Download Weather Patterns - wbm-earth

Climate
Earth Science Chapter 18
Climate
• Average, year-after-year conditions
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Temperature
Precipitation
Wind
Clouds
Microclimate
• Small area with a climate different from
its surroundings
• Example: grove of trees
Factors affecting temperature
• Latitude
• Warmer near equator where sun is more
direct
• Altitude
• Cooler higher in atmosphere
• Distance from large bodies of water
• Oceans make temperatures less extreme
• Ocean currents
• Warm currents warm air above them, cool
currents cool air above them
Tropical zone
• Near equator
• Between 23.5°N and 23.5°S latitude
• Direct or near-direct sun all year
• Warm climates
Polar zone
• Near poles
• 66.5° to 90° N and 66.5° to 90° S
latitude
• Sun’s rays always at a lower angle
• Cold climates
Temperate zones
• Between tropical and polar zones
• In summer, more direct sun
• Warm weather
• In winter, less direct sun
• Cool weather
Marine climates
• Near oceans, especially on west coasts
• Relatively mild winters and cool
summers
• Ocean winds
Continental climates
• Too far inland to be affected by ocean
• More extreme temperatures
• Cold winters and hot summers
Factors determining precipitation
• Prevailing winds
• Areas downwind from large bodies of water
receive more precipitation
• Presence of mountains
• More precipitation on windward side, less on
leeward side
• Air cools as it rises
• Seasonal winds
• Like wide area land and sea breezes
Monsoons
• Sea and land breezes over a large
region that change direction with the
seasons
• Can produce heavy rains in summer,
little rain in winter
Seasons
• Caused by tilt of Earth’s axis
• NOT distance from Sun
• End (N or S) of Earth pointed toward
sun has summer
• End (N or S) pointed away from sun has
winter
• When neither is pointed towards it, it is
fall or spring
• Seasons website
Discuss
• Name four factors that affect temperature.
• List three factors that affect precipitation.
• Two locations are at the same latitude in the
temperate zone. One is in the middle of a
continent. The other is on a coast affected by
a warm ocean current. How will their climates
differ?
• How does a mountain range in the path of
prevailing winds affect precipitation on either
side of the mountains?
Six main climate regions
• Classified by temperature and
precipitation
• Tropical rainy
• Dry
• Temperate marine
• Temperate continental
• Polar
• Highlands
Tropical Rainy
• Tropical wet
• Many rainy days with thunderstorms all year long
• Only windward side of Hawaiian Islands in US
• Tropical wet-and-dry
• Slightly less rain that tropical wet
• Have distinct dry and rainy seasons
• Have tropical grasslands called savannas
• Grass with small clumps of trees
• Only on the southern tip of Florida in the US
Dry
• Precipitation that falls is less than what could
evaporate
• Not just low rainfall
• Arid
• Deserts
• Hot and sandy or cold or rocky
• Average less than 25 cm of rain per year
• Southwest US
• Semiarid
• Steppes - edges of deserts
• AKA prairie or grassland
• Enough rain for grasses and low bushes
Temperate Marine
• Marine west coast
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Coolest marine climate
Mild, rainy winters
between 40° latitude and pole
Heavy precipitation – thick forests
Northern California to southern Alaska
Temperate Marine
• Mediterranean
• Drier and warmer than west coast marine
• Mostly around Mediterranean sea
• Mild climate with two seasons
• Cool rainy winter
• Warmer, drier summer
• Southern California coast in US
Temperate Marine
• Humid subtropical
• Warmest marine climate
• Wet and warm, but not as consistently hot
as tropics
• Cool to mild winters with more rain than
snow
• SE US
Temperate Continental
• Extremes of temperature
• Only in northern hemisphere
• Humid Continental
• Constantly changing weather
• Bitter cold winters and hot humid summers
• Subarctic
• Farther north
• Short cool summers and long, bitterly cold
winters
• Pine trees
Polar
• Coldest
• Ice cap
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Always below freezing
Land covered with ice and snow
Dry air
Little vegetation
• Tundra
• Short, cool summers and bitterly cold winters
• Some layers of the soil are always frozen
(permafrost)
• Wet and boggy in summer
Highlands
• Colder than regions around them
• Precipitation increases with altitude
• Tree line – any higher, and too cold for
trees
Discuss
• What two major factors are used to identify
climates?
