Climate Types:
Mild Climates
Mild climates are characterized by seasonality in temperature. Mild climates have mild winters
and mild to hot summers depending on the sub group. Different Mild climates are based on
which season precipitation occurs in and the severity of winters. There are three sub groups of
the mild climate type:
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Mediterranean
Humid Sub Tropical
Marine West Coast
Mediterranean
The Mediterranean basin contains the largest area of this climate. This climate is also found on
the west coasts of middle latitude continents in for example, California, Central Chili, South
Africa and Western/Central Australia. This Mediterranean climate has long, hot, dry summers
and mild, rainy winters. Average summer temperatures are 75F and winter temperatures average
45F. The subtropical high-pressure cell affects the climate in the summer producing arid
conditions. The wet winter occurs when the westerlies bring in moisture from the oceans.
Humid Subtropical Climate
Found on the Southeastern side of continents primarily between 30-40 degrees latitude. This
climate is hot, humid during the long summers, cool, and humid during the short winter season.
This climate is a transition between the tropical rainy climates and the more severe continental
climates that occur towards the poles. In the U.S. and China, polar air masses bring cold "spells"
in winter. During the winter season, precipitation from storms dominates the areas This frontal
precipitation is replaced by precipitation caused by convection during the summer. The water
budget for most of this climate is a surplus and the deficit at the remaining locations usually
occurs for no more than 2-3 months. Summers average 86F while winters are a mild 45 F.
Marine West Coast Climate
This climate occurs poleward of the dry subtropical climates on the western sides of continents
and can extend quite a distance. The prevailing westerly winds constantly bring in moisture from
the oceans. If a warm ocean current is present offshore the climate is even more moist and mild.
The degree to which this climate extends inland depends on the presence or absence of mountain
barriers. Locations include:
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The west coast of U.S. from N. California to the panhandle of Alaska.
Southern Chile (narrow band because of mountains).
NW Europe - extends far inland because of lack of North-South trending mountains.
This climate is very mild because of the modifying effects of the ocean. This climate does not
have large seasonal extremes of temperature, summers are cool and winters are mild. Average
summer temps are 60F -65F. Average winter temps are 30-45F. Freezing temperatures are
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more frequent and more severe then in the Humid Subtropic subgroup but the growing season is
still quite long (6-8 months) considering the latitude. Rainfall is adequate throughout the year,
the water budget always shows a surplus. Places such as Europe get 25-30 inches per year. In
areas with mountain barriers precipitation can be high (40-100"/year) on the windward side.
Dry or Arid Climates:
Little rain and a large variation in daily temperatures characterize dry Climates. There are two
climate sub groups:
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Arid or Desert
Semi-Arid
In both climate groups, the temperature change between night and day is considerable. One
reason for the wide swings in temperature is that skies are clear and the air is dry. There are no
clouds to reflect the sun’s heat during the day, which increases the temperature on the ground. At
night, there are no clouds to slow the rate of cooling, resulting in colder nights.
Semi-Arid and desert climates occur over a greater land area than any other climate grouping.
They occur in both the tropics and middle latitudes. They cover broad east-west bands near 30
degrees north and south latitude. Desert plants have adapted to survive extreme dryness and
extreme temperature ranges. They are genrally low to the ground with small, few or no leaves.
Semi-arid and desert climates are in the rain shadows of mountain ranges. Winds that descend
the leeward slopes of these ranges are warm and dry. Semi-arid and deserts climates differ from
tropical climates mainly in their seasonal temperature changes. Winters are much colder in the
semi-arid and desert climates.
Arid Climate
The Arid climate sub group are deserts that lie approximately between 18-28 degrees latitude
in both hemispheres. They coincide with the equatorward edge of the subtropical high pressure
belt and trade winds. This group Includes the world's great deserts: Sahara, Sonoran, Thar,
Kalahari, Great Australian. Environmental conditions are harsh; searing heat is present most of
the year. Summers average 95F while winters average 59F. Air flows generally downward so
air masses that cause rain rarely penetrate the area. There is a general lack of precipitation with
no pattern developed.
Semi-arid
This climate sub group is found surrounding the low-latitude deserts. They usually border desert
climates You cannot distinguish between the Arid and Semi-Arid climates by temperature only,
but need to consider precipitation as well. Summers average 69F and winters average 26F.
Although the precipitation in the Semi-Arid climate is not very much, it is greater than the
deserts. The typical semi-arid region has greater than 10" of precipitation per year and always
less than 30".
