earth science, 12e the atmosphere: composition, structure, and temperature chapter 16
TRANSCRIPT
Earth Science, 12eEarth Science, 12e
The Atmosphere: The Atmosphere: Composition, Structure, Composition, Structure,
and Temperatureand TemperatureChapter 16Chapter 16
Weather and climate Weather and climate
Weather Weather • Weather is over a short period of time Weather is over a short period of time • Constantly changingConstantly changing
ClimateClimate• Climate is over a long period of time Climate is over a long period of time • Generalized composite of weather Generalized composite of weather
Weather and climateWeather and climate
Elements of weather and climate Elements of weather and climate • Properties that are measured regularly Properties that are measured regularly • Most important elementsMost important elements
• TemperatureTemperature• HumidityHumidity• CloudinessCloudiness• PrecipitationPrecipitation• Air PressureAir Pressure• Wind speed and directionWind speed and direction
Composition of the Composition of the atmosphereatmosphere
Air is a mixture of discrete gasesAir is a mixture of discrete gases Major components of clean, dry air Major components of clean, dry air
• Nitrogen (NNitrogen (N22) – 78%) – 78%
• Oxygen (OOxygen (O22) – 21%) – 21%
• Argon and other gases Argon and other gases • Carbon dioxide (COCarbon dioxide (CO22) – 0.038% – absorbs ) – 0.038% – absorbs
heat energy from Earth heat energy from Earth
Proportional volume of Proportional volume of gases that compose dry airgases that compose dry air
Figure 16.4
Composition of the Composition of the atmosphereatmosphere
Variable components of air Variable components of air • Water vapor Water vapor
• Up to about 4% of the air’s volumeUp to about 4% of the air’s volume• Forms clouds and precipitationForms clouds and precipitation• Absorbs heat energy from Earth Absorbs heat energy from Earth
• AerosolsAerosols• Tiny solid and liquid particles Tiny solid and liquid particles • Water vapor can condense on solidsWater vapor can condense on solids• Reflect sunlightReflect sunlight• Help color sunrise and sunset Help color sunrise and sunset
Structure of the atmosphere Structure of the atmosphere
Pressure changes Pressure changes • Pressure is the weight of the air above Pressure is the weight of the air above • AverageAverage sea level pressuresea level pressure
• Slightly more than 1,000 millibarsSlightly more than 1,000 millibars• About 14.7 pounds per square inch About 14.7 pounds per square inch
• Pressure decreases with altitude Pressure decreases with altitude • One-half of the atmosphere is below 3.5 miles One-half of the atmosphere is below 3.5 miles
(5.6 km) (5.6 km) • Ninety percent of the atmosphere is below 10 Ninety percent of the atmosphere is below 10
miles (16 km) miles (16 km)
Structure of the atmosphere Structure of the atmosphere Atmospheric layers based on Atmospheric layers based on
temperature temperature • TroposphereTroposphere
• Bottom layerBottom layer• Temperature decreases with altitude – called Temperature decreases with altitude – called
the the environmental lapse rateenvironmental lapse rate • 6.5˚C per kilometer (average)6.5˚C per kilometer (average)• 3.5˚F per 1,000 feet (average)3.5˚F per 1,000 feet (average)
• Thickness varies – average height is 12 kmThickness varies – average height is 12 km• Outer boundary is named the Outer boundary is named the tropopausetropopause
Structure of the atmosphere Structure of the atmosphere Atmospheric layers based on Atmospheric layers based on
temperature temperature • StratosphereStratosphere
• About 12 km to 50 km About 12 km to 50 km • Temperature increases at topTemperature increases at top
• Outer boundary is named the Outer boundary is named the stratopausestratopause • MesosphereMesosphere
• About 50 km to 80 kmAbout 50 km to 80 km• Temperature decreasesTemperature decreases• Outer boundary is named the Outer boundary is named the mesopause mesopause
Structure of the atmosphere Structure of the atmosphere
Atmospheric layers based on Atmospheric layers based on temperature temperature • ThermosphereThermosphere
• No well-defined upper limitNo well-defined upper limit• Fraction of atmosphere’s mass Fraction of atmosphere’s mass
• Gases moving at high speeds Gases moving at high speeds
