Download File - Mr. Derrick Baker

Unit 2:
Patterns in Weather and Climate
Chapter 4:
Weather and Climate
Weather: daily atmospheric condition (heat, moisture, air
movement) for a given area.
Climate: average weather conditions over an extended period of
time.
The Three Main Factors that Affect both Weather and Climate:
1. Temperature.
2. Moisture.
3. Air Movement.
 Earth’s warmth is derived from the sun’s energy – INcoming
SOlar radiATION or INSOLATION.
 The Earth’s surface does not receive direct sun rays. WHY????
 Our atmosphere filters much of the insolation:

30% reflected to atmosphere.

17% absorbed by the air.

53% reaches the ground.
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 Of the radiation reaching the ground some is absorbed and some
is reflected.
 Snow and Ice REFLECT.
 Water, vegetation, dark ground ABSORB.
The Greenhouse Effect:
 The Earth system behaves like a greenhouse.
 The atmosphere, like the glass/plastic of a greenhouse traps
heat energy resulted increased temps.
 SHORT WAVE insolation reaches the ground and is
absorbed.
 The Earth heats up and gives off LONG WAVE terrestrial
radiation which is absorbed by the atmosphere causing it to
heat up.
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The Earth – Sun Relationship:
 Because the Earth is a sphere, all areas on the planet do not
receive the same intensity insolation.
 The Earth ROTATES on its axis toward EAST or
Counterclockwise when looking down from the North Pole.
 It takes the Earth 24 HOURS to make 1 complete rotation on
its axis.
 Earth REVOLVES around the sun counterclockwise looking
down from the North.
 It takes 365.25 days to make 1 complete REVOLUTION.
 This is why we have a LEAP YEAR every 4 years.
 This keeps our calendar in sync with the Earth’s
revolution.
 SEE FIGURE ON PAGE 56 IN TEXT.
 The Earth’s axis is tilted 23.5o from the vertical.
 This tilt is continuous during Earth’s revolution.
 This is why we have SEASONS in the higher latitudes.
 During part of the revolution, the North Pole is tilting away
from the sun.
 At another time, the North Pole is tilted toward the sun.
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 Titling toward and away from the sun affects the intensity of
the insolation.
 As we tilt AWAY from the sun, insolation is less intense and
we in the Northern Hemisphere experience cooler temps.
(our WINTER)
 During our summer, the Northern Hemisphere tilts
TOWARD the sun resulting in more intense radiation.
 SEE FIGURE 4.3 PAGE 56. (Magnifying Glass)
 The tilt of the axis also results in the length of DAYLIGHT
and NIGHTTIME varying throughout the year.
 At 2 times during the year the number of day and nights
hours is equal. - called EQUINOXES (equal night)
 MARCH 21 is the VERNAL (SPRING) EQUINOX.
 SEPT 22/23 is the AUTUMNAL EQUINOX.
 These dates mark the 1st day of Spring and Fall, respectively,
in the Northern Hemisphere.
 0o latitude is the EQUATOR.
 23.5oN is the TROPIC of CANCER.
 23.5oS is the TROPIC of CAPRICORN.
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 In Northern Hemisphere, the sun is directly overhead at noon
on JUNE 21 at 23.5oN.
 Longest day of the year.
 1st day of SUMMER is called the SUMMER SOLSTICE.
 On Dec 22nd, the sun is directly overhead at noon at 23.5oS.
 In the Northern Hemisphere, this is the shortest day of the
year. The beginning of WINTER, it is known as the
WINTER SOLSTICE.
Pattern in Temperature (Latitude):
 The Earth’s curvature causes the sun’s heat to be unevenly
distributed.
 When the Sun’s rays strike the Earth’s spherical body, the
region that corresponds to the equator receives more
radiation than the region corresponding to the poles.
Other Factors Affecting Climate:
1. Winds:
 The horizontal movement of air.
 Occur to equalize varying pressure within atmosphere.
 Air moves from HIGH PRESSURE to LOW
PRESSURE (Always).
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 There are major pressure belts over the globe:
 Winds are named according to the DIRECTION from
which they blow. (Note: Coriolis Effect)
 Winds, as a result, influence temperatures.
 They also influence moisture levels.
