Prepare Prelims-2017-Day-39-World Geography

Steppe Climate:

Bordering the deserts, away from the Mediterranean regions and in the interiors of the continent are the Temperate grasslands
Feature semi-arid or steppe climate, which lies between the tropics & Polar Regions.
Though they lie in the westerlies wind belt, they are so remote from maritime influence that the grasslands are practically treeless.
Grass are generally distinct in natural vegetation as those lie in S-Hemisphere have a much moderate climate due to coastal effects of the seas & warm currents alongside
Whereas grasslands in N-Hemisphere are comparatively warmer in summers & colder in winters as they are entirely continental.
In Eurasia, they are called Steppes, which stretches eastward from the shores of Baltic Sea across the Great Russian plains, to the foothills of Altai Mountains, for approx. 2000 miles
In isolated sections of Hungary & Mongolian-Manchurian region, they are known as Pustaz of Hungary and the plains of Manchuria.
In North America, the grasslands are quite extensive & known as Prairies, lying between foothills of Rockies & the Great lakes astride American – Canada border
In the southern hemisphere, due to the narrowness of temperate portions of southern continents, grasslands are rather restricted & less continental
In case of Pampas of Argentina & Uruguay, the grasslands extend right to the sea & enjoy much maritime influence
In South Africa, the grasslands are sandwiched between the Drakensberg & Kalahari deserts; & are further divided into the more tropical Bush Veld in the north, & more temperate High Veld in the south
In Australia, the grasslands are better known as Downs & are found in Murray-Darling basin of southern Australia

Steppe Climate

In northern hemisphere, they lie in the heart of continents & thus have little maritime influence
Hence climate is continental with extremes of temperature.
Summers are very warm, approx. 25 degree Celsius, with winters are chilling cold, with well below freezing point viz. approx. – 20 degree Celsius
Hence have high annual range of temperature
In contrast, in southern hemisphere, climate is never severe, with mild winters of ~ 10 degree Celsius & warm summers with ~ 20 degree Celsius, due to the maritime effect of the coasts
Hence annual range of temperature is way less than that in northern hemisphere steppes.
Annual precipitation in N – Hemisphere has a mean annual of approx. 50 Cm, with majority of rainfall in summers from convectional sources.
Winter rainfall of approx. 25 mm/ month is occasional by depressions of the westerlies & in form of snow.
Due to maritime influence in southern hemisphere, mean annual rainfall always averages more than 50 cm, mainly due to warm ocean currents that wash the shores of steppe lands.
On the eastern slopes of the Rockies in Canada & USA, a local wind similar to Fohn (Switz), called Chinook, comes in south west direction to the Prairies, descending from the Rockies. It is a hot wind that rises the temperature & melts snow covered pastures, generally in winters & early springs, hence frequent chinook means mild winters in the region.

Natural Vegetation of Steppe

Natural vegetation of steppes is generally referred as temperate grasslands, differing only in density & quality of grass.
Their greatest difference from tropical savannas is that steppes are practically treeless & grasses are much shorter.
Regions in N – Hemisphere, where the rainfall averages above 50 cm, the grasses are tall, fresh & nutritious & are better described as long prairie grass
Examples include North America, Rich black earth of Russia –Ukraine & better watered areas of Asiatic steppe.
Where the rainfall is light, less than 50 cm, or the soil is poor, as in continental interiors of Asia, the short steppe type of grass prevails.
The grasses are not only shorter but also wiry & sparse, often found in discontinuous clumps, with bare soil exposed between them.
The climatic requirement of grass are quite different from trees as they require less moisture than trees & an annual precipitation of approx. 25 – 50 cm is adequate.
Their growth is not abruptly checked by summer drought & winter cold as they lie dormant throughout this period & sprout instantly as soon as temperature is moist & warm again.
Trees are very scarce in steppes, because of the scanty rainfall, long droughts & severe winters; with long rolling plains of endless grass.
Poleward, an increase in precipitation gives rise to a transition zone of wooded steppes where some conifers gradually appear, but are very scattered & few in number.
Towards the equator, the steppe grass becomes shorter & sparser, till it merges into desert with thorny scrub.

Economic Development

Grasslands have been ploughed up for extensive mechanized wheat cultivation & are termed as granaries of the world.
Beside wheat, maize is also increasingly cultivated, mainly in warmer & wetter areas.
Farms are extensively long, hence due to less attention & high mechanization, average yield per acre is low, but the yield per man is very high
Hence grasslands of mid latitudes produce greatest exporters of wheat in the world.
The tuft grasses have been replaced by more nutritious lucerne & alfalfa grass for cattle & ship rearing.
Natural conditions suit animal farming & with the introduction of more nutritious grass & refrigerated ships, temperate grasslands became major pastoral regions, exporting large quantities of beef, mutton, wool, milk, butter, cheese & other dairy products such as Pampas became lead exporter of beef.
Australia became world’s leading wool exporter.

Importance of Temperature

Temperature influences the actual amount of water vapour present in the air & thus decides the moisture carrying capacity of the air.
It decides the rate of evaporation & condensation, & therefore governs the degree of stability of the atmosphere.
As relative humidity is directly related to the temperature of the air, it affects the nature & types of cloud formation & precipitation

Factors influencing Temperature

Latitude	§ Due to the earths inclination, temperature reduces from equator to poles § Mainly due to direct & oblique sunrays falling differently on different latitudes
Altitude	§ Since the atmosphere is mainly heated by conduction from the earth § Hence places near to earth surface are warmer than those higher up § Thus, temperature decreases with increasing height above the sea level
Continentality	§ Land surfaces are heated more quickly than the water surfaces, due to higher specific heat of the water § Hence warmer summers & colder winters prevails in continental interiors as compared with maritime districts
Ocean currents & winds	§ Both ocean currents & winds affect temperature by transporting their heat or coldness into adjacent regions § For e.g. the westerlies that come to Britain & Norway tend to be cool winds in summer & warm winds in winter
Slope, Shelter & Aspect	§ A steep slope experiences more rapid change in temperature than a gentle one. § Mountain ranges that have an eastward alignment like the alps show a higher temperature on the south facing sunny slope than the north facing sheltered slope. § The greater insolation of the southern slope is better suited for vine cultivation & has a more flourishing vegetative cover, consequently more settlements
Natural vegetation	§ There is a definite difference in temperature between forested regions & open ground § Thick amazon forest cuts off much of incoming insolation keeping the land surface of the jungle cool & few degrees lower than the open spaces in corresponding latitudes
Soil	§ Light soils reflect more heat than the darker ones which are better absorbers of heat, which may give rise to slight variations in temperature of the region. § Dry soils like sand are very sensitive to temperature compared to wet clayly soils which retains moisture & warms up & cools down more slowly

