Download Chapter 22 Complete Notes

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Chapter 22 Teacher Notes - Atmosphere
Lesson 1 - Composition of the Atmosphere
Atmosphere is a mixture of gases that surrounds a planet, such as Earth.
The most abundant elements in air are the gases nitrogen (78%), oxygen (21%), and argon (0.9%).
Composition of the Atmosphere
In addition to containing gaseous elements and compounds CO² and H²O.
The atmosphere also carries various kinds of tiny solid particles, such as dust and pollen.
History of the Atmosphere
Prior to 3.5 billion years ago, primitive Earth was devoid of an atmosphere, which means lighter gases like
hydrogen and helium would escape Earth’s gravity due to the Sun's radiation.
Earth’s first atmosphere was formed by volcanic outgassing of gases trapped in the interior of the early Earth like
water vapor (H²O), nitrogen, ammonia, methane, argon, sulfur dioxide and carbon dioxide.
Most scientist except the theory that the early atmosphere was probably dominated at first by water vapor, which,
as the temperature dropped, would rain out and form the oceans.
This would have been a deluge of truly global proportions an resulted in further reduction of CO².
Then the atmosphere was dominated by nitrogen, but there was certainly no oxygen in the early atmosphere.
Our oxygen will come from early Cynobacteria (blue-green algae -stromatolites), splitting molecules of H²O and
CO² through photosynthesis and recombining them into organic compounds and molecular oxygen (O²) about 2
billion years ago.
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Oxygen in the Atmosphere
Oxygen makes up about 21% of Earth’s atmosphere.
Land and ocean plants produce large quantities of oxygen in a process called photosynthesis.
Nitrogen of the Atmosphere
Nitrogen makes up about 78% of Earth’s atmosphere and is maintained through the nitrogen cycle.
Nitrogen is removed from the air mainly by the action of nitrogen-fixing bacteria.
Decay releases nitrogen back into the atmosphere.
Water in our Atmosphere
As water evaporates from oceans, lakes, streams, and soil, it enters air as the invisible gas water vapor.
Plants and animals give off water vapor during transpiration, one of their processes.
Water Role in our Atmosphere
As water vapor enters the atmosphere, it is removed by the processes of condensation and precipitation thus
completing the Water Cycle.
Atmospheric Pressure
Atmospheric pressure is the force per unit area that is exerted on a surface by the weight of the atmosphere.
Gravity holds the gases of the atmosphere near Earth’s surface and as a result, the air molecules are compressed
together and exert force on Earth’s surface.
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Atmospheric pressure is exerted equally in all directions—up, down, and sideways.
Earth’s gravity keeps 99% of the total mass of the atmosphere within 20 miles of Earth’s surface.
Because the pull of gravity is not as strong at higher altitudes, the air molecules are farther apart and exert less
pressure on each other at higher altitudes.
At sea level, the air pressure is about 14.7 pounds per square inch.
As your altitude increases (for example, if you climb a mountain), the air pressure decreases.
At an altitude of 10,000 feet, the air pressure is 10 pound per square inch (and there is less oxygen to breathe).
Lesson 2 - Layers of the Atmosphere
In general, air pressure and density decrease in the atmosphere as height increases.
However, temperature has a more complicated profile with altitude.
Earth's atmosphere has a distinctive pattern of temperature changes with increasing altitude and allow scientist to
indentify five main layers.
The five main layers of the atmosphere from top to bottom are the
5th Layer – the Exosphere.
4th Layer – the Thermosphere
3rd Layer- the Mesophere
2nd Layer- the Stratosphere
1st layer – the Troposphere
1st layer - The Troposphere
The Troposphere is the layer closest to Earth’s surface.
From the extreme desert temperature’s of over a 120° F, the temperature drops at a constant rate as altitude
increases to a low of (-)76° F.
The most important fact to the troposphere is that almost all of the water vapor for weather and carbon dioxide in
the atmosphere is found in this layer.
