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Heat of Earth – Temperature , Temperature Inversion Insolation and its distribution :

Heat of Earth – Temperature , Temperature Inversion Insolation and its distribution :

The Earth’s surface receives most of its energy in short wavelengths. The Energy received by the earth is known as incoming solar radiation which in short is termed as insolation.

The factors that cause these variations in insolation are :

  1. Rotation of earth on its axis – Earth’s axis makes an angle of 66 1/2 degree with the plane of its orbit round the sun has a greater influence on the amount of insolation received at different latitudes.
  2. Angle of Inclination of sun’s rays – This depends on the latitude of a place. The higher the latitude the less is the angle they make with the surface of the earth resulting in slant sun rays. If more area is covered, the energy gets distributed and the net energy received per unit area decreases.
  3. Length of the day
  4. Transparency of the atmosphere – Atmosphere is transparent to short wave solar radiation. Within the troposphere water vapour, ozone and other gases absorb much of the near infrared radiation
  5. Configuration of land in terms of its aspect

Last two however, have less influence.

Maximum insolation is received over the subtropical deserts, where the cloudiness is the least. Equator receives comparatively less insolation than the tropics.

Generally, at the same latitude the insolation is more over the continent than over the oceans.

Heating and Cooling of Atmosphere :

  • Conduction:

Conduction takes place when 2 bodies of unequal temperature are in contact with one another, there is a flow of energy from the warmer to cooler body. The transfer of heat continues until the both the bodies attain the same temperature or the contact is broken.

Conduction is important in heating the lower layers of the atmosphere.

The earth after being heated by insolation transmits the heat to the atmospheric layers near to the earth in long wave form. The air in contact with land gets heated slowly and since air is very poor conductor of heat, transfer of heat is only effective upto a few metres in the lower atmosphere.

 

 

  • Convection :

The transfer of heat energy through the movement of a mass of substance from one place to another place is called convection.

Process- The earth’s surface gets heated after receiving insolation from the sun. Consequently , the air coming in contact with the warmer earth’s surface also gets heated and expands in volume. Thus, warmer air becomes lighter and rises upward and a vertical circulation of air is set in. Conversely, the relatively colder air aloft becomes heavier because of contraction in volume and thus descends to reach earth’s surface. The whole mechanism of ascent of warmer air and descent of colder air generates convection currents in the lower atmosphere

The Convective transfer of energy is confined only to the Troposphere.

  • Advection:

The Transfer of heat through horizontal movement of air is called advection. Horizontal movement of air is relatively more important than vertical movement.

Dirunal  (day and night ) variations in Middle latitude, ‘Loo’ – summer season local winds in northern india are the outcome of advection process.

  • Terrestrial Radiation :

The insolation received by the earth is in short waves forms and heats up its surface. The earth after being heated itself becomes a radiating body and it radiates energy to the atmosphere in long wave form. This energy heats up the atmosphere from below. This process is known as terrestrial radiation.

The long wave radiation is absorbed by the atmosphere gases particularly by Carbon Dioxide and other green house gases. Thus, the atmosphere is indirectly heated by the earth’s radiation. The atmosphere in turn radiates and transmits heat to the space. Finally the amount of heat received from the sun is returned to space, thereby maintaining constant temperature at the earth’s surface and in the atmosphere.

Heat Budget / Heat Balance of the Earth : A heat budget is the perfect balance between incoming heat absorbed by earth and outgoing heat escaping it in the form of radiation. If the balance is disturbed, then earth would get progressively warmer or cooler with each passing year.

 

Temperature : It is referred to be amount of heat present in the atmosphere involving outgoing terrestrial radiation as its principal source where as incoming solar radiation forms the secondary source.

 

 

 

Factors controlling Temperature Distribution :

  1. Latitude – The Temperature of a place depends on the insolation received. As explained earlier that the Insolation varies according to the latitude hence the temperature also varies accordingly.
  2. Altitude – The temperature generally decreases with increasing height. The rate of decrease of temperature with height is termed as the Normal Lapse Rate. It is 6.5 degree Celsius per 1000 m.
  3. Distance from Sea – Compared to land, the sea gets heated slowly and loses heat slowly. Land heats up and cools down quickly. Therefore, the variation in temperature over the sea is less compared to land.
  4. Air -Mass and Ocean currents– The places that come under the influence of warm air-masses experience higher temperature and the places that come under the influence of cold air-masses. Similarly, the places located on the coast where the warm ocean current flow record high temperature than the places located on coast where cold ocean current flow.
  5. Local Aspects

Temperature Inversion:

  • Under certain conditions the situation where temperature decreases with increasing height is reversed and the Normal Lapse Rate is inverted which is known as Temperature Inversion.
  • The mechanism of temperature inversion is more strongly applicable during low sun season when the process of conduction throughout the long winter nights generates cold air column in contact with it, With air being poor conductor of heat , significantly warm air column present over it. For development of such inversion other fundamental requirements includes cloudless night and still air.
  • Over the Polar region areas, the temperature inversion is normal throughout the year.
  • Surface inversion promotes stability in the lower layers of the atmosphere.
  • Smoke and dust gets collected beneath the inversion layer and spread horizontally to fill the lower strata of atmosphere. Dense Fog is common occurrence in the morning especially during winter season.
  • The inversion in hills and mountains takes place due to Air drainage. Cold air produced during night flows under the influence of gravity. Being heavy and dense, cold air acts like water and moves down the slope & gets piled up deeply in pockets & valley bottoms with warm air above. This regular sequence of inversion relates to range of economic benefits as it facilitate favourable sun rays to the mountain wall which supports cultivation , human settlement, tourism in such mountainous region.

Distribution of Temperature :

  • The temperature distribution is generally shown on the map with the help of isotherms. Isotherms are lines joining places having equal temperature.
  • In general the effect of the latitude on temperature is well pronounced on the map, as the isotherms are generally parallel to the latitude. The deviation from this general trend is more pronounced in January than in July, especially in the northern hemisphere.
  • In the northern hemisphere the land surface area is much larger than in the southern hemisphere. Hence, the effects of land mass and the ocean currents are well pronounced.
  • In January the isotherms deviate to the north over the ocean and to the south over the continent
  • The effect of the ocean in well pronounced in the southern hemisphere. Here the isotherms are more or less parallel to the latitudes and variations in temperature is more gradual than in the northern hemisphere.
  • In July the isotherms generally run parallel to the latitude.
  • The highest temperatures in july are in the northern hemisphere ; in January they are in the southern hemisphere.

Geographical Discoveries

Geographical Discoveries

Geographical exploration holds a very important place in the history of Europe and even in the world history.

Why did Europeans take to the  Sea? What made the civilization of the Renaissance and Reformation turn to discovery?

What made the civilization of the Renaissance turn to discovery? Something drove Europeans out of their native lands in order to contact other lands.There could be four motives.

The first motive was perhaps the willingness or the courage to learn and understand other cultures. This idea naturally follows from what we accept as fundamental to the Renaissance in general — a willingness to experience and observe as much as possible. In other words, man’s curiosity was a prime motive to know as much about the world as possible.

A second motive or explanation for this age of discovery was religious in origin. In this respect, the age is also connected to the idea of the Crusades of the 12th and 13th centuries. There was evident throughout Europe a religious desire to save souls. After 1415, Portuguese explorers were told to search for Christians on the African coast but they found none.

A third motive was economic. Western Christendom felt itself to be shrinking and decaying at a time when Islam seemed to be enlarging its domain. Europe was exposed to attacks from the infidel east. Europeans also knew and agreed that the Far East was rich in luxuries. They knew this in their daily lives – -they assumed that these luxuries were in the East, just waiting to be taken by those adventurous and courageous enough to make the voyage. It was the Spanish who embraced the simple desire for gold and silver.

A final motive was political, economic and cultural in nature. We tend to speak of imperialism when we observe nations conquering other lands and the 15th century was no exception. As naval technology advanced, and as Europeans settled down to the notion that there was a much larger world at their disposal, they naturally made the attempt to colonize foreign lands.

The Portugese

In 1419, Prince Henry the Navigator (1394-1460), the son of King João of Portugal, began to subsidize sailors, mapmakers, astronomers, shipbuilders and instrument makers who were interested in discovering new lands. These sailors did not succeed but they were successful in advancing down the west African coast, where they began to open a rich trade in gold and slaves.

In 1488, the Portuguese captain, Bartholomeu Dias (c.1450-1500), returned to Lisbon after having sailed to the east coast of Africa, passing the Cape of Storms, later renamed the Cape of Good Hope. Dias probably would have reached India had his crew not mutinied and forced him to return to Portugal.

In the 1490s, Vasco de Gama (c.1460-1524) also rounded the Cape of Good Hope and ventured as far as the Indian Ocean. The holds of his ships were swollen with spices from the East. Portuguese ambitions were at their peak by 1500.

Over the next twenty-five years, Portugal built an empire that remained entirely dependent on sea power. Rather than colonize its new territories, Portugal set up trading depots from West Africa to China, and made little attempt to conquer these lands by force. The Portuguese set up military outposts with the sole task of protecting their investments.