Precipitation

Condensation of water vapor in air in form of water droplets or ice
Their falling on earth surface is known as precipitation

Snowfall

When condensation takes place below freezing point
Means at 0*C, conversion of water vapour directly into solid state
Precipitation occurs in forms of fine flakes of snow

Sleet

Sleet is frozen raindrops or refroze melted snow water
When a layer of temp. above freezing point overlies a subfreezing layer near the ground, precipitation occurs in form of sleet

Hail

Sometimes, drops of rains after being released by the clouds become solidified into small rounded stone pieces of ice, known as hailstones
Formed by rainwater passing through colder layers hence have several concentric layers of ice, one over the another

Rainfall

Most common form of precipitation
Precipitation in form of water
Also known as cloud particles

Types of Rainfall

Convectional Rainfall

Air on being heated becomes light & rises up as conventional currents
As it rises, it loses heat & consequently condensation takes place with the formation of cumulus clouds.
Under these conditions, heavy rainfall takes place along with thunder & lightening, but does not last for long
Common in Equatorial & Tropical regions in summers daily

Orographic / Relief Rainfall

When a warm & moist air currents is obstructed by a mountain range, it is forced to ascent along its slopes
It gets cooled while ascending & when its temp. falls below dew point, it causes rainfall on windward slope of mountain range
However, when these winds cross mountain range & descend along its leeward side
Here, they get warm & dry & causes only little rain (Rain shadow areas)
This type of rainfall may occur in any season

Cyclonic / Frontal Rainfall

Rainfall associated with cyclone is known as cyclonic/ frontal rainfall
Occurs along the fronts of the cyclone viz. cold front & warm front
At the warm front, the warm lighter wind rises gently over the heavier cold air, which being heavy stays close to the ground
As the warm air rises, it cools, and the moisture present in it condenses to form clouds altostratus clouds
This rain falls steadily for a few hours to a few days.

Planetary Winds

Planetary winds are also known as permanent or prevailing winds
Blow from high to low pressure, over the earth surface & oceans throughout the year & in a particular direction
These winds are divided into 3 categories viz.

Trade Winds (Tropical Easterlies)
Westerlies
Polar winds (Polar Easterlies)

Trade Winds (Tropical Easterlies)

Winds blowing from subtropical high pressure area to equatorial low pressure area (Extremely steady winds)
Since they travel from high latitude to low latitude area, they become gradually hot & dry and hence have a great capacity to hold moisture
They cause considerable rainfall on eastern margins of the continents as they get moisture after blowing over oceans
These winds converge near equator & form ITCZ, Here these winds rises & causes heavy rainfall
Absent in N Indian Ocean which is dominated by Monsoon winds.

Westerlies

Winds blowing from subtropical high pressure belts towards subtropical low pressure belts
Blow from S – W to N – E under Coriolis effect in N – Hemisphere & from N – W to S – E in S – Hemisphere
Blow from lower latitudes to higher latitudes
Cause considerable rainfall particularly on western margins of the continents
More consistent in direction & blow with stronger force in S – Hemisphere due to lesser obstructions from continents
Also known as brave winds or roaring forties, furious fifties & shrieking sixties according to the varying degree of storminess in the latitudes in which they blow.
It must be noted that not all the western coast of the temperate zone (30* – 60*) receive Westerlies throughout the year due to shifting of wind belts coz of earth’s inclination.

In June, when the overhead sun is over the tropic of cancer, all the belts move about 5* – 10* north of their average position. The Mediterranean parts of continents that comes under the effect of werterlies, receive rain in June & vice a versa in December, when sun is overhead tropic of Capricorn

Polar winds

Winds blowing from polar high to sub polar low pressure belt
Are very cold in nature as originate in polar areas & do not cause much rainfall
These winds give birth to cyclones when they come in contact with westerlies
Brings frequent change in weather conditions & causes heavy rainfall

Shifting of Wind belts

Wind belts described above keep on shifting northward & southward depending upon the movement of the sun
March 21 & Sep 23 (Equinoxes)

Sun shines vertically over equator
Equatorial low pressure belt lies b/w 5* N – 5* S

After March 21, sun moves northward & with it whole system of pressure belts moves northward
June 21→ Sun shines vertically over Tropic of cancer & all the pressure belts move 5 – 10 * northward from original position
Dec 21→ Sun shines vertically over Tropic of Capricorn & all the pressure belts move 5 – 10 * southward from original position
Thus, shifting of world’s pressure belts also causes shifting of world’s wind system

Periodic / Seasonal winds

Winds which change their direction periodically
Examples →Monsoon Winds, Land & Sea Breeze, Mountain & Valley Breeze

Monsoon Winds

Refers to system of winds which reverses their direction completely with change of seasons
Blow from sea to land during summers & land to sea during winters, due to differential in heating of continents & oceans →Halley’s law
In summers, sun shines vertically over Tropic of cancer resulting in high temp. & low pressure in central Asia, while pressure is sufficiently high at Bay of Bengal & Arabian Sea.
This induces air flow from Sea to land & induces heavy rainfall in India & neighboring countries
In winters, sun shines vertically over tropic of Capricorn, hence N – W part of India grows colder than Arabian Sea & Bay of Bengal which results in reversal of monsoon in India
Above theory of differential heating was replaced by shifting of ITCZ for monsoon in India & neighboring countries

Land & Sea Breeze

Influence only a narrow strip of 20 – 30 km along the coast
During day sun shines hence sea breeze moves from sea to land (Sea Breeze)
In night it reverses its direction i.e. from land to sea (Land Breeze)

Mountain & Valley Breeze

During day, mountain slopes gets heated more than valley floor hence air from valley floor blows up the slope (Valley Breeze)
After sunset pattern is reversed i.e. Mountain Breeze

Fohn Wind & Chinook Wind

Both the Fohn & Chinook winds are local hot & dry winds experienced on the leeward side of the mountains when descending air become compresses with increased pressure.
Fohn wind is experienced in the valleys of northern Alps, particularly in Switzerland in spring.
Chinook winds are experienced on the eastern slopes of the Rockies in USA & Canada in winters.
While descending, most of the moisture of the wind is lost & hence it becomes dry & hot, which may lead to rise in temperature of leeward side.
In North America, it is called Chinook which means the snow eater, as it melts the snow & causes avalanches.

