GEOG 100--Lecture 07--Water and Weather

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  • GEOG 100--Lecture 07--Water and Weather

    1. 1. GEOG 100:Physical Geography Clouds and Precipitation:The Transfer of Latent Heat
    2. 2. The Global Water Budget• Earth has a global water budget—if water is lost in one place or in one form, it is moved to another place or another form• The total amount of water (in whatever form) varies from place to place, but stays constant over the planet as a whole
    3. 3. Where is all of Earth’s water found?• Oceans = 97.2%• Glaciers = 2.0%• Underground sources (aquifers, underground pools & groundwater) = 0.5%• Lakes (half saline, half fresh) = 0.2%• Pore spaces in soil (“soil water”) = 0.04%• Atmospheric water, streams, living things = 0.01%
    4. 4. Residence Time• The amount of time a given amount of water may remain in a particular segment of the hydrologic cycle is its residence time.• Residence time can vary from hours (evaporation followed by a thundershower), to millions of years (trapped in deep aquifers)
    5. 5. Residence Time• As water changes its “residence,” it may also change state.• When water changes state it moves around latent heat. The evaporation and condensation phase changes are especially significant...
    6. 6. Residence Time• As water changes its “residence,” it may also change state.• When water changes state it moves around latent heat. The evaporation and condensation phase changes are especially significant... How about a diagram???
    7. 7. Latent Heat Transfer ice (solid) ed d se orb fre lea me bs e t re ta zi n ltin ea ea g— —g th th lat lat en en en en lat lat th th — — ea ea ion n tio t re ta sit ma bs lea po orb bli de se su ed d water vapor (gas) water (liquid) evaporation—latent heat absorbed condensation—latent heat released
    8. 8. Saturation
    9. 9. Saturation The saturation point is the point at which a given parcel of air is holding the maximum amount of water vapor that it can possibly hold at a given temperature and pressure.
    10. 10. Saturation The saturation point is the point at which a given parcel of air is holding the maximum amount of water vapor that it can possibly hold at a given temperature and pressure. – Temperature is the key!
    11. 11. Saturation The saturation point is the point at which a given parcel of air is holding the maximum amount of water vapor that it can possibly hold at a given temperature and pressure. – Temperature is the key! If the air is not saturated, evaporation can continue, as long as there is moisture available to be evaporated
    12. 12. Three Factors Influencingthe Rate of Evaporation
    13. 13. Three Factors Influencingthe Rate of Evaporation1. Temperature of the water
    14. 14. Three Factors Influencingthe Rate of Evaporation1. Temperature of the water – The warmer the water, the faster the molecules are moving and the more likely they will be able to escape the surface (evaporate)
    15. 15. Three Factors Influencingthe Rate of Evaporation
    16. 16. Three Factors Influencingthe Rate of Evaporation2. Temperature of the air
    17. 17. Three Factors Influencingthe Rate of Evaporation2. Temperature of the air – Warm air can hold more water vapor suspended in it
    18. 18. Three Factors Influencingthe Rate of Evaporation2. Temperature of the air – Warm air can hold more water vapor suspended in it – Warm air transfers heat to the water and speeds up water molecules to the point where they can evaporate
    19. 19. Three Factors Influencingthe Rate of Evaporation2. Temperature of the air – Warm air can hold more water vapor suspended in it – Warm air transfers heat to the water and speeds up water molecules to the point where they can evaporate – Cold air can hold less water as a vapor and reaches its saturation point more quickly
    20. 20. Three Factors Influencingthe Rate of Evaporation
    21. 21. Three Factors Influencingthe Rate of Evaporation3. Degree of windiness
    22. 22. Three Factors Influencingthe Rate of Evaporation3. Degree of windiness – Saturation is reached quickly right above the water
    23. 23. Three Factors Influencingthe Rate of Evaporation3. Degree of windiness – Saturation is reached quickly right above the water – Wind blowing over a wet surface will reduce saturation above that surface by moving water vapor molecules away from the surface. This leaves room for more molecules to evaporate
