Glossary
Air mass A large body of
air with relatively uniform characteristics such as temperature and humidity.
Altimeter A special
type of aneroid barometer used in airplanes to measure altitude.
Aneroid barometer A
device to measure air pressure that uses an aneroid, which is a sealed, flexible metal
bellows with some air removed that expands and contracts with air pressure changes.
Atmosphere The air
surrounding Earth.
Barograph A device for
recording air pressure.
Barometer A device for
measuring air pressure.
Blizzard Snow falling
with winds faster than 35 mph and visibility of 1/4 mile or less over an extended time.
Climate Average weather
of an area over a long time, usually 30 years.
Climate model
Mathematical model containing equations that describe climatic interactions.
Cold front A warm-cold
air boundary with the cold air advancing.
Condensation The change
of a vapor to liquid.
Conduction Transfer of
heat within a substance or from one substance to another by inter-molecular action.
Continental air mass An
air mass that forms over land, making it generally dry. It may be warm or cold.
Convection Transfer of
heat by the movement of the heated material. In meteorology, the up and down air motions
caused by heat.
Coriolis Effect The
apparent curving motion of anything, such as wind, caused by Earth's rotation. It was
first described in 1835 by French scientist Gustave-Gaspard Coriolis.
Cyclone An area of low
atmospheric pressure with winds blowing around it, counterclockwise in the Northern
Hemisphere, clockwise in the Southern Hemisphere.
Doppler radar Radar
that measures speed and direction of a moving object, such as wind.
Downburst Wind blasting
downward through the air. It may be due to a thunderstorm or shower.
Drizzle Falling water
drops with diameters less than .02 inch.
Drought Period of
abnormal dryness for a particular region.
Electromagnetic radiation Energy that moves in the form of disturbances in electrical and magnetic fields.
Light and radio waves are examples.
El Niño
Linked ocean and atmospheric events that have worldwide effects, characterized by warming
of water in the tropical Pacific from around the International Date Line to the coast of
Peru.
Extratropical cyclone A
large-scale weather system with a low-pressure center that forms outside the tropics.
Flash flood Flooding
with a rapid water rise.
Fog A cloud with its
base on the ground.
Fujita Scale A scale
created by Theodore Fujita for classifying tornadoes according to their rotational wind
speed and the damage they cause.
Funnel cloud A rotating
column of air extending from a cloud but not reaching the ground.
GOES Geostationary
Operational Environmental Satellite, a U.S. weather satellite in an orbit that keeps it
above the same place on the equator.
Gulf Stream A warm
ocean current that flows from the Gulf of Mexico across the Atlantic to the European
coast. It helps warm Western Europe.
Gust front The boundary
between cold air flowing downward out of a thunderstorm and the warmer air at the surface.
Its passage is similar to that of a strong cold front.
Hail Balls of ice that
grow in thunderstorm updrafts.
Heat lightning Glowing
flash in clouds. No thunder is heard because heat lightning is too far away.
High An area of
high-atmospheric pressure, also called an anticyclone.
Hurricane A tropical
cyclone with winds of 74 mph or more.
Hydrosphere Comprises
all the water on Earth.
Intertropical Convergence Zone The area near the equator called "The Doldrums" by sailors, where the
trade winds converge.
Inversion Stable air
condition in which air near the ground is cooler than air at a higher altitude.
Jet stream A narrow
band of wind in the upper atmosphere with speeds greater than 57 mph.
Latent heat Energy
stored when water evaporates into vapor or ice melts into liquid. It is released as heat
when water vapor condenses or water freezes.
Latitude The distance
on Earth's surface measured in degrees north and south of the equator.
Lightning A visible
discharge of electricity produced by a thunderstorm.
Longitude The distance
on Earth's surface measured in degrees east and west from the prime meridian.
Low An area of
low-atmospheric pressure.
Maritime air mass An
air mass that forms over an ocean, making it humid. It may be warm or cold.
Meridional flow A north
to south to north flow of high-altitude winds.
Mesocyclone A rotating,
upward moving column of air in a thunderstorm that can spawn tornadoes.
Mesoscale In
meteorology, weather systems and events up to about 250 miles across.
Meteorological bomb An
extratropical cyclone in which the center pressure drops an average of one millibar an
hour for 24 hours. Usually refers to storms off the U.S. East Coast.
Microburst A downburst
less than 2.5 miles in diameter.
Mid latitudes The
region of Earth between the polar and tropical regions, between latitudes 23.5 degrees and
66.5 degrees.
Millibar A metric unit
of air pressure measurement. The average atmospheric pressure at sea level is 1013
millibars.
Moist adiabatic lapse rate The variable rate at which rising air cools or sinking air warms when water is
changing phases in the air.
Monsoon Persistent,
widespread, winds that seasonally reverse directions. Usually summer winds from the ocean
bring rain, while winter winds from the land are dry.
Multicell storms
Thunderstorms consisting of clusters of single cell thunderstorms.