Over time, Antwerp replaced Lisbon as the European center of the spice trade. The Portuguese were eventually to make greater gains in the accidental discovery of Brazil in 1500, than they did through the spice trade in the Far East.

The Spanish — It was the Spanish who rode the second wave of expansion and exploration, but unlike Portugal, Spain founded its empire on conquest and colonization, and not trade. Perhaps the most important of the Spanish endeavors was that of Christopher Columbus (1451-1506).

His plans were accepted by King Ferdinand and Isabella in April 1492. A contract was drawn up on April 30, a contract which specified that Columbus would be designated the Admiral of the Ocean Sea. The contract also stated that Columbus would have control of all the lands he founded and 10% of all the riches. These rights were to be guaranteed and inherited by him and his family forever. He would also be admitted to the Spanish nobility.

In August 3, 1492, Columbus set sail on his first voyage in command of the Santa Maria and attended by two smaller ships, the Pinta and Nina. After thirty-three days at sea, Columbus sighted Watlings Island in the Bahamas. He then visited Cuba and Hispaniola.

In total his discoveries include Dominca in the West Indies, Virgin Islands and Puerto Rico. Cuba , Hispaniola ,Trinidad and Margarita.

Other Spanish discoveries followed those of Columbus. On September 1, 1513, Vasco Nunez de Balboa (1475-1519) left the Spanish settlement of Santa Maria de la Antigua with 200 men and a thousand Indians and crossed the isthmus of Panama. Three weeks later, Balboa climbed to the peak of a mountain, and saw the “South Sea.” Four days later, he  reached the Pacific Ocean and claimed all lands that it touched for Spain.

In 1519, the Portuguese sailor, Ferdinand Magellan (c.1480-1521), left Spain with five ships. He threaded the straits of Cape Horn at the tip of South America and reached the Pacific Ocean. He was killed during an expedition at Zebu in the Philippines on April 27, 1521, but his ship, the Victoria, returned to Spain with eighteen crew members, on September 6, 1522, thus completing the first circumnavigation of the globe

In 1519, Hernando Cortés (1485-1547) set out to conquer the Aztec civilization of Mexico. After a series of battles lasting more than a year, the conquistador Cortés brought Central and parts of South America under Spanish control and domination. His success was partly the result of obtaining allies from tribes that the Aztecs had conquered previously. The human cost was immense — in a period of thirty years, the Aztec population had been reduced from 25 million to 2 million people. Francesco Pizarro (1474-1541) conquered the Incan Empire of Peru. Gold and silver flooded back to Spain, especially after the huge silver deposit at Potosi was discovered.

Impact

The gains of overseas exploration of the New World were immense.

  • Gold and silver flooded into Europe, especially into Spain and ultimately into the hands of Italian and German bankers and merchants. Economic conditions seemed to be improving and the population was increasing. But with this wealth came poverty as investors and businessmen sought to take advantage of their new found wealth.
  • As the medieval moneylender could not meet the requirements of trade and commerce, the banking system was evolved. Joint stock companies also came into existence, which made large-scale operations possible
  • The other gain was the simple fact of an awareness of new parts of the globe. The intellectual area which was the root of the changes and which impacted other areas. As the discoveries expanded the learning and knowledge of the world the outlook and the attitude of men changed. When the ideas of the New World influenced the Europeans the effects were seen in their understandings of the human kind. The spirit of learning and inquiry brought revolutionary changes in the lives of the people throughout Europe.

If the Age of Discovery did anything, it restored the self-confidence of Europe, and in turn, Europe rediscovered itself.

 

 

 

Distribution of Oceans and continents-Continental Drift and evidence

Distribution of Oceans and continents-Continental Drift and evidence

Theory of Origin of continents and ocean basins:

1.Wegner Theory:

  • Wegner gave the theory of continental drift in 1915.He stated that all the continents formed a single continental mass called PANGEA,which meant all earth and the pangea was surrounded by a mega ocean called PANTHALASA,meaning all water.
  • During the Jurassic era,about 200 million years ago,the pangea started to split.It first broke into two continental masses-Laurasia and Gonwana,forming nothern and southern components respectively.
  • Later,the continental masses began to split further to form the present day continents.
  • Thus,he proposed that the continents are floating and constantly drifting,which became the basis of Plate Tectonics theory.

Evidences of movement of continents:

  • Mathching of continents(Jig-saw fit)
  • Geological evidence of identical mountains of eastern and western coasts of atlantic sea.
  • Evidences of carboniferous glaciations show that the landmasses once had similar climatic conditions which is possible only if they were contiguous.

 

  1. Plate Tectonics:

It substantiates the concept of continental drift theory based on evidences of Sea floor spreading and Paleomagnetism. This theory explains various natural events such as mountain building, folding and faulting, continental drift, earthquakes and vulcanism.

It identifies 7major and 20 minor lithospheric plates. The major plates are-Eurasian, African, Indo-Australian, Pacific, North American, South American and Antarctic plates. Plate tectonics explains that it is the plates that are in motion and hence the continents that form a part of them also happen to move.

Plate margins or boundaries are divided into three types

a)Constructive or Divergent plate margins-pulling apart of plates which causes sea floor spreading.Shallow earthquakes are associated with it.

e.g-growth of atlantic ocean.

b)Destructive or Convergant plate margin-movement of two plates towards each other.This could be

i)ocean-continent collision-leads to formation of great mountain ranges.

ii)continent-continent collision-leads to crustal thickening,closing of ocean floor separating the two continents and folding causes formation of highlands.

iii)ocean-ocean collision-deep oceanic trenches,island arcs are found.

c)Transform or conservative plate movement-plates slide past each other along a vertical fracture called the tranform fault

Evidences for plate tectonics:

  • Continuous eruption of lava and volcanoes along mid oceanic ridges.
  • Rocks equidistant on either side of the crest of mid oceanic ridges show similarities in terms of period of formation,chemical and magnetic properties.
  • Age of oceanic crust rocks are younger than continental rocks.
  • Thin occeanic sediments.
  • Deep oceanic trenches.

Climate – Composition and Structure of Atmosphere

Climate – Composition and Structure of Atmosphere

 

The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth’s gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).

Composition of the Atmosphere

The atmosphere is composed of gases, water vapour and dust particles. Nitrogen, Oxygen, and Argon, which together constitute the major gases of the atmosphere. The proportion of gases changes in the higher layers of the atmosphere.

Constituent Percentage
Nitrogen 78.08
Oxygen 20.95
Argon 0.93
Carbon dioxide 0.036
Neon 0.002
Helium 0.0005
Krypton 0.001
Xenon 0.00009
Hydrogen 0.00005

 

Water Vapour :

  • Water Vapour is also a variable gas in the atmosphere, which decreases with altitude.
  • Water vapour also decreases from the equator towards the poles.
  • It also absorbs parts of the insolation from the sun and preserves the earth’s radiated heat.
  • Water vapour also contributes to the stability and instability in the air

Dust Particles:

  • Dust particles are generally concentrated in the lower layers of the atmosphere; yet, convectional air currents may transport them to great heights.
  • Dust and salt particles act as hygroscopic nuclei around which water vapour condenses to produce clouds.

Structure of the Atmosphere

The atmosphere consists of different layers with varying density and temperature. Density is highest near the surface of the earth and decreases with increasing altitude.

The column of atmosphere is divided into 5 different layers depending upon the temperature condition. They are :

  1. Troposphere
  2. Stratosphere
  3. Mesosphere
  4. Ionosphere
  5. Exosphere

 

Troposphere:

  • The troposphere is the lowest layer of Earth’s atmosphere. It extends from Earth’s surface to an average height of about 13 km, although this altitude actually varies from about 8km at the poles to 18km at the equator.
  • Thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents.
  • This layer contains dust particles and water vapour.
  • All changes in weather and climate take place in this layer.
  • The temperature in this layer decreases at the rate of 1 degree Celsius for every 165m of height.
  • This is the most important layer for all biological activity.

The Zone separating the troposphere from stratosphere is known as the tropopause. The air temperature at the tropopause is about -80 degree Celsius over the equator and about -45 degree Celsius over the poles. The temperature here is nearly constant and hence the name tropopause.

Stratosphere:

  • The Stratosphere is found above the tropopause and extends up to a height of 50 km.
  • One important feature of this layer is that it contains the Ozone layer. This layer absorbs ultra-violet radiation and shields life on the earth from intense, harmful form of energy.

Mesosphere:

  • The Mesosphere lies above the stratosphere, which extends up to a height of 80 km.
  • In this layer, Temperature starts decreasing with the increase in altitude and reaches up to -100 degree Celsius at the height of 80 km.

The upper limit of Mesosphere is known as the Mesopause.

Ionosphere:

  • The Ionosphere is located between 80 to 400 km above the Mesopause.
  • It contains electrically charged particles known as ions, and hence, it is known as ionosphere.
  • Radio waves transmitted from the earth are reflected back to the earth by this layer
  • Temperature here starts increasing with height.

Exosphere:

  • The uppermost layer of the atmosphere above the ionosphere is known as exosphere.
  • Whatever contents are here, these are extremely rarefied in this layer and it gradually merges with the outer space.
  • Here Temperature decreases with increasing height.