    24. 24. Vapor Pressure  Vapor pressure--the portion of total air pressure made up of water vapor molecules  Saturation vapor pressure--the pressure exerted by the maximum amount of water vapor a parcel of air can hold at a given temperature.11
    25. 25. Relative Humidity
    26. 26. Relative Humidity The amount of water vapor in the air at a given temperature, compared with the maximum amount of water vapor which could be in the air if it were saturated
    27. 27. Relative Humidity The amount of water vapor in the air at a given temperature, compared with the maximum amount of water vapor which could be in the air if it were saturated RH = actual/maximum x 100 = ___ %
    28. 28. Relative Humidity The amount of water vapor in the air at a given temperature, compared with the maximum amount of water vapor which could be in the air if it were saturated RH = actual/maximum x 100 = ___ % RH = relative humidity
    29. 29. Relative Humidity The amount of water vapor in the air at a given temperature, compared with the maximum amount of water vapor which could be in the air if it were saturated RH = actual/maximum x 100 = ___ % RH = relative humidity Actual = the actual amount of water vapor in the air right now
    30. 30. Relative Humidity The amount of water vapor in the air at a given temperature, compared with the maximum amount of water vapor which could be in the air if it were saturated RH = actual/maximum x 100 = ___ % RH = relative humidity Actual = the actual amount of water vapor in the air right now Maximum = the maximum amount of water vapor the air can hold at the given temperature and pressure (in other words, saturation point)
    31. 31. RH Example:
    32. 32. RH Example: If the room you’re sitting in has 5 grams of water vapor actually suspended in it, but the maximum amount of water vapor that the air could possibly hold is 10 grams, then:
    33. 33. RH Example: If the room you’re sitting in has 5 grams of water vapor actually suspended in it, but the maximum amount of water vapor that the air could possibly hold is 10 grams, then: RH = actual/maximum x 100 = ___ %
    34. 34. RH Example: If the room you’re sitting in has 5 grams of water vapor actually suspended in it, but the maximum amount of water vapor that the air could possibly hold is 10 grams, then: RH = actual/maximum x 100 = ___ %
    35. 35. RH Example: If the room you’re sitting in has 5 grams of water vapor actually suspended in it, but the maximum amount of water vapor that the air could possibly hold is 10 grams, then: RH = actual/maximum x 100 = ___ % RH = 5g / 10g x 100 = 50%
    36. 36. Relative Humidity
    37. 37. Relative Humidity What happens when relative humidity reaches 100%?
    38. 38. Relative Humidity What happens when relative humidity reaches 100%? – Saturation
    39. 39. Relative Humidity What happens when relative humidity reaches 100%? – Saturation – Condensation
    40. 40. Relative Humidity What happens when relative humidity reaches 100%? – Saturation – Condensation  Clouds or fog (if cooling continues)
    41. 41. Two Ways to ChangeRelative Humidity
    42. 42. Two Ways to ChangeRelative Humidity Change the temperature of the air
    43. 43. Two Ways to ChangeRelative Humidity Change the temperature of the air – Temperature up, RH down – Temperature down, RH up
    44. 44. Two Ways to ChangeRelative Humidity Change the temperature of the air – Temperature up, RH down – Temperature down, RH up
    45. 45. Two Ways to ChangeRelative Humidity Change the temperature of the air – Temperature up, RH down – Temperature down, RH up
    46. 46. Two Ways to ChangeRelative Humidity Change the temperature of the air – Temperature up, RH down – Temperature down, RH up
    47. 47. Two Ways to ChangeRelative Humidity Change the temperature of the air – Temperature up, RH down – Temperature down, RH up Add or subtract water vapor
    48. 48. Two Ways to ChangeRelative Humidity Change the temperature of the air – Temperature up, RH down – Temperature down, RH up Add or subtract water vapor – In the atmosphere, water is added through evaporation, or lost through precipitation (rain, snow, etc.)
    49. 49. The Dew Point The dew point is the temperature at which saturation is reached.
    50. 50. The Dew Point The dew point is the temperature at which saturation is reached.Note: The temperatureat which the dew pointis reached depends onvariables such asabsolute humidity. Forexample...
