Dry Climates

As the name indicates, dry climates are characterised by low rainfall which is not suit for the growth of plants. These climates cover vast areas extending from 15° to 60° north and south of equator. The climates of this group are divided into following four types.

Subtropical Steppe (BSh). is is low latitude semi-arid climate. Average annual temperature is more than 18°C and rainfall is adequate enough for the growth of sparse grass. Rainfall is variable and famines occur frequently.

Subtropical desert (BWh). is is low latitude arid or dry climate in which mean annual temperature is above 18°C. Rainfall is less than that in the subtropical steppe and is highly variable. It occurs in short intense thunder showers and is unable to build soil moisture. Both the above-mentioned climates have many things in common although their degree varies. ese include hightemperaturess1, low and variable rainfall and frequent famines.

Fog is common in coastal deserts bordering cold currents. Maximum temperature in the summer is very high. The highest shade temperature of 58°C was recorded at Al Aziziyah, Libya on 13 September 1922. The annual and diurnal ranges of temperature are also high.

Mid-latitude semi-arid (BSk). This is mid latitude cold steppe climate in which rainfall is scanty and mean annual temperature is below 18°C.

Mid-latitude arid (BWk). is climate in mid latitude cold areas is marked by rainfall less than in mid-latitude steppe climate but the mean annual temperature here also is less than 18°C.

C—Warm Temperate (Mid-latitude) Climates

Climates of this category extend from 30° to 50° latitudes and are conned mainly on the eastern and western margi ns of the continents. Warm summers and mild winters are the chief characteristics of these climates. ese climates ar e grouped into following three types.

Humid Subtropical Climate (Cfa). is climate occurs in subtropical latitudes on the eastern parts of the continents. Large areas of eastern U.S.A., southern and eastern China, southern Japan, northeastern Argentina, coastal south Africa, and eastern coast Australia have this type of climate. In these areas, the airmasses are generally unstable and cause rainfall throughout the year. The annual average rainfall varies from 75 to 150 cm. understorms in summer and frontal precipitation in winter are common. Mean monthly temperature in summer is around 27°C, and in winter it varies from 5°C–12°C. The daily range of temperature is small.

Mediterranean Climate (Cs). As the name suggests, Mediterranean climate occurs around Mediterranean Sea, along the west coast of continents in subtropical latitudes between 30–40° latitudes e.g.—Central California, Central Chile, along the coast in south eastern and south western Australia. These areas come under the inuence of sub tropical high in summer and westerly wind in winter. Hence, the climate is characterised by hot, dry summer and mild, rainy winter. Monthly average temperature in summer is around 25°C and in winter it is below 10°C. The annual precipitation ranges between 35—90 cm.

Marine West Coast Climate (Cfb). Marine west coast climate is located poleward from the Miditerranean climate on the west coasts of the continents. The main areas are: Northwestern Europe, west coast of North America, north of California, southern Chile, southeastern Australia and New Zealand. Due to marine inuence, the temperature is moderate and in winter, it is warmer than for its latitude. The mean temperature in summer and winter months ranges from 15–20°C and in winter 4–10°C respectively. The annual and daily ranges of temperature are small. Precipitation occurs throughout the year. Precipitation varies greatly from 50 to 250cm.

D—Cold Snow Forest Climates

These climates occur over large areas in continents of the northern hemisphere between 40° and 70° northern latitudes. Large parts of Europe, Asia and North America experience this type of climate. Cold snow forest climates are of the following two types:

Cold Climate with Humid Winters (Df).

This climate is found in areas located poleward of marine west coast climate and mid latitude steppe. Winters are cold and snowfall in winter is a common phenomenon. Frost free season is short and the annual range of temperature is large. Weather changes abruptly but the change is short lived. Winters become more severe as we move towards the north pole.

Cold Climate with Dry Winters (Dw). Northeastern Asia is the main area of cold climate with dry winters. This climate is marked by anticyclonic conditions in winter which weakens in summer. Summer temperatures are lower towards the pole and winter temperatures are extremely low. Several places have temperature below freezing point for more than half of the year. This climate is characterised by very low rainfall of 12–15 cm, most of which is received in summer.

E—Polar Climates (E)

These climates are found in polar areas beyond 70° latitude and have the following two distinct types.

Tundra Climate (ET). is climate is characterised by permafrost where such soil is permanently frozen. The growing season is very short and water logging is common. These two conditions support only low growing plants like mosses, lichens and wering plants. Duration of day light is very long during the summer season but almost completely absent during the winter season.

Ice Cap Climate (EF). is is a very cold climate in which even summer temperature are below freezing point. Such climate occurs in interior of Greenland and Antarctica. Precipitation is very low and occurs in the form of snow. The snow and ice get accumulated and the mounting pressure causes the deformation of the ice sheets and they break. They move as icebe rgs that oat in the Arctic and Antarctic waters. ‘Plateau Station’ in Antarctica at 79° S, portray this climate.

H—Highland Climates (H)

As the name indicates, highland climates occur in high mountainous regions and are governed by topography. The temperature falls with altitude and there are large spatial variations in temperature and rainfall. There is vertical zonation of layering of climate types with elevation in the mountain environment.


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