Geo 305 Ch 8

Front 1

atmosphere

Back 1

Layer of gases surrounding a planet, such as Earth.

Front 2

blizzard

Back 2

A severe winter storm producing large amounts of falling or blowing snow that create low visibilities for extended periods of time. In the United States, for a storm to be classified as a blizzard winds must exceed 56 km (35 mi) per hour with visibilities of less than 0.4 km (0.25 mi) for at least 3 hours, and in Canada, for a storm to be classified as a blizzard winds must exceed 40 km (25 mi) per hour with visibilities of less than 1 km (0.6 mi) for at least 4 hours.

Front 3

Coriolis effect

Back 3

An apparent deflection in the path of a moving object. This apparent deflection, to the right in the Northern Hemisphere and left in the Southern Hemisphere, results from Earth's rotation. The magnitude of this effect increases with increasing latitude from the equator to the poles.

Front 4

drought

Back 4

Extended period of unusually low precipitation that produces a temporary shortage of water for people, other animals, and plants.

Front 5

dust storm

Back 5

A weather event in which visibility at eye level drops to less than 1 km (0.6 mi) for hours or days because of fine airborne particles of silt and clay.

Front 6

EF scale

Back 6

A graduated range of values from EF0 to EF5 for describing tornado intensity based on the maximum 3-second wind velocity inferred from damage to buildings, towers, poles, and trees. A modification of the F-scale developed by T. Theodore Fugita in 1971.

Front 7

fog

Back 7

A cloud that is in contact with the ground.

Front 8

heat index

Back 8

A value on a temperature scale that describes the human body's perception of air temperature, taking into account relative humidity.

Front 9

heat wave

Back 9

A prolonged period of extremely high air temperature that is both longer and hotter than normal. The criteria for establishing what constitutes longer and hotter than normal varies geographically with climate and living conditions.

Front 10

ice storm

Back 10

A prolonged period of freezing rain during which thick layers of ice accumulate on all cold surfaces.

Front 11

lightning

Back 11

A natural, high-voltage electrical discharge between a cloud and the ground, between clouds, or within clouds. The discharge takes a few tenths of a second and emits a flash of light that is followed by thunder.

Front 12

relative humidity

Back 12

A measure of the amount of water vapor in the air compared to the amount that would saturate the air at a given temperature and pressure; commonly expressed as a percentage.

Front 13

tornado

Back 13

A destructive, commonly funnel-shaped cloud of violently rotating winds that extends downward from a severe thunderstorm to reach Earth's surface.

Front 14

troposphere

Back 14

Lowermost layer of the atmosphere defined by a general decrease in temperature with increasing height above Earth's surface.

Front 15

urban heat island effect

Back 15

A local climatic condition resulting from various design and land-use practices in a city, large town, or other extensively developed area. This condition can intensify heatwaves and cause temperatures in a metropolitan area to be up to 12°C (22°F) warmer than the surrounding rural area.

Front 16

warning

Back 16

With respect to natural hazards, the announcement of a possible hazardous event, such as a large earthquake or flood, that could occur in the near future.

Front 17

watch

Back 17

With respect to weather, an alert issued by a forecast office that meteorological conditions are favorable for severe thunderstorm, winter storm, or flash flood.

Front 18

wind chill

Back 18

The influence of wind on the perception and actual effect of cold air. Meteorological agencies in the United States and Canada have developed a wind chill index based on how the human body loses heat in the cold and wind.