It has blessings too, it enhances the growth of crops & fruits & thaws the snow covered pastures by raising temperature of the region quite quickly.

Cyclones

A low pressure area surrounded by high pressure area from all from all the sides along with winds moving from all the sides towards central low
Cyclones moves in Anti clockwise in N – Hemisphere & in Clockwise direction in S – Hemisphere under the effect of westerlies due to coriolis effect
No Cyclones at equator as coriolis force is 0 there

Temperate Cyclones

Also known as wave cyclones or Extra Tropical
Originate mainly in zones b/w 35* – 65* N & S of latitudes

Polar Front Theory → Forms due to collision of 2 air masses of contrasting characteristics (in terms of temp. & humidity at about 60* latitude). Here they do not meet each other readily but forms a front known as polar front

Cold air mass pushes the warm air mass upwards & a void is created due to decrease in pressure.
Air from surrounding area rushes to fill the void & a temperate cyclone if formed
Average speed of extra tropical cyclone is 32 km/hr in summer & 49 km/hr in winters

Tropical Cyclones

Also known as Typhoons or Hurricanes
Originate mainly in zones b/w 5* – 30* N & S of latitudes
Are the violent storms that originate over oceans in tropical areas & move to coastal areas
Bring large scale destruction, caused by violent winds, heavy rainfall & storm surges
Favorable conditions for formation of tropical cyclones are
Large sea surface with temp. > 27*C
Presence of coriolis force
Small variation in vertical wind speed
Upper divergence above sea level
Pre-existing weak low pressure area or low level cyclonic circulations

Energy that intensifies the storm comes from the condensation process in towering cumulonimbus clouds, surrounding center of the storm.
Hence, with constant supply of moisture from the sea, storm is further strengthened
On reaching land, moisture supply is cut off & the storm dissipates
Place where tropical cyclone crosses the land is called landfall of the cyclone
Central low pressure is known as eye of the cyclone → Calm with subsiding air having lowest pressure & highest temp.
Surrounding this area is zone of strong winds with clouds extending vertically
Surrounding the eye is eye wall, a place of strong spirally ascending winds to a height reaching tropopause, having max. wind velocity

Tropical Cyclone Distribution & its various names worldwide

Name	Country
Cyclone	Indian ocean, Arabian sea & Bay of Bengal
Hurricane	Atlantic sea (West indies) & USA
Typhoons	China sea + Japan sea
Willy Willies	Western Australia

Difference between Tropical & Extra Tropical Cyclones

Tropical Cyclones	Extra Tropical Cyclones
Moves from east to west	Moves from west to east
Wind velocity is very high & more destructive	Low wind velocity & less destructive
Originate only on sea & dissipates on reaching land	Affect much larger area & can originate on land as well as sea

Anticyclones

An anticycloneis just opposite to a cyclone
Basically it is a large-scale circulation of winds around a central region of high atmospheric pressure
Clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere
Anticyclones are form from air masses, cooling more than their surroundings, which causes the air to contract slightly making the air denser
Since dense air weighs more, the weight of the atmosphere overlying a location increases, causing increased surface air pressure
Anticyclones herald fair weather, clearing skies, calm air with high temperature in summers & cold in winters
Fog can also form overnight within a region of higher pressure

Savanna:

Savanna or Sudan climate is a transitional type of climate found between the equatorial forests & trade wind hot deserts.
It is confined within the tropics (Tropic of Cancer & Tropic of Capricorn) & is best developed in Sudan, where dry & wet climate are most distinct, hence named Sudan climate.
It covers much of Africa (Keya, Nigeria, Gambia) as well as large areas of Australia, South America (Brazilian highlands), and India.
Sudan climate is characterized by an alternate & distinct hot, rainy season (from May to Sep) & cool, dry season (Oct – April) in N – Hemisphere & vice versa in S – Hemisphere.
The savanna climate has a temperature range of 18° – 30° C.
In winters, it is usually about 18° – 25° C & in summers, the temperature ranges from 25° – 30° C.
Like the monsoon climate, the maximum temperature tends to occur in late spring to early summer prior to the onset of the rainy season, with Daily temperature range greater during the dry season & annual temp. range increasing towards poleward from equatorial region.
Both the length of the rainy season as well as annual total rainfall decreases from equatorial region to polewards.
On the whole, the annual precipitation (~100 cm annually) is less than the tropical monsoon climate & length of wet & dry seasons differs with the locality.
Prevailing winds of the region are the trade winds, which bring rain to the eastern coastal districts.
They are strongest in summers but are relatively dry by the time tome they reach the continental interiors or western coasts of the continents, so scattered grasses & short trees dominates.

In west Africa, N-E trade winds blow from the Sahara Desert & reach Guinea coast as dry dust laden winds called locally ‘Harmattan’, means the doctor, which increases the rate of evaporation & provides cooling effect at Guinea coast; but it is such a dry dusty wind that, besides ruining the crops, sometimes it may cause fire; it also stirs up a thick dusty haze & impedes inland river navigation.

Natural Vegetation of Savanna Climate Region

Savanna landscape is generally characterized by Tall grass (6 – 8 feet) & short trees.
Savannas are generally known as tropical grasslands, but it is rather misleading as trees are always present with the luxuriant tall grass.
Trees grow best towards the equatorial humid latitudes or along the river banks but decrease in height & density away from the equator.
Trees are generally deciduous, shedding their leaves in cool, dry season to prevent excessive loss of water through transpiration for e.g. aracias.
Others have broad trunks to store water to survive through the prolonged drought such as baobabs & bottle trees.
Palms, which cannot stand drought, are confined to the wettest areas along the rivers.

