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DESCRIPTION OF THE
ATMOSPHERE
Page 3-2 through 3-3
Composition: The atmosphere
is composed of 78% nitrogen and
21% oxygen. The rest of the gases make up 1%.
Regions: The atmosphere is
divided into regions according to composition or
temperature.
- The atmosphere's composition
consists of two main regions: homosphere
and heterosphere. The
homosphere extends from the Earth’s surface up to an altitude of 60 miles.
The heterosphere starts at 60 miles.
- The more common atmospheric classification is made according to temperature.
The lowest layer of this thermal structure is the troposphere.
- The temperature within the troposphere decreases at a fairly
constant rate as altitude increases. This decrease in temperature
is called the temperature lapse rate. Most
of our weather occurs within the troposphere.
(See illustration on page 3-2)
THE ELEMENTS OF THE
WEATHER
Page 3-3
Weather is the condition of the atmosphere at a given time
and place. It is a combination of temperature, winds, moisture and
pressure. These are called the elements of weather because they are the factors
that form weather.
Heat and temperature affect weather.
The temperature of the air is important because the heat energy within the
atmosphere generates all the Earth’s weather processes.
The molecules in a substance are constantly in motion. This means that molecules
possess energy.
Heat is the total energy
of motion of all the molecules
in a substance.
Temperature is the measure
of that
molecular motion on a scale devised by scientists. The
scale is commonly called a thermometer.
HEAT AND TEMPERATURE
Page 3-4
The four principal ways heat is
transferred from one place to another are conduction,
convection, advection and radiation.
- Conduction
is the
transfer of heat between objects whose surfaces are in
contact with each other.
- Convection
is the
transfer of heat in liquids or gases by currents
within the liquids or gases.
- Advection
is the process
of lateral heat transfer.
- Radiation
is the transfer
of heat by radiant waves.
- The rate at which the Earth's surface is heated by solar radiation is
called Insolation.
- Radiation
transfers heat
energy without changing the temperature of anything between the source of
energy and the object heated.
WIND
Pages 3-5 through 3-9
- When heated air rises and cooler air flows in to fill the lower
pressure area created by the rising air, this flow is called wind.
Coriolis effect:
- The most significant influence on the creation and flow of wind is
the spinning planet. The rotation of the Earth influences any object moving
over its surface.
- In the example above you will notice the earth's
counterclockwise rotation (E) viewed from the North Pole
(NP) causes polar air moving south
to be deflected to the right--toward the west. (Air
moving north from the Equator will also be deflected to the right--toward
the east.) This phenomena is called the
Coriolis effect.
Pressure Gradient is
the difference in pressure between neighboring areas of high pressure and low
pressure. Air flows from the high pressure areas into the low pressure areas
producing wind. The greater the pressure gradient, the stronger
the wind will be.
Gravity: tends pulls the air downward
producing the greatest air density near the Earth’s surface.
Local and Surface Air Movements:
Convection currents are formed along shorelines by the differing
temperatures of the land and the water. During the day, these currents cause the
wind to flow from the cooler water toward the warmer land. During the
night, they cause the wind to blow from the cooler land towards the warmer
water. This phenomena is known as the land-sea breeze.
| The Jet
Stream |
 
Jet stream chart on left courtesy of the Weather Channel |
- The jet stream is a narrow current of
air that moves around the Northern and Southern Hemisphere of the Earth in
wavelike patterns.
- It generally flows west to east.
- It migrates with the seasons.
- The strongest winds are
usually encountered above 30,000 feet.
MOISTURE
Page 3-9 through 3-10
- Water can be found in the atmosphere as a solid, liquid or a gas.
is
the ratio of the existing water vapor in the air to its possible
saturation point. Dew point
is the temperature at which the water vapor in the air condenses and becomes
liquid.
CLOUDS
Pages 3-10 and 3-11
- Fog is a cloud because it develops within the
atmosphere. However, fog is classified differently because it usually
forms under different conditions than a cloud.
- There are two general categories under which clouds can be
classified. They are cumulus and stratus.
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Cumulus clouds
are dome shaped. |
Stratus clouds
spread out in
layers. |
Cirrus clouds
high wispy clouds
composed of ice crystals. |
AIR MASSES AND FRONTS
Pages 3-12 through 3-14
- The boundaries between air masses
of different characteristics are called frontal zones or fronts.
- When a cold air mass replaces
a warmer air mass, the leading
edge of this cold air mass is called a cold front.
- A warm air mass generally contains more moisture than a cold air mass
because it is less dense and can hold more moisture.
- An occluded front is formed when
a warm air mass is "sandwiched" between two cold air masses.
(See illustrations page 3-13)
SEVERE WEATHER
Pages 3-15 through 3-19
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- Thunderstorms are formed when warm, moist air is pushed
upward rapidly, accompanied by powerful downdrafts of cool air. The three
stages of thunderstorm
development are: building,
mature, and dissipating.
