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This section explores the various factors that determine climate and weather patterns, including latitude, atmospheric and oceanic circulation patterns, local geography, solar and volcanic activity.
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Chapter 13 Section 1: Atmosphere and Climate Change
Terms • Weather: state of the atmosphere at a particular place at a particular moment. • Climate: long-term prevailing weather conditions at a particular place based upon records taken.
What Factors Determine Climate? • Latitude • Atmospheric circulation patterns • Oceanic Circulation patterns • Local geography of an area • Solar activity • Volcanic Activity • Distance from the equator
Latitude • Distance from the equator measured in degrees north or south of the equator. • Low latitudes: temperatures high year-round. No summers or winters. • High latitudes: yearly temperature range is larger.
Atmospheric Circulation • Cold air sinks • As cold air sinks, it compresses and warms. • Warm air rises, expands and cools.
Solar energy heats the ground, which warms the air above it. • This warm air rises, and cooler air moves in to replace it. (WIND) • Circulation pattern determines precipitation pattern. • Areas near equator are warmer, warm air holds more water. As water cools, it cannot hold as much water—this leads to rain.
Global Circulation Patterns • Cool air over the equator is forced toward the poles. • Cold, dry air descends at the poles, which are essentially very cold deserts. • Coriolis Effect – air defected from its path due to earth’s rotation http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/gifs/coriolis.mov
Three Prevailing Winds Due to Coriolis Effect • Polar easterlies • Westerlies • Trade Winds
Prevailing Winds • Prevailing winds: winds that blow predominantly in one direction throughout the year. • Trade winds: Blow from the northeast in the Northern hemisphere and the southeast in the Southern hemisphere. Near the equator. • Westerly's: northwest winds in Northern hemisphere, and southwest winds in the Southern hemisphere. 30-60o latitude • Easterlies: cold dry air – cold deserts
Oceanic Circulation Patterns • Surface currents affect the climate in many parts of the world. • El Niňo: Pacific ocean is warmer than usual. Causes increased rainfall in some areas and droughts in others. • La Niňa: (opposite) Pacific is cooler than usual.
Topography • Mountains trap clouds, which can cause rain on one side and dry air and climate on the other.
Other Influences on Earth’s Climate • Sun: Increased UV rays = increased ozone = warmer atmosphere. • Volcanic eruptions: sulfur dioxide released reflects sunlight and causes global temp. to decrease.
Seasonal Changes in Climate • Seasons change as a result of the earth’s tilt on its axis. • Northern hemisphere tilts toward sun in summer and away from it during winter.