as the following table summarizes: Solar Radiation Atmosphere into Space into Space and Clouds Earth's Surface The albedo for the Earth is... When the Earth radiates away this energy in
Trang 1~_ _ _ _ _ _ _ _A CO M PRE H E NSIVE G UI D E TO WEATH E R P _ _ _ -~
2 It was named in 1908 by Teisserence de Bort and means the region where air turns over
THE
3 The troposphere is the layer of the atmosphere
A Gas Composition
I The atmosphere is composed mainly of a
gas known as Nitrogen, which is odorless
and colorless
2 Oxygen is the next most abundant element,
with other gasses represented only in trace
amounts
3 It is interesting to note that Helium, one of these
trace gasses, was discovered to exist in the sun
before it was discovered on Earth
a The distinctive colors that Helium emits were seen
in the light coming from the sun
b Scientists were able to determine what kind of ele
ment would emit such light
B Description of Composition
I There are several ways to describe the composi
tion of the atmosphere:
a By the weight of the constituents
b By their volume (below is a list of the principle
gasses in dry air, categorized by volume in the
atmosphere)
PRINCIPLE GASSES OF DRY AIR
C Possible Origination
I The Earth has what is known as a secondary
atmosphere, which was created after the forma
tion of the planet
2 The large gas planets, Jupiter, Saturn, Uranus
and Neptune, are entirely made of gas Jupiter
has a primary atmosphere, which is an atmos
phere that originated with the planet
3 There are thought to be two possible origina
tions of the Earth's atmosphere:
a The first hypothesized origination is by out
i When the Earth formed, it was a giant spinning ball
of molten lava
ii As it cooled, gasses trapped in the lava were
"belched" up by large volcanoes
iii The combination of these out-gassed vapors, and
the biological transformation of the chemistry of
the atmosphere by hundreds of millions of years of
plant growth, has, it is thought, given us our con
temporary atmosphere
b The second possible origination is by cometary
impact
i A comet is a giant iceberg of frozen water and
gasses
ii If a large comet struck the Earth several billion
years ago, it could have left a residue of water,
carbon dioxide, oxygen and other gasses
Note: The first hypothesis is now more widely
accepted
D Troposphere
1 The lowest level of the atmosphere is known as
the troposphere
nomena occur
4 The troposphere, in turn, has two layers The layer that touches the Earth is called the bound
ary layer and is about 5 to 10 miles high at the equator
5 The troposphere's upper limit is called the
tropopaus e and varies in height with both sea
son and location
a At the equator, the tropopause is usually about 12 miles high, and at the North Pole, about 5 miles high
b In the tropopause, the temperature of the air decreases steadily as altitude increases The rate is about -6,50 Celsius (11.7' Fahrenheit) for every kilometer (mile) you go up At the top of the tropopause, the tempera
ture is usually about -60" Celsius
E Stratosphere
I The stratosphere is the layer of atmosphere that exists between the heights of 10-35 miles
2 The temperature in the stratosphere increases with height because the ozone, which is only present in the stratosphere, absorbs ultraviolet radiation from the sun
F Mesosphere
1 The mesosphere is the atmosphere above the stratosphere
2 The temperature in the mesosphere begins to fall , often reaching the coldest of any part of the atmosphere This coldest region is about 50 miles up, and can be as cold as -100°C
G Thermosphere
1 The thermosphere is the fourth major layer of the atmosphere
2 It starts around 50-60 miles up
3 Temperatures that get warmer with height char
acterize the thermosphere
H Ionosphere
I The ionosphere is the layer within the thermos
phere or stratosphere in which there are enough ionized particles to effect the transmission of radio signals
2 Ionized particles are atoms or molecules that have more electrons than protons [negatively charged] or more protons than electrons [positively charged]
3 The ionosphere begins about 20-30 miles above the surface
