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Weather and Climate
The Atmosphere
2.5.1Summarize information from charts
and graphs regarding layers of the
atmosphere, temperature, chemical
composition, and interaction with radiant
energy.
Weather and Climate… what’s
the difference?
● Weather
is always changing and
refers to the state of the atmosphere
at a given time and place
● Climate is based on the observations
of weather conditions over many years
and helps us describe a region
● To
understand weather and climate,
we first need to understand what our
atmosphere is made of
The Composition of the
Atmosphere
● How
old is the earth? _______
● Over this period of time the
composition of the atmosphere has
changed dramatically
● “Air” is not a single gas, it is a mixture
of gases
The Composition of the
Atmosphere
● The
most abundant gas in the
atmosphere is nitrogen
● The second most abundant is oxygen
◦ Together make up 99% of clean, dry air
● Carbon
dioxide is important for
absorbing energy in the atmosphere
● Water vapor is the source of all clouds
and precipitation and absorbs heat
given off by Earth
Composition of the
Atmosphere
● Ozone:
a form of oxygen with three
oxygen atoms bonded together
instead of just two (that’s the O2 we
breathe)
● Results from oxygen absorbing
radiation (energy) from the sun
● The ozone layer is crucial for life on
Earth because it absorbs potentially
harmful radiation
● The ozone layer allows life on Earth to
exist
The Composition of the
Atmosphere
● We
just finished talking about the
oceans, which contain water.
● Liquids are one type of fluid
● Gases are also fluids
● Most of the properties of our
atmosphere that influence weather,
climate, and life as we know it, come
from the fluid nature of the
atmosphere
● Check it out!
The Structure of the Atmosphere
● The
atmosphere
thins very quickly as
you travel away
from Earth’s surface
● The atmosphere is
divided vertically
into 4 layers based
on temperature
The Structure of the Atmosphere
● Layers
of the atmosphere
◦ The lowest = troposphere
⚫Temperature decreases as altitude increases
⚫Most important weather phenomena occur here
◦ 2nd = stratosphere
◦ 3rd = mesosphere
◦ Top = thermosphere
Atmospheric Basics
Solar Fundamentals
The Sun is the source of all energy in the
atmosphere.
● This energy is transferred to Earth and
throughout the atmosphere through
conduction, convection & radiation.
Atmospheric Basics
Solar Fundamentals
– Conduction is the transfer of energy that
occurs when molecules collide.
– Through conduction, energy is
transferred from the particles of air
near Earth’s surface to the
particles of air in the lowest layer
of the atmosphere.
– For conduction to occur,
substances must be in contact
with one another.
– Conduction affects only a very thin
atmospheric layer near Earth’s
surface.
Atmospheric Basics
Solar Fundamentals
– Convection is the transfer of energy by the flow of a
heated substance.
– Pockets of air near Earth’s
surface are heated, become less
dense than the surrounding air,
and rise.
– As the warm air rises, it expands
and starts to cool.
– When it cools below the
temperature of the surrounding
air, it increases in density and
sinks.
– Convection currents are among the
main mechanisms responsible for
the vertical motions of air, which in
turn cause different types of
Atmospheric Basics
Solar Fundamentals
– Radiation is the transfer of energy through
space by visible light, ultraviolet radiation, and
other forms of electromagnetic waves.
– The Sun is shining on, and therefore warming,
some portion of Earth’s surface at all times.
– While Earth is
absorbing solar
radiation, it is also
continuously
sending energy
back into space.
Heating of the Atmosphere
● Heat
vs. temperature
● Heat is the energy transferred from
one object to another due to
differences in temperatures.
