1. Temperature, Air Pressure and Wind
ES12a Temperature, Pressure and Wind
I can label a diagram that demonstrates the interaction of Earth’s atmosphere and energy transfer (conduction, convection, and radiation).
I can explain the reason for high and low pressure areas
Identify and describe the direction of local winds (land and sea breezes).
Identify and describe the direction of global winds (Tradewinds, Westerlies,
Polar Easterlies, Doldrums, Jet stream)
Read and interpret data from a thermometer and a barometer

2. Sun’s energy is transferred by:
1. Radiation
A type of energy transfer in which energy moves in waves through space and the atmosphere.

3. Sun’s energy is transferred by:
2. Conduction
A type of energy transfer in which vibrating molecules pass heat along to other vibrating molecules by direct contact
(Air is in contact with the surface below it.)

4. Sun’s energy is transferred by:
3. Convection
The movement of gases or liquids due to differences in density.
As air is heated is becomes less dense and rises.
As air is cooled is becomes more dense and sinks downward.

6. How much radiation reaches the surface?
50% reaches the Earth’s surface
25% absorbed by atmosphere on the way in
25% is reflected by clouds

7. Variations in Temperature
Radiation from sun heats the earth unevenly. This is called differential heating.
There are 3 main reasons why the earth is heated unevenly:
1. Latitude
2. Cloud and Ice Cover
3. Land-Water Heating Differences

8. Latitude and Angle of Incidence
At the Equator, the rays hit the earth at 90°. They are very concentrated there.
At higher latitudes, the rays hit the earth at a lower angle. The same amount of energy is spread out over a larger area=less heat per area

9. Cloud and Ice Cover More clouds and ice will reflect more radiation.
When a surface reflects a lot of light is has a high albedo.
Can you think of a surface that would have low albedo?

10. Nearness to a Body of Water
Water has a very high specific heat capacity.
We saw this in the Lab on Heating of Land vs. Water
This means it can absorb lot if energy before it will heat up. Oceans and lakes take a long time to heat up and long time to cool down.
This property helps water regulate the temperatures around the world.

11. Land-Water Temperatrue Controls

12. Measuring Temperature
An instrument used to measure temperature is called a thermometer.
Thermometers make use of a liquid’s ability to expand & contract.

13. Measuring Temperature
What happens to a liquid when air temperature falls?
The fluid contracts and it moves down the column.

14. Indicating Temp on Weather Map
Scientists draw lines on weather maps that connect places with the same temperature.
These lines (similar to contour lines) are called ISOTHERMS.

16. Complete the Isotherms and worksheet before continuing.

18. Part II: Air Pressure

19. What is Air Pressure?
Atmospheric pressure = force of air pressing down on the Earth’s surface.
Two factors influence whether air pressure will be HIGH or LOW:
1. Density of the air
2. Amount of Water Vapor present
(We will do more with water vapor in the next section)

20. How pressure works

21. 2 Factors affect Air Pressure
Temperature
Air Pressure
Hot air
Low density
Air rises
Low Pressure
Cold Air
High density
Air sinks
High Pressure
Water Vapor content
Air Pressure
High Humidity
Low Pressure
Low humidity
High Pressure
What type of air will have the lowest pressure?
What type of air will have the highest pressure?

22. Wind Blows from Hi to Low
The sun’s energy is transferred by the wind and convection
Wind is the horizontal flow of air from areas of high pressure towards regions of low pressure.
Wind Blows from Hi to Low
TEST QUESTIONs:
What is the immediate cause of wind?
What is the ultimate cause of wind?

23. Local Winds
Generally move short distances and can blow in any map direction N, S, E, W (but always hi to low)
Caused by geographic features (land, water) that produce temperature differences

25. Sea Breezes
High pressure is created over the ocean during the day and low pressure over land due to uneven heating
Air moves from the ocean to the land creating a sea breeze

27. Land Breezes
Low pressure occurs over the ocean during the night and high pressure over land due to the uneven heating of earth
This causes wind to move from the land to the ocean creating a land breeze

28. DYO-Draw your own Local Winds
Label high and low pressure areas, draw wind direction arrows write the ‘name’ of the wind.

29. How do we measure Pressure?
Use an instrument called a barometer.
Two Types:
Aneroid barometer
Mercury barometer

30. Mercury barometer Aneroid barometer

31. Reading air pressure Read the larger ‘hand’ (like hand on a clock).
__________________
The smaller hand is set by a person every three hours to see how the pressure changes over time.

32. Predicting weather using Barometric Pressure:
High Pressure (anticyclone)
fair weather
Cool, dry air descends, clear skies
Low Pressure (cyclone)
Stormy, rain or snow
Warm, moist air rises, cools, clouds form L

33. Jet Stream is the movement of Air at high altitudes.
Think of it as a fast moving river of air.

35. READING ATMOSPHERIC PRESSURE
Scientists connect areas on a weather map with the same air pressures.
These lines are called ISOBARS
Pressure Gradients describe how close isobars are together

37. Complete the back of your notes by drawing isobars!

39. The closer the isobars are to each other, the steeper the pressure change.
The steeper the slope the faster the wind blows.

40. Three factors control speed and direction of the wind.
1. Pressure differences
2. Coriolis Effect
3. Friction

41. Coriolis Effect Earth rotating causes things to be sent off course.
Northern Hemisphere – Right deflection
Southern Hemisphere – Left deflection

42. Friction
Friction resists the flow of air opposite to the direction of flow.

43. Pressure Centers High Pressure – “Anti-cyclone”
Air moves down and out.
Wind blows clockwise
Weather – Clear, Sunny, AWESOME
Low Pressure – “Cyclone”
Air moves in and up
Wind blows counter-clockwise
Weather – Rainy, Cloudy, Dreary

44. jetstream https://www.youtube.com/watch?v=C_HiBj0teRY

45. Local Winds

49. Global Atmospheric Circulation Model

50. Cyclones and Anticyclones