Transcript Atmosphere Characteristics

Atmosphere Characteristics
Chapter 17, Section 1
Weather
• No other planet in our solar system has an atmosphere
with the exact mixture of gases or the moisture conditions
and heat needed to sustain life as we know it
• Weather is constantly changing, and it refers to the state of
the atmosphere at any given time and place
• Climate is based on observations of weather that have
been collected over many years
• Climate helps describe a place or region
• The most important measurable properties of weather and
climate are air temperature, humidity, type and amount of
precipitation, air pressure, and the speed and direction of
wind
Weather
Concept Check
• How does weather differ from climate?
• Weather changes constantly, but climate is
based on patterns of weather that have been
observed over years. Climate helps describe a
place or region.
Composition of the Atmosphere – Major
Components
• The composition of the atmosphere has
changed dramatically over Earth’s nearly 4.6
billion year history
• The atmosphere is thought to have started from
gases that were emitted during volcanic
eruptions
• Air is a mixture of different gases and particles,
each with its own physical properties
• Two gases—nitrogen and oxygen—make up 99%
of the volume of clean, dry air
Gases Composing Clean, Dry Air
Composition of the Atmosphere – Variable
Components
• Important materials that vary in the air from time to time
and place to place include water vapor, dust particles, and
ozone
• Water vapor is the source of all clouds and precipitation.
• Movements of the atmosphere allow a large quantity of
solid and liquid particles to be suspended within it
• Ozone – a form of oxygen which combines three oxygen
atoms into each molecule (O3)
• We breath oxygen which has two atoms per molecule (O2)
• Ozone is concentrated 10 to 50 kilometers above 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
Composition of the Atmosphere – Human
Influence
• Air pollutants are airborne particles and gases that
occur in concentrations large enough to endanger the
health of organisms
• Primary pollutants, are emitted from identifiable
sources
• Secondary pollutants are not emitted directly into the
air, they form in the air when reactions take place
among primary pollutants and other substances
• Reactions triggered by strong sunlight are called
photochemical reactions
Primary Pollutants
What They Are
Sulfur
Oxides
16%
Particulates
Volatile
Organics
14%Nitrogen
Oxides
15%
6%
Carbon
Monoxide
49%
Where They Come From
Solid
Industrial Waste
Processes Disposal
3%
15%
Stationary
Source
Fuel
Combusti
on
27%
Misc.
9%
Transporta
tion
46%
Concept Check
• What are secondary pollutants?
• Secondary pollutants are pollutants that form
when reactions take place among primary
pollutants and other substances.
Height and Structure of the Atmosphere
• The atmosphere thins as you travel away from
Earth until there are too few gas molecules to
detect
• Atmospheric Pressure – weight of the air
above (~1000 millibars at sea level)
• The higher you go in the atmosphere, the less
air pressure there will be
• The atmosphere can be divided vertically into
four layers based on temperature
(troposphere, stratosphere, mesosphere, and
thermosphere)
Atmospheric
Pressure
Variation with
Altitude
Layers of the Atmosphere
• Troposphere – bottom layer of atmosphere,
temperature decreases with an increase in altitude
(~0-12 kilometers)
• This layer essentially has all the weather
phenomenon
• Stratosphere – temperatures gradually increase due
to concentration of ozone (~12-50 km)
• Mesosphere – temperatures again decrease with
altitude, going as low as -90ºC (~50-80 km)
• Thermosphere – no well defined boundary,
temperatures increase, due to short-wave solar
radiation being absorbed
Thermal Structure of the Atmosphere
Earth-Sun Relationships
• Solar energy is not evenly distributed over
Earth’s surface, but varies with latitude, time of
day, and season of the year
• It is this unequal distribution of heat which
creates winds and drives the ocean’s currents
• Seasonal changes occur because Earth’s axial
position relative to the sun continually changes
as it travels along its orbit
• If the axis were not tilted, we would not have
seasonal changes
Sun Rays Striking Earth
Earth-Sun Relationships
Solstices and Equinoxes
Concept Check
• In which direction does Earth’s axis point?
• Earth’s axis points toward the North Star.
Assignment
• Read Chapter 17, Section 1 (pg. 476-482)
• Do Chapter 17 Assessment #1-30 (pg. 499500)
• For Section 1: #’s 1-4, 8-10, 12, 15, 18, 19, 23,
24, 29
• For the Multiple Choice (#1-10) make sure to
write the question and answer
• For the rest…Complete Sentences!