whole year Compare that to the total amount of pre cipitation for the Albany New York area in 2002 at 40 8 inches 103 6 cm and you ll see that the desert receives a much smaller amount in one year What is the annual precipitation in your town Biologists look at rainfall when they define a desert but in addi tion they look at the evaporation rate Evaporation is when a liquid changes into a gas in this case the liq uid is the rain The evaporation rate describes the time it takes for the rain to dissipate into the air The evaporation rate must be greater than the amount of rainfall for the region to be called a desert by biolo gists Basically biologists focus on the little amount of rain deserts receive each year and the fact that most of that rain evaporates and is not beneficial to the animals and plants that live in the region What Makes Most Deserts So Hot Why are most deserts so hot Most deserts fall between the latitudes called the Tropic of Cancer and the Tropic of Capricorn If you look on a globe these latitude lines are found on either side of the equator This region is known as a subtropical climate belt Gen erally it has dry air and clear skies The winds are very dry because they have lost most of their mois ture in the more northern or southern regions These deserts are often described as hot dry deserts The winds along their western coasts are often cooled by cold ocean currents which cause them to drop only
small amount of water These areas are called coastal deserts Atacama in Chile is an example of a coastal desert Some deserts are found far inland or between mountains Often these are known as semiarid deserts Semiarid deserts are found in Utah Mon tana Russia and northern Asia The winds that reach these deserts have usually released most of their moisture before reaching the desert areas Desert regions also absorb more heat than humid regions Since there is not much to deflect the sun's rays bounce the rays off of the ground in the desert the desert absorbs 90 percent of the sun's rays or solar radiation which heats the ground and the layer of air above the ground In more humid regions of the world the sun's rays are deflected by clouds dust and water Ghost Rains In order for rain to fall there must be clouds in the sky Clouds rarely float over the desert but once in a while a cloud does float over the desert and rain falls to the hot ground below Sometimes the ground is so hot that there is a layer of hot air just above the ground This air can be so hot that it evaporates the rain as soon as the rain hits it The rain never reaches the dry earth of the desert When this occurs it is called a ghost rain Sometimes a ghost rain cools the layer of hot air enough so that if a second rainfall
occurs this rain will not evaporate and will have a better chance of falling to the ground Make a Solar Still Plants and animals that live in the desert have adapted to the lack of rain in very unique ways that we will explore further People however do not have these adaptations They have to obtain water or they will die A person can live only about three days without water when the temperature is above 100°F 37 8°C as it is in the hot and dry deserts There are only a handful of ways to obtain water in the desert You could try to collect rainwater or dew in the morning You could also get water from desert plants like cacti Another way to obtain water is to build a solar still The solar still was created by two doctors and was tested by the United States Air Force in the deserts of Arizona Here's how to make your own What You Need the A grown up to assist A Shovel Measuring tape A Glass jar such as a 32 ounce 9 liter mayon naise jar Plastic wrap At Stones
What You Do 1 Dig a hole roughly 3 feet 9 m across and about 2 feet 6 m deep 2 Place the open jar in the center of the hole with the opening on top 3 Ask someone to help you spread a large sheet of plastic wrap over the hole and jar 4 Place stones on the plastic wrap on the ground to hold it down and place one stone in the center of the plastic wrap covering the jar opening to hold the plastic wrap securely over the opening of the jar Water will eventually gather in the jar through the process of condensation Condensation occurs when the water vapor in the air is pulled out and turned into liquid water You might get a pint of water in about 24 hours If you were trying to survive in the desert your body would require about seven to eight pints 3 3 to 3 8 L of water each day you are exerting energy You could probably last about five days without water if you didn't exert any energy at all That means no walking not even at night Look at the water you gathered in your still Would it be enough for you to survive until you are rescued Would it be enough to sustain you walking at night to search for
