C18 F1

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superman237
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75166
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C18 F1
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2011-03-28 06:10:31
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Chapter 18
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  1. Precipitation
    Any form of water that falls form a cloud
  2. Latent heat
    • "hidden heat"
    • measured in joules or calories
    • stored in liquied water & not released as heat until liquid returns to solid state
    • aids in forming towering clouds seen in summer days
    • major source of energy for thunderstorms, tornadoes & hurricanes
  3. Evaporation
    • The process of changing a liquid to a gas
    • takes ~2500J to convert 1gm of water -> gas
  4. Condensation
    Where water vapor changes to the liquid state
  5. Sublimation
    The conversion of a solid directly to a gas, without passing through the liquid state
  6. Deposition
    The conversion of a vapor directly to a solid
  7. Humidity
    The general term fot the amount of water vapor in the air
  8. Saturated
    The number of vapor molecules returning to the surface will balance the number leaving
  9. Dew Point
    • The temperature to which a parcel of air would need to be cooled to reach saturation
    • For every 10oC increase, amount of water vapor need for saturation doubles, ie: 0oC contains 1/2 water vapor of saturated air of 10oC & 1/4 water vapor of saturated air of 20oC.
    • HIGH dew-point temp = moist air
    • LOW dew-point temp = dry air
  10. Hygrometer
    • The device that measures relative humidity
    • ex: psychrometer has 2 similar thermometer mounted side-by-side, one w/ wet cloth; it's swung in air---the drier the air, the more moisture evaporates & the lower the temperature of the wet bulb (because it takes the heat from the wet-bulb as the cloth dries, causing temp to drop)--not as accurate.
    • Better to use electric hygrometer, which uses electrical conductor coated w/ chemical that absorbs moisture.
  11. Why is the air in buildings so dry in the winter?
    • Increase temp = LOWERS humidity = dry air
    • Decrease temp = RAISES humidity = moist air
  12. Key Points:
    The process of changing state requires that energy is transferred in the form of heat
  13. Key Points:
    Relative humidity is simply the amount of water vapor
    in the air in relation to how much water vapor that air can hold.
    Colder air cannot hold as much water vapor as warmer air. Thus, as temperature decreases, the relative humidity will increase, and likewise, as temperature increases, the relative humidity will decrease.
    The warmer the air, the more water vapor it can hold, the higher the RH
    Relative Humidity is a ratio of the air's actual water-vapor content compared with the amount of water vapor air can hold at that temperature and pressure.

    As the temperature goes up, the relative humidity goes down. The warmer the air is, the more water it can hold(the water is in vapor form). Say its 70 degrees outside, and the relative humidity is 50%. This mean that the air is currently holding half of the water it can contain. Say the temperature goes up to 80 degrees, but the actual amount of water in the air stays the same. The warmer air can now hold more water, so the relative humidity would now be under 50%. So if its 70 and there is 80% relavitve humidity, its less humid than if its 80 and there is 80% humidity..
  14. Key Points:

    As the temperature goes up, the relative humidity goes down. The warmer the air is, the more water it can hold(the water is in vapor form). Say its 70 degrees outside, and the relative humidity is 50%. This mean that the air is currently holding half of the water it can contain. Say the temperature goes up to 80 degrees, but the actual amount of water in the air stays the same. The warmer air can now hold more water, so the relative humidity would now be under 50%. So if its 70 and there is 80% relavitve humidity, its less humid than if its 80 and there is 80% humidity..
    To summarize, when the water-vapor content of air remains constant, lowering air temperature causes an increase in relative humidity, and raising aire temperatures causes a decrease in relative humidity.
  15. Dry Adiabatic Rate
    Rate of cooling or heating applied to unsaturated air
  16. Wet Adiabatic Rate
    Slower rate of cooling caused by the addition of latent heat "hidden" which begans at condensation level
  17. Orographic Lifting
    When elevated terrains, such as mountains act as barriers to air flow.Precipitation and cloud formation usually happens and all or most of the humidity is lost before they get to the leeward side
  18. Frontal Wedging
    Where warm and cold air masses collide.
  19. Front
    The outcome of frontal wedging. Here the cooler, denser air acts as a barrier over which the warmer, less dense air rises.
  20. Temperature Inversion
    The most stable air: Air temperature is high with altitude
  21. Condensation Nuclei
    Tiny bits of particulate matter above the ground
  22. Key Points
    When air is allowed to expand, it cools, and when it is compressed, it warms
  23. Key Points
    Four mechanisms that can cause air to rise are orographic lifting, frontal wedging, convergence, and localized convective lifting
  24. Key Points
    Stable air tends to reamis in its original position, while unstable air tends to rise
  25. Key Points
    For any of these form of condensastion to ocuur, the air must be saturated
  26. Key Points
    Clouds are classified on the basis of thier form and height
  27. Cirrus
    High,white, and thin clouds
  28. Cumulus
    Clouds Consists of rounded individual cloud masses and is a sign of good weather.
  29. Stratus
    Best describes as sheets or layers that cover much or all of the sky
  30. Key Points
    Fog is defined as a cloud with its base at or very near the ground.
  31. Key Points
    For precipitaion to form, cloud droplets must grow in volume by roughly one million times
  32. Collision-coalescence process
    In warm clouds, the mechanism that forms raindrops.
  33. Key Points
    The type or precipitation that reaches Earth's suface depends on the temperature profile in the lowest of a few kilometers of thhe atmosphere
  34. Which gas is most important for understanding atmospheric processes?
    • water vapor
    • ~ 0 - 4% by volume
    • atmosphere only holds ~ 2mm deep global layer
  35. What is the range in volume percent of water in the atmosphere?
    0 - 4% by volume of atmosphere
  36. What happens during a change of state?
    matter changes from solid -> liquid -> gas, which requires the transfer of energy in the form of HEAT
  37. Melting point
    breaking of water molecules in ice crystals, forming noncrystalline subtance: liquid water
  38. How do warm and cold air compare in ther ability to hold water vapor?
    • Warm air can hold HIGH water vapor
    • Cool air can hold LESS water vapor
  39. What is relative humidity?
    • The ratio of the air's water-vapor content to its water-vapor capacity
    • The drier the air, the more moisture evaporates, the lower the temp. of the wet bulb

    • Relative humidity is simply the amount of water vapor in the air in relation to how much water vapor that air can hold. Colder air cannot hold as much water vapor as warmer air. Thus, as temperature decreases, the relative humidity will increase, and likewise, as temperature increases, the relative humidity will decrease.
    • The warmer the air, the more water vapor it can hold, the higher the RH
  40. What can change the relative humidity?
    water vapor, temperature
  41. What happens to heat during a change of state?
    It is either absorbed or released:

    gas (releases heat) ---> liquid (releases heat)---> solid

    solid (aborbes heat)-->liquid (absrobs heat --> gas
  42. How does the temperature of air influence its ability to hold water?
    • COLD air holds LESS water vapor
    • HOT air holds MORE water vapor
  43. List two ways that relative humidity describe about air?
    The warmer the air, the more water vapor it can hold, the higher the RH

