The world has several climatic zones. These are summarized on the map below.
1. Tropical Moist Climates (Af)
– This climate is located upto 50 to 100 latitudes on both the hemispheres.
– The zone is subjected to seasonal shifting due to northward and southward movement of Sun.
– The tropical climate is characterized by two major properties – uniformly high temperature throughout the year and uniformly adequate rainfall throughout the year by convectional rainfall. The total annual rainfall is often more than 250 cm.
– Humidity is between 77 and 88%.
– The equatorial climate is found in – The Amazon Basin in South America, Congo Basin in Africa, Guinea coast in Africa, Java, Sumatra, Malaysia etc.
– The climates on eastern sides of continents are influenced by maritime tropical air masses. These air masses flow out from the moist western sides of oceanic high-pressure cells, and bring lots of summer rainfall. The summers are warm and very humid. It also rains a lot in the winter.
– This region accounts for the largest number of plant species due to high temperature and high rainfall.
– This climatic region is characterized by broad leaf evergreen dense forests comprising mahogany, rosewood, bamboos, sandal etc.
2. Wet-Dry Tropical Climates (Aw) savanna
– This type of climate is located between 50 – 200 latitudes on either side of the equator.
– This climatic type is bounded by tropical rainforest climate towards the equator and by dry climate towards the poles.
– The Savanna type is found in the southern continents and all the regions are to the south of the Tropic of Cancer.
These are –
a) South America: Cuba, Jamaica and the islands in the Pacific.
b) Africa: The Sudan, large parts of the newly formed Republics – Senegal, Guinea, Mali, Niger, Chad and also in Ghana, Togo, Kenya, Zimbabwe, Tanzania, Angola and Uganda.
c) Australia: The northern region and Queensland.
– The Savanna climate is characterized by distinct wet and dry seasons, mean high temperature throughout the year and high insolation.
– There is sunshine for 13 to 14 hours and humidity is low, the air is hot, dry and dusty.
– The average monthly temperature during the dry season ranges between 22°C and 37°C.
– Coastal regions on the windward side of the mountains get heavier rain. Rainfall decreases as one goes either towards north (in the Northern Hemisphere) or towards south (in the Southern Hemisphere).
– The Savanna vegetation marks the transition from the dense equatorial forests, where the rainy season lasts practically throughout the year, and the semi-desert and deserts where the dry season lasts practically throughout the year.
– The seasonal rain allows only grass to grow. These are therefore the natural grasslands of the world. Rainfall is not sufficient to support tall trees but grass grows well and one variety known as the elephant grass grows up to four and a half metres.
– Trees occur more as one goes towards the Equator.
3. Hot Desert Climate
– This type of climate is located between the latitudinal belt of 150 – 300 in both the hemispheres.
– The arid deserts lie close to the Tropic of Cancer and Tropic of Capricorn in the western margins of continents.
– The climatic zone lies in – The Sahara, the Arabia, the Thar, Mohave and Sonoran (South Western U.S.A.), Kalahari and Namib (South Western Africa), Simpson, Gibson, Great Sandy (Australia)
– The climate is dominated by the subsidence of air masses and marked stability of the sub-tropical anticyclones and hence nearly rainless. The highest temperatures in the world are recorded here (Azazia 58.7°C). The greatest daily ranges of temperature of (15°C) are seen here.
– These areas receive the lowest annual rainfall (12 to 15 cm). Cold currents also influence the climate on the western margins of continents. The aridity is intensified because of these currents which chill the air and further stabilize it.
– The vegetation found here is cactus, thorny plants, shrubs, herbs.
4. Steppe Climate
– This type of climatic zone is found between 40° and 55° North and South. They lie far away from the influence of the sea, in the heart of continents.
– The areas are – Prairies (North America), Pampas (South America), Velds (South Africa), Downs (Australia) and Steppes (Russia)
– The temperature in summer varies from 18°C to 24°C and in winter from – 4°C to 2°C. The range of temperature is large. Rainfalls in spring and early summer and vary between 23 cm. and 65 cm. It is of convectional type but very light.
