Introduction

Equatorial Region:

Between 5 and 10 ° North and South of the equator. The temperature is uniform throughout the year with no variations. Cloudiness and heavy precipitation make the climate bearable. The annual range of temperature is small and so is the diurnal range of temperature [ range of temperature in a 24-hour period]. Rainfall is heavy throughout the year with no dry period. The equinoxes coincide with the periods of maximum rainfall [April and September].

1. • The morning is bright and sunny.

1. • The afternoon sees heavy convectional rainfall accompanied by lightning and thunder.

1. • The relative humidity is high and the weather feels sticky.

1. • Equatorial vegetation has features like:

1. • Growing season throughout the year.

1. • Great variety of vegetation

1. • Trees are tall as they compete for sunlight. Undergrowth is less as sunlight may not reach the ground.

1. • Tropical and equatorial forests have a large number of species in a small area and this makes commercial exploitation tough. Also, the hardwood doesn’t float on water and is difficult to transport. Thus most of these nations are net importers of timber.

Oil palm, cocoa, and rubber are the main crops.

The hot and wet climate throughout the year. Rainfall during the evening and high biodiversity. Intense competition amongst species for survival. A large number of species in a small area makes it tough for exploitation. Presence of many epiphytes.

Also, the trees are hardwood and difficult to transport by rivers. Hence most of these regions are importers of timber.

Living conditions are poor because of the hot and moist climate. High incidents of disease. Death rates are higher in equatorial and tropical regions due to the pathogens finding it easier to spread in moist weather than the dry weather in deserts.

Deserts of the World

Deserts

Deserts occupy 1/5th of the World’s land. They are almost always present in 15-30 degrees parallel both north and south of the equator. They lie in the trade wind belt on the western margin of continents and hence receive offshore trade winds. They are also bathed by cold currents that have a desiccating effect on the moisture and hence it doesn’t precipitate.

Types of deserts:

1. Trade wind deserts
2. Continental interior desert / mid-latitude desert – they have extreme temperatures.

Desert landscapes:

1. Rocky deserts
2. Stony deserts
3. Sandy deserts
4. Badlands
5. Mountains deserts

Landforms in the desert are formed due to chemical actions of minerals present in rainwater on the rocks [weathering], rapid heating, and cooling of rocks due to high temperatures. Water is expanded on heating in the morning and contracts at night due to low temperature. This also weathers the rocks. Wind effects are also high here as there is no presence of vegetation to block the winds.

Tropical Deserts:

They are present between 15-30 degree latitudes on the western margin of continents. They receive offshore trade winds hence low precipitation. Also, they are basked in cold currents which have a desiccating effect on the winds.

The deserts are present on the leeward side or rain shadow side of mountains. Hence they experience low rainfall.

A low population and xerophytic vegetation. However, compared to temperate deserts the annual temperature range is low. Deserts also have high diurnal temperature ranges i.e. day and night temperatures have a high difference.

Desert plants have long roots and thorns in place of leaves to prevent evaporation. Cacti are plants that store water in the stems to withstand long droughts.

Nomadic herders like Bedouins [Sahara] and Bindibu [Aborigines of Australia] tribes are seen in deserts. Tuaregs and Gobi Mongols are nomadic horsemen who have settled here.

Continental deserts:

These are located in the interior region. The rain-bearing winds don’t reach here. They have high annual temperature range than tropical deserts..

Tropical Grasslands: Savannah

Savanna Climate:

A transitional type of climate is found between the hot trade wind deserts and the equatorial forests. There is a distinct cool, dry and hot, wet seasons here. On days the clear sky and the treeless land ensure that the temperatures are high and similarly the nighttime temperatures are low due to the radiation of heat from the land. Thus the high diurnal temperature range is a characteristic feature of the savannas.

Tallgrass and short trees are the features of the savanna forest. Trees are mainly of deciduous origins. Wildlife is plenty. Masaai [nomadic, cattle herders] and Hausa [settled cultivators] are the tribes found there.

The Sudan climate is also responsible for the rapid deterioration of soil fertility. The torrential rains cause heavy leaching of minerals like nitrates, potassium, and phosphates. Then in the summer, the high evaporation rates water of the soil dries up and so the savanna regions have laterite soils. These can’t have good yield unless proper fertilizer treatment is given.

Temperate grasslands: Steppe

These are practically treeless grasslands in the interiors of the continents. They are remotely located and are far away from the influence of any moisture-bearing winds.

