ATMOSPHERE
Composition of the Atmosphere
•The atmosphere is comprised of a variety of gases:
Major Constituents (99%):
Nitrogen (N): 78%
Oxygen (O2): 21%
Trace Constituents:
Argon (Ar), about 0.9%
Water vapor (H2O),
Carbon dioxide (CO2),
Ozone (O3), near zero at the surface
Methane (CH4),
and others…..
Recycling of
Atmospheric
Materials
Movement of Heat Energy
• Radiation: the transfer of energy through space in
the form of visible light, ultraviolet rays and other
types of electromagnetic waves.
• Convection: the transfer of heat energy in a liquid or
gas through the motion of the liquid or gas caused by
differences in density.
• Conduction: the transfer of heat energy through
collisions of the atoms
or molecules of a
substance.
Heat and Temperature
• Temperature: is a measure of the average
kinetic energy of atoms or molecules in the
substance.
• Heat: the total kinetic energy of all of the
particles of the substance.
Troposphere:
• 0 to 15 km altitude
• The lowest region of the atmosphere, where life & weather exist.
• It contains 99 percent of the water vapor and 75 percent of the
atmospheric gases
• Temperature decreases with
altitude.
• Long-wave radiation emitted from
Earth is absorbed by the
atmosphere, the atmosphere
becomes less dense with increasing
altitude, less air to absorb
• Top of the troposphere is known as
the tropopause
Stratosphere
• 15 to 50 km altitude
• Heating occurs because ozone (O3)
absorbs ultraviolet radiation
from the Sun.
• Temperature increases with
altitude due to ozone absorbing
ultraviolet radiation.
• Top of the stratosphere is known
as the stratopause
Mesosphere
• 50 to 90 km altitude
• Temperature decreases with altitude
• The lowest temperatures in the
entire atmosphere are found at
the mesopause during summer
at high latitudes, 130 K (-226°F)
can occur
• Top of the mesosphere is known
as the mesopause
Thermosphere
• 90 to 500 km altitude
• Temperature increases with altitude above 90 km, and is constant
above 200 km.
• This heating is due to absorption of
solar radiation.
• The highest temperatures in the
atmosphere can be found in the
thermosphere, can rise about
1000oC (2000 K)
• Separated into layers of different
gasses.
• Lowest layer Nitrogen
• Then Oxygen to 1000km
• Then Helium to 2400km
• Top layer is Hydrogen thinning
into space
Ionosphere:
• Occurs within the mesosphere and thermosphere
between 90 and 500 km.
• Layer of electrically charged
particles
• Effected by solar events
• Electrically charged particles
for solar events interact with
Earth’s magnetic field create
auroras (Northern and
Southern lights).
Exosphere:
• The exosphere is the outermost layer of the atmosphere.
• The temperature in the exosphere goes up with altitude.
• Satellites orbit earth in the exosphere
Insolation and the Atmosphere
• Insolation: incoming solar radiation.
– some solar radiation is absorbed by gasses in the
atmosphere
– some solar radiation reaches the Earth’s surface
– some solar radiation is scattered in the
atmosphere and is returned to space
Heat Budget of Earth and the
Atmosphere
• Small % of insolation is absorbed by the atmosphere.
• Energy transferred by radiation, conduction and
evaporation and substance condesation of water
• This energy transfer is the major cause of Earth’s weather
• 50% of solar radiation reaches the Earth’s surface
• Accumulation of carbon dioxide and water vapor absorbs
most of the infrared radiation preventing from radiating
directly back into space creating the Greenhouse effect.
• Without the green house effect, most of the heat energy
would be lost to outer space, which would cause Earth’s
average temperate to be about 33oC.
• The increased levels of carbon dioxide in the atmosphere
the Earth’s heat budget may be out of balance, thus the
warnings of Global Warming.
Temperature variations due to
Insolation
• The intensity of insolation varies with the time
of day, the latitude and the time of year.
• The characteristics of a material determines
how much insolation is absorbed and how the
absorbed energy affects the temperature.
Intensity of Insolation
• Intensity of insolation is depended on the angle at which the sun’s rays strike
Earth’s surface.
• When the sun is at 90o the Earth receives the maximum amount of energy.
• As the angle of insolation decreases the amount of energy decreases
because the energy of the rays are
spread over a larger area.
• The sun ray’s are closest to 90o at noon, the intensity of insolation is the
greatest, so Earth’s sufaces heats up more quickly
• However, the warmest temperatures of the day are usually a several hours
after noon, when the lower
atmosphere is receiving more
energy from the ground than
it loses.
• The coolest temperatures of
the day are right before dawn
when both the ground and the
atmosphere has lost most of
its heat.
Intensity of Insolation
• The intensity of insolation is affected by the latitude.
• The closer to the equator the sun’s rays are almost vertical, so
the hotter the climate.
• Moving either north or south of the equator the angle of
insolation increases so the
energy is spread out over a
larger area. Thus the
greater the latitude the
colder the climate.
Intensity of Insolation
• At mid-latitudes, the sun ray’s are nearly vertical in the summer so
summers are hot. During the winter the angle of insolation is
greater so the winters are cold.
• Like day’s maximum tempertures,the year’s highest temperatures
after the time of maximum insolation.
• In the Northern Hemisphere, the lowest angle of insolation occurs
around Jun 21, so July is the warmest month of the year. The
greatest angle of insolation occurs in around December 21, so
January is the coldest month.
• The Southern
Hemisphere is
the
reverse.
• The affect of the insolation on sea-level
temperatures in January and July.
• What changes do you notice?
Human Impact on the Atmosphere
Acid Rain
• Forms due to pollutants
such as sulfur dioxide
and nitrogen dioxide
react with water vapor.
• Acidity is measured by
pH. The lower the pH
the more acidic the rain.
Smog
• Temperature inversion: when the temperature
at the Earth’s surface is cooler than the air
above it, so convection does not occur
Ozone Depletion
• Hole in Ozone layer due to pollution of
chloroflurocarbons (CFCs).
• Has greatly be reduce due to the elimination of
CFCs.
• Thin Ozone/Hole forms
each spring over Antarctica.
• Thinning Ozone/hole allows
for exposure to ultraviolent
radiation which is
dangerous to living things.