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Weather
Atmospheric layers
Troposphere – weather occurs here,
closest to ground, colder as you rise; ends
with the tropopause.
Stratosphere – jet stream here; from
tropopause up warmer as you rise; ozone
layer is here. Ends with stratopause.
Mesosphere – ice clouds that burn up
meteoroids; from stratopause up , colder as
you go up. Ends with mesopause.
Thermosphere – hot layer, made of two
layers. Ionosphere where satellites and
auroras are; and Exosphere marking the
end of the atmosphere at 800 km.
Review 13: Weather
1. Meteorologist – scientists who study the
weather.
What direction do most weather systems
travel in the U.S.?
Defining weather…
 Weather is the daily
conditions of the
atmosphere
Heat Energy and the Atmosphere
 The Sun’s energy is mostly absorbed by the
Earth but some is reflected back into space
The Greenhouse Effect
 Caused by the increased amount of CO2 which is
placed there through burning fossil fuels.
arctic cod
amphipod
copepod
Krill?, amphipods?
black guillemot
harp seal
bearded seal
ribbon seal
walrus
spotted seal
ringed seal
hooded seal
GREENHOUSE EFFECT
Air pressure
 Air pressure if the force of air
pressing down on the Earth’s
surface
 Highest at sea level.
 As elevation increases (you go up)
pressure and density decreases
(air is thinner).
Air Masses
 A large body of air that has
properties similar to the
part of the Earth’s surface
over which it develops.
Air Mass Map
Fronts
 A boundary between two air
masses of different density,
moisture, or temperature.
Cold Front
Warm Front
Occluded Front
Stationary Front
Severe Weather occurs when
two different fronts collide.
Thunderstorms
Lightning
Tornadoes
How do storms begin?
Types of storms…
 Storms –violent disturbance in the
atmosphere. Marked by sudden
change in air pressure and rapid air
movement; two different fronts
collide (warm meets cold)
Winter weather…
Thunderstorms
 Thunderstorms – cold meets warm
front.
Cyclones and Anticyclones?
 Cyclones – area of low pressure
that cause rainy stormy weather.
 Anticyclones – high pressure area
that causes dry clear fair weather.
Hurricanes and Typhoons are the
same thing…
More about tornadoes…
 Great Plains – “tornado alley”.
 Average diameter - .4 km
 Length traveled – 6 km for only a few
minutes but winds can still reach more than
350 km/hour.
More Severe Weather
Hurricanes
Blizzards
Severe Weather Safety
 Watches- conditions are favorable
 Warnings- conditions already exist
 Examples- Tornadoes, Flooding,
Thunderstorms, Blizzards, Winter Mixes and
Hurricanes
Lightning – opposites attract.
Will strike the tallest positively
charged object.
Tornado Alley
Fujita Scale
Hurricane
Saffir-Simson Scale measures Hurricanes
 Two sources of
forecasting weather
– Data collected
from upper
atmosphere
– Data collected on
the Earth’s
surface
Weather Station Model
Isobars
 Isobars-connect points
of the “same”
 Examples:
temperature and wind
speed
 The further away the
lines the lower the
wind speed
Winds
 Wind is caused by unequal heating of the atmosphere
 Winds travel from high to low pressure
 Winds curve to the right in the N hemisphere and to
the left in the S hemisphere called the Coriolis effect
 Land and Sea breezes
 Local winds blow in all directions
and in short distances.
You feel the
air moving
from water to
land during
the day
You feel the
air moving
from land to
the water at
night
Warm air rises over
the land and moves
over the water
Cool air sinks
toward the land
Cool air sinks
and travels
toward the land
Warm air rises over
the water and moves
toward the land
Jet Stream
 jet stream - strong,
high speed wind that
blows from west to
east.
 Located in the
stratosphere.
Moisture in the Air
 Humidity - Water vapor or
moisture in the air.
 Dew Water – water vapor
becomes liquid water as it
condenses.
 Condensation forms clouds as
water vapor rises and cools.
