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Period ______
Atmosphere Stuff
 Read each topic and hi-lite/annotate.
 Answer practice questions to review your understanding.
 Watch videos and draw diagrams when required.
WEATHER AND CLIMATE
Practice
We refer to the local, short-term conditions in an
area as weather. This includes temperature, humidity,
_______ Which of the following is the best description of a region’s
cloud cover, precipitation, wind speed, and
climate?
atmospheric pressure. But weather only happens on
time scales from seconds to days. The average
A. The amount of rainfall that an area receives over a period of 1
weather in an area over a long period of time (at least
year.
several decades) is called climate.
Climate is defined by temperature and
B. The average precipitation over a 1-2 year time period.
precipitation and is what determines plants in an area,
which in turn, determines animals.
C. The average high temperature of a region.
There are six different factors that affect the
distribution of heat and precipitation around the
D. The average temperature and precipitation over several
world, thus leading to varying climates. These six
decades.
factors are unequal heating of Earth by the Sun,
atmospheric convection currents, the rotation of
E. The average temperature and rainfall over a period of 1-2
Earth, Earth’s orbit around the sun on a tilted axis,
years.
ocean currents, and Earth’s topography.
We will start with general information about the
atmosphere, then explore these six climatedetermining factors.
Take a deep breath. About 99% of the volume of air
you inhaled consists of two gases: nitrogen (78%)
and oxygen (21%). The remainder consists of water
vapor (varying from 0.01% at the frigid poles to 4%
in the humid tropics, for an average of about 1%),
0.93% argon (Ar), 0.039% carbon dioxide (CO2) and
trace amounts of dust and soot particles as well as
other gases including methane (CH4), ozone (O3),
and nitrous oxide (N2O).
Review Question:
The atmosphere is 78% nitrogen but it is in a form we are unable
to utilize. Describe how we are able to convert nitrogen gas (N2)
into a more useable form (use appropriate vocab, feel free to
draw diagram)
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EARTH’S ATMOSPHERE
The density of the gas molecules per unit of air
volume varies throughout the atmosphere because
gravity pulls its gas molecules toward the earth’s
surface. About 75-80% of the earth’s air mass is found
in the atmospheric layer closest to earth’s surface – the
troposphere. This layer extends about 11 miles above
sea level at the equator and 4 miles above sea level over
the poles. Most of the weather we experience occurs in
this layer. Air currents, winds, and concentrations of
CO2 and other greenhouse gases in the troposphere
play a major role in the planet’s weather and climate.
The layers of the atmosphere are based on
differences in temperature as altitude increases. Because
of radiation from Earth and the objects on it, the
troposphere is warmer at sea level (0 km altitude) and
cools as altitude increases.
Moving away from Earth, the next layer of the
atmosphere is the stratosphere. The stratosphere
contains a layer of air with a high concentration of
ozone molecules (O3), called the ozone layer.
Stratospheric ozone is formed when oxygen molecules
(O2) in this layer interact with ultraviolet (UV) radiation
from the sun. The ozone layer keeps about 95% of the
sun’s harmful UV radiation from reaching the earth’s
surface. This UV filtering effect allows life to exist on
Earth and protects us from sunburn, skin and eye
cancers, cataracts, and damage to our immune systems.
This absorption of UV also makes the stratosphere
warm as altitude increases, a trend opposite to that of
the troposphere.
Above the stratosphere is the mesosphere and then
the thermosphere. Without any heat absorbing
materials, the mesosphere is the coldest layer of the
atmosphere. The thermosphere is sometimes broken
down further into the ionsphere (an area of highly
charged particles where auroras occur) and the
exosphere (where many satellites orbit). Despite this
distinction, the entire thermosphere warms as altitude
increases.
Although there is no distinct beginning or end to
any of the layers, the transition from one to another is
known as a “pause”. For example, the transition from
troposphere to stratosphere is called the tropopause.
The stratopause divides the stratosphere and
mesosphere and the mesopause divides the mesosphere
and thermosphere. There is no pause after the
thermosphere because it blends into space as the
concentration of atmospheric molecules gets lower and
lower.
