Chapter 8 cover

air masses An air mass is a large body of air that has similar temperature and moisture properties throughout. The best source regions for air masses are large flat areas where air can be stagnant long enough to take on the characteristics of the surface below.

Figure 8.1

temperatureP-PolarA-ArcticT-Tropical humiditym-Maritime-wetc-Continental-dry classifying air masses

air masses

North American air masses

cP Continental Polar Air Masses cold temperatures and little moisture

cP a map of surface observations and the leading edge of a large arctic air mass blanketing much of the United States has been highlighted by the blue line. The center of this air mass is a high pressure center located in northern Montana (indicated by the blue "H") Continental Polar Air

mT Maritime Tropical Air Masses warm temperatures and rich in moisture

mT Maritime Tropical Air a map of surface observations and the leading edge of a tropical air mass surging northward into the Ohio Valley has been highlighted in red. Southerly winds behind the boundary signify the continued northward transport of warm moist air

k-coldw-warm air mass modification

cP-w

fronts

cold front

Figure 8.2

Figure 8.3

fronts

warm front

Figure 8.4

fronts

occluded fronts

mid-latitude cyclone

formation of an occlusion

mature cyclone

partial occlusion

occlusion

life of a midlatitiude cyclone

Figure 8.8

Figure 8.9

Figure 8A

Figure 8.10

Figure 8.7