Vegetative luxuriance reaches its peak in rainy season, when trees renew their foliage & flower.
Grass lies dormant throughout the long dry period & springs up again in next rainy season.
In true savanna lands, the grass is tall & coarse growing 6 – 12 feet on height (Elephanta grass); grows in tufts and have long roots, which reach down in search of water.
In-between long grasses are scattered short trees & low bushes.
As rainfall diminishes towards the deserts, the savanna merges into thorny scrubs.

Savanna Animals & Agriculture

Savanna, particularly in Africa, is the home of diverse varieties of wild animals
Known as Big game country
Many of the animal films that we see in cinemas are actually taken in savanna.

Human Life in the Savanna:

Some tribes lives as cattle pastoralists like Masai of East African Plateau and others as settled cultivators like Housa of Nigeria
Tropical grassland animals (which do not all occur in the same area) include giraffes, zebras, buffaloes, kangaroos, mice, moles, gophers, ground squirrels, snakes, worms, termites, beetles, lions, leopards, hyenas, Zebu cattle and elephants.
The world’s greatest diversity of ungulates (hoofed mammals) is found on the savannas of Africa.
The soil of tropical grasslands is porous, with rapid drainage of water.
It has only a thin layer of humus (the organic portion of the soil created by partial decomposition of plant or animal matter), which provides vegetation with nutrients.

Problems, Prospects and Development of Savanna:

The Sudan climate, with distinct wet and dry periods is also responsible for deterioration of soil fertility.
During rainy season, torrential downpours of heavy rain causes leaching, leading to drainage of soil nutrients
During the dry season, intense heating & evaporation dries up soils water.
Many savanna areas therefore have poor laterite soils, incapable of supporting good crops, unless the soil is properly conserved by manuring & weeding.
Savanna is said to be a natural cattle country & many of its native people are herdsman & pastoralists with cattle kept in large numbers for meat & milk; but the settlements in central Africa, Northern Australia & Eastern Brazil have shown an immense growth potential in food & plantation crops such as :
Maize, Millet, Corn, Bananas, Beans & Groundnuts are food crops of Savanna
Cotton, Tobacco, Sugarcane, Coffee, Groundnuts, Oil palms & Tropical fruits are plantation crops of savanna.

Hot Wet Equatorial Climate

Equatorial hot, wet climate is found between 5* – 10* north & south of the equator mostly viz.
the Amazon Basin (South America)
the Congo Basin (Africa)
Malaysia
Indonesia
Singapore

The most outstanding feature of the equatorial climate is its great uniformity of temperature throughout the year with no winters.
The average monthly temperatures are about 26 – 28 degrees Celsius, with small annual range of temperature ~ 3*C & fairly greater diurnal range of temperature ~ 12* – 15*C.
Cloudiness and heavy precipitation ~ 150 – 250 cm of rainfall or more in a year, helps to moderate the temperature, so that even at the equator, climate is not unbearable.
There is no month without the rain & a distinct dry season like that of savanna or tropical monsoon climate is absent.
Most of the rainfall is convectional, with thunderstorm & lightening often accompanying the torrential showers.
The convection uplift is related to the position of the ITCZ and rainfall totals double when the sun is directly overhead at the spring and autumn equinox, with the least rain falls at June & December solstices.
Besides the convectional rainfall, mountainous regions also experience much orographic or relief rainfall
In addition, there are some intermittent showers from cyclonic atmospheric disturbances caused by the convergence of air masses at Doldrums.
The relative humidity is constantly high ~ over 80 %, making one feel sticky & uncomfortable

Vegetation in Equatorial Regions

The year round high temperatures and abundant rainfall in equatorial regions support a luxuriant type of vegetation – Tropical or equatorial rain forests.
In the Amazon lowlands, the forest is so dense & extravagance that a special term Selva is used to describe it.
Unlike the temperate regions, the growing seasons here is all year round
Seeding, Flowering, Fruiting & Decaying do not take place in seasonal pattern, so some trees may be flowering while others only a few yards away may be bearing fruits.
There is neither drought nor cold to check the growth in any part of the year.
Unlike the temperate forests, many different types of trees and other plants can be found growing in a relatively small area of rainforest.
Rainforests cover only about 6 % of the Earth’s surface.
However, they contain about half of the world’s known animal species and provide about 40% of the world’s oxygen.

Equatorial vegetation comprises a multitude of evergreen trees that yields tropical hardwood viz. Mahogany, Ebony, Greenheart, Cabinet Woods & Dyewoods.
There are smaller palm trees, climbing plants like lianas & epiphytic & parasitic plants that live on other plants.
Under the trees grow a wide variety of ferns, orchids & lalang (tall grass)
There are several layers of vegetation in a rainforest with all plants struggling to move upward to get sunlight.
The uppermost layer is made up of the crowns of the tallest trees with average height 45 – 60 meters are known as emergent, with their crowns exposed to the direct sunlight.
The next layer is known as the canopy with an average height of about 20 to 40 meters.
The crowns of the trees in this layer are tightly packed together forming a nearly unbroken cover for the forest floor.
If you were looking down on a section of the rainforest from above, you would not be able to see the ground because of the cover provided by the canopy, very little sunlight reaches the lower layers of the rainforest.
Below the canopy is another layer known as the understory with trees only few meters high.
Here one can find trees which only grow to about 15 meters at maturity as well as young saplings which will eventually grow to reach the canopy. Sunlight here is limited.
Between understory & the forest floor lays the shrub layer, composed of ferns & shrubs.
Only about 1% or 2% of sunlight reaches this layer.
Therefore, only few plants are able to thrive there which must be able to tolerate low light conditions.
In order to support their great height, many trees have buttress roots(also called plank buttresses) which extend above the ground and along the trunk on all sides.
Some plants in the lower layers of the rainforest have verylarge leavesin order to make efficient use of the little sunlight which reaches them.
Some plants, known as lianas, are vines which are rooted in the soil and grow up the trunks of trees all the way into the canopy where their leaves can get more sunlight.
Some plants, known as epiphytes, grow on trees (their roots are not in the soil).
They do not harm the trees and they do not get their nutrients from them. They only use the trees for physical support.
There are other plants which are parasites.
They grow on other plants and get their nutrients from them, damaging them as they do so.
There are other plants known as strangler figs.
They start out by growing on a host tree, and then they grow long roots down the trunk of the tree and into the soil.
These roots grow larger and begin to surround the trunk of the host tree.
Eventually the host tree will die, leaving the strangler fig in its place.
Many parts of the virgin tropical rainforests have been cleared either for lumbering or shifting cultivation.

