1. Ground School: Meteorology
5.08 Air Masses
References: - FTGU, pages 139 and Air Command Weather Manual, Chapters 6 and 19
40 Minutes

2. Ground School 5.08 Meteorology – Review
1. What creates wind?
The horizontal pressure differences.
2. What do isobars on a map represent?
Lines of equal pressure.
3. The ______________ the isobars are on a map, the stronger the winds.
Closer together
4. As you go up in altitude, what happens to the winds?
Veer and increase
5. When does a land breeze occur?
During the night

3. Ground School 5.08 Meteorology – Air Masses
MTPs:
Air Masses – Definition and Characteristics
Formation
Classifications
Modification
Geographic factors
Seasonal Effects

4. Ground School 5.08 Meteorology – Air Masses
Definition:
A large section of the troposphere with uniform properties of temperature and moisture
May be several thousand miles across
Cold Air Masses
Warm Air Mass
Instability
Stability
Turbulence
Smooth air
Good visibility
Poor visibility
Cumuliform clouds
Stratiform Clouds and Fog
Shower type precipitation
Drizzle type Precipitation
Hail, Thunderstorms may occur

5. Ground School 5.08 Meteorology – Air mass formation
Air masses develop uniform properties of temperature and moisture
Source Regions:
Formed over the ice and snow surfaces of the Arctic would be cold and dry
Formed over the South Pacific would be warm and moist
Air masses develop uniform properties of temperature and moisture when a large part of the troposphere comes under the influence of a large part of the earth’s surface for a long period of time
These areas are called Source Regions
An air mass formed over the ice and snow surfaces of the Arctic would be cold and dry
An air mass formed over the South Pacific would be warm and moist.

6. Ground School 5.08 Meteorology – Air mass formation
Three main sources over North America
Arctic (A)
Cold
Extends from the North Pole south to the permafrost line
Polar (P)
Cool
Extends south from the permafrost line to where the temperature is 10°C
Tropical (T)
Very warm
Lies below Latitude 30°N.

7. Ground School 5.08 Meteorology – Air mass formation
Two Sub-Categories:
Continental (c) - Dry
Maritime (m) - Moist

8. Ground School 5.08 Meteorology – Air mass classifications
Continental Arctic (cA):
Forms over poles (usually in winter)
From polar regions across prairies, into east
Low moisture, Very cold, Very stable
Very low tropopause.
Pacific
Ocean
Atlantic
Gulf of
Mexico

9. Ground School 5.08 Meteorology – Air mass classifications
Maritime Arctic (mA):
Forms over Alaska or Siberia
Spends short time over North Pacific Ocean
Moist, Cold, Unstable in low levels
Low tropopause.
Pacific
Ocean
Atlantic
Gulf of
Mexico

10. Ground School 5.08 Meteorology – Air mass classifications
Maritime Polar (mP):
Forms over Arctic, Alaska and Northern Russia
Spends longer time over Pacific Ocean than mA
Moist, Warmer than mA, More stable than mA
Medium height tropopause.
Pacific
Ocean
Atlantic
Gulf of
Mexico

11. Ground School 5.08 Meteorology – Air mass classifications
Maritime Tropical (mT):
Forms over oceans and bodies of water in the Tropics
Rarely appears north of Great Lakes
Causes fog that effects Atlantic provinces
Moist, Very warm, Unstable
High tropopause.
Pacific
Ocean
Atlantic
Arctic

12. Ground School 5.08 Meteorology – Air mass modification
As air masses move from their source region, they become modified
Degree of modification depends on three factors:
Speed at which the air mass moves
Make up of the surface (i.e. land or water)
3. Temperature difference between air mass and new region’s surface temperature.

13. Ground School 5.08 Meteorology – Air mass modification

14. Ground School 5.08 Meteorology – Geographic factors
The temperature of the oceans is a major factor
North Pacific Current supplies warm water along the West Coast of Canada
This warm water current maintains the Gulf of Alaska ice free through the winter

15. Ground School 5.08 Meteorology – Geographic factors
Mountains
On land the Rocky Mountains and the Coastal Range barrier extends unbroken from Alaska to Mexico with peaks extending up to 10, ,000 feet

16. Ground School 5.08 Meteorology – Geographic factors
Lakes
Northern Canada is covered with lakes that are open and provide moisture to the air in summer, but are frozen in winter.

17. Ground School 5.08 Meteorology – Seasonal effects

18. Ground School 5.08 Meteorology – Confirmation
What are the characteristics of a Cold Air Mass?
Instability, Turbulence, Good visibility, Cumuliform clouds
Shower type precipitation (Hail and thunderstorms may occur)
What are the three main source regions for North America?
Arctic (Cold), Polar (Cool), Tropical (Warm)
What are the two air mass sub-categories?
Maritime and continental
Name some factors that affect air masses