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Chapter 6 Weather. Weather An area’s short term (usually a day) atmospheric condition Differs from climate which is weather over a long period of time Climate Determined by average temperature and precipitation over a period of time (usually a year) Climate then determines an areas biome. - PowerPoint PPT Presentation
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Chapter 6
Weather
Weather• An area’s short term (usually a day) atmospheric
condition• Differs from climate which is weather over a long
period of timeClimate• Determined by average temperature and
precipitation over a period of time (usually a year)• Climate then determines an areas biome
Global Air CirculationCaused by 4 factors1. Uneven heating of the Earth’s
surface- poles vs equator2. Seasons caused by the tilt of the
Earth3. Rotation of the Earth- spins faster at
the equator than at the poles causing prevailing winds
4. Evaporating water creating convection cells
60ºN
30ºN
0º
30ºs
60ºS
Cold deserts
Westerlies Forests
Hot desertsNortheast trades
ForestsEquator
Hot deserts
Forests
Southeast trades
Westerlies
Cold deserts
Physical properties of atmosphere
• Warm air, less dense (rises)
• Cool air, more dense (sinks)
• Moist air, less dense (rises)
• Dry air, more dense (sinks)
Fig. 6.5
Moist surface warmed by sun
Flows toward low pressure,picks up moisture and heat
Warm,dry air
Hot, wetair
Falls, is compressed, warms Rises, expands, cools
Heat releasedradiates to space
LOWPRESSURE
HIGHPRESSURE
Cool, dryair
Condensationand
precipitation
HIGHPRESSURE
LOWPRESSURE
Dry woodlands and shrublands (chaparral)
Temperate grassland
Temperate deciduous forest
Boreal forest (taiga), evergreen coniferousforest (e.g., montane coniferous forest)
Arctic tundra (polar grasslands)
Tropical savanna,thorn forest
Tropical scrub forest
Tropical deciduous forest
Tropical rain forest,tropical evergreen forest
Desert
Ice
Mountains(complex zonation)
Semidesert,arid grassland
Tropic ofCapricorn
Equator
Tropic ofCancer
Polar (ice)
Subarctic (snow)
Cool temperate
Warm temperate
Dry
Tropical
Highland
Major upwelling zones
Warm ocean currentCold ocean current
River
Ocean Currents and Climate• Ocean currents help to mix
nutrients and dissolved oxygen, as well as influence the climate of coastal regions
• Winds blowing westward push surface waters away from the coast and cold, nutrient rich water takes its place (upwelling)
• Upwelling leads to high productivity
Normal Conditions
El Nino Conditions
La Nina Conditions
