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Lecture14 oct28-bb
- 1. Lecture 14 AirMass Fronts 1
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- 3. Weather map 11/02/2009 Weatherstrongly depends on where an air mass comes from!!!
- 4. What is anair mass? An air mass is a large body of air with similar temperature and humidity An air mass is named by its birthplace (source region) 4
- 5. Must be dominatedby light wind (or non at all) Must have an extensive, uniform surface 5
- 6. air mass name Bytwo letters with two properties
- 7. air mass name Bytwo letters with two properties cA cP cT mP mT
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- 10. Why cold cPpassage causes clear weather?
- 11. The upper airflow on the map below would bring ____ air masses into the Pacific Northwest and ____ air masses into the eastern United States. a. b. c. d. mT, mP mP, cP mT, cP mP, cT 11
- 12. Air masses ofNorth America mP/west coast 12
- 13. What would happenas cP passes over great lakes? 13
- 14. Lake-effect snow is producedin the winter when cold, arctic winds move across long warmer lake water, and is deposited on the lee shores. Figure 1, p. 207
- 15. What would happenas two air masses meet? 15
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- 17. Atmospheric Fronts Boundary, transitionzone between two different air masses frontal boundary can be 1-100 km wide cP 17
- 18. Cold Fronts Cold airreplaces warm Much steeper than warm fronts Advances faster than warm front More violent weather –cumulonimbus clouds Short, sharp showers mT cP 18
- 19. Weather associated withcold front passing Weather Before Passing While Passing After Passing Winds south-southwest gusty; shifting west-northwest Temp. warm sudden drop steadily dropping Dew Point high; remains steady sharp drop lowering Pressure falling steadily minimum, then sharp rise rising steadily Precip. short period of showers heavy rains, sometimes with hail, thunder and lightning showers then clearing
- 20. Warm Fronts Warm airreplaces cold Gentle slope Covers a wide area with its weather Stratus clouds get lower as front approaches Drizzle or steady rain cP mT 20
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- 22. Weather associated withwarm front passing Winds Temperature Dew Point Precipitation Before Passing south-southeast cool-cold, slow warming While Passing variable steady rise steady rise After Passing south-southwest warmer, then steady steady light-to-moderate rain, snow, sleet, or drizzle rise, then steady drizzle or none usually none, sometimes light rain or showers Why?
- 23. Warm Fronts Warm airreplaces cold Gentle slope Covers a wide area with its weather Stratus clouds get lower as front approaches Drizzle or steady rain cP mT 23
- 24. Stationary Fronts nomoving weather: clear, partly cloudy, cloudy, light precipitation 24
- 25. Occluded Fronts separatetwo cold air masses Lifts the warm air off the ground Weather is complex Cold occluded front– cold front lifted warm front Warm occluded front- cold front rises up and over warm front 25
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- 28. Atmospheric Fronts Boundary, transitionzone between two different air masses frontal boundary can be 1-100 km wide cP 28
- 29. The diagram belowrepresents a side view of a ____ occluded front with the coldest air located at position ____. a. b. c. d. cold type, B warm type, B cold type, A warm type, A 29
- 30. Review Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. What isan air mass? What and where are good source regions for air masses? How are air masses classified? What are the characteristics of the air masses that commonly affect weather over the U.S.? How can air masses be modified? What are the fundamental, physical processes involved with generating lake effect snows? What is a front? What are the types of fronts? How are they analyzed (what symbol) on a surface weather map? What are the characteristics of each kind of front? What is observed during frontal passage for each kind of front? Why is the weather at LA much drier than at Atlanta? What are the two jet streams and how are they created? What is the Walker circulation? What is El Nino? How often does it occur? How do pressure, precipitation, SSTs and ocean currents change in the equatorial pacific during an El Nino event? 30