World Climate Types. The global distribution of the world climate
controls is responsible for the development of fourteen widely
recognized climate types. In this section, the major characteristics
of each of these climates will be briefly described.
The climates are discussed in a rough poleward sequence.
Tropical Wet Climate. Sometimes called the tropical rain forest cli-
mate, the tropical wet climate exists chiefly in areas lying within 10 de-
grees of the equator. It is an almost seasonless climate, characterized by
year-round warm, humid, rainy conditions that allow land areas to sup-
port a dense broadleaf forest cover. The warm temperatures, which for
most locations average near 80 degrees Fahrenheit (27 degrees Celsius)
throughout the year, result from the constantly high midday sun angles
experienced at this low latitude. The heavy precipitation totals result
from the heating and subsequent rising of the warm moist air to form fre-
quent showers and thunderstorms, especially during the afternoon
hours. The dominance of the ITCZ enhances precipitation totals, help-
ing make this climate type one of the world’s rainiest.
Tropical Monsoonal Climate. The tropical monsoonal climate occurs
in low-latitude areas, such as Southeast Asia, that have a warm, rainy cli-
mate with a short dry season. Temperatures are similar to those of the
tropical wet climate, with the warmest weather often occurring during
the drier period, when sunshine is more abundant. The heavy rainfalls re-
sult from the nearness of the ITCZ for much of the year, as well as the
dominance of warm, moist air masses derived from tropical oceans. Dur-
ing the brief dry season, however, the ITCZ has usually shifted into the
opposite hemisphere, and windflow patterns often have changed so as to
bring in somewhat drier air derived from continental sources.
Tropical Savanna Climate. The tropical savanna climate, also referred
to as the tropical wet and dry climate, occupies a large portion of the
Tropics between 5 and 20 degrees latitude in both hemispheres. It experi-
ences a distinctive alternation of wet and dry seasons, caused chiefly by
the seasonal shift in latitude of the subtropical highs and ITCZ. Summer
is typically the rainy season because of the domination of the ITCZ. In
many areas, an onshore windflow associated with the summer monsoon
increases rainfalls at this time. In winter, however, the ITCZ shifts into the
opposite hemisphere and is replaced by drier and more stable air associ-
ated with the subtropical high. In addition, the winter monsoon ten-
dency often produces an outflow of continental air. The long dry season
inhibits forest growth, so vegetation usually consists of a cover of drought-
resistant shrubs or the tall savanna grasses after which the climate is
named.
Subtropical Desert Climate. The subtropical desert climate has hot,
arid conditions as a result of the year-round dominance of the subtropical
highs. Summertime temperatures in this climate soar to the highest read-
ings found anywhere on earth. The world’s record high temperature was
136.4 degrees Fahrenheit (58 degrees Celsius), recorded in El Azizia,
Libya, in the northern Sahara Desert. Rainfall totals in this type of climate
are generally less than 10 inches (25 centimeters) per year. What rainfall
does occur often arrives as brief, sometimes violent, afternoon thunder-
storms. Although summer temperatures are extremely hot, the dry air
enables rapid cooling during the winter, so that temperatures are cool
to mild at this time of year.
Subtropical Steppe Climate. The subtropical steppe climate is a semi-
arid climate, found mostly on the margins of the subtropical deserts. Pre-
cipitation usually ranges from 10 to 30 inches (25 to 75 centimeters), suf-
ficient for a ground cover of shrubs or short steppe grasses. Areas on the
equatorward margins of subtropical deserts typically receive their precip-
itation during a brief showery period in midsummer, associated with the
poleward shift of the ITCZ. Areas on the poleward margins of the sub-
tropical highs receive most of their rainfall during the winter, due to the
penetration of cyclonic storms associated with the equatorward shift of
the westerly wind belt.
Mediterranean Climate. The Mediterranean climate, also sometimes
referred to as the dry summer subtropics, has a distinctive pattern of dry
summers and more humid, moderately wet winters. This pattern is
caused by the seasonal shift in latitude of the subtropical high and the
westerlies. During the summer, the subtropical high shifts poleward into
the Mediterranean climate regions, blanketing them with dry, warm, sta-
ble air. As winter approaches, this pressure center retreats equatorward,
allowing the westerlies, with their eastward-traveling weather fronts and
cyclonic storms, to overspread this region. The Mediterranean climate is
found on the windward sides of continents, particularly the area sur-
rounding the Mediterranean Sea and much of California. This results in
the predominance of maritime air and relatively mild temperatures
throughout the year.
Humid Subtropical Climate. The humid subtropical climate is found
on the eastern, or leeward, sides of continents in the lower middle lati-
tudes. The most extensive land area with this climate is the southeastern
United States, but it is also seen in large areas in South America, Asia, and
Australia. Temperature ranges are moderately large, with warm to hot
summers and cool to mild winters. Mean temperatures for a given loca-
tion are dictated largely by latitude, elevation, and proximity to the coast.
Precipitation is moderate. Winter precipitation is usually associated with
weather fronts and cyclonic storms that travel eastward within the west-
erly wind belt. During summer, most precipitation is in the form of brief,
heavy afternoon and evening thunderstorms. Some coastal areas are sub-
ject to destructive hurricanes during the late summer and autumn.
Midlatitude Desert Climate. This type of climate consists of areas
within the western United States, southern South America, and Central
Asia that have arid conditions resulting from the moisture-blocking influ-
ence of mountain barriers. This climate is highly continental, with warm
summers and cold winters. When precipitations occurs, it frequently
comes in the form of winter snowfalls associated with weather fronts and
cyclonic storms. Rainfall in summer typically occurs as afternoon thun-
derstorms.
