Ch. 6 and 7 Weather, Climate and Biomes

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Ch. 6 and 7Weather, Climate and Biomes

• Mrs. Sealy APES

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Weather

• The short-term day-to-day changes in temperature,
  air pressure, humidity, precipitation, sunshine,
  cloud cover and wind direction and speed.
• Most weather is predicted using
• weather balloons, aircraft, radar, and
  satellites

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Weather Changes

• Air Masses large lump of air that similar
  temperature and moisture level throughout.
• Air Masses that effect the US are

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When air masses meet it causes changes in weather

• Cold front when a cold air mass collides with a
  stationary warm air mass. The result is
  thunderstorms, short bursts of heavy rain

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Warm Front

• when a warm air mass collides with a stationary
  cold air mass. The result is warm steady rain

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Weather is also affected by changes in
atmospheric pressure

• High pressure has descending air that moves
  outward from the center of the high-pressure
  system. Descending air is warm and dry. The
  result is nice dry weather

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Low pressure

• has ascending air that flows towards the center
  of the low-pressure area. Ascending air-cools and
  condenses as it rises. The result is clouds, rain

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Weather Extremes

• Hurricanes
• What is it? Tropical storm with winds greater
  than 75 mph
• The bad loss of life and property
• The good flushes out coastline

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Tornadoes

• Form when cold dry air collides with warm moist
  air, which causes the warm air to rise quickly
  making a funnel cloud

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Prince Williams Sound
Gulf of Alaska
Risk of Tornadoes
CANADA
Highest
High
Medium
UNITED STATES
Low
Grand Banks
Hurricane Frequency
High
Moderately high
Atlantic Ocean
MEXICO
Fig. 6.2, p. 122
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Climate

• Climate is the long term average precipitation
  and temperature of an area
• Climate is determined by global wind patterns,
  latitude, altitude and ocean currents

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Climate
is
the average weather patterns for an area over a
long period of time (30 - 1,000,000 years).
It is determined by
Average Temperature
and
Average Precipitation
which are influenced by
latitude
altitude
ocean currents
and affects
Fig. 6.3, p. 123
what they grow and eat
where people live
how people live
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Warm ocean current
Warm temperate
Highland
Polar (ice)
Cold ocean current
Dry
Major upwelling zones
Subarctic (snow)
Fig. 6.4, p. 124
River
Tropical
Cool temperate
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Global Air currents affect regional climates

• Uneven heating of the Earths surface causes the
  equator to receive more sunlight making it
  hotter the poles receive less light making them
  cooler. This causes global circulation

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Easterlies (from the east)
Westerlies (from the west)
60N
Northeast tradewinds
30N
(Doldrums)
equator
Southeast tradewinds
30S
Westerlies
Easterlies
60S
Deflections in the paths of air flow near the
earths surface 
Initial pattern of air circulation
Fig. 6.6b, p. 125
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Cold
Cool Temperate
Warm Temperate
Tropical
(equator)
Tropical
Warm Temperate
Cool Temperate
Cold
Fig. 6.6a, p. 125
Climate type
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Seasons

• Seasonal changes in temp and precipitation affect
  climate because the earth is tilted on its axis.
  It is colder in the winter and warmer in the
  summer because

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Spring (sun aims directly at equator)
Winter (northern hemisphere tilts away from sun)
Solar radiation
Summer (northern hemisphere tilts toward sun)
Fig. 6.5, p. 124
Fall (sun aims directly at equator)
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Coriolis Effect

• Rotation of the Earth on its axis prevents air
  currents from moving directly north or south
  causing the winds to curve in what is called

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Ocean Currents

• Long term variations in the amount of incoming
  solar radiation
• Heat from the sun evaporates water and transfers
  energy from the ocean to the atmosphere. This
  creates convection cells that transport heat to
  different latitudes. This leads to ocean
  currents and weather

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Warm ocean current
Warm temperate
Highland
Polar (ice)
Cold ocean current
Dry
Major upwelling zones
Subarctic (snow)
Fig. 6.4, p. 124
River
Tropical
Cool temperate
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• Ocean Currents Affect climate
• Differences in water temp, winds and the rotation
  of the earth create currents.
• Currents redistribute heat. For example the gulf
  stream brings heat to Europe

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• Upwelling is created when the trade winds blow
  offshore pushing surface water away from land.
  The outgoing surface water is replaced by
  nutrient bottom water. Upwelling support

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Wind
Movement of surface water
Diving birds
Fish
Upwelling
Zooplankton
Phytoplankton
Nutrients
Fig. 6.9, p. 126
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The El Nino Southern Oscillation occurs every few
years in the Pacific Ocean

• In an ENSO, prevailing westerly winds weaken or
  stop
• Surface waters along the coast of North America
  and South America (west) become warmer
• Normal upwelling stops
• This reduces the population of some fish species
• Also causes severe weather, storms in the US
  especially CA, and drought in southeast Asia

