Climate of India

Climate of India


HELLO,

•India’s climate is dominated by monsoons. Monsoons are strong, often violent winds that change direction with the season.
•Monsoon winds blow from cold to warm regions because cold air takes up more space than warm air.
•Monsoons blow from the land toward the sea in winter, and from the sea toward land in the summer.
•India’s winters are hot and dry.
•The monsoon winds blow from the northeast and carry little moisture.
•The temperature is high - the Himalayas form a barrier that prevents cold air from passing onto the subcontinent.
•Additionally, most of India lies between the Tropic of Cancer and the equator, so the sun’s rays shine directly on the land.
•The temperature can reach as high as 110degrees F during the Indian winter.

•The summer monsoons roar onto the subcontinent from the southwest. 
•The winds carry moisture from the Indian Ocean and bring heavy rains from June to September.
•The torrential rainstorms often cause violent landslides. Entire villages have been swept away during monsoon rains.
•Despite the potential for destruction, the summer monsoons are welcomed in India. Farmers depend on the rains to irrigate their land. Additionally, a great deal of India’s electricity is generated by water power provided by the monsoon rains.
•Pakistan is much drier than India. The summer monsoon winds in India bring moisture from the Indian Ocean; Pakistan is north of the ocean and receives much less rain. The Thar Desert is on the border between India and Pakistan. It covers more than 77,000 square miles, about the size of Nebraska.





FACTORS AFFECTING THE CLIMATE OF SOUTH ASIA







1. LOCATION






• Latitude wise the Tropic of Cancer divides India into temperate or subtropical North and tropical South.
• Subcontinent lies between 8 degree 4’N and 37 degree 6’ N latitude.
•Northernmost part of the subcontinent is occupied by high mountains.
•Places situated north of Tropic of Cancer has extreme/continental type of climate.
•Southern peninsula – 3 sides by sea- moderate climate
•Coastal regions – has equable climate
•Temp in general increases from north to south



2. Influence of Hills and Mountains


The Karakoram Mountain Range in India 

•Himalaya Mountains - important role in lending a sub-tropical climate – barrier that separates sub-continent from rest of Asia
i)Prevents cold winds of North and Central Asia from blowing into the south – protects from cold winters.

ii. Traps monsoon winds , forcing them to shed the moisture within the subcontinents. So Indo-Gangetic plain receives heavy rainfall while central Asia lies in the ‘rainshadow’ of the Himalayas.

WESTERN GHATS:



•Obstructs southwest winds blowing from Arabian Sea.
•So Deccan Plateau gets very little rain as it on the leeward side or in the rain shadow of the Western Ghats.









ARAVALLI HILLS: 
•Runs parallel to the direction of the south-west monsoon winds.
•As such the moisture laden winds pass through Rajasthan without shedding their moisture. So dry climate.





HILLS OF ASSAM: 
•The hills of Southern Assam force the moisture-laden winds coming from the Bay of Bengal to shed their moisture before proceeding northwards.
•So Assam gets heavy rainfall while north is comparatively dry.

THE ARKANAN YOMA RANGE: 





Regions of the western sides of the Arakan Yoma get heavy rainfall brought by the South-West Monsoon winds.
•The central part of Myanmar which lies in the rain shadow of Arakan Yoma gets very little rain.








SOUTH-CENTRAL HILLS OF SRI LANKA:
•Large variation in the rainfall in the southern and northern parts of Sri Lanka due to its varied relief.
•The South-Central part of Sri Lanka is a hilly region rising to a height of 1,500m.
•The Northern Plain consists of extensive flat plain.


3. ALTITUDE

•Temperature decreases with increasing altitude
•For every 165 m ascent, the temp falls by 1 degree C.
•Hence places in the mountains are cooler than places on the plains
•Places on the Deccan Plateau are not very hot inspite of being near Equator.

4. DISTANCE FROM THE SEA

•India has long coastline,
•large coastal areas have an equable climate due to effect of land breeze and sea breeze caused by differential rate of heating and cooling of land and sea.
•Areas in the interior of the subcontinent are far away from the moderating influence of the sea – so have extreme climate.

5. WESTERN DISTURBANCES

•During winter there is an inflow of low pressure depressions called western disturbances in northwest India.
•These originate in Mediterranean Sea and enter India after crossing Iraq, Afghanisthan, Pakistan.
•They intensify over north-west India and move eastward causing rain in Punjab and Haryana and snowfall in the Himalayan belt
•During summer the whole of the east coast of India and the coastal areas of Bangladesh come under the influence of tropical depressions (low pressure systems originating at the head of the Bay of Bengal)
•They cause heavy loss to life and property.

