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Weather
Weather vs. Climate
• Weather changes from day to
day
• One day it may be hot and dry,
the next day cold, wet, and
stormy
• Climate is the average
weather for a particular region
over a long period of time
• As the saying goes, “Climate is
what you expect and weather is
what you get”
What is Weather?
• The state of our atmosphere on a ___to day
basis, with respect to _______and_______
Answer Bank
temperature
day
precipitation
Liquid
Absorbed
Phase
released
Evaporation
• Water exists in our
atmosphere in a solid, liquid
and gas form
• In order for a liquid like
water to become a gas,
energy must be absorbed!
• If enough energy is
absorbed, the molecules can
escape, and enter the gas
phase
What is Evaporation?
• The cooling process by which
water is converted from a
liquid into a ____ (water
vapor)
• Energy is ____ and it is a
cooling process
Answer Bank
Evaporation
gas
Continuous
Liquid
Absorbed
Phase
released
Condensation
• Think of
Condensation as
evaporation in reverse
• If water vapor in the
air cools, it will turn
back into a liquid
• So, Condensation is
the process by which
water vapor in the air
is changed into liquid
water
What is Condensation?
• The process
by which
water vapor
in the air is
changed
back into
_____water
• Energy
is______
Answer Bank
Evaporation
gas
Continuous
Liquid
Absorbed
Phase
released
Humidity
• Water is in the air all
around us
• But how much?
• It all depends on how warm
the air is
• The warmer the air, the
more moisture it can hold
or contain
• The cooler the air, the less
water vapor it can contain
What is Humidity?
• A measure of the amount of _____in the air
• Warmer air can hold more water vapor
Critical thinking: Have you ever
visited a tropical location??
Was the air humid or dry???
Answer Bank
decrease
surface
altitude
droplets
Water vapor
rises
condensation
The Water Cycle
Water is now stored
in the atmosphere
water
vapor
Stored As
water
on land
flows
back
to
the
ocean
Evaporation
causes
As
rises
the
itClouds
cools, rise
through
rivers
or cool,
and
higher,
condenses,
they
water molecules
groundwater
The ocean
absorbs
dropping
turning Precipitation
back into
toA(snow,
rise
liquid, hail,
forming
rain)
radiation
(heat)
clouds
from the sun
What is the Water Cycle?
• The _______movement of water on, above, and
below the surface of the Earth through evaporation
and condensation
Answer Bank
Evaporation
gas
Continuous
Liquid
Absorbed
phase
Summarize:
• ______ is the state of our atmosphere on a
daily basis
• _______ is when water is converted from a
liquid into a gas and _______ when water vapor
(gas) in the air is changed back into liquid
water
• Humidity is A measure of the amount of
_____in the air
• The ________ _________is the continuous
movement of water on, above, and below the
surface of the Earth through evaporation and
condensation
Answer Bank
Humidity
Evaporation
Water cycle
Weather
Condensation
water
Topic: Dew point and clouds
• Objectives:
– I will know what the dew point is
– I will know what a cloud is and how we
classify them
Dew Point
• Air can only hold
so much
moisture
• Air
At acan
certain
only hold
temperature,
the
so
much moisture
dew point,
condensation
begins
• At the dew point
temperature
clouds, fog or
Dew will form
Air begins to cool at night
Eventually it will reach the Dew Point,
Temperature when condensation begins
 At the dew point temperature
Fog, clouds or dew form
Dew Point
• Remember, humidity is the
amount of water vapor in
the air
• When warm, saturated,
humid air comes in contact
with cooler surfaces, dew
forms as a result of
condensation
• Features such as grass,
leaves, and spider webs
often contain dew
What is the Dew Point?
• The temperature air needs to cool for _______to begin
• If the temperature is _____then Dew Pt., then clouds,
fog or Dew will form
Answer Bank
decrease
surface
altitude
droplets
Water vapor
rises
Condensation
below
At the dew point temperature
Fog, clouds or dew form
Clouds
• Clouds are small
collections of small
water droplets or ice
crystals that form
through condensation
or freezing
• Clouds can form either
high in our
atmosphere or near
the surface
What is a Cloud?
