Chapter 6. Biogeography:
Climate, Biomes and
Terrestrial Biodiversity
Living in the Environment
Miller’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.
Temperature
Pressure
Humidity
Precipitation
Sunshine
Cloud cover
What are Highs and Lows?
changes in atmospheric pressure
• 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
Highs and Lows
Weather Extremes
• Tornadoes
• Tropical cyclones
Atlantic Ocean = hurricanes
Pacific Ocean = typhoons
Descending
cool air
Severe thunderstorms
can trigger a number
of smaller tornadoes
Severe
thunderstorm
Rising
warm air
Tornado forms when
cool downdraft and
warm updraft of air
meet and interact
Rising
updraft
of air
Tropical Cyclones
Rising winds exit
from the storm at
high altitudes.
The calm central
eye usually is about
24 kilometers
(15 miles) wide.
Gales circle the eye at speeds
of up to 320 kilometers
(200 miles) per hour.
Moist surface winds
spiral in towards the
center of the storm
Prince William
Sound
Gulf of Alaska
Risk of Tornadoes
Highest
High
Medium
Low
CANADA
UNITED STATES
Grand Banks
Tropical Cyclone
Frequency
High
Moderately
high
MEXICO
Atlantic
Ocean
Climate
is
Climate
the average weather patterns for an area over
a long period of time (30 - 1,000,000 years).
and
It is determined by
its
Average Precipitation
effects
and
Average Temperature
which are influenced by
latitude
altitude
ocean currents
and affects
where people live
how people live
what they
grow and eat
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)
Cold
Cool Temperate
Warm Temperate
Tropical
(equator)
Tropical
Warm Temperate
Cool Temperate
Cold
Climate type
23.5º
Winter
(northern hemisphere
tilts away from sun)
Spring
(sun aims directly
at equator)
Solar
radiation
Fall
(sun aims directly at
equator)
Summer
(northern hemisphere
tilts toward sun)
© 2004 Brooks/Cole – Thomson Learning
Easterlies
(from the east)
Westerlies
(from the west)
60°N
Northeast
tradewinds
30°N
(Doldrums)
equator
Southeast
tradewinds
30°S
Westerlies
60°S
Initial pattern of
air circulation
Easterlies
Deflections in the
paths of air flow
near the earth’s surface
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.
Cold,
dry air
falls
Cell 3 North
Polar cap
Arctic tundra
Evergreen
coniferous forest
60°
Temperate deciduous
forest and grassland
Desert
30°
Cell 2 North
Cool, dry
air falls
Cell 1 North
Tropical deciduous forest
0°
Equator
Tropical
rain forest
Tropical deciduous forest
Cell 1 South
30°
60°
Desert
Temperate deciduous
forest and grassland
Cool, dry
air falls
Cell 2 South
Polar cap
Cold,
dry air
falls
Relationship
between
global air
circulation
and biomes
Moist air rises — rain
Moist air rises — rain
Cell 3 South
Moist
air rises,
cools, and
releases
moisture
as rain
Solar
radiation
Convection
cell
Cool
Warm
current
Cool
current
air
Equator
Warm
air
Warm
water
Warm
current
Cool
current
Polar
front
Surface
Currents
Midlevel
currents
Bottom
Currents
Cold
water
Ocean
Currents
Polar (ice)
Warm temperate
Highland
Warm ocean current
Subarctic (snow)
Dry
Major upwelling zones
Cold ocean current
Cool temperate
Tropical
River
Movement of
surface water
Wind
Diving birds
Fish
Upwelling
Zooplankton
Phytoplankton
Nutrients
A shore upwelling
What is the El Nino-Southern Oscillation
(ENSO)?
1) Occurs in the Pacific Ocean
2) Prevailing westerly winds weaken
or cease
3) Surface water along the South and
North America coasts become
warmer
4) The normal upwelling of cold,
nutrient rich water are suppressed
Surface winds
blow westward
EQUATOR
AUSTRALIA
Warm waters
pushed westward
SOUTH
AMERICA
Warm water
Thermocline
Cold water
Normal Conditions
Winds weaken,
causing updrafts
and storms
Drought in
Australia and
Southeast Asia
EQUATOR
AUSTRALIA
Warm water
flow stopped
or reversed
SOUTH
AMERICA
Warm water deepens off
South America
Warm water
Thermocline
Cold water
El Niño Conditions
El Niño
Drought
Unusually high rainfall
Unusually warm periods
the greenhouse effect
Major
Greenhouse
Gases
1)
2)
3)
4)
5)
Water vapor H2O
Carbon dioxide CO2
Methane CH4
Nitrous oxide N2O
Chlorofluorocarbons CFCs
a Winds carry
moisture inland
from Pacific Ocean
b Clouds, rain on
windward side of
mountain range
c Rain shadow on
leeward side of
mountain range
Dry habitats
Moist habitats
the rain shadow effect
Rain Shadow Effect