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Surface winds blow westward
EQUATOR
SOUTH AMERICA
Warm waters pushed westward
AUSTRALIA
Warm water
Thermocline
Cold water
Normal Conditions
Fig. 6.10a, p. 127
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3
198283
199798
El Nino conditions
La Nina conditions
2
1
Temperature/Change (F)
0
-1
-2
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
Year
Fig. 6.12, p. 128
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Winds weaken, causing updrafts and storms
Drought in Australia and Southeast Asia
EQUATOR
Warm water flow stopped or reversed
SOUTH AMERICA
AUSTRALIA
Warm water deepens off South America
Warm water
Thermocline
Cold water
El Niño Conditions
Fig. 6.10b, p. 127
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El Niño
Drought
Unusually high rainfall
Unusually warm periods
Fig. 6.11, p. 127
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La Nina

• La Ninas follow an El Nino and are characterized
  by cooling trends. La Nina brings more Atlantic
  hurricanes, colder winters in the north and
  warmer winters in the south, and an increase in
  tornadoes.

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The chemical makeup of the atmosphere affects the
weather.

• Small amounts of water vapor, carbon dioxide,
  ozone, methane, nitrous oxide and
  chlorofluorocarbons trap heat in the atmosphere
  warming the planet. These gases are called
  greenhouse gases
• The greenhouse effect is when greenhouse gases
  allow light, infrared radiation and UV radiation
  through to the surface of the earth where it is
  reflected back into space. The greenhouse gases
  trap some reflected infrared radiation

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(a)
(b)
(c)
Rays of sunlight penetrate the lower atmosphere
and warm the earth's surface.
The earth's surface absorbs much of the incoming
solar radiation and degrades it to
longer-wavelength infrared radiation (heat),
which rises into the lower atmosphere. Some of
this heat escapes into space and some is absorbed
by molecules of greenhouse gases and emitted as
infrared radiation, which warms the lower
atmosphere.
As concentrations of greenhouse gases rise,
their molecules absorb and emit more infrared
radiation, which adds more heat to the lower
atmosphere.
Fig. 6.13, p. 128
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Ozone Layer

• The ozone layer is located in the stratosphere.
  It is created when ultraviolet light turns oxygen
  into ozone. The chemical reactions is
• Ozone blocks all short wavelength UV-C radiation,
  50 of the UV-B radiation and almost no long
  wavelength UV-A radiation.
• Ozone also forms a thermal cap which traps heat

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Topography of the earth also creates microclimates

• A microclimate is small area that has a
  different climate than the general climate of an
  area.
• Vegetation in an area influences climate forests
  stay warmer in the winter and cooler in the
  summer because of the trees
• Cities create heat
  islands that trap heat
  and decrease wind speeds

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Water also changes climate by causing land
breezes and sea breezes
Cool air descends
Warm air ascends
Land warmer than sea breeze flows onshore
Fig. 6.15a, p. 130
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Cool air descends
Warm air ascends
Land cooler than sea breeze flows offshore
Fig. 6.15b, p. 130
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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
4,000/75
3,000/85
2,000/25
1,800/125
1,000/25
Moist habitats
1,000/85
15/25
The rain shadow effect changes climate
Fig. 6.14, p. 129
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Tropic of Cancer
Equator
Tropic of Capricorn
Semidesert, arid grassland
Arctic tundra (polar grasslands)
Desert
Boreal forest (taiga), evergreen
coniferous forest (e.g., montane coniferous
forest)
Tropical rain forest, tropical evergreen forest
Mountains (complex zonation)
Temperate deciduous forest
Tropical deciduous forest
Ice
Temperate grassland
Tropical scrub forest
Fig. 6.16, p. 131
Dry woodlands and shrublands (chaparral)
Tropical savanna, thorn forest
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Polar
Subpolar
Temperate
Desert
Tropical
Desert
Fig. 6.17, p. 132
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Low
Alpine Tundra
Montane Coniferous Forest
Elevation
Deciduous Forest
Tropical Forest
High
Tropical Forest
Temperate Deciduous Forest
Northern Coniferous Forest
Arctic Tundra
Low
High
Moisture Availability
Fig. 6.18, p. 133
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Plant and animal adaptations to climate

• For plants precipitation is generally the
  limiting factor in determining whether a climate
  is a desert, forest or grassland, but biomes are
  not uniform. They have the same general
  characteristics but there are microclimates that
  determine the actual plants you will find in any
  given area.

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Plants exposed to cold year around or in the
winter have

• Traits that keep them from losing too much heat
  or water
• They stay small

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Desert plants must be able to lose heat and
conserve water. They do this by

• Lose heat and store water
• Fleshy tissue, vertical, no leaves, store water

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In wet tropical climates the plants have

• Broadleaf evergreen, maximize sunlight

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In climates that are hot in summer and cold in
winter, plants have

• Deciduous leaves that fall off in winter

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In areas with cool short summers, the trees have

• Coniferous evergreen
• Needle shaped leaves