Transcript Chapter 11, Section 1

The Atmosphere
What is the atmosphere made of?
• 78% is nitrogen
• 21% is oxygen
• The remaining 1% consists of the
following: argon, hydrogen, carbon
dioxide, water vapor, and other gases.
Why is water vapor important?
• Water vapor is the gas form of water, and
without it, clouds could not form.
• Water is also the only substance in the
atmosphere that exists in three different
states, solid, gas, and liquid. (snow,
clouds, and rain)
What is ozone?
Ozone: a layer in the atmosphere that
absorbs ultraviolet radiation from the sun.
Without ozone, our skin could not tolerate
exposure to the sun for very long.
Layers of the atmosphere
• The atmosphere is made up of several
different layers.
1) Troposphere: the layer closest to the
Earth.
• This is the layer that most weathering
takes place, and most pollution collects.
• As you go from the bottom to the top of the
troposphere, it get colder.
2) Stratosphere: the layer above the
troposphere.
• This layer is made up primarily of ozone.
• Because the stratosphere absorbs a lot of
radiation, it is heated, and temperature
increases towards the top part.
Mesosphere
The layer above the Stratosphere but below the
Exosphere.
This is where you see meteors as they burn up.
Temperature decreases as you go up through this
layer.
4) Exosphere: the outermost layer of the
Earth’s atmosphere.
• Light gases such as helium and hydrogen
are found here.
• Above the exosphere lies outer space, but
there is no clear boundary between the
atmosphere and space.
The sun is the source of all energy
in the atmosphere. It gets to the
Earth in 3 ways:
1) Radiation
2) Conduction
3) Convection
Radiation
Radiation is the transfer of energy
through space by visible light and
ultraviolet radiation.
conduction: transfer of energy
when molecules collide.
• An example of conduction is when a
heated pot transfers the heat energy from
the pot to the water in the pot.
• In the same way, energy is transferred
from particles of air near Earth’s surface to
the particles of air in the lower
atmosphere.
convection: the transfer of energy
buy the flow of a heated surface.
• In a pot of boiling water, the water near the
bottom is heated first, then expands, forms
bubbles, and rises, bringing warm water to
the top.
Analyze air masses and the life cycle of weather
systems:
Planetary wind belts.
Air masses.
Classification of Air Masses
• Air masses are classified by the
region they form.
• These regions determine the
temperature and humidity of the
air mass.
• There are four regions that air
masses form:
– Continental (over land)-dry
air masses
– Maritime (over oceans)moist air masses
– Tropical (over warm
areas)-warm air
masses
– Polar (over cold areas)cold air masses
Continental Air Masses:
• Form over large land masses
• Have low humidity
• Two types :
– Continental Polar- cold and dry air mass
– Continental Tropical- warm and dry air mass
Continental Polar
Continental Tropical
Maritime Air Masses:
• Form over oceans or other large bodies of water
• This air mass has higher humidity and often brings fog to
areas.
• Two types:
– Maritime Polar- cold and moist air mass
– Maritime Tropical- warm and moist air mass
Maritime Polar
Maritime Continental
Weather Systems
• Frontal systems.
• Cyclonic systems
• Wind patterns are caused by
differences in air pressure at
different locations on the Earth.
• The unequal heating of the
Earth’s surface creates air
pressure differences .
• Low pressure belts are created
as air is heated and rises
(equatorial and low latitudes).
• High pressure belts are created
as air is cooled and falls (high
latitudes).
Fronts
• A front is a boundary between two air
masses.
• There are four types of fronts:
– Cold Front
– Warm Front
– Stationary Front
– Occulded Front
Cold Fronts
• Cold fronts form when
cold air overtakes warm
air
• The cold, dense air
pushes the less dense
warm air upward.
• If the warm front is moist
large cumulus clouds will
form.
• This can form a long line
of severe thunderstorms
called a squall line.
Warm Fronts
• Form as a cold front
leaves an area.
• Less dense warm air rises
over the cooler air.
• This rising air produces a
gradual slope with the
cool air so clouds can
extend far ahead of the
warm front causing
precipitation over large
areas.
Stationary and Occulded Fronts
Stationary Front
Occulded Front
• Formed when air
masses meet and move
very slowly or not at all.
• The cold air moves
parallel to the front.
• A fast moving cold front
overtakes a warm front.
• The warm air is lifted off
the ground.
Cyclones
• Cyclones form in midlatitudes where cold polar
air meets warm tropical
air.
• Midlatitude cyclones are
areas of low pressure
which have air moving
toward the rising air of the
low pressure region.