Life & Development in Equatorial Regions

The equatorial regions are generally sparsely populated with shifting cultivation as major agricultural practice
Major crops being manioc (tapioca), yams, maize, bananas & groundnuts
Food is abundant in form of animals, birds, fishes, fruits, nuts & other jungle produces.
In the Amazon basin, Indian tribes collect rubber and in the Congo basin Pygmies gather nuts.
Certain high value industrial crops for which equatorial climate suits best are grown now a days such as rubber, cocoa, oil palms, coconuts, sugarcane, coffee, tea etc.
Home country of discovery of rubber, Brazil (Amazon basin) exports no natural rubber due to tree diseases & lack of commercial organizations of Indian at Amazon lowlands.
Currently, Malaysia & Indonesia are leading producers of rubber in the world.
Cocoa is cultivated most extensively in West Africa with two most important producers Ghana & Nigeria.
From the same area another crop, oil palms have done equally well.

Factors affecting the development of Equatorial Regions:

Under the conditions of excessive heat & high humidity, man is subjected to physical & mental handicap
One loses vigour in such an enervating environment along with high exposer to sun strokes, malaria & yellow fever.
The hot, wet climate which stimulates rapid plant growth also encourages the spread of pest & insects
Germs & bacteria are most easily transmitted through moist air; which are injurious to all man, animals & plants.
Jungle is so luxuriant that it is quite a problem to clear small patches in it & even difficult to maintain it.
Lalang & thick grass springs up as soon as shade trees are cut & unless they are weeded at regular intervals, they may choke crops & overwhelm estates.
Roads & railways constructed through the equatorial lands have to cut through forests & those who maintain them encounter wild animals, snakes & insects
Once they are completed, they have a high maintenance cost.
Therefore, many remote parts of Amazon basin & Congo are without modern communications, with rivers as only natural highways.
Though the tropics have great potential in timber resources, commercial extraction is difficult as trees do not occur in homogeneous stands
Have no frozen surface to facilitate logging & tropical hardwoods are sometimes too heavy to float in the rivers, even if these flow in desired direction.
Livestock farming is greatly handicapped by an absence of meadow grass
Bullocks which are domesticated yields milk & beef well below than those in temperate grasslands.
In its virgin state, due to heavy leaf fall & decomposition of leaves by bacteria, a thick mantle of humus makes the soil fairly fertile, but once the humus content is used after shifting cultivation & natural vegetative cover is removed, the torrential downpour soon wash out most of the soil nutrients. Therefore, soil deteriorates rapidly with subsequent soil erosion.

Tropical Monsoon Climate

Also known as a tropical wet climate or trade-wind littoral climate
Marked by seasonal reversal in wind direction giving well defined wet & dry seasons
Mainly due to the difference in specific heat capacity between land and sea
Tropical Monsoon climate is best developed in India, Myanmar, Thailand, Laos, Vietnam, Bangladesh, South China & Northern Australia
Basically found beyond the equatorial region between 10 degree and 25 degree and North and South of the equator.
The tropical monsoon climate experiences abundant rainfall like that of the tropical rain forest climate, but it is concentrated in the high-sun season.
Being located near the equator, the tropical monsoon climate experiences warm temperatures throughout the year.
In the summer, when sun is overhead at Tropic of cancer, the great land masses of the northern hemisphere are heated.
Central Asia, backed by the lofty Himalayan ranges, gets heated intensely, creating a region of extremely low pressure.
The seas, which warm up much slower, remain comparatively cool
At the same time, the southern hemisphere experiences winter, & a region of high pressure is set up in the continental interior of Australia.
Winds blow outward as south east monsoon to java, & after crossing the equator are drawn towards the continental low pressure area reaching the Indian subcontinent as south west monsoon.
In winters, the conditions are reversed & the sun is overhead at the Tropic of Capricorn while the central Asia gets extremely cold, creating a region of high pressure with winds out-blowing as North East Monsoon.
On crossing the equator, the winds are attracted to the low pressure centre in Australia & arrive in Northern Australia as the North West Monsoon.
In other parts of the world, which experience a tropical monsoon climate, a similar reversal of wind directions occurs.
The monsoon climate has a high mean annual temperature and a small annual temperature range like equatorial climate.

Seasons of Tropical Monsoon Climate

Cool, Dry Season (Oct – Feb)

Average temperature ranges between 19 degree Celsius and 23 degree Celsius with frost may occur at night in colder north; a centre of high pressure is developed over Punjab.
Out-blowing dry winds, the N-E Monsoon, bring little or no rain in northern Indian subcontinent;
However a small amount of rain falls in Punjab from cyclonic sources, vital for survival of winter cereals.
When the N-E Monsoon blows over the Bay of Bengal, it acquires moisture & thus brings rain to the south eastern tip of Indian peninsula at this time of the year
For e.g. Chennai receives 125 Cm of rainfall during October & November, accounting for half its annual rainfall.

Hot Dry Season (March – Mid June)

The temperature rises sharply with the sun’s northward shift to the Tropic of Cancer with average temp. of 35 degree Celsius.
Practically, no rain anywhere with an intense low pressure generated over N-W India.

Rainy Season (Mid June – Sep)

With the burst of S-W monsoon in mid-June, torrential downpours sweep across the country.
Almost 95 % of annual rainfall is concentrated within this rainy season of approx. 4 months.
This pattern of concentrated heavy rainfall in summer is a characteristic feature of the tropical monsoon climate.

