is strongest (most direct) near the equator (tropics). The heated
air rises and as it does, it cools. Cool air can't hold as much
water as warm air, so low pressure (L) forms, creating clouds and
tropical rain belt runs along the equator and spreads
out to about the Tropic of Cancer (23.5 north latitude) and Tropic
of Capricorn (23.5 south latitude). But by the time it reaches about
30 degrees north and south latitude, it's cool enough to sink back
to the surface. This creates high pressure (H), which means drier
conditions. Most of the world's deserts are at
you notice that one of the rainiest regions is closest to the
equator (tropical zone)? Where did you notice
you notice that an orange rain band moves north from South America
(the equator) to Central America and Mexico during the summer?
Then it moves south during the winter?
of our long-distant migrants, such as hummingbirds and monarchs,
winter in the tropics or subtropics.
circulation continues, moving away from the equator through the
force of global winds.* Those of us living in temperate
zones (from 30 to 60 degrees north and south latitudes)
have varied precipitation (rain, snow, or both) in each of our
four seasons. The poles, in turn, are very dry.
Winds are created by unequal heating of air masses above land
and the oceans. These circulate air globally. Learn
More About Global Wind Systems.
at a globe or map and find your state or hometown. What is its
latitude? Which of the climate zones on the above "globe"
and on the Climate
Zone Chart do you live in?
the same thing for the winter and breeding habitats of the migrating
animal(s) you're studying. Describe the climates in these two
habitats. What does it tell you about your animal's basic needs
or ability to survive?
Causes Wet and Dry Seasons?
In many tropical and subtropical regions, rainfall varies
much more than temperature does. Also, because the earth tilts,
the direct sun rays, and in turn, the tropical rain belt, shifts
from the northern to the southern tropics. So these areas experience
just two seasons: a wet season and a dry season.
Wet season in the southern tropics/subtropics
Dry season in the northern tropics/subtropics
(e.g., monarch winter habitat)
Dry season in the southern tropics/subtropics
Wet season in the northern tropics/subtropics
on the equator, there are two wet and two dry seasons as the rain
belt passes over twice a year, once moving north and once moving
learn about global temperatures >>
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