Download The Atmosphere (E) - Westmount High School

Ch.7 The Atmosphere (EST)
Atmosphere: refers to the layer of air that surrounds our planet
Air Pollution
- the composition of the atmosphere is affected by the
presence of humans
- the atmosphere has a known and relatively constant
distribution of gases (see regular science notes)
- Addition of substances that distort the atmosphere’s
equilibrium constitutes air pollution
- Acid Rain: is formed by the addition of sulphur dioxide (SO2),
and nitrous oxides (NOx). These substances become
dissolved in the rain water, changing its pH.
- Smog*: is also caused by the above-mentioned products.
- Metals: such as mercury, arsenic and lead that enter the
atmosphere as a result of burning garbage, producing glass,
or burning fossil fuels can cause health problems, especially
since they are prone to bioaccumulation
- Destruction of the Ozone layer**: by CFCs and other gases
that attack the O3 molecules
- Dust and other particulate matter: can cause breathing
problems, especially for the very young and very old.
- It is important to note that air pollution is not limited to the
regions immediately surrounding the source, the pollution
can spread by winds
*SMOG
- is a word that is a combination of “smoke” and “fog”.
- it is a thick mix of smoke and fog that sits close to the
surface of the earth.
- It can be caused by emissions from factories, automobiles,
heating systems etc. that evacuate NO2, SO2 and other
gases into the air.
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**Destruction of the Ozone Layer
- ozone is a molecule that is formed when three oxygen atoms
combine together
- the ozone layer is found in the stratosphere, about 20-30 km
above the surface of the earth
- the ozone layer is essential to life on the planet since ozone
is particularly effective at absorbing a large proportion of the
ultra-violet (UV) rays emitted by the sun
- without this protective layer, life forms would be bombarded
by these rays, which cause damage (sometime irreparable)
to the DNA in each and every exposed cell
- the ozone layer is shrinking, and it has been observed that
since the 1970s, we have lost ~ 6% of the depth of the
ozone layer
- in the 1980s, scientists figured out that CFCs were
responsible for this destruction, and in 1987, the Montreal
Protocol was ratified, an initiative that called for the gradual
reduction of CFC production, with a complete ban coming
into effect by 2010!
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Atmospheric Circulation
- The air around our planet is in constant movement. It rises in hot
regions and falls in cold regions, creating convection currents.
- Convection movements occur on a global scale; these movements
are collectively called global winds.
- How do winds circulate around the globe? Imagine that the Earth
stops rotating for a minute and see what is happening…
- The Earth’s surface is very hot at the equator, warming the air.
This lighter, hot air rises. At ground level, this creates a low
pressure zone or depression. Air covering the rest of the Earth is
colder, especially at the poles.
- This colder, heavier air therefore moves downwards towards the
Earth’s surface. This results in the formation of a high pressure
zone or anticyclone.
- In this scenario, one can conclude that two convection cells would
occur with each occupying a hemisphere.
- Another effect of an immobile Earth would be winds blowing from
the poles towards the equator. However, the Earth does rotate on
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its axis, and one must consider the effects of this movement on
winds.
- Because of the Earth’s rotation, each of the two convection cells is
divided into two smaller parts.
- If you were an astronaut circling the Earth, you would see air
mass movements like those shown below.
Polar Cell: the air reaches the lowest
temperatures above the poles. It sinks
towards the Earth, where it encounters
the Ferrel cell. Here at the boundary
the air is forced upwards back toward
the poles.
Hadley Cell: warm air from above the
equator rises in the atmosphere. Once
airbone, the air travels towards the 30th
parallel. Here is collides with the air
from the Ferrel cell, and sinks,
returning toward the equator.
Ferrel Cell: One part of the
descending air near the 30th parallel
moves towards the pole. Near the 60th
parallel, the air collides with the polar
cell. The warmer air rises, and heads
back toward the 30th parallel.
- You would see the low pressure zone near the equator. Air
coming from the equator moves down towards the Earth’s surface
at 30º North Latitude.
- This air forms a zone of high pressure. At 60º North Latitude, you
would see a low pressure ridge because cold air coming from the
pole is warmed along its course and consequently rises.
- At the North Pole, air pressure is always high since cold air
descends to the Earth’s surface.
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- The same alternation of low and high pressure zones is observed
in the southern hemisphere. The rotation of the Earth affects wind
direction.
- Winds diverge at the Earth’s surface and follow curved pathways.
You can observe this effect by letting drops of water fall onto a
moving globe. You will see that the drop follows a curved
pathway.
- Each part of the Earth has winds which blow in a particular
direction; these are called prevailing winds.
Prevailing Winds
- Air rises at the equator, and there is no wind. In the days of
sailing ships, mariners hated this region as they sometimes had
to wait weeks for just a mild breeze.
- Regular winds that blow in neighbouring regions of the equator
are the trade winds.
- Temperate regions are characterized by the westerly winds.
This is not to say that winds do not blow from other directions in
these regions but that the dominant winds come from the
specified direction.
- Polar regions are characterized by the easterlies.
- These prevailing winds blow over vast regions on the earth.
There are other more localized winds such as the sea and land
breezes.
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To do:
Page 246-248 of observatory textbook
Questions 10-11 & 18-20
Then complete the following
The Atmosphere
1. a) What is the main gas found in the atmosphere, and
b) what are its roles?
2. a) Why is the second most common gas also important to life, and
b) where did it come from?
3
a) Identify the gas whose percentage can vary from <1 to almost 5,
b) which biomes’ atmospheres have the most
c) which have the least?
4. a) What is atmospheric pressure and,
b) mention two factors that could make it change.
6. What is the Coriolis effect
7. Taking the westerlies into account, predict which will take longer: cycling from Quebec City to
Montreal or cycling from Montreal to Quebec City, assuming the same leg strength.
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8. a) What are the key latitudes that separate Hadley cells from Ferrel cells?
b) Why do these cells exist?
9. a) At what latitudes do we find trade winds?
b) What is their direction in the Northern hemisphere? Southern hemisphere?
10. Why does flying to Europe from Quebec take less time than the return trip?
11. Describe each of the following: Hadley Cell, Ferrel Cell, and Polar Cell. In your description, include
the following:
a) A description of the type of cell
b) an explanation of how that cell develops
c) The cell’s location with respect to the equator
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