Meteorology
Meteorology
Listening to the chirps of crickets can
give you a rough estimate of what the
temperature outdoors is on the
Fahrenheit temperature scale. Count
the amount of chirps you hear in
fifteen seconds and add 37
Branch of the natural sciences that deals with the
Earth’s atmosphere & its related phenomena.
The 4 Factors that Cause Weather:
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Temperature
Air Pressure
Wind
Moisture
The Atmospheric Composition
Earth’s Atmosphere:
79% Nitrogen
20% Oxygen
1% Everything Else
Variable Components
 Water Vapor
 Aerosols--suspended solid
& liquid particles in the
atmosphere
 Ozone--(O3) absorbs
harmful UV radiation
Death Valley, California's temperature
has the U.S. temperature record: 134
degrees Fahrenheit
Atmospheric Layers
Troposphere - bottom layer where we live.
* Weather occurs here.
* Gets colder w/ altitude.
Stratosphere—2nd layer
* Contains the Jet Stream & Ozone layer
* Gets warmer w/ altitude.
Mesosphere—3rd layer
* Gets colder w/ altitude.
Thermosphere– 4th layer
* Ionosphere-lower part, made of charged
ions.
* Exosphere-upper part, satellites orbit at this
location.
* Van Allen Radiation Belts-layers of high
radiation that help block solar particles.
Exosphere
Thermosphere
Ionosphere
Mesosphere
Stratosphere
Troposphere
Ozone
Layer
Heating of the Earth
Unequal Heating of the Earth
Direct Sunlight Energy (comes at a 90º
angle) causes more HEAT. It occurs
most often at the equator.
Indirect Sunlight Energy (comes in at an
angle less than 90º) doesn’t produce as
much heat.
Prospect Creek, Alaska holds the U.S.
temperature record for the coldest
temperature: minus 80 degrees
Fahrenheit
Heat Transfer
Radiation
– Sun gives off light energy because of nuclear
fusion. (Fusing of 4 hydrogen atoms into a
single helium atom)
– Atmosphere absorbs most of the radiation.
– Ground absorbs the rest.
The hot and cold temperature
extremes ever recorded on
earth is over 260 degrees
Fahrenheit
Conduction--the direct transfer of heat
energy from one substance to
another.
**The warmth of the Earth’s surface
slightly warms the air that it comes in
contact with.
Convection--the transfer of heat energy
in a gas or liquid
**Warm air rises, cold air sinks
“Greenhouse Effect”-- CO2 collects in the
atmosphere & traps heat energy at the
surface. (CO2 is 0.036%)
Air Pressure
Air has mass, so its weight (gravity) pushes
down on the earth causing pressure.
Movement of Air
•Warm air expands, making it less dense so it
rises causing LOW pressure. Warm air holds
more moisture.
•Colder air contracts, making it more dense so
it sinks causing HIGH pressure. Cold air
holds less moisture.
•LOW Pressure is usually associated w/
cloudy, rainy weather.
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HIGH Pressure is usually associated w/
good/fair weather.
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Every winter around one septillion snowflakes fall from the sky! That's a one with 24 zeros following it
Measuring Pressure
• Barometer (Mercury or Aneroid) measures
the change in air pressure in either millibars
or millimeters/inches of mercury.
Wind
the movement of air from one place to another
Air moves from a HIGH pressure to LOW pressure.
Global Winds
Created by the unequal heating of the Earth’s surface,
difference in air pressure& the Earth’s rotation.
Coriolis Effect--due to the Earth’s rotation, moving
objects such as air and water will shift in a certain
direction.
Hilo, Hawaii is the
wettest city in the
United States with an
average annual
precipitation of 128
inches! To put that into
perspective, one inch
of rain falling over one
acre of land is over
27,000 gallons of
water or over 226,000
pounds of water.
Northern Hemisphere = right
Southern Hemisphere = left
Global Wind Belts
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 Trade Winds – winds
that blow from east to
west on either side of
the equator. Separated
by the Doldrums
 Prevailing Westerlies –
winds that blow from
west to east between
30o & 60o north & south
latitudes.
 Polar Easterlies - winds
that blow from east to
west in the polar
regions.
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Jet Stream
• A narrow stream of high pressure wind
found in the lower stratosphere.
• Pushes large air masses across the
globe.
Contrary to popular belief, lightning
does strike twice in the same
place. Tall buildings such as the
Sears Tower in Chicago are struck
repeatedly.
Measuring Wind
Wind Speed—Anemometer
Wind Direction--Wind Vane
Measured in mi/hr, km/hr, and knots.
A light wind is called a
"zephyr." Many poets use
the term to describe the
gentlest of breezes.
Moisture
Humidity
The measure of the amount of water vapor
in the atmosphere.