    The cooler the air, the less water vapor it can hold, the lower the RH
  44. What does a low dew point indicate about the moisture content of air?
    • HIGH dew point temperatures indicate MOIST air
    • LOW dwe point temperatures indicate DRY air.
  45. What happens to air when it's compressed or allowed to expand?
    • air COMPRESS = increase temperature
    • air EXPAND = decrease temperature
  46. front
    warm air & cold air collide, producing a FRONT
  47. List four mechansims that can cause air to rise.
    • orographic lifting- mountains acting as barriers to the flow of air, forcing the air to ascend; the air cools adiabatically, and clous & precipitation may result.
    • frontal wedging- when cooler, denser air acts as a barrier over which the warmer, less dense air rises.
    • convergence- collsion of contrasting air masses forces air to rise.
    • localized convective lifting- unequal heating of Earth's surface may cause pockets of air to be warmed more than the surrounding air.
  48. stable vs unstable air
    • stable air = remains in is original position
    • unstable air = rises
  49. radiosonde
    instrument designed to collect weather data high in atmosphere,often carried by air balloons
  50. Contrast movements of stable air and unstable air.
    • stable air = remains in is original position/ resist vertical movent
    • unstable air = rises
  51. What types of weather can result when stable air rises?
    When stable air is forced above Earth's survace, the clouds that form are widespread & have little vertical thickness when compared to their horizontal dimension. There might be ligth to moderate precipitation, if any.
  52. What conditions in air favor condesation of water?
    condensation nuclei: microscopic dust, smoke, & salt particles from ocean...condensation needs a surface; therfore, dust, smoke, etc are good condensation nuclei
  53. Describe what happens to air temperature when work is done on the air to compress it.
    • temperature DROPS when EXPANDS
    • temperature INCREASES when COMPRESSED
  54. What does stability mean in terms of air movement?
    • Stable air tends to remain in its original position
    • Unstable air tends to rise
  55. Describe conditions that cause condensation of liquid water in air
    condensation nuclei must exist
  56. How are clouds classified?
    • clouds are classified based on their form & height:
    • Cirrus (curl of hair)- clouds are high, white & thin
    • Cumulus (a pile)- clouds consit of rounded indivual cloud masses; caulifower structure.
    • Stratus (layer)- sheets or layers that cover much or all of the sky
  57. List 3 levels of cloud heights:
    • high - 6000 meters; cirrus, cirrostratus(flat layers), cirrocumulus (fluffy): all high clouds are thin & white & often made of ice crystals; when cirrus clouds ared followed by cirrocumulus or cirrostatus clouds & increase coverage, may indicate approaching stormy weather
    • middle- 2000 to 6000 m, have prefix alto; rounded mass, clouds are larger & denser (altocumulus, altostratus)...Altostratus clouds create uniform white to grayish sheet covering the sky with the sun or moon visible as a bright spot; infrequent light snow or drizzle may accompany these clouds.
    • low- stratus, stratocumulus & nimbostratus; stratus coulds are unifrom, fog-like layer of clouds that frequently covers much of the sky; occaionally, these clouds may produce light preciptation. nimbus (rainy clouds) stratus (layer): nimbostratus clouds are one of the main precipitation makers.
  58. How are clouds and fogs similar and different?
    • physically & structurally are no difference b/t fog & cloud.
    • Difference is the method & place of formation:
    • Clouds result when air rises & cools adiabatically.
    • Fogs are result of radiation cooling or the movement of air over a cold surface.
    • Fog is defined as a cloud with its base at or very near the ground.
    • Fogs caused by cooling: earth's surface cools rapidly by radiation; thin layer of air in contact w/ the ground is cooled below its dew point.
  59. What must happen in order for precipitation to form?
    Cloud droplets must grow in volume by roughly one million times
  60. What controls the type of precipitation that reaches Earth's surface?
    • types of precipitation that reaches Earth's surface depends on the temperature profile in the lowest few kilometers of the atmosphere.
    • temperature profile- the air temperature changes w/ altitude.
  61. Compare and contrast clouds and fogs.
    • physically & structurally are no difference b/t fog & cloud.Difference is the method & place of formation: Clouds result when air rises & cools adiabatically.Fogs are result of radiation cooling or the movement of air over a cold surface.Fog is defined as a cloud with its base at or very near the ground.
    • Fogs caused by cooling: earth's surface cools rapidly by radiation; thin layer of air in contact w/ the ground is cooled below its dew point.
  62. Describe how the temperature profile of air near Earth's surface controls the type of precipitation that falls to the ground.
    • types of precipitation that reaches Earth's surface depends on the temperature profile in the lowest few kilometers of the atmosphere.
    • temperature profile- the air temperature changes w/ altitude.
  63. What is the source of all condensation & precipitation?
    cloud droplets: combination of microscopic particles: dust, smoke, etc

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