World Climate
Zones
Have you
ever wondered why one area of the world is a desert, another
a grassland, and another a rainforest? Why are there
different forests and deserts, and why are there different
types of life in each area? The answer is climate.
Climate is the
characteristic condition of the atmosphere near the earth's
surface at a certain place on earth. It is the long-term
weather of that area (at least 30 years). This includes the
region's general pattern of weather conditions, seasons and
weather extremes like hurricanes, droughts, or rainy
periods. Two of the most important factors determining an
area's climate are air temperature and
precipitation.
World biomes are
controlled by climate. The climate of a region will
determine what plants will grow there, and what animals will
inhabit it. All three components, climate, plants and
animals are interwoven to create the fabric of a
biome.
Some
facts about climate
The
sun's rays hit the equator at a direct angle
between 23 ° N and 23 ° S latitude.
Radiation that reaches the atmosphere here is
at its most intense.
In
all other cases, the rays arrive at an angle
to the surface and are less intense. The
closer a place is to the poles, the smaller
the angle and therefore the less intense the
radiation.
Our
climate system is based on the location of
these hot and cold air-mass regions and the
atmospheric circulation created by trade
winds and westerlies.
Trade
winds north of the equator blow from the
northeast. South of the equator, they blow
from the southeast. The trade winds of the
two hemispheres meet near the equator,
causing the air to rise. As the rising air
cools, clouds and rain develop. The resulting
bands of cloudy and rainy weather near the
equator create tropical
conditions.
Westerlies
blow from the southwest on the Northern
Hemisphere and from the northwest in the
Southern Hemisphere. Westerlies steer storms
from west to east across middle
latitudes.
Both
westerlies and trade winds blow away from the
30 ° latitude belt. Over large areas
centered at 30 ° latitude, surface winds
are light. Air slowly descends to replace the
air that blows away. Any moisture the air
contains evaporates in the intense heat. The
tropical deserts, such as the Sahara of
Africa and the Sonoran of Mexico, exist under
these regions.
Seasons
The
Earth rotates about its axis, which is tilted
at 23.5 degrees. This tilt and the sun's
radiation result in the Earth's seasons. The
sun emits rays that hit the earth's surface
at different angles. These rays transmit the
highest level of energy when they strike the
earth at a right angle (90 °).
Temperatures in these areas tend to be the
hottest places on earth. Other locations,
where the sun's rays hit at lesser angles,
tend to be cooler.
As
the Earth rotates on it's tilted axis around
the sun, different parts of the Earth receive
higher and lower levels of radiant energy.
This creates the seasons.
The Köppen
Climate Classification System is the most widely used for
classifying the world's climates. Most classification
systems used today are based on the one introduced in
1900 by the Russian-German climatologist Wladimir
Köppen. Köppen divided the Earth's surface into
climatic regions that generally coincided with world
patterns of vegetation and soils.
The Köppen
system recognizes five major climate types based on the
annual and monthly averages of temperature and
precipitation. Each type is designated by a capital
letter.
A
- Moist Tropical Climates are known for their high
temperatures year round and for their large amount of
year round rain.
B - Dry
Climates are characterized by little rain and a huge
daily temperature range. Two subgroups, S -
semiarid or steppe, and W - arid or desert, are
used with the B climates.
C - In
Humid Middle Latitude Climates land/water differences
play a large part. These climates have warm,dry
summers and cool, wet winters.
D -
Continental Climates can be found in the interior
regions of large land masses. Total precipitation is
not very high and seasonal temperatures vary
widely.
E -
Cold Climates describe this climate type perfectly.
These climates are part of areas where permanent ice
and tundra are always present. Only about four months
of the year have above freezing
temperatures.
Further subgroups
are designated by a second, lower case letter which
distinguish specific seasonal characteristics of
temperature and precipitation.
f
- Moist with adequate precipitation in all months and
no dry season. This letter usually accompanies the
A, C, and D climates.
m -
Rainforest climate in spite of short, dry season in
monsoon type cycle. This letter only applies to
A climates.
s -
There is a dry season in the summer of the respective
hemisphere (high-sun season).
w -
There is a dry season in the winter of the respective
hemisphere (low-sun season).
