Transcript Chapter 15

Chapter 15
The Atmosphere
I. Characteristics of the Atmosphere
A. The Composition
• Made up mostly of nitrogen gas
• Oxygen makes up about 20% of the
atmosphere
• Small particles, such as dust, volcanic ash,
sea salt, dirt, and smoke circulate the
atmosphere
• Water vapor is suspended and changes to
liquid rain and solid snow when
atmospheric conditions change
B. Atmospheric Pressure and Temperature
1. As Altitude Increases, Air Pressure Decreases
• Gravity pulls molecules in the atmosphere toward
the Earth’s surface
• Air pressure is the measure of the force of the
molecules pushing on a surface
• Air pressure decreases the further from sea level
you move because there are less molecules above
you
2. Atmospheric Composition Affects Air
Temperature
• Some parts of the atmosphere are warmer
because they contain a high percentage of
gases that absorb solar energy
C. Layers of the Atmosphere
• Based on temperature
changes
1. The Troposphere
• The layer in which we live
• Densest atmospheric layer,
containing almost 90% of
the atmosphere’s total
mass
• “tropo-” means “turning”
or “change”
• Temperatures very greatly
causing gases to mix
continuously
2. The Stratosphere
• Home of the ozone layer
• “Strato-” means “layer”
• Gases are layered and do not mix much
• Air is very thin and contains little moisture
• Lower part of stratosphere is -60°C and rises
as altitude increases due to the ozone
absorbing ultraviolet radiation from the sun
3. The Mesosphere
• “Meso-” means “middle”
• Coldest layer
• Temperature decreases as altitude decreases
• Top part of the mesosphere is -93°C
a. The Ionosphere
- Upper part of the mesosphere
- “iono-” means ions
- Heat increases in the layer above the mesosphere
causing gas particles to become electrically
charged
- These electrically charged ions radiate shimmering
lights called auroras
4. The Thermosphere
• The edge of the atmosphere
• “thermo-” means “heat”
• Temperature increases with altitude
• Nitrogen and oxygen absorb solar radiation
and release thermal energy causing
temperatures to exceed 1,000°C
• Particles are less dense than particles in the
troposphere so heat, or thermal energy, is
not transferred, so it does not feel hot
5. Exosphere
• Outermost layer
• “I Owe My Aunt Lucy Ten Outstanding
Strawberries. May I Taste ‘Em?
Inner Core, Outer Core, Mesosphere,
Asthenosphere, Lithosphere, Troposphere,
Ozone, Stratosphere, Mesosphere, Ionosphere,
Thermosphere, Exosphere
II. Atmospheric Heating
A. Energy in the Atmosphere
1. Radiation
• Energy transferred by electromagnetic
waves
• About 26% is scattered and reflected by
clouds and air
• About 19% is absorbed by ozone, clouds,
and atmospheric gases
• About 51% is absorbed by Earth’s surface
• About 4% is reflected by Earth’s surface
2. Conduction: Energy Transfer by Contact
• Transfer of thermal energy through a material
from warm to cold areas
• Air is heated near the Earth’s surface
3. Convection: Energy Transferred by Circulation
• Transfer of thermal energy by the circulation, or
movement, of a liquid or gas
• As air is heated, it becomes less dense and rises
• Cool, denser air sinks
• Cool air is heated by the Earth’s surface and
begins to rise again
• Movement creates convection currents
4. The Greenhouse Effect
• Energy that is absorbed by clouds and the
Earth’s surface is converted into thermal
energy that warms the planet
• Thermal energy is released into the
atmosphere but does not escape the outer
limits of the atmosphere
• The greenhouse effect is the process by
which gases in the atmosphere absorb
thermal energy radiated from Earth
- Allows solar energy to enter but prevents
thermal energy from escaping
5. Greenhouse Gases and Global Warming
• Greenhouse gases are gases that absorb
thermal energy in the atmosphere and
prevents the energy from escaping the
atmosphere
• An increase of greenhouse gases in the
