CLIMATIC REGIONS

CLIMATIC REGIONS

 

Topics to be covered

  1. Equatorial Climate
  2. Tropical Monsoon Climate
  3. Tropical Marine Climate
  4. Desert Climate
  5. Tropical Savanna / Sudan Climate
  6. Warm Temperate / Mediterranean Climate
  7. Temperate Continental Grasslands / Steppe Climate
  8. Warm Temperate / China Climate / Natal Type / Gulf Type
  9. Cool Temperate Western Margin / British Climate
  10. Cool Temperate Eastern / Laurentian Climate
  11. Boreal Climate / Taiga Climate / Siberian Climate / Cool Temperate Continental Climate / Continental Sub-Polar Climate
  12. Tundra Climate / Polar Climate / Arctic Climate

 

 

Equatorial Climate

Distribution

  • Main regions are Amazon belt, Congo-Zaire basin, South-East Asia between 10º N-S.
  • Further away from equator, the influence of trade winds leads to monsoonal influences.

 

Temperature

  • Consistently high and uniform throughout the year with annual range of less than 2 ºC.
    • Even on highlands the annual range of temperature < 2ºC
  • Due to great heat in equatorial belts, mornings are brighter and sunny.

 

Rainfall

  • This region experiences convectional rainfall (4 pm rainfall) through cumulonimbus clouds which comes with a thunderstorm.
  • No month is without rain.
  • Rainfall has twin monthly peaks (equinoxes) – in March and September
    • Because the sun is directly overhead during these times and rainfall is convectional.
    • Rainfall is least on solstices.
  • As one goes north from the equatorial regions, the rainfall pattern starts to get disturbed by monsoon winds.
  • Not good for habitation due to hot and moist climate (High incidents of malaria and other tropical diseases).

 

Vegetation

  • Dense tropical rain forests (called selvas in Amazon) are found.
    • Trees compete for the sunlight because of the huge density and closeness.
    • Epiphytes
    • Forest is arranged in 3 canopy layers
    • Growing season is entire year.
    • No distinct season of seeding, flowering, shedding of leaves.
  • Many species of trees are intermixed, and hardwood logs sink in water so that commercial logging is not feasible.g. mahogany, ebony, dyewoods etc.
    • Cutting and transportation of the hardwood is a difficult task.
    • Many parts of the tropical rain forests have been cleared either for lumbering or shifting cultivation.
  • In the coastal areas and brackish swamps, mangrove forests

 

Epiphytes: They are plants that grow upon other plants non-parasitically. They usually derive only physical support and not nutrition from their host. They use photosynthesis for energy obtain moisture from the air or from dampness on the surface of their hosts.

 

Economic activities

  • Main crops are plantation crops like rubber (SE Asia), cocoa (W Africa – Ghana & Nigeria), coconuts, sugar, coffee, tobacco, spices, banana.
  • Belukar is the secondary forest growing as a result of shifting cultivation activities in Malaysia.
  • Agriculture and developmental activities are difficult because thick grass and undergrowth grows as soon as the forest is cut.

 

Tropical Monsoon Climate

Distribution

  • South and South-East Asia and North Australia.
    • Outside this zone the climate is modified by the onshore trade winds and rainfall is distributed more evenly throughout the year (tropical marine climate).

 

Temperature

  • It experiences warm to hot summers due to the region’s proximity to the tropics.
  • Average monthly temperature is above 18 ºC, but in summers the maximum temperature can reach as high as 45 ºC.
  • The average temperature in the summer is around 30 ºC, with an overall temperature range of 30-45 ºC.
  • Mean temperature during winters is around 25 ºC with temperature range of 15-30 ºC.

 

Seasons

Seasons are chief characteristics of monsoon climate.

  • Cool, dry winters (October – February).
  • Hot, dry summers (March – June).
  • Rainy season (June-September).
    • Orographic rainfall

 

The cool, dry season (October to February)

  • The North-East Monsoon (Out blowing dry winds) bring little or no rain to the Indian sub-continent.
    • However, a small amount of rain falls in Punjab from cyclonic sources (Western Disturbances)
  • North-East Monsoons blowing over the Bay of Bengal acquires moisture and bring rains to the south-eastern regions of Indian peninsula during Nov-Dec of the year.

