Chapter 15The AtmosphereEnvol. Sci. IIMr. Martino
Lesson 1 – The AtmosphereProperties 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 AtmosphereThe 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 WeatherWeather – 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 TroposphereEnergy 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 fluidConvection Currents – sinking
cool air and rising warm air; causes winds
Air MassesAir 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 AtmosphereSources of Air
Pollution◦ Air pollution –
release of damaging materials into the atmosphere
◦ Emissions – the damaging substances
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
Air Pollution
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 l
eads 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 PollutionThe 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
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