To further denote
variations in climate, a third letter was added to the
code.
a
- Hot summers where the warmest month is over
22°C (72°F). These can be found in C
and D climates.
b -
Warm summer with the warmest month below 22°C
(72°F). These can also be found in C and
D climates.
c -
Cool, short summers with less than four months over
10°C (50°F) in the C and D
climates.
d -
Very cold winters with the coldest month below
-38°C (-36°F) in the D climate
only.
h -
Dry-hot with a mean annual temperature over 18°C
(64°F) in B climates only.
k -
Dry-cold with a mean annual temperature under
18°C (64°F) in B climates
only
Köppen
Climate Classification System |
- Tropical
Moist Climates
(Af)
rainforest
Rainfall is heavy in all
months. The total annual rainfall is often more than
250 cm. (100 in.). There are seasonal differences in
monthly rainfall but temperatures of 27°C
(80°F) mostly stay the same. Humidity is between
77 and 88%.
High surface heat and humidity
cause cumulus clouds to form early in the afternoons
almost every day.
The climate on eastern sides
of continents are influenced by maritime tropical air
masses. These air masses flow out from the moist
western sides of oceanic high-pressure cells, and
bring lots of summer rainfall. The summers are warm
and very humid. It also rains a lot in the
winter
- Average
temperature: 18 °C (°F)
- Annual
Precipitation: 262 cm. (103 in.)
- Latitude
Range: 10° S to 25 ° N
- Global
Position: Amazon Basin; Congo Basin of equatorial
Africa; East Indies, from Sumatra to New
Guinea.
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- Wet-Dry
Tropical Climates
(Aw)
savanna
A seasonal
change occurs between wet tropical air masses and dry
tropical air masses. As a result, there is a very wet
season and a very dry season. Trade winds dominate
during the dry season. It gets a little cooler during
this dry season but will become very hot just before
the wet season.
- Temperature
Range: 16 °C
- Annual
Precipitation: 0.25 cm. (0.1 in.). All months less
than 0.25 cm. (0.1 in.)
- Latitude
Range: 15 ° to 25 ° N and S
- Global
Range: India, Indochina, West Africa, southern
Africa, South America and the north coast of
Australia
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- Dry
Tropical Climate (BW)
desert
biome
These desert
climates are found in low-latitude deserts
approximately between 18° to 28° in both
hemispheres. these latitude belts are centered on the
tropics of Cancer and Capricorn, which lie just north
and south of the equator. They coincide with the edge
of the equatorial subtropical high pressure belt and
trade winds. Winds are light, which allows for the
evaporation of moisture in the intense heat. They
generally flow downward so the area is seldom
penetrated by air masses that produce rain. This makes
for a very dry heat. The dry arid desert is a true
desert climate, and covers 12 % of the Earth's land
surface.
- Temperature
Range: 16° C
- Annual
Precipitation: 0.25 cm (0.1 in). All months less
than 0.25 cm (0.1 in).
- Latitude
Range: 15° - 25° N and S.
- Global
Range: southwestern United States and northern
Mexico; Argentina; north Africa; south Africa;
central part of Australia.
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Group
II
Mid-latitude
Climates:
Climates
in this zone are affected by two different air-masses.
The tropical air-masses are moving towards the poles
and the polar air-masses are moving towards the
equator. These two air masses are in constant
conflict. Either air mass may dominate the area, but
neither has exclusive control.
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- Dry
Midlatitude Climates
(BS)
steppe
Characterized
by grasslands, this is a semiarid climate. It can
be found between the desert climate (BW) and more
humid climates of the A, C, and D groups. If it
received less rain, the steppe would be classified
as an arid desert. With more rain, it would be
classified as a tallgrass prairie.
This dry
climate exists in the interior regions of the North
American and Eurasian continents. Moist ocean air
masses are blocked by mountain ranges to the west
and south. These mountain ranges also trap polar
air in winter, making winters very cold. Summers
are warm to hot.
- Temperature
Range: 24° C (43° F).
- Annual
Precipitation: less than 10 cm (4 in) in the
driest regions to 50 cm (20 in) in the moister
steppes.
- Latitude
Range: 35° - 55° N.
- Global
Range: Western North America (Great Basin,
Columbia Plateau, Great Plains); Eurasian
interior, from steppes of eastern Europe to the
Gobi Desert and North China.
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- Mediterranean
Climate (Cs)
chaparral
biome
This is a
wet-winter, dry-summer climate. Extremely dry
summers are caused by the sinking air of the
subtropical highs and may last for up to five
months.
Plants have
adapted to the extreme difference in rainfall and
temperature between winter and summer seasons.
Sclerophyll plants range in formations from
forests, to woodland, and scrub. Eucalyptus forests
cover most of the chaparral biome in
Australia.