 

ATMOSPHERIC CIRCULATION : PRESSURE, VERTICAL AND HORIZONTAL DISTRIBUTION

ATMOSPHERIC CIRCULATION : PRESSURE, VERTICAL AND HORIZONTAL DISTRIBUTION

Atmospheric Pressure:

       The weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere is called the atmospheric pressure. The  atmospheric pressure is expressed in units of mb and Pascals. At sea level the average atmospheric pressure is 1,013.2 mb or 1,013.2 hPa. Air pressure is measured with the help of a mercury barometer or the aneroid barometer.

Vertical  Distribution of Air Pressure :

 

The columnar distribution of atmospheric pressure is known as vertical distribution of pressure. Air pressure decreases  with  increase  in  altitude  but  it  does  not  always  decrease  at  the same rate. Dense components of atmosphere are found in its lowest parts near the  mean sea  level.

The higher the density of air, the greater is the air pressure and vice versa. The mass of air above in the column of air compresses the air under it hence its lower layers are more dense than the upper layers; As a result, the lower layers of the atmosphere have higher density, hence, exert more pressure. Conversely, the higher layers are less compressed and, hence,they  have  low  density  and  low  pressure.

Temperature of  the air,  amount of  water vapour present in the air and gravitational pull of the earth determine the air pressure of a given place and at a given time. Since these factors are variable with change in height, there is a variation in the rate of decrease in air pressure with increase in altitude. The normal rate of decrease in air pressure is 34millibars  per  every  300  metres  increase in  altitude.  The effects of low pressure are more clearly experienced by the people living in the hilly areas as compared to those who live in plains.

 

Horizontal Distribution of  Air Pressure :

The distribution of atmospheric pressure over the globe is known as horizontal distribution of pressure. It is shown on maps with the help of isobars.

Anisobar is a line connecting points that have equal values of pressure. Isobarsare analogous to the contour lines on a relief map. The spacing of isobars expresses the rate and direction of change in air pressure. This charge in air pressure is referred to pressure gradient.

Pressure gradient is the ratio between pressure difference and the actual horizontal distance between two points.Close spacing of isobars expresses steep pressure gradient while wide spacing indicates gentle pressure gradient.

The  horizontal  distribution  of  atmospheric  pressure  is  not  uniform  in  the world. It varies from time to time at a given place; it varies from place to place  over  short  distances.

The  factors  responsible  for  variation  in  thehorizontal distribution of pressure are as follows:

(i) Air temperature

(ii) The earth’s rotation

(iii) Presence of water vapour

 

  • Air Temperature:

 

The earth  is  not  heated  uniformly  because  of  unequal  distribution  of insolation, differential heating and cooling of land and water surfaces.Generally there is an inverse relationship between air temperature and air pressure. The higher the air temperature, the lower is the air pressure.The fundamental rule about gases is that when they are heated, they become less dense and expand in volume and rise. Hence, air pressure is low in equatorial regions and it is higher in polar regions. Along the equator  lies  a  belt  of  low  pressure  known  as  the  “equatorial  low  or doldrums”. Low air pressure in equatorial regions is due to the fact that hot  air  ascends  there  with  gradual  decrease  in  temperature  causing thinness of air on the surface. In polar region, cold air is very dense hence it descends and pressure increases. From this we might expect, a gradual increase in average temperature thords equator. However, actual readings taken on the earth’s surface at different places indicate that pressure does not increase longitudinally in a regular fashion from equator to the poles. Instead, there are regions of high pressure in subtropics and regions of low pressure in the subpolar areas.

(ii) The Earth’s Rotation: The earth’s rotation generates centrifugal force.

This  results  in  the  deflection  of  air  from  its  original  place,  causing decrease of pressure. It is believed that the low pressure belts of the sub polar regions and the high pressure belts of the sub-tropical regions are created as a result of the earth’s rotation. The earth’s rotation also causes convergence  and  divergence  of  moving  air.  Areas  of  convergence experience low pressure while those of divergence have high pressure.

(iii) Pressure of Water Vapour: Air with higher quantity of water vapour

has lower pressure and that with lower quantity of water vapour has

higher pressure. In winter the continents are relatively cool and tend todevelop high  pressurecentres; in summer  they stay warmer  than theoceans and tend to be dominated by low pressure, conversely, the oceansare associated with low pressure in winter and high pressure in summer.

Atmospheric Circulation:

The circulation of wind in the atmosphere is driven by the rotation of the earth and the incoming energy from the sun. Wind circulates in each hemisphere in three distinct cells which help transport energy and heat from the equator to the poles. The winds are driven by the energy from the sun at the surface as warm air rises and colder air sinks.

 

1.Hadley Cell :

 

The circulation cell closest to the equator is called the Hadley cell.  Winds are light at the equator because of the weak horizontal pressure gradients located there.   The warm surface conditions result in locally low pressure.  The warm air rises at the equator producing clouds and causing instability in the atmosphere.  This instability causes thunderstorms to develop and release large amounts of latent heat.  Latent heat is just energy released by the storms due to changes from water vapor to liquid water droplets as the vapor condenses in the clouds, causing the surrounding air to become more warm and moist, which essentially provides the energy to drive the Hadley cell.

The Hadley Cell encompasses latitudes from the equator to about 30°.  At this latitude surface high pressure causes the air near the ground to diverge.  This forces air to come down from aloft to “fill in” for the air that is diverging away from the surface high pressure. The air flowing northward from the equator high up in the atmosphere is warm and moist compared to the air nearer the poles. This causes a strong temperature gradient between the two different air masses and a jet stream results. At the 30° latitudes, this jet is known as the subtropical jet stream which flows from west to east in both the Northern and Southern Hemispheres. Clear skies generally prevail throughout the surface high pressure, which is where many of the deserts are located in the world.

Wind Directions

From 30° latitude, some of the air that sinks to the surface returns to the equator to complete the Hadley Cell. This produces the northeast trade winds in the Northern Hemisphere and the southeast trades in the Southern Hemisphere. The Coriolis force impacts the direction of the wind flow. In the Northern Hemisphere, the Coriolis force turns the winds to the right. In the Southern Hemisphere, the Coriolis force turns the winds to the left.

Ferrel cell :

From 30° latitude to 60° latitude, a new cell takes over known as the Ferrel Cell. This cell produces prevailing westerly winds at the surface within these latitudes. This is because some of the air sinking at 30° latitude continues traveling northward toward the poles and the Coriolis force bends it to the right (in the Northern Hemisphere). This air is still warm and at roughly 60° latitude approaches cold air moving down from the poles. With the converging air masses at the surface, the low surface pressure at 60° latitude causes air to rise and form clouds. Some of the rising warm air returns to 30° latitude to complete the Ferrel Cell.

The two air masses at 60° latitude do not mix well and form the polar front which separates the warm air from the cold air. Thus the polar front is the boundary between warm tropical air masses and the colder polar air moving from the north.

3.Polar Front:

The polar jet stream aloft is located above the polar front and flows generally from west to east. The polar jet is strongest in the winter because of the greater temperature contrasts than during the summer.  Waves along this front can pull the boundary north or south, resulting in local warm and cold fronts which affect the weather at particular locations.

Above 60° latitude, the polar cell circulates cold, polar air equatorward. The air from the poles rises at 60° latitude where the polar cell and Ferrel cell meet, and some of this air returns to the poles completing the polar cell. Because the wind flows from high to low pressure and taking into account the effects of the Coriolis force, the winds above 60° latitude are prevailing easterlies.

Walker Circulation

In contrast to the Hadley, Ferrel and polar circulations that run along north-south lines, the Walker circulation is an east-west circulation.  Over the eastern Pacific Ocean, surface high pressure off the west coast of South America enhances the strength of the easterly trade winds found near the equator.

The winds blow away from the high pressure toward lower pressure near Indonesia. Upwelling, the rising of colder water from the deep ocean to the surface, occurs in the eastern Pacific along South America near Ecuador and Peru.

This cold water is especially nutrient-rich and is stocked with an abundance of large fish populations. By contrast the water in the western Pacific, near Indonesia, is relatively warm. The air over Indonesia rises because of the surface low pressure located there and forms clouds. This causes heavy precipitation to fall over the western tropical Pacific throughout the year.

The air then circulates back aloft towards the region above the surface high pressure near Ecuador and this becomes the Walker circulation. The air sinks at this surface high pressure and is picked up by the strong trade winds to continue the cycle.

El Nino

On some occasions, the Walker circulation and the trade winds weaken, allowing warmer water to “slosh back” towards the eastern tropical Pacific near South America.  The warmer water will cover the areas of upwelling, cutting off the flow of nutrients to the fish and animals that live in the eastern Pacific Ocean.  This warming of the eastern Pacific Ocean is known as El Niño.  The warmer water will also serve as a source for warm, moist air which can aid in the development of heavy thunderstorms over the mass of warm water.

How does this relate to agriculture?

Changes in the Hadley cell and Walker circulation can result in dramatic climate variations for many regions. In an El Niño winter, for example, the presence of the warm water in the eastern Pacific shifts the position of the subtropical jet, leading to heavy rainfall in Florida and southern Georgia.

