Acid rainRain that is more
acidic than normal because water vapour has condensed ion to
particles of sulphate or nitrogen oxide.
Advection The transfer of some property (e.g.
temperature or moisture) by the horizontal movement of air
or water, such as wind or ocean current.
Advection fog Fog caused by the condensation
of water vapour when warm, moist air crosses cold ground or
sea.
Aerosol A suspension of microscopic liquid
and solid particles in the atmosphere for at least a few hours.
Can be natural or anthropogenic (man-made).
Air A naturally occurring mixture of gases,
chiefly nitrogen and oxygen with small amounts of argoin, carbon
dioxide and water vapour- we sometimes call this our atmosphere
Airmass A large area of air which has similar
temperature and humidity characteristics.
Air pressure The weight of the atmosphere
pressing down on the Earth’s surface as a result of gravity
Altitude The height of the something above
sea level. It is usually measured in feet or metres. Sea level
is an altitude of 0m.
Anemometer An instrument for measuring the
speed of wind
Anticyclone A large are of high atmospheric
pressure, characterised by outward-spiralling winds- a ‘high’.
In the northern hemisphere winds rotate around an anticyclone
in a clockwise direction.
Atmosphere A layer of air which covers the
earth.
Barometer An instrument for measuring atmospheric
pressure
Beaufort scale A scale that indicates wind
speed by the effect wind has on familiar objects.
Biofuel Any fuel (liquid, solid or gas) produced
from organic matter (matter from animals or plants).
Black ice Transparent ice forms when liquid
water freezes on the ground
Blizzard Blowing snow reduces surface visibility.
There are low temperatures, strong winds and heavy snow.
Celsius A scale of temperature based on one
introduced in 1742 by Celsius, a Swedish astronomer and physicist,
who divided the interval between the freezing and boiling points
of water into 100 parts. The present system, where the freezing
point is marked 0 and the boiling point is marked as 100, was
introduced by Christin Lyons in 1743.
Climate The long term (often taken as 30
years) average weather pattern of a region.
Cloud A structure formed in the atmosphere
by condensed water vapour.
Cold front The boundary between two different
air masses where the cold air pushes the warm air out of way
and brings colder weather.
Condensation The process by which water vapour
becomes liquid water.
Conduction The process of heat transfer through
materials by molecular motion.
Convection The process of heat transfer through
fluids by means of rising currents.
Corioilis force An effect caused by the Earth’s
rotation, which causes winds and currents to follow a curved
path across the Earth’s surface- to the right (clockwise) in
the northern hemisphere, to the left (anti-clockwise) in the
southern hemisphere.
Cyclone A large area of low atmospheric pressure,
characterised by inward-spiralling wind often called a ‘low’
or a ‘depression’. Also the name used for a hurricane in the
Indian Ocean and Western Pacific.
Depression A low-pressure weather system.
Dew Liquid water that has condensed on to
objects at or near the earth’s surface.
Dew point The temperature at which water
starts to condense out of a particular air mass.
Downburst A strong downdraught of short duration
produced by some thunderstorms.
Drizzle Very small droplets of liquid precipitation.
Evaporation The process where liquid water
turns into vapour (e.g. a rain puddle may evaporate into water
vapour when the sun comes out). It is the opposite of condensation.
Eye Centre of a hurricane
Fahrenheit A scale of temperature introduced
in about 1709 by the German Physicist, Fahrenheit, who was
the first to use mercury as a thermometric substance. Primary
fixed points were the temperatures of a mixture of common salt
and ice and the temperature of the human body; with reference
to these the freezing point of water was marked 32 degree and
the boiling point of water was marked 212 degrees.
Fog Water droplets in the air that reduced
visibility to less than 1000m (1100 yards).
Front The boundary between two air masses.
Frost White ice crystals deposited on the
surface of objects that have a temperature below the freezing
point of water.
Global warming The increase in global mean
temperature, which is believed to be linked to the artificial
increase in greenhouse gas concentrations.
Greenhouse gases Gases which absorb some
of the outgoing radiation from Earth and re-emit it back down
towards earth. Act as a kind of insulator.
Hail Pieces of hard, solid ice falling from
clouds.
Hemisphere One half of a sphere. The term
is usually applied to regions north or south of the equator.
High also known as an anticyclone- an area
of high pressure with a system of winds rotating outwards.
This usually means dry weather.
Humidity The amount of water vapour in the
air.
Hurricane A tropical revolving storm with
sustained wind speeds of more than 118km/h (73mph). It is called
a hurricane in the North Atlantic, but in other parts of the
world it is known as a typhoon or tropical cyclone.
Isobar A line on a map or chart that links
points of equal atmospheric pressure.
Jet stream A strong, high level wind that
can reach speeds in excess of 320km/h (200mph) – it is usually
around 5-10km (3-6 miles) above the ground.
Katabatic wind A wind which blows down a
slope.
Latitude Position on the Earth’s surface
north or south of the equator.
Lee The side of a mountain, hillside or
island what is facing away from the prevailing wind.
Lightning Discharge of static electricity
in the atmosphere, usually between the ground and a storm cloud.
Longitude Position on the Earth’s surface
east or west of the Greenwich meridian.
Low Also called a depression- this region
of low pressure can mean wet weather- it is the opposite of
high pressure or anticyclone.
Meteorologist Someone who makes a scientific
study of weather, weather processes and/or the climate.
Meteorology The science of the atmosphere-
meteorology embraces both weather and climate and is concerned
with all aspects of the Earth’s atmosphere (and those of the
planets) and with the interaction between the atmosphere and
the surface. The term was first used by Aristotle.
Millibar International unit for measuring
air pressure. Now a hectoPascal (hPa) is the standard unit
for pressure.
Monsoon The seasonal shift in wind direction
that brings alternate very wet and very dry seasons to India
and much of South-East Asia.
Occluded front The combination of warm and
cold fronts as a cold front overtakes a warm front. The front
develops during the later stage of the life cycle of a frontal
depression and is so called because of the associated occluding
(shutting off) the warm air from the Earth’s surface.
Precipitation Moisture that is released from
the atmosphere as rain, drizzle, hail, sleet or snow.
Radiation Process by which energy travels
across space.
Rainbow A rainbow appears when sunlight shines
through water droplets in the air. White light is made of seven
colours. As the light shines through the water droplets the
light is bent. The different colours of light bend by different
amounts, so they separate and become visible.
Sea-level The normal level of high tide,
used as a baseline for measuring height or depth.
Snowline The vertical limit of snow lying
on mountain side throughout the year.
Synoptic chart A map showing large-scale
weather patterns in an area at a given time.
Temperature: The heat content of the air.
Thunder Sound caused by intense heating of
the air by lightening.
Typhoon A name of Chinese origin, meaning
‘great wind’ applied to the intense tropical cyclones which
occur in the western Pacific Ocean. They are the same as the
hurricanes of the Atlantic Ocean and the cyclones of the Bay
of Bengal.
Warm front The boundary between two different
air masses where warm air pushes cold air away to bring warmer
weather.
Water vapour Water in its gas form. One of
the most important constituents
Weather The state of the atmosphere (with
regard to wind strength and direction, temperature, precipitation
and pressure) at a specific time and place.
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