 

 

The hot dry season (March to mid-June)

  • The sun’s northward shift to the Tropic of Cancer causes sharp rise in temperature.
  • Coastal districts are a little relieved by sea breezes and little rain.

 

The rainy season (mid-June to September)

  • Torrential downpours sweep across the country with the ‘burst’ of the South-West
  • Almost all the rain for the year falls within this rainy season (this concentrated heavy rainfall in summer is a chief characteristic of the Tropical Monsoon Climate).

 

Vegetation

  • Deciduous due to marked dry season during which leaves are shed.
  • Forests are generally logged but the vegetation differs with the rainfall.
  • Broad-leaved hardwood trees
  • The forests are more open and less luxuriantthan the equatorial region forest and there are far fewer species.

 

Economic activities

  • The region supports high population density.
  • Subsistence farming is the main occupation (crops grown with an intention to secure food for the season and not sold as the production is very low).
  • Intensive cultivation is common in regions with irrigational facilities.
  • Shifting cultivation is prevalent in North-East India and South-East countries.
  • Main crops are rice, sugar, jute (hemp in Manilla), cotton. Coffee is grown in Brazil. Tea requires modest temperatures (15 – 20ºC), heavy rainfall (150 cm) and well drained slopes.
  • Cattle and sheep rearing are carried out for domestic and commercial purposes, but livestock industry is not as profitable as in temperate regions.

 

Shifting cultivation

It is a‘slash and burn’ agriculture. Farmers clear a patch of land and produce cereals and other food crops to sustain their family. When the soil fertility decreases, the farmers shift and clear a fresh patch of land for cultivation. This type of shifting allows Nature to replenish the fertility of the soil through natural processes; land productivity in this type of agriculture is low as the farmer does not use fertilisers or other modern inputs. It is known by different names in different parts of the country.

 

RegionName of Shifting Cultivation
MalaysiaLacking
BurmaTaungya
ThailandTamrai
PhilippinesCaingin
JavaHumah
Sri LankaChena
Africa and Central AmericaMilpa
North-east IndiaJhum

 

 

Tropical Marine Climate

 

Distribution

  • Occurs on the eastern coasts in tropics under the influence of trade winds. Philippines, Central America, NE Australia, Madagascar, East Africa and East Brazil.

 

Rainfall

  • It is both orographic and convectional. It is maximum in summer season but without any distinct dry season.
  • It is prone to severe tropical storms and typhoons.

 

 

Desert Climate

Distribution

  • Areas having less than 25 cm of annual precipitation known as deserts (whether hot or cold).
  • Major hot deserts are located on the western side of tropics (i.e.  on 15º-30º latitude range of continent).

 

  • Hot desert
    • Aridity of hot deserts is mainly due to offshore trade winds.
    • Lie in the horse latitude belt where the air is subsiding – a condition least favorable to precipitation. Further winds blow from cooler to hotter regions, hence the lack of water content.

 

  • Cold deserts
    • Aridity of cold deserts is because of offshore westerlies or leeward side effects.
    • Cold deserts are also generally located on high plateaus.
    • Atacama/Peruvian desert (driest place on earth) is the driest of all deserts (< 1.25 cm p.a.).
  • Cold currents have the effect of cooling the air. When this comes in contact with the hot air on the land mass, relative humidity drops further.

 

 Rainfall

  • Whatever occurs, occurs mostly because of convectional rainfall and with thunderstorms.
  • In cold deserts in Asia, whatever rainfall happens occurs because of occasional western disturbances and in form of snow.

 

Temperature

  • Temperature is high throughout the year (due to clear cloudless sky, intense insolation, high rate of evaporation). No winter.
  • Average temperature is around 30-35°C.
  • Diurnal and annual range is high.
  • Coastal deserts generally have less temperature than interiors due to cold currents. Ranges are also high in interiors.
  • Annual range of temperature is higher in cold deserts compared to hot deserts (because they are mostly located in mid-latitudes where variation in insolation is highest and because they are located deep inside continents)

 

Vegetation

  • Vegetation is xerophytes / drought resistant scrubs (like cactus)
  • Shrubs remain dormant for years waiting for rainfall. They also have long roots, modified leaves and stems. Seeds have thick tough skins and lie dormant until it rains.
  • High evaporation means salts are brought upwards and they accumulate on the surface forming hard pans. Soil is also deficient in humus.