From the ground up to the top of this layer is about 10 miles in height and from there the temperature stops
decreasing.
This part of the layer is called the tropopause and represents the upper boundary of the troposphere.
2nd Layer - The Stratosphere
The second layer of the atmosphere is the stratosphere.
The temperature at the bottom of the stratosphere starts at about -76°F and increases as attitude increases to a
high of 32°F.
The second later if the atmosphere starts at about 10 miles high and goes up to an altitude of 30 miles, which
means it is twice the size of the troposphere.
Commercial airliners typically cruise in the lower reaches of the stratosphere at altitudes of 30,000–39,000 ft.
This optimizes fuel burn, drag on the airframe and allows them to stay above extreme turbulence and weather.
Ozone Layer
The stratosphere is the most important layer in our atmosphere because it contains a thick 10 mile layer of ozone,
which absorbs harmful ultraviolet radiation from the sun.
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It is made up of three oxygen atoms - O³, unlike the air we breathe which is O².
This process started about a 1.0 billion years ago when ozone gas began to form in the stratosphere through the
process known as the ozone-oxygen cycle.
The cycle occurs when short-wavelength UV light from the sun hits a molecule of oxygen gas.
Light has so much energy that it breaks the oxygen bond holding the atoms together, thus creating two
oxygen atoms (O² = O + O).
From there the single atoms of oxygen (O) combined with remaining oxygen (O²) to form ozone (O³) molecules.
Ozone Layer Damage
The ozone layer is located at the bottom of the stratosphere and then extends upward for about 10 miles.
The ozone layer is very effective at absorbing UV rays, in fact it is considered a “greenhouse gas”.
The ozone layer is a mixture of our major atmospheric gases (N² and O²) along with the O³ molecules.
Invented in the 1920s, CFCs found in hair sprays and aerosol cans proved to be an exceptional problem for ozone,
because many of these synthetic chemicals can persist for decades, allowing them to make their way into the upper
atmosphere.
In that rarefied air, ultraviolet light breaks the molecular bonds in CFCs and free chlorine atoms get released.
Chlorine then destroys ozone molecules by "stealing" their oxygen atoms.
Scientists had theorized since the 1970’s about the chemistry that could lead to ozone depletion.
In May 1985 scientists with the British Antarctic Survey shocked the world when they announced the discovery of a
huge hole in the ozone layer over Antarctica.
In 1987, delegates from around the world signed the Montreal Protocol designed to protect the ozone layer by
phasing out the production of a number of substances believed to be responsible for ozone depletion.
Today the ozone hole, which was first spotted 25 years ago, appears headed for a happy ending, thanks to
international action.
Some scientists project that by 2080 global ozone will return to 1950’s levels.
Lesson #3 The Mesosphere (3), Thermosphere (4) and Exosphere (5)
The Mesosphere is the third layer to our atmosphere or middle layer.
The mesosphere starts at about 30 miles and goes up to about 50 miles high.
As you get higher up in the mesosphere, the temperature gets colder.
Temperature ranges from 32°F at the bottom to about a -150°F at the top making this the coldest place on Earth.
Scientists know less about the mesosphere than about other layers of the atmosphere because it is hard to study.
Weather balloons and jet planes cannot fly high enough to reach the mesosphere and the orbits of satellites are
above the mesosphere.
What we do know is that millions of meteors enter the atmosphere, an average of 40 tons per day.
Within the mesosphere most melt or vaporize as a result of collisions with the air particles contained there.
(4) The Thermosphere
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The thermosphere is the 4th layer of the atmosphere and in this layer temperatures increases as the altitude
increases.
It is the largest layer of the atmosphere as is spans from 50 miles above ground to 400 miles.
Ionosphere
The lower region of the thermosphere, at an altitude of 50 miles to 250 miles, is commonly called the ionosphere.
The ionosphere is the region where Earth’s atmosphere blends into the almost complete vacuum of space.