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Continental Climates
Continental climates are typical of the middle-latitude interiors of the large continents of the
Northern Hemisphere in the zone of westerly winds. They are also found along the east coasts
and southwest coasts of the same continents, and also at higher elevations in certain other parts
of the world. Snow is a major elelment in the precipitation of Continental climates. This climate
is characterized by winter temperatures cold enough to support a fixed period of stable snow
cover each year, and relatively low precipitation occurring mostly in summer, although east coast
areas (chiefly in North America) may show an even distribution of precipitation.
These regions generally have either forest or tall-grass prairie as natural vegetation and include
some of the most productive farmlands in the world. All such climates have at least three months
of temperatures in excess of 50°F and winters with at least one month below 32°F.
The Midwestern United States, parts of China, and most of Russia are examples of areas of the
world with continental climates. Continental climates do not exist at all in the Southern
Hemisphere due to the lack of broad land masses at middle latitudes.
There are two main sub groups of continental climates are:
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Humid Continental
Sunacrtic.
Humid Continental (Warm Summer)
The humid continental climate is found over large areas of landmasses in the temperate regions
of the mid latitudes where there is a zone of conflict between polar and tropical air masses.
Variable weather patterns and a large temperature range mark the humid continental climate. The
seasonal temperature variance can be as great as 55 to 70 degrees Fahrenheit. Winter
temperatures average 23F and summers average 77F. The temperature difference between the
warmest and coldest months increases inland, away from the moderating influence of the ocean.
Subarctic
Very cold winters, and brief, warm summers characterize regions having a subarctic climate.
Average July temperatures are 63F. January temperatures average -10F. This type of climate
offers some of the most extreme seasonal temperature variations found on the planet: In winter,
temperature can drop to −40°F and in summer, the temperature may exceed 86°F.
The Subarctic climate is found in much of Siberia, Scandinavia, most of Alaska and much of
Canada from about 50°N to the tree line. It is found on large landmasses, away from the
moderating effects of an ocean, at latitudes from 50° to 70°. It is not found in the southern
hemisphere because there is no sufficiently large landmass at the same latitudes.
With 6-7 consecutive months where the average temperature is below freezing, all moisture in
the soil and subsoil freezes solidly to depths of many feet. Summer warmth is insufficient to
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thaw more than a few surface feet, so permafrost prevails under large areas. Seasonal thaw
penetrates from 2 to 14 ft, depending on latitude.
Tropical Climates
Places close to the Equator are known as the tropics and these areas experience a tropical
climate. The weather is usually hot and humid, and during the wet season, it rains heavily and
regularly almost every day. Daytime temperatures, even in the winter, rarely fall below 77 ° F
and generally average around 80F. However, temperatures in the tropics are not as hot as the
deserts that lie north and south of the tropical zones. Temperatures in the tropics rarely rise
above 95 ° F.
All subgroups of tropical climates experience hot and humid weather. There is abundant rainfall
due to the active vertical uplift or convection of air that takes place there, and during certain
periods, thunderstorms can occur every day. Nevertheless, this belt still receives considerable
sunshine, and with the excessive rainfall, provides ideal growing conditions for luxuriant
vegetation. The principal regions with a tropical climate are the Amazon Basin in Brazil, the
Congo Basin in West Africa and Indonesia. The two subgroups of a tropical climate are:
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Tropical Wet and Dry
Tropical Wet or Rainforest
Tropical Wet and Dry
The primary feature of this subgroup is the monsoon winds. This climate subgroup has a
pronounced dry season with the driest month having precipitation of less than 1 to 2 inches and a
wet season that can bring precipitation in exceeding 20 inches per month. Most places that have
this climate are found at the outer margins of the tropical zones. This type of climate, most
common in southern Asia and West Africa, results from the monsoon winds that change
direction according to the seasons. The dry season nearly always occurs at or soon after the
"winter" solstice for that side of the equator. This is due to the time of lower sun and shorter
days.
Tropical Wet or Rainforest
In the tropical rainforest subgroup, all twelve months have average precipitation of at least 4
inches. These climates usually occur within 5-10° latitude of the equator. In some eastern-coast
areas, they may extend to as much as 25° away from the equator. This climate is dominated by
low-pressure systems all year round, and therefore has no natural seasons. The temperature and
precipitation of these places does not vary from month to month resulting in uniform and
monotonous conditions. These conditions promote the growth of lush, green rainforest
vegetation. Tropical rainforests have a continuous canopy of trees, some reaching 200 feet or
taller. Within the rainforest canopy are trees of many different sizes, including pygmies, which
reach only a few feet.
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