Earth Climate

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Earth Climate

The average weather conditions over a large area is called the climate of a place. Weather conditions over a specific length of time, usually a period of 31 years, are taken into consideration.

On a large scale, the climate of a particular region is determined by:

i. Latitude and tilt of the earth’s axis, which determines the amount of solar radiation received by the area

ii. The distribution of land and sea and proximity of ocean currents

iii. The altitude and topography of the area

iv. The location of the area in relation to the main circulation belts of the earth.

Climate can be classified on the basis of temperature, rainfall, evaporation, evapotranspiration and water balance. One of the universally accepted climate classifications is by Koeppen which is being described here.

Types of Climates

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1. Tropical Rain Forest Climate

  • Also called equatorial type of climate or Selvas.
  • 5° – 10° of equator, nights and days equal.
  • Average monthly temperature is 24° – 27°c, annual range least. Diurnal range of temperature far greater than the annual range. Here night is the winter.
  • Called ‘Belt of Calm’ or Doldrums.
  • Convectional rainfall. Annual rainfall is 250 cm.
  • Broad-leaved evergreen dense forests. Trees are gregarious and there is competition for sunlight. Have more species of plants and animals than in all others combined.
  • In Amazon basin, Congo basin, Indonesia.

2. Tropical Monsoon Climate

  • Complete seasonal reversal of winds.
  • Rainfall seasonal (generally in summers). Due to this vegetation is deciduous.
  • Approx. 200 cm of rainfall.
  • Occurs in Western Guinea coast of Africa, South-Eastern Asia, Northern Australia, some parts of Amazon valley and West Indies.

3. Tropical Grasslands/Savanna Climate

  • Average annual temperature is 23°c. Annual rainfall is about 150 cm. Area- Africa, East and Central South America.
  • Bounded by tropical rain forest climate towards the equator and dry climate towards the poles, the Savannah type is characteristic of grasslands in tropical and subtropical latitudes. Grasslands are dotted with scattered trees and bushes that can survive the drought season.
  • Rainfall in summer owing to convectional ascent of air. Distinct dry season in winter. Trees with longer roots, fire-resistant.

4. Tropical-Subtropical hot Desert

  • Situated in the trade wind belt. Occupy the western margins of continents. The area includes North America – Colorado Desert, Mexican Desert; Africa-Sahara, Kalahari, Namib Desert; S W.Asia-Arabian, Iranian, Thar Desert; S.America-Atacama; Australia-Great Australian Desert.
  • Average annual temperature is 38° c; annual summer temperature is 40° c, annual winter temperature is 15° c. average annual rainfall is about 25-40 cm. Greatest diurnal temperature.
  • Highest insolation, as there is no clouds cover to scatter the insolation.
  • Vegetation is xerophytic.

5. Middle Latitude Desert Climate

  • Found between 35°-50° N and S.
  • Area: Tarim, Gobi, Russian Turkistan and C. Iran. In Southern Hemisphere, only in Patagonia.
  • Unlike the hot deserts, they have very cold winters because of their interior location.

6. Tropical and Subtropical Steppes

  • Transition belt between hot deserts and humid climates. Occupy pole-ward margins of the tropical and subtropical deserts.
  • Average annual temperature is 21° c.
  • Semi-arid climate characterized by abundance of shrubs and grasses.
  • Known by different names:
  • Prairies – North America
  • Pampas – South America
  • Veldt – South Africa
  • Downs – Australia
  • Steppes – Eurasia
  • Canterbury – New Zealand
  • Postaz – Hungary
  • Manchurian – Russia

7. Mediterranean Climate

  • In the western coast of continents between 30°-45° N & S; Around the Mediterranean Sea, in South Europe, North Africa, California coast, Central Chile, Cape of Good Hope and South East Australia.
  • Characterized by dry summer and humid winter. Off-shore trade winds blow in summer; they are dry and give no rainfall. Cyclonic rainfall in winter.
  • Average annual temperature is 16° c. average winter temperature, 10° c, summer 25°c annual rainfall is 40-60 cm.
  • Olives, grapevine and citrus family fruits are the chief products of these regions which are also known for grain farming.

8. China Type Climate

  • Average annual temperature is 19° c, annual rainfall 120 cm.
  • In the eastern coasts of continents between 25°- 45° N & S. Areas- China, South East USA, South Brazil, Eastern Argentina, South East Africa, South East Australia, South Japan. It is the eastern counterpart of the Mediterranean type.
  • Characteristics-Hot summers and mild winters. Rainfall throughout the year.

9. West European Type Climate

  • On the western side of continents between 40°-65° N & S. Areas- North West Europe including British Isles, West coat of Canada, South Chile, Southern New Zealand.
  • Summers are moderate to cool (15°-18°); winters mild (2°-10°). Average annual temperature is 10° c.
  • Annual Rainfall: 75-100 cm. No dry season as the westerly winds blow from the ocean throughout the year. Rainfall is mostly of cyclonic origin.

10. Cool East Coast Climate

  • The Corn Belt of US has this type of climate; that is why it is known as ‘Corn-Belt’ climate.
  • Average summer temp is 21°-24°c; it is long, warm and humid.
  • Winter temp average-4° to 1.7° for a period of 3-5 months.

11. Continental Type Climate

  • Coldest winter month average -12° to -6.7°c.
  • Hottest summer months average 18°c to 21°c.
  • In the interior parts of big continents.

12. Taiga Climate

  • Taiga means snow forests or coniferous forests; needle shaped leaves, composed of evergreen spruce, fir and pine. Extends in two large belts in east-west direction from Alaska to Newfoundland in North America and from Norway to Kamchatka Peninsula in Eurasia.
  • Cool and short summers (around 10°c) and very cold and long winters (below 0°c).
  • Annual range of temperature highest. (In Verkhoyansk, Jan temp is -50°, annual range being 64°c)
  • Total annual precipitation below 50 cm.
  • These forests are the most important source of softwood and fur bearing animals.

13. Tundra Climate

  • Summers are warm enough to melt the thin snow cover or small water bodies, with the result that land is water soaked and marshes, swamps are common.
  • Precipitation less than 30 cm.
  • Blizzards blow.
  • Lichens and mosses common.

14. Highland Climate

  • Experienced in the mountainous regions.
  • Determined by elevation, shape of the highland, exposure to winds and location.
  • Here winds are much stronger than at low levels.
  • Vegetation varies as we move up.

Important Deserts of the World:

  • Sahara – N. Africa (Includes the Libyan and the Nubian Desert)
  • Australian – Australia (Includes Gibson, Simpson, Victorian, Great Sandy)
  • Arabian – Arab Countries (Includes Rub’al Khali & An-Nafad of S. Arabia and Dast-e-Lut & Dast-e-Kavir of Iran)
  • Kalahari – Africa (mainly in Botswana)
  • Gobi – Mongolia
  • Atacama – Central Chile
  • Patagonian – Argentina
  • Nabib – Namibia
  • TaklaMakan – Sinkiang, China
  • Karakum – Turkmenistan
  • Sonoran – Arizona and California (USA)
  • Thar – India

Isopleth

  • Lines drawn on map along which the value of a particular phenomenon is uniform.

Some Important Isopleths are:

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