Thermosphere
The ionosphere is distinguished because it is ionized by solar radiation and forms the inner edge of
the magnetosphere.
It is the ionosphere and the interactions between solar radiation that causes the phenomena known as auroras.
The temperatures leave the -130°F and go up to 400°F.
Reasons for Aurora’s
The aurora’s are cause when the massive amounts of electrons emitted from the Sun are carried by the solar
winds.
They are then attracted in by our magnetism at the poles where they then crash into our atmosphere.
When the electrons collide with the oxygen and nitrogen atoms, the atoms are ionized, and this ionization causes
the atoms to become excited and emit photons of light.
This reaction can be seen elsewhere including Jupiter.
(4) Thermosphere
Although part of Earth's atmosphere, the air density is so low in this layer that most of the thermosphere is what we
normally think of as outer space which is 62 miles above.
Much of the X-ray and UV radiation from the Sun is absorbed in the thermosphere which is why most satellites and
the space station orbit within the thermosphere.
Orbit Height ISS, Space Shuttle and Satellites
The ISS is maintained at an orbital altitude of between 205 miles and 255 miles and completes 15.7 orbits per day.
The Space Shuttle's orbital altitude, normally ranged from 190 miles to 330 miles above sea level, depending on its
mission.
Not all are found in the thermosphere, some satellites are put into geostationary orbits like the Direct TV new D12
satellite, which orbits about 22,000 miles above Earth.
To an observer on the rotating Earth, satellites will appear stationary in the sky at their respective locations.
(4) Thermosphere
Solar activity strongly influences temperatures in the thermosphere with temperatures leaving the 400°F ionosphere
and going all the way up to about 1000°F.
From there temperatures in the upper thermosphere then explode from about 1000°F to 3,600°F or higher.
However temperature is actually tricky here because there are only a few molecules that are present in the
thermosphere.
Temperature is a measurement of the mean kinetic energy , or average speed of motion, of a molecule.
Which means even though the measured temperature is very hot, if you exposed your skin to the thermosphere,
the perceived temperature would be very cold because there are so few molecules present.
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(5) Exosphere
The exosphere is the 5th and final layer of the atmosphere.
The exosphere observable from space as the geocorona is seen to extend to at least 62,000 miles from the surface
of the Earth.
However, the upper boundary of the exosphere can be defined theoretically by the altitude about 120,000 miles,
half the distance to the Moon, at which the influence of solar radiation pressure on atomic hydrogen velocities
exceeds that of the Earth’s gravitational pull.
Lesson #4 Radiation
All of the energy that Earth receives from the sun travels through space as radiation.
Radiation is the transfer of heat energy without the involvement of a physical substance in the transmission.
Electromagnetic spectrum refers to all of the frequencies or wavelengths of electromagnetic radiation.
The various types of radiation differ in the length of their wavelength and the amount of energy carried within their
wavelength.
Electromagnetic radiation can be described in terms of a stream of photons, which are mass-less particles each
traveling in a wave-like pattern and moving at the speed of light.
Each photon contains a certain amount (or bundle) of energy.
The only difference between the various radiation is the amount of energy found in the photons.
Any type of electromagnetic energy can be transformed into thermal energy.
Thus, any electromagnetic radiation can "heat" a material when it is absorbed.
If we were to compare water flow to the electromagnetic spectrum, radio waves & microwaves would be
comparable to a mist of water.
The photons that create infrared, visible light and ultraviolet radiation would be comparable to a water hose of
water.
X-rays and gamma-ray radiation would be comparable to a fire hose of water.
All of the high-energy Gamma rays, X-rays and high energy UV radiation are absorbed by our atmosphere well
above our heads.
What we receive in the troposphere is:the low energy UV radiation, visible light and short wave Infrared along with
longer wave radio waves.
Hubble Space Telescope
Hubble Space Telescope/Spitzer Space Telescope composite image of the Sombrero Galaxy in visible and infrared
light.