In a warming climate, the Hadley cell could increase in length and alter the climate of regions around 30°. For example, many deserts in the northern hemisphere are located around the 30° latitude, and if the Hadley cell were to increase in length, that could cause dry conditions to move north of 30°. Ultimately, this would alter the precipitation patterns of many regions, including the Southeast.

Asia:Eastern and South-Eastern Island groups

Asia:Eastern and South-Eastern Island groups

Recent Issues:

  • Japan Information and Study center has been set at Ahmedabad Management Association (AMA).The centre is an attempt to cement the Indo-Japanese relationship.
  • Japan is working closely on India’s infrastructure development projects such as DMIC.
  • PM of India visited Japan.
  • MOU signed to transfrom Varanasi into a smart city on line of the Kyoto city
  • Japan pledged to invest Rs. 2.1 lakh crore ($35.5 billion) in a wide spectrum of projects in India over five years,include infrastructure , clean energy,skill development
  • Also to double the number of Japanese companies operating in India in five years.
  • Japan expressd its readiness to provide financial,technical and operational support to introduce the Shinkansen, or bullet train, along the Ahmedabad-Mumbai route.
  • Japan also supported India’s entry as a full member of the Nuclear Suppliers Group.
  • The Stratergic and Global Patnership is turned into Special Strategic and Global Partnership”.

Physical Geograhpy:East Asian Islands:

  • Along the Coast of East Asia, many penninsulas and islands dot the Westernmost Pacific Ocean.
  • Mostly divide the ocean into smaller bodies of water ,including Yellow sea, the Sea of Japan,East China Sea,South China Sea.
  • The South China sea stretches from the Island of Taiwan to the Philippines and the peninsula of Southeast Asia , carries 1\3rd of the world’s shipping traffic.

Japan:

  • Japan is a stratovolcanicarchipelago of 6,852 islands.
  • Four large , mountainous islands and thousands of smaller ones form the archipelago or island chain , of Japan.
  • Honsu is the central and largest island, with Hokkaido to the north and Kyushu and Shikoku to the south.
  • Most of Japan’s major cities are on Honshu.
  • Surrounding Japan are the Sea of Okhotsk on the north, the Sea of Japan and the East China Sea on the west and the Philippine Sea on the South .On the east and South-east is the Pacific Ocean.
  • The country, including all of the islands it controls, lies between latitudes 24° and 46°N, and longitudes 122° and 146°E.
  • About 73 percent of Japan is forested, mountainous, and unsuitable for agriculturalindustrial, or residentialThus, habitable zones , mainly located in coastal areas and are extremely populated.
  • Japan is one of the most densely populated countries in the world.

Natural Calamities that Occur:

  • The islands of Japan are located in a volcaniczone on the Pacific Ring of Fire.
  • These islands are formed as a result of subduction  of the Philippine Sea Platebeneath the continental Amurian Plate and Okinawa Plate to the south and subduction of the Pacific Plate under the Okhotsk Plate to the north.
  • Japan has 108 active volcanoes.Destructive earthquakes, often resulting in tsunami, occur several times each century.
  • The 1923 Tokyo earthquakekilled over 140,000 people.
  • Recent earthquakes are the 1995 Great Hanshin earthquake and 2011 Tohoku earthquake.
  • Due to its location in the Pacific Ring of Fire,Japan is frequently prone to earthquake and tsunami , having the highest natural disaster risk in the developed world.

Climate

Economy

  • From 1868,Japan began to expand ecoomically after embracing market economy.
  • Many of today’s enterprises were founded at the time, and Japan emerged as the most developed nation in Asia
  • As of 2012, Japan is the third largest national economy in the world, after the United States and China, in terms of nominal GDP.

Exports

  • Japan has a large industrial capacity, and is home to some of the largest and most technologically advanced producers.
  • Its mainly produces motor vehicles, electronicsmachine tools, steel and nonferrous metals, ships, chemical substances, textiles, and processed foods
  • Agricultural businesses in Japan cultivate 13 percent of Japan’s land,
  • Japan accounts for nearly 15 percent of the global fish catch, second only to China.
  • Japan’s main export markets were China , the United States , South Korea , Thailand and Hong Kong .
  • Its main exports are transportation equipment, motor vehicles, electronics, electrical machinery and chemicals
  • Japan has a low unemployment rateof around four percent.
  • Some 20 million people, around 17 per cent of the population, were below the poverty line in 2007.

Imports:

Science and technology

  • Japan is a leading nation in scientific research, particularly technology, machinery and biomedical research.
  • It has the third largest budget in the world.
  • Some of Japan’s more prominent technological contributions are in the fields of electronics, automobiles, machinery, earthquake engineeringindustrial roboticsoptics, chemicals, semiconductorsand metals.
  • leads the world in roboticsproduction and use, possessing more than 20% (300,000 of 1.3 million) of the world’s industrial robots as of 2013[
  • The Japan Aerospace Exploration Agency(JAXA) is Japan’s space agency; it conducts space, planetary, and aviation research, and leads development of rockets and satellites

Demographics

  • Japan’s population is estimated at around 127.1 million,[2]with 80% of the population living on Honshū
  • Japanese society is linguistically and culturally homogeneous,composed of 98.5% ethnic Japanese, with small populations of foreign workers.
  • The changes in demographic structure have created a number of social issues, particularly a potential decline in workforce population and increase in the cost of social security benefits like the public pension plan
  • In 2011, Japan’s population dropped for a fifth year, falling by 204,000 people to 126.24 million people.
  • Japan’s population is expected to drop to 95 million by 2050,demographers and government planners are currently in a heated debate over how to cope with this problem
  • Immigration and birth incentives are sometimes suggested as a solution to provide younger workers to support the nation’s aging population

Religion

  • Japan enjoys full religious freedom based on Article 20 of its Constitution.
  • Major religion followed is Buddhism or Shinto .

India and Japan relations:

  • The friendship between India and Japan has a long history rooted in spiritual affinity and strong cultural and civilizational ties.
  • Throughout the various phases of history since civilizational contacts between India and Japan began some 1400 years ago, the two countries have never been adversaries
  • Bilateral ties have been singularly free of any kind of dispute – ideological, cultural or Territorial.
  • The relationship is unique and one of mutual respect manifested in generous gestures and sentiments, and of standing by each other at times of need.
  • The momentum of bilateral ties, however, was not quite sustained as per expectations in the following decades.
  • The beginning of the 21st Century witnessed a dramatic transformation in bilateral ties.
  • in 2000, the Japan-India Global Partnership in the 21st Century was launched providing the much-needed impetus for the trajectory of relations to soar to new heights.
  • The Global Partnership formed the foundation for the strengthening ties in diverse fields, including identifying strategic convergences
  • Japanese companies, such as SonyToyota, and Honda, have manufacturing facilities in India, and with the growth of the Indian economy, India is a big market for Japanese firms.
  • Japanese firms in fact, were some of the first firms to invest in India.
  • In December 2006, Indian Prime MinisterManmohan Singh‘s visit to Japan culminated in the signing of the “Joint Statement Towards Japan-India Strategic and Global Partnership”
  • Japan has helped finance many infrastructure projects in India, most notably the Delhi Metro
  • in the year 2007, the Japanese Self-Defence Forces and the Indian Navy took part in a joint naval exercise in the Indian Ocean, known as Malabar 2007, which also involved the naval forces of AustraliaSingapore and the United States.

Historical relations

  • Cultural exchanges between Indiaand Japan began early in the 6th century with the introduction of Buddhism to Japan from India.
  • The Indian monkBodhisena arrived in Japan in 736 to spread Buddhism and performed eye-opening of the Great Buddha built in Tōdai-ji,
  • Buddhism and the intrinsically linked Indian culturehad a great impact on Japanese culture, still felt today, and resulted in a natural sense of amicability between the two nations

Economic Relations

  • Japan is currently India’s fourth largest source of foreign direct investment;
  • trade and economic patnreship has underperformed
  • Bilateral trade at 16.29 billion dollars 2013-14 forming 2.13% of India’s total trade and 1% of Japan’s
  • Low profile trade esp since Japan has to offer in terms of investment and technology both of which India needs
  • Japanese ODA (Official Development Assistance) India is the largest recipients
  • In terms of FDI in India Japan ranks low and well behind China and accounts 7.46 per cent of total FDI inflows into India

Taiwan

Geography of Taiwan

  • is an island in East Asia;
  • it is located some 180 kilometres (112 miles) off the southeastern coast of Chinaacross the Taiwan Strait
  • has an area of 35,883 km2 (13,855 sq mi) and spans the Tropic of Cancer.
  • TheEast China Sealies to the north, the Philippine Sea to the east, the Luzon Strait directly to the south and the South China Sea to the southwest.
  • Taiwan Island makes up 99% of the territory of the Republic of China (ROC),
  • Taiwan is a tilted fault blockcharacterized by the contrast between the eastern two-thirds, consisting mostly of five rugged mountain ranges parallel to the east coast
  • There are six peaks over 3500 meters, the highest being Yu Shanat 3,952 metres (12,966 ft)
  • Taiwan the world’s fourth-highest island.
  • The tectonic boundary that formed these ranges is still active, and the island experiences many earthquakes, a few of them highly destructive
  • There are also many active submarine volcanoesin the Taiwan Straits.
  • The climate ranges from tropicalin the south to subtropical in the north, and is governed by the East Asian Monsoon
  • The island is struck by an average of four typhoonsin each year
  • The eastern mountains are heavily forested and home to a diverse range of wildlife, while land use in the western and northern lowlands is intensive

Economy and industry

Culture

  • The cultures of Taiwan are a hybrid blend of various sources, incorporating elements of traditional Chinese culture, attributable to the historical and ancestry origin of the majority of its current residents, Japanese culture, traditional Confucianist beliefs, and increasingly Western values.