    51. 51. The Dew Point The dew point is the temperature at which saturation is reached.Note: The temperatureat which the dew pointis reached depends onvariables such asabsolute humidity. Forexample...At 10g water vapor/m3,
    52. 52. The Dew Point The dew point is the temperature at which saturation is reached.Note: The temperatureat which the dew pointis reached depends onvariables such asabsolute humidity. Forexample...At 10g water vapor/m3, dew pt. = 50℉
    53. 53. The Dew Point The dew point is the temperature at which saturation is reached.Note: The temperatureat which the dew pointis reached depends onvariables such asabsolute humidity. Forexample...At 10g water vapor/m3, dew pt. = 50℉At 20g/m3,
    54. 54. The Dew Point The dew point is the temperature at which saturation is reached.Note: The temperatureat which the dew pointis reached depends onvariables such asabsolute humidity. Forexample...At 10g water vapor/m3, dew pt. = 50℉At 20g/m3, dew pt. = 68℉
    55. 55. The Adiabatic Process t’s ing, ha enW p ap ? h e her
    56. 56. The Adiabatic Process
    57. 57. The Adiabatic Process The process by which rising air cools (as it expands) and sinking air warms (as it is compressed) in the atmosphere
    58. 58. The Adiabatic Process The process by which rising air cools (as it expands) and sinking air warms (as it is compressed) in the atmosphere The physical principle involved:
    59. 59. The Adiabatic Process The process by which rising air cools (as it expands) and sinking air warms (as it is compressed) in the atmosphere The physical principle involved: – When a gas expands, it cools
    60. 60. The Adiabatic Process The process by which rising air cools (as it expands) and sinking air warms (as it is compressed) in the atmosphere The physical principle involved: – When a gas expands, it cools – When a gas is compressed, it warms
    61. 61. The Adiabatic Process
    62. 62. The Adiabatic Process As an air mass rises through the atmosphere, it moves into an area of lower density, allowing the molecules the freedom to expand.
    63. 63. The Adiabatic Process As an air mass rises through the atmosphere, it moves into an area of lower density, allowing the molecules the freedom to expand. As air expands, there are fewer collisions between molecules and the air begins to cool.
    64. 64. The Adiabatic Process As an air mass rises through the atmosphere, it moves into an area of lower density, allowing the molecules the freedom to expand. As air expands, there are fewer collisions between molecules and the air begins to cool. So rising air expands and cools down. If the air mass cools enough to reach the dew point temperature, condensation will occur and a cloud will form.
    65. 65. The Adiabatic Process
    66. 66. The Adiabatic Process On the other hand, a sinking air mass will move down through the atmosphere into a region of increasingly more molecules of air.
    67. 67. The Adiabatic Process On the other hand, a sinking air mass will move down through the atmosphere into a region of increasingly more molecules of air. The pressure of all of these molecules will compress the air mass, forcing the molecules closer to one another.
    68. 68. The Adiabatic Process On the other hand, a sinking air mass will move down through the atmosphere into a region of increasingly more molecules of air. The pressure of all of these molecules will compress the air mass, forcing the molecules closer to one another. This increases the number of molecular collisions, speeding up the molecules, which translates into an increase in temperature.
    69. 69. The Adiabatic Process On the other hand, a sinking air mass will move down through the atmosphere into a region of increasingly more molecules of air. The pressure of all of these molecules will compress the air mass, forcing the molecules closer to one another. This increases the number of molecular collisions, speeding up the molecules, which translates into an increase in temperature. So sinking air is compressed and warms up.
    70. 70. The DAR
    71. 71. The DAR The rate at which unsaturated air will cool as it rises is called the Dry Adiabatic lapse Rate, or DAR (the air is not actually “dry”, it’s just not saturated).
    72. 72. The DAR The rate at which unsaturated air will cool as it rises is called the Dry Adiabatic lapse Rate, or DAR (the air is not actually “dry”, it’s just not saturated). Although this rate can vary based on several atmospheric variables, a commonly-used average value is:
    73. 73. The DAR The rate at which unsaturated air will cool as it rises is called the Dry Adiabatic lapse Rate, or DAR (the air is not actually “dry”, it’s just not saturated). Although this rate can vary based on several atmospheric variables, a commonly-used average value is: 10ºC/1000m (5.5ºF/1000ft)
    74. 74. The LCL
    75. 75. The LCL The lifting condensation level (LCL) is the elevation at which condensation occurs.
