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
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%
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 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
 Summer and Winter Solstice occur when Earth’s tilt is
pointed away from the sun
 The Autumnal and Spring Equinoxes occur when the sun’s
vertical rays strike the equator (Earth not tilted towards or
away from the sun)
 The length of daylight compared to darkness also is
determined by Earth’s position in orbit
Sun Rays Striking Earth
Earth-Sun Relationships
Solstices and Equinoxes
Assignment
 Read Chapter 17, Section 1 (pg. 476 – 482)
 Do Section 17.1 #1-6 (pg. 482)