1. Local and Global Winds
AIM: How is wind created?

2. Do Now: Recall what creates areas of higher and lower air pressure.
**FACT**
Higher pressure air (H) is cooler, more clear, and drier than Lower pressure air (L) which is warmer, cloudier, and more moist.

3. Vocabulary Air pressure Local winds Global winds Prevailing westerlies
Isobars
Cyclones
Anti-cyclones
Wind Chill factor
Anemometer
Wind Vane

4. 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)

5. 2. How is wind named and measured?
Named by the direction and speed from which it comes. Ex. Westerly wind comes from the West
Anemometer – measures wind speed using cups connected to a speedometer
Wind vane – points to direction that wind comes from

6. 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.

7. 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

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

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

10. 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

11. 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

12. 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)

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

14. Bands of H and L air are created

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

16. 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.

17. 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

18. ESRT pg 14.

19. Question…
Why do you think there are bands of wet and dry air at the equator, 30o, 60o and 90 o?

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

21. 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)

22. Pressure, Wind and Weather

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

24. 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

25. Warm air rises, cool air sinks

27. Isobars
Isobars are lines on a map that connect areas of equal air pressure.
Same rules apply….
Connect equal values
Calculate gradient
Steep side where lines are closest together

28. Air moves from H to L

29. 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

30. A D B C

31. Wind barbs Tell us direction and speed.
The wind is blowing from the southeast at mph

32. Draw the isobars

33. 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