1. Right Now: TCAP Review Get new 7.2 notes Agenda: 1. Notes: 7.2 part I 2. Complete Air Masses map 3. Describe Air Masses in graphic organizer TN Standard: Analyze meteorological data to predict weather conditions February 10, 2015

3. Today we’ll learn about air masses and their effect on weather. THINK ABOUT IT… Write down as many different qualities of air as possible…

4. An AIR MASS is a large body of air where temperature and moisture content are similar throughout. Changes in weather are caused by the movement and interaction of air masses.

5. Air Masses characterized by: moisture content temperature The moisture content and temperature are determined by the AREA over which the air mass forms. These areas are called source regions.

6. There are many types of air masses, each associated with a particular source region. The characteristics of these air masses are represented on maps by a two-letter symbol. The first letter indicates the moisture content characteristic of the air mass. The second letter represents the temperature that is characteristic of the air mass. mTmT

7. MOISTURE CONTENT maritime (m)  forms over water  Wet continental (c)  forms over land  dry Types of Air Masses

8. TEMPERATURE polar (P)  forms over the polar regions  cold tropical (T)  develops over tropics  warm

10. Cold Air Masses Most cold winter weather in the U.S. is influenced by three polar air masses. 1. (cP) continental polar – forms over northern Canada - brings extremely cold winter weather to the U.S. In summer, a cP air mass brings cool, dry weather. 2. (mP) maritime polar – forms over the North Pacific Ocean is cool and very wet. Brings rain and snow to Pacific Coast in winter and cool, foggy weather in summer. 3. (mP) maritime polar air mass that forms over the North Atlantic Ocean brings cool, cloudy weather and precipitation to New England in winter. In summer, it brings cool weather and fog.

11. Four warm air masses influence weather in the U.S. 4. (mT) Maritime tropical that develops over warm areas in Pacific Ocean is milder than maritime polar air mass that forms over Pacific Ocean. Same weather as #6 mT. 5. (mT) Maritime tropical air mass develops over the warm waters of the Gulf of Mexico and towards the Midwest. 6. (mT) Maritime tropical forms over the warm Atlantic Ocean, and moves north across the East Coast. BOTH : In summer, they bring hot and humid weather, hurricanes, and thunderstorms. In winter, mild and cloudy weather. 7. (cT) Continental tropical air mass forms over deserts of northern Mexico and southwest U.S. It moves northward and brings dry, and hot weather in summer.

12. Is humid air heavier than dry air? What do you think?

13. People often assume humid air is heavier than dry air. Humid air rises like a balloon because it is less dense than dry air at same pressure and temperature. Water molecules are lighter than nitrogen and oxygen which makeup air.

14. The more water vapor in a mass of air, the more nitrogen and oxygen is displaced. When humidity increases, air becomes less dense and rises. As an air mass rises, it cools. The water vapor condenses, and air mass eventually sinks. If water vapor were heavier than air, clouds would form only at the Earth’s surface.

15. Using your map of North America – Draw RED or BLUE colored arrows (according to temperature) and indicate the source regions of North American air masses. LABEL each air mass by its two-letter symbol. (4 warm and 3 cold air masses as shown on page 192). IN CLASS mT Look at page 192 in textbook

17. How do you think air masses that form over the land and ocean affect weather in the United States?

18. Use your graphic organizer and textbook page 193 to classify: 3 COLD AIR MASSES 4 WARM AIR MASSES

19. END OF AIR MASSES PPT

20. Meteorological data suggests that a warm front is coming. What sort of weather might be predicted? PUTTING IT TOGETHER…

21. Drizzly rain followed by clear, warm weather!