• A collection of small water
_____ or ice crystals
suspended in the air,
• They form from
______when the
temperature is below
the_______
Answer Bank
Dew point
surface
altitude
droplets
Water vapor
rises
Condensation
below
Cloud Classification
• Clouds are
classified by
their shape and
altitude
• The 3 basic
cloud types are:
stratus,
cumulus, and
cirrus
Stratus Clouds
• Clouds with flat bottoms that
are found close to the surface
• “Stratus” means sheet like or
layered
• Right above fog are stratus
clouds
Cumulus Clouds
• Cumulus clouds resemble
big fluffy cotton balls
• They have a flat base that
show a well-defined
condensation level
Cirrus Clouds
• Cirrus clouds have feathery
appearance and are
composed of ice crystals
• They form at high elevations
• Cirrus clouds are seen during
sunny skies and are a sign
that bad weather is on it’s
way
What are the 3 types of clouds?
• Stratus- low _____
clouds, with layered,
sheet like shape
• Cumulus-middle
altitude clouds, with
flat, _____shape
• Cirrus- ____altitude
clouds made of ____
crystals, giving them
a feather like shape
& associated with
sunny, fair weather
Answer Bank
wedging
Ice
combination
Altitude
high
convergence
fluffy
lifting
Condensation Nuclei
• Our atmosphere contains
billions of particles of dust,
pollen, ice, salt and other
materials
• Because these particles are
so small, they remain
suspended in our air
• These small particles
provide the “seed” needed
for water to condense into
water droplets
Condensation Nuclei
• Condensation nuclei
are very small
• Water molecules are
attracted the surface
of these small
particles
• The result is a typical
cloud droplet that
forms by
condensation
Dust
Particle
Salt
Crystal
Condensation Nuclei
• To give you an
idea of how
small these
particles are, we
can compare the
size of a rain
drop and cloud
droplet to the
size of a
condensation
nuclei
Water Molecules love
Condensation Nuclei!
Dust grain:
Condensation
Nuclei
Condensation
Nuclei
• Smoke particles can
serve as condensation
nuclei
• Here, a cloud forms
over a small fire
What are Condensation Nuclei?
• A solid particle (dust, pollen,
salt) in the atmosphere that
provides the _____on which
water vapor condenses
Answer Bank
decrease
surface
altitude
droplets
Water vapor
rises
Condensation
below
Summarize
• ____ clouds are low elevation clouds and have
a flat shape to them
• _____ clouds are fluffy and slightly higher than
stratus clouds
• ______ clouds are high elevation clouds made
of ice crystals
• _____ _____ is the temperature at which
clouds, fog, and dew forms
• A ________ is collection of small water
droplets or ice crystals suspended in the air
• ______ ______ provide a surface for water
droplets to condense on
Answer Bank
Dew point
cloud
Humidity
Water vapor
rises
Cumulus
Cirrus
Stratus
Condensation nuclei
Topic: Cloud Foramtion
• Objectives:
– I will know the 4 ways clouds can form
– I will understand coalescence and the 4
kinds of precipitation
Cloud Formation
• When air rises it cools, condenses and
reaches the DEW POINT temperature
• Whenever humid air rises, clouds form
Convective Lifting
Dew Point
Temperature
Temperature air
needs to cool In
order for clouds,
fog & dew to form
As air rises it cools!!!!!
Orographic Lifting
Dew Point
Temperature
Mountains force air to rise, as
it rises it cools and condenses!!!!!
Covergence
Dew Point
Temperature
Temperature air
needs to cool In
order for clouds,
fog & dew to form
As air rises it cools and condenses!!!!!
Frontal Wedging
Dew Point
Temperature
Temperature air
needs to cool In
order for clouds,
fog & dew to form
Warm Light Air
Cold Heavy Air
As air rises it cools and condenses!!!!!
What caused this band of clouds to
form over the equator?
Frontal Wedging
• Cold air lifting warm
air, resulting in clouds
How did this
2 ways
cloud
form?
Convergence -2
air masses
coming together
Orographic Lifting - mountains lifting air
What are the 4 ways clouds can
form?
