Download Composition Of The Atmosphere

Chapter 1 Introduction To The Atmosphere
Objectives
• Identify some of the atmospheric hazards that exist.
• Describe how the atmosphere is a part of the Earth System.
• Describe the composition of the atmosphere.
• Explain why the depletion of the ozone is a problem.
• Identify the size of the atmosphere.
• Describe the structure of the atmosphere.
Weather & Climate
• Few other aspects of our physical environment affect our lives as much
as weather does.
• The combined effects of the Earth’s motions and energy from the Sun,
causes Earth’s atmosphere to respond in a variety of ways (called
weather) and over time these responses form a basic pattern (called
climate).
• It would be nice to be able to measure the positive effect weather has on
us, but usually we measure the effect weather has on us based on the
estimated cost in damage.
• A hurricane may cause several billion dollars worth of damage to a city
it strikes, or a drought may wipe out entire crops causing losses in
money that could have been brought in if crops didn’t fail.
• The words climate and weather not interchangeable.
• Climate: the sum of all statistical weather information that helps
describe a place or region.
• Weather: atmospheric
conditions at any given time or
place.
• In other words; weather is
moment to moment atmospheric
conditions, climate is the
conditions of a region or area
over a long period of time.
• Weather and climate are measured regularly with the same basic
properties and quantities called elements.
• The six major elements measured are: type & amount of precipitation,
type & amount of cloud cover, wind speed & direction, air pressure, air
temperature, and air humidity.
• Even though we will be studying these elements separately, they are
closely interrelated.
• A change in one causes a change in the others.
• Most people think their local meteorologist is who provides all of the
data used to prepare a weather forecast for their area; in fact it’s a vast
network of meteorologists sharing their data with everyone.
• The World Meteorological Organization (WMO) was started in 1950 by
the United Nations to help coordinate the effort by scientists to gather
weather and climate data from across the world.
• The World Meteorological Organization (WMO) has 185 participating
member-nations that provide up to the minute information gathered by
over 10,000 land
based stations,
7,000 ship based
stations, and 10
satellites.
The Earth’s
Four Spheres
• The Earth is
divided into four
major parts that
are all interconnected, called spheres.
• The four spheres are: the Lithosphere or Geosphere (solid Earth), the
Biosphere (all life on Earth), the Hydrosphere (water portion), and the
Atmosphere (gas envelope surrounding the Earth).
• The lithosphere or Geosphere refers to the rigid outer layer of the Earth
that includes the crust.
• The Biosphere refers to all life on Earth.
• The Hydrosphere refers to all the water on Earth in its various forms:
fresh water found in lakes, ponds, streams, clouds, ground water,
glaciers, etc; and salt water found in the seas and oceans around the
world (known as the global ocean).
• The Atmosphere refers to the small thin gas layer that surrounds Earth.
• From our view on the ground, it looks enormous.
• The truth is, compared to the radius of the lithosphere (at more than
4,000 miles), the atmosphere is quite small (99% of it is with 20 miles
of the surface).
Earth System Science
• As we study our planet, it soon becomes clear that all of the separate
aspects of Earth (referred to as spheres) work together seemlessly and
have a significant impact on each other.
• In fact, these different sphere are interconnected.
• The hydrologic (water) cycle is a perfect example.
• We refer to this and
other cycles, all
together, as a system.
• A system is any size
group of interacting
parts that forms a
complex whole.
• Most natural systems
are driven by sources of
energy that move matter
and/or energy from one
place to another.
• A closed system is self-contained, which means energy can move into
and out of a closed system, but matter is sealed up in the system.
• An open system is far more complex, because matter and energy are
able to freely enter or exit the system.
• Earth is considered to be an open system, because both matter and
energy are able to come to Earth.
• Energy in the form of the constant stream of sunlight, and matter from
the meteoroids hitting Earth.
• The addition of matter into the system results in constant change.
Composition Of The Atmosphere
• Our atmosphere is made up of a mixture of gases, each with its own
special traits.
• We often think of the oxygen that we breathe as being a major part of
Earth’s atmosphere, but it’s not.
• It’s made up of many different gases, with the main gas being nitrogen.
• It’s vital to life on Earth that the atmosphere is mostly nitrogen, because
it’s a more stable gas than oxygen.
• Oxygen is highly flammable, and nitrogen is not.
• If the atmosphere where mostly oxygen, the first spark would ignite the
whole atmosphere, and it would burn off in a matter of hours.
• Movement in the atmosphere is enough to keep a large amount of solid
and liquid particles suspended within it.
• Sometimes larger dust particle get kicked up in the atmosphere in the
form of dust storms, but they are to large to stay up for long.
