Transcript A boundary between two air masses

Day 47
Investigation 9 part 2
Air Masses and Weather Maps
Arrows and Scale
Visualization Exercise 9.1
Resources P. 85
Resources P. 85
Color and Real vs Diagram
Visualization Exercise 9.2
Resources, P. 89
Review Air Masses
• Air masses:
– Large thick bodies of air
– Uniform in temperature and humidity
–Have distinct boundaries
–Cover large areas of earth’s surface
–Reach top of the troposphere
–Names for the source region
Colliding
Air Masses
Cold air masses from the polar regions
move south and east
Air masses don’t stay
in one place
Warm air masses from the tropics
move north and east
Colliding
Air Masses
Air masses don’t stay
in one place
Movement of air masses creates opportunity for air masses of different
temperatures and humidity to collide
Meeting of Air Masses
• Remember the density bottles
• What is going on inside of the bottle?
– Denser liquid below the less-dense one
Meeting of Air Masses
• Imagine
– I reach north
– Grab a cP (continental polar) air mass
– Shrink it
– Jam it into the bottle
cP
Meeting of Air Masses
• Imagine
– I reach south
– Grab a mT (maritime tropical) air mass
– Shrink it
– Jam it into the bottle with the cP one
• What happens to the air masses?
mT
– Polar air sinks because it is denser
– Tropical Air lifts to the top because it is
less dense
cP
Air Mass Model
• Gases and liquids have fluid movement
• The liquid in the bottle represents what would
happen in real life with air masses
Fronts
• If air masses meet, a boundary forms
• Front
– A boundary between two air masses
Origin of “Fronts”
• Originated after World War 1
• Norwegian meteorologists
• The zone where 2 opposing armies clash is
called a battlefront
• The boundary - violent weather changes often
occur
Naming Fronts
• Takes the name of the air mass that is moving
faster and overtakes a slower air mass
Cold Fronts
• A boundary that forms when a cold air mass
overtakes warm air mass
Clouds form
Cold, dense air
plows under
warm, less dense
air
Warm,
humid air
rises and
cools
Weather and Cold Fronts
• Effects from cold fronts happen quickly
–Clouds form, can grow into thunderstorms
–Rain or snow can fall
• Lightening and hail
–Drop in temperature
–Pressure
increases
Cold front symbol on weather
map
A cold front
moves in
Warm Front
• The boundary that forms when
a warm air mass overtakes a
cold air mass
Can be hundreds of km long
Warm air slides up
over cold air at a
gentle slope
Weather and Warm Front
• Effects happen over long period of time
– Air pressure decreases
– Temperature rises at the
surface
– Clouds thicken and lower
(first wispy, cirrus clouds) then
others (cumulostratus,
altostratus, nimobostratus,
stratus, possibly fog)
– Rain, snow, sleet or freezing
rain begin to fall
Warm front symbol on weather
map
A warm front
moves in
Surface Observations
• Meteorologists receive
weather observations
from stations all over
the United States and
the world
• These are called
surface observations
Surface Observations
• Surface Observations include:
–Temperature
–Humidity
–Air Pressure
–Wind Speed and Direction
–Cloud Cover and Type
–Precipitation Type and Amount
Look at Weather Symbols
• Use special codes or symbols to represent
weather data on a map
• Typical weather symbol
Weather Symbol
From
which it is
blowing
Short barb = 5
knots
Long barb = 10
knots
Surface Observations
• Programmed into a computer that plots the
information on a map
• Used by meteorologist to make weather
predictions
Practice Reading Weather Maps
• Open to page 57 of your lab book and see if
you can read a weather map.