atmosphere may be the cause of a warming
trend
III. Global Winds and Local Winds
A. Why Air Moves
• Wind is the movement of air caused by
differences in air pressure
• Differences in air pressure are generally
caused by unequal heating of the Earth
• The equator receives more direct solar energy
than other latitudes
- Air is warmer and less dense
- Warm air rises and creates low pressure areas
- Warm air flows toward the poles
• Air at the poles is cooler and more dense
- Cool air sinks and creates high pressure areas
- Cool air flows toward the equator
1. Pressure Belts
- Bands of high pressure and low pressure
found about every 30° of latitude
B. Global Winds
1. Polar Easterlies
• Formed as cold, sinking air moves from the
poles toward 60° north and south latitude
• Carry cold arctic air over the U.S., producing
snow and freezing weather
2. Westerlies
• Wind belts between 30° and 60° latitude
• Flow toward the poles from west to east
• Carry moist air over the U.S., producing rain
and snow
3. Trade Winds
• Blow from 30° latitude almost to the equator
4. The Doldrums
• “dull” or “sluggish” winds
• Little winds near the equator because the
warm, rising air creates an area of low
pressure
5. The Horse Latitudes
• Weak winds near 30° latitude because the
cool, sinking air creates an area of high
pressure
• Most of the world’s deserts are located at
these latitudes because the sinking air is very
dry
6. Jet Streams
• Narrow belts of high-speed winds that blow
in the upper troposphere and lower
stratosphere
• Do not follow regular paths around the Earth
• Affect the movement of storms
C. Local Winds
• Generally move short distances and can blow
from any direction
1. Sea and Land Breezes
- Air over land is warmer and rises
- Air over the ocean is cooler and flows to
land, producing a sea breeze
- A land breeze flows over the ocean at night
due to warm air over the ocean
2. Mountain and Valley Breezes
- Air above the mountain slopes is warm and
rises up the mountain, creating a valley
breeze throughout the day
- Air cools at nightfall and falls back down the
slopes, creating a mountain breeze
IV. Air Pollution
A. Primary Pollutants
• Put directly into the air by human or natural
activity
1. Human
- Carbon monoxide, CO
- Dust
- Smoke
- Vehicle exhaust
2. Natural
- Sea salt
- Volcanic ash
- Smoke from forest fires
- pollen
B. Secondary pollutants
• Form when two primary
pollutants react
• Ozone, O3, is an example
of a secondary pollutant
- Ozone in the
stratosphere absorbs
harmful radiation
- Ozone near the Earth’s
surface, is a dangerous
pollutant
C. Acid Precipitation
• Sulfur dioxide and nitrogen oxide are
produced when fossil fuels are burned
• Produce sulfuric acid and nitric acid when
mixed with water
1. Acid Precipitation and Plants
- Acid precipitation can cause the acidity of soil
to increase
- Nutrients become dissolved when soil acidity
increases and get washed away by rainwater
2. Acid Precipitation and Aquatic Ecosystems
- Aquatic organisms have adapted to live in
water with a particular range of acidity
- If acid precipitation increases the acidity of a
lake or stream, aquatic organisms may die
- Effects are worse in the spring when acidic
snow starts to melt
- Powdered lime, a base, is sprayed to
neutralize the acid in water
D. The Ozone Hole
• Chemicals called CFCs cause the ozone, O3, to
break down into oxygen, O2
• Oxygen, O2, does not block the sun’s UV rays
1. Cooperation to Reduce the Ozone Holes
- The use of CFCs have been banned and
alternatives have been developed
- CFC molecules can remain active in the
stratosphere for 60 to 120 years
- CFCs released 30 years ago are still
destroying ozone today
E. Cleaning Up Air Pollution
• Clean Air Act was passed by Congress in 1970
that gives the Environmental Protection
Agency (EPA) the authority to control the
amount of air pollutants that can be released
from any source