Introduction to
Climates
UNIT 9
STANDARDS: NCES 2.6.1, 2.6.2,
2.6.4, 2.7.2
LESSON 4
Lesson Objectives
 In this lesson, you will learn about:
– Describe the criteria for classifying climates
– Compare and contrast different climates
Koeppen Climate Classification
 According to the Koeppen Climate Classification System, the 5 basic
climate types are:
 Tropical, Dry, Temperate, Cold, and Polar.
Tropical Climates
 To remember a tropical climate, think HOT. Examples are Hawaii,
An area is considered tropical if its average coldest month is above
65°F. Some tropical areas are very wet, and some have wet and dry
seasons. Vegetation can range from grasses in the drier to tropical
rainforests.
Tropical Subclimates
 Within the tropical classification, the seasons are
distinguished by the amount of precipitation.
There are specific amounts of precipitation that
divide the subclimate. Sometimes, an easier way
to tell the subclimates apart is by vegetation.
Think of vegetation as a clue to the climate of an
area. In the tropical climates, the amount of
precipitation is a major factor in the vegetation of
an area. In some cases of the tropics, the more
rain, the more vegetation.
Tropical Savanna
 Tropical savannas sometimes act as a transition
zone between the wet tropical rain forest and the
dry desserts. The vegetation in tropical savanna
areas is usually grasses. Savannas occasionally
have scattered trees and shrubs. The tropical
savanna has the longest dry season of the tropical
climates, where its usual dry season is from
December to April.
Tropical Monsoon
 Monsoon climates have dry season, but are
known for their long, heavy rainy season. Most
monsoon climates are in South Asia. The dry
monsoon winds bring cool air from the north, but
no moisture. The wet monsoon winds carry
moisture from the Indian and Pacific Oceans
bringing heavy rains.
Tropical Rainforest
 The tropical rainforest subclimate has the most precipitation of the
tropical climates. It rains at least 2.3 inches even in the driest months;
it has no dry seasons
 Tropical rainforests are very close to the equator. They have very lush
rainforest vegetation composed of tall, leafy trees. The treetops form
a canopy, providing shade for the forest floor. The rainforests are
home to thousands of plant and animal species.
Dry Climates
 Think of very little or no rain. Think of Arizona, Idaho or
the Sahara Desert.
 Idaho? Dry climates can be hot or cold. The temperature
depends upon altitude and latitude. A portion of Idaho,
near Boise, is considered to be a dry climate.
 A climate is dry if it gets 20 inches of rain or less a year.
Vegetation can range from grassland to desert.
Dry Climates
 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.
Dry Climate: 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.
Dry Climate: 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:
– Requiring little water
– Storing Water
– Being widely spaced from other vegetation so its roots can absorb water
from a large area.
– A cactus is one example of desert vegetation.
Temperate Climate
 Most of the world’s population lives in temperate climates
because:
 Most of the land of the world is located in the mid-latitudes.
The mid-latitudes are where the temperate climates occur.
 Many people think of the temperate climate as the “just right”
climate. Not “too hot” like the tropics, and not “too cold” like
the colder climates. The temperate climates are just right for
human comfort and for growing crops that feed large
populations.
Temperate: Humid Subtropical
 The entire humid subtropical climate has warm,
wet summers. It has hot summer temperatures
that average above 71° F.
 This climate is very close to Tropical Savanna in
season and temperature, but is colder and has a
wider range of temperatures.
 Vegetation in the humid subtropical climate is
mixed forest and some grasses.
Temperate: Marine West Coast
 The marine west coast climate has wet winter and summer seasons. It
also has cool summers, with temperatures averaging below 71° F.
The name of the subclimate gives you an idea of its location. This
climate is found primarily on the west coasts of continents in midlatitudes.
 The marine west coast subclimate is farther from the equator than the
Mediterranean subclimate, and has coniferous forest vegetation.
 Cities in the Marine West Coast subclimate are: Edinburgh, Scotland;
Bremerhaven, Germany; Salem, Oregon
Temperate: Mediterranean
 Mediterranean areas have wet winters and dry
summers. Vegetation in Mediterranean areas is
varied. It ranges from scrub to grassland to
woodlands. Some people call this kind of
vegetation “chaparral”, a Spanish word that
means “an area of small evergreen oak trees.”
The Mediterranean climate occurs around most
of the Mediterranean Sea.
Cold Climates
 Think four seasons. Short growing seasons with frost. Think Vermont
and the Northeast.
 The Cold Climates have four seasons of about the same length. The
warmest month average is above 50 ° F and the coldest month
average is below 27° F. The precipitation varies. The vegetation is
mixed forest or evergreen forest.
 The cold climate is sometimes called the continental climate because
it forms over large continents. Almost no land masses in the Southern
Hemisphere are large enough to support this climate.
Cold: Humid Continental
 The humid continental subclimate has year-round
precipitation. The other cold climates do not have
precipitation all year. It has mixed forests and some grass
vegetation. The mixed forests make for a beautiful fall
with the changing colors of the leaves.
 Quebec Canada is an example of humid continental
subclimate.
Cold: Subarctic
 The subarctic subclimate has a dry winter
season—it receives 10 times more precipitation
in the summer than in winter. Subarctic climates
have coniferous forest vegetation.
 Reykjavik, Iceland is not subarctic due to the
higher temperatures and year-round rain.
However Irkutsk, Russia is subarctic due to
temperature and dry winters.
Polar
 Think cold and dry. Think about the poles. Think
Alaska or Antarctica.
 The Polar Climates are cold all year. The average
temperature of the warmest month is below 50°
F. The polar climates are also dry. The vegetation
is mosses and low shrubs or no vegetation at all.
Polar: Tundra
 The tundra subclass of polar climates has precipitation of
5 to 10 inches per year. It supports moss, lichen, and low
shrub vegetation. This is sometimes referred to as tundra
vegetation.
 Snow and ice melt for at least part of the year in tundra
areas, but the area is called permafrost, since lower layers
of the soil remain frozen year-round.
Polar: Polar Ice
 The polar ice subclass has no temperature above
50°F. It averages less than 10 inches of
precipitation per year. Since the polar ice cap
never melts, this subclass has no vegetation.
 The North Pole, Alaska is not polar ice due top
the temperatures above 50°F, but at the South
Pole Station, it is definitely Polar Ice.
Section Review 9.4.1
 Compare and contrast the five main
climates
 Describe the climate of North Carolina in
terms of temperature, rainfall, and
vegetation.
 Of the different types of climates, which do
you think would be the most strongly
influenced by the jet stream.