The Retreating monsoon

Amount & frequency of rain decreases towards the the end of the rainy season;
It retreats gradually southwards after mid-September until it leaves the continent altogether.
Punjab plains which receive the S-W Monsoon earliest are the first to see the withdrawal of the monsoon.
The skies are clear again & cool, dry season returns in October, with the N-E Monsoon.

Tropical Marine Climate

This type of climate is experienced along the eastern coasts of tropical lands, receiving steady rainfall from trade winds all the time.
These areas experience between 120 cm to 200 cm of rainfall annually & include –
Central America
West Indies
N-E Australia
Philippines
Parts of East Africa
Madagascar
the Guinea Coast
Eastern Brazi
The rainfall is both orographic where moist trade winds meet upland masses as in eastern Brazil and convectional due to intense heating during the day in summers
Tendency is towards a summer maximum as in monsoon lands, but without any distinct dry period.
Regions which experience a tropical marine climate have hot & humid temperature all year round but annual temperature range is often quite small.
Temperatures are higher during the wetter season and lower during the drier season.
Due to the steady influence of the trades, the tropical marine climate is more favourable for habitation, but is more prone to severe tropical cyclones, hurricanes or typhoons.

Tropical Monsoon Forests

The natural vegetation of tropical monsoon land depends on the amount of summer rainfall.
Trees are normally Deciduous, because of the marked dry period, during which they shed their leaves to withstand drought.
In tropical monsoon forests, the ecosystems which develop are very similar to the true rainforests which develop in equatorial climates, but are more open, less luxuriant & contains far fewer species.
The layer structure of the forest trees consist of Canopy, understory & shrub layer with average height 25 – 45 m & average rainfall 100 – 200 cm.
Most of the forests yield valuable timber & prized for their durable hardwood such as teak, Rosewood, Sal, sandalwood, Shisham, Banyan, Aracia & some varieties of Eucalyptus in N- Australia.
Together with the forests are bamboo thickets, which often grow to great heights; thorny scrubs with scattered trees & long grass.
Among hardwoods, Teak is extensively used for ship building, furniture & other construction purposes because of its high durability, strength, immunity to shrinkage, fungus & insects; with Burma alone accounting for 3/4^thof the world production

Agricultural Development in Monsoon lands

Major Food Crops

Rice (Most important)
Wheat
Millets
Sorghum
Gram
Maize
Beans (in drier areas where rice cannot be grown)

Lowland Cash Crops

Sugarcane – India, Java, Cuba, Jamaica, Formosa, Trinidad & Barbados
Jute – Ganga Brahmaputra Delta in India & Bangladesh
Manila hemp / Abaca – Philippines (used for making a high quality rope)
Other crops include Indigo, Cotton, Banana, Coconut & Spices

Highland plantation Crops

Coffee

Originated in Ethiopia & Arabia, where it is still grown
But Brazil now accounts for half the world production
Also grows on highland slopes of India, Eastern Java & Central American states

Tea

Originated in china & still important crop there for local consumption
Major exporters are India, Java, Bangladesh & Srilanka

Shifting Cultivation

Also practised in Tropical monsoon forests entirely for subsistence (for consumption only)
Major crops are sweet potato, beans, maize, paddy, yams & tapioca
As tropical soils are mainly latosolic (high content of iron & aluminum oxide), hence rapidly leaches away & easily exhausted

First crop may be bountiful, but the subsequent crops deteriorates
Shifting cultivation is so widely practised amongst indigenous peoples that different local names are used in different countries viz.

Ladang	Malaysia
Taungya	Burma
Tamrai	Thailand
Caingin	Philippines
Humah	Java
Chena	Sri Lanka
Milpa	Africa & Central America

Deserts are the regions of scanty rainfall (less than 25 cm or 10 inch of rainfall)
May be hot like Saharan Desert; Coastal dry deserts like Atacama & Temperate or the mid latitude deserts viz. Gobi.
Hot desert climates are typically found under the subtropical ridge

Deserts Climate Type

Unbroken sunshine for the whole year + stable descending air + high pressure aloft
These areas are located between 15 – 30 degrees south & north latitude, under the subtropical latitudes called the horse latitudes.
Major hot deserts of the world include

Sahara Desert (Africa)
Thar Desert (India)
Libyan Desert (Africa)
Mojave Desert (N-America)
Kalahari Desert (Africa)
Iranian Desert
Arabian Deserts

Hot desert drylands, like the Atacama of Chile, the Namib of southern Africa, and the western Australian desert, are the result of cold oceanic currents that divert rain-laden air away from coastlines.
Among the mid-latitudes deserts, many are found on plateau & are at considerable distance from the sea – Cold Deserts – viz.
Gobi Desert
Turkestan Desert
Patagonian Desert

Causes of aridity of deserts

The hot deserts lie astride thehorse latitudes or sub-tropical high pressure belts, where the air is descending, a condition least favorable for precipitation of any kind.

Rain shadow → Air descending leeward side from mountainous areas warms and dries by compression, little rainfall forms and aridity is the result for e.g. Patagonian desert due to rain shadow effect of Andes.
Cold ocean currents → Cold air present above such currents ensures less evaporation of moisture with scarse evaporation resulting in formation of mist & fog, but no clouds – hence no rain. Effect of cold Peruvian current makes Atacama the driest place of the earth

Continentality →Central areas of continents are dry because they lie far away from the oceans & air moving over landmasses does not absorb large amounts of water vapour, required for precipitation.

Temperature variation in Deserts

Deserts are some of the hottest spots on the earth & have high temperature throughout the year.
There is no cold season in hot deserts & average temp. is around 30 -35*C.
Diurnal range of temperature is extremely high in deserts due to intense high temp. during the day & freezing cold nights.
Days are unbearably hot with highest temp. of 76*C recorded in open barren sand and in shaded, well-ventilated areas viz.
Al- Azizia in Libya has had a recorded high temperature of 58 °C.

An interesting variant of tropical and subtropical deserts are the so-called West Coast Desert areas found on the western coastal margins of the regions such as Atacama deserts of South America, and the Sahara [Moroccan part] and Namib deserts of Africa.

