Earth Science, 12e Rocks: Materials of the Solid Earth Chapter 3.
Earth Science, 12e
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Transcript of Earth Science, 12e
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Earth Science, Earth Science, 12e12e
The Atmosphere: The Atmosphere: Composition, Structure, Composition, Structure,
and Temperatureand TemperatureChapter 16Chapter 16
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Weather and climate Weather and climate
Weather • Weather is over a short period of time • Constantly changing
Climate• Climate is over a long period of time • Generalized composite of weather
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Weather and climateWeather and climate
Elements of weather and climate • Properties that are measured regularly • Most important elements
• Temperature• Humidity• Cloudiness• Precipitation• Air Pressure• Wind speed and direction
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Composition of the Composition of the atmosphereatmosphere
Air is a mixture of discrete gasesMajor components of clean, dry air
• Nitrogen (N2) – 78%
• Oxygen (O2) – 21%
• Argon and other gases • Carbon dioxide (CO2) – 0.038% – absorbs
heat energy from Earth
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Proportional volume of Proportional volume of gases that compose dry airgases that compose dry air
Figure 16.4
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Composition of the Composition of the atmosphereatmosphere
Variable components of air • Water vapor
• Up to about 4% of the air’s volume• Forms clouds and precipitation• Absorbs heat energy from Earth
• Aerosols• Tiny solid and liquid particles • Water vapor can condense on solids• Reflect sunlight• Help color sunrise and sunset
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Composition of the Composition of the atmosphereatmosphere
Variable components of air • Ozone
• Three atoms of oxygen (O3)
• Distribution not uniform • Concentrated between 10 to 50 kilometers
above the surface • Absorbs harmful UV radiation • Human activity is depleting ozone by adding
chlorofluorocarbons (CFCs)
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Structure of the atmosphere Structure of the atmosphere Pressure changes
• Pressure is the weight of the air above • Average sea level pressure
• Slightly more than 1,000 millibars• About 14.7 pounds per square inch
• Pressure decreases with altitude • One-half of the atmosphere is below 3.5 miles
(5.6 km) • Ninety percent of the atmosphere is below 10
miles (16 km)
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Figure 16.6
Atmospheric pressure variation
with altitude
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Structure of the atmosphere Structure of the atmosphere Atmospheric layers based on
temperature • Troposphere
• Bottom layer• Temperature decreases with altitude – called
the environmental lapse rate • 6.5˚C per kilometer (average)• 3.5˚F per 1,000 feet (average)
• Thickness varies – average height is 12 km• Outer boundary is named the tropopause
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Structure of the atmosphere Structure of the atmosphere Atmospheric layers based on
temperature • Stratosphere
• About 12 km to 50 km • Temperature increases at top• Outer boundary is named the stratopause
• Mesosphere • About 50 km to 80 km• Temperature decreases• Outer boundary is named the mesopause
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Structure of the atmosphere Structure of the atmosphere
Atmospheric layers based on temperature • Thermosphere
• No well-defined upper limit• Fraction of atmosphere’s mass • Gases moving at high speeds
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Thermal structure of Thermal structure of the atmospherethe atmosphere
Figure 16.8
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Earth–Sun relations Earth–Sun relations
Earth motions • Rotates on its axis• Revolves around the Sun
Seasons• Result of
• Changing Sun angle • Changing length of daylight
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Daily paths of the Sun at Daily paths of the Sun at 4040º N latitudeº N latitude
Figure 16.10 A
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Relationship of Sun angle Relationship of Sun angle and solar radiation received and solar radiation received
Figure 16.11
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Earth–Sun relations Earth–Sun relations Seasons
• Caused by Earth’s changing orientation to the Sun
• Axis is inclined 23½º • Axis is always pointed in the same direction
• Special days (Northern Hemisphere) • Summer solstice
• June 21–22 • Sun’s vertical rays are located at the Tropic
of Cancer (23½º N latitude)
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Relationship of Sun angle to Relationship of Sun angle to the path of solar radiation the path of solar radiation
Figure 16.12
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Earth–Sun relations Earth–Sun relations Seasons
• Special days (Northern Hemisphere) • Winter solstice
• December 21–22 • Sun’s vertical rays are located at the Tropic
of Capricorn (23½º S latitude)• Autumnal equinox
• September 22–23• Sun’s vertical rays are located at the
Equator (0º latitude)
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Earth–Sun relations Earth–Sun relations Seasons
• Special days (Northern Hemisphere) • Spring (Vernal) equinox
• March 21–22• Sun’s vertical rays are located at the
Equator (0º latitude)