Earth–Sun relations Earth–Sun relations
Earth motions Earth motions • RotatesRotates on its axison its axis• RevolvesRevolves around the Sunaround the Sun
SeasonsSeasons• Result ofResult of
• Changing Sun angle Changing Sun angle • Changing length of daylight Changing length of daylight
Relationship of Sun angle to Relationship of Sun angle to the path of solar radiation the path of solar radiation
Figure 16.12
Relationship of Sun angle Relationship of Sun angle and solar radiation received and solar radiation received
Figure 16.11
Earth–Sun relations Earth–Sun relations SeasonsSeasons
• Caused by Earth’s changing orientation to Caused by Earth’s changing orientation to the Sunthe Sun• Axis is inclined 23½º Axis is inclined 23½º • Axis is always pointed in the same direction Axis is always pointed in the same direction
• Special days (Northern Hemisphere) Special days (Northern Hemisphere) • Summer solstice Summer solstice
• June 21–22 June 21–22 • Sun’s vertical rays are located at the Sun’s vertical rays are located at the Tropic Tropic
of Cancerof Cancer (23½º N latitude) (23½º N latitude)
Earth–Sun relations Earth–Sun relations SeasonsSeasons
• Special days (Northern Hemisphere) Special days (Northern Hemisphere) • Winter solsticeWinter solstice
• December 21–22 December 21–22 • Sun’s vertical rays are located at the Sun’s vertical rays are located at the Tropic Tropic
of Capricornof Capricorn (23½º S latitude) (23½º S latitude)• Autumnal equinox Autumnal equinox
• September 22–23September 22–23• Sun’s vertical rays are located at the Sun’s vertical rays are located at the
EquatorEquator (0º latitude) (0º latitude)
Earth–Sun relations Earth–Sun relations
SeasonsSeasons• Special days (Northern Hemisphere) Special days (Northern Hemisphere)
• Spring (Vernal) equinoxSpring (Vernal) equinox • March 21–22March 21–22• Sun’s vertical rays are located at the Sun’s vertical rays are located at the
EquatorEquator (0º latitude) (0º latitude)
Characteristics of the Characteristics of the solstices and equinoxessolstices and equinoxes
Figure 16.14
Atmospheric heating Atmospheric heating Heat is always transferred from warmer Heat is always transferred from warmer
to cooler objects to cooler objects Mechanisms of heat transfer Mechanisms of heat transfer
• ConductionConduction through molecular activity through molecular activity • ConvectionConvection
• Mass movement within a substance Mass movement within a substance • Usually vertical motions Usually vertical motions
• RadiationRadiation (electromagnetic radiation) (electromagnetic radiation) • Velocity: 300,000 kilometers (186,000 miles) Velocity: 300,000 kilometers (186,000 miles)
per second in a vacuum per second in a vacuum
Atmospheric heating Atmospheric heating Mechanisms of heat transfer Mechanisms of heat transfer
• Radiation Radiation (electromagnetic radiation) (electromagnetic radiation) • Consists of different wavelengths Consists of different wavelengths
• Gamma (very short waves)Gamma (very short waves)• X-rays X-rays • Ultraviolet (UV) Ultraviolet (UV) • VisibleVisible• InfraredInfrared• Microwaves and radio wavesMicrowaves and radio waves
Atmospheric heating Atmospheric heating Mechanisms of heat transfer Mechanisms of heat transfer
• Radiation Radiation (electromagnetic radiation) (electromagnetic radiation) • Governed by basic laws Governed by basic laws
• All objects, at whatever temperature, emit All objects, at whatever temperature, emit radiation radiation
• Hotter objects radiate more total energy per Hotter objects radiate more total energy per unit area than do cooler objects unit area than do cooler objects
• The hotter the radiating body, the shorter The hotter the radiating body, the shorter the wavelength of maximum radiationthe wavelength of maximum radiation
• Objects that are good absorbers of radiation Objects that are good absorbers of radiation are good emitters as well are good emitters as well
Atmospheric heating Atmospheric heating Incoming solar radiation Incoming solar radiation
• Atmosphere is largely transparent to Atmosphere is largely transparent to incoming solar radiation incoming solar radiation
• Atmospheric effectsAtmospheric effects• Reflection – albedoReflection – albedo (percent reflected) (percent reflected)• ScatteringScattering• Absorption Absorption