This composite of data from NASA's Chandra X-ray Observatory and Hubble Space Telescope for NGC 6543,
better known as the Cat's Eye nebula.
Lesson 5 Energy Heat Transfer and Greenhouse Gasses
Essentially 100% of the energy that fuels the earth comes from the sun.
To maintain a constant global average temperature, all of the sun’s radiation that enters Earth’s atmosphere must
eventually be sent back to space.
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This is achieved through Earth’s energy balance.
There are three ways energy can be transferred between the earth's surface and the atmosphere:
1)Convection
2)Conduction
3)Radiation.
Convection
Convection is heat transfer by the movement of mass from one place to another.
In the atmosphere, convection includes large- and small-scale rising and sinking of air masses and smaller air
parcels.
Conduction
Conduction is the transfer of energy as heat from one substance to another by direct contact with matter.
Since air is a poor conductor, most energy transfer by conduction occurs right at the earth's surface.
During the day, solar radiation heats the ground, which heats the air next to it by conduction.
At night, the ground cools and the colder ground cools the air around it by conduction (sometimes cool enough to
create a fog).
There are three ways to heat the atmosphere or anything else, for that matter.
There are three ways to cook popcorn.
1. Microwave a bag of popcorn.
2. Cook it in a pan of oil.
3. Place the popcorn in the popper.
Each of these methods of cooking popcorn is really an example of the three ways heat can be transferred.
Which is which? Write to correct response to each of the three ways listed above.
Absorption of Infrared Energy
Of all the sunlight that passes through the atmosphere annually, only about 50% is available at the Earth's surface
to do work.
This 50% of energy is used to:
Heat the Earth's surface and lower atmosphere,
Melt and evaporate water
Run photosynthesis in plants.
Of the other approx. 50%:
4% is reflected back to space by the Earth's surface
26% is scattered or reflected to space by clouds and atmospheric particles
19% is absorbed by atmospheric gases, particles, and clouds.
Lesson #6 The Atmosphere and Solar Energy
There are three atmospheric processes that can modify the solar radiation passing through our atmosphere
destined to the Earth's surface.
1) Absorption
2) Scattering
3) Reflection
Absorption
Absorption is defined as a process in which solar radiation is retained by a substance and converted into heat
energy.
Scattering
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The process of scattering occurs when solar radiation is sent in random directions without any change to the
wavelength of the electromagnetic energy.
Scattering does reduce the amount of incoming radiation reaching the Earth's surface.
Reflection
Reflection is a process where sunlight is redirect by 180° after it strikes an atmospheric particle.
In this process, the solar radiation striking an atmospheric particle is redirected back to space unchanged.
Most of the reflection in our atmosphere occurs in clouds when light is intercepted by particles of liquid and frozen
water.
Albedo Effect
Reflectivity of the surface is often described by the term surface albedo.
The Earth's average albedo, reflectance from both the atmosphere and the surface, is about 30%.
The reflectivity or albedo of the Earth's surface varies with the type of material that covers it.
For example, fresh snow can reflect up to 95% of the insulation that reaches it surface.
The Greenhouse Effect
The greenhouse effect refers to process where visible light energy from the sun pass through glass or our
atmosphere and is absorbed but the infra-red heat energy created from the ground because trapped by the glass or
our atmosphere.
This greenhouse effect occurs because light is a shorter wavelength.
When light energy is absorbed it is turned into infra-red energy which has a longer wavelength and can no longer
escape the way it entered.
The Greenhouse Effect in a Car
Bright sunlight will effectively warm your car on a cold, clear day by the greenhouse effect.
The longer infrared wavelengths radiated by sun-warmed objects do not pass readily through the glass.
The entrapment of this energy warms the interior of the vehicle making it very uncomfortable to enter are stay in.
The Greenhouse Effect
The greenhouse effect has been widely used to describe the trapping of excess heat by the rising concentration
of carbon dioxide in the atmosphere.
The carbon dioxide strongly absorbs infrared and does not allow as much of it to escape into space.
