wet. In the winter, when the ITCZ moves back toward the equator, the region is dry. This
climate exists where strong monsoon winds blow from land to sea, such as in India.
Rainforests cannot survive the months of low rainfall, so the typical vegetation issavanna
(Figure17.10). This biome consists mostly of grasses, with widely scattered deciduous trees
and rare areas of denser forests. Central Africa is famous for its savanna and the unique
animals that live there.
Figure 17.10: A male lion stalks the African savanna. ( 19 )Dry Climates (Group B)
TheDry Climates (Group B) generally have less precipitation than evaporation and are
further from the equator than Tropical (Group A) climates. They have cooler winters and
longer, harsher dry seasons. Rainfall is irregular; several years of drought are often followed
by a single year of abundant rainfall. Summer temperatures are high, and much of the rain
evaporates before it reaches the ground. Dry climate zones cover about 26% of the world’s
land area. Low latitudedesertsform as a result of the Ferrell cell high pressure zone. Higher
latitude deserts occur within continents or in rain shadows where the air has little humidity.
Arid Desert (Bw)
Low-latitude, arid deserts are found between 15° to 30° N and S latitudes. This is where
warm dry air sinks at high pressure zones. True deserts make up around 12% of the world’s
lands. Deserts are found in southwestern North America, Africa, Australia and central Asia.
Humidity is low, and as a result there are few clouds in the sky. The Sahara is the world’s
largest desert (Figure17.11).
In the Sonora Desert of the southwestern United States and northern Mexico, most weather
stations record sunshine 85% of the time, both in summer and winter (Figure17.12). Clear
skies allow the ground to heat rapidly during the day and cool rapidly at night. The summer