1. Air Pressure, Clouds and Weather
Laura Schofield, Ipswich Public Schools
Tina Ciarametaro, Ipswich Public Schools
University of MA, Amherst STEMS
Jan. 26, 2013

2. Today’s Driving Questions:
1) What are basis characteristics of the atmosphere?
2) What is the horizontal and vertical movement of air in a “High” and “Low?”
3) How do clouds form and what can they tell us?
4) How are temperature, pressure and clouds related?
5) Applying concepts to real-time data

3. Today’s Schedule Highs and Lows (PowerPoint & Application) Short Break
2) Clouds (PowerPoint & Application)
3) WeatherCycler (Application)
4) Real Time Data (Application and Resources

4. Earth’s Atmosphere Ocean of air **3-dimensional
We live on the bottom of this “ocean”
Air moves horizontally and vertically

5. Air Mass Body of air that covers thousands of kilometers2
Horizontally homogenous in temperature and humidity
Characteristics determined by type of surface over which the air mass resides or travels

6. Air Mass Tropical: “warm” Polar: “cold” and Continental: “dry”
Maritime: “humid”
Continental tropical (cT)
Maritime tropical (mT)
Maritime polar (mP)
Continental polar (cP)
Arctic (A)

7. Weather vs. Climate “Weather tells you what to wear on any given day;
State of atmosphere at a specific time and place, variables include:
Temperature
Humidity
Cloudiness
Precipitation
Wind (speed & direction)
Weather, of a given location, averaged over a period of time
Includes extremes in weather behavior observed during the same time period
How the weather behaves over relatively long periods of time
“Weather tells you what to wear on any given day;
climate tells you what wardrobe to have.”

8. H = “highs” or high pressure system
L = “lows” or low pressure system

9. Highs vs. Lows
High or “H,” symbol on a weather map, the center of a high pressure system - where air pressure is relatively high compared to the *air pressure in surrounding area
Low or “L” signifies the center of low pressure system - where *air pressure is relatively low compared to surrounding air
*air pressure is calibrated to sea level measurements

10. Air Pressure
Weight of a column of air above a per unit area

11. Highs are associated with fair weather
Lows are associated with stormy weather

12. Horizontal Movement at surface in Highs (anticyclone)
Air near the center of Highs flows outward toward lower pressure.
Earth’s rotation makes this air spiral outward
In the northern hemisphere and as seen from above this air moves outward and clockwise

13. Anticyclones

14. Anticyclones

15. Anticyclones

16. Anticyclones

17. Anticyclones

18. Anticyclones

19. Anticyclones

20. Anticyclones

21. Vertical Movement in a High
Air sinks from above with Highs and replaces outward spiraling air
Sinking air in Highs warms due to compression
Clouds, if present, vaporize and skies tend to clear

22. Horizontal movement of air at surface in Lows (cyclone)
Air flows toward the center of a low
Earth’s rotation makes this air spiral inward
In the northern hemisphere and as seen from above this air moves inward and counter clockwise

23. Cyclones

24. Cyclones

25. Cyclones

26. Cyclones

27. Cyclones

28. Cyclones

29. Cyclones

30. Cyclones

31. Vertical Movement in a Low
Air spiraling into low produces an upward motion
Rising air expands and cools
Clouds form and precipitation can develop

32. Activity: Highs and Lows
Modeling vertical and horizontal air movements using your hands.

33. of motion & conditions of the air in which they exist
Clouds are Evidence
of motion & conditions of the air in which they exist
Cloud Appreciation Society

34. Clouds are:
Is a visible suspension of minute water droplets and/or ice crystals in the atmosphere above Earth’s surface
Fog is a cloud in contact with Earth’s surface
Clouds form as a result of condensation or deposition of water vapor in ascending air

35. Global Water Cycle
The end circulation of a fixed amount of water among Earth’s ocean, atmosphere and terrestrial reservoirs.

36. Movement of between Earth’s surface and the atmosphere
Evaporation – Process of liquid water molecules absorbing heat energy and changing to water vapor
Condensation – Process of water vapor releasing heat energy to the atmosphere and changing to liquid water
Transpiration – Process by which water is taken up by roots of plants and released as water vapor through tiny leaf pores
Sublimation – Process of ice absorbing heat energy and changing directly to water vapor
Deposition - Process of water vapor releasing heat energy to atmosphere and changing directly to ice
Precipitation – when water, in liquid or solid form falls from clouds

37. Water Vapor in the atmosphere
All air contains water vapor, although the amount can vary greatly
Amount of water vapor air can hold has a limit which is dictated by air temperature
Warmer air can “hold” more water vapor than cold air
Saturation – air can’t “hold” any more water vapor
Unsaturated air can become saturated by
a) More water vapor evaporating or
b) Cooling the air temperature****

38. Most clouds are made by the cooling of air, as air moves upward
Boundary between two air masses of different densities Also called an air front
Fronts are mapped where the boundary touches Earth’s surface

39. Fronts
Stationary front

40. Fronts
Warm front

41. Fronts
Cold front

42. Most clouds are made when air cools as it moves upward
Air Front
Moving up the slopes of a mountain or hill
Air near ground heats up causing less dense air to rise
Where surface winds converge (L) or Low

43. Clouds Sky watcher Chart
Strong vertical motions, updrafts
Long, flat clouds indicate more horizontal air motion
Shapes, numbers, sizes and motion of clouds gives us clues to what the invisible air is doing.

44. Activity: Clouds, Air Pressure and Temperature How to make a cloud appear and disappear?

45. Putting it all together

46. Current Weather Studies 1A
General info about isobars: An isobar is a line passing through locations having the same air pressure By U.S. conventions, isobars are drawn at 4-mb intervals (e.g., 996 mb, 1000 mb, 1004 mb) In Europe the convention is to use 5-mb intervals

47. CWS 1A - Drawing Isobars
Draw an isobar so that air pressure readings greater than the isobar’s value are always on one side of the isobar and lower values are on the other side
Assume a uniform pressure change between neighboring stations. E.g. a 1012-mb isobar would be drawn between 1010 and 1013 about 2/3s the way to 1010.
Adjacent isobars tend to have similar shapes. Isobars will generally align with the curves of its neighboring isobars because the horizontal changes in air pressure from place to place are usually gradual
Draw isobar until it reaches boundary of map or “closes” to form a loop
Isobars never stop or end within a data field, they never fork, or cross one another
Isobars CANNOT be skipped if their values fall within the range of air pressures reported on the map

48. CWS 1B – Air Pressure & Wind Direction
Wind direction is identified by the direction from which it is coming…
”I want to know where my air is coming from…down from the arctic or from the south.”
Air moves from higher pressure area to lower pressure area

49. Real Time Data Resources
AMS Datastreme Atmosphere
Unanalyzed (“Pressures”) with the analyzed (“Isobars & Pressures”) surface pressure maps
Weather maps and maps showing water vapor
Blue Hill Observatory in Milton, MA
National Weather Service
Supplies and other resources
Thermometers, American Meteorological Society
The WeatherCycler, The Weather School
Textbook, Weather Studies by Joseph M. Moran

50. It starts with the Teachers
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Transformed by teachers into discipline- and age-appropriate lessons
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51. PreCollege Programs Project Atmosphere Maury Project
DataStreme Atmosphere
DataStreme Ocean
DataStreme Earth’s Climate System (ECS)

52. AMS DataStreme Atmosphere