 

Minerals

  • Gold is mined in Australia, diamonds and copper in Kalahari Desert, copper and nitrates in Atacama Desert.

 

 

Tropical Savanna / Sudan Climate

Distribution

  • It is found between equatorial forests and the trade wind hot deserts.
  • The grasses are called llanos in Orinoco basin and campos in Brazil.

 

Seasons

  • Distinct wet and dry season with extreme diurnal range of temperature.
    • Hot, rainy season (May-September in Northern hemisphere, October-March in Southern hemisphere).
    • The amount of rainfall and the length of the rainy season decreases from equator to pole-wards towards the desert fringes.
    • Trade winds bring rains to the eastern coasts but become dry by the time they reach interiors of the continents.
  • Cool, dry season.
  • Annual range of temperature is about 10ºC and the range increases as we move polewards.
    • Highest temperatures don’t coincide with period of highest sun but fall just below the onset of rains.
  • These conditions are best developed in Sudan hence it is called Sudan type of climate.

 

Local Winds

Harmattan (the doctor) are the north east trades which blow from interior Africa to the Atlantic coast in Guinea. They come from deserts and humidity rarely exceeds 30%. It is called the doctor because it gives relief from moist sea winds.

 

Vegetation

  • Tall savanna grasses (elephant grass). Grasses have deep roots. It lays dormant during cool, dry season.
  • Trees decrease in height and density polewards.
  • Some trees are deciduous shedding their leaves in cool, dry season to prevent water loss.
  • Some trees have broad trunks with water storing devices (like Acacia tree).
  • Many trees are umbrella shaped exposing only a narrow edge to the winds.
  • Heavy rainfall in hot, wet season lead to intense leaching of the soil and all the nutrients are washed away.
  • Domestication of animals is popular in Australia.
  • Grass fire occurs during dry season that also burn the seeds of trees which are ready to germinate.

 

Animal Life of the Savanna

  • The savanna is the home large variety of animals and known as the ‘big game country’ due to the prevalence of hunting.
  • There are mainly two groups of animals in the savanna, one is the grass-eating herbivorous animals and second is the fleshing-eating carnivorous animals.
    • Herbivorous = zebra, antelope, giraffe, deer, gazelle, elephant etc.
    • Carnivorous = lion, tiger, leopard, hyena, panther, jaguar, jackal etc.

 

Warm Temperate / Mediterranean Climate

Distribution

  • It is confined between 30 – 45º latitudes on the western margins of the continents.
  • It is caused by shifting of pressure belts and comes under the effect of trade winds during summers (continental trades and hence dry) and westerlies during winters (onshore winds and hence wet).

 

Temperature

  • Highest temperatures are experienced as we move inland away from maritime influence.
  • Climate is not extremebecause of cooling effect by water bodies.

 

Rainfall

  • Cyclonic rainfall is prevalent from westerlies. The rain comes as heavy showers and only on few days with bright sunny intervening days.
  • The region experiences dry warm summers and wet cold winter.

 

Dry, warm summers with offshore Tradewinds:

  • The sun is overhead the Tropic of Cancer and Tropic of Capricorn during the summer months.
  • The belt of influence of the Westerlies is shifted a little polewards. Rain bearing winds are therefore not likely to reach the Mediterranean lands.
  • Hence the regions are practically rainless in summers and remain dry.
  • The heat is intense, and the days are excessively warm.
  • In the interiors, prolonged droughts are common. The relative humidity is generally low.

 

Wet, cold winters with on-shore Westerlies:

  • The Westerlies belt shifts equator ward in the winter and the Mediterranean regions are under the influence of on-shore Westerlies.
  • Hence, these lands receive almost all of their precipitation during the winter months.
  • The rain comes in heavy downpours and causes floods in the months of September and October in Mediterranean Europe.

 

Local Winds

  • Sirocco: They are the south-westerlies blowing from Sahara Desert into the mediterranean climate. They are hot and dry and remain dry even after passing above Mediterranean Sea. It is most frequent during spring and is bad for crops.
  • Mistral: It is a cold wind from north in Alps region which rushes down in winter into the valleys to fill the low pressure towards the sea.It is fast and may take the temperature below the freezing point.
  • Bora: In the Adriatic coast, the cold winds blowing from the continent to the sea in winters are called Bora. They are very fast.

