Dry Climates
Introduction
Have you ever heard people say that a place is hot, but you don’t notice so much because
“it’s dry heat”? What is dry heat? Where are these dry places? Are all dry places hot?
There are two types of dry climates: steppe and desert. Both are dry, but desert is the
drier of these two areas. Both are dry, but not always hot.
The Dry Climates
The distinguishing feature of dry climates is a complicated mathematical formula that
measures the precipitation against the evaporation potential. Some people describe it as
evaporation exceeding precipitation, but that would be impossible after a certain point.
In dry climates, precipitation is very scarce. When it does rain, the rain evaporates as fast
as possible. Most climates that have 20 inches of precipitation or less fall into this
category. A dry climate is a place that has an average of 20 inches of rain or less per
year. Dry climates are the only climates classified by precipitation. Other climate types
are classified by temperature.
Until you get to the colder climates, if an area has precipitation of less than 20 inches per
year, it is dry, regardless of temperature. Once the average temperature of the warmest
month gets below 50 ° F, however, temperature is more important. Those areas are called
cold climates, not dry climates.
Dry climates are classified as steppe or desert. The difference lies in the amount of
precipitation. Notice that these are also names of vegetation classifications. You can use
vegetation as a clue to the climate. The more vegetation there is, the more rain must fall.
This lesson uses the Koeppen Climate Classification System to describe each subclimate.
The Uppercase B in each climate code refers to dry climate. Bs stands for semiarid steppe
climate; Bw stands for the arid desert climate.
Bs = steppe
Bw = desert
Steppe
Steppe climates are considered semiarid. This means they receive more rain than the arid
desert climate, but not much more. Steppe climates average about 10-20 inches of rain
per year. Steppe climates have the short-grass vegetation, known as steppe vegetation.
Trees are rare except along riverbanks. Steppes are often a transition zone between
desert areas and more humid climates.
Human Activity
The steppe areas are like tropical savanna areas in that their grassy vegetation can be used
for grazing. The steppe areas are unlike the tropical savanna areas because they make for
poor farmland. Some crops are grown, but unless the dry soil is irrigated, it cannot
support more than family farming for a short time. Many farmers in the steppe areas have
to move to another area every few years because the soil quality is easily depleted.
Desert
Desert climate are considered arid. This means that they average less than 10 inches of
rain per year. Desert climates have no wet season. Desert climates have very little or no
vegetation. When they do have plant life it survives by:
a. Requiring little water
b. Storing Water
c. Being widely spaced from other vegetation so its roots can absorb water from a
large area.
d. A cactus is one example of desert vegetation.
Human Activity
The desert climate areas have very sparse vegetation, so any farming or grazing must be
done with great care. People native to these areas have developed practices that sustain
the sparse vegetation and soil nutrients that are available.
With advancements of irrigation and damming techniques, many oases have been created
from desert areas. Human activity in these areas can be varied, but is dependent on warter
sources from outside the area.
Arid Oasis near Dubai
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