Chapter 15 The Atmosphere

1. Chapter 15The Atmosphere Envol. Sci. II Mr. Martino

2. 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

4. 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

5. 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

6. Barometers

8. 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

9. 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

11. 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

12. 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)

14. 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

15. 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

16. 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

17. 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

20. Pollution of the Atmosphere • Sources 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

21. 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

22. Cancer • Long term exposure can cause cells to mutate and start to divide uncontrollably forming tumors • Benign or malignant

23. 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

24. 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.

25. 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

26. Montreal Protocol • Nations signed this in 1987 • Goal was to reduce the CFC production