1. Aim: What are factors of Air Pressure?

2. Observe what happens…
Why do you think the water rushed out of the bottom opening and poured out slower on top?

3. 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

5. The atmosphere exerts 14.7 lbs of pressure on us.
Why don't we feel it?

6. The force of air pushing on an area or surface
1. What is air pressure?
The force of air pushing on an area or surface

7. 2. How does temperature affect air?
When temperature increases, the volume of air ____________ & density ____________. Pressure will _______________.
When temperature decreases, the volume of air _____________ & density ___________.
Pressure will ______________.
increases
decreases
decrease L
increases
decreases
increase H

8. 3. Measuring air pressure
a. Instrument used is called a barometer
b. Air pressure is also called barometric pressure

9. c. 2 kinds of barometers: Mercury Barometer- 1st invented
When air pressure increases, it pushes down on the mercury pushing it up the tube

10. 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

11. 4. Units for barometric pressure
Measured in inches of mercury or
*Measured in millibars (mb)
900s to 1,000s
*1in of mercury= millibars

12. 5. Isobars: connected points of equal air pressure
They are used to show areas of High and Low pressure.

13. Isobars Same rules apply…. Connect equal values Calculate gradient
Steep side where lines are closest together

14. Draw the isobars

15. 6. What does a rising barometer indicate?
High pressure- Happy weather
Clearing or pleasant
Cooling temp

16. HOC: High Pressure Outward Clockwise

17. 7. What does a falling barometer indicate?
Low pressure- Lousy weather
Storm may be coming
Warming temp

18. LICC: Low Pressure Inward Counter Clockwise

19. High vs. Low Air High: Anticyclone Clockwise, outward More dense
Air sinks
Good weather
Dry air
Lows : Cyclones
Counter clockwise, inward
Less Dense Rising air Moist air Bad weather

20. Warm air rises, cool air sinks

22. Maps show us where the rising and sinking air is…..

23. 8. Air moves from H to L -Creates wind

24. 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

25. A D B C

26. 10. Wind barbs on station models
Tell us direction and speed.
The wind is blowing from the southeast at mph

27. 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 mb and 992 means 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

30. How do these storms form?

31. It's time for a little bit of science magic...

33. decreases decreases increases Aim: What are factors of air pressure?
Do Now: Copy the following in your notes section.
1)As altitude increases, density of air ____________.
2) As altitude increases, air pressure ___________.
3)As temperature increases, air volume ___________.
decreases
decreases
increases

34. 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)

35. 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

36. 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.

37. 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
During night, cooler air sinks over the sand, warmer air rises over sea.
Air moves from land to sea = land breeze L H H L

38. Sea and Land breezes are local winds that affect us near TOBAY or Jones Beach

39. 5. Larger local breezes
Monsoon – sea or land breezes covering a large area that change directions with the seasons (Southeast Asia)

40. 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

41. Please Do Now:

42. 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.
6. Global Winds

43. 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)

44. 7. Global Convection Currents
Poles have higher pressure (cold air)
Equator has lower pressure (warmer air)
Air sinks from poles  Equator creating convection cells

45. Bands of H and L air are created

46. The convection currents create a distribution system for earth’s heat

47. 8. Why do the winds curve?
The Earth’s rotation curves the global winds.
Right in the Northern hemisphere
Left in the Southern hemisphere
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.

48. 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

49. ESRT pg 14.

50. 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

51. 10. Wind Chill factor
Wind chill factor – increased cooling, increased evaporation, make the temperature feel colder. The stronger the wind, the colder you feel!

52. Summary: What affect do winds have on weather?
Moves weather
Creates weather patterns (seasonal changes)
c. Increases evaporation (dry things out)
d. Creates a wind chill (colder temperatures)

53. Video Reviews Brain Pop Wind