Sketch and label:
http://ds9.ssl.berkeley.edu/LWS_GEMS/3/layers.ht
m
 atmospheric layers (4)
 temperature
 ozone layer
Practice:
_____ In which level of the atmosphere does weather occur?
A. Troposphere
B. Stratosphere
C. Mesosphere
D. Thermosphere
E. Exosphere
_____ Which level of the atmosphere is the densest?
A. Troposphere
B. Stratosphere
C. Mesosphere
D. Thermosphere
E. Exosphere
_____ What best describes the density of the atmosphere?
A. It increases as you increase in altitude
B. It decreases as you increase in altitude
C. It maintains a constant level throughout the atmosphere
D. It shows fluctuations up and down as you move through the
layers of the atmosphere
E. It does not change
_____ What is the importance of the ozone layer?
A. It plays an important role in the greenhouse effect.
B. It reflects solar gamma reaction that would otherwise reach
Earth’s surface.
C. It acts as an insulator for the earth and helps to maintain a
livable temperature.
D. It absorbs incoming UV rays.
E. It reflects incoming heat back into space.
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UNEQUAL HEATING OF EARTH
Factor 1: Variation in Sun’s Angle
Because of Earth’s spherical shape, sunlight strikes the
earth at a perpendicular angle only at the equator. As you
move away from the equator, the sun’s rays hit the earth at a
more oblique angle. When the angle is more oblique, the
sunlight must travel a longer distance through the
atmosphere. This allows for a lot of energy to be absorbed
by the atmosphere, leaving little to hit the earth. Near the
equator, sunlight travels only a short distance through the
atmosphere, less energy is absorbed, and more energy is left
to hit the earth.
Practice:
_____ What region of the earth does the sun hit at the most
direct angle?
A. North Pole (90 N)
D. 30-60 S
B. South Pole (90 S)
E. Equator (0)
C. 30-60 N
_____ Which of the following is not true about the sun’s
energy heating the earth?
A. The sun’s rays hit the earth at different angles depending
on the latitude.
B. The sun’s rays are concentrated over a smaller surface area
at the equator than they are in higher latitudes.
C. The polar regions reflect more sunlight than the tropical
regions.
D. The sun’s rays are more strongly reflected in the lower
latitude regions.
E. The unequal heating helps to determine an area’s climate.
http://astro.unl.edu/naap/motion1/animations/se
asons_ecliptic.html
Factor 2: Angle of incidence
Air is heated much more at the equator, where the sun’s
rays strike directly, than at the poles, where sunlight strikes at
an angle and spreads out over a much larger area. These
differences in energy input help explain why tropical regions
near the equator are hot, why polar regions are cold, and
why temperate regions in between generally have warm and
cool temperatures.
The intense input of solar radiation in tropical regions
leads to greatly increased evaporation of moisture from
forests, grasslands, and bodies of water. As a result, tropical
regions normally receive more precipitation than other areas
of Earth.
Use the above website to manipulate the sun and Earth to determine the
cause of the seasons.
June marks Summer in the Northern hemisphere draw. Draw
the relationship of the sun and Earth during this time. (Shapes
not to scale). Draw North America, include the tilt of the axis
of Earth (you can use a line through the poles), draw a line to
represent the equator, shade the part of Earth that is in
“darkness” and include arrows to indicate solar radiation
hitting Earth from the sun.
Sun
Factor 3: Albedo
We will discuss later
EARTH’S TILT AND SEASONS
The earth is tilted 23.5° on its axis. The North Pole is
always pointed toward the North Star. During the spring
equinox (first day of spring), the equator (0° latitude) is
facing directly toward the sun. In this “neutral” position, the
equator is getting the most direct sunlight and the rest of the
earth is getting indirect sunlight. (Reread the Unequal
Heating of Earth summary if necessary.) Six months later, at
the autumn equinox, the earth is in the same position except
on the opposite side of its revolution around the sun.
During summer and winter, the northern hemisphere is
tilted either toward (summer) or away from (winter) the sun.
This means during our summer, our angle of incidence is
higher and therefore we receive more energy per unit area
and experience a higher average temperature. The opposite
is true for our winter when we are tilted away from the sun.
Because the earth is only tilted 23.5° and we are at 40° N,
December marks Summer in the Northern hemisphere draw.
Draw the relationship of the sun and Earth during this time.