• When air rises it cools, condenses forming
water droplets
Answer Bank
• 4 ways air rises:
wedging
- Orographic
lifting -mountains lift air
- Frontal_____- warm air is lifted above colder air
-____________- air converges and is forced upward
- Convective______- hot air rises over hot land
combination
Altitude
high
convergence
fluffy
lifting
Precipitation
• Any moisture that
falls from the air to
Earth’s surface is
called Precipitation
• The 4 major types of
precipitation are rain,
snow, sleet, hail
What is Precipitation?
• Any _______ that falls from the air to Earth’s
surface is called Precipitation
• 4 types exist: ______,
snow, sleet, hail
Answer Bank
wedging
rain
Altitude
moisture
convergence
fluffy
Coalescence
• Ever wonder how rain drops
form?
• They form through a process
call coalescence
• A rain drop is the
combination of smaller
cloud droplets coming
together to form a large rain
droplet
• As larger droplets grow, they
fall picking up even more
small droplets in the
process
Coalescence
• How do we go
from a small
cloud droplet, to
a typical, large
raindrop
Coalescence
Rain
CloudDroplet
Droplets
Gravity pulls the heavy
Large raindrop down
What is Coalescence?
• The formation of a large rain
droplet by the ______ of
smaller droplets
Answer Bank
wedging
Ice
combination
Altitude
high
convergence
fluffy
lifting
Summarize
The 4 ways clouds can form are _______,
________, _________, and __________.
• ________ is the formation of a large rain
droplet by the combination of smaller
droplets
• ______ is any moisture that falls from the
air to Earth’s
• 4 kinds of precipitation are _____, ______,
_____ and _____
Topic: Fronts & High/Low Pressure
• Objectives:
– I will know the difference between a cold
and warm front
– I will understand the difference between
high and low pressure systems
How Air Moves
• If you recall, The sun drives our
winds due to the uneven
heating of earth
• This unequal heating creates
our global wind patterns
• Remember, hot equatorial air
moves to the cold poles by
convection, resulting in our
wind
• Then, the Coriolis Effect causes
our wind to curve and spin
• But, air also moves as a result
of pressure differences in our
atmosphere
How Air Moves
• Air moves from
areas of high
pressure (H), to
areas of low
pressure (L)
• During High
Pressure, air
sinks
• During Low
Pressure,
air rises
High vs. Low
Low Pressure
As air rises, it spins
Counter clockwise
As a result, cloudy stormy
weather forms
High Pressure
As air sinks, it
spins clockwise
As a result sunny,
clear weather forms
Where in the U.S. is sunny High pressure?
Where in the U.S. is stormy Low pressure?
Where is the stormy weather?
High vs. Low
• Wind flows from High Pressure to Low Pressure
• The greater the pressure difference, the faster the wind
High = 1020mb
Low = 990mb
Air_____, spinning
clockwise creating
Sunny clear weather
Air_____, spinning counterclockwise creating, cloudy
stormy weather
Answer Bank
temperature
tropical
cumulus
funnel
Sinks
thunder
stratus
warm
moisture
rises
Air Masses
• When air doesn’t move, it starts to take on a characteristic
temperature and humidity for that region
• An air mass is a large body of air throughout which temperature
and moisture content are similar
Cold, Dry air mass
Warm Humid Air Mass
What is an Air Mass?
• A large body of air
throughout which
temperature and
moisture content
are similar
•
Answer Bank
temperature
tropical
cumulus
4 types exist:
funnel
-Continental – form
Sinks
over land
thunder
-Maritime – form
stratus
over the ocean
warm
-Tropical – Warm,
moisture
humid
rises
-Polar – Cold, Dry
Fronts
• When 2 air masses meet they
don’t mix, they form Fronts
• Why?!