• In North America these
cyclones generally spin
counter clock-wise in an
easterly direction and can
last for several days.
Tornadoes
• Tornadoes are the
smallest and most violent
storms.
• They form when a
thunderstorm meets high
altitude horizontal winds.
• The winds cause the
warm, rising air in the
thunderstorm to rotate.
• The thunderstorm may
develop a narrow,
spinning cloud that may or
may not reach the ground.
Hurricanes or Tropical Storms
• Hurricanes differ from
cyclones in several ways:
– They cover a much
smaller area
– They lack warm and
cold fronts
– They are much more
violent
– They have winds that
travel 120 km/hr and
spiral inward towards
the low-pressure
center.
Formation of Hurricane
• Hurricanes develop over
warm, tropical water.
• Warm air moving over the
ocean rises rapidly,
condenses, and releases
energy.
• This energy is called
Latent Heat.
• Hurricanes cause a rise in
sea level and large waves
known as a storm surge.
Classifying Hurricanes
• Hurricanes are categorized by the SaffirSimpson Scale.
How Do Clouds Form?
Clouds form as warm air is forced
upward, expands, and cools until it
reaches its dew point.
The water vapor condenses, forming
water droplets that group together.
When millions of these droplets
collect, clouds form.
3 Ways Clouds Form
#1 Clouds form when warm air is forced up in a
convection current caused by solar radiation
heating the Earth’s surface.
#2 Clouds form when warm, moist air is forced to rise
over a mountain. The air cools and the water vapor
condenses.
#3 Clouds form when 2 air masses meet. Warmer air
is forced up over the cooler air. As the warm air cools
to its dew point, the water vapor condenses, or gets
together to form clouds.
How are clouds classified?
By SHAPE and HEIGHT
4 main cloud types
CIRRUS CLOUDS
- VERY HIGH CLOUDS MOSTLY
MADE OF ICE CRYSTALS
- THEY LOOK VERY STRINGY,
THIN, AND HAIR-LIKE
- USUALLY OCCUR IN FAIR
WEATHER AND POINT IN THE
DIRECTION THE AIR IS MOVING
Cirrus Clouds
CUMMULUS CLOUDS
- VERY PUFFY AND LUMPY
LOOKING CLOUDS
- THEY ARE LOW IN ELEVATION,
THAT INDICATES WARM AND
SUNNY WEATHER
- IF THEY ARE HIGH UP AND
TALL, THEY CAN GROW INTO
THUNDERSTORMS
CUMMULUS CLOUDS
STRATUS CLOUDS
- FLAT SHEETS OF CLOUDS
- THESE CLOUDS CAN MEAN AN
OVERCAST DAY OR STEADY RAIN
AND DRIZZLE
- THEY MAY STAY IN ONE PLACE
FOR SEVERAL DAYS
STRATUS CLOUDS
NIMBUS CLOUDS
-REALLY DARK AND LOW
CLOUDS THAT ARE EITHER
PRODUCING THUNDERSTORMS
OR ABOUT TO PRODUCE RAIN
- THEY ARE USUALLY A
COMBINATION OF ONE OR
MORE TYPES OF CLOUDS
NIMBUS CLOUDS
Prefixes for Cloud Height
Cirro: high clouds
Alto: middle elevation clouds
Strato: low clouds
Cirrostratus: high clouds that
look like fine veils. They are made of
ice crystals and sometimes appear to
form halos around the moon or sun.
Altostratus: form at middle levels
and look like thick veils or sheets of
gray or blue. If they are not too thick,
sunlight can filter through them.
They produce light, continuous
precipitation.
Nimbostratus: bring long, steady
rain, and low to the ground. They
often have streaks that extend to the
ground.
Cumulonimbus: occurs when a nimbus
cloud tows a cumulus cloud. Sometimes
they release unexpected, giant
thunderstorms.
Conditions necessary to form
rain:
Air near the ground has to
be warm to form water
vapor. Then rain droplets
will form.
Conditions necessary to form
sleet:
Air near the ground has to
be cold to form many small
ice pellets. Then sleet will
form.
Conditions necessary to form
snow:
Air near the ground has to
be cold to form
snowflakes. Then snow
will form.
Conditions necessary to form
hail:
Hailstorms are pellets of
ice that form as the ice
nuclei go up and down in
the cloud.
Sources
NOAA The National Oceanic and Atmospheric Administration
The Encyclopedia of Earth
Wikipedia
Freedigitalphotos.net
Wikimedia commons
Weather.com
www.eoearth.org