(Shapes not to scale). Follow the same directions from above
Sun
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we never get the sun’s most direct rays. During our summer,
the direct rays shine on 23.5° N latitude, the Tropic of
Cancer. During our winter, the direct rays shine on 23.5° S
latitude, the Tropic of Capricorn. The area between these
two tropics (equatorial region) is always receiving a lot of
concentrated solar energy and stays warm year round. But
since the warmest area shifts, so does the rain (formed when
warm air rises, cools, and releases water as precipitation).
Areas just north and south of the equator stay warm but may
experience dry seasons during their respective winters.
A common misconception is that the earth is closer to
the sun in the summer and farthest from the sun in the
winter. Actually, Earth’s perihelion (peri=near, helios=sun)
occurs around January 3. Earth’s aphelion (apo=away)
occurs around July 4. The difference between these two
distances is only about 5 million kilometers (about 3% of the
distance to the sun), not enough to affect temperature.
Earth’s tilt and its effect on the angle of incidence is the
determining factor when it comes to seasons.
_____ Which area on earth would experience 24 hours of
daylight in December?
A. The Arctic Circle
B. Greenland
C. Amazon Rainforest
D. Antarctica
E. Australia
_____The primary cause of Earth’s seasons is the
A. Constant tilt of Earth’s rotational axis with respect to
the plane of its orbit around the Sun
B. Changing distance of Earth from the Sun at different
times of the year
C. Periodic wobbling of Earth on its axis of rotation
D. Changing relative positions of Earth, its Moon and
the Sun
E. Periodic changes in solar energy output
_____ What latitude receives the most direct sunlight
throughout the year?
A. 90° N
B. 30°-60° N
C. 0°
D. 30°-60° S
E. 90° S
EARTH’S ROTATION AND THE CORIOLIS EFFECT
In the northern hemisphere, large air masses generally appear to curve clockwise and in the southern hemisphere, they
appear to curve counterclockwise. This curving pattern is a result of the earth’s rotation in an eastward direction as winds
move above the surface. The apparent curvature of object traveling long distances on Earth is known as the Coriolis effect.
On a global scale, this effect produces steady, reliable wind patterns, such as the trade winds and mid-latitude Westerlies.
Ocean currents also experience the Coriolis effect and curve clockwise in the northern hemisphere and counterclockwise in
the southern hemisphere.
Imagine you are in space looking down at the North Pole (the center of your field of view). As the earth spins on its axis,
the North Pole is moving much slower than the equator because it’s a much smaller area. In 24 hours a point near the North
or South Pole (Point A) will not travel nearly as far as a point near the equator (Point B).
An object (like a large mass of air or water) traveling from Point B to Point A will be moving faster than the middle
portion of the hemisphere and will end up to the right of Point A. The same object traveling from A to B will be moving
slower than Point B and will land behind Point B. Both examples show a clockwise (to the
right) curve according to the point of origination. The same effect is seen in the southern
hemisphere, with object appearing to curve counterclockwise (to the left) according to the
direction they came from.
Large masses of air, moving long distances, like Earth’s atmospheric convection cells
are influenced by the Coriolis effect. This is seen in the world’s prevailing winds. The six
major wind belts (formed by the six convection cells) all curve clockwise in the northern
hemisphere and counterclockwise in the southern hemisphere. The winds on either side of
the equator are the Northeast and Southeast trade winds. From 30°-60° are the Westerlies.
At the North and South Pole are the polar easterlies. Winds are always named for the
direction they come from.
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Watch the following video about the Coriolis Effect:
https://www.youtube.com/watch?v=i2mec3vgeaI
If you (hypothetically) threw a paper airplane North from
Texas what is the most likely place it would land:
A. California
B. Nebraska
C. Delaware
D. Mexico
Practice
_____ Which of the following statements about the Coriolis
Effect is incorrect?
A. The Coriolis effect causes object to be deflected to the
right in the northern hemisphere.
B. The Coriolis effect causes objects to be deflected
clockwise in the southern hemisphere.
C. Global winds are not affected by the Coriolis effect.
D. The Coriolis effect is caused by the rotation of the earth.
E. The different rotation speeds of Earth at different
latitudes causes the deflection of traveling objects.
An object moving from the Equator south would move to the
___________ (assuming you were facing South)
_____ The Coriolis effect and prevailing winds contribute to
the formation of gyres in the oceans. Which direction do
Identify the hemisphere of the hurricane pictures below
these gyres flow in the Northern Hemisphere?
