Earth
Science, 10th edition
Chapter
15: The Atmosphere: Composition,
Structure, and Temperature
I. Weather and climate
A. Weather
1. Weather is over a short period
of time
2. Constantly changing
B. Climate
1. Climate is over a long period of
time
2. Generalized, composite of
weather
C. Elements of weather and climate
1. Properties that are measured
regularly
2. Most important elements
a. Temperature
b. Humidity
c. Cloudiness
d. Precipitation
e. Air pressure
f.
Wind speed and direction
II. Composition of the atmosphere
A. Air is a mixture of discrete gases
B. Major components of clean, dry air
1. Nitrogen (N) – 78%
2. Oxygen (O2) – 21%
3. Argon and other gases
4. Carbon dioxide (CO2)
– 0.036% – absorbs heat energy from Earth
C. Variable components of air
1. Water vapor
a. Up
to about 4% of the air's volume
b. Forms clouds and
precipitation
c. Absorbs heat energy from
Earth
2. Aerosols
a. Tiny solid and liquid
particles
b. Water vapor can condense on
solids
c. Reflect sunlight
d. Help color sunrise and
sunset
3. Ozone
a. Three atom oxygen (O3)
b. Distribution not uniform
c. Concentrated between 10 to
50 kilometers above the surface
d.
Absorbs harmful UV radiation
e. Human activity is depleting
ozone by adding chlorofluorocarbons (CFCs)
III. Structure of the atmosphere
A. Pressure changes
1. Pressure is the weight of the
air above
2. Average sea level pressure
a. Slightly more than 1000 millibars
b. About 14.7 pounds per
square inch
3. Pressure decreases with altitude
a. One-half of the atmosphere is below 3.5 miles (5.6 km)
b. Ninety
percent of the atmosphere is below 10 miles (16 km)
B. Atmospheric layers based on
temperature
1. Troposphere
a. Bottom layer
b. Temperature decreases with
altitude – called the environmental lapse rate
1. 6.5 C per kilometer
(average)
2. 3.5 F per 1000 feet
(average)
c. Thickness varies – average
height is about 12 km
d. Outer boundary is named the
tropopause
2. Stratosphere
a. About 12 km to 50 km
b. Temperature increases at
top
c. Outer boundary is named the
stratopause
3. Mesosphere
a. About 50 km to 80 km
b. Temperature decreases
c. Outer boundary is named the
mesopause
4. Thermosphere
a. No well-defined upper limit
b. Fraction of atmosphere's
mass
c. Gases moving at high speeds
IV. Earth-Sun relations
A. Earth motions
1. Rotates on its axis
2. Revolves around the Sun
B. Seasons
1. Result of
a. Changing Sun angle
b. Changing length of daylight
2. Caused by Earth's changing
orientation to the Sun
a. Axis is inclined 23½°
b. Axis is always pointed in
the same direction
3. Special days (Northern
Hemisphere)
a. Summer solstice
1. June 21-22
2. Sun's vertical rays are
located at the Tropic of Cancer (23½°N latitude)
b. Winter solstice
1. December 21-22
2. Sun's vertical rays are
located at the Tropic of Capricorn (23½°S
latitude)
c. Autumnal equinox
1. September 22-23
2. Sun's vertical rays are
located at the Equator (0° latitude)
d. Spring equinox
1. March 21-22
2. Sun's vertical rays are
located at the Equator (0° latitude)
V. Atmospheric heating
A. Heat is always transferred from warmer
to cooler objects
B. Mechanisms of heat transfer
1. Conduction through molecular
activity
2. Convection
a. Mass movement within a
substance
b. Usually vertical motions
3. Radiation (electromagnetic
radiation)
a. Velocity: 300,000
kilometers (186,000 miles) per second in a vacuum
b. Consists of different
wavelengths
1. Gamma (very short
waves)
2. X-rays
3. Ultraviolet (UV)
4. Visible
5. Infrared
6. Microwaves
7. Radio (longest waves)
c. Governed by basic laws
1. All objects, at
whatever temperature, emit radiation
2. Hotter objects radiate
more total energy per unit area than do cooler objects
3. The hotter the
radiating body, the shorter the wavelength of maximum radiation
4. Objects that are good
absorbers of radiation are good emitters as well
C. Incoming solar radiation
1. Atmosphere is largely
transparent to incoming solar radiation
2. Atmospheric effects
b. Reflection – albedo (percent reflected)
a. Scattering
c. Absorption
3. Most visible radiation reaches
the surface
4. About 50% absorbed at Earth's
surface
D. Radiation from Earth's surface
1. Earth re-radiates radiation
(terrestrial radiation) at the longer wavelengths
2. Longer wavelength terrestrial
radiation is absorbed by
a. Carbon dioxide and
b. Water vapor in the
atmosphere
3. Lower atmosphere is heated from
Earth's surface
E. Heating of the atmosphere is termed
the greenhouse effect
VI. Temperature measurement
A. Daily maximum and minimum
B. Other measurements
1. Daily mean temperature
2. Daily range
3. Monthly mean
4. Annual mean
5. Annual temperature range
C. Human perception of temperature
1.Anything that influences the rate of heat loss from the
body also influences the
sensation of
temperature
2. Important factors are
a. Air temperature
b. Relative humidity
c. Wind speed
d. Sunshine
VII. Controls of temperature
A. Cause temperature to vary
B. Receipt of solar radiation is the most
important control
C. Other important controls
1. Differential heating of land and
water
a. Land heats more rapidly
than water
b. Land gets hotter than water
c. Land cools faster than
water
d. Land gets cooler than water
2. Altitude
3. Geographic position
4. Cloud cover
5. Albedo
VIII. World distribution of temperature
A. Temperature maps
1. Isotherm – a line connecting
places of equal temperature
2. Temperatures are adjusted to sea
level
3. January and July are used for
analysis because they represent the temperature extremes
B. Global temperature patterns
1. Temperature decreases poleward from the tropics
2. Isotherms exhibit a latitudinal
shift with the seasons
3. Warmest and coldest temperatures
occur over land
4. In the
Southern Hemisphere
a. Isotherms are straighter
b. Isotherms are more stable
5. Isotherms show ocean currents
6. Annual temperature range
a. Small near equator
b. Increases with an increase
in latitude
c.
Greatest over continental locations