MOISTURE
Weather
High-pressure system – when cold air
sinks to the ground, warms up, and
absorbs water vapor, causing sunny
skies.
Low-pressure system – when
warm air rises higher in the sky,
causing water vapor to cool and
form clouds and precipitation.
Predict what will happen if a high-humidity air mass located over an
ocean moves inland and up a mountain slope. Why do you think so?
Movement of Pressure Systems
 High Pressure
moves clockwise
and outwardly.
 Low Pressure
moves
counterclockwise
and inwardly.
Clouds
Cirrus – highest clouds
Indicate rain/snow in next 24 hours
Cumulus – bright white
wads of cotton
seen with fair weather
More on clouds
Cumulonimbus – largest
clouds. Bring heavy rain, high
winds, hail and tornadoes.
Stratus – form gray sheets
that spread across the sky
Bring heavy mist, snow
or drizzle. Cause fog.
Describe the clouds you see outside.
Do they fit any of the categories?
Precipitation types
Hail – when a raindrop freezes
and forms an icy ball before
falling to the ground.
Sleet – when a
raindrop falls from a
cloud and passes
through belowfreezing air making
a slushy blob.
Snow – when ice
crystals form in clouds
and fall to the ground
without melting.
Weather
Make a prediction. What kind of precipitation will fall if
there are:
Below-freezing temperatures in the clouds
Temp. barely above freezing on the ground?
Describe the air temperature, precipitation, winds,
and humidity during:
Winter?
Spring?
Summer?
Fall?
Weather
Wind speed is described in miles per hour.
Wind direction is the direction from which
the wind blows.
A north wind comes from the north.
The tail points
to where the
wind is coming
from.
The barbs on
the tail show
the speed of
the wind. More
barbs – faster
wind
The dot points
to the direction
the wind is
going.
Review 13: Weather
Tools to gather data
about the weather:
Thermometer – measures
temperature
Anemometer – measures
wind speed
Review 13: Weather
Tools to gather data about the
weather:
Rain Gauge – measures the
amount of precipitation
Barometer – measures air pressure
Weather Vane –
indicates wind direction
Odd-shaped clouds
Even more…
Sun dogs
Weather Stations &
Weather Map Symbols
Temperature
• Top left
number
shows the
temperature
Weather Symbol
• The symbol
between the two
numbers on the
left indicate
what the
weather is in
terms of
precipitation.
• Notice how
more
symbols
indicate
intensity
• More snow
flake symbols
=more snow
• More rain
symbols =
heavy rain
Dew Point
• The number on the
bottom left shows
the temperature the
air must be for
condensation to
occur or the Dew
Point.
• Humidity is a factor
of the dew point.
• This number will be
lower than the
actual temperature.
• Remember cold air can’t
hold moisture like warm
air
Cloud Cover
The percentage
of the circle that
is shaded in
reflects the
percentage of
cloud cover in
the sky
Similar to a pie
chart
Air Pressure •
This number is displayed
on the top right of the
weather symbol
• When the # is high or
rising, the weather is fair
because the pressure is
high
• When the # is low or
dropping, the weather is
rainy, because the
pressure is low
Wind Barb
• This shows the
direction of the
wind, it will point in
the direction the
wind is coming
from, this shows
the wind coming
from the Southeast
• The # of lines
and/or triangles
indicates the
speed of the wind
• The wind barb points in the direction it is coming FROM.
• Stronger winds have more flags, or marks
Fronts on a weather map
Warm
occluded
• Cold
Stationary
The symbols point in the direction that the front
is moving towards
Pressure symbols:
Isobars: connect areas with equal air pressure
The distance between the isobars is called the
pressure gradient • The closer the isobar
lines, the greater the
change in air pressure,
and the greater/faster
the winds speeds.
•
High pressure systems
bring clear/sunny
weather and wind flows
out and clockwise
(right)
•
Low pressure systems
bring overcast/stormy
weather and wind flows
in and counterclockwise (left)