Ch.18 Notes Mc Neely 2009
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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.
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Ch.18 Notes Mc Neely 2009
- 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
- 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
- 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)
- 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/
- 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
- 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