Chapter 17
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![Page 1: Chapter 17](https://reader035.fdocuments.in/reader035/viewer/2022062704/5559196bd8b42a3d028b4ea8/html5/thumbnails/1.jpg)
Chapter 17
The Atmosphere: Structure and Temperature
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Weather is …… The state of the atmosphere at any
time and place is. The combination of Earth’s motions
and energy from the sun produce a variety of weather.
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Climate is….based on observations of weather that
have been collected over many years.
Climate helps describe a place or region.
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Composition of the Atmosphere Earth’s early atmosphere was much
different. Volcanic activity provided most of
the original gases. Oxygen didn’t start to accumulate
about 2.6 billion years ago.
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The atmosphere continuously exchanges materials with the ocean and life on Earth.
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Major Components
Air is a…..
A. compoundB. Mixture
MIXTURE
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Air is mostly gas with a few variable components.
Gases include: Nitrogen – 78% Oxygen – 22% The remaining 1% includes: Argon - .93% CO2 - .039% - Although only a small amount, this
gas absorbs energy given off by Earth. This is very important in heating the
atmosphere.
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Variable Components
These components vary from time to time and from place to place…….
Variable components include: Water vapor Dust Ozone
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These components can have significant effects on weather and climate.
The water vapor varies from almost none to about 4% by volume.
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Why is this small amount so significant?
Water vapor is the source of all clouds and precipitation.
It also absorbs heat given off by the Earth and absorbs some solar energy.
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Movements of the atmosphere allow a large quantity of solid and liquid particles to be suspended within it.
Microscopic dust can stay in the atmosphere for many years.
Example: Volcanic dust may stay in the atmosphere for 100 years.
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Other substances include: Sea salts Fine soil blown into the atmosphere Smoke Soot Pollen Microorganisms
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Ozone – is a form of oxygen that combines three oxygen atoms (O3) into each molecule.
REMEMBER: This is not the form of oxygen we breathe.
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Ozone is not evenly distributed. It is concentrated about 10-50 km above the Earth’s surface.
At this altitude 02 is split into single atoms when they absorb ultraviolet radiation.
Ozone forms from the collision of single oxygen atoms with a molecule of 02.
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Ozone is crucial to life on Earth. Imagine what Earth would like if all
the sun’s ultra-violet radiation was not filtered out.
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The Changing Hole in the Ozone Layer
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Human Influence Air pollutants are airborne particles and
gases that occur in large enough quantities to endanger the health of organisms.
Primary pollutants include: CO – 49.1% Nitrogen oxides – 14.8% Volatile organics – 13.6% Sulfur oxides – 16.4% Particulates – 6%
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Sources include: transportation fuel combustion industrial processes solid waste disposal
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Secondary pollutants form in the atmosphere when reactions occur between primary pollutants.
Example: After sulfur dioxide enters the atmosphere it combines with oxygen to form sulfur trioxide. Sulfur trioxide combines with water to form H2SO4 or sulfuric acid.
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Example: Some reactions are triggered by sunlight and are called photochemical reactions.
When nitrogen oxides absorb solar energy a chain of complex reactions begins.
If certain volatile organic compounds are present, secondary products form that are reactive, irritating, and toxic….. smog
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Height and Structure of the Atmosphere The atmosphere thins as you travel
away from Earth until there are too few gas molecules to measure.
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Pressure Changes Atmospheric pressure is simply the weight
of the atmosphere. At sea level the average air pressure is
just over 1000 millibars (14.7 lbs/in2). One half of the atmosphere lies below the
altitude of 5.6 kilometers. Above 100 kilometers, only .00003% of
the gases exist. Therefore, as you gain altitude there is
less air pressure.
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Temperature Changes Most of the time temperature
decreases with altitude. The atmosphere can be divided into
four vertical layers
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Earth – Sun Relationships How much of the sun’s energy
actually reaches the Earth? One – two billionth. This energy is not evenly distributed,
it varies with latitude, time of day, and season of the year.
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This uneven heating causes the winds and drives the ocean currents.
Think of how ocean currents try to even the distribution of heat around the Earth (Oceanography again?)
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Earth’s Motions The Earth rotates once is about 24
hours. It orbits the sun at about 113,000
km/hr in an elliptical orbit.
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Earth’s Orientation Seasonal changes occur because the Earth is
tilted 23.50. The constant movement of the Earth causes
solar noon to vary up to 470.Example: New York City has a maximum solar
angle 0f 73.50. As you can see the sun is never actually straight
(900) overhead. This occurs on June 21st. Six months later solar noon reaches a minimum
of 26.50.
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Solstices and Equinoxes
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Length of Day The farther north you are from the
equator on the summer solstice, the longer the period of daylight. When your reach the Arctic Circle, at 66.5 degrees N. latitude the length of daylight is 24 hours.
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Arctic Summer
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Heating the Atmosphere The concept of heat is often
misunderstood…. Heat is the energy transferred from one
object to another because of a difference in their temperatures.
Temperature is the measure of the average kinetic energy of the individual atoms or molecules in a substance
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When energy is transferred to the gas atoms and molecules in air, those particles move faster and air temperature rises.
