Study Guide Chapter 7 1.  Define the following air mass symbols: mE, MT, cT, mP, cP, and cA. 2.    What are the 5 air masses that influence the weather of North America. Describe characteristics of each air mass. Know where each originates. 3. What is a front? 4. Draw the symbol for different fronts. 5. What is a stationary front and occluded front? 6. Describe the characteristics of cyclone and anticyclone. 7.  What are thunderstorms? 8.  What are tornadoes? Where is tornado alley? 9.   Describe a hurricane. Where do hurricanes form?  

Air Masses and Atmospheric Disturbances An air mass is a large body of air homogeneous in temperature and humidity. A source region refers to where the air mass is located geographically.

Source Regions E= Equatorial ( very warm) T= Tropical (warm) P=Polar (cold) A=Artic (very cold) c= Continental (dry) m=Maritime (wet)

Source Regions Combined to make various classifications mE mT cT mP cP

Fig. 7-1, p. 178 5

Air Masses cP continental polar Source region is Canada. Weather associated with this air mass is cold, crisp, and clear weather. Rarely travels Western U.S. cA continental artic Originates Artic Ocean it is extremely cold, dry, and stable air. Rarely reaches the U.S.

Air Masses mP maritime polar Source region is Northern Pacific Ocean It is cold air, damp, and unstable. When this air meets other cold air it usually results in cloudy weather with precipitation. This is the source of many MidWestern snowstorms.

Air Masses mT Maritime Tropical Source region Gulf of Mexico subtropical region of Atlantic Ocean (Caribbean) When this air mass reaches cP air results in significant precipitation. Responsible for thunderstorm activity. cT continental Tropical Hot, dry, and clear skies. Sahara of North America. Where? Least important of air masses.

Cold Front and Warm Fronts To view this animation, click “View” and then “Slide Show” on the top navigation bar. 9

Weather symbols Occluded= merger of fronts Fig. 7-4, p. 181 10

Convergent or Cyclonic Low pressure Air in the center is displaced upward Diameter is approximately 600 miles Counterclock wise movement

Divergent or anticyclonic High pressure air in center is subsiding Usually associated with fair weather Diameter about 900 miles Clockwise movement Cyclones and anticyclones tend to develop in certain areas more frequently. These are known as storm tracks.

Thunderstorms Thunderstorms are uplift of moist air. Charges cause by friction of air moving over ice particles.

Thunderstorms When the lightning discharge occurs the air is heated to 45,0000 F. The air expands explosively as thunder.

Tornadoes Intense cyclonic/ low pressure storm Tornado alley Oklahoma and Kansas. Natural funnel

Hurricanes Diameters are 100-400 miles Severe tropical cyclones that develop over warm oceans

Table 7-3, p. 197 17

Latent Heat of Condensation Fig. 4-11, p. 96 18

Fig. 7-18, p. 195 19

Weather symbols