India–Taiwan relations

  • The bilateral relations between Indiaand Taiwan (Republic of China) have improved since the 1990s despite both nations not maintaining official diplomatic relations.
  • India’s economic & Commercial links as well as people-to-people contacts with Taiwan have expanded in recent years.
  • As a part of its “Look East” foreign policy, India has sought to cultivate extensive ties with Taiwan in trade and investment as well as developing co-operation in science & technology, environment issues and people-to-people exchanges
  • The India-Taipei Association ITAhas been established in Taipei since 1995  to promote non-governmental interactions between India and Taiwan
  • ITA also facilitates business, tourism, scientific, cultural and people-to-people exchanges
    The Taipei Economic & Cultural Centre in New Delhi is ITA’s counterpart organisation in India
  • In 2002, the two sides signed the Bilateral Investment Promotion & Protection Agreement and are discussing the possibility of entering into agreements related to Double Taxation Avoidance and ATA Carnet to facilitate participation in each other’s trade fairs

Cultural exchanges

  • While the ROC and India are two of Asia’s leading democracies, both with fairly close ties to the United Statesand Europe, both sides continue to lack formal diplomatic relations. However, the two governments maintain unofficial ties with each other.
  • According to some sources, Buddhism is the most widely practiced religion in Taiwan, usually alongside elements of Daoism, and Bollywoodfilms have in recent years gained a reasonably popular following, along with other aspects of Indian culture such as yogacuisine and Indian dance.

Southeast Asia

  • vast regionof Asia situated east of the Indian subcontinent and south of China.
  • It consists of two dissimilar portions: a continental projection (commonly called mainland Southeast Asia) and a string of archipelagoes to the south and east of the mainland (insular Southeast Asia).
  • Characteristic of insular (or archipelagic) Southeast Asia are the chains of islands—the Malayand Philippine archipelagoes
  • Earthquakes and volcanic activity are quite common along the entire southern and eastern margin
  • One consequence of the seismic activity is that a large number of lakes are found in the region.
  • The countries in this region include Malaysia, Singapore, Brunei, Indonesia, East Timor, and the Philippines.
  • The physical geography varies from island to island; some have high mountain relief and others are low-lying and relatively flat.
  • Active tectonic plate action in the region causes earthquakes and volcanic activity, resulting in destruction of infrastructure and loss of life; both acutely impact human activities.
  • Tectonic plate activity has been responsible for the existence of the many islands and has created the mountainous terrain of the various countries
  • High mountain ranges can have peaks that reach elevations of over fifteen thousand feet.
  • The island of Borneo, in the center of the insular region, is actually a segment of ancient rock that has been pushed upward by tectonic forces to form a mountainous land mass.
  • The mountains on Borneo have been worn down over time by erosion.
  • The physical geography of the mainland and the insular region is dominated by a tropical type A climate. Cooler temperatures may be found in the mountainous regions and more even temperatures ranges can be found along the coasts.
  • Tectonic plate activity is responsible for the many earthquakes and volcanic eruptions that occur in the realm.

 

Cultural 

  • Southeast Asia was colonized by Europeans and later by Japan.
  • Southeast Asia has a population of more than six hundred million people more than half the population lives on the many islands of Indonesia and the Philippines.
  • Southeast Asia is ethnically, religiously, and linguistically diverse. A number of major ethnic groups dominate in the mainland and insular region but are only examples of the multitude of smaller groups that exist in the realm. One minority group is the overseas Chinese, who immigrated to the realm during the colonial era.
  • The small island of Java in Indonesia is one of the most densely populated places on Earth.
  • The island of Luzon in the Philippines is also one of the more densely populated areas of the insular region
  • The ethnic mosaic of Southeast Asia is a result of the emergence of local differences between people that have evolved into identifiable cultural or ethnic groups
  • Many distinct groups can exist on the many islands of the region.
  • The large number of ethnic groups is dominated by Indonesians, Malays, and Filipinos, coinciding with the countries of Indonesia, Malaysia, and the Philippines.
  • Indonesia is also home to the largest Muslim population in the world.
  • About 95 percent of the people in Thailand and more than 60 percent of the people in Laos are Buddhist.
  • Hinduism is present in the Indonesian island of Bali and in various other locations in the region.

Malaysia

 

  • Malaysia is a country made up of various British colonies that came together as a federation and then became an independent country
  • The two main areas include the western colonies on the Malay Peninsula and the eastern colonies on the island of Borneo.
  • Malaysia has two main land areas separated by the South China Sea. The regions of Sarawak and Sabah, on the island of Borneo, are called East Malaysia;
  • the mainland on the Malay Peninsula is called West Malaysia.

Diversity of Culture and Ethnicity in Malaysia

  • Malaysia’s culture is diverse in that several major religions are practiced within its borders.
  • Islam is considered the official language.
  • Buddhists,christians and Hindu do constitute the the Malaysia.
  • During British colonialism, a number of people from South Asia were brought to Malaysia.
  • For example, Tamils were brought from India to work the plantations.
  • . Their Hindu beliefs were infused into the culture and some Tamils also converted to Christianity.
  • Sikhs were brought from South Asia to help Britain run the country as police, soldiers, or security officers.
  • The Sikhs who came brought their religion with them, which added to the multireligious dynamics of the country.

Economy

  • Malaysia has rapidly advanced its economy in recent decades and is modernizing its infrastructure—roads, bridges, highways, and urban facilities.

Singapore

  • Singapore is similar to Hong Kong in its development.
  • With a good port, Singapore is a hub for ships sailing between Europe and China.
  • It serves Southeast Asia as anentrepôt, or break-of-bulk point, where goods are offloaded from large ships and transported to smaller vessels for distribution to the Southeast Asian community.
  • Singapore has made good strategic utilization of its geographic location by serving as a distribution center for goods and materials processed in the region.
  • Crude oil from Indonesia is unloaded and refined here.
  • Raw materials are shipped in, manufactured into finished products, and then shipped out to global markets
  • Singapore Island is a swampy place with no natural resources
  • All production components, food goods, construction materials, and energy must be imported.
  • Importing everything has raised the cost of living

Indonesia

  • The country of Indonesia is the world’s largest archipelago state, consisting of more than 17,500 islands, about one-third of which are inhabited.
  • Indonesia is the sixteenth-largest country in the world by area
  • The tropical climate and the archipelago nature of the country provide for enormous biodiversity within the environment.
  • Second only to Brazil in its biodiversity, Indonesia is host to an enormous number of unique plants and animals.
  • The habitats of many of these creatures are being encroached upon by human activity.
  • In 2010, the estimated population of Indonesia was about 245 million. Indonesia has the fourth-largest population of any country in the world
  • Agriculture has been the historic base of the Indonesian economy and also the largest employment sector.

Brunei

  • Bordered by Sarawak, the sultanate is actually two small separate regions along the coast of the South China Sea.
  • A major oil and natural gas exporter
  • It provides a high standard of living for its small population.
  • It is called a sultanate because the kingdom has been ruled by sultans (rulers) from the same family for the past six centuries.
  • Brunei is an Islamic State with Islam as its state religion. About two-thirds of the population is Muslim
  • Buddhism is the second-most popular religion.

The Philippines

  • Located on the eastern side of the Southeast Asian community is the archipelago state of the Philippines.
  • The islands of the Philippines are of volcanic origin and have numerous  active volcano.
  • They are mainly mountainous and covered in tropical rainforest.
  • The highest mountain, at 9,692 feet, is Mt. Apo, which is located on the southern island of Mindanao
  • The Philippines can be divided into three main geopolitical regions: Luzon, Visayas, and Mindanao.
  • South East Asia and India
  • From prehistoric days, India has trade relations with South East Asia
  • India sent its traders and missionaries to these regions and in some places these persons also settled.
  • The Association of Southeast Asian Nations (ASEAN) is apolitical and economic organisation of ten countries located in South East Asia
  • Its aims include accelerating economic growthsocial progresssociocultural evolutionamong its members, protection of regional peace and stability, and opportunities for member countries to discuss differences peacefully
  • The Look East policy a multi-faceted and multi-pronged approach to establish strategic links with as many individual countries as possible, evolve closer
  • political links with ASEAN, and develop strong economic bonds with the Region
  • Second, it was an attempt to carve a place for India in the larger Asia Pacific.
  • Third, the Look East policy was also meant to showcase India’s economic potential for investments and trade.
  • A number of institutional mechanisms have been put in place to promote economic exchanges both at the governmental as well as private sector level
  • The ASEAN-India Joint Cooperation Committee and an ASEAN-India Working Group on Trade and Investment were set up along with the creation of an ASEAN-India Fund to promote trade, tourism, science and technology, and other economic activity.

