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Chapter 6. Biogeography: Climate, Biomes and Terrestrial Biodiversity
Living in the EnvironmentMiller’s 13th Edition
www.wral.com/weather
What is weather?
Short-term set of physical properties of the troposphere at a particular place and time.
TemperaturePressureHumidityPrecipitationSunshine Cloud cover
What are Highs and Lows?
• High– Air mass with high
pressure– Cool, dense air
descends toward the earth’s surface and becomes warmer
• Low
– Air mass with low pressure
– Less dense warm air spirals inward
– The center of a low rises, and its warm air expands and cools
changes in atmospheric pressure
Highs and Lows
Weather Extremes
• Tornadoes
• Tropical cyclonesAtlantic Ocean = hurricanesPacific Ocean = typhoons
Descendingcool air
Severethunderstorm
Tornado forms whencool downdraft andwarm updraft of airmeet and interact
Risingwarm air
Severe thunderstormscan trigger a numberof smaller tornadoes
Risingupdraftof air
Rising winds exitfrom the storm athigh altitudes.
The calm centraleye usually is about
24 kilometers(15 miles) wide.
Moist surface windsspiral in towards thecenter of the storm
Gales circle the eye at speedsof up to 320 kilometers
(200 miles) per hour.
Tropical Cyclones
Risk of Tornadoes
Highest
High
Medium
Low
Tropical CycloneFrequency
High
Moderately high
Gulf of Alaska
Prince WilliamSound
CANADA
UNITED STATES
Grand Banks
Atlantic OceanMEXICO
Climate
the average weather patterns for an area overa long period of time (30 - 1,000,000 years).
is
It is determined by
Average Precipitation Average Temperatureand
which are influenced by
latitude altitude ocean currents
and affects
where people live how people livewhat they
grow and eat
Climate
and
its
effects
Global Air Circulation Patterns Result In:
1) Uneven heating of the earth’s surface.
2) Seasonal changes in temperature and precipitation.
3) Rotation of the earth on its axis• Deflect winds
Six convection cells (3N/3S)
Climate type
Cold
Cool Temperate
Warm Temperate
Tropical
(equator)
Tropical
Warm Temperate
Cool Temperate
Cold
Fall(sun aims directly at
equator)
Summer(northern hemisphere
tilts toward sun)
Spring(sun aims directly
at equator)
23.5º
Winter(northern hemispheretilts away from sun)
Solarradiation
Initial pattern of air circulation
Deflections in the paths of air flownear the earth’s surface
30°S
Easterlies
Westerlies
Southeasttradewinds
(Doldrums)
Northeasttradewinds
Westerlies(from the west)
Easterlies(from the east)
60°S
equator
30°N
60°N
© 2
004
Bro
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/Co
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Th
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son
Lea
rnin
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Global Air Circulation Patterns Result In:
4) Long term variation in the amount of solar energy
• Wobbles and tilts about the earth’s axis.
5) Properties of air and water• Convection Cells – circulate air, heat,
and moisture both vertically and from place to place.
Cell 3 South
Cold,dry air falls
Moist air rises — rain
Cell 2 South
Cool, dryair falls
Cell 1 South
Moistair rises,cools, andreleasesmoistureas rain
Cell 1 North
Cool, dryair falls
Cell 2 North
Moist air rises — rain
Cell 3 NorthCold,dry airfalls
Polar cap
Arctic tundra
60°
30°
0°
30°
60°
Polar cap
Evergreenconiferous forest
Temperate deciduousforest and grassland
Desert
Tropical deciduous forest
EquatorTropical rain forest
Tropical deciduous forest
DesertTemperate deciduousforest and grassland
Relationship between global air circulation and biomes
Warmcurrent Cool
air
Convectioncell
Coolcurrent
Warmair
Equator
Solarradiation
Warmwater
Warmcurrent
Polarfront
Coolcurrent
Coldwater
Ocean Currents
Surface Currents
Midlevel currents
Bottom Currents
Polar (ice)
Subarctic (snow)
Cool temperate
Warm temperate
Dry
Tropical
Highland
Major upwelling zones
Warm ocean current
Cold ocean current
River
Wind
Movement ofsurface water
Diving birds
Nutrients
Upwelling
Fish
Zooplankton
Phytoplankton
A shore upwelling
What is the El Nino-Southern Oscillation (ENSO)?
1) Occurs in the Pacific Ocean2) Prevailing westerly winds weaken
or cease3) Surface water along the South and
North America coasts become warmer
4) The normal upwelling of cold, nutrient rich water are suppressed
Normal Conditions
Cold water
Warm water
Thermocline
SOUTHAMERICA
Warm waterspushed westward
AUSTRALIA
EQUATOR
Surface windsblow westward
El Niño Conditions
Cold water
Thermocline
Warm waterWarm water deepens offSouth America
SOUTHAMERICA
Warm waterflow stoppedor reversed
AUSTRALIA
EQUATOR
Drought inAustralia andSoutheast Asia
Winds weaken,causing updraftsand storms
El Niño
Unusually warm periods
Unusually high rainfall
Drought
the greenhouse effect
1) Water vapor H2O
2) Carbon dioxide CO2
3) Methane CH4
4) Nitrous oxide N2O
5) Chlorofluorocarbons CFCs
Major Greenhouse Gases
a Winds carrymoisture inland
from Pacific Ocean
b Clouds, rain onwindward side ofmountain range
c Rain shadow onleeward side ofmountain range
Moist habitats
Dry habitats
the rain shadow effect
Rain Shadow Effect