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EarthEarth––Sun relationshipsSun relationships
Figure 16.13
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Characteristics of the Characteristics of the solstices and equinoxessolstices and equinoxes
Figure 16.14
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Atmospheric heating Atmospheric heating Heat is always transferred from warmer
to cooler objects Mechanisms of heat transfer
• Conduction through molecular activity • Convection
• Mass movement within a substance • Usually vertical motions
• Radiation (electromagnetic radiation) • Velocity: 300,000 kilometers (186,000 miles)
per second in a vacuum
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Mechanisms of heat transferMechanisms of heat transfer
Figure 16.17
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Atmospheric heating Atmospheric heating Mechanisms of heat transfer
• Radiation (electromagnetic radiation) • Consists of different wavelengths
• Gamma (very short waves)• X-rays • Ultraviolet (UV) • Visible• Infrared• Microwaves and radio waves
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The electromagnetic The electromagnetic spectrumspectrum
Figure 16.18
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Atmospheric heating Atmospheric heating Mechanisms of heat transfer
• Radiation (electromagnetic radiation) • Governed by basic laws
• All objects, at whatever temperature, emit radiation
• Hotter objects radiate more total energy per unit area than do cooler objects
• The hotter the radiating body, the shorter the wavelength of maximum radiation
• Objects that are good absorbers of radiation are good emitters as well
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Atmospheric heating Atmospheric heating Incoming solar radiation
• Atmosphere is largely transparent to incoming solar radiation
• Atmospheric effects• Reflection – albedo (percent reflected)• Scattering• Absorption
• Most visible radiation reaches the surface • About 50% absorbed at Earth’s surface
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Average distribution of Average distribution of incoming solar radiationincoming solar radiation
Figure 16.20
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Atmospheric heating Atmospheric heating Radiation from Earth’s surface
• Earth reradiates radiation (terrestrial radiation) at the longer wavelengths
• Longer wavelength terrestrial radiation is absorbed by
• Carbon dioxide and • Water vapor in the atmosphere • Lower atmosphere heated from Earth’s surface
• Heating of the atmosphere is termed the greenhouse effect
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The heating of The heating of the atmospherethe atmosphere
Figure 16.22
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Temperature measurement Temperature measurement
Daily maximum and minimumOther measurements
• Daily mean temperature • Daily range• Monthly mean• Annual mean• Annual temperature range
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Mean monthly temperatures Mean monthly temperatures for two locations in Canadafor two locations in Canada
Figure 16.27
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Mean monthly temperatures for Mean monthly temperatures for two coastal locationstwo coastal locations
Figure 16.29
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Temperature measurement Temperature measurement Human perception of temperature
• Anything that influences the rate of heat loss from the body also influences the sensation of temperature
• Important factors are• Air temperature• Relative humidity• Wind speed• Sunshine
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Controls of temperature Controls of temperature Temperature variationsReceipt of solar radiation is the most
important controlOther important controls
• Differential heating of land and water • Land heats more rapidly than water • Land gets hotter than water• Land cools faster than water • Land gets cooler than water
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Controls of temperature Controls of temperature
Other important controls • Altitude• Geographic position• Cloud cover• Albedo
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World distribution World distribution of temperature of temperature
Temperature maps • Isotherm – a line connecting places of
equal temperature• Temperatures are adjusted to sea level • January and July are used for analysis
because they represent the temperature extremes
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World distribution World distribution of temperature of temperature
Global temperature patterns • Temperature decreases poleward from the
tropics • Isotherms exhibit a latitudinal shift with the
seasons • Warmest and coldest temperatures occur
over land
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World distribution World distribution of temperature of temperature
Global temperature patterns • In the Southern Hemisphere
• Isotherms are straighter • Isotherms are more stable
• Isotherms show ocean currents • Annual temperature range
• Small near equator • Increases with an increase in latitude • Greatest over continental locations
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World mean sea-level World mean sea-level temperatures in Januarytemperatures in January
Figure 16.32
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World mean sea-level World mean sea-level temperatures in Julytemperatures in July
Figure 16.33