Transcript Chapter 11 Heating the Atmosphere Earth’s Unique Atmosphere  No other planet in our solar system has an atmosphere with the exact mixture of gases or.

Chapter 11
Heating the
Atmosphere
Earth’s Unique Atmosphere

No other planet in our solar system
has an atmosphere with the exact
mixture of gases or the heat and
moisture conditions necessary to
sustain life as we know it.
Introduction of Weather


Weather influences our everyday
activities, our jobs, and our health
and comfort.
Many of us pay little attention to
the weather unless we are
inconvenienced by it or when it
adds to our enjoyment outdoors.
Weather Continued
(Severe weather events)






United States has the greatest
variety of weather of any country
in the world.
Tornadoes
Flash Floods
Intense Thunderstorms
Hurricanes
Blizzards
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
Weather and Climate
 Elements of weather and climate
 Properties that are measured
regularly
 Most important elements
 Temperature
 Humidity
 Cloudiness
 Precipitation
 Air Pressure
 Winds speed and direction
Composition of
the Atmosphere
 Air is a mixture of discrete gases
 Major components of clean, dry air




Nitrogen (N)—78%
Oxygen (O2)—21%
Argon and other gases
Carbon dioxide (CO2)—0.036%—
absorbs heat energy from Earth
Composition of Dry Air
Composition of
the Atmosphere
 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
Composition of
the Atmosphere
 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)
Chlorofluorocarbons (CFCs)


Over the past half century, people have
unintentionally placed the ozone layer in
jeopardy by polluting the atmosphere.
Many uses developed for CFCs
•
•
•
•
Coolants for AC
Refrigeration equipment
Cleaning solvents for electronic components and
comp. chips
Propellants for aerosol sprays
Characteristics of CFCs




Practically inert, not chemically
active in the lower atmosphere
Gradually make their way to the
ozone layer
Sunlight separates the chemicals
into their constituent atoms
Chlorine atoms released, breaking
up some of the ozone molecules
Importance of Ozone


Ozone filters out most of the UV radiation from
the Sun
Decreased concentration allows more of these
harmful wavelengths to reach Earth’s surface




Increase risks of skin cancer
Impair the human immune system
Promote cataracts, clouding of the eye lens that
reduces vision. May cause blindness if not treated
Montreal Protocol was developed under the
sponsorship of the UN to eliminate the
production and use of CFCs
Structure of
the Atmosphere
 Pressure changes
 Atmospheric Pressure is the weight of
the air above
 Average sea level pressure
 Slightly more than 1000 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)
Atmospheric
Pressure
Variation
with
Altitude
Figure 11.5
Structure of
the Atmosphere
 Atmospheric layers based on
temperature
 Troposphere
 Bottom layer, where all weather phenomena
occur
 Temperature decreases with altitude—Called the
environmental lapse rate
 6.5˚C per kilometer (average)
 3.5˚F per 1000 feet (average)
 Thickness varies with latitude and season—
Average height is about 12 km
 Outer boundary is named the tropopause
Structure of
the Atmosphere
 Atmospheric layers based on
temperature
 Stratosphere
 About 12 km to 50 km
 Temperature increases at top due to ozone
absorbing UV radiation from the sun
 Outer boundary is named the stratopause
 Mesosphere
 About 50 km to 80 km
 Temperature decreases
 Outer boundary is named the mesopause
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
Temperatures in the
Thermosphere




Increases with altitude, absorption of very
shortwave high-energy solar radiation by
atoms of oxygen and nitrogen
Rising to extreme values of more than 1000
degrees Celsius
Temperature is defined in term of average
speed at which molecules move
Sparse amount of gases = insignificant
quantity of heat
Thermal Structure of
the Atmosphere
Figure 11.7
Earth–Sun Relations
 Earth’s two principal motions
 Rotates on its axis, an imaginary line running
through the poles
 One rotation/24 Hrs.
 Cycle of daylight and darkness
 Revolves around the Sun
 Hundred years ago, most people believed Earth was
stationary, Sun/stars revolved around Earth
 Fact: Traveling at more than 107,000 km/hr orbiting
about the sun
 Seasons
 Result of
 Changing Sun angle
 Changing length of daylight
Seasons
 Result of
 Changing Sun angle
 At around 90 degrees angle, the solar rays are more
concentrated
 At a lesser angle, the solar rays are more spread
out, and therefore less intense solar radiation that
reaches the surface
 Thickness of atmosphere, lower the angle, the more
distance the rays have to penetrate
 The longer the path, the greater the chances that
sunlight will be absorbed, reflected, or scattered by
the atmosphere, reduce intensity at the surface
 Changing length of daylight
 Longer the day, the more solar radiation the Earth
takes in
Daily Paths of the Sun
at 40° N latitude—June
Figure 11.9 A
Daily paths of the Sun at
40° N latitude—December
Figure 11.9 B
Relationship of Sun Angle and
Intensity of Solar Radiation
Figure 11.10
Earth–Sun Relations
 Seasons
 Caused by Earth's changing
orientation to the Sun
 Axis is inclined 23½°
 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 (23½° N latitude)
Earth–Sun relations
 Seasons
 Special days (Northern Hemisphere)
 Winter solstice
 December 21–22
 Sun's vertical rays are located at the
tropic of Capricorn (23½° S latitude)
 Autumnal equinox
 September 22–23
 Sun's vertical rays are located at the
equator (0° latitude)
Earth–Sun relations
 Seasons
 Special days (Northern Hemisphere)
 Spring equinox
 March 21–22
 Sun's vertical rays are located at the
equator (0° latitude)
Earth–Sun Relationships
Characteristics of the
Solstices and Equinoxes
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
 Radiation (electromagnetic radiation)
 Velocity: 300,000 kilometers (186,000
miles) per second in a vacuum
Conduction