    76. 76. The LCL The lifting condensation level (LCL) is the elevation at which condensation occurs. As it rises, expands, and cools, the air’s relative humidity increases (getting closer to 100%) until eventually the air parcel reaches its dew point temperature.
    77. 77. The LCL The lifting condensation level (LCL) is the elevation at which condensation occurs. As it rises, expands, and cools, the air’s relative humidity increases (getting closer to 100%) until eventually the air parcel reaches its dew point temperature. At that point, saturation has been reached and a cloud begins to form.
    78. 78. The LCL The lifting condensation level (LCL) is the elevation at which condensation occurs. As it rises, expands, and cools, the air’s relative humidity increases (getting closer to 100%) until eventually the air parcel reaches its dew point temperature. At that point, saturation has been reached and a cloud begins to form. The elevation where this happens is the LCL.
    79. 79. You can “see” the LCL:
    80. 80. You can “see” the LCL:
    81. 81. You can “see” the LCL:Look at the flat bottom of the cloud
    82. 82. A Quick Reminder!
    83. 83. A Quick Reminder! The following five conditions all occur at the same time:
    84. 84. A Quick Reminder! The following five conditions all occur at the same time: Saturation
    85. 85. A Quick Reminder! The following five conditions all occur at the same time: Saturation Condensation
    86. 86. A Quick Reminder! The following five conditions all occur at the same time: Saturation Condensation RH=100%
    87. 87. A Quick Reminder! The following five conditions all occur at the same time: Saturation Condensation RH=100% Dew point temperature
    88. 88. A Quick Reminder! The following five conditions all occur at the same time: Saturation Condensation RH=100% Dew point temperature LCL (lifting condensation level)
    89. 89. The Latent Heat of Condensation
    90. 90. The Latent Heat of Condensation Once condensation occurs, the water molecules begin to give off the latent heat of condensation. This heat becomes sensible heat that can be measured.
    91. 91. The Latent Heat of Condensation Once condensation occurs, the water molecules begin to give off the latent heat of condensation. This heat becomes sensible heat that can be measured. This heat interferes with the adiabatic cooling that is going on, slowing down the cooling process. So the air continues to get colder as it rises, but it cools at a slower rate.
    92. 92. The SAR (or MAR)
    93. 93. The SAR (or MAR) The rate at which a saturated parcel of air will cool as it rises is called the Saturated Adiabatic lapse Rate, or SAR (also called the MAR, or moist adiabatic lapse rate) Again, the rate varies, but we’ll use an average value of:
    94. 94. The SAR (or MAR) The rate at which a saturated parcel of air will cool as it rises is called the Saturated Adiabatic lapse Rate, or SAR (also called the MAR, or moist adiabatic lapse rate) Again, the rate varies, but we’ll use an average value of: 5ºC/1000m (3.3ºF/1000ft)
    95. 95. The SAR (or MAR) The rate at which a saturated parcel of air will cool as it rises is called the Saturated Adiabatic lapse Rate, or SAR (also called the MAR, or moist adiabatic lapse rate) Again, the rate varies, but we’ll use an average value of: 5ºC/1000m (3.3ºF/1000ft) As the air parcel continues to rise, it continues to cool, though more slowly.
