Transcript Chapter 6. Biogeography: Climate, Biomes and Terrestrial Biodiversity

Chapter 6. Climate, Terrestrial
Biodiversity, and Aquatic
Biodiversity
Section 6-1 Weather and
Climate: A Brief Introduction
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 is weather?
• Meteorologists use equipment to
obtain data on weather variables:
–
–
–
–
Atmospheric pressure
Precipitation
Temperatures
Wind speeds locations of air masses and
fronts
This data is fed into computer models to
draw weather maps to forecast the
weather
What is Climate?
• Climate is a region’s general pattern of
atmospheric of weather conditions
over a LONG period of time
– Average temperature and average
precipitation are the two main factors
that determine a region’s climate
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
effects
Average Precipitation
and
Average Temperature
which are influenced by
latitude
altitude
ocean currents
and affects
where people live
how people live
what they
grow and eat
5 factors that determine global
air circulation patterns
1.
2.
3.
4.
5.
Uneven heating of Earth
Seasons
Earth’s rotation
Variation of sun’s output
Properties of air and water
1. Uneven Heating of the Earth
Cold
Cool Temperate
Warm Temperate
Tropical
(equator)
Tropical
Warm Temperate
Cool Temperate
Cold
Climate type
2. Seasons
3. Rotation of Earth
4. Variations in solar output
5.
Properties
of Properties
air and
•5.
of air and
water
water
– Convection Cells –
circulate air, heat,
and moisture both
vertically and from
place to place.
How do ocean currents affect
regional climates?
• The five factors PLUS differences in water
density create warm and cold ocean
currents.
• These currents (driven by winds and earth’s
rotation) redistribute heat and therefore
influence climate and vegetation
– If ocean’s currents suddenly stopped flowing,
there would be deserts in the tropics and thick
ice over northern Europe, Siberia, and Canada
– Currents also mix ocean waters and distribute
nutrients and dissolved oxygen needed by
aquatic organisms
60,000 Nikes spilled into the Pacific
Polar (ice)
Warm temperate
Highland
Warm ocean current
Subarctic (snow)
Dry
Major upwelling zones
Cold ocean current
Cool temperate
Tropical
River
CD ani 2
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
Movement of
surface water
Wind
Diving birds
Fish
Upwelling
Zooplankton
Phytoplankton
Nutrients
Upwellings – winds push surface water away from the
land, this water is replaced by cold-nutrient rich bottom
water – brings deep cool water to the surface
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
El Nino - “The Christ Child”
El Niño is a disruption of the oceanatmosphere system in the Tropical
Pacific having important
consequences for weather and
climate around the globe.
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
Bad fishing
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
La Nina
• Cooling counterpart of El Nino
• Means more Atlantic hurricanes,
colder winters in Canada and
northeastern US, warmer and drier
winters in the southeastern and
southwestern US and more wildfires in
Florida
How does the chemical makeup of the atmosphere lead to
the greenhouse effect?
The Greenhouse
Effect
Major
Greenhouse
Gases
1)
2)
3)
4)
5)
Water vapor H2O
Carbon dioxide CO2
Methane CH4
Nitrous oxide N2O
Chlorofluorocarbons CFCs
Are Greenhouse Gases
GOOD or BAD?
• THEY’RE BOTH
• GOOD - without greenhouse gases,
the Earth would be too cold for life
• BAD - too many greenhouse gases
may lead to global warming
Where do greenhouse gases
come from?
• ALL OF US!!!
• Burning fossil fuels releases:
– CO2
– H2O
– N2O
• Cows release methane (CH4)
• Various refrigerants use CFCs
How does the chemical
make-up of the atmosphere
create the ozone layer?
Is this what
the hole in
the ozone
layer looks
like?
Did Mrs. Gallo destroy the
OZONE… it’s possible…
Ozone
• In a nutshell – we will discuss in detail later in the
year
– In stratosphere oxygen (O2) is converted to
ozone (O3) and back to oxygen by a sequence
of reactions initiated by UV radiation from the sun
– Results in a thin veil protecting us from 95% of
sun’s harmful UV radiation
– Evidence indicates that chemicals added to
atmosphere by our activities are decreasing the
level of protection
– Thermal cap – warm layer of air created by
ozone layer that prevent churning gases in the
troposphere from entering the stratosphere,
important in determining average temp of
troposphere and climate
Microclimates – local climatic conditions that
differ from the general climate of a region
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
Rain Shadow Effect - lower precipitation
and semiarid or arid conditions on the
leeward side of a mountain-
Rain Shadow Effect
Cool air
descends
Land warmer than
sea; breeze flows
onshore
Sea Breeze
Warm air ascends
Cool air
descends
Warm air
ascends
Land cooler than
sea; breeze flows
offshore
Land Breeze
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
Hurricane Sandy FRANKENSTORM
• Hurricane Sandy was the largest Atlantic hurricane
on record
• The second-costliest Atlantic hurricane in history,
only surpassed by Hurricane Katrina in 2005
• Hurricane - A hurricane is a tropical storm with winds
that have reached a constant speed of 74 miles
per hour or more.
The eye of a storm is usually 20-30 miles wide and
may extend over 400 miles.
The dangers of a storm include torrential rains, high
winds and storm surges.
A hurricane can last for 2 weeks or more over open
water and can run a path across the entire length
of the Eastern Seaboard
•
Video – Weather Channel
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