These areas are much cooler than their latitude would suggest (monthly mean temperatures of only 15–21 °C.
The cooling results from airflow off adjacent coastal waters where upwelling of the ocean gives rise to cold currents.
Deserts of this sort are subject to frequent fog and low-level clouds; yet they are extremely arid.

Desert Facts

Deserts cover more than 1/5^thof the Earth’s land, and they are found on every continent.
Despite the common conceptions of deserts as dry and hot, there are cold deserts as well.
The largest hot desert in the world, northern Africa’s Sahara, reaches temperatures of up to 122 degrees Fahrenheit (50 degrees Celsius) during the day.
But some deserts are always cold, like the Gobi desert in Asia and the desert on the continent of Antarctica.
Simoom –Violent dust storms in deserts

Desert Animals Characteristics

Desert animals have adapted ways to help them keep cool and use less water. Camels, for example, can go for days without food and water.
Many desert animals are nocturnal, coming out only when the brutal sun has descended to hunt, have long feet & secrets conc. waste.
Some animals, like the desert tortoise in the southwestern United States, spend much of their time underground.
Most desert birds are nomadic, crisscrossing the skies in search of food.
Because of their very special adaptations, desert animals are extremely vulnerable to introduced predators and changes to their habitat.

Desert vegetation Characteristics

Desert vegetation is an amazing example of adaptive power of plants and trees, which majorly consists of scrub, herbs, weeds, roots & bulbs.
The predominant vegetation of deserts is xerophyte or drought resistant which usually has special ways of storing and conserving water viz. cacti
Trees are rare except where there is abundant of ground water to support clusters of date palms.
Absence of moisture retards the rate of decomposition hence desert soils are deficient in humus content along with high rate of evaporation making the soil saline.
Plants have few or no leaves & foliage is waxy, leathery or hairy / needle shaped to reduce the loss of water through transpiration.
Thick bark & tough skins to protect them while they lie dormant from excessive evaporation
Develop an extended root system close to the surface to collect a lot of water during scant rainfall.
Develop a deep root system and reach groundwater.

Characteristic features of desert vegetation

Stay many years dormant as a seed and when sufficient rain falls, and speed up your active life to a 3 week compressed cycle, producing leaves, flowers and new seeds in no time.
Poison your immediate neighbours, and reduce competition of even your own species.
Remain small, it saves surface through which water evaporates.
Get round, a more advantageous ratio volume/surface, and develop green cylindrical stems able to perform photosynthesis
Cut off your limbs, I mean, led some of your branches die in order to consume less of everything

Nomads in Deserts

Bushmen	Kalahari
Bindibu / Aborigins	Australia
Bedouin	Arabia
Tauregs	Sahara
Mangols	Gobi (Cold Desert)

Minerals in Deserts

Diamond & Copper	Kalahari (Thirst land)
Atacama	§ Caliche (Cemented gravels) → Sodium Nitrate fertilizer § Chuquicamata (Chile) → Largest copper town
Sahara & Arabia	Oil
Mexico	Silver
Utah	Uranium
Nevada	Copper

Mediterranean climate is found between the 30 degree- 45 degree N-S latitudes & gets its name from the climate found around the Mediterranean Sea.
The basic cause of this type of climate is shifting of the wind belts with summers – warm to hot, and winters – cool but mild.
These regions have also been called ‘winter-rain & summer dry’
The Mediterranean biome is divided into five floristic biome subtypes, according to the various floristic realms into which each fall –

Mediterranean	Areas around Mediterranean sea
Californian	Around San Francisco
Chilean	Central Chile (South America)
Capensic	Cape Town, Africa
Australian	Southern & Western Australia

Though the area around Mediterranean Sea has the great extent of this type of agriculture, the best developed form of this peculiar type of climate is infact found in central Chile.
Strong, cold up-welling currents bathe the coastal regions with cool marine air and moderate winter temperatures, except for the Mediterranean Basin and South and Western Australia.

Dry, warm summer with off shore trade winds

The summer months have relatively higher temperature, with highest temperature recorded are away from the coast & in more eastern continental Mediterranean.
In summers, when the sun is overhead at the Tropic of Cancer, the belt of influence of westerlies is shifted a little polewards.
Rain bearing winds, therefore, are not likely to reach Mediterranean lands.
The prevailing trade winds are off shore; as all of the Mediterranean region lies on the western margin of the continents except large portions of the Mediterranean Basin; and all the regions are situated along the coast of oceans or the Mediterranean Sea, therefore the air is dry, heated & is of low relative humidity with practically no rains.
Days are excessively warm in the interiors & prolonged droughts are common, with areas at coast getting relief from moderating effects of the seas.

A concentration of rainfall in winter with on shore Westerlies

The Mediterranean lands receive most of their precipitation in winters, when the westerlies shift equatorward, with average temp. in winters approx.
In the northern hemisphere, the prevailing on shore westerlies brings much cyclonic rain from from the Atlantic to the countries bordering Mediterranean Sea.
The mean annual rainfall is approx. 70 cm, which differs greatly from place to place, depending on the relief, continentality & passing of the cyclones.
Mediterranean regions are often backed by mountains along the coasts which provide an effective barrier to oncoming westerlies.
As a result, Portuguese coast is much wetter than eastern Spain & much heavier precipitation has been recorded in highlands of windward slopes facing the westerlies.
The steep hills of the eastern Adriatic are the rainiest part of Europe.
Rain comes in heavy showers but only on few days, with bright sunny periods between them; mostly from Sep – Feb, with peak at October.
Though the downpour is infrequent, they are often very torrential & in mountainous regions, cause destructive floods.