– This dry climate exists in the interior regions of the North American and Eurasian continents. Moist ocean air masses are blocked by mountain ranges to the west and south. These mountain ranges also trap polar air in winter, making winters very cold. Summers are warm to hot.
– Short grass grows everywhere. Trees appear only on the slopes of mountains.
5. Monsoon Climate
– Monsoon climate is generally related to those areas which register complete seasonal reversal of wind direction and are associated with tropical deciduous forests. The region lies between 10°N to 30°N and 10°S to 30°S latitude.
– Climatic zone areas are – Eastern Brazil (S. America), Central American countries, Natal coast (South Africa), India, Pakistan and Bangladesh, South East Asia including Burma, Thailand, Vietnam and the Philippines etc., Parts of East Africa including Malagasy, North Australia.
– The annual average temperature is about 26°C and the annual range is about 3°C. The maximum temperatures occur in May before the summer rainfall maximum in June and July. The annual rainfall amounts to about 300 cm.
– The characteristic feature of this type of climate is a reversal in the wind direction with the change of season.
– During the summer season, the wind is on shore, bring large amount of moisture to the land surface. Rainfall is both orographic and cyclonic in nature.
– In winter season the wind is off shore and hence is cool and dry. But some parts like Madras coast get rain during this season because winds are on shore there.
6. Mediterranean Climate:
– This type of climate has developed between 300 – 400 latitudes in both the hemispheres.
– This is a wet-winter, dry-summer climate. Extremely dry summers are caused by the sinking air of the subtropical highs and may last for up to five months.
– This climatic region includes European, Asiatic and African lands bordering the Mediterranean Sea.
– This climate owes its origin to the seasonal shifting of wind and pressure belts due to northward and southward migration of the sun.
– In winter they are under the influence of westerlies which are moisture laden thus brings rainfall in winters whereas they come under the influence of subtropical high pressure belt in summers thus associated with anti cyclonic conditions.
– Plants have adapted to the extreme difference in rainfall and temperature between winter and summer seasons. Sclerophyll plants range in formations from forests, to woodland, and scrub. Eucalyptus forests cover most of the chaparral biome in Australia.
– Fires occur frequently in Mediterranean climate zones.
7. Taiga Climate
|· Temperature Range: lows; -25 °C (-14 °F), highs; 16 °C (60 °F).
· Average Annual Precipitation: 31 cm (12 in).
· Latitude Range: 50° – 70° N and S.
· Global Position: central and western Alaska; Canada, from the Yukon Territory to Labrador; Eurasia, from northern Europe across all of Siberia to the Pacific Ocean.
– This climate type has been named after the coniferous forest cover of the same name found in the region. the region extends from 50-55 degrees to 60-70 degrees latitudes in northern hemisphere.
– It stretches as an almost continuous belt across southern Canada, northern Europe and Russia. The Tundra region lies on the north and the Temperate Grasslands on the south.
– The areas are – Southern Alaska, Southern Canada, parts of Norway, Sweden, Finland, Northern Russia, Northern Siberia, Sakhalin Island.
– Winters are very cold and severe from 6 to 7 months with temperatures below freezing. In this region lies Verkhoyansk the “cold pole” colder than the Arctic region.
– Summers are short lasting for 3 or 4 months but the days are long; at 60°N the sun shines for over 18 hours.
– Rainfall varies from 25 to 100cm. There is more rainfall near the coast. Most of the rain comes from cyclonic weather. It falls throughout the year but maximum in summer in frequent showers. In winter it takes the form of snow, which may remain, on the ground from 5 to 7 months.
– The vegetation associated with this climate type is the soft-wood coniferous forests.
8. Tundra Climate
|· Temperature Range: -22 °C to 6 °C (-10 °F to 41 °F).
· Average Annual Precipitation: 20 cm (8 in).
· Latitude Range: 60° – 75° N.
· Global Position: arctic zone of North America; Hudson Bay region; Greenland coast; northern Siberia bordering the Arctic Ocean.
– The tundra climate is found along arctic coastal areas. Polar and arctic air masses dominate the tundra climate.
– The winter season is long and severe. A short, mild season exists, but not a true summer season. Moderating ocean winds keep the temperatures from being as severe as interior regions.