The document summarizes key concepts about the water cycle and atmospheric moisture. It describes the three states of water, processes like evaporation and condensation, cloud formation mechanisms including convection and orographic lifting, different cloud types classified by height and shape, and various forms of precipitation including rain, snow, hail and acid rain. Diagrams illustrate concepts like the water cycle, adiabatic processes, cloud classification and hailstone formation.

1. Moisture, Clouds, & Precipitation Ch. 18 Earth-Space Science Bremen High School Teacher : Aaron McNeely

2. Water in the Atmosphere Sec 18.1 Water vapor Water in a gas form The source of all clouds, condensation, and precipitation For weather, water vapor is the most important gas in the atmosphere Precipitation is any water, solid or liquid, that falls from the sky Water vapor is 0-4% of atmospheric gases

3. Water’s Changes of State Three states of matter: Solid, liquid, and gas Water can change between these states in earth’s atmosphere, termed the water cycle

4. Water Cycle Water constantly moves among the oceans, fresh water bodies, and atmosphere Planet-wide phenomena powered by the sun

5. Steps in the Water Cycle General Steps : Water evaporates from the ocean Water falls as precipitation upon land or ocean (cycle complete) Water that falls on land becomes run-off or soaks into the ground (infiltration) Run-off carries water directly back to the ocean in streams and rivers Groundwater eventually joins lakes and rivers Plants absorb water and release it back into the atmosphere (transpiration) Cycle complete when land-based water reaches the ocean

6. Phenomena of the Water Cycle Evaporation Precipitation Infiltration Run-off Transpiration

7. Water Cycle http://www.metoffice.com/education/images/water_cycle.jpg

8. Water’s Changes of State Evaporation—Liquid to gas Condensation—Gas to liquid Melting—Solid to liquid Freezing—Liquid to solid Sublimation—Solid to gas Deposition—Gas to solid

9. Evaporation Liquid to a gas Energy required, termed latent heat Evaporation is a cooling process, removes heat from surroundings

10. Condensation Gas to liquid Latent heat is released Ex: Cold beverage, morning car http://www.2xup-ph.org/album/discovery/condensation.jpg

11. Melting Solid to liquid Heat required, used to break bonds between water molecules Latent heat is the energy source for weather such as thunderstorms, tornadoes, and hurricanes http://www.phys.unsw.edu.au/~tonyt/dome%202003/melting%20ice.JPG

12. Freezing Liquid to solid Water releases latent heat during freezing Molecules in water become trapped in the crystal structure of ice http://www.bbc.co.uk/bristol/content/weather/2002/a2z/f/freezing_rain.shtml

13. Sublimation Solid to gas, skips liquid phase Dry ice (frozen carbon dioxide) sublimates, also freezer ice cubes can shrink Dry ice http://www.nwoutdoorgrrl.com/images/uploads/1953a.jpg

14. Deposition Gas to a solid, opposite of sublimation Frost http://fizyka.phys.put.poznan.pl/~pieransk/Physics%20Around%20Us/Frost%2001.jpg

15. Water’s Changes of State Diagram Red arrows = absorption of latent heat Blue arrows = release of latent heat

16. Humidity Water vapor in the air Saturation occurs when air holds all the water vapor that it is able to hold (at a particular temperature and pressure) Saturated warm air holds more water than cool saturated air

17. Relative Humidity A ratio of the air’s water vapor content compared to the amount it could possibly hold Expressed as a percent 100% is saturated air

18. Changes in Relative Humidity When the amount of water vapor in the air is constant: Lowering temperature increases relative humidity Raising temperature decreases relative humidity

19. Relative Humidity Example Amount air can possibly hold Assume no water is taken or added from the parcel of air Relative humidity increases just by lowering temperature Relative humidity = 7g/7g = 100% Relative Humidity = 7g/14g = 50% Actual water vapor = 7g Actual water vapor = 7g Saturation = 7g water vapor Saturation = 14g water vapor Temperature = 10 ° C Temperature = 20 ° C

