GEOG 100 Lecture 08--Airmasses and Storms

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  • GEOG 100 Lecture 08--Airmasses and Storms

    1. 1. Air Masses, Stormsand other scary stuff
    2. 2. What Is An Air Mass?
    3. 3. What Is An Air Mass? A large parcel of air with characteristics which distinguish it from surrounding air
    4. 4. What Is An Air Mass? A large parcel of air with characteristics which distinguish it from surrounding air 1000 mi (1600 km) across, several miles deep
    5. 5. What Is An Air Mass? A large parcel of air with characteristics which distinguish it from surrounding air 1000 mi (1600 km) across, several miles deep Conditions of temp., humidity, stability consistent horizontally at any altitude
    6. 6. What Is An Air Mass? A large parcel of air with characteristics which distinguish it from surrounding air 1000 mi (1600 km) across, several miles deep Conditions of temp., humidity, stability consistent horizontally at any altitude Moves as a coherent whole, not easily torn apart by local turbulence
    7. 7. What Is An Air Mass? A large parcel of air with characteristics which distinguish it from surrounding air 1000 mi (1600 km) across, several miles deep Conditions of temp., humidity, stability consistent horizontally at any altitude Moves as a coherent whole, not easily torn apart by local turbulence Sourceregion: Where an air mass originates
    8. 8. Source Regions
    9. 9. Source Regions Extensive, physically uniform surface area
    10. 10. Source Regions Extensive, physically uniform surface area High or low latitude
    11. 11. Source Regions Extensive, physically uniform surface area High or low latitude Not found in the midlatitudes (too much atmospheric activity)
    12. 12. Source Regions Extensive, physically uniform surface area High or low latitude Not found in the midlatitudes (too much atmospheric activity) High pressure zones are common source regions (because air sinks, stays close to the ground, where it picks up surface characteristics)
    13. 13. Lake-effect snow:cP air crossing warmer water 5
    14. 14. Lake-effect snow:cP air crossing warmer water Areas commonly affected around the Great Lakes 5
    15. 15. Lake-effect snow:cP air crossing warmer water Areas commonly affected around the Great Lakes Buffalo, NY (Dec., 2001)--Nearly seven feet of lake effect snow fell in 5 days 5
    16. 16. Air Mass Classification
    17. 17. Air Mass Classification Latitude A = arctic/antarctic P = polar T = tropical E = equatorial
    18. 18. Air Mass Classification Latitude A = arctic/antarctic P = polar T = tropical E = equatorial Surface Conditions m = maritime c = continental
    19. 19. Major Air Mass Source Regions
    20. 20. Major Air Mass Source Regions (c)A
    21. 21. Major Air Mass Source Regions (c)A mP
    22. 22. Major Air Mass Source Regions (c)A mP cP
    23. 23. Major Air Mass Source Regions (c)A mP cP mT
    24. 24. Major Air Mass Source Regions (c)A mP cP mT cT
    25. 25. Major Air Mass Source Regions (c)A mP cP mT cT (m)E
    26. 26. Air Masses of North America
    27. 27. So what happens when these air masses meet???
    28. 28. So what happens when these air masses meet??? They start frontin’.
    29. 29. Frontal lifting
    30. 30. Movement of a Warm Front
    31. 31. Warm Front: Development
    32. 32. Movement of a Cold Front
    33. 33. Cold Front: Development
    34. 34. Comparison: Note the shapeof the frontal boundary
    35. 35. Stationary Front
    36. 36. Occluded Front
    37. 37. Fronts on a Weather Map
    38. 38. Putting it together:Note line A – A’
    39. 39. A cross section along line A – A’ (fromthe map on the previous slide)
    40. 40. Real-World Application:An Atlantic Storm
    41. 41. Life-cycle of a Midlatitude Cyclone
    42. 42. A Hypothetical Weather Map(note the alternating Highs and Lows…)
    43. 43. How do theUpper-level Winds Move?
    44. 44. Major Midlatitude Disturbances Midlatitudes are the most dynamic weather region Where polar and tropical air masses meet and mix Midlatitude cyclones (a.k.a. depressions, lows, wave cyclones) Large low pressure systems (1000+ miles across) moving from west to east in the region of the Westerlies (35º to 70º N and S latitude)
    45. 45. Characteristic weather changes withthe passage of a cold front:
    46. 46. Characteristic weather changes withthe passage of a cold front: Sharp temp. drop as the front approaches
    47. 47. Characteristic weather changes withthe passage of a cold front: Sharp temp. drop as the front approaches As the front approaches, wind direction is southerly
    48. 48. Characteristic weather changes withthe passage of a cold front: Sharp temp. drop as the front approaches As the front approaches, wind direction is southerly After the front passes, wind shifts to more northerly (opposite for the Southern Hemisphere)