Increases in the Greenhouse Gasses
Carbon dioxide is not the only “greenhouse gas”.
Gas molecules in the Earth's atmosphere with three or more atoms are called "greenhouse gases" because they
can capture outgoing infrared energy from the Earth, thereby warming the planet.
The greenhouse gases include:
(1) water vapor with three atoms (H2O),
(2) ozone (O3),
(3) carbon dioxide (CO2), and
(4) methane (CH4).
Current analysis suggests that the combustion of fossil fuels is a major contributor to the increase in the carbon
dioxide in our atmosphere.
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Climate Change
Because the potential consequences of climate change in terms of loss of snow cover, change in weather patterns,
change in the deep thermohaline current, etc., are so great, it is a major societal concern.
Essentially any kind of tabulation you access will tell the same story.
The temperature has gradually risen over the last 150 years.
The statistics are not what is disputed, the dispute is over how much of an effect humankind is having on the
atmosphere and how much of this is just nature taking its course.
The potential impact both economically and politically combined with the ambiguities of the science has given rise
to many passionate extremes.
Lesson #7 Atmospheric Circulation
Pressure differences in the atmosphere cause the movement of air worldwide.
The air near Earth’s surface generally flows from the poles toward the equator and this is because cold air sinks
(forming a high pressure) and wants to replace the hotter (lower pressure) air.
Coriolis Effect
As the air circulates it is affected by another factor the Coriolis effect.
The Coriolis effect is a force acting on winds causing them to curve because the Earth is spinning.
Why Does the Coriolis Effect, Affect the Ocean Currents
If the Earth did not rotate and remained stationary, the atmosphere would circulate between the poles (high
pressure areas) and the equator (a low pressure area) in a simple back-and-forth pattern.
But because the Earth rotates, circulating air is deflected.
Instead of circulating in a straight pattern, the air deflects and curves.
In the Northern Hemisphere to the right.
In the Southern Hemisphere to the left.
This deflection is called the Coriolis effect.
Global Winds
Each hemisphere contains three looping patterns of flow called convection cells.
Each convection cell correlates to an area of Earth’s surface, called a wind belt, that is characterized by winds that
flow in one direction.
Three Types of Prevailing Winds
These wind belts are called prevailing winds.
There are three types of prevailing winds:
1) Trade Winds
2) Westerlies
3) Polar Easterlies
Trade Winds (Equatorial Winds)
Named from their ability to quickly propel trading ships across the ocean, the trade winds between about 30°
latitude and the equator are steady and blow about 11 to 13 miles per hour in both hemispheres.
In the Northern Hemisphere, the trade winds flow the northeast and are called the northeast trade winds.
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In the Southern Hemisphere, they are the southeast trade winds.
Westerlies
Westerlies are prevailing winds that blow from west to east between 30º and 60º latitude in both hemispheres.
Between 30º and 60º latitude, some of the descending air moving toward the poles is deflected by the Coriolis
effect.
In the Northern Hemisphere, the westerlies are the southwest winds.
In the Southern Hemisphere, they are the northwest winds.
Polar Easterlies
Polar Easterlies prevailing winds that blow from east to west between 60° and 90° latitude in both hemispheres
Surface winds created by the polar high pressure are deflected by the Coriolis effect and become the polar
easterlies.
Duldrums
Sailors noticed the stillness of the rising (and not blowing) air near the equator and gave the region the depressing
name "doldrums."
The doldrums, are located between 5° north and 5° south of the equator.
In this warm zone, most air movement is upward and produces some of the world's heaviest precipitation regions
including the Amazon Forest.
Horse Latitudes
Horse latitudes are two belts of latitude where winds are light and the weather is hot and dry.
They are located at about 30° latitude and create some of the great deserts on Earth including Death Valley.
This occurs because air is an area can go either way - as part of the prevailing trade winds or toward the poles as
part of the Westerlies.