Recent News

  • India to draft 5-year plan of action to deepen ties with ASEAN
  • India and the ASEAN have already implemented a free trade agreement in goods and are set to widen its base and include services and investments. The India-ASEAN Trade in Goods Agreement was signed in August 2009 and it came into force on January 1, 2010.
  • The bilateral trade grew by 4.6 per cent from $68.4 billion in 2011 to $71.6 billion in 2012.
  • ASEAN’s exports were valued at $43.84 billion and imports from India amounted to $27.72 billion in 2012.
  • The target has been set at $100 billion by 2015 for ASEAN-India trade.

India’s Impact on Southeast Asia

  • Southeast Asia which can boast of such magnificent temple cities as Pagan (Burma; constructed from 1044 to 1287 AD,) Angkor (Combodia; constructed from 889 to c. 1300 AD), and the Borobudur (Java, early ninth century AD).
  • Though they were influenced by Indian culture, they are nevertheless part and parcel of the history of those respective countries.
  • Historians have formulated several theories regarding the transmission of Indian culture of Southeast Asia :
  • the ‘Kshatriya’ theory;
    (2) the ‘Vaishya’ theory;
    (3) the ‘Brahmin’ theory.

Sources:

  1. http://www.mea.gov.in/Portal/ForeignRelation/Japan_-_July_2014_.pdf
  2. http://www.worldislandinfo.com/TALLESTV1.htmhttp://news.bbc.co.uk/2/hi/asia-pacific/279170.stm
  3. http://www.c3sindia.org/taiwan/98http://en.wikipedia.org/wiki/India%E2%80%93Japan_relations
  4. http://www.jamestown.org/programs/chinabrief/single/?tx_ttnews%5Btt_news%5D=3561&tx_ttnews%5BbackPid%5D=193&no_cache=1#.VLJOedKUffs
  5. http://2012books.lardbucket.org/books/regional-geography-of-the-world-globalization-people-and-places/s14-southeast-asia.html
  6. http://www.rchss.sinica.edu.tw/capas/publication/newsletter/N27/2704_02.pdf
  7. http://www.thehindu.com/news/national/india-to-draft-5year-plan-of-action-to-deepen-ties-with-asean/article6299015.ece

ASIAN: DESERTS

ASIAN: DESERTS

Desert

Deserts in Asia are characterized by small amount of moisture. They receive an annual average rainfall of ten inches (25 cms) or less, and have an arid or hyperarid climate, characterized by a strong moisture deficit, where annual potential loss of moisture from evapotranspiration well exceeds the moisture received as rainfall.

The desert biome of the earth covers about 35 per cent of the total land area of the world. Deserts are very dry, receiving less than 25cm. The area of the desert biome in Asia are increasing as there is increasing desertification because of human over interaction. Deserts and xeric shrublands occur in all tropical, subtropical, and temperate climate regions. Desert soils tend to be sandy or rocky, and low in organic materials. Soil is generally saline or alkaline.

Adaptations:

Plants and animals in deserts of Asia are adapted to low moisture conditions. Hyperarid regions are mostly devoid of vegetation and animal life, and include rocky deserts and sand dunes. Vegetation in arid climate regions can include sparse grasslands, shrublands, and woodlands.

Deserts are inhabited by the Xerophytes which include succulent plants, geophytes, sclerophyll, and annual plants. Animals, including insects, reptiles, arachnids, birds and mammals, are frequently nocturnal to avoid moisture loss. In the southern Arizona, the unique Saguaro cactus grows too many meters in height and can survive up to 200 years of age if left undisturbed. First blooms do not appear until it is 50 to 75 years old.

Cold Deserts:

Cold desert in Asia is the Gobi desert occurs where seasonal shifting of the subtropical high is of some influence less than six months of the year. Specifically interior locations are dry because of their distance from moisture sources or their location in rain shadow areas on the leeward side of mountain ranges such as Himalayas and Andes.

Winter snows occur in the cold deserts but are generally light. Summers are hot, with highs varying between 30º and 40ºC. Night time lows -even in the summer, can cool 10º to 20ºC from the daytime high.

Map showing the location of deserts in Asia

Source: http://www.worldatlas.com/webimage/countrys/aslanddeserts.htm

Major Hot Deserts in Asia

The main hot deserts in Asia are as follows:-

  1. Arabian Desert
  • The Arabian Desert is the fourth largest desert in the world, with an area of about 2,330,000 square kilometers.
  • It is a vast desert wilderness stretching from Yemen to the Persian Gulf and Oman to Jordan and Iraq. It occupies most of the Arabian Peninsula, with an area of 2,330,000 square kilometers.
  • Animal species that are found are- Gazelles, oryx, sand cats, and spiny-tailed lizards are .They have adopted to desert conditions.
  • The rainfall amount is scanty and is generally around 100 mm, and the driest areas can receive between 30 and 40 mm of annual rain. Such dryness remains very rare throughout the desert, There are hardly any hyperarid areas in the Arabian Desert, in contrast with the Sahara Desert, where more than half of the area is hyperarid (annual rainfall below 50 mm).
  • Many species, such as the striped hyena, jackal and honey badger have become extinct in this area due to hunting, human encroachment and habitat destruction. Other species have been successfully re-introduced, such as the sand gazelle, and are protected at a number of reserves. Overgrazing by livestock, off-road driving, and human destruction of habitat are the main threats to this desert ecoregion.
  • The area is home to several diverse cultures, languages, and peoples, with Islam as the predominant faith. The major ethnic group in the region is the Arabs, whose primary language is Arabic. Nomadic Bedouin tribes have travelled through the Arabian Desert for thousands of years.
  • Ecological threats to the region include agricultural projects; human destruction of habitat; military activity (during Gulf War where US tanks eroded the top desert soil leading to increased sand dunes and dropping of depleted uranium on Iraqi targets that has become a cancer risk and source of water contamination); oil and gas production (Kuwait oil wells sabotage, dumping into Persian Gulf) and overgrazing by camels and goats, with increased herd size, and a more sedentary lifestyle amongst the Bedouin.

 

  1. Sahara Desert
  • The third largest desert in the world and the largest non-polar desert is the Sahara. Situated in North Africa, the Sahara makes up parts of Algeria, Chad, Egypt, Eritrea, Ethiopia, Libya, Mali, Mauritania, Morocco, Niger, Somalia, Sudan, Tunisia, and Western Sahara. The Sahara spans over 9,400,000 square kilometers across the continent, and is the world’s hottest desert.
  • It is covered by mountains, rocky areas, gravel plains, salt flats and huge areas of dunes. Contrary to popular belief, the desert is only 30% sand, and the rest 70% are gravel plains.
  • Areas in the central sometimes get no rain for years at a time.
  • Common vegetation – acacia, grasses and tamarisks.
  • Common animals – addax antelope, dorcas gazelle, fennec fox, horned viper, jackal, jerboa, sandgrouse and spiny-yailed lizard.
  • Nomads such as the Tuareg live here. It is crossed by Arab caravans since the 10th century.
  1. Gobi Desert
  • The fifth largest desert on Earth is Asia’s Gobi Desert. Situated in northwestern China and southern Mongolia, the Gobi Desert was created as a rain shadow from the tall Himalayan Mountains, which prevent rain from reaching Gobi.
  1. Thar Desert
  • It lies in India and Pakistan covering 200,000 sq. kms. It is mostly rocky sand and sand dunes with a majority part of the desert covered by sand dunes, and the rest covered by gravel plains.
  • Common vegetation- acacia, euphorbias, grasses, shrubs.
  • Animals- black buck, dromedary camel, great Indian bustard, Indian spiny-tailed lizard, jackel and sandgrouse.
  • Small villages of ten to twenty houses scattered throughout the Thar.

Kara Kum Desert
The Kara Kum covers 135,000 square miles, nearly 70 percent of Turkmenistan’s land. Because of the desert’s location along the Caspian Sea, the weather in Karakum is milder than many Asian deserts, which typically experience frigid winters and scorching summers.

Kyzyl Kum Desert
Crossing over Kazakhstan into Uzbekistan, this 115,000 square mile desert features a wide variety of flora and fauna. Though the area only receives 4 to 8 inches of rain per year, the rain occurs during the region’s cooler period so the water does not dissipate quickly and supports large migratory game.

Takla Makan Desert
China’s largest desert extends over 123,550 square miles. Composed primarily of shifting crescent sand dunes, the Takla Makan is one of the largest sandy deserts in the world. Despite the inhospitable and unpredictable nature of the desert sands, the Chinese government erected a road across the desert in the mid-1990s.

 

Why do hot deserts occur between 20-30 deg latitudes on the western margins on the Asian continent?

The occurrence of hot deserts in the 20-30 deg latitudes in both hemispheres and on the western margins of continents are due to a combination of multiple atmospheric and surface factors. The factor that determines the type of climate in any region is the amount of rainfall. Deserts are characterised by HOT and DRY conditions with very LESS RAINFALL. The following factors that occur in the 20-30 latitude regions contribute to the desertic conditions in these areas.