4 It reflects longer-wavelength, lower-energy radio signals, like AM radio, back to Earth, but allows shorter-wavelength, higher-energy radio signals, like FM, to pass through into space
PERCENT OF SEA-LEVEL ATMOSPHERIC PRESSURE AT SELECTED ALTITUDES
A The Earth's Tilt and the Seasons
1 The Earth spins on its axis as it orbits around the Slm
2 The axis about which it spins is tilted with respect
to the plane about which it orbits the sun
a TIle top does not point directly up and down as it spins
b.lt is inclined, in our case, at 23° with respect to straight up and down
4 As it orbits the sun, in a near-circular path called an ellips e , it remains at the same angle and pointing in the same direction
a.This tilt means that during a certain time half of the year, the top part or the Earth is pointed towards the sun more than the lower pan
b During this period, the top part receives more sun light than the lower part, and therefore, becomes warmer This is summer in the upper part, the Northern Hemisphere, and winter in the lower part, the Southern Hemisphere
c When the Earth is on the exact opposite side of the sun, the Southern Hemisphere gets more sunlight,
and it is summer in the Southern Hemisphere and winter in the Northern Hemisphere
,
d Twice a year, the Northern and Southern Hemispheres get the same amount of sunlight
I These times are called the AlIllImllal and ~ernal
Equinox e s
ii When it is spring in the Northern Hemisphere it
is autumn in the Southern Hemisphere, and vice versa
B Eledromagnetlc Radiation
I Radiation is the only mechanism of heat trans fer that can transmit energy across empty space
2 The energy that powers our weather is rrom the sun Therefore, the energy that powers most, if not all, of our weather is radiative energy from the sun
a The visible part of the spectrum accounts for only
a small part of the radiation fi-om the sun
b The vast majority of the radiative energy is invisible light in the form of radio waves, microwave infrared waves, ultraviolet rays, x-rays, and gamma rays All of these forms of energy are the same as light, only different wavelengths
3 The radiation from the sun takes several differ ent paths after it encounters the Earth as the following table summarizes:
Solar Radiation
Atmosphere into Space into Space
and Clouds Earth's Surface
The albedo for the Earth is
Trang 2C Heat Transfer and the Greenhouse EHect
I About 50°1r, of the solar energy that strikes the
Earth is absorbed by the surface
2 The atmosphere is basically transparent to short
through the atmosphere and heats the Earth
a When the Earth radiates away this energy in the
form of long-wavelength infrared radiation, not all
of the energy escapes back into space
b Some of this low-energy, long-wavelength radia
tion is reflected back to Earth by carbon dioxide in
the atmosphere This is the greenhouse effect
3 Land heats up faster and to higher temperatures
than water It also cools down quicker and to
lower temperatures than water
a This leads to greater temperature variations for
cities away from water than for those on the coast
b The body of water nearby acts as a brake, keeping the
temperature from getting either too hot or too cold
D Heat versus Temperature
I There are important differences between heat
and temperature
a Heat is the microscopic vibration of the particles
that constitute an object
b Temperature is a way of comparing the average energy
of the particles in one ohject to the energy in another
2 Heat is energy Temperature is relative to some specif
ic point, such as the boiing point of water
E Wind-Chili Effed
I When air passes over water, it causes the water
to evaporate
a This water may be in the ocean, a lake, or on the
skin's surface
b When water evaporates, it absorbs energy
c Since air particles need more energy to move
around than water particles, water must absorb
energy in the form of heat when it evaporates
2 The more water that is evaporated, the cooler
the surface gets
a This is how sweating keeps the body cool in the
summertime
3 Wind-thill is created when cool air moves over a
surface and carries away some heat with it It sim
ply makes the air feel cooler than it actually is
F Cloud Formations
I Cirrus Clouds
a Cirrus clouds are the highest clouds in the
atmosphere