• What are the six main climate regions?
• Which place would have more sever winters
– central Russia or the west coast of France?
Why?
• How could a forest grow on a mountain that is
surrounded by desert?
• Place the following climates in order from
coldest to warmest: tundra, subarctic, humid
continental, ice cap
Climate-studying principle
• If plants or animals today need certain
conditions to live, then similar plants
and animals in the past also required
those conditions
Ancient climate information
• Pollen
• What types of plants used to live in an area
• What type of climate it used to have
• Tree Rings
• Thickness depends on temperature in cool
climates and amount of precipitation in dry
climates
Ice Ages
• AKA glacial episodes
• Glaciers covered large parts of Earth’s
surface
• Carve grooves in rock, deposit sediment
• Most recent was 10,500 years ago
• So much water in ice that the sea level was much
lower
• When melted, coastal areas flooded and Great
Lakes formed
Climate change causes
• Earth’s position
• Time Earth is closest to sun shifts over
23,000 years
• Angle of axis tilt also shifts slightly over
thousands of years
• Solar energy
• Sunspots – cool areas on the sun
• Sun produces more energy when there are
more sunspots – Earth warms
Climate change causes
• Volcanic Activity
• Gases and ash may filter solar radiation,
making it cooler
• Movement of continents
• Different locations on Earth
• Changed locations of land and sea
• Changed wind and ocean currents
Discuss
• What types of evidence do scientists
gather to study changes in climate?
• If you are studying tree rings, what do
several narrow rings in a row indicate?
• What occurs during an ice age?
Short-term climate changes
• El Niño
• Warm surface water from western Pacific
moves towards South American coast
• Can cause unusual and severe conditions
around the world
• Heavy rains or droughts
• Every two to seven years
Short-term climate changes
• La Niña
• Colder than normal waters in eastern
Pacific
• Can cause unusual and severe conditions
around the world
• Colder winters in Pacific NW
• Greater hurricane activity
Global Warming
• Gradual increase in temperature of
Earth’s atmosphere
• 0.5 °C in last 120 years
Greenhouse hypothesis
• Greenhouse gases trap in heat like the
glass in a greenhouse
• Carbon dioxide, water vapor, and methane
• Human activities may add greenhouse
gases to the air
Changing CO2 levels
• Increase in carbon dioxide might be a
major factor in global warming
• Increase might be from increased
burning of wood and fossil fuels
• Carbon dioxide level could double by
year 2100.
• Global temperature could rise by 1.5 to
3.5 °C
Climate variation hypothesis
• 0.5 °C rise in last 120 years might be
from natural climate variation
• Could be due to solar energy variations
• Could be a combination of increased
CO2 and solar energy variations
Possible Global Warming effects
• Farmers in some areas could plant two
crops per year
• Cold places could become farmland
• Fertile fields might become dust bowls
• Warmer ocean water could mean
stronger hurricanes
• Sea level could rise, causing flooding
• Already 10 – 20 cm rise over last 100
years
Ozone depletion
• CFCs damage ozone layer
• Over Antarctica because of winds in the
atmosphere
• Increase in skin cancer and eye
damage
CFC bans
• US and many other countries banned
from aerosols in late 1970s
• 1990 – many nations agreed to phase
out entirely
• Should be eliminated from US use next
year
• Should gradually shrink ozone hole
Discuss
• What are two events that can lead to
short-term climate change?
• What are two things that might
contribute to global warming?
• What effect have human activities had
on the ozone layer?