Chapter 15The AtmosphereEnvol. Sci. IIMr. 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 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 fluid

Convection 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