● Bottom
line: heat is transferred
between objects because of
differences in temperature
Heating of the Atmosphere
The heating of the atmosphere comes
from solar energy
● The solar energy is transferred to Earth
through radiation
● When radiation hits an object, three
things happen
●
◦ 1. some radiant energy is absorbed
◦ 2. some radiant energy is transmitted through
substances like water and air
◦ 3. some radiant energy bounces off the
object without being absorbed or transmitted
Heating of the Atmosphere
● If
we did not have gases to absorb
solar radiation, Earth would not be a
place where we could live
● This heating of the lower layer of the
atmosphere from radiation absorbed
by heat absorbing gases is called the
greenhouse effect
● … so just like plants grow better in a
greenhouse, all life on Earth is able to
flourish because of the greenhouse
effect
Heating of the Atmosphere
●
●
●
●
●
The temperatures we experience are due to
the amount of heating of the atmosphere
above us and the ground and water around
us.
Land heats and cools more rapidly than
water
Land also reaches higher and lower
temperatures than water
The temperature of the land and water
influences the temperature of the air above it
This explains why inland areas experience
greater temperature variations than cities
near large bodies of water
Think about it!
● City
A is located on the Outer Banks
of NC and City B is located inland.
Which city would experience greater
variations in temperature and why?
Air Masses and Weather
● Weather patterns result from the movement of large
bodies of air called air masses
● Air masses are characterized by similar
temperatures and amounts of moisture at
certain altitudes.
● When air masses move, the characteristics of the air
mass change and the weather in the areas over which
they move changes
Starts off at 460C
Ends up at
700C
Air Masses and Weather
○
○
○
○
Example of air mass/weather interaction:
A cold, dry air mass moves over warm, tropical waters
The air mass becomes warmer and wetter
The weather over those waters becomes colder and drier
You try…
○ A warm, dry air mass moves over a cold, wet area
○ The air mass becomes ______________ and
_______
○ The weather over that area becomes ____________
and ____________
When air masses meet… Fronts
● When two air masses meet, they form a front- the boundary
that separates the two
● There are 4 types of fronts
○ Warm fronts
○ Cold fronts
○ Stationary fronts
○ Occluded fronts
Fronts
● Warm fronts
Form when warm air moves into an area
formerly covered by cold air
○ Shown on a weather map by a red line
with semi-circles pointing toward the
colder air
○
Warmer air
Colder air
Fronts
● Warm front
Fronts
● Warm fronts
○
As the warmer, less dense air
rises, it cools
→This produces clouds and frequent
precipitation
• Warm fronts move slowly, so the
precipitation is light-to-moderate
over a large area for a long period of
time
Fronts
● Cold fronts
Form when cold, dense air moves
into an area formerly occupied by
warmer air
○ Shown on a weather map by a blue
line with triangles pointing toward
the warmer air
○
Colder air
Warmer air
Fronts
● Cold Front
Fronts
● Cold Fronts
Move much more quickly than warm
fronts
○ Associated with heavy precipitation that
is short-lived
○
Fronts
● Stationary Fronts
Form when the flow of air is neither
toward the cold air mass, nor toward
the warm air mass
○ The front does not move
○ Shown by blue triangles on one side
and red semicircles on the other
○
○
Gentle to moderate precipitation
Fronts
● Occluded Front
Forms when a cold front overtakes a
warm front
○ Complex weather patterns
○
Severe Storms
● Thunderstorms
○
Develop when warm, humid air rises
in an unstable environment
Warm air
Heavy rain
Severe Storms
● Tornadoes
Violent windstorms
○ Form as a vortex extends down from a
cumulonimbus cloud
• A vortex is a rotating column of air
○
•
Most tornadoes form along with severe
thunderstorms
Severe Storms
● Tornadoes
Tornado Watches: there is the possibility
of a tornado in the area
○ Tornado Warning: a tornado has been
spotted in the area or is indicated by
radar
○
Damage Caused by Tornadoes
● Extremely high winds can tear buildings apart, slip
cars, and even suck the water out of a riverbed
● HurricanesSevere Storms
A hurricane is a large, rotating
tropical weather system with wind
speeds of at least 74 mph
○ Hurricanes are the most powerful
storms on Earth
○ In other countries they are also
known as typhoons and cyclones
○
How Do Hurricanes Form?