Transfer of heat through matter by molecular
activity
Energy of molecules is transferred through
collisions from one molecule to another, heat
flowing from high to low temp.
Metals are good conductors
Air is a very poor conductor of heat
Conduction is the least significant of the three
as a means of heat transfer for the
atmosphere
Convection


Most of the heat transport that occurs in the
atmosphere is carried on by convection.
Def: The transfer of heat by mass movement
or circulation within a substance


Takes place in fluids (oceans, air) where atoms
and molecules are free to move about
Pan example:



Warmer water rises, cooler water sinks
Uneven heating of water, from the bottom up
Water will continue to “turn over”, producing a
convective circulation
Radiation



Travels in all directions from its source
Travels through the vacuum of space,
does not need medium like the other
two
Radiation is the heat-transfer
mechanism by which solar energy
reaches our planet
Mechanisms of
Heat Transfer
Figure 11.14
Atmospheric Heating
 Mechanisms of heat transfer
 Radiation (electromagnetic radiation)
 Consists of different wavelengths (distance from
one crest to the next)
 Gamma (very short waves)
 X-rays
 Ultraviolet (UV)
 Visible
 The only portion of the spectrum we can
see
 White Light as a mixture of colors, each
corresponding to a particular wavelength
seen through a prism
 Infrared (detected as heat)
 Microwaves and radio waves (longest)
The Electromagnetic
Spectrum
Figure 11.15
Atmospheric Heating
 Mechanisms of heat transfer
 Radiation (electromagnetic radiation)
 Governed by basic laws
 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
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
Average Distribution of
Incoming Solar Radiation
Figure 11.17
Atmospheric Heating
 Radiation from Earth's surface
 Earth re-radiates radiation (terrestrial
radiation) at the longer wavelengths
 Longer wavelength terrestrial
radiation is absorbed by
 Carbon dioxide and water vapor
 Lower atmosphere is heated from Earth's
surface
 Heating of the atmosphere is termed
the greenhouse effect
Greenhouse effect


Approx. 50% of the solar energy that strikes the top
of the atmosphere reaches Earth’s surface and is
absorbed
Most of this energy is then reradiated skyward





The radiation that it emits has longer wavelengths than solar
radiation (terrestrial radiation)
The atmosphere is an efficient absorber of this type of
radiation (85% absorbed)
Water vapor and CO2 are the principal absorbing gases
The absorbed terrestrial radiation is then reradiated back to
Earth
Atmosphere acts like a real Greenhouse (with windows
open)
Heating of the Atmosphere
Figure 11.19
Global Warming




Carbon dioxide in the atmosphere absorbs some of
the radiation emitted by Earth and thus contributes
to the greenhouse effect
Changes in content of CO2 could influence air
temperature
Rapid growth of industrialization, burning of fossil
fuels has added vast quantities of CO2 to the
atmosphere
The clearing of forests also contributes substantially.
Carbon dioxide is released as vegetation is burned or
decays
Consequences of Global
Warming?





Probable rise in sea level?
Shifts in the paths of large-scale storms, affecting the
distribution of precipitation and the occurrence of
severe weather
Stronger tropical storms
Increases in the frequency and intensity of heat
waves and droughts
Gradual environmental shift, imperceptible to public.
Nevertheless will have a strong impact on future
economics and thus leading to social and political
consequences.
Temperature Measurement
 Daily maximum and minimum
 Other measurements





Daily mean temperature
Daily range
Monthly mean
Annual mean
Annual temperature range
Controls of Temperature
 Temperature variations
 Receipt of solar radiation is the
most important control
 Other 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
Maritime Influence
on Temperature
Figure 11.23
Controls of Temperature
 Other important controls




Altitude
Geographic position
Cloud cover
Albedo
Clouds
Reduce the
Daily
Temperature
Range
Figure 11.27
World Distribution
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
World Distribution
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
World Distribution
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
World Mean Sea-Level
Temperatures in January
Figure 11.28
World Mean Sea-Level
Temperatures in July
Figure 11.29
End of Chapter 11