    49. 49. Characteristic weather changes withthe passage of a cold front: Sharp temp. drop as the front approaches As the front approaches, wind direction is southerly After the front passes, wind shifts to more northerly (opposite for the Southern Hemisphere) Air pressure drops as the front approaches, rises after it passes
    50. 50. Characteristic weather changes withthe passage of a cold front: Sharp temp. drop as the front approaches As the front approaches, wind direction is southerly After the front passes, wind shifts to more northerly (opposite for the Southern Hemisphere) Air pressure drops as the front approaches, rises after it passes Clear skies, followed by clouds and precip. along the edge of the front, then colder with clear skies again as the front passes
    51. 51. Mapping it out:
    52. 52. Midlatitude Anticyclones High pressure systems moving west to east No fronts Subsidence Clear, dry weather Cold in winter May stagnate, stalling other weather systems behind them
    53. 53. Now on to the fun stuff!
    54. 54. Lightning
    55. 55. Lightning
    56. 56. Lightning
    57. 57. Thunder
    58. 58. Tornadoes
    59. 59. Tornado formation
    60. 60. 35
    61. 61. 36
    62. 62. Tropical Disturbances Tropical Depression - winds up to 38 mph Tropical Storm - winds 39 - 73 mph Hurricane - winds 74+ mph
    63. 63. HurricanesFour different namesfor the same event: Hurricane Typhoon Cyclones, tropical cyclones Baguios
    64. 64. HurricanesFour different namesfor the same event: Hurricane Typhoon Cyclones, tropical cyclones Baguios
    65. 65. Hurricane Origins
    66. 66. Hurricane Origins Form in tropical and subtropical zones approx. 8° to 15° N or S latitude
    67. 67. Hurricane Origins Form in tropical and subtropical zones approx. 8° to 15° N or S latitude Rarely form within 3° N or S of equator (no Coriolis force), rarely cross it
    68. 68. Hurricane Origins Form in tropical and subtropical zones approx. 8° to 15° N or S latitude Rarely form within 3° N or S of equator (no Coriolis force), rarely cross it Tend to form in or just poleward of the ITCZ
    69. 69. Hurricane Origins Form in tropical and subtropical zones approx. 8° to 15° N or S latitude Rarely form within 3° N or S of equator (no Coriolis force), rarely cross it Tend to form in or just poleward of the ITCZ Tend to form in late summer and fall (warmest sea sfc. temps.)
    70. 70. Hurricane Origins Form in tropical and subtropical zones approx. 8° to 15° N or S latitude Rarely form within 3° N or S of equator (no Coriolis force), rarely cross it Tend to form in or just poleward of the ITCZ Tend to form in late summer and fall (warmest sea sfc. temps.) Storm’s low pressure cell feeds off warm sea sfc. temps. (up to 81°F!)
    71. 71. Hurricane Origins Form in tropical and subtropical zones approx. 8° to 15° N or S latitude Rarely form within 3° N or S of equator (no Coriolis force), rarely cross it Tend to form in or just poleward of the ITCZ Tend to form in late summer and fall (warmest sea sfc. temps.) Storm’s low pressure cell feeds off warm sea sfc. temps. (up to 81°F!) Gains energy from release of latent heat of condensation during intense precipitation
    72. 72. Hurricane Origins Form in tropical and subtropical zones approx. 8° to 15° N or S latitude Rarely form within 3° N or S of equator (no Coriolis force), rarely cross it Tend to form in or just poleward of the ITCZ Tend to form in late summer and fall (warmest sea sfc. temps.) Storm’s low pressure cell feeds off warm sea sfc. temps. (up to 81°F!) Gains energy from release of latent heat of condensation during intense precipitation Always form over oceans
    73. 73. Hurricane Origins Form in tropical and subtropical zones approx. 8° to 15° N or S latitude Rarely form within 3° N or S of equator (no Coriolis force), rarely cross it Tend to form in or just poleward of the ITCZ Tend to form in late summer and fall (warmest sea sfc. temps.) Storm’s low pressure cell feeds off warm sea sfc. temps. (up to 81°F!) Gains energy from release of latent heat of condensation during intense precipitation Always form over oceans Do not / rarely form in the south Atlantic or southeast Pacific because the water is too cold and air pressure too high
    74. 74. Hurricane Origins Form in tropical and subtropical zones approx. 8° to 15° N or S latitude Rarely form within 3° N or S of equator (no Coriolis force), rarely cross it Tend to form in or just poleward of the ITCZ Tend to form in late summer and fall (warmest sea sfc. temps.) Storm’s low pressure cell feeds off warm sea sfc. temps. (up to 81°F!) Gains energy from release of latent heat of condensation during intense precipitation Always form over oceans Do not / rarely form in the south Atlantic or southeast Pacific because the water is too cold and air pressure too high Storm intensity lessens as it gains latitude (into cooler waters) or moves over land
    75. 75. Hurricanes
    76. 76. Hurricane Tracking
    77. 77. Pressure Signature of a Hurricane
    78. 78. Hurricane Structure
    79. 79. Hurricane Katrina making landfall
    80. 80. Storm Surge

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