In the Northern hemisphere, these are the Steppes and the Prairies, in the Southern hemisphere they are Pampas, Velds, and Downs. In the northern hemisphere, these grasslands face extreme heat in summer and extreme cold in winter.

This is due to being far away from the moderating influence of the sea. In the Southern hemisphere, due to moderating influence of the oceans, extreme temperature swings are absent. Rainfall is mild in the north compared to the south.

Wheat cultivation is the major occupation in the prairie grasslands. But due to the large landholdings, one characteristic feature of agriculture is poor yields. This is due to the low attention that can be paid by a farmer compared to those who have small landholdings.

However, due to the sparse population majority of the wheat is exported and so the Prairies are called the Granaries of the World. 75% of Canadian wheat is exported to European nations that though have higher yields but can’t feed their dense populations.

Wheat has two types:

1. • Summer wheat: This is grown in parts where winter temperatures are too low and so seedlings are sown in summer. This wheat is used for making cakes, biscuits, and pastries as it is too soft for bread making. 25% of the wheat produced is of this type.

1. • Winter wheat: 75% of wheat is of this type. It is sown in winter and dried in summer and so becomes hard. This is best for making bread.

Tropical Monsoon and Tropical Marine:

The basic cause of monsoon climate is the difference in the rate of heating and cooling of the land and sea. The summer sees intense heating of the tropic of the cancer region which is the Tibetan plateau; the heating causes a zone of low pressure to develop there.

At the same time in the southern hemisphere, there is winter and a high-pressure belt is formed around the Continent of Australia. The winds blow from high pressure to low pressure and they are attracted to the Indian subcontinent which they reach as the “Southwest Monsoon”.

The conditions are reversed and in the winter a high-pressure zone develops in the Central Asian region. The winds blow from there to the low-pressure belt in Australia created by intense heating as the sun is now over the Tropic of Capricorn. These winds arrive in Australia as the Northwest monsoon.

Thus, the Tropical Monsoon climate is characterized by the seasonal reversal of winds.

Seasons:

Cool and Dry winter:

The high-pressure belt over Central Asia leads to out-blowing dry winds. These cause some cyclonic showers over North West belt of India. These winds then cross the Bay of Bengal and acquire some moisture. This moisture causes precipitation over the Southern tip of India which is the Andhra Pradesh, Tamil Nadu region.

Hot, dry summer:

This period sees intense heating of the Indian subcontinent and no precipitation is seen. This lasts from March to May.

Mid-June to September:

This is the rainy season in the subcontinent and during this period almost all of the precipitation is seen. Heavy and concentrated rainfall is a characteristic feature of the Tropical Monsoon climate.

Tropical Marine climate:

This occurs on the Eastern coast of Tropical countries. They receive rainfall from onshore trade winds continuously throughout the year. The pattern of rainfall is that a peak is seen during the summer which lasts for 4 months. However, these regions are also affected by tropical cyclones, hurricanes, and tycoons.

Tropical monsoon forests:

These are deciduous due to the presence of a dry period in the rainfall. Thus the leaves are shed. The monsoon forests are less thick and have far fewer species in an area compared to equatorial forests. This also means that they can be commercially exploited for timber. The tropical countries are major producers of timber for the world.

Agriculture is the main occupation of most people and the main crops are rice [most characteristic crop of monsoon and marine regions], sugar cane [commercial cash crops], jute [grown mostly along the Ganga – Brahmaputra delta], tea, and coffee.

The western margin of temperate areas: Mediterranean Climate

These are regions found in the western margins of continents between 30-45 degrees North and South of the equator. The basic cause for this type of climate is the “Shifting of Wind Belts”.

Climate

In summer there is a dry, warm period. Due to the movement of the sun to the top of the tropic of cancer, a warm zone or low-pressure region is built in the Mediterranean region and so rain-bearing winds are not seen here. But offshore trade winds blow here which don’t bring much precipitation.

Wet winter is a characteristic feature of these regions. The precipitation is brought by the westerly which is onshore. The Wet Winters is a unique characteristic of this region. However, this affects the grassland as a cold wet season isn’t favorable for the growth of grass and it is thus wiry and bunchy and unsuitable for animal farming. Due to this reason, cattle herding isn’t practiced here and Mediterranean regions are Net importers of Dairy products.

Citrus fruit cultivation is practiced here and this region is responsible for the majority of the World’s exports. Olive trees can also grow here as they can survive long spells of dry seasons due to their long and deep roots. Since animal fats are scarce here olive oil is the main source of cooking oil.