• Most visible radiation reaches the surface Most visible radiation reaches the surface • About 50% absorbed at Earth’s surface About 50% absorbed at Earth’s surface
Average distribution of Average distribution of incoming solar radiationincoming solar radiation
Figure 16.20
Atmospheric heating Atmospheric heating Radiation from Earth’s surface Radiation from Earth’s surface
• Earth reradiates radiation (terrestrial Earth reradiates radiation (terrestrial radiation) at the longer wavelengths radiation) at the longer wavelengths
• Longer wavelength terrestrial radiation is Longer wavelength terrestrial radiation is absorbed by absorbed by • Carbon dioxide and Carbon dioxide and • Water vapor in the atmosphere Water vapor in the atmosphere • Lower atmosphere heated from Earth’s surface Lower atmosphere heated from Earth’s surface
• Heating of the atmosphere is termed the Heating of the atmosphere is termed the greenhouse effectgreenhouse effect
Temperature measurement Temperature measurement
Daily maximum and minimumDaily maximum and minimum Other measurementsOther measurements
• Daily mean temperature Daily mean temperature • Daily rangeDaily range• Monthly meanMonthly mean• Annual meanAnnual mean• Annual temperature rangeAnnual temperature range
Mean monthly temperatures Mean monthly temperatures for two locations in Canadafor two locations in Canada
Figure 16.27
Mean monthly temperatures for Mean monthly temperatures for two coastal locationstwo coastal locations
Figure 16.29
Temperature measurement Temperature measurement Human perception of temperature Human perception of temperature
• Anything that influences the rate of heat Anything that influences the rate of heat loss from the body also influences the loss from the body also influences the sensation of temperature sensation of temperature
• Important factors areImportant factors are• Air temperatureAir temperature• Relative humidityRelative humidity• Wind speedWind speed• SunshineSunshine
Controls of temperature Controls of temperature Temperature variationsTemperature variations Receipt of solar radiation is the most Receipt of solar radiation is the most
important controlimportant control Other important controlsOther important controls
• Differential heating of land and water Differential heating of land and water • Land heats more rapidly than water Land heats more rapidly than water • Land gets hotter than waterLand gets hotter than water• Land cools faster than water Land cools faster than water • Land gets cooler than water Land gets cooler than water
Controls of temperature Controls of temperature
Other important controlsOther important controls • AltitudeAltitude• Geographic positionGeographic position• Cloud coverCloud cover• AlbedoAlbedo
World distribution World distribution of temperature of temperature
Temperature mapsTemperature maps • IsothermIsotherm – a line connecting places of – a line connecting places of
equal temperatureequal temperature• Temperatures are adjusted to sea level Temperatures are adjusted to sea level • January and July are used for analysis January and July are used for analysis
because they represent the temperature because they represent the temperature extremes extremes
World distribution World distribution of temperature of temperature
Global temperature patterns Global temperature patterns • Temperature decreases poleward from the Temperature decreases poleward from the
tropics tropics • Isotherms exhibit a latitudinal shift with the Isotherms exhibit a latitudinal shift with the
seasons seasons • Warmest and coldest temperatures occur Warmest and coldest temperatures occur
over land over land
World distribution World distribution of temperature of temperature
Global temperature patterns Global temperature patterns • In the Southern Hemisphere In the Southern Hemisphere
• Isotherms are straighter Isotherms are straighter • Isotherms are more stable Isotherms are more stable
• Isotherms show ocean currents Isotherms show ocean currents • Annual temperature range Annual temperature range
• Small near equator Small near equator • Increases with an increase in latitude Increases with an increase in latitude • Greatest over continental locations Greatest over continental locations
World mean sea-level World mean sea-level temperatures in Januarytemperatures in January
Figure 16.32