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- Tornadoes are spawned from thunderstorms. Some researchers
think that a tornado is the result of variation in electrical charge
within the cumulonimbus cloud. Others believe that the cause is the
reaction of cold and warm air currents within the cloud.
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- A hurricane is a low-pressure area which goes through a
period of building up force over equatorial ocean areas. Hurricanes
(called typhoons in the Pacific) can be from 50
to 900 miles in diameter, with winds
of 75 to 130 or more miles per hours
rotating around a calm center--the
eye.
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Aircraft Icing
- Carburetor Ice - Some piston-engine planes have
carburetors. The carburetor is where fuel is mixed with air, and it gets
very cold due to the evaporation of the fuel. On a humid day, the moisture
in the air can turn to ice as it passes through the carburetor if the engine
is run at low speed. Pilots who experience carburetor ice turn on carburetor
heat to melt the ice.
- Glaze and rime ice are names given to the ice that
forms on an airplane's windshield, its propeller and other aerodynamic
surfaces as an airplane flies through supercooled rain droplets.
- Frost is another ice factor that affects aircraft.
Frost can disturb the airflow enough to reduce the lift efficiency of
aerodynamic surfaces.
Ice buildup on wing leading edge
- Frost, glaze ice and rime-icing conditions pose the
greatest danger to flight
primarily because they change the shape of the
airfoil and decrease the airplane's lift factor.
FROM THE SUN TO THE EARTH
Pages 3-22 through 3-24 |
Scientists observe and collect physical facts about our solar system
from space vehicles that they launch send out to take samples and make on-site
observations.
- Interplanetary space is
measured from the center of the sun to the orbit of its outermost planet
Pluto.
Sun
The sun is a star that consists of:
- The Photosphere,
which is the portion of the sun that gives
light. Sunspots
are enormous areas where the photosphere is dark. Sunspots are
thought to result from magnetic activity
- The Chromosphere
(sphere of color), lies above the photosphere and extends to about 15,000
miles.
- Inside the Chromosphere are spicules.
These are small spike-like, short-lived
prominences.
- The Corona (crown) is
an enormous area of faint white light that visibly extends outward from the
sun's surface.
MERCURY
Page 3-25
Mercury is a small planet and looks a lot like the Earth's moon. It has
been highly cratered by impacts from meteoroids and is completely covered by
loosely grained porous soil. It is exceptionally hot on its surface.
The Mariner spacecraft took some 5,000 photographs of Mercury's surface.
The photos lead to the discovery of a huge basin about 800 miles in diameter.
This is called the Caloris Basin.
It rotates very slowly about its axis and takes 59 Earth days to make
one revolution.
VENUS
Pages 3-23 through 3-26
Venus is the second planet outward from the Sun. It is nearest to Earth
in both distance and size. Venus, like all other planets, rotates about an axis,
but it rotates in a clockwise direction (east to west). It rotates very slowly
about its axis, making one revolution every 240 Earth days. It was thought that
Venus was a twin planet of Earth, but numerous spacecraft have studied Venus and
their findings show 900-degree Fahrenheit temperatures and surface pressure 90
times greater than Earth's. Our most recent spacecraft, the Magellan, will
continue to orbit Venus and probe its clouds to answer numerous questions that
scientists still have about Venus.
EARTH
Pages 3-26 through 3-27
The Ionosphere
is a zone of electrically conductive
layers in the upper atmosphere.
There are four separate reflecting layers in the upper atmosphere. The lowest of
these reflects long-wave radio transmissions. The higher layers reflect
short-wave transmissions.
The higher the reflecting layer, the farther a signal that
reflect off of higher layers can travel farther because they bypasses more of
the Earth's curvature.
- An ion is an atom
that carries a positive or negative electrical
charge as a result of losing or gaining one or more electrons.
THE MAGNETOSPHERE AND
SOLAR WIND
Pages 3-27 through 3-29
The magnetoshpere is the
region of the Earth's atmosphere influenced by the geomagnetic field. The solar
wind is a continuous stream of
charged particles flowing outwards from the sun. It strikes the
Earth's magnetosphere with considerable enough force to distort the
magnetosphere.
- The extent of the solar wind's effect on the magnetosphere is not
known precisely, but it is known that it sweeps the magnetosphere
beyond the orbit of the moon.
- Information about the total magnetosphere and the solar wind is currently
being studied via satellites.
VAN ALLEN RADIATION
BELTS
Pages 3-29 through 3-30
The Van Allen radiation belts are filled with charged particles.
They are produced by interaction between the Sun and the Earth.
Concentrations of radiation within the Van Allen belts pose a
hazard to astronauts.
EFFECTS OF SOLAR
DISTURBANCES
Page 3-30
The impact of solar magnetic storms
on the Earth is especially apparent in radio
transmission interference. These magnetic storms interfere with the
reflectivity of the ionosphere and cause it to actually absorb radio
transmissions rather than reflect them.