• However, microscopic dust particles and water vapor can stay
suspended in the atmosphere for very long periods of time.
• They can come from fine soil, smoke & soot from fires, human
pollution, pollen from vegetation, ash & dust from volcanic eruption,
sea spray from breaking waves, all lifted into the atmosphere by surface
winds.
• These microscopic solid and liquid particles are together called
Aerosols.
Ozone Depletion
• Another important part of the atmosphere is Ozone (03); ozone is made
of three oxygen atoms joined together.
• Under normal conditions, there is very little ozone in the atmosphere (3
parts per 10 million), but it’s vital to life on Earth.
• Ozone filters out the sunlight’s harmful ultraviolet radiation, and
without it all life on Earth would die.
• In the last 60 years, air pollution in the form of chlorofluorocarbons
(CFCs) have been destroying ozone.
• CFCs are versatile chemical compounds that were stable and easy to
make, but when they were released into the atmosphere, they break
down into their base elements.
• Chlorine is one of CFC’s base elements, and it easily binds with ozone
molecules, separating the oxygen atoms from each other.
• Since the 1980s a hole in the ozone layer over Antarctica, has been
opening every August and closing every December allowing ultraviolet
radiation to reach the surface of the Earth.
• This may be the reason skin cancer has been steadily on the rise the last
30 years.
• Even though strong action has been taken to reduce CFC pollution in
the atmosphere, the ozone layer is slow to respond.
• If we continue to steadily cut back CFC pollution, the ozone layer may
be restored by the late 21st century.
• The Montreal Protocol is a treaty that more than 40 nations agreed to in
1987 that would sharply cut CFC production world-wide.
• If nothing had been done about CFCs back in the 1980s, then ozone
depletion in the Northern Hemisphere would have been at 50% and at
70% in the Southern Hemisphere.
Extent Of The Atmosphere
• So, how far does the
atmosphere extend above the
Earth’s surface?
• There’s no sharp boundary
indicating where the
atmosphere ends and space
begins, but there is a point
where the numbers of
atmospheric molecules begins
to decline rapidly.
• Looking at changes in
atmospheric pressure might
indicate how high up the
atmosphere goes.
• Sea level is generally considered the starting point of the atmosphere,
where there is about 1000 grams per square centimeter of atmosphere
pressing down on us.
• Half of the atmosphere lies below an altitude of 5.6 km (3.5 miles),
about 90% of the atmosphere is below 16 km (10 miles), and about
99.99997% of the atmosphere lies below 100km (62 miles).
Thermal Structure Of The Atmosphere
• Meteorologists have discovered that our atmosphere has four different
layers with different functions.
• The bottom layer that we live in is called the Troposphere, and it goes
from surface level to about 10 km up.
• The temperature gets colder, the higher up we go in this zone of the
atmosphere.
• The Troposphere gets most of the attention in meteorology, because this
is the layer in which weather occurs.
• The boundary between the Troposphere and the next layer up is called
the Tropopause.
• The Stratosphere is the next layer up, and this is the layer where ozone
is located.
• From the Stratosphere’s
lower boundary (10km) to
about 20 km up, the
temperature remains
constant.
• At about 20 km, the
temperature begins to
increase to a maximum of
just under 0oC.
• This is due to the amount
of ozone in this layer
absorbing ultraviolet
radiation.
• At about 50 km is the
Stratopause, which is the
boundary between the
Stratosphere and the
Mesosphere.
• In the Mesosphere, the air
really gets cold, with temperatures dropping from just under 0oC all the
way down to -90oC.
• The boundary between the Mesosphere and the Thermosphere is called
the Mesopause.
• The Mesopause is where we find the atmosphere’s coldest temperatures
(-90oC).
• Above the Mesopause is where we find the Thermosphere, which has
no as no defined upper limit.
• This graph to the left is a bit misleading; it infers that the temperature at
this level is extremely high, which is correct.
• In the Thermosphere temperatures get up to 1000oC, but these
temperatures are not comparable to surface temperatures on Earth.
• At this height, molecules are very hot because the gases are absorbing a
lot of energy.
• But because there are so few molecules, there is a very small amount of
heat.
• In the highest parts of the Thermosphere is an electrically charged layer
called the Ionosphere.
• This layer molecules of nitrogen and oxygen absorb high-energy short
wave radiation.
• When solar radiation bounces off of the Ionosphere and interacts with
nitrogen and oxygen, the resulting Northern & Southern Lights is
amazing.
• The northern lights are called the Aurora Borealis, and the southern
lights are called the Aurora Australis.