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Polar

Temperate

Tropical

Temperate

Polar

FIGURE 23.24 The principal climate zones are defined in terms of yearly temperature averages, which are determined by the amount of
solar radiation received at the different latitude groups.

during the other part. Overall temperatures are cooler than
in the low latitudes and have a wide seasonal variation.
3. Th e high latitudes receive a maximum amount of radiation
during one part of the year and none during another part.
Overall temperatures are low, with the highest range of
annual tem peratures.
The low, middle, and high latitudes provide a basic frame-
work for describing Earth’s climates. These climates are asso-
ciated with the low, middle, and high latitudes illustrated in
Figure 23.23, but they are defined in terms of yearly temperature
averages. It is necessary to define the basic climates in terms of
temperature because land and water surfaces react differently
to incoming solar radiation, creating a different temperature.
Temperature and moisture are the two most important climate
factors, and temperature will be considered first.
The principal climate zones are defined in terms of
yearly tem perature averages, which occur in broad regions (Fig-
ure 23.24). They are FIGURE 23.25 A wide variety of plant life can grow in a tropical
climate. Here is a tropical plant with an orange and red flower.
1. the tropical climate zone of the low latitudes (Figure 23.25),
2. the polar climate zone of the high latitudes (Figure 23.26),
during some winter days. Overall, the polar climate zone is cold.
and
Average monthly temperatures stay below 10°C (50°F), even
3. the temperate climate zone of the middle latitudes
during the warmest month of the year.
(Figure 23.27).
The temperate climate zone is between the polar and tropi-
The tropical climate zone is near the equator and receives the cal zones, with average temperatures that are neither very cold
greatest amount of sunlight throughout the year. Overall, the nor very hot. Average monthly temperatures stay between 10°C
tropical climate zone is hot. Average monthly temperatures stay and 18°C (50°F and 64°F) throughout the year.
above 18°C (64°F), even during the coldest month of the year. General patterns of precipitation and winds are also associ-
The other extreme is found in the polar climate zone, where ated with the low, middle, and high latitudes. An idealized model
the Sun never sets during some summer days and never rises of the global atmospheric circulation and pressure patterns was

23-17 CHAPTER 23 Weather and Climate 581