1. Characteristics of the Atmosphere
Chapter 22.1
Characteristics of the Atmosphere

2. Atmosphere – the layer of gases that surrounds the Earth.
What is the Atmosphere?
Atmosphere – the layer of gases that surrounds the Earth.
The Two Functions of Our Atmosphere:
To protect the Earth’s surface from the Sun’s radiation.
To regulate the temperature of the Earth’s surface.

3. Chemical Composition of the Atmosphere
Abundant Elements
Nitrogen (78%)
Oxygen (21%)
Argon (0.9%)
Abundant Compounds
Carbon dioxide (CO2)
Water Vapor (H2O)

4. Water Vapor in the Atmosphere
The Two Process That Put Water Vapor Into Air Are:
Evaporation
Transpiration (from plants)
The Two Process That Take Water Vapor Out of Air Are:
Condensation
Precipitation
Based on the time of day, location, and season, water vapor in the atmosphere can vary from as low as 1% to as much as 4%.

5. Ground level ozone causes SERIOUS lung irritation!!!
Ozone (O3) is a form of oxygen found in the stratosphere (The stratosphere is the layer ABOVE the layer we live in which is called the troposhere.).
Ozone is created when ultraviolet radiation (UV rays) from the Sun strikes and splits oxygen molecules (O2) to atomic oxygen (O).
The atomic oxygen (O) quickly combines with further oxygen molecules to form ozone (O3):
It should be noted that ground level (troposphere) ozone, which is produced by hydrocarbons that react with sunlight, is a pollutant itself!!!
Ground level ozone causes SERIOUS lung irritation!!!

6. Ozone
Before Earth had an ozone layer, all life lived under the oceans … NONE could live above them!
Ozone absorbs harmful ultraviolet radiation (UV rays) coming from the sun.
Ultraviolet radiation can cause severe burns, cancers, mutations, and even death!).
Ozone can be destroyed by: CFC propellants in old aerosol spray cans, Freon coolant from refrigerants in old refrigerators and air conditioners, and nitrogen oxide exhaust gases from burning supersonic jet fuel.

7. Dust In The Wind… Particulates – tiny solid particles in the air.
Sources of Atmospheric Particulates:
Dust from volcanic eruptions
Ash from fires
Microscopic organisms
Minerals lifted from soil by winds
Pollen from plants
Particles from meteorite impacts
Salt from sea spray
The tinier the particle, the longer it can stay suspended in the air.

8. What is Atmospheric Pressure?
Atmospheric pressure – the force per unit area that is exerted on a surface by the weight of the atmosphere.
99% of the total mass of the atmosphere is located within 32 km (20 miles) of the Earth’s surface.
The general trend between atmospheric pressure and altitude is that, the higher up in the atmosphere one goes, the less atmospheric pressure there will be.
pressure
altitude
A you go up in the atmosphere, the air gets thinner and therefore there is less pressure. That is why ears pop when ascending and descending in an airplane!

9. Measuring Atmospheric Pressure
Barometer – a device used to measure atmospheric pressure.
There are two types of barometers:
Mercury Barometer – a barometer that works when air pushes down on a pan of mercury forcing the mercury to rise up a calibrated, inverted tube.
Aneroid Barometer – a barometer that works when air pressure squeezes on the sides of a can moving an attached pointer.
Three values for Standard Pressure (at sea level):
1 atmosphere
760 mm Hg
1000 mb.

10. Layers of the Atmosphere 1
Did you know…
Mount Everest,
the highest elevation above sea level, is only about 8.8 km high, keeping it in the bottom layer of the atmosphere.
The Earth's atmosphere is composed of several layers:
We live in the Troposphere where almost all weather occurs
(ex. wind, clouds, fog, rain, hail, sleet, snow and storms).
Above the Troposphere is the Stratosphere, which contains the Ozone Layer, which blocks out harmful UV rays.
Commercial airliners (ex. a 747) usually fly in the troposphere, whereas supersonic jet airliners (ex. the Concorde) fly in the lower stratosphere.

11. Layers of the Atmosphere 2
Thermosphere
Lower region called ionosphere.
Upper region called exosphere.
Nitrogen and oxygen atoms absorb deadly gamma and X rays here, explaining the unexpected increase in temperature.
Mesosphere
Coldest layer of the atmosphere.
Temperature within this layer decreases as altitude increases.
Stratosphere
The Ozone Layer absorbs harmful UV Rays here, explaining the unexpected increase in temperature.
Troposphere
All weather change occurs here.
Temperature within this layer decreases as altitude increases because there is an increase in distance from the warming effect of sunlight absorbed by the Earth’s surface.

12. Air Pollution
The greatest source of air pollution today is from the burning of fossil fuels which releases pollutants such as sulfur dioxide gas (SO2), hydrocarbons, nitrogen oxides (NO), carbon monoxide (CO), and lead (Pb) into the air.
These pollutants can cause irritating smog which can make breathing difficult, especially for people with asthma, allergies, and lung disease … OR cause …

13. All rain is somewhat naturally acidic!!
Acid Rain!!!
All rain is somewhat naturally acidic!!
But when chemicals from car and factory exhaust (CO, CO2, NO, NO2, SO, SO2) combine with rainwater, they can produce HIGHLY acidic rains that damage buildings and monuments and kill plants and fish.

14. The End!... Up Next … Light and the Electromagnetic Spectrum …