 

Vegetation

  • Mediterranean evergreen forests: They are found in regions of high rainfall. Cork oak trees are common in Europe while eucalyptus are grown in Australia.
  • Evergreen coniferous forests: They are found in highlands.
  • Mediterranean shrubs: They are the dominant vegetation.
  • Orchard farming: Fruit trees have long roots enabling them to fetch water in hot summer season as well. The thick leathery skin of the fruits also prevents transpiration.

 

Agriculture

  • Summer is dry hence monsoon crops are not grown.
  • This region is not suitable for agriculture, but some regions do cultivate using irrigation methods.
  • Citrus fruits are mostly grown and viticulture (wine making) is mostly done here.

 

Temperate Continental Grasslands / Steppe Climate

 

Name of the Temperate GrasslandRegion
PustazHungary and surrounding regions
PrairiesNorth America (between the foothills of the Rockies and the Great Lakes)
PampasArgentina and Uruguay (Rain-shadow effect)]
Bush-veld (more tropical)Northern South Africa
High Veld (more temperate)Southern South Africa
DownsAustralia (Murray-Darling basin of southern Australia)
CanterburyNew Zealand

 

Distribution (30° – 45°)

  • They border the deserts and lie in the interiors of the continents in Northern hemisphere and near the oceans in Southern hemisphere. Though they lie in the westerly belt, they are far removed from the maritime influence.
  • Mostly they are grassland / treeless because of absence of maritime influence. They are extensive in northern hemisphere.
  • Grasslands in Southern hemisphere are less continental due to proximity to oceans. They have less extreme temperatures (milder winters and less annual range) and rainfall is higher as well.

 

Temperature (Continental Climate)

  • Warm summers and cold winters. Extreme variation of temperature.
  • Wetter and cooler than Savannah.
  • Annual range is very high in northern hemisphere.
  • Southern hemisphere climate is never severe (effect of ocean).

 

Rainfall

  • Annual precipitation (conventional sources) is light with maximum rainfall in summers. Winters get occasional rains from western disturbances and in the form of snow.
  • Annual precipitation is higher in Southern hemisphere due to proximity to ocean and warm ocean currents.

 

Local Winds

  • Chinooks: They are south-westerly winds pulled over from the Rockies. They are hot winds and can raise the temperatures by 20º C in 20 minutes.

 

Vegetation

  • Nutritious grasses (No trees).
  • Complete grasslands are converted into agricultural lands.
    • Truck farming is done (mostly in prairies).
  • Heavily mechanised farming (Aeroplane used for dropping fertilizers).
  • Per person productivity is high, per acre productivity is low (because of absence of intense farming).
  • The grasses lie dormant in the winters and become active in the spring when the temperature is hot enough. In summers they get scorched but in autumn they grow again.
  • Polewards, an increase in precipitation gives way to coniferous trees while equatorward they merge with desert shrubs.

 

Economic Development

  • Prairies would have wheat, cotton, maize cultivation
  • Steppes are one of the major producers of wheat
  • Pampas region would have wheat cultivation, animal husbandry livestock ranching (alfa-alfa a nutritious grass is found here).
  • Downs of Australia would have sheep rearing (Marino sheep famous for wool).
  • Veldts are famous for sheep rearing (agora goat is famous for wool production).

 

Warm Temperate / China Climate / Natal Type / Gulf Type

DistributionEastern margin in warm temperate zone (30°- 45°)

  • China type
    • East and central China.
    • Rainfall throughout the year.
    • Trade winds take the warm current moist air inside and causes rain in summers. Typhoons are carried in by the trades in late summers.
    • In winters, however there is a reversal of wind direction due to cooling of Asian land mass and temperatures plummet (rain through moisture gain by Siberian plateau wind while passing yellow). So annual range of temperature is high.

 

  • Gulf type
    • SE USA, Gulf of Maxico.
    • The monsoonal characteristics are less here as the pressure gradient between continental North America and the Atlantic Ocean is never high enough to reverse the wind direction completely.
    • Rainfall in summer is maximum.
    • In winter season this type will experience temperate cyclone while in late summers they experience tropical cyclones (hurricane).