When air transfers energy to a cooler object, its particles move slower, and air temperature drops.
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Energy Transfer as Heat Three mechanisms of energy transfer as
heat are: Conduction – is the transfer of heat
through matter by molecular activity. Good conductors include metals. Air is a
poor conductor of heat. Conduction only occurs between the air
and the Earth’s surface that is direct contact with the air.
For the atmosphere, conduction is the least important mechanism of heat transfer.
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Convection – is the transfer of heat by mass movement or circulation with in a substance.
Convection takes place in fluids like the ocean and air where the atoms and molecules are free to move about.
Convection also occurs in solids that behave like fluids like materials in the mantle.
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Electromagnetic Radiation All forms of light that originates at
the sun form the electromagnetic spectrum.
All forms and wavelengths of light travel at a speed of 300,000 km/sec.
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Radiation – travels out in all directions for its source.
Radiant energy can travel through the vacuum of space.
Solar energy reaches Earth by? radiation
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Four laws the govern radiation:1. All objects, at any temperature,
emit radiant energy. The sun, the Earth, the poles2. Hotter objects radiate more total
energy per unit area than colder objects do.
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3. The hottest radiating bodies produce the shortest wavelengths of maximum radiation.
The sun emits energy with the visible light range while Earth emits light in the infrared range.
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4. Objects that are good absorbers of radiation are good emitters as well.
The atmosphere does not absorb certain wavelengths or radiation, but is a good absorber of other wavelengths.
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Write a small description that explains how this water is being heated… You must include the terms you think heat the water like radiation, conduction, and convectionSend via email or bring in a hard copy.
Now that you are an expert on heat transfer…………….
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What Happens To Solar Radiation? When radiation strikes an object,
there are usually three different results:
1. Some energy is absorbed by the object.
When absorption occurs radiant energy is converted to heat energy.
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2. Substances such as water and air are transparent to certain wavelengths of radiation.
Energy that is transmitted does not contribute energy to the object.
3. Some radiation may bounce off the object without being absorbed or transmitted.
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Reflection and Scattering Reflection occurs when light
bounces off an object. The reflected radiation has the same
intensity as the incident radiation. Scattering produces a large number
of weaker rays that travel in different directions.
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About 30% of the radiant energy that reaches Earth’s atmosphere is reflected back into space.
This energy is lost and does not heat the Earth or its atmosphere.
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Some dust particles and gas molecules scatter some incoming radiation in all directions.
This is how some light reaches beneath a shade tree.
Scattering also accounts for the brightness and even the color of the atmosphere.
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Absorption About 50% of the energy that strikes the
top of the atmosphere reaches the Earth’s surface and is absorbed.
Most of this energy is reradiated skyward. Since the Earth is cooler than the sun it
emits longer wave radiation in the infrared range.
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The atmosphere efficiently absorbs the longer wavelengths emitted by the Earth.
Water vapor and carbon dioxide are major absorbing gases.
When a gas molecule absorbs light waves, this energy is transformed into molecular motion that can be detected as a rise in temperature.
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This energy can be: Radiated away Reabsorbed by other gas molecules Absorbed by the EarthThis phenomenon has been termed
the greenhouse effect.
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Temperature Controls
Why Temperature Varies includes: 1. Latitude 2. Variation in the angle of sunlight 3. Heating land and water 4. Altitude 5. Geographic position 6. Cloud cover 7. Ocean currents
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Land and Water Different land surfaces absorb varying
amounts of incoming solar radiation. The largest contrast is between land and
water. Land heats more rapidly to higher
temperatures than water. Land also cools more rapidly and to lower
temperatures that water.
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Therefore, temperature variations are considerably greater over land than water.
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61% of the Northern hemisphere is covered by water and 39 % land.
81% of the Southern hemisphere is covered by water and 29% land.
Which hemisphere has smaller annual temperature variations?
The Southern hemisphere
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Geographic position Compare the east coast of the U.S.
with the west coast of England. England has cooler summers and
milder winters.
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Seattle and Spokane, Washington – temperature variation occurs because of a mountain range.
Seattle has a more marine influence. Spokane is separated from the
ocean by the Cascade Range and has a more continental influence and larger temperature variation.
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Altitude Temperatures tend to drop with
altitude.
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Cloud Cover and Albedo Albedo is the fraction of total
radiation that is reflected by any surface.
Many clouds have a high Albedo, and therefore reflect a significant portion of the sunlight that strikes them back in space.
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The extent of cloud cover influences temperatures in the lower atmosphere.
At night clouds have the opposite effect. Clouds act like a blanket by absorbing outgoing radiation emitted by the Earth and reradiating a portion of it back to the surface.
Cloudy nighttime temperatures don’t drop and much as clear night temperatures.
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The effect of cloud cover is to reduce the daily temperature range by lowering the daytime maximum and raising the nighttime minimum.
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World Distribution of Temperatures Isotherms - are lines on a weather
map that connect points that have the same temperature.
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World Records
Highest temperature ever recorded on Earth was 590C.
It occurred on September 13, 1922, at Aziza, Libya in North Africa’s Sahara Desert.
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Lowest temperature ever recorded on Earth was –890C.
It occurred on August 24, 1960, at Antarctica.