METEOROIDS
- A meteoroid becomes a meteor
(shooting star) when it enters the Earth's outer atmosphere.
- If the meteor gets through the atmosphere and lands on Earth, it is
called a meteorite.
SPACE BEYOND EARTH'S
ORBIT
Pages 3-32 through 3-33
- Cislunar space is the
space between the
Earth and the Moon.
- Cislunar space consists of meteoroids, the magnetosphere
and cosmic rays.
The Earth’s Moon
The moon has no atmosphere to
protect it; therefore, its surface is bombarded by solar
radiation, cosmic rays and interplanetary dust. The surface
temperature varies widely from -250 degrees Fahrenheit to +270 degrees
Fahrenheit . Also, meteoroids impact its lunar surface without
ever going through the meteor and meteorite stages as with Earth.
Moon Dust
- Meteoroids strike the surface of the moon with such force that it
pulverizes lunar matter into dust.
- Other dust, cosmic dust, is picked up from space by the moon's
gravitational pull.
Moon Rocks
The Apollo lunar landings discovered that there are many different kinds
of rocks on the moon. The two basic kinds of rocks – basalt
(lowland material) and anorthosite
(highland material) are the most
common.
MARS
Pages 3-35 through 3-37
Mars is called the Red
Planet because it appears as a small reddish light when viewed
with the naked eye. Mars was photographed and studied by the Mariner
and Viking probes.
Between Mars and Jupiter are millions of pieces of
rock. They form a belt called the Asteroid Belt.
Asteroid means "similar to a star" or starlike. These starlike
pieces of rock may be the remains of a planet that once orbited between Mars and
Jupiter.
THE OUTER PLANETS
Pages 3-38 through 3-42
Jupiter
Jupiter is the largest planet
and makes up about 70 percent of the mass of all the planets.
Jupiter rotates very rapidly. It is flattened at the poles and bulges at
the equator.
Pioneer 10 and 11
spacecraft made very significant contributions to our knowledge of the Jovian
(Jupiter) atmosphere, magnetism and radiation and satellites of the giant
planet.
NASA's Galileo project was
launched October 18, 1989. It orbited and probed Jupiter in the mid-1990s.
Saturn
Saturn was probed by the Pioneer
spacecraft. It returned a variety of findings about Saturn’s rings,
17 moons, magnetic field,
radiation belts and the planet itself which is composed mainly of hydrogen
gas. Voyager 1 has
also visited Saturn.
Uranus
Uranus is the oddball of the solar system
because it lies on its side with its poles alternately facing the sun. Uranus'
magnetic field does not have the usual north-south axis. It is tilted 60
degrees and offset from the center of the planet.
Uranus' rings are made of boulder-size chunks. This is quite a
contrast to Saturn's 1,000 or so rings that are composed of bright, grain-size
particles.
Neptune
In August 1989, Voyager 2
reached the frigid planet of Neptune and the overall results were spectacular.
It is smaller and colder than Uranus and, like Jupiter, is disturbed by
great storms. Neptune has eight moons;
the largest is called Triton. Like Uranus, Neptune has a greater density than
Jupiter and Saturn.
Pluto
No space probe has ever been to the planet Pluto. Therefore, we
know very little about this particular planet.
We do know that it is yellowish in color, is about the size of Mars,
rotates on its axis in about 6.5 Earth days and has one known satellite. Pluto
appears to be a snowball of methane and water mixed with rock.
COMETS
Pages 3-42 through 3-44
- Comets are erratically
orbiting bodies of dust and ice.
When a comet comes near the sun, the heat and solar wind melt part of its
ice content and blow it in the direction of the solar wind. Thus, the
typical comet's tail points away from the sun
as the body swings around the sun.
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Comet Halley
The Comet Halley was studied by two Vega probes
launched by the Soviets; the European spacecraft Giotto; and two
spacecraft launched by the Japanese.
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THE MILKY WAY AND
BEYOND
Pages 3-45 through 3-47
- The distances between one solar system
and the beginning of another solar system is called interstellar
space.
- Astar's color indicates it temperature. The Sun
is a average yellow star. The hottest
stars are blue. White stars are
less hot than blue stars, but hotter than yellow stars. Orange
and red stars are colder than
the sun.
- Two existing stars which orbit a common center of gravity are called binary
stars.
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Nova are stars which are not stable;
they flare, subside, and flare again. A supernova
occurs when an explosion
on a star increases its brilliance to many
thousands of times brighter than a nova.
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A Pulsar
formed from the remains of a supernova is a dense spinning
neutron star. One teaspoonful of a Pulsar would weigh a billion
tons on Earth. |
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Nebulae
are dark or bright clouds within our galaxy. The dark
Nebulae are vast clouds of matter which have not
as yet formed into stars. |
- Intragalactic space
is the space within the galaxies.
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