Download File - Earth Science

Composition of the Atmosphere
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The atmosphere
mostly consists of
nitrogen (78%),
oxygen (21%), and
argon.
99% composed of
Nitrogen and Oxygen
Remaining 1% made up of
small amounts of other gases
Structure of the Atmosphere
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Atmosphere composed of several layers
Structure of the Atmosphere
Troposphere
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Closest to Earth
Altitude 0-10 km
Contains most of the mass of
the atmosphere
Weather occurs here, pollution
collects
Upper limit called tropopause
Tropopause is where gradual
decrease in temperature stops
Stratosphere
-Above troposphere
-Altitude 10-50 km
-Contains mostly ozone
-Ozone absorbs more UV radiation, so this layer is heated
-Upper limit called stratopause
-Stratopause is where gradual increase in temperature stops
Mesosphere
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Above stratosphere
Altitude 50-80 km
No concentrated
ozone here, so
temperature drops
again
Upper limit called
mesopause
Mesopause is where
gradual decrease in
temperature stops
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Thermosphere
Above mesosphere
Altitude 80 km and above
until outermost boundary of
atmosphere
Contains a small part of the
atmosphere’s mass
Little air that is in this layer
increases in temperature
again to greater than 1000C
The Ionosphere
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The thermosphere can
be identified in two
parts- the ionosphere
and the exosphere.
Ionosphere: 80 km-640
(about 400 miles = 640
km).
It contains many ions
and free electrons
(plasma).
Auroras occur in the
ionosphere.
Exosphere
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Outermost layer of Earth’s
atmosphere
Light gases like helium and
hydrogen found here
Above exosphere is outer
space
No clear boundary between
atmosphere and space
Atmosphere Energy
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The Sun is the source for all energy in the
atmosphere.
Three ways the energy transfer occurs:
Radiation
 Conduction
 Convection
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Flash Animation
Radiation
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Radiation is the
transfer of energy
through space by
visible light, UV
radiation, and other
forms of
electromagnetic waves
Conduction
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Conduction is the
transfer of heat energy
that occurs when
particles collide
Through conduction,
Earth’s surface transfers
energy to nearby air
particles in troposphere.
Conduction only affects
small layer of
atmosphere.
Convection
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Convection is the transfer of
heat energy by the flow of a
heated substance
Pockets of air near Earth’s
surface are heated, become less
dense and rise
As warm air rises, it expands
and starts to cool. As it cools,
its density increases and the
cooler air sinks. As it sinks, it
warms again and process starts
over.
Temperature and Heat
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Temperature-measurement of energy of a
substance; interprets atmospheric processes.
Heat-transfer of energy from two objects of
different temperatures; fuels atmospheric
processes.
Pressure and Density
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Air pressure increases towards Earth’s surface
because of the greater mass of the atmosphere
above you.
Atmospheric pressure decreases with height
because there are fewer gas particles above you.
Density is proportional to amount of particles.
Wind
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Air moves in response to density imbalances
created by the unequal heating and cooling of
Earth’s surface.
These imbalances, in turn, create areas of high
and low pressure.
Wind can be thought of as air moving from an
area of high pressure to an area of low pressure.
Humidity
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Humidity-amount of water vapor in air.
Relative humidity-ratio of water that air contains
and the maximum amount of water the air could
contain.
Warm air is more capable of holding more
moisture that cold air.
Do we usually ever complain of humidity in
winter?
Clouds
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Dew point-temperature at which air must be
cooled to reach saturation.
Condensation-phase change from gas to liquid;
only occurs at saturation.
Lifted Condensation Level-LCL; point at which
condensation occurs.
Cloud Formation
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Air masses of different temperatures collide.
The less dense, warmer air mass rises over the
more dense, colder air mass.
As the warm air rises, it cools, and once it
reaches the LCL, water vapor will condense
around condensation nuclei to become a cloud,
if the density of condensation nuclei is great
enough.
Condensation nuclei-particles in the air around
which cloud droplets can form.
Precipitiation
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Coalescence-occurs when cloud droplets
collide and join together to form a larger
droplet.
