Chapter 17 Atmosphere
Earth Science
17.1 Atmosphere Characteristics
Weather
Constantly changing and it refers to
the state of the atmosphere at any
given time and place.
Climate
Based on observations of weather
that have been collected over many
years
Helps describe a place or region
Measurable Properties of Weather/Climate
I.
Composition of the Atmosphere
a. Temperature
b. Humidity
c. Type
d. Amount of precipitation
Changes of 4.6 billion years
Major Components
Air
Mixture of different gases and
particles
a. Each with its own physical
properties
b. Varies from time to time
c. Place to place
Water Vapor / Dust / Variable Components
Atmosphere would be very Stable
Volume of Clean, Dry Air
99% Nitrogen / Oxygen
Don’t affect the weather much
Dry Air 1%
0.930% inert gas argon
0.039% carbon dioxide
0.031% number of other gases
Variable Components
Water Vapor
Varies from 0 – 4%
a. Source of all clouds and
precipitation
b. Absorbs heat given off by Earth
c. Absorbs some solar energy
Ozone
Form of oxygen that combines 3
oxygen atoms into each molecule
a. Very little ozone in the
atmosphere
b. Concentrated layer 10 – 50 km
above the Earth’s surface
***If ozone did not filter most UV
radiation and all of the sun’s UV rays
reached the surface of Earth, our
planet would be uninhabitable for
many living organisms.
Human Influence
Air Pollutants
Airborne particles and gases that
occur in concentrations large enough
to endanger the health of organisms.
Primary Pollutants
Emitted directly from identifiable
sources
Ex. Cars, trains, factories,
Secondary Pollutants
Not emitted directly into the air
a. Form in atmosphere – reactions
take place among primary
pollutants and other substances
II.
Height and Structure of the Atmosphere
**Atmosphere thins as you travel
away from Earth until there are too
few gas molecules to detect
Pressure Changes
The weight of the air above the Earth
a. Sea level – Average Pressure 1000
millibars
Temperature Changes
1. Troposphere
Atmosphere can be divided vertically
into four layers
Bottom layer decreases with an
increase in altitude
a. Thickness is not the same
everywhere
b. Temperature drops to the height
of 12 km
Tropopause
Outer boundary of troposphere
Height of 12 km
2. Stratosphere
Beyond tropopause
a. Temperature remains constant to
a height of 20 km
b. Gradual increase in temperature
until stratopause
c. Stratosphere is heated at this
height due to absorbtion of
ultraviolet radiation
Stratopause
3. Mesophere
Increase temperature up to 50 km
Temperatures decrease with height
until mesopause
Mesopause
4. Thermosphere
^ 80 km above the Earth /
temperatures reach -98* C
no well-defined upper limit
Temperatures increase because
oxygen / nitrogen absorb short-wave
high energy solar radiation
III.
Earth-Sun Relationships
Earth’s Motions
Rotation – Spinning of Earth about its
axis
a. Imaginary line through north
and south pole
b. Earth rotates 1 every 24 hrs
– cycle of daylight/darkness
Revolution – Movement of Earth in
its orbit around the sun
a. Travels 113,000 km per
hour in ellipitical orbit
Earth’s Orientation
Seasonal changes occur because
Earth’s position relative to the sun
continually changes as it travels along
its orbit.
Summer Soltice
June 21, 22 First official day of the
summer
Winter Soltice
December 21, 22 First day of winter
Autumnal Equinox
September 22, 23
Spring Equinox
March 22, 23
**All in the Northern Hemisphere