Pariksha SaathiLesson 8 of 10 · Physical and World Geography
Climates and Natural Regions of the World: Koppen's Scheme, Vegetation and Peoples
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Koppen's classification
The most widely used scheme of world climates was devised by the German climatologist Wladimir Koppen, who kept revising it until 1936. It uses monthly temperature and rainfall, matched to vegetation. Its five main groups are A, tropical humid, where every month averages above 18 degrees Celsius; B, dry, where evaporation exceeds precipitation; C, warm temperate, with the coldest month between 18 and minus 3 degrees; D, cold snow-forest, with the coldest month below minus 3 degrees; and E, polar, where even the warmest month stays below 10 degrees. Small letters show the rainfall pattern: f for no dry season, m for monsoon, w for a dry winter and s for a dry summer, while BW is desert, BS steppe, ET tundra and EF ice cap. In India, Amw covers the west coast south of Goa, As the Coromandel coast of Tamil Nadu, BWhw extreme western Rajasthan and Cwg much of the Ganga plain.
Equatorial regions
The equatorial climate (Af) lies within about 10 degrees of the Equator in the Amazon and Congo basins, Malaysia and Indonesia. It is hot and wet all year, around 27 degrees Celsius with a very small annual range, and rain falls almost daily in afternoon convectional thunderstorms, often more than 200 cm a year. The natural vegetation is tropical evergreen rainforest, called selvas in the Amazon: tall, dense, layered forest of hardwoods such as mahogany, ebony and rosewood. Traditional peoples include the Pygmies of the Congo forests and the Semang of Malaysia. Shifting cultivation has many local names: roca in Brazil, milpa in Mexico and Central America, conuco in Venezuela, masole in Central Africa, ladang in Indonesia and Malaysia, ray in Vietnam and jhum in north-east India.
Monsoon and savanna regions
The tropical monsoon climate (Am) of South and South-East Asia and northern Australia has a seasonal reversal of winds, a hot, wet summer and a dry winter; its deciduous forests shed their leaves in the dry season and yield teak, sal and bamboo. The tropical savanna or Sudan climate (Aw) lies between the equatorial forests and the hot deserts, with a wet summer and a long dry winter. Tall grasses with scattered trees such as acacia and baobab cover the savannas of Africa, the llanos of the Orinoco basin in Venezuela, the campos of Brazil and northern Australia. The Maasai of Kenya and Tanzania herd cattle, and the Hausa of northern Nigeria farm and trade.
Hot and cold deserts
Hot deserts (BWh) lie mostly on the western sides of continents between about 15 and 30 degrees of latitude, where the subtropical high brings sinking dry air, the trade winds blow offshore and cold currents chill the coast. Rain is usually under 25 cm a year, and blazing days and cold nights give the largest daily range of temperature of any climate. The Sahara is the largest hot desert, followed by the Arabian; others are the Kalahari and Namib, the Thar, the Australian deserts and the Atacama, the driest. Xerophytic plants such as cacti and thorny bushes survive here, and date palms grow at oases. Peoples include the Bedouins of Arabia, the Tuaregs of the Sahara, the San (Bushmen) of the Kalahari and the Aborigines of Australia. Cold deserts, such as the Gobi, Patagonia and Ladakh, lie deep inside continents or in rain shadows.
Mediterranean regions
The Mediterranean climate (Cs) lies on the western margins of continents between about 30 and 45 degrees: around the Mediterranean Sea, in central California, central Chile, the Cape Town region of South Africa, and south-western and southern Australia around Perth and Adelaide. Its unique feature is rain in winter. Summers are hot and dry under the subtropical high, while in winter the pressure belts shift towards the Equator and the westerlies bring cyclonic rain. Evergreen trees such as the cork oak and olive grow here, and these orchard lands of the world produce citrus fruits, grapes, olives and figs.
Temperate grasslands
Low rainfall and extreme temperatures in mid-latitude continental interiors produce treeless grasslands: the steppes of Eurasia, the prairies of North America, the pampas of Argentina, the veld of South Africa, the downs of Australia and the Canterbury plains of New Zealand. Once grazed by bison and wild horses, they are now the great wheat lands and cattle ranches of the world, and the Kirghiz and Kazakhs traditionally herded animals on the Central Asian steppes.
Taiga and tundra
Roughly between 50 and 70 degrees north lies the taiga or Siberian climate, with long, bitterly cold winters and short, cool summers. Found only in the Northern Hemisphere, because the Southern Hemisphere has no broad land masses at these latitudes, it supports vast coniferous forests of pine, fir, spruce and larch. Farther north, along the Arctic Ocean, the tundra (ET) is a treeless land of mosses, lichens and dwarf shrubs over permanently frozen ground (permafrost). Its peoples include the Inuit (once called Eskimos) of Canada, Alaska and Greenland; the Sami (Lapps) of northern Scandinavia, who herd reindeer; and the Samoyeds and Chukchi of Siberia. The ice cap climate (EF) covers Antarctica and the interior of Greenland.
Key facts
- Koppen groups: A tropical (every month above 18 degrees C), B dry, C warm temperate, D cold snow-forest, E polar (warmest month below 10 degrees C); H highlands.
- Koppen small letters: f no dry season, m monsoon, w dry winter, s dry summer; BW desert, BS steppe, ET tundra, EF ice cap.
- India in Koppen's scheme: Amw west coast south of Goa, As Coromandel coast, Aw most of the peninsular plateau, BWhw western Rajasthan, Cwg Ganga plain.
- Equatorial (Af): about 27 degrees C all year, daily afternoon rain, over 200 cm; selvas of the Amazon; mahogany, ebony, rosewood; Pygmies of the Congo, Semang of Malaysia.
- Shifting cultivation names: roca (Brazil), milpa (Mexico), conuco (Venezuela), masole (Central Africa), ladang (Indonesia, Malaysia), ray (Vietnam), jhum (north-east India).
- Savanna: llanos (Venezuela), campos (Brazil), Serengeti (East Africa); acacia and baobab trees; Maasai herders (Kenya, Tanzania), Hausa farmers (Nigeria).
- Hot deserts on western margins at 15-30 degrees: Sahara, Arabian, Kalahari, Namib, Thar, Atacama; Bedouins (Arabia), Tuaregs (Sahara), San or Bushmen (Kalahari).
- Mediterranean (Cs): rain in winter, dry summer; Mediterranean basin, California, central Chile, Cape Town, Perth and Adelaide; olive, cork oak, citrus, grapes.
- Temperate grasslands: steppes (Eurasia), prairies (North America), pampas (Argentina), veld (South Africa), downs (Australia), Canterbury (New Zealand).
- Taiga: coniferous softwood forests, only in the Northern Hemisphere. Tundra: mosses, lichens, permafrost; Inuit (Canada, Alaska, Greenland), Sami or Lapps (Scandinavia), Samoyeds and Chukchi (Siberia).
Quick revision
Koppen: groups A, B, C, D, E plus H; letters f, m, w, s; Af equatorial, 27 C, over 200 cm, selvas, Pygmies; Am monsoon forests of teak and sal; Aw savanna, llanos, campos, Maasai; BWh hot deserts on western margins at 15-30 degrees, Bedouin, Tuareg, Bushmen; Cs Mediterranean winter rain, orchard lands; steppes, prairies, pampas, veld, downs; taiga conifers only in the north; tundra mosses and permafrost, Inuit, Sami; shifting cultivation roca, milpa, ladang, jhum.