When the droplet becomes too heavy to be held
aloft, gravity takes over and it falls to Earth
as precipitation.
Another Method of Cloud
Formation
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Orographic Lifting-air mass is forced to lift due
to topography, cooling down quickly in the
process, causing condensation and cloud
formation.
Meteorology
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Weather-current state of the atmosphere.
Climate- describes the average weather over a
long period of time
Air Masses
A large body of air with similar
-TEMPERATURE
- HUMIDITY
Temperature
• Warm
• Cold
Humidity
• Moist
• Dry
Air Masses’ Characteristics
Source Regions
Over land: drier.
Over water: more moist.
Types of Air Masses
DESCRIPTION
FORMED
1. Maritime: (m)
CONDITION
moist
LOCATION
(marina/water)
2. Continental:(c)
dry
(continents/land)
3. Tropical: (T)
warm
(tropics)
4. Polar: (P)
cold
(poles)
Types of Air Masses
Maritime Tropical
(mT)
Continental Tropical
(cT)
Maritime Polar
(mP)
Continental Polar
(cP)
Types of Air Masses
cP
Continental Polar
mP
Maritime Polar
Dry, cold air to central
and eastern US.
mP
Maritime Polar
Moist, cold air to east
areas of the Canada
Moist, cold air to west
coast of the US.
mT
Maritime Tropical
mT
Maritime Tropical
Moist, warm air to west
coast of the Mexico.
Dry, warm to Desert SW
Moist, warm air to south
Mr. Fetch’s Earth Science Classroom
east coast
of the US.
Air Mass Modification
mP
Maritime Polar
Moist, cold air to west
coast of the US.
Mr. Fetch’s Earth Science Classroom
Weather Systems
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Coriolis Effect-caused by Earth’s rotation;
causes moving objects to deflect right in N.
hemisphere, left in S. hemisphere.
This effect creates a global wind system that
transports air masses.
Three Types of Wind Systems
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Trade winds
Prevailing westerlies
Polar easterlies
Trade winds
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Move between equator
and 30° N and S latitude.
Air sinks, warms, and
returns to equator in
westerly direction.
Prevailing Westerlies
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Occurs between 30° and
60° latitude
Moves in opposite
direction of trade winds
Moves weather across
U.S.
Polar Easterlies
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Occur between 60° and
poles
Cold air
Fronts
A boundary between two air masses:
COLD FRONTS
WARM FRONTS
STATIONARY FRONTS
Occluded fronts
When air masses meet…
mP
Maritime Polar
Moist, cold air to west
coast of the US.
mT
Maritime Tropical
Moist, warm air to south
Mr. Fetch’s Earth Science Classroom
east coast
of the US.
Cold Fronts
-When cold air hits warm air.
- Warm air is forced violently up.
- Rising air creates clouds, rain, and storms.
-Heavy precipitation for a short period of time likely.
(FRONTAL LIFTING)
Mr. Fetch’s Earth Science Classroom
Cold Fronts
-When cold air hits warm air.
- Warm air is forced violently up.
- Rising air creates clouds, rain, and storms.
(FRONTAL LIFTING)
-Flash Animation
Cold Fronts
“COLD FRONT” … umm its gets colder , duh!
Warm Fronts
-When warm hits cold air.
- Warm air gently glides up over the cold air.
- Rising air creates clouds and showers. (Less Violent).
-Light precipitation for a longer period of time likely.
Mr. Fetch’s Earth Science Classroom
Warm Fronts
“WARM FRONT”… right, it gets warmer, good.
Stationary Front
- When a warm or cold front stops moving.
- Usually several days of clouds and showers.
Occluded Front
 Occluded
front occurs
when cold front wraps
around warm front.
SYSTEM TYPES
LOW PRESSURE: cyclones
1. form along fronts.
(Unstable)
2. rising air.
3. winds rotate counter-clockwise around low pressure systems.
4. Rainy, stormy weather
The high’s and low’s of weather…
HIGH PRESSURE: anticyclones
1. sinking air.
