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Weather Words - G
-- G --
Gales of November: High winds (usually accompanied by rain and snow) that
sweep the Great Lakes in November (the peak of the Great Lakes storm season)
in association with intense low pressure systems traversing the Upper
Midwest.
Galloping Gertie: The Tacoma-Narrows Bridge, a 5,939-foot suspension bridge
across Puget Sound at Tacoma, Washington. Four months after opening, 40
m.p.h. winds caused the evenly-spaced spans of the bridge to sway
increasingly violently until it collapsed on Nov. 7, 1940.
Gegenschein: The round or elongated area of light seen in the night sky
along the zodiac (the plane defined by the Earth's orbit around the sun).
Rarely observable in cities because of background city lights.
General circulation: The patterns of permanent or semi-permanent large-scale
motions within the Earth's atmosphere (trade winds, the prevailing
westerlies, etc.); also called global circulation.
Geography: The science of the Earth and its life -- especially the
description of land, sea, air and the distribution of plant and animal life
(including man), with reference to the mutual relations among those diverse
elements.
Geology: The scientific study of the Earth, including its composition,
structure, physical properties and history.
Geonephelococcygia: Seeing clouds whose shapes are reminiscent of the
geographical features on maps. The word was coined in 2000 by Jim Hill, a
popular Chicago radio and television personality from the 1960s into the
1990s.
Geophysics: The physics of the Earth and its environment: the interior of
the Earth, its surface and atmosphere and, by extension, the physical nature
of the universe.
George Shot: The world's first thermonuclear explosion, detonated by the
United States on May 8 in 1951, at Eniwetok Atoll in the South Pacific
Ocean.
George Washington's Hurricane: Originating near Bermuda on July 19, 1788,the
hurricane passed directly over Lower Chesapeake Bay and Mount Vernon,
Va.,the home of George Washington, on the 23rd. George Washington wrote in
his diary that the center of a hurricane passed directly over his Mount
Vernon, Virginia, estate on July 23, 1788.
Geosmin: A musky-smelling chemical found in the soil that helps to produce
the familiar smell of rain. When air pressure falls, as it often does when
it rains, the soil literally exhales and geosmin escapes into the air.
Geostrophic: Referring to an exact balance between the Coriolis force and
the pressure gradient force, two important influences that determine the
strength and direction of the wind.
Geosynchronous: A term applied to an equatorial satellite with an orbital
velocity equal to the rotational velocity of the Earth. The satellite thus
appears stationary to an observer on the ground.
Geosynchronous orbit: The orbit of a satellite traveling west to east above
the Equator with a speed matching that of the Earth's rotation, thereby
remaining stationary in relation to the Earth. Such an orbit has an altitude
of about 22,300 miles.
Ghibli: (1) A hot, dust-bearing desert wind in the Saharan region of north
Africa.
Ghibli: (2) In Libya, the name given to foehn winds (warm, dry winds blowing
downslope on the lee (downwind) slopes of a mountain range). In the United
States and Canada, foehn winds are known as chinooks.
Glacial: Characterized or dominated by the existence of glaciers; extremely
cold, icy; having the appearance of ice.
Glaciation: In meteorology, the transformation of cloud particles from water
droplets to ice crystals. The anvil-shaped upper portion of a thunderhead
(cumulonimbus cloud) consists of ice crystals and is said to be GLACIATED.
Glacier: A mass of land ice that is flowing slowly (at present or in the
past) from an accumulation area to an area of dissipation. A flowing glacier
is termed active; a glacier that has ceased to flow is termed stagnant.
Glacier fire: A strong reflection of sunlight from an icy surface causing
the surface to appear as if it were on fire, occurring mainly when the sun
is low in the sky.
Glaciers, disappearing: The glaciers in Glacier National Park, Mont., are
melting. In 2007, 27 glaciers exist in the park, down from 150 in 1900, and
90 percent of the ice volume is gone.
Glaciology: The study of snow and ice on the Earth's surface, with emphasis
on the causes and modes of ice accumulation and movement.
Glaze: A coating of ice, usually clear and smooth, formed on exposed objects
by the freezing of rain, drizzle, or (rarely in the Chicago area) fog. The
accumulation of glaze in sufficient thickness constitutes an ice storm.
Global mean sea level: It has been rising at an average rate of about 0.06
inch per year over the past 100 years. That amounts to a rise of six inches
during the 20th Century.
Global warming: (1) The term refers, without any implications for the cause
or magnitude, to the observation that the atmosphere near the Earth's
surface is growing warmer.
Global warming: (2) All aspects of the planetary warming problem, including
potential climatic changes that will be brought about by an increase in
global temperatures. The scientific community is in agreement that the
Earth's average surface temperature has risen about 1 degree F during the
last century, but there is disagreement on the causes for that warming or
the amount of additional warming that will occur.
