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NATS 101 Lecture 22 Air Masses

NATS 101 Lecture 22 Air Masses. What is an Air Mass?. Air Mass Large area (>1600 km by 1600 km) of air that contains relatively uniform, horizontal distributions of temperature and moisture. How Air Masses Form.

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NATS 101 Lecture 22 Air Masses

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  1. NATS 101Lecture 22Air Masses

  2. What is an Air Mass? • Air Mass Large area (>1600 km by 1600 km) of air that contains relatively uniform, horizontal distributions of temperature and moisture.

  3. How Air Masses Form • If surface air resides in a region for a few days, it acquires the thermal and moisture characteristics of the underlying surface. • Source regions for Air Masses are: Big in area [ >>(1600 km)2 ] Dominated by persistent high pressure and light winds

  4. Air Mass Source Regions • Contrasting source regions are Continents versus Oceans Tropics versus Poles • An Air Mass is designated in terms of itsSource Region • Each Air Mass has its characteristic weather

  5. Air Mass Characteristics Ahrens Table 8.1

  6. Air Mass Source Regions for NA Ahrens Fig 8.2

  7. Creation of cP Air Mass Williams p22

  8. Creation of cP Air Mass Williams p23 Snow cover accelerates the formation of cP air masses through enhanced radiative cooling.

  9. Creation of mP Air Mass Lutgens & Tarbuck, p 230 Transition of cP to mP occurs rapidly as cP air mass streams over warm water.

  10. Lake Effect Snows ~100 km Lutgens & Tarbuck, p 230 As cP air flows over the warmer, open Great Lakes, it is warmed and moistened. When the modified cP air flows onshore, prodigious snows of several feet can result.

  11. Creation of mT Air Masses Williams p24

  12. Creation of cT Air Masses Williams p24

  13. Contrasting Air Masses 17 Apr 1976 Ahrens Fig 8.9

  14. Paths of cP Air Masses Ahrens Fig 8.3 Two record breaking cP air masses

  15. cP Air Mass Ahrens Fig 3 p203 24 Dec 1983 Another record breaking cP air mass

  16. Modification of cP Air Mass cP cP warm ocean mP warm ocean mP Ahrens Fig 8.4

  17. mP Air Masses East Coast Snows Storms Air mass modified further as it crosses several mountain ranges of West U.S. Winter rains over West Coast Ahrens Fig 8.5 Ahrens Fig 8.7

  18. cT Air Mass Record Heat over Western U.S. 29-30 Jun 1990 Ahrens Fig 8.10

  19. Winter mT Pacific Air Masses mP mT “Pineapple Express” Ahrens Fig 8.8 Heavy precipitation along West Coast

  20. Weather Map with Air Masses Ahrens Fig 8.11 Fronts form between adjacent air masses!

  21. Summary • Air Masses Large (>1000 miles) regions with “uniform” temperature and moisture characteristics • Classified by Source Region Continental (c) or Maritime (m) Polar (P) or Tropical (T) • Source Regions Big in area (>>1600 km by 1600 km) Dominated by light winds (long resident times)

  22. Assignment for Next Lecture • Topic -Fronts • Reading -Ahrens pg 212-219 • Problems -8.12, 8.13

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