Fires occur
frequently in Mediterranean climate
zones.
- Temperature
Range: 7 °C (12 °F)
- Annual
Precipitation: 42 cm (17 in).
- Latitude
Range: 30° - 50° N and S
- Global
Position: central and southern California;
coastal zones bordering the Mediterranean Sea;
coastal Western Australia and South Australia;
Chilean coast; Cape Town region of South
Africa.
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- Dry
Midlatitude Climates
(Bs)
grasslands
biome
These dry
climates are limited to the interiors of North
America and Eurasia.
Ocean air
masses are blocked by mountain ranges to the west
and south. This allows polar air masses to dominate
in winter months. In the summer, a local
continental air mass is dominant. A small amount of
rain falls during this season.
Annual
temperatures range widely. Summers are warm to hot,
but winters are cold.
- Temperature
Range: 31 °C (56°F).
- Annual
Precipitation: 81 cm. (32 in.).
- Latitude
Range: 30° - 55° N and S
- Global
Position: western North America (Great Basin,
Columbia Plateau, Great Plains); Eurasian
interior.
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- Moist
Continental Climate (Cf)
Deciduous
Forest biome
This
climate is in the polar front zone - the
battleground of polar and tropical air masses.
Seasonal changes between summer and winter are very
large. Daily temperatures also change often.
Abundant precipitation falls throughout the year.
It is increased in the summer season by invading
tropical air masses. Cold winters are caused by
polar and arctic masses moving south.
- Temperature
Range: 31 °C (56 ° F)
- Average
Annual Precipitation: 81 cm (32 in).
- Latitude
Range: 30° - 55° N and S (Europe:
45° - 60° N).
- Global
Position: eastern parts of the United States and
southern Canada; northern China; Korea; Japan;
central and eastern Europe.
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Group
III
- High-latitude
climates:
Polar and
arctic air masses dominate these regions. Canada and
Siberia are two air-mass sources which fall into this
group. A southern hemisphere counterpart to these
continental centers does not exist. Air masses of arctic
origin meet polar continental air masses along the 60th
and 70th parallels.
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- Boreal
forest Climate ( Dfc)
taiga
biome
This is a
continental climate with long, very cold winters, and
short, cool summers. This climate is found in the
polar air mass region. Very cold air masses from the
arctic often move in. The temperature range is larger
than any other climate. Precipitation increases during
summer months, although annual precipitation is still
small.
Much of the
boreal forest climate is considered humid. However,
large areas in western Canada and Siberia receive very
little precipitation and fall into the subhumid or
semiarid climate type.
- Temperature
Range: 41 °C (74 °F), lows; -25 °C
(-14 °F), highs; 16 °C (60
°F).
- Average
Annual Precipitation: 31 cm (12 in).
- Latitude
Range: 50° - 70° N and S.
- Global
Position: central and western Alaska; Canada, from
the Yukon Territory to Labrador; Eurasia, from
northern Europe across all of Siberia to the
Pacific Ocean.
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- Tundra
Climate (E)
tundra
biome
The tundra
climate is found along arctic coastal areas. Polar and
arctic air masses dominate the tundra climate. The
winter season is long and severe. A short, mild season
exists, but not a true summer season. Moderating ocean
winds keep the temperatures from being as severe as
interior regions.
- Temperature
Range: -22 °C to 6 °C (-10 °F to 41
°F).
- Average
Annual Precipitation: 20 cm (8 in).
- Latitude
Range: 60° - 75° N.
- Global
Position: arctic zone of North America; Hudson Bay
region; Greenland coast; northern Siberia bordering
the Arctic Ocean.
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- Highland
Climate (H)
Alpine
Biome
Highland
climates are cool to cold, found in mountains and high
plateaus. Climates change rapidly on mountains,
becoming colder the higher the altitude gets. The
climate of a highland area is closely related to the
climate of the surrounding biome. The highlands have
the same seasons and wet and dry periods as the biome
they are in.
Mountain
climates are very important to midlatitude biomes.
They work as water storage areas. Snow is kept back
until spring and summer when it is released slowly as
water through melting.
- Temperature
Range: -18 °C to 10 °C (-2 °F to
50°F)
- Average
Annual Precipitation: 23 cm (9 in.)
- Latitude
Range: found all over the world
- Global
Position: Rocky Mountain Range in North America,
the Andean mountain range in South America, the
Alps in Europe, Mt. Kilimanjaro in Africa, the
Himalayans in Tibet, Mt. Fuji in Japan.
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