 

  • Natal type
    • In southern hemisphere like South Africa (Natal province), Eastern Australia, Southern Brazil.
    • These lands have no monsoonal climate due to thinness of the land masses which is not sufficient to cause any wind change.
    • More dominance of maritime climate. So annual range of temperature is less, rainfall is more and distributed throughout the year.

 

Rainfall & Temperature

  • It has more rainfall than Mediterranean climates for same latitude because of influence of warm currents. They are under the influence of trade winds.
  • Summers are warm and winters are cool. Rainfall varies from 60-150 cm.

 

Natural Vegetation

  • The region supports luxurious vegetation due to heavier rainfall.
  • There are perennial plants, a well-suited condition for the rich variety of plant life.
  • The lowlands carry both evergreen broad-leaved forests and deciduous trees, like tropical monsoon forests.
  • The highlands carry various important softwoods species of conifers such as pines and cypresses.
  • Eastern Australia = Eucalyptus
  • South-Eastern Brazil, eastern Paraguay, north-eastern Argentina = Parana pine, the quebracho, wild yerba mate trees.
  • Natal = palm trees

 

Economic Development

  • These regions are the most productive part of the middle latitudes due to the adequate rainfall; no prolonged drought and the cold season is warm.
  • This shows almost continuous growing season.
  • The temperate monsoon regions are the most intensively tilled parts of the world.

 

Agriculture Development

CountryEconomic Activity
ChinaRice, Tea, Cotton, Maize, Mulberry
NatalSugarcane
South AmericaCoffee and Maize
USAMaize Region- Cotton- Tobacco (Virginia Tobacco)

 

Cool Temperate Western Margin / British Climate

Distribution

  • Located to the western margin in cool temperate zone (45°-65°) North and South.
  • They are under the influence of westerlies all through the year, but westerly influence is blocked by Rockies and Andes in N and S America, respectively.
  • Britain, Northern France, Northern Germany, Norway, Western Canada (Vancouver provinces) Tasmania and New Zealand, Southern Chile.
  • British type will experience four seasons.

 

Temperature &Precipitation

  • Cool moderate climate.
  • Low annual range of temperature. Moderate temperature best suited for human habitation. Summers are never very warm.
  • Rainfall is throughout the year with winter or autumn maximum because of cyclonic conditions.
    • Rainfall from westerlies in summer.
    • Western coast receives most rainfall and rain decreases towards interior.
  • Temperature have much oceanic influence, mostly warm ocean currents

 

Natural Vegetation

  • Deciduous forests are found, and they shed their leaves in autumn to prepare for the cold season.
  • Tall trees with good canopy cover, mostly give softwood.
  • Trees are social species and are in pure stand, multiple species are not found (hence commercially viable).
  • Example – Oak, Birch, Beech, Elm

 

Economic activities

  • Lumbering (cutting of trees for commercial purpose) in systematic way. Winter cutting is done where they would make wood logs float on frozen river.
  • Market gardening is a type of agricultural practice.

 

Cool Temperate Eastern / Laurentian Climate

Distribution

  • It is the intermediate types and has both maritime and continental traits.
  • It is extended in cool temperate eastern margin (45°-65°) of northern hemisphere.
  • It extends in eastern Canada (Newfoundland), North-East USA (new England states) regions, Korea, Northern Japan present beyond 40° latitude).
  • It also extends in Eastern Siberia, North china, Manchurian regions.
  • In southern hemisphere this climatic type is absent (land is not present beyond 40°latitude).

 

Rainfall and Temperature

  • Winters are cold and dry while summers are warm and wet. Summers would be warmer but for the cold continental winds.
  • Rainfall throughout the year.
    • In summer, westerlies bring rain fall in North America region because they catch moisture from great lakes. In winter, gulf stream increases moisture content which results in rainfall from polar easterly wind.
    • In china, we have summer maximum rainfall because of intense heating of land leading winds penetration come from pacific (south-east monsoon). In winter, anti cyclonic conditions in central Asia exists hence cold wind blows out and create some rainfall (Borrowing moisture from Yellow Sea).