(Stable)
2. The sinking air stops clouds from forming.
3. winds rotate clockwise around high pressure systems.
4. Sunny, clear weather
How Thunderstorms Form
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For a thunderstorm to form, three conditions
must exist.
Abundant source of moisture
2. Mechanism to lift air so that the moisture can
condense and release latent heat.
3. Instability in the atmosphere
1.
Limit of Thunderstorm Growth
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The air in a thunderstorm will keep rising until:
1. Stable air is reached that it cannot overcome
2. Rate of condensation is not able to generate enough
latent heat to keep the cloud warmer than the
surrounding air
Three Types of Thunderstorms
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1) air mass thunderstorm-results from air rising
due to unequal heating in an air mass.
2) sea breeze thunderstorms-results from
extreme temperature differences air over land
and water.
3) frontal thunderstorms-results from advancing
cold fronts.
Stages of Thunderstorm
Development
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Three Stages
1) Cumulus
 2) Mature
 3) Dissipation
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Flash
Cumulus Stage
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Air rises vertically.
Moisture condenses into
visible cloud.
Coalescence occurs.
Mature Stage
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Precipitation falls,
cooling the air
surrounding it and
creating a downdraft.
The updraft and
downdraft creates a
convection cell.
Equal amount of updraft
and downdraft creates a
cumulonimbus cloud.
Dissipation Stage
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Warm air is gone, cooled
by downdraft.
Updraft ceases.
Lingering downdraft
persists.
Tornadoes
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A tornado is a violent,
whirling column of air in
contact with the ground.
Before touching ground
it is called a funnel cloud.
Fujita intensity scale-classifies
tornadoes from F0 to F5, F5
being the strongest wind
speeds.
Tornadoes
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Tornadoes are visible
due to dust, debris, and
condensation.
Created when wind
speed and direction
change suddenly with
height, a process called
wind shear.
Flash
Tropical Cyclones
Tropical cyclones are
large, rotating, lowpressure storms that
form over water during
summer and fall in the
tropics.
Two things to form:
1) Abundance of warm
water
2) Disturbance to lift air
and keep it rising
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Tropical Cyclones
These conditions exist in all tropical oceans
except the South Atlantic Ocean and the
Pacific Ocean west of the South American Coast.
Tropical Cyclone
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Most tropical cyclones begin as a disturbance, or
a low pressure system that occurs close to the
surface of tropical ocean.
Once the low pressure system acquires a
cyclonic rotation, it is known as a tropical
depression.
Forms of Tropical Cyclones
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0-65 km/hr-tropical depression
65-120 km/hr-tropical storm
120 km/hr +-hurricane
Saffir-Simpson hurricane scale classifies hurricanes
from Category 1 to Category 5, Category 5 having the
strongest win speeds
Flash
Hurricanes
Eye-calm center of the storm
Eyewall-band immediately surrounding
the eye that contains the strongest winds
in a hurricane.
A hurricane will last until it can no longer
produce enough energy to sustain itself.
This usually
happens when:
1) Hurricane runs over land.
2) Hurricane runs into colder water
Hurricanes
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The Saffir-Simpson hurricane scale classifies
hurricanes according to wind speed, air pressure
in the center, and potential for property damage.
It ranges from Category 1 hurricanes to
Category 5 storms, which can have winds in
excess of 155 mph.
Hurricanes
A hurricane will last until it can no longer produce
enough energy to sustain itself. This usually
happens when:
1) Hurricane runs over land.
2) Hurricane runs into colder water
Global Warming
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Global warming, a phenomenon related to the
greenhouse effect, is an increase in Earth’s average
surface temperature.
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The greenhouse effect is a natural phenomenon in
which Earth’s atmosphere traps heat in the troposphere
to warm Earth.
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Human activities, especially the burning of fossil fuels,
are largely responsible for increased levels of carbon
dioxide, which is the main greenhouse gas that causes
global warming.
Global Warming and Severe Weather
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Increased temperatures of ocean waters due to
global warming have been linked to the increase
in severity and frequency of tropical cyclones.