The occurrence of hot deserts in the 20-30 deg latitudes in both hemispheres and on the western margins of continents are due to a combination of multiple atmospheric and surface factors. The factor that determines the type of climate in any region is the amount of rainfall. Deserts are characterised by HOT and DRY conditions with very LESS RAINFALL. The following factors that occur in the 20-30 latitude regions contribute to the desertic conditions in these areas.

the north and south hemispheres respectively.Thus they flow over the entire continents from east to west. Because of this, by the time they reach the western margins of the continents all the moisture that they have been carrying would have been lost as rainfall for those regions along the way. What comes here – is just dry moisture free winds. Again this is not favouring the rainfall in this region resulting in dry desertic conditions.

Leeward sides of Mountains:

Another important factor that could be obeserved in some regions are the presence of High rise mountains along the western coasts.

Thus beacause of these reasons deserts in Asia are found between 20-30 deg latitudes on the western margins on the Asian continent.

General Circulation of the Atmosphere

General Circulation of the Atmosphere

Basic points to understand

 

  • Winds circulate around the globe because of the rotation of the earth and the energy from the sun.
  • The general direction of the winds varies around the globe depending on factors like latitude and proximity to oceans. The direction of the wind at various levels in the atmosphere determines the local climate and steers around weather systems and severe weather.

Wind circulates in each hemisphere in three distinct cells which help transport energy and heat from the equator to the poles.

The Hadley Cell

  • The circulation cell closest to the equator is called the Hadley cell
  • Winds are light at the equator because of the weak horizontal pressure gradients located there.   The warm surface conditions result in locally low pressure.  The warm air rises at the equator producing clouds and causing instability in the atmosphere.
  • This instability causes thunderstorms to develop and release large amounts of latent heat.  Latent heat is just energy released by the storms due to changes from water vapor to liquid water droplets as the vapor condenses in the clouds, causing the surrounding air to become more warm and moist, which essentially provides the energy to drive the Hadley cell.
  • The Hadley Cell encompasses latitudes from the equator to about 30°.  At this latitude surface high pressure causes the air near the ground to diverge.
  • This forces air to come down from aloft to “fill in” for the air that is diverging away from the surface high pressure. The air flowing northward from the equator high up in the atmosphere is warm and moist compared to the air nearer the poles.
  • This causes a strong temperature gradient between the two different air masses and a jet stream results. At the 30° latitudes, this jet is known as the subtropical jet stream which flows from west to east in both the Northern and Southern Hemispheres.
  • Clear skies generally prevail throughout the surface high pressure, which is where many of the deserts are located in the world.
  • From 30° latitude, some of the air that sinks to the surface returns to the equator to complete the Hadley Cell. This produces the northeast trade winds in the Northern Hemisphere and the southeast trades in the Southern Hemisphere. The Coriolis force impacts the direction of the wind flow. In the Northern Hemisphere, the Coriolis force turns the winds to the right. In the Southern Hemisphere, the Coriolis force turns the winds to the left.
  • From 30° latitude to 60° latitude, a new cell takes over known as the Ferrel Cell. This cell produces prevailing westerly winds at the surface within these latitudes. This is because some of the air sinking at 30° latitude continues traveling northward toward the poles and the Coriolis force bends it to the right (in the Northern Hemisphere). This air is still warm and at roughly 60° latitude approaches cold air moving down from the poles. With the converging air masses at the surface, the low surface pressure at 60° latitude causes air to rise and form clouds. Some of the rising warm air returns to 30° latitude to complete the Ferrel Cell.
  • The two air masses at 60° latitude do not mix well and form the polar front which separates the warm air from the cold air. Thus the polar front is the boundary between warm tropical air masses and the colder polar air moving from the north.  (The use of the word “front” is from military terminology; it is where opposing armies clash in battle.)  The polar jet stream aloft is located above the polar front and flows generally from west to east. The polar jet is strongest in the winter because of the greater temperature contrasts than during the summer.  Waves along this front can pull the boundary north or south, resulting in local warm and cold fronts which affect the weather at particular locations.
  • Above 60° latitude, the polar cell circulates cold, polar air equatorward. The air from the poles rises at 60° latitude where the polar cell and Ferrel cell meet, and some of this air returns to the poles completing the polar cell. Because the wind flows from high to low pressure and taking into account the effects of the Coriolis force, the winds above 60° latitude are prevailing easterlies.

Walker Circulation

 

  • In contrast to the Hadley, Ferrel and polar circulations that run along north-south lines, the Walker circulation is an east-west circulation.
  • Over the eastern Pacific Ocean, surface high pressure off the west coast of South America enhances the strength of the easterly trade winds found near the equator.
  • The winds blow away from the high pressure toward lower pressure near Indonesia. Upwelling, the rising of colder water from the deep ocean to the surface, occurs in the eastern Pacific along South America near Ecuador and Peru.
  • This cold water is especially nutrient-rich and is stocked with an abundance of large fish populations. By contrast the water in the western Pacific, near Indonesia, is relatively warm.
  • The air over Indonesia rises because of the surface low pressure located there and forms clouds. This causes heavy precipitation to fall over the western tropical Pacific throughout the year. The air then circulates back aloft towards the region above the surface high pressure near Ecuador and this becomes the Walker circulation. The air sinks at this surface high pressure and is picked up by the strong trade winds to continue the cycle.

 

On some occasions, the Walker circulation and the trade winds weaken, allowing warmer water to “slosh back” towards the eastern tropical Pacific near South America.  You can think of this as blowing a fan over a bathtub full of water.  If the fan blows steadily, the water at the side farthest from the fan will tend to pile up downwind.  If you suddenly slow the fan down, some of the water that was built up will surge back towards the fan.  The warmer water will cover the areas of upwelling, cutting off the flow of nutrients to the fish and animals that live in the eastern Pacific Ocean.  This warming of the eastern Pacific Ocean is known as El Niño.  The warmer water will also serve as a source for warm, moist air which can aid in the development of heavy thunderstorms over the mass of warm water.

How does this relate to agriculture?

Changes in the Hadley cell and Walker circulation can result in dramatic climate variations for many regions. In an El Niño winter, for example, the presence of the warm water in the eastern Pacific shifts the position of the subtropical jet, leading to heavy rainfall in Florida and southern Georgia.

In a warming climate, the Hadley cell could increase in length and alter the climate of regions around 30°. For example, many deserts in the northern hemisphere are located around the 30° latitude, and if the Hadley cell were to increase in length, that could cause dry conditions to move north of 30°. Ultimately, this would alter the precipitation patterns of many regions, including the Southeast.

Frequent occurrence of landslides in the Himalayas than in Western Ghats

Frequent occurrence of landslides in the Himalayas than in Western Ghats

Q. What are landslides? Why do they occur?
Answer:

  1. Landslides are simply defined as the mass movement of rock, debris or earth down a slope and have come to include a broad range of motions whereby falling, sliding and flowing under the influence of gravity dislodges earth material.
  2. They often take place in conjunction with earthquakes, floods and volcanoes. At times, prolonged rainfall causing heavy block the flow or river for quite some time.
  3. The formation of river blocks can cause havoc to the settlements downstream on its bursting.
  4. In the hilly terrain of India including the Himalayas, landslides have been a major and widely spread natural disaster the often strike life and property and occupy a position of major concern.

Q. Why there are more landslides in the Himalayas than in the Western Ghats?
Answer: Reasons can be divided as

A) Man-Made: –
• Excavation (particularly at the toe of slope)
• Loading of slope crest
• Draw -down (of reservoir)
• Deforestation
• Irrigation
• Mining
• Artificial vibrations
• Water impoundment and leakage from utilities
• Unplanned growth of houses in the hill areas. e.g. heavy load of residential and hotel structures in Nainital, Uttarakhand, this activity is less in Western Ghats.
• Population Density and Human activity is more.

B) Physical:-

  1.  The Himalayas mountain belt comprise of tectonically unstable younger geological formations subjected to severe seismic activity. The Western Ghats and nilgiris are geologically stable but have uplifted plateau margins influenced by neo- tectonic activity.
  2.  In winter there is high snow fall and this snow melts in summer hence large flow of debris.
  3.  Indian plate is moving northwards and subsiding under Eurasian plate, 5-10 cm a year, This leads to rising of Himalayas every year. Hence, it creates instability and it leads to more landslides.
  4. Great height, steep slopes, numerous streams and rivers hence it can carry high amount of debris which leads to more landslides in Himalayan region whereas in Western Ghats, Eroded and denuded, steep slope on western side, but gentle on eastern side. Western side, small swift flowing of stream.
  5. Eastern side – big rivers originated like, Godavari, Kaveri and Krishna in saline stage of erosion which cannot carry large amount of debris.

Q. Methods of protection – what can be done to avoid lanslides?

Answer: In general the chief mitigatory measures to be adopted for such areas are :
• Drainage correction,
• Proper land use measures – promotion of terrace farming.
• Reforestation for the areas occupied by degraded vegetation.
• Creation of awareness among local population.
• Control on new dam building.