• Because they have different
Temperatures and Densities
• A cold air mass is dense and
does not mix with a warm air
mass
• There are 2 types of fronts:
Cold Front and a Warm Front
Cold Fronts
• When a cold air mass
overtakes a warm air
mass, a cold front forms
• The moving, heavier, cold
air lifts the warm air
• If the warm air is moist,
Clouds will form
• Large cumulus and
cumulonimbus form
along cold fronts
• A cold front is defined
as the area or zone
where a cold air mass
is replacing a warmer
air mass
Cold Fronts
• The side with the “teeth”
has the warmer air
• The colder air is pushing
the warmer air up
A Cold Front Approaching:
Notice the large cumulus clouds
Warm Fronts
• When a cold air mass
retreats from an area, a
warm front forms
• This warmer, lighter, less
dense air rises over the
cooler air
• A warm from has a gradual
slope, with clouds that form
as the warm air rises along
the front
• A warm front can cause rain,
and even sever
thunderstorms
• A warm front is defined as
the area or zone where a
warm air mass is replacing a
cold air mass
Warm Front
On a weather map,
Colder temperatures are
on the side of the semi
circles
Where is the warm front?
Where is the cold front?
What is the difference between
Cold Front and Warm Front?
• A cold front is when a cold
air mass is ______ a warmer
air mass and ______ Clouds
form as warm air is forced
upward
• A warm front is an area
where a ____ air mass is
replacing a cold air mass
and _______ clouds form
as warm air is forced
upward
Answer Bank
replacing
tropical
cumulus
funnel
Sinks
thunder
stratus
warm
moisture
rises
Severe Weather
• Severe weather is any
weather that may cause
property damage or loss
of life
• Severe weather may
include large quantities of
rain, lightning or hail,
strong winds, or tornadoes
• Severe weather causes
billions of dollars in
damage each year
Thunderstorms
• A thunderstorm is
accompanied by rain,
thunder, lightning, and
strong winds
• A thunderstorm is an
extreme low pressure
system
What is a Thunderstorm?
• A brief heavy storm (low
pressure) that consists
of rain, strong winds,
lightning, and________
Answer Bank
temperature
tropical
cumulus
funnel
Sinks
thunder
stratus
warm
moisture
rises
Tornadoes
• A tornado is the most
violent, and shortest
lived severe storm or
low pressure system
• It is basically a
destructive rotating
column of air that has
very high winds
producing a funnel
shaped cloud
Tornadoes
• The winds of a
tornado may reach
speed of over 400
kilometers!
• Usually everything in
a tornado’s path is
destroyed
Tornado Formation
• A tornado is the result
of warm tropical air
coming up from the
gulf of Mexico
meeting cold dry air
coming down from
Canada
Cold, dry
air mass from
Canada
Warm, humid
air mass from
Gulf of Mexico
What is a Tornado?
• A destructive, rotating
column of air that has
very high wind speeds
and that maybe
visible as a funnel
shaped cloud
• Tornadoes form when
a cold dry, polar air
mass from Canada
meets warm, wet
tropical air mass from
the Gulf of Mexico
Answer Bank
temperature
tropical
cumulus
funnel
Sinks
thunder
stratus
warm
moisture
rises
Hurricanes
• A hurricane is a tropical
storm
• Hurricanes do not have
warm and cold fronts
• Hurricanes develop over
warm tropical water where
evaporation & condensation
release a tremendous
amount of heat (latent heat)
Hurricanes
• Hurricanes are about 700
kilometers in diameter
and can have winds that
can reach up to 275
kilometers an hour along
the eye wall
• Hurricanes are the most
destructive storms on
earth
Hurricanes form of
the coast of Africa
where warm ocean
temperatures cause massive
amounts of evaporation
The trade winds blow the
hurricane toward the gulf
of Mexico & the United States
What is a Hurricane?
• A severe storm that develops
over _____ oceans and whose
strong winds of over 120 km/h
spiral in toward the lowpressure storm center
Answer Bank
temperature
tropical
cumulus
funnel
Sinks
thunder
stratus
warm
moisture
rises
Summarize
• A _____ ______ is when a cold air mass is
replacing a warmer air mass and ______
Clouds form
• A _____ ______ is an area where a warm air
mass is replacing a cold air mass and _____
clouds form
• Wind flows from _____ Pressure to ____
Pressure
• The greater the pressure difference, the
______ the wind
• High pressure systems spin_____ and low
pressure systems spin ______
Answer Bank
cumulus
Cold
low
clockwise
Counter-clockwise
Warm
Faster
high
stratus