(Northern or Southern Hemisphere)
A. North to South
D. Counterclockwise
B. South to North
E. East to West
C. Clockwise
_____ A plane leaves the North Pole. Initially, it flies directly
south towards point B on the diagram. Which is the most
likely landing site for the plane if it maintains a straight path
to the south? A, B, C, or D?
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ATMOSPHERIC CONVECTION CURRENTS
Four properties of air influence its movement around the world.
1. Density. Warm air is less dense so it rises. Cool air is denser so it sinks.
2. Water Vapor Capacity. Warm air can hold more water vapor than cold air. This helps explain why summer days in
Indiana are hot and humid and winter days are cold and dry. The maximum amount of water vapor that air can hold
is called its saturation point. The saturation point is higher for warm air because it can hold more water. Conversely,
the saturation point is lower for cool air because it can hold less water. As air cools, the saturation point lowers and
the air can’t hold any more water vapor. The water vapor will condense and leave the air as precipitation.
3. Adiabatic Cooling/Heating. As air rises, the pressure lowers. This allows molecules to move further apart (and
collide less), cooling the temperature of the air. When air sinks, the pressure rises, causing molecules to collide more
and the temperature to rise. This forced change in temperature because of change in pressure is called adiabatic
cooling or heating.
4. Latent Heat Release. When water evaporates (liquid to gas) a tiny amount of energy is stored. This energy is known
as latent heat. The latent heat will be released when the opposite process occurs and the water condenses into a liquid.
Whenever precipitation is forming and latent heat is being released, the air will warm and rise.
Because the earth is heated unevenly, some areas experience
the warm, less dense, wet, rising air and some areas experience
cool, denser, dry, sinking air. The warmest air is found near the
equator (in the intertropical convergence zone) where heat
from the sun is most direct. This solar energy evaporates ocean
water and transfers heat from the oceans to the atmosphere.
Once the air has cooled and released precipitation, it will sink
back down as cooler, drier air. This continuous cycle of rising
and falling air creates large convection currents of air around
the earth. Along with rising and falling air, air moves across the
surface of the earth from areas of high pressure to areas of low
pressure. This continual displacement and replacement of air
forms large convection cells.
Hadley cells are convection cells north and south of the equator. Polar cells are convection cells at the north and south
pole. In the area between (where we live) air circulates based on the Hadley and polar cells but does not form a strong
convection cell. This is partly why we experience a variety of different weather conditions, even during the same season.
Watch the video lecture to help you label the
diagram (you might have to Google as well):
http://www.bozemanscience.com/ap-es-004-theatmosphere
On the diagram to the left draw and label the
following:
- High and Low Pressure
- Hadley Cells (with arrows)
- Westerlies
- Easterlies
- Ferrel Cells (with arrows)
- Polar Cells (with arrows)
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Practice
_____ What is the best explanation for the high amounts of
rain that occur at the equator?
A. This area experiences a high amount of wind, which leads to
storms and rain.
B. This area has a large amount of water, leading to more rain.
C. The warm air rises at the equator and condenses at a high
altitude, leading to rain.
D. The low pressure system that develops here causes warm air
_____ What is the overall direction of global air currents to sink, leading to rain.
E. As the air rises, it becomes warmer, leading to more rain.
at the equator?
A. Air rises at the equator.
_____ What type of weather would you expect to find at the
B. Air sinks at the equator.
intertropical convergence zone (ITCZ)?
C. Air moves horizontally to the north at the equator.
A. Dry and warm weather
D. Air moves horizontally to the south at the equator.
B. Dry and cool weather
E. Air is relatively stable at the equator.
C. Warm and rainy weather
D. Cool and rainy weather
E. Warm in the summer and cool in the winter
_____ What happens to air as it rises?
A. The pressure decreases and it expands in volume.
B. The pressure increases and it expands in volume.
C. The pressure decreases and it decreases in volume.
D. The pressure increases and it decreases in volume.
E. The pressure and volume remain constant.
____ Which of the following statements is correct?
A. Warm air rises as 60° latitude and sinks at 30° latitude
B. Warm air rises at 90°latitudue and continues to rise at
60° latitude
C. Warm air rises at the equator and sinks at 30° latitude
D. Cold air rises at the equator and sinks at 30° latitude
E. Cold air rises at 30° latitude and sinks and 60° latitude
OCEAN CURRENTS
Along with unequal heating of the earth, atmospheric convection currents, the rotation of the earth and the Coriolis
effect, and Earth’s orbit around the sun on a tilted axis, Earth’s weather and climate are also influenced by the circulation of
surface and deep ocean waters.