 

Natural Vegetation

  • Mixed forestry (coniferous and deciduous).
    • Deciduous would spread below 50° latitude, Coniferous would spread above 50° latitude.
  • Oak, birch beech maple are principle trees.
  • Agriculture: potatoes, oats, barley, soya beans (mostly china) are grown.
  • Nova Scotia of Canada is famous for apple farming.

 

Economic activities

  • Lumbering and its associated timber, paper and pulp industries are the most important economic activity.
  • Fishing is also an important economic activity.
  • Agriculture is less important because of long and severe winters.
  • Farmers are engaged in dairy farming in the North American region.

 

Boreal Climate / Taiga Climate / Siberian Climate / Cool Temperate Continental Climate / Continental Sub-Polar Climate

Distribution

  • It has tundra towards the north and steppes towards the south. Taiga is the Russian name.
  • It stretches along a continuous belt across central Canada, some parts of Scandinavian Europe and most of central and southern Russian (50° to 70° N).
  • Found only in the northern hemisphere (due to great east-west extent).
  • Absent in the southern hemisphere (Because of the narrowness in the high latitudes. Also, the strong oceanic influence reduces the severity of the winter).

 

Temperature

  • Summers are brief and warm reaching whereas winters are long and brutally cold.
  • Annual temperature range of the Siberian Climate is the greatest (Almost 50-60 °C in Siberia).
  • In North America, the extremes are less severe, because of the continent’s lesser east-west stretch.
  • Occasionally cold, northerly polar local winds such as the Blizzards of Canada and Buran of Eurasia blow violently.
  • Permafrosts (a thick subsurface layer of soil that remains below freezing point throughout the year) are generally absent as snow is a poor conductor of heat and protects the ground from the severe cold above.

 

Precipitation

  • Rainfall annually is not high as maritime influence in the interiors is absent.
  • Frontal disturbances might occur in winter.
  • It is quite well distributed throughout the year, with a summer maximum (convectional rain in mid-summer – 15 °C to 24 °C).
  • In winter, the precipitation is in the form of snow as mean temperatures are well below freezing all the time.

 

Natural Vegetation

  • The predominant type of vegetation is evergreen coniferous forest.
  • The conifers are best suited to this type of sub-Arctic climate as they require little moisture
    • Juniper, spruce, fir, pine are example species of coniferous
  • The greatest single band of the coniferous forest is the taiga(a Russian word for coniferous forest) in Siberia.
  • These coniferous belts are rich source of softwood (used in furniture, construction, paper making industries).

 

 

Tundra Climate / Polar Climate / Arctic Climate

Distribution

  • Found in regions north of the Arctic Circle and south of Antarctic Circle.
  • The icecaps are confined to highlands and high latitude regions of Greenland and Antarctica.
  • In the southern hemisphere, Antarctica is the greatest single stretch of ice-cap.
  • The lowlands – coastal strip of Greenland, the barren grounds of northern Canada and Alaska and the Arctic seaboard of Eurasia, have tundra climate.

 

Temperature

  • The tundra climate is characterized by a very low mean annual temperature (most of the year below freezing point).
    • Temperatures are as low as 40-50 °C below freezing in mid-winter whereas summers are relatively warmer.

 

Precipitation

  • Precipitation is mainly in the form of snow and sleet.
  • Frequent blizzards reaching a velocity of 130 miles an hour.
  • Convectional rainfall is generally absent.

 

Natural Vegetation

  • There are no trees in the tundra.
  • Lowest form of vegetation like mosses, lichens etc. are found in patches.
  • Climatic conditions along the coastal lowlands are a little favorable.
  • Coastal lowlands support hardy grasses and the reindeer moss which provide the only pasturage for reindeers.
  • Berry-bearing bushes and Arctic flowers bloom in the brief summer.
  • In the summer, Birds migrate north to prey on the numerous insects which emerge when the snow thaws.
  • ResidingMammals = Wolves, foxes, muskox, Arctic hare and lemmings.
  • Penguins live only in Antarctic

 

Human Activities

  • People live a semi-nomadic life and largely confined to the coast.
  • In Greenland, northern Canada and Alaska live the sEskimos.
  • During winter they live in igloos.
  • Fish, seals, walruses, and polar bears are their major food.