Global warming and cooling: The natural planetary warming and cooling
trends that the Earth has experienced all through its history. We're in a
warming phase now, up 11 degrees F during the last 12,000 years, but the
rate of warming has greatly increased since the Industrial Revolution and
that accelerated rate of warming is apparently due to human activity.
Globe lightning: A rare form of lightning consisting of a luminous ball,
often reddish in color, about one foot in diameter, which may move rapidly
along solid objects or remain floating in mid-air. Also known as ball
lightning.
Gloomy: In reference to the weather, a period of cloudy, dark, foggy, damp
or rainy weather that is especially depressing to the spirit. Not a
technical meteorological term.
Glory: Small, faintly colored rings of light centered around a bright object
seen through a mist; also, the same phenomenon seen in mist at a point in
the sky directly opposite the sun.
Gouverneur, NY, snowburst: On Oct. 18, 1930, a massive early-season
lake-effect snowstorm swept off Lake Ontario and buried Gouverneur (50 miles
northeast of the east tip of the lake) under 47 inches of snow.
Gradient: In meteorology, the change in the value of an atmospheric variable
per unit of horizontal distance, as in temperature gradient or air pressure
gradient.
Grassland: An large area (such as the prairies of the Great Plains) of grass
or grasslike vegetation, generally receiving 10 to 30 inches of
precipitation annually. (Chicago's annual precipitation: 36 inches).
Graupel: White, opaque, approximately round precipitation particles,
typically 0.1 to 0.2 inch in diameter. They are crisp and easily crushed,
and bounce when they land on a hard surface. Graupel is sometimes mistaken
for hail.
Gravity: The force of attraction imparted by the Earth on a mass which is at
rest relative to the Earth. During every second of fall, the speed of a body
freely falling in a vacuum in Earth's gravity will increase by 32 feet per
second.
Gravity wind: The general name for the gravity-induced downslope flow of
relatively cold air. Gravity winds usually develop in mountainous or hilly
terrain toward sunset.
Great Lakes: Combined, the five Great Lakes (Superior, Michigan, Huron,
Ontario and Erie) contain 90 percent of fresh water in the United States and
20 percent of the world's fresh water.
Great Lakes shipwrecks, causes of: 58 percent from storms; 22 percent from
on-board fire; 8 percent from sinking (not weather-related); 7 percent from
collisions; 3 percent from strandings; 2 percent from other causes.
Great Lakes summertime weather effect: The surface water of the Great Lakes,
cool relative to air temperatures during the summer, strengthens high
pressure systems that move across the Lakes Region.
Great Lakes winter weather effect: The water of the Great Lakes, warm
relative to air temperatures during the winter, adds heat to the air and
strengthens low pressure systems that move across the Lakes Region.
Great London smog disaster: From Dec. 4-10, 1952, damp air, gray skies, no
wind and a powerful inversion sealed London in a toxic mix of pollutants
from power plants, coal stoves and the city's new fleet of 8,000 diesel
buses. The toxic air brought death to 12,000 Londoners.
Great Miami Hurricane: On Sept. 18, 1926, the hurricane lashed Miami with
138 m.p.h. winds and a 12-foot storm surge, and it claimed 135 lives in the
city (214 elsewhere). The storm's eye passed directly over the city. On
Sept. 20, the same hurricane blasted Pensacola, Fla., with 152 m.p.h. wind
gusts.
Great New England Hurricane of 1938: On Sept. 21, 1938, a category 3
hurricane, moving in excess of 50 m.p.h., swept north across Long Island
with 120 m.p.h. winds, claiming 600 lives in New England.
Great Salt Lake, Utah: It generates lake-effect snow, occasionally 20 inches
or more, especially when moist air from the lake is lifted as it blows over
mountains and highlands surrounding the lake.
Green flash: As the sun is setting (or rising), the last (or first) glimpse
of sunlight will be seen as brilliant green for 2-3 seconds. The phenomenon
requires a very clear atmosphere and is rarely seen.
Greenhouse effect: The heating effect of the Earth's atmosphere upon the
planet. Sunlight readily passes through the atmosphere and warms the
surface, but the atmosphere retards the escape of heat back into space. The
atmosphere acts like a greenhouse because sunlight freely passes through it
and warms the surface, but the Earth's re-radiated heat is retarded in its
escape from the planet back into space. Without the greenhouse effect, the
temperature of the Earth's surface would average about 0 degrees F instead
of the present 61 degrees. If the greenhouse effect strengthens, the Earth's
surface warms.
Greenhouse gases: Those gases in the Earth's atmosphere that absorb
appreciable terrestrial radiation and retard the escape of the planet's heat
into space. The main greenhouse gas is water vapor, but others are carbon
dioxide, ozone, methane and nitrous oxide.
Greenland: The Earth's largest island, 85 percent of which is covered by an
ice sheet averaging 5,000 feet thick. If melted, ocean levels would rise
about 21 feet; highest temperature 78 degrees F; lowest temperature -87.