● A hurricane begins
as a group of
thunderstorms
moving over
tropical ocean
waters
● Winds traveling in
two different
directions collide
causing the storm
to spin
● Warm water gives
the storm energy
and causes it to
grow
Structure of a Hurricane
The eye is a zone of
scattered clouds and
calm averaging
about 20 kilometers
in diameter at the
center of a hurricane.
The eye has the
warmest
temperatures.
The eye wall is a doughnut-shaped area of intense
cumulonimbus development and very strong winds that
surrounds the eye of a hurricane.
Damage Caused by Hurricanes
● Hurricane winds can knock
down trees and telephone
poles
● However, the most damage
during a hurricane comes
from flooding due to heavy
rain and storm surges
● A storm surge is a wall of
water that builds up over the
ocean and can be up to 20
feet before it crashes onto the
shore
2.5.4c Moisture, Precipitation,
and Clouds
Water in the Atmosphere
●Water
exists in three different forms.
●What are they?
1. SOLID Examples: Snow, ice
2. LIQUID Examples: Rain, water
3. GAS Examples: Clouds, water vapor
●How
do each of these forms of water
influence weather?
Water in the Atmosphere
●
When it comes to understanding
atmospheric processes, water vapor
is the most important gas in the
atmosphere.
●
Why do you think water vapor is so
important?
Water in the Atmosphere
●Even
though water vapor is important, it
only makes up from 0 – 4% of the
atmospheric gases.
●When
have you felt water vapor at close to
4%?
●What about 0%?
●How do you know?
◦Water vapor is the HUMIDITY that you feel in
the air!
Water in the Atmosphere
●What
do you think the word
“SATURATED” means?
●What
do you think it would mean if air
is Saturated?
●Air
that has reached its water vapor
capacity is said to be saturated.
Water in the Atmosphere
●Warm,
saturated air contains more
water vapor than cold air
●Dew point is the temperature to which
air is cooled to reach saturation.
◦The point at which condensation can
occur
●When
have you noticed the humidity
more, in the summer or in the winter?
●That’s because warm air can hold
more water vapor!
Water in the Atmosphere
humidity is the ratio of air’s
water-vapor content to its capacity to hold
water vapor at that same temperature.
●Relative humidity indicates how near the
air is to saturation, not the actual quantity of
water vapor in the air.
●Relative Humidity varies with
temperature.
●Cooling air increases its relative humidity.
●Warming air decreases its relative
humidity.
●Relative
Water in the Atmosphere
●Why
does lowering the air temperature
cause Relative humidity to increase?
◦Because colder air cannot hold as much water
vapor!
●Why
does increasing air temperature
cause relative humidity to decrease?
◦Because warm air can hold more water vapor
and it will take more water vapor for it to
become saturated.
Lifting Air
●When
air is compressed the air
molecules move faster and the
temperature rises.
●Air compression causes changes in
temperature even though heat isn’t
added or subtracted.
●When air is allowed to expand, it
cools.
●When air is compressed, it heats up.
Lifting Air
Orographic Lifting
●Orographic lifting occurs when
mountains act as barriers to the flow
of air, forcing the air to ascend.
1.
Lifting Air
How does the relatively flat areas form
clouds?
2.
Frontal Wedging
●A
front is the boundary between two
adjoining air masses having
contrasting characteristics.
Lifting Air
Convergence
●Convergence occurs when two air
masses converge. The air flows
together and rises.
3.
Lifting Air
Localized Convective Lifting
●Localized convective lifting occurs
where unequal heating on earth’s
surface causes pockets of air to rise.
4.
Lifting Air
Cool, expanded
air
Warm, compressed
air
Clouds form
because as you
go up in
elevation, it gets
colder.
Cold air cannot
hold as much
water vapor so
it transforms
into clouds.
Lifting Air – Creating Clouds
●When
air expands to form clouds, the
water vapor is transformed to clouds by
condensation.
●Generally,
there must be a surface for
water vapor to condense on.
●Condensation
nuclei are tiny bits of
matter that serve as surfaces on which
water vapor condenses when
condensation occurs in the air.
●Examples
of condensation nuclei include
dust, smoke and salt particles.