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upon temperature. As temperatures climb, potential evaporation
also increases. 25 cm of rain may support only a sparse vegetative
cover in Nevada, whereas the same amount of precipitation falling
in northern Scandinavia is sufficient to support forests.
Within these water-deficient regions, two climatic types are
commonly recognized: desert, which is arid, and steppe, which is
semiarid. The two share many features; their differences are
primarily matters of degree. The steppe is a marginal and more
humid variant of the desert and is a transition zone that surrounds
the desert and separates it from bordering humid climates.
Unlike their low-latitude counterparts, middle-latitude
deserts and steppes are not controlled by the subsiding air masses
associated with high pressure. Instead, these dry lands exist
principally because they are sheltered in the deep interiors of large
landmasses. They are far removed from the ocean, which is the
ultimate source of moisture for cloud formation and precipitation.
One well-known example is the Gobi Desert of central Asia.
The presence of high mountains across the paths of
prevailing winds further separates these areas from water-bearing
maritime air masses. Also, the mountains force the air to lose
much of its water. The mechanism is simple: As prevailing winds
meet mountain barriers, the air is forced to ascend. When air rises,
it expands and cools, a process that can produce clouds and
precipitation.
The windward sides of mountains, therefore, often have
high precipitation. By contrast, the leeward sides of mountains are
usually much drier. This situation exists because air reaching the
leeward side has lost much of its moisture, and if the air descends,
it is compressed and warmed, making cloud formation even less
likely. The dry region that results is often referred to as a
rainshadow desert.

Task 3. Answer the following questions in written form.
0. What does the word desert literally mean?

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