Download Weather - Bremen High School District 228

Chemistry 2014
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Weather- “the state of the atmosphere with
respect to heat or cold, wetness or dryness,
calm or storm, clearness or cloudiness”.
Climate – “the average course or condition of
the weather at a place usually over a period of
years (at least 30 yrs) as exhibited by
temperature, wind velocity, and precipitation”
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Temperature
 Ships
Dewpoint
 Buoys
Barometric Pressure  Commercial Aircraft
(ACARS)
Wind Speed and
Direction
 Satellite
Cloud Cover & Type
All of this data goes into
Present Weather
forecast models
• A thermometer
measures temperature,
or how hot or cold the
air is.
• A rain gauge measures
how much rain or snow
has fallen.
• Barometers
are used to
measure air
pressure
• A wind vane shows
which direction the wind
is blowing. It points to
the direction the wind is
coming from.
• An anemometer
measures how fast
the wind is
blowing.
Beaufort Wind Speed
Scale is has a range
from 0 for calm
to 12 for a hurricane
with waves greater than
37 feet
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Amount and height
Cloud type is done by sight only
More on this later 
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Why is there wind? Why does it blow from one
direction one day and another the next?
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Why is it rainy one day and dry the next?
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How come it’s cold in the winter?
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How can we have hail in the summer?
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What causes snow and freezing rain?
Earth’s Atmosphere
exosphere—contains few particles that move into and from space.
thermosphere—temperature increases with height. low air pressure
The International Space Station orbits Earth in this layer.
mesopause—boundary between mesosphere and thermosphere; coldest place on
Earth.
mesosphere—the layer in which most meteors burn up
stratosphere—contains the ozone layer; the layer where volcanic gases can affect
the climate
troposphere—layer closest to
Earth’s surface
-Most atmospheric mass
-Where weather occurs
-Where air pollution collects
-Temperature decreases with
height
Notice layers of atm
where temp increases
with altitude and where
temp decreases with
altitude
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Daily concerns – what to wear, flight delays, etc
Travel
Agriculture and Food concerns
Safety
Insurance and property damage
Future
You might pick heat or sun….but another good
choice would be
Convection
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Since warmed air has more
space between the
molecules (expands), it’s
less dense and rises
Cooled air is more dense
(condenses) and tends to
sink
◦ In general, air near the equator
tends to rise and air near the
poles tends to sink
Jet streams are usually found
somewhere between 10-15 km (6-9 mi)
above the earth's surface
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As solar energy reaches the Earth, equatorial
regions heat up more than the poles.
Warm air and water at the equator travel
pole-ward while cold air and water at the
poles travel equator-ward in an attempt to
equalize this temperature contrast.
It is the atmosphere's continual struggle for
temperature balance that brings us our
changing weather.
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Additionally, the rotation
of the earth creates the
Coriolis effect.
The Coriolis effect
causes the air and water
to be deflected to the
right, north of the
equator.
This creates global
weather highways
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Because of our latitude,
most of our weather
comes from the west
Looking at the top
weather map, what type
of weather might we
expect?
What type of weather
might we expect in a few
days?
What is the
prediction for
this weather
map?
1. Weather occurs in the _____ layer of the
atmosphere.
2. Transfer of heat in liquids or gases is_____
3. _____ air is dense and tends to sink.
4. Cold air holds _____ moisture than warm air
5. The Coriolis effect causes the air and water
to be deflected to the _____ of the equator
1. TROPOSPHERE
2. CONVECTION
3. COLD
4. LESS
5. RIGHT
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Ok, so we know that the weather moves around
on these highways and that warm air rises and
cold air sinks.
But why is it sunny one day, and rainy the next?
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air pressure is caused by the weight of the air
pressing down on the Earth, the ocean and on
the air below
the pressure depends on the amount of air
above the measuring point and falls as you go
higher
air pressure changes
with weather
The lowest atmospheric pressure is
found at the center of a
low pressure system, labeled with
a capital L on a weather map.
L
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air in a high pressure area compresses and
warms as it descends (drops)
the warming inhibits the formation of clouds,
meaning the sky is normally sunny in highpressure areas
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haze and fog might form
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the opposite occurs in an area of low pressure
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Notice that there
are H’s and L’s on the
map
There are also blue
lines with spikes and
red lines with half
circles
Let’s take a closer
look!
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When cooler air sinks
and is warmed, the
air can hold more
moisture
This usually means
sunny skies
Winds tend to move
clockwise around a
high
H over your home area
means likely fair weather
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When warm air rises and
is cooled, the air can not
hold as much moisture
Often, these areas are
associated with
precipitation and stormy
weather
Winds tend to move
counter clockwise around
the low
L over your home area
means probably stormy
weather
An air mass is a large body of air whose
temperature and moisture are fairly similar at
a given altitude
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Fronts are boundaries separating different air
masses
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(continental polar) : cold, dry stable
(continental tropical) : hot, dry, stable air
aloft, unstable at the surface
(maritime polar) : cool, moist, unstable
(maritime tropical) : warm, moist, unstable
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Let’s look at the different fronts and their impact
on weather
Can you see the four different types of fronts on
the map?
