Page 250 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

214 part II The Water, Weather, and Climate Systems
Egg Island, British Columbia 100 Mile House, British Columbia
400
300
200
100
0 JFMAMJJASOND Month
20 400 10 300 0 200 –10 100 –20 0
20
10
0
–10
JFMAMJJASOND –20 Month
Metres
4000
2000 W 0
Egg Island
E
Mt. Calgary Fidelity International
Airport
100 Mile House
Calgary International Airport, Alberta
400 20
300 10
200 0
100 –10
0 JFMAMJJASOND –20 Month
Glacier National Park, Mount Fidelity, British Columbia
▲Figure 8.7 Orographic patterns in British Columbia and Alberta. Four stations in British Columbia and Alberta provide examples of oro- graphic effects of windward precipitation and leeward rain shadows. Isohyets (lines connecting points of equal precipitation) that form the boundaries between the colours on the map indicate precipitation (in mm). [Data courtesy of Meteorological Service of Canada, and map by Jessica Mueller and Pam Schaus.]
air pressure rises in response to the cooler, denser air; cloud cover breaks and clears.
On weather maps, such as the example in Critical Thinking 8.1, page 222, a cold front is depicted as a line with triangular spikes that point in the direction of fron- tal movement along an advancing air mass. The particu- lar shape and size of the North American landmass and its latitudinal position present conditions where cP and
400
300
200
100
0
JFMAMJJASOND Month
20
10
0
–10
–20
mT air masses are best developed and have the most di- rect access to each other. The resulting contrast can lead to dramatic weather, particularly in late spring, with siz- able temperature differences from one side of a cold front to the other.
A fast-advancing cold front can cause violent lift- ing, creating a zone known as a squall line right along or slightly ahead of the front. (A squall is a sudden episode of
Coast Mountains Mt. Waddington
Interior Plain Rocky Mountains Prairies
Precipitation (mm)
Temperature (°C)
Precipitation (mm)
Temperature (°C)
Precipitation (mm)
Temperature (°C)
Precipitation (mm)
Temperature (°C)