What is rain shadow

As air hikes up the mountain slope, it expands and cools adiabatically. As a general rule, dry air typically cools by 5. An adiabatic process is one where heating or cooling occurs without heat being actively added or removed. For example, when air expands or compresses its molecules occupy more less space and move more slowly energetically within that space, thereby causing a decrease increase in temperature.

If a mountain's elevation is high enough, the air cools to its dew point temperature , at which point it reaches saturation, or holds as much water vapor as it can. If the air is lifted beyond this point, its water vapor will begin condensing, forming cloud droplets and eventually precipitation. The now-moist air also continues cooling, but at a rate of 3. When air is lifted in this style, that is, over a topographic barrier, it's called orographic lift.

If the air that reaches the mountaintop is cooler than the surrounding air already in place at the summit, it'll want to sink down the leeward, or sheltered side, of the mountain. As it descends, it compresses and heats adiabatically.

By now, there's little moisture remaining in the air, so very little precipitation falls on the east side of the mountain's crest. By the time the air reaches the base of the mountain, it can be many degrees warmer than it was originally. It can also move more swiftly, too, since gravity pulls on the air mass as it travels thousands of feet downhill. According to AccuWeather, a to mph wind along a mountain ridge can increase to mph by the time it reaches the mountain valleys.

This phenomenon is known as a chinook, or a foehn wind. Besides, the rain shadow effect is very important for agricultural and commercial reasons, mainly because it differentiates arid regions from moist ones. Additionally, the rain shadow effect swipes away certain minerals that come into the atmosphere and land in other types of vegetation, such as oceanic phytoplankton, which needs the elements to grow.

Finally, the effect of rain shadow is vital in affecting the water supply of certain areas of the world , such as the Atacama Desert.

On some occasions, mountains stand in the way for air to pass through. When that happens, it is usually the result of warm moist air rising along with the winds on top of the mountains. Rain shadows occur when the wind carries the moisture of the air into the mountains.

Once the warm mass of air is pushed upwards, it passes the mountain and cools down. As it hurdles on the top, it sucks moisture and goes down, leaving a dry region devoid of any precipitation. Consequently, precipitation can fall on the side where the air is coming from, but not on the other part. There are many rain shadow regions all across the globe. One of the most famous ones is in Asia, where the Himalaya mountain casts a shadow effect over the Desert of Gobi, Central Asia, and the Tibetan Plateau.

The United States of America and Canada also have rain shadows. The latter, on the other hand, hosts the natural phenomenon on the most populated city of its North-Western territory — Yellowknife is in the shadow of Ranges to the West. For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher.

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View Full Term. By clicking sign up, you agree to receive emails from Safeopedia and agree to our Terms of Use and Privacy Policy. A rain shadow describes the dry area on one side of a mountain or mountain range where less rain falls. This side of the mountain or mountain range is called the leeward side, while the side which has greater rainfall is called the windward side. A rain shadow is the result of the direction of wind and its effect on rainfall.

A rain shadow results as wind carries air full of moisture into mountains. This air is blocked by the mountains and cannot reach the other side. Precipitation or rain fall then falls on the side where wind is blowing from, but the area on the other side of the mountain is drier. This is a rain shadow.