1. Chapter 20: Air Masses, Fronts, and Instruments

2. AIR MASSES Definition:
Body of air that is uniform (same) air temperature and water content
Air masses are named after their source region (the place where they were formed)
There are four major types of air masses:
Continental (c)
Maritime (m)
Polar (P)
Tropical (T)

3. Tropical (T)
forms in warm latitudes
warm air
Polar (P)
forms in cold extreme north &
southern regions
cold air
Continental (c)
forms over land
dry air
Maritime (m)
forms over oceans
moist air

4. Describe the difference between each air mass:
Continental Air Mass
Maritime Air Mass
Describe the difference between each air mass:

5. Describe the difference between each air mass:
Polar Air Mass
Tropical Air Mass
Describe the difference between each air mass:

6. What type of air mass?
mT- Maritime Tropical
Warm and Moist Air

7. What type of air mass?
cP – Continental Polar
Cold and Dry Air

8. What Type of Air Mass?
cT – Continental Tropical
Warm and Dry Air

9. What Type of Air Mass?
mP- Maritime Polar
Cold and Moist Air

10. Air Masses Around the World

11. WEATHER FRONTS Cold Warm Occluded Stationary Definition:
A front occurs when two unlike air masses collide.
Remember: Warm air rises while cold air sinks! Therefore, warm air is pushed up when a cold air mass moves into the area.
A typical front is several km long.
There are 4 basic types of fronts:
Cold Warm Occluded Stationary

12. COLD FRONT
A cold air mass takes over a warm air mass
Symbol:

13. Cold Front Diagram
Weather Conditions: Cold fronts can move fast producing thunderstorms, heavy rain, or snow. Cooler weather follows.

14. Cold Front

16. What type of clouds are formed during a cold front?

17. WARM FRONT Occurs when warm air mass takes over a cooler air mass
Symbol:

18. Warm Front Diagram
Weather Conditions: Precipitation over large area, usually drizzle or rain.

19. Warm Front

20. What type of clouds would you see before the rain comes?

22. STATIONARY
Two air masses meet and neither moves.
Symbol:

23. Stationary Front
Weather Conditions: Stationary fronts move little and rain continues over long period of time.

24. OCCLUDED FRONT
Occurs when a fast moving cold front overtakes a warm front lifting the warm air off the ground.
Symbol:

25. Occluded Front Diagram
Weather conditions: Cool temperatures and large amounts of precipitations

26. Occluded Front

27. Weather Front Symbols

28. WEATHER INSTRUMENTS REVIEW… Anemometer measures wind speed Wind Vane
measures wind direction
Barometer
measures air pressure
Psychrometer
measures relative humidity

29. Barometer
Anemometer
Wind Vane

31. Where are the High and Low Pressure Systems?

32. WEATHER MAPS
Meteorologists prepare weather maps using coded weather information they have received from numerous weather stations.

35. Symbols are plotted around every weather station.
The cluster of symbols at each station is called a station model.

36. INTERPRETING MAPS
After all station models are plotted, meteorologists create individual maps to observe individual weather characteristics.
Lines are drawn between stations with equal values of temperature, pressure, or precipitation.

37. Areas of equal pressure are called isobars

38. Areas of equal temperature are called isotherms
Areas of similar precipitation are shaded different colors or patterns to indicate the precipitation type