    96. 96. Stability vs. Buoyancy
    97. 97. Stability vs. Buoyancy Buoyancy – The tendency of a substance to rise, especially in a fluid
    98. 98. Stability vs. Buoyancy Buoyancy – The tendency of a substance to rise, especially in a fluid  An air-filled balloon (or you!) in water
    99. 99. Stability vs. Buoyancy Buoyancy – The tendency of a substance to rise, especially in a fluid  An air-filled balloon (or you!) in water  A helium balloon in air – Density is the key Equilibrium level
    100. 100. Stability vs. Buoyancy Buoyancy – The tendency of a substance to rise, especially in a fluid  An air-filled balloon (or you!) in water  A helium balloon in air – Density is the key Equilibrium level – Where both the rising and the still air are the same density The opposite of buoyancy is stability
    101. 101. Stability vs. Buoyancy Buoyancy – The tendency of a substance to rise, especially in a fluid  An air-filled balloon (or you!) in water  A helium balloon in air – Density is the key Equilibrium level – Where both the rising and the still air are the same density The opposite of buoyancy is stability – The substance does NOT want to rise
    102. 102. Stable air
    103. 103. Unstable air
    104. 104. Conditionally unstable air
    105. 105. Four Causes of Uplift: 1. Convective Uplift
    106. 106. 2. Frontal lifting
    107. 107. 3. Convergent lifting
    108. 108. 4. Orographic Lifting
    109. 109. 4. Orographic LiftingWaaaait…something else is going on here…the air is sinking on the other side!
    110. 110. So what happens to temperature if the airsinks on the other side of the mountain?
    111. 111. So what happens to temperature if the airsinks on the other side of the mountain? You can not have greater than 100% relative humidity on the way up (except in rare cases like a lack of condensation nuclei).
    112. 112. So what happens to temperature if the airsinks on the other side of the mountain? You can not have greater than 100% relative humidity on the way up (except in rare cases like a lack of condensation nuclei). Anything over 100% will condense into liquid water droplets, forming a cloud. Right?
    113. 113. So what happens to temperature if the airsinks on the other side of the mountain? You can not have greater than 100% relative humidity on the way up (except in rare cases like a lack of condensation nuclei). Anything over 100% will condense into liquid water droplets, forming a cloud. Right? So, as air sinks, it is compressed by the weight of more air above it and it begins to warm up adiabatically. It moves away from 100% RH (99%, 98%, 97%...and so on).
    114. 114. So what happens to temperature if the airsinks on the other side of the mountain? You can not have greater than 100% relative humidity on the way up (except in rare cases like a lack of condensation nuclei). Anything over 100% will condense into liquid water droplets, forming a cloud. Right? So, as air sinks, it is compressed by the weight of more air above it and it begins to warm up adiabatically. It moves away from 100% RH (99%, 98%, 97%...and so on). Because RH becomes < 100% as soon as the air begins to sink, we can’t use the Saturated Adiabatic Lapse Rate any more. (It is only used when RH = 100%.)
    115. 115. So what happens to temperature if the airsinks on the other side of the mountain? You can not have greater than 100% relative humidity on the way up (except in rare cases like a lack of condensation nuclei). Anything over 100% will condense into liquid water droplets, forming a cloud. Right? So, as air sinks, it is compressed by the weight of more air above it and it begins to warm up adiabatically. It moves away from 100% RH (99%, 98%, 97%...and so on). Because RH becomes < 100% as soon as the air begins to sink, we can’t use the Saturated Adiabatic Lapse Rate any more. (It is only used when RH = 100%.) It therefore warms as it sinks at the Dry Adiabatic Lapse Rate, the whole way back down.
    116. 116. This is why the back side of a mountain ishotter and drier than the side facing the wind windward side leeward side
    117. 117. Condensation nuclei and cloud droplets
    118. 118. Classifying Clouds
    119. 119. Classifying CloudsAre you paying attention?
    120. 120. Extra Credit Section!!!
    121. 121. Cloud types…
    122. 122. Fog: A cloud on the ground
    123. 123. The Four Common Types of Fog
    124. 124. Dew: Condensation on Earth’s surface
    125. 125. Formation of Precipitation: The Bergeron Process
    126. 126. The Collision-coalescence process
    127. 127. Some Different Forms of Precipitation• Rain – Drizzle vs. showers• Snow• Sleet• Glaze (ice storm)• Hail
    128. 128. The Formation of Hail
    129. 129. The Formation of Hail
    130. 130. Hail
    131. 131. Hail
    132. 132. Hail
    133. 133. Hail
    134. 134. Hail
    135. 135. Global Precipitation
    136. 136. Global Precipitation:The ITCZ Connection
    137. 137. Precipitation in the U.S.
    138. 138. Acidity
    139. 139. Acid Precipitation in the U.S.

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