1. NATS 101 Lecture 22 Air Masses

2. Supplemental References for Today’s Lecture Lutgens, F. K. and E. J. Tarbuck, 2001: The Atmosphere, An Introduction to the Atmosphere, 8 th Ed. 484 pp. Prentice Hall. (ISBN 0-13-087957-6)

3. 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.

4. 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

5. Air Mass Source Regions Contrasting source regions are Continents versus Oceans Tropics versus Poles An Air Mass is designated in terms of its Source Region

6. Air Mass Characteristics Ahrens Table 8.1

7. Air Mass Source Regions for NA Ahrens Fig 8.2

8. Creation of cP Air Mass Williams p22

9. Creation of cP Air Mass Williams p23

10. Creation of mP Air Mass Lutgens & Tarbuck, p 230

11. Lake Effect Snows 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. Lutgens & Tarbuck, p 230

12. Creation of mT and cT Air Masses Williams p24

13. Contrasting Air Masses Ahrens Fig 8.9 17 Apr 1976

14. Paths of cP Air Masses Ahrens Fig 8.3

15. cP Air Mass Ahrens Fig 3 p203 24 Dec 1983

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

17. mP Air Masses Ahrens Fig 8.7Ahrens Fig 8.5 Air mass modified further as it crosses several mountain ranges of West U.S.

18. cT Air Mass Ahrens Fig 8.1029-30 Jun 1990

19. Winter mT Pacific Air Masses mT mP Ahrens Fig 8.8 “Pineapple Express”

20. Cold Air-Warm Air Movement Williams p23

21. Weather Map with Air Masses Ahrens Fig 8.11

22. 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)

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