Relief and Climate

In Geography, the term relief may be defined as “the variations in elevation and slope of an area of the Earth’s surface”. When we speak of an area as being flat, gently sloping or mountainous, we are speaking of the relief of that area. When we speak of the elevation (height above sea level) of an area, we are also speaking of relief.
The relief of an area can have a significant effect on the climate of that area. Let us explore the effect of relief on temperature, wind and rainfall.

Effect of Relief on Temperature

Elevation has a marked effect on the temperature of an area. Generally speaking, temperature decreases with height in the lower atmosphere. Therefore, areas at high elevations would tend to experience lower temperatures than nearby areas at much lower elevations. In the lower atmosphere, temperature decreases at a rate of about 6.5 degrees Celsius per kilometer. The rate at which temperature decreases with height is called the environmental lapse rate.

The drop in temperature is due in part to the fact that atmospheric pressure decreases with height. Because of the lower pressure at high elevations, the air is thinner (the molecules of air are farther apart). This makes the air less capable of absorbing or retaining heat. The video below explains in more detail.


Effect of Relief on Wind

Wind speed is affected by altitude. Near the Earth’s surface, winds are slowed due to friction. At higher elevations wind speeds tend to be considerably higher. The windward slopes of mountains (the side facing the prevailing wind) will generally experience higher wind speeds than nearby lowland areas. Winds speeds are not as high on the leeward side.

Effect of Relief on Rainfall

Relief can influence the amount of precipitation an area receives. When air is forced to rise over a mountain range, it cools and the moisture within it condenses. Clouds form and produce rain. This type of rainfall is called orographic rainfall or relief rainfall. It rains mostly on the windward slopes. As the air moves over the mountain range and starts to descend, it warms. As a result, rainfall is usually low on the leeward side of the mountain range and the area is said to be in a rain shadow. The video below explains the process in greater detail.

Much of the Caribbean region is under the influence of the northeast trade winds. These winds pick up moisture as they blow over the Atlantic. They are forced to rise over the mountains of many Caribbean islands, producing relief rainfall on the windward side. Rain shadows can be found on the leeward side of many Caribbean islands.

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 Related Pages

Weather and Climate

Trade Winds


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