Climate Due to Topography
Name____________________Per.__
The surface of the land, or topography, can influence climate. For example, inland areas
experience more extremes of, both higher and lower, temperatures (daily and seasonally) than
coastal areas. Mountains can change air as it moves through an area or region. Some general
observations follow. (Also, be sure to look at the pictures on the back.)
Elevation or Altitude. The elevation, or height, of land above sea level can affect or change
average temperatures. Temperature generally goes down as you go up in elevation. So for every
100 meter increase (or, about 300 feet) in elevation, the average temperature decreases 0.7
o
C (or, 3 oF). Even at the equator, tall mountain peaks can have snow on them!
Rain Shadow. The wind moves air over a mountain range and makes a rain shadow. A rain
shadow occurs when water is squeezed from the air as it moves up one side of a mountain,
making it dry on the other side of the mountain. As air flows over tall mountains the air rises,
cools, and water vapor becomes liquid water- rain, sleet, hail or snow. When this air flows down
the other side of the mountains it is cool and dry. Cool, dry air will sink down the other side of
the mountain, and will warm quickly. One type of warm, dry wind forms this way in the Rocky
Mountains, and is called a Chinook. This happens in San Diego, too. The wet air from the Pacific
Ocean sea-breeze goes over the Laguna Mountains and will eventually become dry, warm air in
the Borrego Desert.
Valley and Mountain Breezes. During daylight hours the slopes of a mountain and the air
nearby get more heat than air over the valley floor. Because the warmer air along the slopes
is less dense it rises up along the slope pulling in air from the valley with it, this forms a
valley breeze. During the nighttime the reverse effect occurs, generating mountain breezes –
air over the valley floor is warmer than air along the slopes of a mountain. Because the warmer
air over the valley floor is less dense, it rises up, which allows cool breezes to flow down the
mountain slopes.
Use the reading and the pictures on the back to answer the following questions.
1. What is the effect of elevation to climate?
2. What happens to the clouds as they pass over mountains?
3. Why do you think warmer slopes during the daylight hours help cause wind to form?
4. Why do you think the winds reverse or change their direction during the nighttime?