The Prominence of local winds around Mediterranean Sea

Many local winds, some hot, others cold are common around the Mediterranean Sea due to the varied topography of the region
High Alps in the north, Sahara desert in south, Continental interiors in east & open Atlantic on west, give rise to great differences in temperature, pressure & precipitation
The passing cyclones from the Atlantic, the anticyclones from the north & cold air masses from the continental interior are often interrupted by relief features, resulting in birth of local winds around the Mediterranean

Sirocco Wind

This is a hot, dry, dusty wind which originates in the Sahara desert
Though it may occur at any time of the year, but most frequent in springs & lasts only for few days
Sirocco blows outward from the desert interior to the cooler Mediterranean Sea
It is usually associated with depressions from Atlantic passing from the coast to eastward inlands
After crossing the Mediterranean Sea, Sirocco is slightly cooled by absorption of water vapour but still remains hot & dry with a temperature of over 40*C
It withers crops & vegetation; and the damage is particularly serious when it comes at the times during which Vines & Olives are in blossom
Sirocco is also known as blood rain due to the red dust it carries from Sahara Desert
It is so prominent that it is known by different local names such as –

Chili	Tunisia
Ghibli	Libya
Leveche	Spain
Khamsin	Egypt & Malta

In Adriatic & Aegean Sea, this hot wind, better known as Gharbi, gathers much moisture, causing fog, dew & rains

Mistral Wind

In contrast to Sirocco, Mistral is a cold wind from the north, rushing down the Rhone valley (France) in violent gusts between 40 – 80 miles / hour.
Velocity of Mistral is intensified by the funneling effect in the valley between Alps & Central Massif (France).
In winters, when the Mistral is most frequent, the temperature of the wind may be below freezing point, though the sky may be clear & cloudless.
Therefore, as a protective measure, many of the houses & orchards of Rhone valley & Riviera have thick rows of trees & hedges planted to shield them from Mistral.

Bora Wind

A similar type of cold north-easterly wind experienced along the Adriatic coast is called Bora
Like the Mistral, it is caused by a difference in pressure between continental Europe & Mediterranean
Usually occur in winter, when the atmospheric pressure over continental Europe is higher than that of Mediterranean
This dry, icy wind is even more violent than the Mistral & speeds of over 100 mph have been recorded
During strong Boras, ships may be blown aground & agricultural land ruined.

Natural vegetation

In a land with half the year dry, one cannot expect the natural vegetation to be luxuriant.
In the Mediterranean area, the natural vegetation is xerophyte, or drought resistant
Consists of cypress, cork oak, scrub evergreen, olive, and low bushes
The native vegetation of Mediterranean climate lands must be adapted to survive long, hot summer droughts and prolonged wet periods in winter.
Trees with small broad leaves are widely spread & never very tall
The absence of shade is a distinct feature of Mediterranean lands.
Soil is often reddish in colour, indicating high iron content.
The low amounts of rain in this region result in little leaching of the soil, and the humus content is low from lack of leaf fall.
Growth is slow in cooler & wetter season, even though more rain falls in winter; & long summer drought checks the growth
Thus growth is almost restricted to autumn & spring, when the temperature is higher & moisture is just sufficient.

Mediterranean Evergreen Forests

Open Woodlands with evergreen oaks, found only in climatically most favored regions with rainfall well over 70 cm viz. Spain & Portugal.
In Australia, eucalyptus forests replace the evergreen oaks
Trees are normally low, even stunted with massive trunks
Have deeply fissured barks, small leathery leaves & wide spread root system in search of water

Evergreen Coniferous Trees

Include various kinds of pines, cedars & cypresses with needle shaped leaves & tall, straight trunks.
They appear more on cooler highlands & where droughts are less severe.

Mediterranean Bushes & Shrubs

Perhaps the most dominant type of Mediterranean vegetation as summers are so dry & hot that in places, forests give place to short, evergreen shrubs & bushes, which are scattered in clamps & are often thorny.
Are generally drought & heat resistant & have developed various strategies of growth & usage of available water during the dry period
They are usually known by different names in different regions such as –

Maquis	Mediterranean
Chaparral	California
Matorral	Chile
Fynbos	South Africa
Mallee and kwongan	Australia

Grass

Conditions in Mediterranean do not suit grass, as most of the rain comes in cool season when growth is slow.
Slow growing vegetation, which cannot replenish their foliage readily, & without deep penetrating roots, is least suitable here.
Even if grass do survive, they are wiry & bunchy and are not suitable for animal farming; Cattle rearing is thus unimportant in Mediterranean.
Grass which is replaced by certain drought resistant varieties of shrubs & flowering herbs, can however support sheep or goats.
As a result of above mentioned facts, animal fats are unimportant here & chief cooking oil is obtained from olives; Dairy products are net import items.

Economic development of the Mediterranean Regions

Mediterranean lands are famous for citrus fruits cultivation, Cereal growing & Wine making majorly.

Orchard Farming

Mediterranean lands are also known as world’s orchard lands
Wide varieties of citrus fruits such as oranges, lemons, limes, citrons & grapefruit are grown.
The fruit trees have long roots to draw water from considerable depths during the long summer drought; in exceptionally dry areas, irrigation helps to relieve the lack of moisture.
The thick leathery skin of citrus fruits prevents excessive transpiration & the long, sunny summer enables the fruits to be ripened & harvested.
The Mediterranean lands account for 70 % of world’s export of citrus fruits.
The olive tree is probably the most typical of all Mediterranean cultivated vegetation
As Olive tree is so hard & long rooted that it can survive even on very poor limestone soils, with less than 25 cm of annual rainfall.
Besides olives, many nut trees like chestnuts, walnuts, hazelnuts & almonds are grown, picked as fruits or for chocolate industry.
Other important fruits are peaches, apricots, pears, plums, cherries & figs.

Crop Cultivation

Cereals are by far the most important cultivated crops in Mediterranean, with wheat as the leading food crop, used for bread making
Barley is the next most important cereal
Other food products like spaghetti, vermicelli & macaroni
Farmers usually sow the seeds in autumn, so that they can grow & germinate steadily with coming winter rain; by springs there is still sufficient moisture for wheat to mature
Other important food crops cultivated here are rice, vegetables especially beans, & flowers, for local market
A little cotton & tobacco are also grown
The mountain pastures, with cool climate, support a fur sheep, goats & sometimes cattle with widespread practice of Transhumance

Wine Cultivation

A specialty of the Mediterranean countries
The regions bordering Mediterranean Sea account for 3/4^thof the total world’s production of wine
The long, sunny summer allow grapes to ripen with almost 85 % of grapes produced go into wine production

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