What's geography got to do with it?

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26 terms · ecosystems and the physical environment

Climate

the typical weather pattern in an area over a long period of time; depends on an number of factors: latitude, prevailing winds, ocean currents, topography, distance from large bodies of water, and altitude; the sun is the primary determinant of climate- weather and climate due to the interaction between atmosphere and solar energy

Albedo

the proportional reflectance of solar energy from Earth's surface; percentage of solar radiation reflected by a surface
- glaciers and ice sheets: reflects 80-90% of sunlight
- asphalt pavement and buildings: reflect 10-15%
- oceans and forests: reflect about 5%
- remaining 69% of the solar radiation is absorbed and runs the hydrologic cycle, drives winds and ocean currents, powers photosynthesis, and warms the planet

Latitude

the distance from the equator, measured in degrees north or south
- local variation of Earth's temperature is produced because the sun's energy does not reach all places uniformly; principal effect of Earth's tilt on it's axis is on the angle at which the sun's rays strike different areas of the planet at any one time
- sun's rays hit vertically near the equator, which makes energy more concentrated and produces higher temperatures
- At higher latitudes, the sun's rays hit more obliquely, resulting in the spreading of their energy over a larger surface area; pass through a deeper envelope of air, meaning more of sun's energy is scattered and reflected back to space, lowering temperatures near the poles

Seasons

determined primarily by Earth's inclination/tilt on its axis during its annual passage around the sun
- during half the year (March-September) the Northern Hemisphere tilts toward the sun, during the other half (September-March) it tilts away from the sun; summer in the NH corresponds with winter in the SH

The atmosphere

an invisible layer of gases that envelops Earth; most of the atmosphere's mass is found near earth's surface, becoming less dense as it extends outward into space (due to the force of gravity)

Troposphere

the layer of the atmosphere closest to Earth's surface; weather occurs in the troposphere

Atmospheric circulation

circulation of the atmosphere is driven by differences in temperature (due to variation in the amount of solar energy reaching different locations on Earth)

1) the warm surface near the equator heats the air in contact with it, causing the air to expand and rise in a process known as convection
2) as the warm air rises, it cools and then sinks again
3) heated air that does not immediately recirculate to the same area it has left splits and flows in two directions toward the poles
4)the air chills enough to sink to the surface at about 30 degrees N&S latitudes; this descending air splits and flows over the surface in two directions
5) at the poles, the cold polar air sinks and flows toward lower latitudes, typically beneath the sheets of warm air that simultaneously flow toward the poles

...the constant motion of air transfers heat from the equator toward the poles, and as the air returns, it cools the land over which it passes
- this continuous turnover moderates temperatures over earth's surfaces

Winds

horizontal movements of air from areas of high atmospheric pressure to areas of low atmospheric pressure

Coriolis effect

the influence of Earth's rotation on the direction of wind (deflection); tends to turn air and water toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere; effect is greater at higher altitudes, negligible at the equator; results in prevailing winds

Prevailing winds

major surface winds that blow more or less continuously from the same direction:
- polar easterlies: those that blow from the northeast near the North Pole or from the southeast near the South Pole
- Westerlies: generally blow in the mid altitudes from the southwest in the NH or from the northwest in the SH
- Trade winds: tropical winds blowing from the northeast in the NH or from the southeast in the SH

Low pressure bells (L)

created by rising air at the equator and latitude 60; air laden with water vapour, and on rising it cools and precipitation occurs

High pressure zones (H)

produced by descending air; these zones typically have dry air and little rainfall (arid regions, the sites of Earth's great deserts)

Currents

surface-ocean water currents are produced by the persistent prevailing winds blowing over the ocean; these winds generate gyres (circular ocean currents); paths of SOCs are influenced by the Coriolis Effect:
- rotation from west to east helps establish the circular, clockwise pattern of water currents in the Northern Hemisphere, and the circular, counter clockwise pattern in the Southern Hemisphere

Ocean circulation also affected by the position of land masses

Ocean conveyer belt

circulation of shallow and deep currents that moves cold, salty deep-sea water from higher to lower latitudes; caused by density differences between cold and warm water; affects regional (possibly global) climate:
-OCB responsible for the relatively warm climate in Europe: as the Gulf Stream and North Atlantic Drift push into the North Atlantic, they deliver a great amount of heat from the tropics to Europe

El Nino- Southern Oscillation (ENSO)

a periodic, large-scale warming of surface waters if the tropical eastern Pacific Ocean that affects both ocean and atmospheric circulation patterns; El Nino typically last from 1-2 years; alters global air currents, directing unusual, sometimes dangerous weather to areas far from the tropical Pacific

- weakening of trade winds allows the warm mass of water (usually restricted to the western Pacific near Australia) to collect and expand eastward to South America, increasing surface temperatures in the eastern Pacific
- Ocean currents which normally flow westward in this area slow down, stop all together, or reverse and go eastward
- upwelling is blocked by warm water

Upwelling

(costal) colder, nutrient-rich deep water comes to the surface partly in response to strong trade winds; occurs in the Pacific Ocean along the South American coast; weakens considerably during years with El Nino events, temporarily reducing fish populations (South American fisheries)

Topography

the surface features of a region; refers to the "relief" of the Earth's surface, that being its slope, aspect, relative sizes of land and bodies of water; may result in three small scale wind patterns (sea breezes, slope winds and Fohn winds), which can influence climate in localised regions (microclimates)

Sea breezes

during the day, the atmosphere over large bodies of water is cooler than over adjacent land. This is due to water having a higher heat capacity than soil, as the evaporation of water absorbs heat from the surrounding air.
- this means that hotter land air will rise and breezes will blow onshore, producing a cooling effect on adjacent land

At night, the land cools off more rapidly than the water, resulting in the breeze reversing to blow offshore

These winds as a moderator of the climate of costal regions, typically cooler during the day and warmer at night

Slope Winds

sloping terrain is often subject to local winds, which are generated by a temperature gradient between elevated and depressed areas
- elevated areas receive more direct solar radiation during the day under sunny conditions; air rises from the warm hilltop surfaces and surface winds move upslope
- at night, the elevated areas are often the first to cool off and the wind pattern is reversed
Microclimates of valleys are particularly complex.

Fohn Winds

the dry, warm winds formed on the lee side (sheltered side) of mountains
- on-shore breezes are forced upward by mountain ranges near the coast,
- accumulated moisture is deposited on the windward side of the mountains;
- dry air at the top of the mountain gains energy and temperature on descent

Leeward air is low in moisture, causing a zone of low precipitation called a rain shadow, to occur on the leeward side

Rain shadow

dry area/land that occurs on the leeward side of a mountain barrier; little precipitation

Altitude

the height (elevation) of something above sea level; as altitude increases, environments tend to become colder and more subject to frost

Weather

the conditions of the atmosphere at a given place and time; includes temperature, atmospheric pressure, precipitation, cloudiness, humidity and wind

Climate

the typical pattern of weather that occurs in a place over a period of years; temperature and precipitation= the two most important factors determining an area's climate (as well as wind, humidity, fog & cloud cover)
- usually changes slowly
- Earth has many climates, which organisms have adapted to as each is relatively constant; there are six climate zones:
humid equatorial; dry, humid temperate; humid cold; cold polar and highland climate

Precipitation

any form of water that falls from the atmosphere; rain, snow, sleet, hail

Tornadoes

powerful, rotating funnels of air associated with severe thunderstorms; 1) form when a mass of cool, dry air collides with warm, humid air, producing a strong updraft of spinning air on the underside of a cloud, 2) spinning funnel becomes a tornado when it descends from the cloud and touches the ground

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