20. Dew Point A measure of humidity Dew point is the temperature at which a quantity of air becomes saturated Below dew point, the air’s excess water vapor condenses as dew, fog, or clouds High dew points indicate moist air, low dew points indicate dry air (warm air holds more moisture, etc.) http://static.flickr.com/38/89402458_8dd93eeb91_m.jpg

21. Dew on a Spider Web

22. Water Vapor for Saturation Data : Table 1 on p. 506, Prentice Hall Earth Science

23. Sling Psychrometer Wet bulb Device to measure relative humidity, uses two thermometers and wet and dry bulbs

24. Adiabatic Temperature Changes (Sec 18.2) Adiabatic heating or cooling Compressing or expanding air changes temperature Compressed air is warmer ,expanded air is cooler No heat is added or removed

25. Adiabatic Cooling Rising air cools due to decrease in pressure This adiabatic cooling causes clouds to form

26. Dry & Wet Adiabatic Rates Rising air cools 10°C every 1000 meters, termed dry adiabatic cooling rate After saturation, clouds form, cooling rate drops, termed wet adiabatic (5°C for every 1000 meters)

27. Wet & Dry Adiabatic Lapse Rates http://geology.csupomona.edu/drjessey/class/Gsc101/adiabatic.gif

28. Cloud Formation by Adiabatic Cooling Cooling = 10 ° C per 1000 m Cooling = 5 ° C per 1000 m

29. Processes That Lift Air (for cloud creation) Orographic lifting Frontal wedging Convergence Local convection

30. Orographic Lifting When air is forced up the sides of mountains As the air rises, adiabatic cooling causes cloud formation and precipitation Earth’s rainiest locations are often on the windward sides of mountain ranges Leeward side of mountain range results in rain shadow desert

31. Orographic Processes Windward side Leeward side

32. Orographic Clouds http://home.online.no/~vteigen/orog2.jpg Where is the air rising?

33. Take me to your leader. http://www.lpl.arizona.edu/~jweirich/orographic_cloud.jpg

35. Frontal Wedging Warm and cold air masses collide (fronts) Warm air is forced up over the cooler air Rising air cools adiabatically creating clouds, precipitation, and storms

36. Frontal Wedging and Clouds

37. Convergence Occurs when air comes together after moving from different directions Air rises at the collision and cools adiabatically creating clouds and storms

38. Convergence and Clouds Convergence often creates storms in Florida

39. Local Convection Differences in reflectivity, e.g., asphalt road versus grassy field create areas of warmer and cooler air Rising warm air creates clouds Sinking cool air is clear Rising air also referred to as thermals Thermals affect birds and airplanes

40. Localized Convection http://raanz.org.nz/wiki/uploads/TM/tmfig041.png

41. Birds and Thermals Birds, like this condor, often sail using thermals http://img1.travelblog.org/Photos/6108/22953/t/108896-Condor-sailing-on-thermals-0.jpg

42. Convective Cells Convection cells often develop in stable air creating lumpy clouds (cumulus) separated by clear areas

43. Fair Weather Cumulus Where is air rising and sinking? http://webserv.chatsystems.com/~doswell/chasesums/05jun05_01.JPG

44. Stability Temperature inversions, air overhead is warmer, creates stability Warmer air acts as a cap over the cooler air Surface air can become stagnant and polluted, dangerous air

45. Condensation Nuclei Condensation nuclei are small particles around which water can start to condense Needed for cloud formation Microscopic dust, smoke, ocean salt, meteoritic material (space)

46. Tiny Particles http://vortex.plymouth.edu/precip/dropsizes2.jpg

47. Clouds Sec 18.3 Visible masses of tiny water droplets or ice crystals suspended in the atmosphere Latin names Classified according to form (shape) and height

48. Form and Height Three Forms: Cirrus Cumulus Stratus Heights: Low Middle (alto) High

49. Cirrus Latin for “curl of hair” High, white, and thin, resemble feathers or cotton candy Ice crystals

50. Cirrus Clouds Cirrus clouds are high, white, and thin

51. Cumulus Latin for “a pile” Rounded, lumpy cloud masses, resemble cauliflower Normally a flat base and lumpy top Water droplets

