Transcript Section 1.2 The Causes of Weather

Section 1.2
The Causes of Weather
Science 10
1. What three things affect the distribution of
solar energy that reaches the Earth?
• Three things that affect the distribution of
solar energy that reaches the Earth are the
curved surface, the tilt, and the orbit of the
Earth.
2. Using figure 1.11 on page 26, explain why areas closer to the
equator are warmer than areas closer to the poles.
• When sun hits the poles it is more spread out
over a larger area which means that it is less
concentrated so areas do not heat up as
much.
• When the sun’s light hits the areas closer to
the equator it is very concentrated over a
small area so the warming effect is much
greater.
3. Explain how the tilt of the Earth affects
seasonal changes.
• As the Earth orbits the sun the tilt of the poles
changes and this affects the weather in those
regions. When the northern hemisphere is tilted
toward the sun, the solar energy strikes the
surface of the Earth more directly and the
temperature is very warm.
• When the northern hemisphere
is tilted away from the sun
there is a less direct contact of
solar energy and much cooler
temperatures result.
4. How can the shape of the Earth’s orbit around the
sun affect the length and intensity of the seasons?
• Earth’s orbit around the sun may be circular or
oval and it changes every 100 000 years.
• The amount of solar energy the Earth gets
varies more when the orbit is oval and the
seasons will be longer and more intense.
• A circular orbit means that the solar energy is
more constant and the seasons will be more
balanced.
5. How does an air mass form and where do
most of them form?
• An air mass forms when
air close to the ground is
heated by conduction and
the warmed air rises.
• The resulting air mass
often has the same
properties such as
temperature, humidity
and pressure as the land it
formed over.
• Most air masses form over
tropical or polar regions.
6. What is the difference between an air mass that
forms over the interior of Canada and an air mass that
forms over the North Atlantic Ocean?
• An air mass that forms over the interior of
Canada is known as a Continental Polar air
mass and it will be very cold and dry during
the winter and cool and dry during the
summer.
• An air mass that forms over the North Atlantic
Ocean is known as a Maritime Polar air mass
and it will be cold and humid during the
winter and the summer.
7. Explain how a high pressure system
develops.
• A high pressure system develops
when an air mass cools over an
ocean or a cold region on land.
• The cooling of air particles causes
them to become more dense, the
air mass contracts pulling in more
air and the extra weight increases
pressure. This causes the air
mass to move outward towards
low pressure area (wind).
• The rotation of the Earth causes
the air to circulate in a clockwise
direction, the air sinks and
becomes warmer and drier.
• High pressure systems usually
bring clear skies.
8. Explain how a low pressure system develops.
• A low pressure system develops
when air masses traveling over
warm land or oceans warms up,
expands and rises increasing the
thickness of the layer of air. As the
warm air rises it cools, condenses
and forms clouds or precipitation.
• While this is occurring the
expanding air mass is pushing away
air high in the troposphere, air
pressure near the surface of the
Earth decreases and this draws in air
from high pressure areas.
• The rotation of the Earth causes the
air in a low pressure system to curve
and the wind flows counter
clockwise in a northern hemisphere
and clockwise in the southern
hemisphere.
9. What is the Coriolis Effect and how does it
impact wind?
• The Coriolis Effect is a
change in the direction of
moving air, water, or any
object’s on the Earth’s
surface due to its
rotation.
• The Coriolis effect causes
air that is circulating to be
deflected in different
directions in the northern
(right) and southern (left)
hemispheres.
10. What are the three major wind systems and what
is their general path?
Wind system
Location
Path
Trade Winds
Between the equator and
30° north latitude.
Between the equator and
30° south latitude.
Air at the equator warms, rises
and travels to 30° north or south
latitude.
At 30° north or south the air
cools, sinks, and moves west
toward the equator and is
deflected west.
Prevailing Westerlies
Between 30° and 60°north
latitude.
Between 30° and 60° south
latitude.
Air circulation pattern is
opposite to that of the trade
winds.
Surface winds blow from west to
east and toward the poles.
Polar Easterlies
Between 60° north latitude
and the North Pole.
Between 60° north latitude
and the South Pole.
Air circulation pattern is similar
to that of the trade winds.
Surface winds blow from east to
west and away from the poles.
11. What is a jet stream? Identify the major
and minor jet streams.
• A jet stream is a narrow band of fast moving wind
and its speed varies with the temperatures of air
masses at the wind zone barriers.
• The major jet streams are known as the polar jet
streams and they separate the polar easterlies
from the prevailing westerlies.
• The minor jet streams are known as the
subtropical jet streams and they occur where the
prevailing westerlies meet the trade winds.
12. What is a front and what does an
approaching front mean in terms of weather?
• A front is a zone that develops as a result of
the meeting of two air masses with different
characteristics.
• An approaching front indicates that there will
be a change in the weather and the severity of
the change will depend on the difference
between the conditions of the two air masses.
• Also, fronts usually bring precipitation.
13. Identify the 4 types of weather fronts
that may form.
• The four types of weather fronts that may
form are:
• Cold front
• Warm front
• Stationary front
• Occluded front
14. What is a thunderhead and how does it form?
• Thunderheads are large cumulonimbus clouds
that form when water vapour in rising warm
air condenses and releases thermal energy.
• The released thermal energy warms the air
even further and it continues to rise.
• The resulting thunderheads take on a typical
anvil shape and can produce heavy rains, hail
and lightening.
15. What is a tornado and how does it form?
• A tornado is a violent, funnel-shaped column
of rotating air that touches the ground.
• They form when high altitude horizontal winds
meet large thunderstorms.
• The horizontal winds cause the rapidly rising
air in the thunderstorm to rotate and
produces a funnel cloud, which may touch the
ground and become a tornado.
16. Why are the tropics an ideal location for the
formation of intense storms?
• The tropics are the ideal location for the
formation of intense storms due to the warm
ocean water and winds.
• Warm moist air gets lifted into the atmosphere
where it condenses and produces precipitation
and clouds. The precipitation release large
amounts of thermal energy, the rising air
produces a low pressure area near the surface of
the water, warm air rushes in and the Coriolis
effect causes the air to rotate creating a massive
spinning storm.
17. What are the three types of tropical cyclones and
where do each of them occur?
• Tropical cyclones in areas near the Indian
Ocean are known as cyclones.
• Tropical cyclones that form near the Western
Pacific Ocean are known as typhoons.
• Tropical cyclones that form in the Atlantic
Ocean are known as hurricanes.