Midlatitude Steppe. The midlatitude steppe climate is located in inte-
rior portions of continents in the middle latitudes, particularly in Asia
and North America. This climate has semiarid conditions caused by a
combination of continentality resulting from the large distance from oce-
anic moisture sources and the presence of mountain barriers. Like the
midlatitude desert climate, this climate has large annual temperature
ranges, with cold winters and warm summers. It also receives winter rains
and snows chiefly from weather fronts and cyclonic storms; summer rains
occur largely from afternoon convectional storms. In the Great Plains of
the United States, spring can bring very turbulent conditions, with bliz-
zards in early spring and hailstorms and tornadoes in mid to late spring.
Marine West Coast. This type of climate is typically located on the west
coasts of continents just poleward of the Mediterranean climate. Its loca-
tion in the heart of the westerly wind belt on the windward sides of conti-
nents produces highly maritime conditions. As a result, cloudy and hu-
mid weather is common, along with frequent periods of rainfall from
passing weather fronts and cyclonic storms. These storms are often well
developed in winter, resulting in extended periods of wet and windy
weather. Precipitation amounts are largely controlled by the presence
and strength of the orographic effect; mountainous coasts like the north-
western United States and the west coast of Canada are much wetter than
are flatter areas like northern Europe. Temperatures are held at moder-
ate levels by the onshore flow of maritime air. As a consequence, winters
are relatively mild and summers relatively cool for the latitude.
Humid Continental Climate. The humid continental climate is found
in the northern interiors of Eurasia (Europe and Asia) and North Amer-
ica. It does not occur in the Southern Hemisphere because of the abence
of large land masses in the upper midlatitudes of that hemisphere. This
climate type is characterized by low to moderate precipitation that is
largely frontal and cyclonic in nature. Most precipitation occurs in summer,
but cold winter temperatures typically cause the surface to be frozen and
snow-covered for much of the late fall, winter, and early spring. Temperature
ranges in this climate are the largest in the world. In Siberia, for example,
mean temperatures in July can average more than 108 degrees Fahrenheit
(60 degrees Celsius) warmer than in January. Winter temperatures in parts
of both North America and Siberia can fall well below -58 degrees Fahrenheit
(-50 degrees Celsius), making these the coldest permanently settled sites
in the world.
Tundra Climate. The tundra climate is a severely cold climate that ex-
ists mostly on the coastal margins of the Arctic Ocean in extreme north-
ern North America and Eurasia, and along the coast of Greenland. The
high-latitude location and proximity to icy water cause every month to
have average temperatures below 50 degrees Fahrenheit (10 degrees Cel-
sius), although a few months in summer have means above freezing. As a
result of the cold temperatures, tundra areas are not forested, but instead
typically have a sparse ground cover of grasses, sedges, flowers, and li-
chens. Even this vegetation is buried by a layer of snow during most of the
year. Cold temperatures lower the water vapor holding capacity of the air,
causing precipitation totals to be generally light. Most precipitation is as-
sociated with weather fronts and cyclonic storms and occurs during the
summer half of the year.
Ice Cap Climate. The most poleward and coldest of the world’s cli-
mates is called the ice cap climate. It is found on the continent of Antarc-
tica, interior Greenland, and some high mountain peaks and plateaus.
Because monthly mean temperatures are subfreezing throughout the
year, areas with this climate are glaciated and have no permanent human
inhabitants.
The coldest temperatures of all occur in interior Antarctica, where a Russian
research station named Vostok recorded the world’s coldest temperature of
-128.6 degrees Fahrenheit (-89.2 degrees Celsius) on July 21, 1983. This
climate receives little precipitation because the atmosphere can hold very
little water vapor. A major moisture surplus exists, however, because of the
lack of snowmelt and evaporation. This causes the build up of a surface
snow cover that eventually compacts to form the icecaps that bury the surface.
Snowstorms are often accompanied by high winds, producing blizzard conditions.
Ralph C. Scott
Geography basics / editor, Ray Sumner. Magill’s choice, Salem Press
Pages 106-114; ISBN 1-58765-177-7
For Further Study
Aguado, Edward, and James E. Best. Understanding Weather and Climate.
Englewood Cliffs, N.J.: Prentice Hall, 1999.
Ahrens, C. Donald. Meteorology Today: An Introduction to Weather, Climate,
and the Environment. 6th ed. Pacific Grove, Calif.: Brooks/Cole, 2000.
Barry, Roger G., and Richard J. Chorley. Atmosphere, Weather, and Climate.
7th ed. New York: Routledge, 1998.
Gabler, Robert E., Robert J. Sager, and Daniel L. Wise. Essentials of Physical
Geography. 5th ed. New York: Saunders College Publishing, 1997.
Hidore, John J., and John E. Oliver. Climatology: An Atmospheric Science. En-
glewood Cliffs, N.J.: Prentice Hall, 1993.
McKnight, Tom L., and Darrel Hess. Physical Geography: A Landscape Ap-
preciation. 6th ed. Englewood Cliffs, N.J.: Prentice Hall, 2000.
Rosenzweig, Cynthia. Climate Change and the Global Harvest: Potential Im-
pacts of the Greenhouse Effect on Agriculture. New York: Oxford University
Press, 1998.
Information on the World Wide Web
The World Climate Web site contains temperature and precipitation statistics
in both metric and imperial (standard American) units for thousands of worldwide
climate-reporting stations, all of which are identified by latitude, longitude, and
elevation. Various maps, with enlargement and reduction capabilities, are
provided to show the locations of the stations.
(www.worldclimate.com/climate/)