Greenland ice sheet: It averages 5,000 feet thick and covers 700,000 square
miles of Greenland. If it totally melted, ocean levels would rise about 21
feet.
Greenland's lowest temperature: -87 degrees F on January 9, 1954 at Northice
(located near the center of Greenland). The reading was taken during the
British North Greenland Expedition.
Greenwich time: Time as reckoned from the zero meridian of Greenwich,
England. To each hour in advance of, or behind, Greenwich time there
corresponds a difference of 15 degrees longitude east or west of the
Greenwich meridian.
Gross precipitation: The amount of precipitation measured in the open;
precipitation that is not intercepted by vegetation like trees or grass.
Large, dense trees can intercept up to 0.30" of rain. Routine precipitation
reports are in terms of gross precipitation.
Ground blizzard: Blizzard conditions (winds 35 m.p.h. or higher and
visibility below 1/4 mile for at least three hours) caused solely by blowing
and drifting snow in the absence of new, falling snow. Ground blizzards
occur most often in the Great Plains.
Ground burst: A nuclear explosion at ground level. The area affected is
relatively limited compared to an air burst, but the amount of radioactive
fallout is increased.
Ground clutter: The pattern of radar echoes from fixed ground targets
(buildings, trees, hills, etc.) near a radar. This kind of clutter masks or
hides the echoes returned from nearby precipitation targets.
Ground fog: A type of fog that is shallow and usually results from nighttime
radiational cooling of the air. It does not extend up to the base of any
clouds that may lie above, and it does not obscure the entire sky.
Ground stop: A type of airport delay during which planes at an airport are
not allowed to depart, sometimes for hours, if they are bound for
destinations experiencing bad weather.
Ground water: Water in the earth that supplies wells; water below the water
table, as distinguished from soil moisture above the water table; subsurface
water that lies within the zone of saturated ground.
Groundhog Day: American folklore that the state of the sky on February 2
(mid-point between the winter solstice and spring equinox) is a weather
predictor: if cloudy (and therefore no shadows), milder; if sunny
(shadowed), another six weeks of winter. Embodied now with Punxsutawney
Phil, the Pennsylvania groundhog whose accuracy is only 39 percent.
Ground-level ozone: Ozone that occurs near the surface of the Earth. It is a
pollutant of concern in smog because of its toxic effects. Ozone occurs
naturally in the upper atmosphere about 10-15 miles above the surface.
Ground-to-cloud lightning: A lightning bolt in which the original stroke
jumps upward from some object on the ground (usually from tall structures);
the opposite of more common cloud-to-ground discharges.
Ground truth: A direct measurement or observation of the state of the
weather to verify information determined remotely. Radar determinations of
severe weather often require ground-truth verification.
Growing season: (1) The period during the year in which temperatures remain
high enough for plant growth. Commonly accepted: the number of days between
the last spring and first fall occurrences of 32 degrees.
Growing season: (2) The period of the year during which the temperature of
cultivated vegetation (that is, the temperature of the microclimate in which
the plants are growing) remains high enough for plant growth.
Growler: An iceberg less than about seven feet across and floating with less
than three feet of its mass showing above water.
Gulf air: Air that spreads north across the U.S. after having acquired
considerable warmth and moisture in transit across the warm waters of the
Gulf of Mexico. A major moisture source for eastern U.S. precipitation.
Gulf Stream: Among the strongest, most constant ocean currents. It moves a
massive amount of water, approximately 100 times the amount of water carried
by all of the world's rivers combined. It originates in the Gulf of Mexico,
flows up the U.S. East Coast, leaves the coast at 40 deg N latitude, crosses
the Atlantic, arrives at the British Isles at 50 deg N.
Gully: A channel or miniature valley cut by concentrated runoff but through
which water usually flows only during or immediately after rain or during
periods of snowmelt.
Gush: In colloquial, non-meteorological usage, a cloudburst; a brief and
exceptionally intense rain, usually associated with thunderstorms.
Gust: A sudden, brief increase of at least 10 m.p.h. to at least 18 m.p.h.in
the speed of the wind quickly followed by a lull or slackening of the wind
speed. The duration of a wind gust is usually less than 20 seconds.
Gust front: The miniature cold front created by the downdraft of a
thunderstorm as air descending in the storm's downdraft nears the surface
and rushes outward, usually ahead of the storm.
Gustiness: A quality of air movement with frequent, sudden increases in the
wind speed to at least 10 m.p.h. above the prevailing speed, followed by
equally sudden speed decreases.
Gustnado: A weak and usually short-lived tornado appearing as a temporary
dust whirl or debris cloud that forms along a thunderstorm gust front (cool
outflow winds at the onset of a thunderstorm).
Guttation: Water exuded from leaves. It appears as a single large drop
pendant at the tip of a leaf or blade of foliage, and in grass it is often
confused with dew.
Gutter: A channel for draining off water, as at the edge of a street or
under the border of a roof; also, a groove formed by running water.
Copyright © 2008, WGN-TV
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