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

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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