Ships in the horse latitudes would often become be-calmed in mid-ocean, thus severely prolonging the voyage.
Lesson 8 Winds and Pressure Shifts
As the sun’s rays shift northward and southward during the changing seasons of the year, the positions of the
pressure belts and wind belts shift.
This small change causes some areas of Earth’s surface to be in different wind belts during different times of the
year.
Jet Streams
Jet Streams are a narrow band of strong winds that blow in the upper troposphere.
These winds exist in the Northern and Southern Hemisphere.
There are two major jet streams: polar jet streams and the higher and weaker subtropical jet streams.
The wind speeds vary according to the temperature gradient, but typically measure anywhere from 50 mph on up to
250 mph.
They are important because they affect the path of storms and airline routes.
Pan Am Airlines
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The location of the jet stream is extremely important for aviation.
Commercial use of the jet stream began on 11-18-52, when Pan Am flew from Tokyo to Honolulu at an altitude
25,000 ft.
It cut the trip time by over one-third, from 18 to 11.5 hours.
Not only does it cut time off the flight, it also nets fuel savings.
California’s Place in the Atmosphere
California is located in the northern hemisphere above 30°N latitude.
This puts California within the prevailing westerlies wind belt.
Winds generally blow from the west, off the Pacific Ocean, to the east.
Temperature Inversion
Temperature Inversion is the layering of warm air on top of cool air.
Inversion occurs because warm air, which is less dense than cool air, traps cool air beneath it.
Temperature Inversion Pollution
Certain weather conditions can make air pollution worse.
In some areas, topography may make air pollution even worse by keeping the polluted inversion layer from
dispersing.
Take for example Los Angeles, where warm desert air will trap cooler air against the mountains.
Under these conditions air cannot circulate up and away from an area.
This condition along with the trapping of exhaust from cars, boats and trains can produce smog, a general term for
air pollution that indicates a combination of smoke and fog.
Santa Ana Winds
Santa Ana winds are dry and warm (often hot) winds in the Southern California area that blow in from the desert.
This condition tends to occur during the winter half-year when the high deserts tend to cool more quickly then the
Los Angeles (LA) Basin.
These winds actually start out as cool desert air.
When high pressure builds over the the high sesert, air flows clockwise around high pressure systems.
That clockwise flow, along with the attraction for cool air to want to sink pushes air into the L.A. Basin from the
northeast (Lancaster) and the east (Hesperia).
Why are Santa Ana Winds Hot and Dry
The Great Basin (High Deserts) resides at a higher elevation than the LA Basin, thus, the Santa Ana’s flow
downslope.
When air descends, it is compressed, and dries as its temperature rises.
The Santa Ana wind tends to have very low relative humidity (RH), often registering below 10%.
This combination creates a Red Flag Warning issued by the US National Weather Service to inform area firefighting
and land management agencies that conditions are ideal for wildland fire ignition and propagation.
Variations in Temperature
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The highest temperatures of the day are usually recorded mid- to late afternoons and not all places have the
same temperature.
There are 3 major reasons for these variations and they include:
(1) Latitude
(2) Season
(3) Proximity to water
Latitude
Latitude is the primary factor that affects the amount of solar energy that reaches any point on Earth’s surface.
Because Earth is a sphere, the sun’s rays do not strike all areas at the same angle.
The energy that reaches the equator is more intense than the energy that strikes the poles, so average
temperatures are higher near the equator than near the poles.
Season
Temperature varies seasonally because of the tilt of Earth’s axis.
As the Earth revolves around the sun the portion of Earth’s surface that receives the most sunlight changes.
For part of the year (Summer) the northern hemisphere is tilted toward the sun and receives more direct sunlight
then the southern hemisphere.
The elliptical motion around the sun results in the change of seasons for the two hemispheres.
Proximity to Water
Because water vapor stores heat through conduction, the amount of water in the air affects the temperature of a
region.
Land areas close to large bodies of water generally have more moderate temperatures.
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