North America. Ahrens (1994)
Temperature inversion
An increase in air temperature with height. Ahrens (1994)
Thermal equilibrium
With reference to the Earth: the incoming heat from the sun equals the
outgoing heat radiation.
Thermonuclear reactions
Reactions transforming one nucleus into that of a different element by
fission or fusion. These are the reactions that occur in a nuclear reactor.
Thermosphere
The upper zone of the atmosphere, above about 80km, where solar radiation
of the shortest wavlengths is absorbed. In this zone, which includes the
ionosphere, temperature increases with height, but because of the very
low atmospheric density there, the heat capacity is minute.Allaby and
Allaby (1990)
Thunderstorm
A storm of fairly local scale in which strongly developed cumulonimbus
cloud produces thunder and lightning, usually with rain and strong, gusting
wind, and often with hail. Allaby and Allaby (1990)
Tilt
See Oblique Axis of Rotation.
Tornadoes
Intense, rotating columns of air that protrude from cumulonimbus clouds
in the shape of a funnel or a rope, whose circulation is present on the
ground.Ahrens (1994)
Trade winds
The winds that occupy most of the tropics and blow from the sub-tropical
highs to the equatorial low. Ahrens (1994)
Tropical Cyclone
See Cyclone
Tropical storms
Organised thunderstorms with a cyclonic wind circulation between 35 and
64 knots. Ahrens (1994)
Tropopause
The boundary separating a lower layer of the atmosphere in which air temperature
generally decreases with height (troposphere), from the layer above, in
which temperature remains constant or increases with height (stratosphere).
Allaby and Allaby (1990)
Troposphere
The layer of the atmosphere between the Earth’s surface and the
tropopause, about 10km above the ground, within which the air temperature
on average decreases with height at a rate of about 6.50C/km.Allaby and
Allaby (1990)
Typhoon
Tropical cyclone of great force which occurs in the western Pacific Ocean.Allaby
and Allaby (1990)
Ultraviolet (UV) Radiation
The ultraviolet spectral region lies at shorter wavelengths than the visible
region. Ultraviolet radiation is characterised by having a wavelength
below 400 nanometres.
Van Allen Belts
Two belts of high energy, charged particles, trapped by the Earth’s
magnetic field within the magnetosphere. The inner belt starts at an altitude
of about 800 km and reaches a maximum intensity at about 2,000km. The
outer belt reaches a maximum intensity at between three and four Earth
radii (18,000 - 25,000 km). Allaby and Allaby (1990)
Velocity
Rate of motion (distance per unit time) in a stated direction. Chambers
(1994)
Visible light
Electromagnetic radiation which can be detected by the eye.Chambers (1994)
Visible region
Refer to visible light
Water vapour
A suspension of water, as a liquid, in air. Water vapour is not the gaseous
form of water since that would be steam.
Wave Theory
A theory of the nature of radiation: radiation and light are regarded
as a travelling wave created by an oscillating electric field. The wavelength,
(usually given by the Greek symbol lambda) is the minimum repeating distance).
Wavelength
The distance between two successive similar points on an alternating wave,
e.g. between successive maxima or successive minima. Chambers (1994)
Westerlies
The dominant westerly winds that blow in the middle latitudes on the poleward
side of the subtropical high pressure areas. Ahrens (1994)
White bodies
Perfect reflectors of radiation (see Black Bodies).
X-rays
Electromagnetic radiation of wave length approximately 1 angstrom (10-10m).
Sharp (1990)
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