Specific Humidity--measure of the actual mass of water
vapor in a given mass of air.
Relative Humidity--ratio/percentage of the actual amount
of water vapor in a given mass of air compared to the
maximum amount of water vapor that air can hold at a
given temperature.
Psychrometer--a type of hygrometer that has a wet
bulb thermometer & a dry bulb thermometer
Dew Point Temperature--the temperature to which air
has to be cooled in order to be completely saturated
(filled) with water.
Clouds
•Suspended droplets of water that collect on
aerosols.
•Formation of clouds depend on the amount
of moisture & aerosols in the air, the air
temperature, & the stability of the air (air
pressure.)
A lightning bolt travels up to 60,000 miles per
second and can reach temperatures as high as
50,000 degrees Fahrenheit.
Cirrus – high clouds that
are thin & wispy. Made of
ice crystals.
Cirrus
Stratus – low level clouds
that
have
a layered look.
Florida has
the highest
instance of lightning fatalies;
however, over 8,300 people
have been killed by lightning
from 1940 to 1991 in the
United States.
Stratus
Cumulus – large, fluffy
clouds of vertical
development.
The prefix alto- is added
to the name of clouds
formed in the middle
cloud layer.
Bad family genes? A woman gets struck by lightning in 1995.
Three weeks prior her nephew was struck and suffered
temporary blindness. Years before in 1970 her cousin was
zapped when lighting hit her umbrella, but this wasn't the
first time, she was also struck once before in 1965. Her
grandfather was killed by lightning in 1921 and his brother
struck and killed in the 1920's
Cumulus
Altocumulus
The prefix/suffix nimbus- is added to the
name of a cloud that produces
precipitation.
Cumulonimbus
Nimbostratus
The best chance to be fatally struck by
lightning is before you see the storm as
lightning can travel horizontally over six
miles
Precipitation
Rain
Hailstones
–Form in cumulonimbus clouds
–Strong winds carry rain drops above the
freezing line.
–Rain drops freeze into ice pellets & fall.
–Stronger the wind, the larger the hailstone.
Freezing Line
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The hail stone that holds the
record for the heaviest recorded
in the USA, was found in
Coffeyville, Kansas, on
September 3, 1970. Weighing in
at 0.75 kilograms (1.67 pounds)
it had a diameter of 14.4
centimeters (5.67 inches), a
circumference of 44.5
centimeters (17.5 inches).
The largest hail stone ever
discovered was found in
Nebraska and its
circumference was that of
a soccer ball!
Sleet
•Rain freezes into an ice
pellet as it falls through
a pocket of freezing air.
Freezing Rain
•Rain falls to the ground
and freezes on contact
with the surface.
The largest tornado in the United States was around
two and a half miles wide. It happened in Nebraska in
2004. Although tornados have been reported
worldwide, most happen in the United States
Snow
This occurs when cloud droplets freeze in
the clouds and stick together forming
flakes.
Air Masses
a large body of air that is the SAME throughout
Types
**Named based on where the air formed, its
temperature, and its humidity
Maritime Polar--it forms over the Northern Atlantic and
Pacific Oceans.
*Brings COLD, MOIST air
Maritime Tropical--it forms near the equator. It brings
WARM, MOIST air.
*If it comes in contact with cooler air from the North, storms
will form.
Continental Polar--it forms over northern Canada.
It brings COLD, DRY air.
*Causes extremely cold temperatures in the
United States.
Continental Tropical--it forms over land in
Mexico. It brings HOT, DRY air.
The Enhanced Fujita Tornado scale measures wind
speeds of tornados from EF0 to an EF5. The tornado
that wiped out the center of Greensburg, Kansas
measured EF5. Only 51 EF5 tornadoes have been
recorded since 1953 and just two since 2007. The
wind speed of an EF5 tornado is over 200 miles per
hour
Fronts
• The boundary where two air
masses collide.
• The front is named for the
aggressive air mass.
Cold Front
Cold air meets and
replaces a mass of warm
air.
Fast in speed.
Form cumulus clouds.
Narrow frontal zone
Short, severe weather
Cold Front Symbol
Warm Front
Warm air mass overtakes and moves over a cold
air mass.
 Slow moving
 Forms stratus clouds
 Wide frontal zone
Warm Air
 Long periods of drizzle
 Overcast skies
Cold Air
Texas gets about 110 tornadoes each year,
the most of any U.S. state.
Warm Front Symbol
Stationary Front--neither air mass moves
* No bad weather
Stationary Front Symbol
Occluded Front--a cold front catches up with a
warm front and overtakes it
* Weather can be variable and the conditions
can change.
Cooler
Occluded Front Symbol
Cold
Warm
• What could be happening in this comic?