Sunlight warms the ocean’s surface but does not penetrate deeply, so ocean water is warmest at the surface and becomes
colder with depth. Surface waters receiving more solar radiation at the equator are warmer than surface waters in temperate
or polar regions. Like air, warm water is less dense than cool water. This leads to a heavy layer of cold, salty, sinking water
under a lighter, warmer, less salty layer.
The high heat capacity of water allows it to absorb a lot of solar radiation and remain relatively stable in temperature. By
absorbing and releasing heat to the atmosphere, the oceans regulate Earth’s climate. Oceans also influence climate by moving
heat from place to place via surface circulation.
Large-scale ocean currents (gyres) are driven by temperature, prevailing winds, and gravity. Surface currents flow
horizontally great distances across the globe, curving according to the Coriolis effect and the location of continents.
Equatorial ocean currents carry warm water to cooler regions. Cool water currents carry water from high latitude regions or
from deep in the ocean. Surface currents like the Gulf Stream are rapid and powerful, bringing warm water from the Gulf of
Mexico to Europe, moderating the continent’s climate, which would otherwise be much colder.
Surface winds and heating also create vertical currents in the ocean. Upwelling, the upward movement of cold, deep water
toward the surface, occurs where horizontal currents diverge or flow away from one another. Cold, upwelled water is rich in
nutrients and generally high in productivity. Deep in the ocean, vertical currents create rising and falling convection cells, like
those in the air.
The worldwide current system in which warmer, fresher water moves along the surface and colder, saltier water moves
deep beneath the surface is known as thermohaline circulation. Scientists hypothesize that melting of Greenland’s ice sheet,
because of climate change, may make North Atlantic waters less salty and less likely to sink. This change could trigger a
shutdown of thermohaline circulation, causing temperate areas like Europe to rapidly cool.
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Practice
_____ What is one major role that these
gyres play in global climate?
A. Currents redistribute heat from the
North to the South
B. Currents redistribute heat from the
Equator to Northern latitudes
C. Drive global wind patterns in the
Northern hemisphere
D. Contribute to the Coriolis effect
E. Currents redistribute tropical moisture
_____ If Northern glaciers melted between
Europe and Greenland, what consequence
may occur?
A. Water in the northern hemisphere
would become saltier, causing it to
sink
B. Water would become less salty,
preventing sinking
C. Water would become warmer,
preventing sinking
D. Water would become more dense
and sink to a lower depth
E. Water would sink faster, speeding
up the current
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THE RAIN SHADOW EFFECT
Many of the processes that affect weather and climate
occur on a global scale, but local features, like topography (the
shape of the land) also play a role. Climbing in elevation causes
a much more rapid change in climate than moving the same
distance toward the poles. There is a distinct change in
vegetation along mountain slopes that corresponds with this
altitude-induced climate change.
When large masses of air encounter mountain ranges, the
air is forced upwards. This rising air experiences the same
changes as rising air at the equator: it cools, expands, releases
water vapor as precipitation, and decreases in pressure. All the
rain on this (windward) side of the mountain range often leads
to lush vegetation. By the time the air flows over the mountain
and back down the other side, it has released most of its water
and is very dry. The warm, dry, arid side is called the leeward
side and is known as the rain shadow region.
This rain shadow effect can be seen in the Sierra Nevada
range in the Western United States. Look at the graph below.
Notice how precipitation rises on the windward side of each
mountain range and falls on the leeward side of each mountain
range.
Practice
_____ The rain shadow effect can have a large effect on
local climate. When the rain shadow effect is occurring,
which side of the mountain tends to receive more rain?
A. Windward side
B. Leeward side
C. Top of the mountain
D. Foot of the mountain
E. Side of the mountain that does not face the ocean
_____ Which of the following statements explains the
rain shadow effect?
A. Mountains force air to rise; air cools and releases
moisture as it rises.
B. The atmosphere gets denser as elevation increases,
causing snow to fall.
C. Temperatures are higher on one side of a mountain
than the other.
D. Wind patterns cause precipitation
E. Lush vegetation on one side of a mountain causes it to
rain more on this side
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