Chapter 15
The Atmosphere
Envol. Sci. II
Mr. Martino
Lesson 1 – The Atmosphere

Properties of the Atmosphere
◦ Atmosphere – thin layer of gases that
surround the Earth
◦ Composition of the Atmosphere
 Nitrogen – 78%; bacteria convert N2 or nitrogen
gas into a usable compounds called nitrates and
nitrites through a process called nitrogen fixation
 Oxygen – 21%; Oxygen gas built up over billions of
years due to tiny photosynthetic organisms
 Water Vapor – gaseous water found in the
atmosphere
◦ Relative Humidity – the ratio of water vapor
the air contains to the maximum amount it
could have at that temperature
 When humidity is high, sweat does not evaporate
from the surface of the skin, therefore, perspiring
does not cool us down
 Condensation – process where water vapor quickly cools
down on a surface that is colder than the air
 Dew – when the air temp is warmer than freezing
 Frost – when the air temp is below freezing
 Cloud Formation – condensation that occurs in the air on
tiny particles (particulates ) that are in the air such as salt
crystals, smoke, and dust
◦ Air Temperature
 Temperature varies on the Earth due to the
different angles in which the sun’s rays strike it
◦ Air Pressure – the force exerted by air on the
area below it
 Measuring air pressure – barometer
 Mercury barometer – air pressure pushes mercury up the
column in a tube, the greater the pressure, the higher the
mercury will rise in the tube; inches
 Aneroid barometer – metal chamber whose walls bend in
when air pressure is high and bulge out when air pressure is
low; the bending of the wall moves a dial; millibars
Barometers
◦ Barometric Pressure and Forecasting
 High Pressure – air pressure is pushing down on
the column of mercury making it rise, thus pushing
out the bad weather; nice day
 Low Pressure – air pressure is not pushing down
on the column of mercury making it fall, thus
allowing the bad weather in; not so nice day
 Altitude and Air Pressure
 The lower the altitude, the higher the air pressure
 The higher the altitude, the lower the pressure
 Stack of books example; book on the bottom have more
pressure exerted on them than books at the top
Layers of the Atmosphere

The Troposphere – the lowest layer of the
atmosphere directly above the ground
 Contains the oxygen we need
 Movement of air in the troposphere is largely
responsible for the weather
 11 km in height (7 miles) = thicker at equator
 As height increases, temperature decreases
 The top acts as a cap not allowing it to mix with
the layer above

The Stratosphere – the layer of the
atmosphere above the troposphere
 11-50 (km) above sea level (7-31 miles)
 The highest level of the stratosphere is warmer
than the lower levels.
 Ozone layer – gaseous oxygen found in the upper
layers
 Absorbs and scatters the UV rays in the stratosphere
 Occurs naturally in stratosphere
 Causes damage to lung tissue and impacts plant growth in
the troposphere

The Mesosphere and Thermosphere
◦ Mesosphere – extends 50-80 km (31-50
miles) above sea level
 Air pressure is very low
 Meteorites burn up entering the mesosphere
making fiery trails
◦ Thermosphere – begins about 80 km above
Earth
 Air is thin; temps. are very high
 Aurora borealis (northern lights)
The Troposphere and Weather
Weather – atmospheric conditions over
short time intervals
 Climate – pattern of atmospheric
conditions in large geographical regions
 Example – the climate in London is moist
and temperate, but the weather can be
hot and humid on a summer day

Heat Transfer in the Troposphere
 Energy from the sun heats the
atmosphere driving air movement
influencing temperature and climate.

◦ Heat always moves from warmer to colder
◦ Radiation – transfer of energy through space
 No direct contact with a heat source
 Dark objects absorb more heat, while light objects
reflect more heat
◦ Conduction – transfer of heat directly
between two objects that are in contact with
one another
 Occurs between the surface of the Earth and the
air directly above it
◦ Convection – transfer of heat by the
movement of currents within fluid

Convection Currents – sinking cool air
and rising warm air; causes winds
Air Masses


Air mass – temperature,
humidity, and pressure
are generally the same
Front – boundary
between air masses

Warm Front – boundary
where a mass for warm
air is pushing a mass of
cold air
◦ Warm moist air rises over
the cold dense air creating
light rain

Cold Front – boundary
where a mass of cold air
pushes against warm
moist air
◦ Cold air pushes the moist
air up causing it to
condense forming heavy
precipitation
Pollution of the Atmosphere

Sources of Air
Pollution
◦ Air pollution – release
of damaging materials
into the atmosphere
◦ Emissions – the
damaging substances
Air Pollution

Classes of Pollution
◦ Natural Processes –
wind kicking up dust,
volcanic eruptions, fires
◦ Human Sources –
combustion of fossil
fuels
◦ Primary Pollutant –
released directly into the
troposphere
◦ Secondary Pollutant –
products of reactions
between primary air
pollutants in the
troposphere
How Air Pollutants Affect You

Respiratory Problems
◦ Dust particles get
trapped in mucus
secretions and hair lining
of the respiratory tract
 Makes you cough
 Long term exposure leads
to asthma, bronchitis, and
emphysema

Carbon Monoxide
◦ Bonds to hemoglobin in
the blood, not allowing
oxygen to bond to
RBC’s
 Headaches, tiredness,
nausea
 Long term – heart disease
 Heart must work harder to
deliver the same amount of
oxygen to starved cells

Cancer
◦ Long term exposure can cause cells to mutate and
start to divide uncontrollably forming tumors
 Benign or malignant
15.3 Controlling Air Pollution

The Clean Air Act
◦ First passed in 1963
 Revisions in 1970 and
1990 set stricter air
quality standards
◦ Protects and improves
the quality of air in
order to safeguard
human health and the
environment

Provisions of the Act
◦ Limits emissions from
vehicles and industries
◦ Limits the conc. Of
specific air pollutants
and particulate matter
◦ Allows people to sue
industries for break
rules
◦ Sets aside research
funds for pollution
control

Reduction in Air
Pollutants
◦ Since its passing, the
worst air pollutants have
seen a decrease of 57%,
even though there are
more people


Motor vehicles –
catalytic converters in
gasoline cars reduce
air pollutant emissions
Cleaner Gasoline –
lead was a major
component of gasoline
prior to 1973, today,
only trace amounts
remain.

Ozone: A Success Story
◦ Ozone is a pollutant in smog in the
troposphere, but absorbs UV radiation in the
upper stratosphere.
 The Ozone Hole
 Area of lowered ozone concentration over Antarctica that
occurs every year from August until October.
 Choloroflourocarbons
 Chemicals that are produced by aerosol spray cans and
refrigerators; breaks down ozone by releasing Cl- into the
atmosphere
◦ Montreal Protocol
 Nations signed this in 1987
 Goal was to reduce the CFC production