![Page 1: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/1.jpg)
Part 3. Distribution and Movement of Air
Chapter 9
Air Masses and Fronts
![Page 2: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/2.jpg)
IntroductionAir masses are large volumes of air that contain uniform temperature and humidity characteristics
Different air masses have different source regions
Air mass properties can modify as the air mass travel over continents and oceans
Air mass properties will modify as the air mass moves north or south
Fronts are the boundaries between air masses
![Page 3: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/3.jpg)
North American air masses and source regions
![Page 4: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/4.jpg)
![Page 5: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/5.jpg)
Continental Polar (cP) and Continental Arctic (cA) Air Masses • Canada and Asia origin for North America• Cold and dry• Inherently stable
Continental Polar AirArctic Air
![Page 6: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/6.jpg)
cP Air Migration and Modification
![Page 7: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/7.jpg)
Maritime Polar (mP) Air Masses• Upper latitude ocean origin
• Cool and moist
Continental Tropical (cT) Air Masses• Desert southwest of U.S. and northern Mexico origin
• Hot and very dry
• Inherently unstable
![Page 8: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/8.jpg)
Maritime Tropical (mT) Air Masses• Low latitude ocean origin (Gulf of Mexico)• Warm and moist• Inherently unstable
![Page 9: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/9.jpg)
Weather map symbols that show the four types of fronts between air masses
![Page 10: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/10.jpg)
• Cold fronts– Cold air displaces warm air– Steep uplift of the warm air causes
cumulonimbus clouds and precipitation
Frontal development
![Page 11: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/11.jpg)
Vertical lifting of warm along a cold front
![Page 12: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/12.jpg)
A cold front depicted on a satellite picture (a) andradar composite (b)
![Page 13: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/13.jpg)
• Warm fronts– Warm air overruns and displaces colder
air– Lifting along a warm front usually
produces stratus clouds and often light precipitation
• Stationary fronts– Neither air mass on either side of the
front can make the front move very much– The warmer air can move aloft over the
colder air at a stationary front
![Page 14: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/14.jpg)
Profile of a warm front
![Page 15: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/15.jpg)
• Occluded fronts form when a cold front overtakes a warm front. The front at the surface divides two cold air masses, while the warm air is aloft over the front.
– Cold-type occlusion has a colder air mass pushing out a cooler air mass
– Common in the eastern half of North America
– Warm-type occlusion has a cooler air mass pushing out a colder air mass
– Common along the western edge of North America
![Page 16: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/16.jpg)
Occlusion sequence (next three slides)
![Page 17: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/17.jpg)
![Page 18: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/18.jpg)
![Page 19: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/19.jpg)
Some occlusions form when the surface low elongates and moves away from the junction of the cold and warm fronts
![Page 20: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/20.jpg)
Some occlusions form when the intersectionof the cold and warm fronts slides alongthe warm front
![Page 21: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/21.jpg)
• Drylines are fronts with little temperature change but a strong humidity contrast
– Often form when cT air moves into mT air
Continental Tropical Air
Maritime Tropical Air
![Page 22: Part 3. Distribution and Movement of Air Chapter 9 Air Masses and Fronts](https://reader030.vdocuments.net/reader030/viewer/2022013122/56649d775503460f94a5a09a/html5/thumbnails/22.jpg)