The first thing to consider about the desert is that beneath the pebbly and/or sandy surface, there is no water aquifer, which means no moisture to sustain vegetation. Vegetation (which includes trees) provides a certain amount of top soil stability and retention of warmth, after a sunny day, which accounts for the lack of top soil and extremes in temperatures.
It is not unusual for a desert to attain a high level temperature during the day, and a temperature up to 50 or 60 degrees less at night.
Middle latitude deserts are found in the interior of continents. They receive rare rains due to their distance from the ocean. During the winter months, daytime temperatures can drop to below freezing. Only plants like the cacti, which can store moisture in their roots for long periods of time will survive.
Deserts such as Taklamakan of China, the Gobi of China and Mongolia and the American desert in Arizona, New Mexico, Nevada and Southern Utah are mid-latitude deserts.
The vicious cycle of a desert region is on-going due to a lack of reciprocal humidity between earth and atmosphere. Yet, there are two deserts which are very close in proximity to oceans.
The Namib desert, which is located in Africa, is bordered for 1,200 miles by the Atlantic ocean, however, due to no water aquifer, it remains a desert. The ocean provides a cooler temperature over the desert and often times, fog.
In northern Chile, the Atacama desert runs 600 miles of the coast at the Pacific ocean. It is considered, according to National Geographic, to be the driest desert in the world. Because the desert is located “leeward” in Chile, (meaning the wind travels over the desert toward the ocean), the proximity to the water does it no good, except in cooling the temperatures. The Andes are close by and so steep in altitude, that “convective clouds” are blocked, preventing rain fall.
The role of wind, in the vicious cycle of a desert region is dehydration. Kind of like a convection oven effect, the dry wind causes a more profound drying of the habitat, ensuring a lack of moisture stored.
One of the causes of the Great Depression in the United States was the overproduction of farm lands, producing a desert like effect and terrible dust storms, which could short out a car due to static electricity and pneumonia. Many people died of the sand caused pneumonia during this time.
Underground water aquifers, which occur naturally, as well as corrective action in farming ethics helped to prevent Oklahoma, Kansas and parts of Texas from becoming a giant desert area.
Specifically, to keep a desert dry requires no underground water, dry winds and a lack of consistent rainfall which affords underground build up.
Sources:
The Atmosphere, pp. 362-367 Fifth Edition, Frederick K. Lutgens/Edward J. Tarbuck