National Climatic Data Center (NCDC) The National Oceanic and Atmospheric Administration office in Asheville, NC,
that keeps climate records.
National Hurricane Center (NHC) National Weather Service office in Coral Gables, FL, that tracks and forecasts
hurricanes and other weather in the Atlantic, Gulf of Mexico, Caribbean Sea, and parts of
the Pacific.
National Meteorological Center (NMC) National Weather Service center in Camp Springs, MD, that prepares worldwide
computer forecasts. Hurricane and Severe Storms centers are part of NMC.
National Severe Storms Forecast Center National Weather Service center in Kansas City, MO, that issues watches for
severe thunderstorms and tornadoes across the nation.
National Severe Storms Laboratory (NSSL) National Oceanic and Atmospheric Administration Laboratory in Norman, OK, that
studies severe thunderstorms.
National Weather Service
Federal agency that observes and forecasts weather. Formerly the U.S. Weather Bureau, it
is part of the National Oceanic and Atmospheric Administration, which is part of the
Department of Commerce.
Numerical forecasting or prediction Use of computers to solve mathematical equations and produce weather forecasts.
100-year floods Water
levels that, on average, should occur once a century. This is the same as a water level
with a 100 to 1 chance of occurring in any single year.
Ozone Form of oxygen
with molecules that consist of three oxygen atoms compared to two atoms for ordinary
oxygen molecules.
Ozone hole Zone of
decreased ozone content that forms in the stratosphere over Antarctica each spring.
Prefrontal squall lines
Lines of thunderstorms ahead of an advancing cold front.
Pressure gradient force
Force acting on air caused by air pressure differences.
Rain Falling water
drops with a diameter greater than .02 inch.
Rainbow Arc or circle
of colored light caused by the refraction and reflection of light by water droplets.
Relative humidity The
ratio of the amount of water vapor actually in the air compared to the maximum amount of
water vapor the air can hold at its current temperature and pressure. This is expressed as
a percentage.
Ridge An elongated area
of high atmospheric pressure, running generally north-south, at the surface or aloft.
Saffir-Simpson Hurricane Damage Potential Scale A 1-5 scale, developed by Robert Simpson and Herbert Saffir that measures
hurricane intensity.
Sea breeze Winds
blowing inland from any body of water.
Severe thunderstorm A
thunderstorm with winds faster than 57 mph or hailstones 3/4 of an inch or larger in
diameter.
Short wave A bend, or
wave of wind, only tens of miles long, that moves along in the wind flow of the upper
atmosphere.
Solar energy The energy
produced by the sun.
Squall line A line of
thunderstorms.
Stable air Air in which
temperature and moisture discourage formation of updrafts and downdrafts. Clouds will be
low and flat Any precipitation will be steady.
Stationary front A
warm-cold air boundary with neither cold nor warm air advancing.
Storm surge Quickly
rising ocean water levels associated with hurricanes that can cause widespread flooding.
Storm tracks Paths that
storms generally follow.
Stratosphere The layer
of the atmosphere from about 7 to 30 miles up.
Supercell A fierce
thunderstorm that usually lasts several hours, often spinning out a series of strong tornadoes.
Synoptic scale
Large-scale weather events and systems, generally more than 200 miles across.
Thunder Sound produced
by a lightning discharge.
Thunderstorms Localized
storms that produce lightning, and therefore, thunder.
Tornado A strong,
rotating column of air extending from the base of a cumulonimbus cloud to the ground.
Trade winds
Global-scale winds in the tropics that blow generally toward the west in both hemispheres.
Transpiration Release
of water vapor into the air by plants.
Tropical cyclone A
low-pressure system in which the central core is warmer than the surrounding
atmosphere.
Tropical depression A
tropical cyclone with maximum sustained winds near the surface of less
than 39 mph.
Tropical disturbance
Rotary air circulation 160 to 300 kilometers across associated with a low pressure area over the tropical ocean.
Tropical storm A
tropical cyclone with 39 to 74 mph winds.
Tropics The region of
Earth between latitude 23.5 degrees north--the Tropic of Cancer--southward
across the equator to latitude 23.5 degrees south--the Tropic of Capricorn.
Tropopause The boundary
between the troposphere and the stratosphere.
Troposphere The lower
layer of the atmosphere, extending from the surface up to 7 or 8 miles above the earth.
Typhoon A tropical
cyclone with winds more than 75 mph and located in the north Pacific,
west of the international date line.
Warm Front A warm-cold
air boundary with warm air advancing.
Water Vapor Water in a
gaseous state.
[ Home ] [ Teacher Pages ] [ Modules & Activities ]
HTML code by Chris Kreger
Maintained by ETE Team
Last updated April 28, 2005
Some images © 2004 www.clipart.com
Privacy Statement and Copyright © 1997-2004 by Wheeling Jesuit University/NASA-supported Classroom of the Future. All rights reserved.
Center for Educational Technologies, Circuit Board/Apple graphic logo, and COTF Classroom of the Future logo are registered trademarks of Wheeling Jesuit University.