b.They usually exist at altitudes between 17,000 and
50,000 feet
c.Although they never actually produce rain, they
often precede low-pressure systems that form
many rain and snow clouds
2 Mid le (Alto) Clouds
a Mid-level clouds are called altocumulus and alto
st ratus clouds
b They exist at al titudes between about 6,000 and
17,000 feet
c Altocwnulus clouds are generally fluffY and white
They are very common on partly sunny days
d Altostratuss are grayish, uniform clo ds They
are never white They are characterized by the
st tified covering, which they give to the sky
3 Low Clouds
a The low clouds in the sky come in stra tus , nimbo
str atll s, stra to eumulus and cumu lus varieties
b Stratus clouds are low, gray clouds that cover the
sky uniformly
c Nimbostratus clouds are those stratus clouds that
produce rain
d Stratocumulus clouds are stratus clouds, which cover
the sky unifonn!y but do not produce rain Cumulus
clouds are low, fluffY clouds that do not produce rain
4 Cumulonimbus
a These are the clouds that produce lightning
stonns, hail, and tornadoes
b They are produced when unstable air (which is
hotter than its surroundings) is lifted into the
upper atmosphere by a cold front
c The warm air is cooled in the upper atmosphere,
thereby producing rain
d The top of the cloud may be hi gh enough to pene
trate into the jet stream, causing the characteris c
anvil-shaped top
5 Mammatus
a These are bulging, lumpy clouds sometimes seen
on the underbelly of a cumulonimbus cloud
b They are often associated with severe weather
6 Orographic Clouds
a This type of cloud is produced when warm air is lift
ed by mountains into the upper, cooler atmosphere
b The warm air is cooled and therefore, produces clouds and rain
G Mixed Skies
I In the region of a cumulonimbus cloud, many
FRONTS
A Fronts are the boundary between two air masses
1 Warm fronts have hig er temperatures and usu
ally more moisture than cold fronts
2 Stable air is that which is not greaty warmer
than its surroundings
B Warm Fronts
I Warm air is lighter than cold ai r
2 When a warm font is moving through an area, the warm air is higher than the cold air
3 Warm fronts usualJy move at about 25 km/hr (17 milhr)
4 A warm fro t with stable air tends to produce
light to moderate precipitation over an extended
period for a large area
5 The clouds often associated wiLl} these types of
fronts are cirrus, altostratus and nimbostratus
6 Warm fronts with u stable air tend to produce heavy precipitation and cumulonimbus clouds
C Cold Fronts
, I Cold air is heavier than warm air "'II!
2 When a cold front is passing through an area, the cold air is closer to the ground than the
warm air
a Cold fro ts move fater than warm fronts, about
35 km/hr (22 mi/hr)
b Cold fronts lift the warm air they are moving
into, thereby cooling the r mass, and causing AfI
clouds and rain
3 The rain caus d by cold fronts tends to b
more localized and more intens
D Stationary Fronts
I A stati onary front is a hot or cold front in which
the airflow is parallel to the surfa e posi on of the
front For instance, a front can be imagined to be
lke wal l
a A warm front moving away from you would be
slanted away from you and the air would be blow
ing in the direction it is moving
b A cold front moving away fom you would be
slanted towards you, and the air would be owing
in the direction it is moving
2 In a statio ary tront, the wind is blowing left or
right, not in the direction ofthc wall, hence the
tront has no motivation to move
E Occluded Fronts
I An occluded front is a situation in which a cold front overtakes a warm font
2 In this case, the cooler air of the cold front meets from behind the arm air being lifted by the cool air ahead of the warm front, and com
plex weather patterns often form
ATMOSPHERIC
EXPERIMENTS
W Balloons
A Weather BaUoons
I These are the most common types of atmos pheric probes
2 They often carry aloft lightweight scientific packages that measure such things as tempera ture, pressure, relative humidity, and altitude
those that have their position tracked by radar are called rawinsondes Satellite , airplanes and
B Ancient Atmosphere
I Scientists studying sedimentary rocks and ancient ice formations can explore the atmos phere of the past