Grape cultivation or viticulture is practiced here commercially. A long dry summer is most suitable for grape cultivation. Almost 75% of the World’s wine production comes from here.

Famous wines:

1. 1. 1. Sherry – Spain
      2. Port wine – Portugal
      3. Chianti, Asti, Marsala – Italy
      4. Champagne, Burgundy, Bordeaux – France

Eastern margin of temperate areas:

Warm moist summer and cool dry winter is seen in this region. These regions occur in the Eastern margins of continents present in the temperate regions. The regions see a high annual temperature range.

Due to the southeast monsoon, there is rainfall in summer, and the northwest monsoon leads to rainfall in winters. Typhoons occur in late summer and are disastrous.

In the Gulf of Mexico region of the USA, there are hurricanes or thunderstorms in summer and local intense heating in winter creates highly destructive tornadoes. This region is also known as the “Tornado Alley”.

The China-type climate is modified in the Southern hemisphere due to the moderating influence of the Oceans. The annual temperature range is lower. Hurricanes or typhoons are absent but less destructive weather activity is seen here too.

Natural vegetation is evergreen as rainfall is throughout the year and no dry period is present. The adequate rainfall has made this region the most productive and intensively cultivated region.

Rice is the main crop of China and Eastern margin countries of Asia. Since rice isn’t the staple food of the gulf states, they grow corn and maize, cotton, and tobacco. The Corn Belt of the USA accounts for half of the World’s production but doesn’t export much as a great part of it is used for fattening Cattle and Pigs. These are sold to slaughterhouses and the meat is exported as “corned beef” or “frozen and chilled beef”.

Other commercial crops are cotton and tobacco. The cotton belt is a major producer of cotton and the yield is high. The crop requires conditions like long summer and adequate rainfall. As both are seen here the productivity is high. Tobacco too is grown plenty as it is the native crop of the US.

China Type: – Rainfall throughout the year. Typhoons occur in late summer.

Gulf type: – no distinct dry season. Less annual temperature range.

Natal type: – rainfall throughout the year.

Cool temperate western margin [British type]:

This climate sees mild summers and winters and so a low annual temperature range. This season is suitable for maximum mental alertness and productivity. Therefore these regions are known as the Maximum Productivity region of the World.

The mildness of the temperature is also due to the influence of the North Atlantic drift.

There are four seasons: Small winters where snowfall is expected, spring which is dry and refreshing, summer which is long and sunny and then autumn or fall when leaves of trees fall down. The Autumn season is a characteristic of the temperate regions as it is absent in the tropics.

Warm summer, cool winters. Best for human habitation and low annual range of temperature.

Temperate cyclones give rainfall in winter. Rainfall from Westerlies and so west coast receive the most rainfall.

Cool temperate eastern margin [Laurentian type] and Continental area [Siberian Type]:

Coniferous forests are found in Siberia, Taiga is the greatest single band of coniferous forests. The Siberian type of climate is completely absent in the Southern hemisphere due to the narrowness of continents in the high latitudes as well as the moderating influence of the oceans. The coniferous forest has limited tree species like Pine, Fir, Spruce, and Larch.

They are commercially exploited for softwood. The World’s largest softwood producer is USSR, the USA is a leader in wood pulp and Canada is a leader in Newsprint. A luxurious coniferous forest has made this possible.

Vegetation of non-conifers is low due to harsh conditions like small summers. Conifers have adapted themselves to this climate by showing remarkable features like:

1. 1. 1. Conical shape – Snow falls to the ground
      2. Thick, needle-shaped, leathery leaves – check excess transpiration. Due to the evergreen nature of trees, there is little leaf fall, also low temperature means the decomposition rate is less plus the needle-shaped leaves are slow to decompose. Podzolized soils of coniferous forests are acidic and hence humus content of the soil is low. Thus coniferous forests have low undergrowth.

Not in the southern hemisphere as hardly any land below 40 degrees. In North America, rainfall throughout the year. Temperate regions have profitable fishing and coniferous forests. Found only in the northern hemisphere.

Taiga

Found between tundra region and Laurentian climate. Very cold winter and warm summer. High annual temperature range. Rainfall throughout the year and temperate cyclones. Found only in the northern hemisphere.

Tundra:

Tundra vegetation is seen here in the low lands where a few frost-free months are there. The polar climate is seen mostly in the Northern part of the North American continent and the Northern part of Russia. Ice caps are seen in the Greenland area.

Freezing in winter. Thawing in summer. Aborigines are seen. Ephemeral [short-lived] flowering plants. Found only in the northern hemisphere.