Wind’s Impact on Moisture:
A. Orographic Rainfall:
 Caused by abrupt changes in relief, air masses rise up
mountains.
 Air is forced to rise because it is deflected upward by
the high mountains.
 As the air rises, it cools and its ability to hold moisture
lessens (condensation occurs).
 By the time the air reaches the highest point on the
mountain, it has lost most of its water vapour it picked
dup over the ocean.
 The air begins to descend down the inland (leeward)
side of the mountain, it compresses and becomes
warmer.
 The relative humidity of the air lowers, having a drying
effect.
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 Rain Shadow – is an area of relatively low rainfall on
the leeward side of the uplands.
 Refer to figure 4.13 on page 66.
B. Frontal Rainfall:
 Occurs when a FRONT is created on the meeting of two
air masses with different temperatures.
 As a warm air comes in contact with colder air, it is forced
to rise up over the colder air because the colder air is
denser and heavier than the warm air.
 As the warm air rises, it becomes cooler.
 As the warm air cools, the relative humidity rises, to the
point at which the air masses can no longer hold the water
vapour it brought from the ocean.
 This water vapour condenses and falls as precipitation.
 Refer to figure 4.14 on page 66.
C. Convectional Rainfall:
 Not related to wind.
 Results from RAPID uplift of air due to intense
HEATING.
 Common along the equator.
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 This type of precipitation typically occurs in the summer
in mid-to late afternoon after a day of high rising
temperature.
 Lightning and thunder often accompany this type of
precipitation because the air flows quite rapidly and
intensely. Which cause considerable friction between the
air molecules.
 Refer to figure 4.15 on page 67.
2. Nearness of Land to Water:
 Land masses heat up and cool down more RAPIDLY than
water.
 Areas near the water often experience 2 types of BREEZES:
A. Land Breeze:
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Sea Breeze:
3. Ocean Currents:
 Refer to map on page 60.
 Currents (movements of large amounts of ocean water) result
from unequal heating of the top layer of water by the sun.
 Generally there is a circular flow of dense cold water of Polar
Regions to displace the less dense warmer water equatorial
zones.
 This equator ward flow is complicated by:
i.
ii.
iii.
iv.
Winds
Shorelines
Shape of continents
Earth’s rotation
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Influence on Weather/Climate:
 Warmer currents (Gulf Stream, Japan Current (or Kuroshio)
tend to modify or moderate temps of cooler areas into which
they flow.
 Ex: European weather warmed by Gulf Stream.
 Ex: B.C. coast warmed by the Kuroshio Current.
 Colder currents (Labrador, Peru Current) have a cooling
effect.
 These currents cool the air above which causes the air to have
less capacity for holding moisture.
 This results in generally lower precipitation levels for these
areas.
 Where warm and cold ocean currents meet FOG is produced.
 Ex: Grand Banks off NL meeting place of Gulf Stream and
Labrador Current = Heavy Fog.
4. Elevation of the Land:
 General rule: the HIGHER the elevation, the LOWER the
temperature.
 Before condensation occurs 1oC decrease for every 100 m
increase.
 After condensation occurs 0.6oC decrease for every 100 m
increase.
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Monsoons:
 Occur because of differences in heating over the interior of
the Asian continent and the Indian Ocean during different
seasons.
 In the winter, central Asia is very cold and an area of high
pressure develops over the area.
 Strong winds blow from this high pressure towards lower
pressure over the Indian Ocean.
 In the summer, the reverse takes place because the Asian
interior becomes very hot and a large low – pressure area
develops.
 Strong moisture – laden winds blow from high pressure over
the Indian Ocean towards the Asian and Indian Continent.
 Dry Monsoons from Sept. – March.
 Wet Monsoons from June – Sept.
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