52. Cumulus Clouds http://www.lotc.com.au/images/scenes/sunset6.jpg Cumulus clouds are lumpy

53. Stratus Latin for “a layer” Flat, layered, sheet-like clouds Extensive, create gray, dismal conditions Low stratus clouds - water droplets High stratus clouds - ice crystals Often create halos around the sun or moon

54. Stratus Clouds (flat) Stratus clouds form flat layers

55. High Clouds Usually composed of ice crystals Examples : Cirrus Cirrostratus Cirrocumulus

56. Cirrostratus http://hea-www.harvard.edu/hrc.ARCHIVE/2004/2004243.000000-2004243.240000/SpaceWeather/swpod2004/28aug04/Koeman1.jpg These clouds produced a halo around the sun

57. Middle Clouds Middle clouds have the prefix alto in their names Examples : Altostratus Altocumulus,

58. Altocumulus (middle-height, lumpy) http://meteo.astronomie.cz/pic/ac06.jpg

59. Altostratus (middle, flat) http://www.mmem.spschools.org/grade5science/weather/altostratus.jpeg

60. Low Clouds Low clouds produce local weather such as rain Prefix nimbo indicates rain Examples : Stratus Stratocumulus Nimbostratus

61. Nimbostratus (rainy, low) http://met.no/met/met_lex/q_u/skyer/nimbostratus/nimbostratus_bilder/nimbostratus1.jpg

62. Vertical Clouds Vertical clouds extend through all of these height levels Example : Cumulonimbus

63. Cumulonimbus (vertical) Cumulonimbus clouds often create powerful storms http://www.meteorologia.it/Fotoatlante/foto/

64. Cloud Classification

65. Cloud Summary Table C u m u l o n I m b u s Cumulus Stratocumulus Stratus Nimbostratus Fog Low Altocumulus Altostratus Middle Cirrocumulus Cirrostratus Cirrus High

66. Fog When a cloud develops at ground level Results when the ground cools below dew point Fog condenses in low areas Also can form by evaporation when cool air moves over a warmer body of water

67. Fog in San Francisco http://i1.trekearth.com/photos/19267/100_0032-5.jpg

68. Mechanisms of Precipitation Tiny droplets of airborne moisture collect into larger masses A one million times change in volume Two processes: Bergeron process Collision-coalescence process

69. Bergeron Process Cold clouds Supercooled droplets form ice crystals Fall as precipitation Supercooling occurs when droplets of water remain in a liquid state even below the normal freezing temperature (0C)

70. Bergeron Process Diagram Ice crystal grow at the expense of cloud droplets Eventually the ice crystal becomes large enough to fall as precipitaiton (snow)

71. Collision-Coalescence Process Warm clouds Condensation nuclei collect tiny droplets of vapor Droplets succumb to gravity and fall as precipitation

72. Forms of Precipitation Function of temperature in lower atmosphere Forms of Precipitation: Rain, Snow, Sleet, Glaze, Hail

73. Rain and Snow Rain is drops of water at least 0.5mm in diameter Snow (ice crystals) will survive on the ground if surface temp is below 39 ° F (4 ° C) Snow can range from tiny crystals to large, fluffy clumps

74. Sleet & Glaze Sleet : Small particles of clear ice, fleet forms when tiny water droplets descend through a colder air layer above the earth’s surface Glaze : Fall of supercooled water droplets, can create clear ice coating on surface objects (ice storms)

75. Ice Storms http://www.bellsystemmemorial.com/images/edward_kelly_photos/red_bank_nj_ice_storm_open_wire.jpg Ice storms can result in power outages

76. Hail Solid lumps of ice produced in cumulonimbus clouds In these clouds, solid particles of ice move vertically and grow by collectiing supercooled droplets Onion-like internal layers 5-140mm in size

77. Hailstones http://www.crh.noaa.gov/arx/images/hail.061201.jpg

78. Hail Damage http://externalweb.nmt.edu/reslife/hail/hail%202/Hail%20Storm%20damage%204.jpg

79. Acid Rain Precipitation that forms in clouds containing air pollution Pollution particles act as condensation nuclei Acid rain can damage forests and stone structures http://www.terradaily.com/images/forest-acid-rain-bg.jpg

80. Acid Rain and Stonework 1908 1968