Download Under Pressure

Aim: What are factors
of Air Pressure?
Observe what happens…
Why do you
think the water
rushed out of
the bottom
opening and
poured out
slower on top?
Where would you find the highest
pressure in a column of air?
• the air above it
is pushing
down on the
molecules
below
• more pressure
at the bottom
• The atmosphere exerts 14.7 lbs of
pressure on us.
• Why don't we feel it?
1. What is air pressure?
• The force of air pushing on an
area or surface
2. How does temperature affect
air?
• When temperature increases, the volume of
increases
decreases
air ____________
& density ____________.
decrease
Pressure will _______________.
L
• When temperature decreases, the volume of
increases
decreases
air _____________
& density ___________.
increase
H
Pressure will ______________.
3. Measuring air pressure
a. Instrument used is called
a barometer
b. Air pressure is also called
barometric pressure
c. 2 kinds of barometers:
1) Mercury Barometer• 1st invented
• When air pressure
increases, it pushes
down on the mercury
pushing it up the tube
2) Aneroid Barometer• Means “without liquid”
• Has an airtight metal
chamber sensitive to
pressure change
• When pressure
increases, chamber is
pushed inward
• Needle on dial moves
4. Units for barometric pressure
• Measured in inches of mercury or
• *Measured in millibars (mb)
900s to 1,000s
*1in of mercury= 33.87 millibars
5. Isobars: connected points of equal air pressure
They are used to show areas of High and Low
pressure.
Isobars
• Same rules apply….
– Connect equal values
– Calculate gradient
– Steep side where lines
are closest together
Draw the isobars
6. What does a rising barometer
indicate?
• High pressureHappy weather
• Clearing or
pleasant
• Cooling temp
HOC: High Pressure Outward Clockwise
7. What does a falling barometer
indicate?
• Low pressureLousy weather
• Storm may be
coming
• Warming temp
LICC: Low Pressure Inward Counter Clockwise
High vs. Low Air
High: Anticyclone
Lows : Cyclones
Clockwise, outward
More dense
Air sinks
Good weather
Dry air
Counter clockwise, inward
Less Dense
Rising air
Moist air
Bad weather
Warm air rises, cool air sinks
Maps show us where the rising and
sinking air is…..
8. Air moves from H to L
-Creates wind
9. Pressure gradients
• Pressure Gradient - the change in air
pressure with distance.
• The windiest areas have the steepest
gradients.
• Calculate the gradient between
A – B and C – D on the following map
A
D
B
C
10. Wind barbs on station models
• Tell us direction and
speed.
The wind is
blowing from the
southeast at 1520 mph
Barometric pressure on station models
In the plotted station model the 3 digit number to the
upper right of the station circle is the barometric
pressure.
It will look like 196 for pressures 1000 millibars and
higher: and 992 for pressures below 1000.
So, 196 means 1019.6 mb and 992 means 999.2 mb.
Basically, add a 10 in front of anything starting with a 0
or 1, and a 9 for anything starting with a 9.
Convert each station and then draw the isobars.
1016, 1012, 1008 and 996, 1004, 1008
1016 mb
H
L
996 mb
1012 mb
1000 mb
1008 mb
1004 mb
How do these storms form?
It's time for a little bit of
science magic...
Aim: What are factors of air pressure?
Do Now: Copy the following in your notes
section.
1)As altitude increases, density of air
____________.
decreases
2) As altitude increases, air pressure
___________.
decreases
3)As temperature increases, air volume
___________.
increases
1. What is wind?
• Wind – the horizontal
movement of air
• ***Wind is created when
the uneven heating of
Earth’s surfaces creates
areas of high and low
pressure***.
• Air likes to move from
Higher pressure (H) to
Lower pressure (L)
2. How is wind named and
measured?
A Named by the direction and
speed from which it
comes. Ex. Westerly wind
comes from the West
B. Anemometer – measures
wind speed using cups
connected to a
speedometer
C. Wind vane – points to
direction that wind comes
from
3. What are local winds?
a. Local winds blow over short distances.
b. Part of the weather report. weather.com
c. Examples: Land breezes, sea breezes
• Observe an animation of land and sea breezes.
4. Sea and Land Breezes
• During day, warmer air
rises over the sand,
cooler air sinks over
sea.
• Air moves from water
to land = sea breeze
L
H
• During night, cooler air
sinks over the sand,
warmer air rises over
sea.
• Air moves from land to
sea = land breeze
H
L
Sea and Land breezes are local winds that
affect us near TOBAY or Jones Beach
5. Larger local breezes
• Monsoon – sea or
land breezes covering
a large area that
change directions
with the seasons
(Southeast Asia)
Monsoons
• Winter: A large land
breeze, sinking higher
pressure air over land
keeps moist air off
shore =Good weather
• Summer: A large sea
breeze, rising, moist
air from over the
ocean blows onto
land = Bad weather,
rain
Please Do
Now:
6. Global Winds
• Global winds blow over a
long distance from a
specific direction
• Created by uneven
heating of equator and
poles
– H = poles, cool, sinking
– L = equator, warm, rising
• Weather patterns are
affected by the prevailing
winds in an area.
Name the prevailing winds that
affect each area…ESRT pg 14
• Latitude – distance
from Equator
• Horse latitudes –
areas where air
sinks, at 30°N and
30°S
• Doldrums – areas
with little wind (at
the Equator)
7. Global Convection Currents
• Poles have higher
pressure (cold air)
• Equator has lower
pressure (warmer air)
• Air sinks from poles
 Equator creating
convection cells
Bands of H and L air are
created
The convection currents create a
distribution system for earth’s heat
http://www.youtube.c
om/watch?v=QbvHglF
yZbg&playnext=1&list
=PL9014F9D9475764
97
8. Why do the winds curve?
a. The Earth’s rotation
curves the global
winds.
•
•
Right in the Northern
hemisphere
Left in the Southern hemisphere
a. This is called
Coriollis Effect.
•
•
Coriolis Force: an artifact of the
earth's rotation
Observe an animation of the Coriolis
effect over Earth's surface.
9. Jet Streams
• Jet stream – bands of high speed winds
• 200 to 400 kilometers/hour
• Up near the Tropopause
• Can “stear” weather and pollution patterns
http://www.youtube.com/watc
h?v=CgMWwx7Cll4
http://www.youtube.co
m/watch?v=UFC6819LS
5w&feature=related
ESRT pg 14.
Question…
• Why do you think there are bands of wet and
dry air at the equator, 30o, 60o and 90 o?
Wet air is warmer, lower pressure, and rising,
creating clouds and rain
Dry air is cooler, higher pressure, and sinking,
creating more arid regions
10. Wind Chill factor
• Wind chill factor – increased cooling, increased
evaporation, make the temperature feel colder. The
stronger the wind, the colder you feel!
Summary: What affect do winds
have on weather?
a. Moves weather
b. Creates weather patterns (seasonal
changes)
c. Increases evaporation (dry things out)
d. Creates a wind chill (colder temperatures)
Video Reviews
Brain Pop Wind
http://www.youtube.com/watch?v=kPueXIHGQrg&feature=related
http://www.youtube.com/watch?v=fYfrWLhZy1A&feature=related