• Should they seek shelter?
Dry Line
Dry air invades moist air.
 Fast moving
 Narrow frontal zone
 Forms cumulus clouds
 Severe weather in
most cases
Hurricane Katrina was a category four
hurricane that hit the southern coastline of the
United States in 2005. Hurricane Camille, a
category five hit the same area less than forty
years earlier.
Moist Air
Dry Air
Dry Line Symbol
Severe Weather
• Weather that can be considered life
threatening and can cause damage to
buildings
• Includes thunderstorms, lightning, tornadoes,
flooding, hurricanes, etc.
Hurricanes are called hurricanes
if they develop in the Atlantic
Ocean. If they develop in the
Pacific Ocean, they are called
typhoons.
Watches and Warnings
Watches – a watch is issued when the
conditions for a certain type of severe
weather are possible, but not necessarily
occurring at the moment.
Warnings – a warning is issued in a specific
area where a type of severe weather is
occurring at that given moment.
The worst hurricane in U.S.
history happened in 1900 in
Galveston, Texas, where 8,000
people died
Thunderstorms
 Fast moving rainstorms that can
produce strong winds, hail,
heavy rainfall, lightning &
tornadoes.
Lightning – static electricity
caused by the separation of
electrical charges by the
collisions of rain drops & strong
winds.
The positive & negative charges
seek each other out. When they
connect, an electrical discharge
occurs creating a lightning bolt.
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Thunder – the heat generated by the
lightning bolt superheats the
surrounding air causing it to expand
so rapidly that it causes a sonic
boom.
Hurricane Andrew cost Florida and
Louisiana over $26 billion in 1992. A
category five, it was the costliest
hurricane in U.S. history.
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• Bolts of lightning can travel as far as 25 miles or more.
• Lightning kills an average of 55 people in the United States
each year.
• The only two safe places to be during a thunderstorm are in a
car or in an enclosed house that has electricity and plumbing.
• They can strike on a clear day
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"If you feel a tingling sensation, your hair stands on end or you hear
'buzzing' from nearby rocks, fences, etc., move immediately. Lightning may
be about to strike!“
Britney Wehrle was walking with a friend on a sunny, warm day when she
was suddenly struck by lightning, even though the sky above her was clear
and blue.
MONTEVIDEO, Uruguay -Lightning struck only once
- but 52 cows are dead at
an Uruguayan ranch. The
newspaper El Pais reports
that the cows had pressed
against a wire fence during
a storm when the lightning
bolt struck in the northern
state of San Jose.
• Lightning scars
Fact or Fiction?
What you wear (sneakers, rubber boots, hairpins, cleats, etc.) can
increase or decrease your chances of being struck by lightning.
Fiction. What studies have been done indicate that what you wear doesn’t make much difference
either way.
You’re safe from lightning inside a car because the rubber tires act as insulators.
Fact and Fiction. You are safe from lightning in a car if it has a metal top and sides and if the doors
and windows are shut tight. Don’t touch the car frame, steering wheel, ignition, gear shift, or radio.
The metal shell of the car conducts the electricity away and that protects you, not the tires.
Carrying an umbrella can be dangerous when lightning is present.
Fact. Anything that makes you taller increases your risk.
If lightning only hits the ground close by, you’re safe.
Fiction. When lightning hits the ground, the current spreads along the surface to a depth of a few
inches. Any fence or pipe in its path will be charged with energy for quite a distance. Any person in
its path can be injured.
Lightning travels down telephone wires.
Fact. If lightning strikes your home, the charge travels through power lines, phone lines, and
plumbing until it reaches the ground. If you’re in the bath or shower, touching an electric appliance,
or on a corded phone, you could be injured.
Tornadoes
• Funnels of high speed circulating winds
• High winds & updrafts collide creating a
circulating low pressure.
• The cloud begins to lower below the
cloud base (wall cloud.)
• The low pressure extends to the ground
picking up dust & debris forming a
tornado.
The hottest recorded temperature on
Earth was 136 degrees in El Azizia,
Libya, in 1922
Joplin, Mo. before and after the massive, deadly tornado
Hurricanes
• Tropical cyclone that has a low pressure
center (eye) with several rotating
thunderstorms & strong winds around it.
• Start as tropical depressions over warm
water in the oceans. Storm builds strength
as it travels over the warm water.
Flooding
• Kills more people in the U.S. than any other
type of severe weather.
• Caused by too much rain over an extended
period of time. It causes lakes, streams, rivers,
etc. to overflow.
Flash Flooding
• Flooding that mainly occurs in towns or cities.
• A rainstorm that dumps several inches of rain
over a short period of time causes it.
• It is too much for the ground to soak up.
• It causes low lying areas to overflow and
rushing water in other areas.
Fin