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A warm front is warm
air displacing cool air
diagram
Shallow leading edge
warm air must
“overrun” cold air
These are usually slow
moving
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Cold air advances into
region of warm air
Intensity of
precipitation greater,
but short lived
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Clearing conditions
after front passes
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Usually approaches from
W or NW
 Surface
positions of the
front do not
move
 Often
a region
of clouds
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Cold front overtakes
warm front
Often found close to
the low pressure
center
 Write
your answers as we go
Here
we go!
1. Winds in a low pressure system move _____
around the low.
L
2. What type of front
can be found close
to point D ?
3. Which of these fronts
would you expect to have
greater precipitation,
but be short lived as
the front passes?
4. Give the name of the air mass that would
have the following characteristics:
cool, moist, unstable
5. That important weather
word that refers to the
transfer of heat.
6. This causes air and water to be deflected to
the right, north of the equator.
7. Which of the weather highways usually
controls our weather?
8. Warm air holds ( more or less ) moisture than
cold air?
9. If there is a big H on the weather map where
you live, would you expect fair or stormy
weather?
10. Generally, what happens to air near the
equator and air near the poles?
Bonus: What is wind?
H
1.
2.
3.
4.
5.
6.
Counterclockwise
Cold
Cold
Maritime polar
Convection
Coriolis Effect
7. Westerlies
8. More
9. Fair
10. In general, air near
the equator tends to
rise and air near the
poles tends to sink
Bonus: horizontal movement of air from are of
high pressure to an area of lower pressure
CLOUDS
Cloud Types
Picture taken from:
http://commons.wikimedia.org/wiki/File:Cloud_types.jpg
**** Cloud making demo?
•Rising Air
•Lifted Condensation
Level / Dew
Point
•Condensation Nuclei
-Small droplets in
the atmosphere
around which
cloud droplets can
form
•Clouds form from
millions of
droplets
Cloud Formation
Cloud Types
Cloud Types
• Low Clouds (Cumulus, Stratus)
– 0 to 2000 meters
• Middle Clouds (Altostratus, Altocumulus)
– 2000 to 6000 meters
• High Clouds
(Cirrus, Cirrocumulus, Cirrostratus)
– 6000 meters and above
• Rain Clouds
(Cumulonimbus, Nimbostratus)
Precipitation
• Coalescence
– Cloud droplets collide to form larger droplets
• Precipitation
– Rain, Snow, Sleet, Hail
Hail Formation
• 97% salt water, 3% fresh water
Severe Weather
Thunderstorms
• Can produce some of the most violent weather
conditions on Earth
• May have hail, strong winds, lightening,
thunder, rain and tornadoes
• Supercells – self-sustaining, extremely powerful
storms with intense, rotating updrafts
• Can last for several hours with updrafts up to
240km/hr
• 10% of storms are considered severe
• moist air rises due to frontal zone lifting causing
loss of heat leading to cumulus clouds with
updrafts
• severe thunderstorms occur when cold front
approaches warm front (which supplies
moisture and energy)
– winds over 60 mph
– hail > 3/4 inch
Lightning
• Electricity caused by a rapid rush of air
in a cumulonimbus cloud
• Friction between updrafts and
downdrafts separate electrons
• Positive atoms at the top of the cloud
• Negative atoms at the bottom of the
cloud
• Transfer of energy in form of heat,
sound, and light
• Lightening strikes has about million
volts
• 5x hotter than heat from sun
Thunderstorms.asf
Tornadoes
• A violent, whirling column of air in contact
with the ground
• speeds of 300 mph+
• center of tornado is
extreme low pressure
which causes
buildings to implode
• tornado alley is from
Texas to Indiana
(usually trailer homes)
Tornado Formation
• A change in wind direction and speed creates a
horizontal rotation
• Strong updrafts tilt the rotating air from
horizontal to vertical
• A tornado forms within the rotating winds
Tornadoes_.asf
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cause most property damage and loss of life
winds speeds greater that 74 mph at the
center
begin over warm oceans of the tropics
solar insolation (water >80oF) provides energy
for huge evaporation, cloud formation, and
atmospheric lifting
Severe Weather - Hurricanes
• stages
– separate thunderstorms over tropical ocean
– cyclonic circulation which causes them to pick up
more moisture and heat energy from ocean
– winds speeds of 23 to 40 mph lead to Tropical
Depression
– Tropical Storms have lower pressure and higher wind
speeds (40-75 mph)
• center is the eye
• rainfall may exceed 24 inches in 24 hours
Other Weather Phenomenon
top 30 amazing weather phenomenon (video)
http://www.youtube.com/watch?v=rDNFeILZsSg
20 amazing phenomenon (pics/explanations)
http://listverse.com/2008/04/19/20-amazing-and-unusual-weather-phenomena/
10 more amazing weather phenomenon
(pics/explanations)
http://listverse.com/2010/12/19/10-more-amazing-weather-phenomena/