El Nino, La-Nina- effects on Indian Agriculture

El Nino, La-Nina- effects on Indian Agriculture

Topic

El Nino- effects on Indian agriculture, La-Nina

Normal year

  • Peru Current = Humboldt Current = Cold Current.
  • During normal year two things are “STRONG”
    • Cold Peru Current
    • Trade Winds
  • As a result, cold water is dragged from Peru towards Australia. (observe following image)

Results in:

  • In above image, the red (warm) water region around Australia is called Western Pacific Pool (WPP)
  • WPP = low pressure = warm air ascends = cloud formation = rain over North Australia
  • This air also joins walker cell and begins descending near Peru.
below water Moving of water from Peru to Australia. @Peru cold water upwelling brings nutrient to surface=more lunch for Plankton= more fishes = good for Peru fishermen.
above water Moving of air from Australia towards Peru. Warm water + low atmospheric pressure = good rainfall over Australia & Indonesia.
  • Descending air = anti-cyclonic condition = high pressure = stability = no cloud/rain = Drought in Atacama Desert.

So in a way two cycles are created

What happens in La-Nina year?

Same things as in a “normal” year, but those two things become even “stronger”

  1. Cold Peru Current
  2. Trade Winds

Therefore,  There are  abundant  fishes in Peru coast, oversupply of fishes= prices become dirt cheap and too much rain / flood over Australia and Indonesia.

 What happens in El-nino year?

  • two things become “WEAK”
    1. Cold Peru Current
    2. Trade Winds
  • As result, cold water is not dragged from Peru to Australia.
  • But reverse happens – warm water is dragged from Australia towards Peru.
  • Consequently, warm water + low pressure condition develops in the Eastern Pacific (Peru) and Cold condition + high pressure in Western Pacific (Australia).

Since Pressure is inversely related with amount of rainfall, the results are following

  1. Rain & Floods @Peru, Atacama and even Southern USA
  2. Drought @Northern Australia, Indonesia- even bushfires.
  3. Storms and Hurricanes in East Pacific.
  4. Coral bleaching (high temperature coral dies)
  5. El Nino decreases earth’s rotation rate decreases Coriolis force and increases length of day. (La Nina creates opposite). How? Because El Nino changes the wind pattern, hence Earth needs change speed to conserve its angular momentum of Earth-Atmospheric system.

What is El-nino?

  • Warming of Pacific Ocean
  • Near Western coast of Peru and Ecuador.
  • Occurs @every 3-4 years; [In theory, it should occur @every 12 years].
  • Its impact usually lasts for 9-12-18-24 months.
  • It weakens the trade winds and changes in Southern Oscillation, thereby affects the rainfall pattern across the world.

 What is southern oscillation??

  • Alternating of (tropical) sea level pressure
  • Between the eastern and western hemispheres.

We measure Southern Oscillation by observing the pressure difference between

  1. Tahiti (French Polynesia) and
  2. Darwin (Australia).

 Impact of Southern Oscillation (SO)?

Low Index High SO
·         Smaller pressure difference between (tropical) oceans

·         of Eastern vs. Western Hemisphere

Higher pressure difference
associated with El Nino hence the name ENSO = El Nino-Sothern Oscillation La Nina
Weak trade winds Strong trade winds
poor monsoon good monsoon

 

How does El-nino affect Indian Monsoon??

  • El Nino-Southern Oscillation (ENSO) water circulation happens between Australia and Peru
  • But the wind movement is part of larger atmospheric circulation hence affects the rainfall over India. But how?

We learned that during normal year, the warm water moves towards Australia, this pool of warm water is called Western Pacific Pool (WPP). From WPP air rises above and moves towards two walker cells

  1. Towards Peru coast = this affects rainfall in South America.
  2. Towards Mascarene High Pressure zone near East Africa. = This affect Indian monsoon.
DURING NORMAL YEAR DURING EL NINO YEAR
·         strong WPP

·         strong trade winds

·         strong Mascarene High

·         Strong push for moisture laden winds towards India

·         good rain

·         weak WPP

·         weak trade winds

·         weakening of winds flowing towards Mascarene high

·         weak push to Monsoon winds towards India

·         Less rainfall / weak monsoon.

During La Nina years, this push is even stronger = heavy rain and floods. ·         El Nino caused severe drought in India (2009-10). Sugar price were highest in 30 year history.
El Nino= Little  boy in Spanish. Hence its opposite is called

·         La Nina (little girl)

·         El Vejo= old man, but La Nina more popular term nowadays.

·         Similar drought situation in Australia, Southeast Asia and Africa. (And floods in Brazil and USA Midwest.)

·         Such condition prevails for 9-24 months.

 

El-nino and India

  • Poor monsoon / drought like condition = commodities prices will rise especially sugar, pulses and edible oil. Government needs to stock them up, put restriction on exports, before black marketers start hoarding.
  • Farmers need to device alternate farming strategy, change the seeds and irrigation strategy for the drought like situation.

 

El-nino from economic survey

What is El-Nino?

  1. El Niño effect occurs when surface temperatures in the Pacific Ocean continuously rise above average for several months, which in turn adversely affects weather in many parts of the world.
  2. El Nino occurs every 3-5 years.
  3. South-west (SW) monsoon (from June to September) accounts for ~75% rainfall. Any shortage here.
  4. El Nino often begins to form during June-August, and typically lasts 9-12 months.

El Nino’s negative impact

  1. Rainfed regions of central, south, and north-west India
  2. Maharashtra, Gujarat, Rajasthan, Karnataka, Jharkhand, and Bihar.
  3. Rice, soybean, cotton, maize, jowar, groundnut, and sugarcane will be affected.
  4. Kharif pulses and oilseed

 

The El-nino effect and agriculture in India.

El Nino is a climatic phenomenon which impacts the western coast of South America, Australia, Indonesia and the monsoon regions of South Asia. It lasts for a year. A strong El Nino usually leads to drought-like conditions in the affected areas. There is no fixed pattern as to when it occurs, but it has a periodicity of eight to ten years. But its frequency is increasing as a result of global warming. The year 2014 is supposed to be an El Nino year.

The trade winds over the Pacific Ocean create a Warm Pacific Pool. This acts as a low pressure area over the ocean and a high pressure in the upper Troposphere. This high pressure has a sinking arm at the Mascarene High near Madagascar. This creates a high pressure over Mascarene, which propels the South-West Monsoon winds giving rain to India. In El Nino years, there is a high Sea Surface temperature which prevents the formation of Warm Pacific Pool and subsequently weakens the South-West Monsoon winds blowing towards India. This leads to poor rainfall in India.

India is an agrarian country; it contributes to sixteen percent of India’s Gross Domestic Product (GDP) and employs more than sixty percent of the working population. But, agriculture in India is largely rainfed. that is, it is monsoon dependent. The erratic nature of Indian monsoon leads to the vagaries in the agricultural productivity. In order to make Indian agriculture monsoon-proof, irrigation is required. Even after undertaking large scale irrigation projects, only thirty percent of India’s land has irrigation. Moreover, India cannot have all its agricultural land under irrigation and fifty million hectares out of one hundred forty-five million hectares will always be dependent on monsoon. Hence, poor rainfalls affect agriculture and El Nino years inevitably lead to poor agricultural productivity.

El Nino is linked to drought, which is an agricultural condition where prolonged water shortages lead to crop failure. But every El Nino year does not lead to drought, for example in the year 2002. The drought prone regions of India include areas with rainfall less than 60 cm of rain like the plateau of peninsular India like Deccan plateau, the desert areas of Thar and Saurashtra in Western India and the upland regions of Tamil Nadu. These regions are also poor regions and droughts affect the people much more than people of other regions.

The main consequence of El Nino is poor productivity which affects the poor farmers of peninsular India. Since majority of population is employed in agriculture, the effects of poor productivity are far reaching. The poor productivity leads to increased incidence of poverty and famine. Even the milch animals go hungry and it leads to poor production of milk. Poor productivity, which causes shortage of food, also leads to high food inflation throughout the country. High food inflation affects the poor disproportionately. The poor population, which has to shell more money for food. have less income to spend on other dietary needs like proteins. In order to curb inflation, RBI increases the interest rates which affects the common man also. Thus the effects of El Nino are not just confined to farmers but the whole of India.

As India Meteorological Department (IMD) has predicted the occurrence of El Nino in 2014, the government should take necessary steps to offset its effects. Government should promote the production of coarse grains. Coarse grains are able to meet all the dietary requirements of the people while at the same time require less water and are drought resistant. The Minimum Support Price of these grains should be made attractive to promote its production while that of rice and sugarcane, which are water intensive, should be reduced. The Public Distribution System for these grains should also be upgraded. There should be sale of seeds of crops which use less water. Government should make use of drought funds in case of serious drought and provide extra days of NREGA in such drought affected areas. It should release the stock of stored grains so that the food inflation does not rise unexpectedly.

We cannot control the weather phenomenon. The occurrence of El Nino is beyond our control. But we can take steps to minimize its effects to make sure that the poor population of the country doesn’t go hungry.

 

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