2. Earth Science Chapter 18.1 – Water in the Atmosphere

3. Ag Earth Science – Chapter 18.1
18.1 Vocabulary

4. precipitation
Any form of water that falls from a cloud

5. latent heat
The energy absorbed or released during a change in state

6. evaporation
The process of converting a liquid to a gas

7. condensation
The change of state from a gas to a liquid

8. sublimation
The conversion of a solid directly to a gas without passing through the liquid stage

9. deposition
The process by which water vapor is changed directly to a solid without passing through the liquid state

10. humidity
A general term referring to water vapor in the air but not to a liquid droplets of fog, cloud, or rain

11. saturated
The state of air that contains the maximum quantity of water vapor that it can hold at any given temperature and pressure.

12. relative humidity
The ratio of the air’s water-vapor content to its water-vapor capacity

13. dew point
The temperature to which air has to be cooled in order to reach saturation

14. hygrometer
An instrument designed to measure relative humidity

15. “A Dam Picture”

16. Water in the Atmosphere
When it comes to understanding atmospheric processes, water vapor is the most important gas in the atmosphere
Precipitation – any form of water that falls from a cloud (rain, sleet, hail, snow, etc..)

18. Water Changes in State Solid to Liquid
The process of changing state requires that the energy is transferred in the form of heat
Latent heat – “hidden” heat. The energy absorbed or released during a change in state

19. Water Changes in State Liquid to Gas
Evaporation – the process of changing a liquid to a gas
Condensation – the process where water vapor changes to a liquid

20. Water Changes in State Solid to a Gas
Sublimation – conversion of a solid directly to a gas without passing through the liquid state
Deposition – conversion of a vapor directly to a solid

21. Humidity Humidity – the amount of water vapor in the air Saturation
Saturated - The state of air that contains the maximum quality of water vapor that it can hold at any given temperature and pressure.
When saturated, warm air contains more water vapor than saturated cold air

22. Humidity Relative Humidity
Relative humidity is a ratio of the air’s actual water-vapor content compared with the amount of air can hold at that temperature and pressure.
To summarize, when the water-vapor content of air remains constant, lowering air temperature causes an increase in relative humidity, and raising air temperature causes a decrease in relative humidity.

23. Humidity
Dew Point
The temperature to which a parcel of air would need to be cooled to reach saturation

24. Humidity
Measuring Humidity
Hygrometer - A tool that measures humidity

26. Ag Earth Science – Chapter 18.2
18.2 Vocabulary

27. dry adiabatic rate
The rate of adiabatic cooling or warming in unsaturated air

28. wet adiabatic rate
The rate of adiabatic temperature change in saturated air

29. orographic lifting
Mountains acting as barriers to the flow of air, forcing the air to ascend

30. front
The boundary between two adjoining air masses having contrasting characteristics

31. temperature inversion
A layer of limited depth in the atmosphere of limited depth where the temperature increases rather than decreases with height

32. condensation nuclei
Tiny bits of particulate matter that serve as surfaces on which water vapors condenses

34. Air Compression and Expansion
Adiabatic Temperature Changes
When air is allowed to expand, it cools, and when it is compressed, it warms

35. Air Compression and Expansion
Expansion and Cooling
As you travel from earth’s surface upward through the atmosphere, the atmospheric pressure decreases.
Ascending air = cools and Descending air = warms

36. Air Compression and Expansion
Expansion and Cooling
Dry adiabatic rate – the rate of cooling or heating of dry air (fast)
Wet adiabatic rate – The rate of cooling or heating of saturated air (slow)

37. Processes That Lift Air
Four mechanisms that can cause air to rise are orographic lifting, frontal wedging, convergence, and localized convective lifting.

38. Processes That Lift Air
Orographic Lifting
Elevated terrains, such as mountains, that act as barriers to air flow (forcing air to ascend)

39. Processes That Lift Air
Frontal Wedging
Cooler, denser air acts as a barrier over which the warmer, less dense air rises
Front – boundary between two different air masses (example – cold/warm air masses)

40. Processes That Lift Air
Convergence
The collision of contrasting air masses that causes the air to rise

41. Processes That Lift Air
Localized Convective Lifting
The process that produces rising thermals (localized)

42. Stability
Stable air tends to remain in its original position, while unstable air tends to rise.
Air stability is determined by measuring the temperature of the atmosphere at various heights.

43. Stability
Air is stable when the temperature decreases gradually with increasing altitude
Temperature inversion – air temperature actually increases with height

44. Condensation
Condensation happens when water vapor in the air changes to a liquid (fog, dew, clouds)
For any form of condensation to occur, the air must be saturated
Condensation nuclei - Tiny bits of particulate matter that serve as surfaces on which water vapors condenses

46. Ag Earth Science – Chapter 18.3
18.3 Vocabulary

47. cirrus
1 of 3 basic cloud forms. Very high clouds that are thin, delicate ice-crystal clouds that have veil-like patches or thin, wispy fibers

48. cumulus
1 of 3 basic cloud forms. They are billowy individual clouds with flat bases.

49. stratus
1 of 3 basic cloud forms. They are sheets or layers that cover much or all of the sky.

50. Bergeron process
A theory that relates the formation of precipitation to supercooled clouds, freezing nuclei, and the different saturation levels of ice and liquid water.

51. supercooled water
The condition of water droplets that remain in the liquid state at temperatures well below 0 degrees.

52. supersaturated air
The condition of air that is more highly concentrated than is normally possible under given temperature and pressure conditions. (Greater than 100% humidity)

53. collision-coalescence process
A theory of raindrop formation in warm clouds (above 0 degrees C) in which large cloud droplets collide and join together with smaller droplets to form a raindrop.

55. Types of Clouds
Clouds are classified on the basis of their form and height.
Types of Clouds:
Cirrus (“a curl of hair”) – clouds that are high, white, and thin.

56. Types of Clouds
Cumulus (“a pile”) – clouds that consist of rounded individual cloud masses

57. Types of Clouds
Stratus (“a layer”) – clouds are best described as sheets or layers that cover much or all the sky

58. Types of Clouds High Clouds
Three types of clouds make up the family of high clouds (cirrus, cirrostratus, and cirrocumulus). They are very high altitude and have ice crystals. Not considered precipitation makers.

59. Types of Clouds Middle Clouds
Middle range clouds ( meters). Appear in rounded masses and are larger and denser than higher clouds. Light drizzle or snow may accompany these clouds.

60. Types of Clouds Low Clouds
Three members of the family of low clouds (stratus, stratocumulus, nimbostratus). Most common “rain” clouds as they form a layer across the sky.

61. Fog
Fog is defined as a cloud with its base at or very near the ground.
Fogs caused by cooling
When warm, moist air moves over cold areas, the cooling saturates the air below its dew point.

62. Fog Fogs caused by evaporation
When cool air moves over warm water. Evaporation moves into cool air and saturates.

63. How Precipitation Forms
For precipitation to form, cloud droplets must grow in volume by roughly one million times.
Cold Cloud Precipitation
Bergeron Process – physical processes of supercooling and supersaturation take place.

64. How Precipitation Forms
Warm Cloud Precipitation
Collision-coalescence process – water absorbing particles remove water vapor from the air at relative humidities less than 100 percent forming drops that are quite large. As they move through the cloud, they collide and join together with smaller, slower droplets.

65. Forms of Precipitation
The type of precipitation (rain, snow, sleet, and hail) that reaches the Earth’s surface depends on the temperature profile in the lowest few kilometers of the atmosphere.