2 Sedimentary rocks arc those in which sediment has accumulated over time and has been
mation about atmospheric precipitates and composition
3 Ancient ice formations may still have air bub bles trapped in them from many tens, hundreds
or thousands of years ago, and can, therefore
be useful tools in investigating the change in the
2
Trang 3called an anti-cyclone
fast
faster The effect is called conservation a/angular mom en t u m
/ and south, precipitating rain as it ascends
cell, and this particular cell is the equatorial
Hadley cell
b Thc winds in the Hadley cells just north and south
European explorers
Arctic and Antarctic circles
EQuat o• • •
Thermocline
B EI Nino
2 EI Nino is a major change in the surface tempera
nent, low-pressure system exists
the west, and warm water begins to accumulate off
of air behaves
is depleted of water
a Continental Polar
b Continental Arctic
II It also produces cold waves in winter
d Maritime Tropic
e Maritime Polar (Atlantic)
II In the winter, it brings fog and drizzle to the south
Plains and occasional droughts
in the air
anti-cyclonic flow The area of high pressure is
A Thunderstorm
rising though the atmosphere
Beaufort Name Miles
B Downbursts and Mlcrobursts
sure differences with in the cloud
and c n generate winds of 70+ mph
III Very small downbursts are called microbursts
of aircraft accidents
Trang 45 A large cumulonimbus cloud has a slow, diver
gent spin
a As the warm air rushes upward through the cloud,
it translates its slow rotation into the extremely
tornadoes:
I More tornadoes occur in tornado alley (Texas,
Missouri, Kansas, Oklahoma and Ohio) than
any place on Earth
2 They occur most frequently in May
3 The strongest wind in a tornado can be as high
as 300 mph
4 A to rn ado in Banglad e sh killed more than
1,000 people in 1989
5 The avera g e path len g th ofa tornado is about 5
miles long and 200 yards wide
6 The largest tornado outbreak on record
occurred on April 3 1974, when 148 tornadoes
struck j 3 states and killed 315 peopl e
7 A waterspout is a tornado over water
8 Most tornadoes spin counter-clockwise, the
same direction as hurricanes
FUJITA-PEARSON TORNADO SCALE
D Hurricanes
1 The initial step toward the formation of a hurri
storms called a tropical wave
when the thunderstorms organize themselves into
a single system
still more organized and has sustained winds 39
a Hurricanes have a characteristic spiral shape
which is a relatively calm region called the eye
counter-clockwise
typhoons
every year
storm surge
I The strong winds also whip the waves on top of the
tidal bulge up to heights of 25 feet above normal
E Lightning
parts of cumu
lonimbus clouds
air is swirling
very fast
electrons with
ounts of force,
and so, drops of
one another
cause
cloud becomes great enough, a spark jumps
across space, and lightning is produced
lightning bolt, which causes it to expand explosively
b Thu n e r is caused by the pressure wave of this
expanding, super-heated air
which is almost six times hotter than the sur
face of the sun
F Air Pollution
I Sources
a The major sources of air pollution are coal com
waste, and the combustion of oil
atmosphere is called pri ma ry pollution
c Pollutants that react chemically with other con
a Massive quantities of sulftlr dioxide and nitrogen
b Once there, they are transformed into weak nitric
and sulfuric acids by very complex processes
c The acidity of acid rain is about 4.5, midway between
concentrated sulfuric acid and distilled water
3 Impact on Humans
atmosphere
b Partic;tlat e s are tiny particles suspended in the air
c They contribute greatly to smog and other air
al centers
d Asthma and other lung di seases are exacerbated
e One estimate has it that air pollution alone con
G.Ozone
rays from the sun
2 Man-made chemicals called c hlorojlou roca r bons tend to both destroy the ozone layer and
altered the chemistry of the ozone formation
the Polar Regions
A.Auroras
I Auroras are glowing regions of the atmosphere caused by particles traveling along the Earth's
magnetic field
solar wind, travel along the magnetic field lines
cause it to glow
B Mirages
Rayleigh Scattering
AIR
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