A. Tropical humid Climate:

This type of climate is found in the low latitudes on each side of the equator in an irregular belt 20 to 40° wide. There is no winter season in this climatic group. Temperature is uniformly high throughout the year with adequate annual rainfall.

There is no occurrence of frost in any part of the year. In marine location the average temperature for the coldest month is 18° Celsius or above. This climatic group is subdivided into two climatic types which are as under:

Ar. Tropical wet climate:

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This type of climate is characterized by less than two dry months. This climatic belt extends out 5 to 10° on either side of the equator. Along the eastern or windward margins of a continent, the latitudinal extent may increase to 15° or 20°.

This type of climate is under the influence of inter-tropical convergence zone and the equatorial westerlies. This belt is distinguished by constant low pressure. It is also known as the tropical rainforest.

Aw. Tropical wet-and-dry climate:

At the time of the low sun, two months are dry. Annual average precipitation is less than that in Ar. During the winter season, Aw climatic regions are dominated by the dry trade winds or subtropical anticyclones.

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To the contrary, during the high sun period the equatorial westerlies and intertropical convergence control the weather.

The duration of dry season is longer than that of the wet season. Because of the occurrence of deciduous forest and tree-studded grasslands, Aw is often referred to as Savanna Climate. Temperature is uniformly high.

C. Subtropical Climate:

For 8 months, the temperatures are generally above 18° Celsius. The isotherm of 18° C for the coolest month forms the equator-ward boundary of C climate. Occasional frosts occur in its continental parts, but the marine locations are frostless.

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On the basis of the seasonal distribution of precipitation, C climates are divided into the following two climatic types:

Cfw. Subtropical humid climate:

This type of subtropical climate is found on the eastern side of continents. This climatic type has no distinct dry season. Rains fall throughout the year.

However, in summer this type of climate comes under the influence of unstable air in the western end of a subtropical anticyclone. But during winter it is influenced by the temperate cyclones. Summer months receive greater amount of precipitation than the winter months.

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Cs. Subtropical dry-summer climate:

This climatic type is characterized by moderate to scanty amount of precipitation. Here, winter is the rainy season, while summers are nearly or completely dry.

Located on the tropical margins of the middle latitudes along the western sides of the continents, Cs climate is affected by the stable eastern end of an oceanic sub-tropical high.

This climatic type represents a transition zone between the tropical dry climates equator-ward and the temperate climates pole-ward.

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D. Temperate Climate:

This climatic group is also known as the micro-thermal climatic type. Its pole-ward and equator-ward boundaries are formed by average temperatures of 10° Celsius for 4 and 8 months respectively.

This type of climate is found in the middle-latitudes between the subtropical and boreal climates. There are the following two types which are included in the temperate group of humid climates:

Do. Temperate marine climate:

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In this type of climate winters are mild. Average temperature for all the 12 months is 0° Celsius or above. It is found on the western windward side of the continents in the temperate zone. This is a humid climate with adequate precipitation at all seasons.

Dc. Temperate continental climate:

The temperate continental climate is found in the continental interiors or leeward areas of the middle-latitude continents. This type of climate is land-controlled. It is confined to the northern hemisphere with a latitudinal spread of about 10 to 20°.

This climatic type is characterized by severe winters and summers. Annual temperature ranges are, therefore, high throughout this climate. The 0°C isotherm for the coolest month forms the boundary between Dc and Do.

During winter the ground is covered with snow. Cold waves, heat waves, blizzards, and heavy downpours are all yearly events in this type of climate.

Rapid non-periodic changes in the weather are another characteristic feature of this climate. Precipitation occurs in all the months of the year with maximum concentration during the summer months.

E. Boreal Climate:

Boreal climate is found in the higher middle latitudes. It is super- continental in temperature features. The summers are short and cool. The winters are long and very cold with a very short frost-free season.

One to three months during the year have average temperatures of 10°C or above. Average temperatures for the rest of the year are below 10° Celsius. These regions are characterized by the lowest annual means of temperature for any part of the earth.

However, summer temperatures are still much higher than those experienced during the extremely cold winter months. Annual temperature ranges are usually large. Even though boreal climates are classified as humid, annual precipitation is generally meager.

Precipitation occurs throughout the year. However, most of the precipitation occurs during the warmer months when the amount of water vapour present in the air is highest.

Coniferous forest is the predominant natural vegetation. Because of the severity of climate, population in this type of climate is sparse. This group of climates is also called the sub-arctic type of climate.

F. Polar climates:

Polar climates are found in the high latitudes. These climates are confined to the northern hemisphere only.

The average temperature of no month exceeds 10° Celsius. There is no summer season. On the basis of temperature the Polar climates are classified into the following two climatic types.

Ft. Tundra climate:

The tundra climate on land is found only in the northern hemisphere, where it occupies the coastal fringes of the Arctic Ocean, and many Arctic islands and the ice- free shores of northern Iceland and southern Greenland.

There being complete absence of extensive land areas, no tundra climate is found in the southern hemisphere.

The equator-ward boundary of this climate is determined by the 10° Celsius summer isotherm. Tundra region is characterized by the absence of trees. It is essentially a region of grasses, mosses, and lichens.

The average temperature of the warmest month is recorded between 0° and 10° Celsius. Annual temperature ranges are small.

This is a region of permafrost where the subsoil is permanently frozen. Precipitation occurs throughout the year. However, the warmest season gets the maximum precipitation.

During summer the precipitation occurs partly as snow, and partly as rain. Because of low temperatures and anticyclones conditions, winter-time precipitation, which is entirely in the form of snowfall, is meager. Snowfall is usually dry and powdery.

Fi. Ice-cap Climate:

In ice-cap climate, the average temperature for all the months is below freezing. There is no vegetation of any kind. The landscape is one of permanent ice and snow.

This climatic type covers more than 15.5 million square kilometers or about one-tenth of the earth’s area Ice-cap climate is exclusively confined to the ice caps of Greenland and Antarctica.

Precipitation is meager, and falls as snow, most of which is in the form of dry, hard, sand like particles. The origin of precipitation is still not clear. However, there are numerous cyclonic storms that produce inland precipitation. Most of the snow falls along the seaward margins of the continent.

Since the air close to the ice-cap is intensely chilled, surface inversions are the common features of this climate.