dicksblog.info (GT117-the_mojave_desert.shtml)

 

http://www.dicksblog.info/nittany_lion.jpg (5381 bytes)

http://www.dicksblog.info/logo.jpg (5381 bytes)

http://www.dicksblog.info/american_flag.jpg (5381 bytes)

 


 

 


Why is the Mojave Desert Hot and Dry?

 

 

The Mojave Desert is a rain-shadow desert located in the southwestern United State, primarily in southeastern California and southern Nevada. Small areas for the Mojave extend into Arizona and Utah. It occupies almost 48,000 square miles. Its boundaries are generally noted by the presence of Joshua Trees (pictured on the right), which are native only to the Mojave Desert and as such are considered the indicator species of the area, although many other species of plants are present. It is called a rain-shadow desert because it is on the leeward (down-wind or opposite) side of a mountain or mountain range. The Mojave is the hottest, driest, and smallest desert in North America.

The Mojave contains the lowest elevation in North America at Badwater Basin in Death Valley, CA at an elevation of 282 feet below mean sea level. Only about 85 miles to the west northwest is the highest elevation in the contiguous 48 states at Mount Whitney, also in California, at an elevation of 14,505 feet above sea level. In 1913, the U.S. Weather Bureau recorded the highest ambient air temperature ever recorded on the surface of the earth at Furnace Creek in Death Valley. It was 134 degrees Fahrenheit in the afternoon of July 10.

 

 

 

 

Why is the Mojave Desert hot and dry?

There are many factors and interactions that occur that determine the climatic conditions of any particular area, and the Mojave Desert is no different in that regard. However, in the case of the Mojave, the most pronounced and major factor contributing to the hot and dry conditions of the Mojave is the rain-shadow characteristic of the desert.

Its condition can be explained by the following simplified scenario. We first note that the prevailing wind direction in the southwestern United States is from the west. Winds blow inland off the Pacific Ocean over Southern California. In their movement eastward, the winds encounter several mountain ranges, some of which have elevations as high or higher than 10,000 feet, such as that of the Sierra Nevada’s which include the highest mountain in the contiguous 48 states, Mount Whitney at over 14,000 feet.

Winds coming onshore from the ocean are laden with moisture (water vapor) and are at a relatively cool temperature, let ’s say 75 degrees Fahrenheit (F) for example. As the winds travel eastward, they encounter the inland mountain ranges and rise accordingly. As they rise, they cool, causing the moisture to condense and fall as either rain in the summer or snow in the winter. Because of the condensing water vapor, the temperature of the air drops at the rate of about 2 degrees F per thousand feet of elevation as it rises. If the mountains are, let’s say, an average of 10,000 feet high, that means that the temperature of the air as it reaches the top of the mountains is now about 55 degrees F and it is dry because of the condensed water vapor deposited on the western side of the mountains.

 

 

As the air continues eastward, it travels down the eastern slope of the mountains to the lower elevation on the east side and it heats up during its decent to the lower elevation due to atmospheric compression as it descends. Since the air is now dry, it heats at a higher rate of about 5 degrees F per thousand feet of elevation, so that when the air reaches sea level on the east side of the mountains, it is now at 105 degrees F (and dry) when it reaches the Mojave Desert.

So, air that started at 75 degrees and contained moisture on the west side of the California mountains is now at 105 degrees and dry on the east side of the mountains. Thus, we have the hot and dry atmospheric conditions that produce and characterize the desert.

Even though the Mojave contains Death Valley which is below sea level and other areas that are lower (such as in the Colorado River basin), most of the Mojave is higher than 2000 feet above sea level so that the example above is an overly simplified description of the more complex patterns that occur to create the Mojave. But you get the idea.

 

 

 

 

 

 

   Close   


or click the blue title bar at the top of the page


Top of Page


http://www.dicksblog.info/logo.jpg (5381 bytes)

dicksblog.info. All rights are reserved.
Send mail to
dick@dicksblog.info
with questions or comments about this web site.
Copyright © 2025 dicksblog.info
Last modified: January 22, 2025