6. Conditions in the regions surrounding the Subcontinent

•Temperature and pressure conditions in East Africa, Iran, Central Asia, Tibet determine the strength of the monsoons and the occasional dry spells.
•E.g. high temperatures in East Africa may draw the monsoon winds from the Indian Ocean into that region thus, causing a dry spell.



7. Conditions over the Ocean
•Weather conditions over the Indian Ocean and the China Sea (low pressure depressions in summer) may be responsible for typhoons – affects east coast of India.


8. The upper air currents or jet streams

•Upper air currents or jet streams in the upper layer of atmosphere could determine the onset and departure of the monsoon.
•Research work on – the extent to which monsoons may be affected by these air currents


CLIMATE OF INDIAN SUBCONTINENT
•The climate in India varies considerably,
•The northern state of Jammu and Kashmir and the Himalayan region will experience snow fall in winter with the temperature going below the freezing point while in southern part, the temperature can rise up in summer. The Thar desert in the northwest region of India experiences less than 10 inches of rain where as the Shillong plateau in the northeast recieves more than 450 inches of rain. The town of Chirapunji, in the northeast state of Assam has recorded the highest rainfall, in one year, in the world (1, 042 inches).
•The climate in India is greatly dominated by the two monsoon winds - the Northeast monsoon wind and the Southwest monsoon wind. The most important of these is the Southwest monsoon wind. The progress of this wind can be used to divide the year into six seasons: winter, spring, summer, summer monsoon, autumn, and the winter monsoon.
•The failure of these winds to produce sufficient rain causes famine and drought in the central part of India. Excessive rain with heavy winds, known as cyclones, cause flash floods and loss of crops and lives of both human and animals. In India, mainly an agricultural country, the life of a farmer depends on the rain.
•Inspite of great diversity and variation in Indian climate and topography, due to various reasons, the most important factor that lends unity to the Indian sub continent is the fact or the monsoons.
•Alternating winds over the Arabian sea.
•These winds appear to blow from southwest for 6 months and from northeast for another 6 months
•Hence as they reverse their directions seasonally , they are called ‘monsoon winds’ and the climate as TROPICAL MONSOON TYPE.
•“ Monsoons are large scale seasonal winds system flowing over vast areas of the globe, persistently in the same direction, only to be reversed with the change of season.” – A Rama Shastry
•Monsoon winds can be called Land and Sea breezes on large scale as both are caused due to differential heating of land and sea
•Winds are called Southwest Monsoon and Northeast Monsoon on the basis of the direction from where they blow.
•Their main feature is alternation of seasons which determines the climate of the Indian Subcontinent.





















Has very hot and cold regions
•Regions with heavy rainfalls and scanty rainfall.
•Large part of India has tropical monsoon climate.
•Climate of India is influenced by its position, size, and relief features.
•Monsoon winds are main factors that determine climate of India.
•They influence a large part of India.
 


India has 4 major seasons - winter - summer –rainy and the retreating monsoons.
Winter months (December-February) are bright and pleasant, with snowfall in the northern hills.
Summer time (March-May) is hot in most parts of India, and it is then that the numerous hill resorts provide cool retreat.
South-West monsoons or rainy season, rainfall is heavy along the west coast between June and September, and along the east coast between mid-October and December.
Retreating monsoons – October & November: The South-West Monsoon winds start retreating from the beginning of October due to decrease in temperature and increase in pressure and they are called Retreating Monsoon winds.

1.WINTER

•Sun’s rays fall vertically over Southern Hemisphere.
•So, India gets oblique rays of the sun and temperature decreases.
•Days are bright due to sunlight but nights are cold.
•Fine weather is disturbed by temperate cyclones which originate over the Mediterranean Sea & cause rainfall & snowfall in north-western parts of India.
•North-East Monsoons blow from land & are dry.
•However they gather mositure while crossing the Bay of Bengal and cause rainfall along Coromandel coast.
•Contributes to over 2% of the country’s annual average rainfall.

QUESTION: Describe the pressure and wind conditions of India during winter.

ANSWER: High pressure is formed at the north of Himalays and cold icy winds starts blowing towards Indian Ocean to the south. (i.e. low pressure area) 

2.Summer

•Middle of March to end of May
•Sun’s rays fall vertically over northern hemisphere & so temperature is high
•The north Indian plain has very high temperature because of long days & distance from sea.
•Dust storms & hot dry winds are common
•Ganganagar of Rajasthan-52 degree C-has highest temperature
•During this time, northern mountain region & plateau of Peninsular India are cooler.
•Rainfall occurs at few places due to local convection currents.
•Pre-monsoon showers that occur in April-May in Kerala are called Mango showers.
•Assam & W. Bengal get some rain during this season.
•North-western regions do not get any rainfall.
•Coromadel coast gets some rainfall
•India gets 10% of total rainfall during this season.

•The pre-monsoon showers that occur in April-May due to local heating and convection currents are called Mango showers. They occur in Kerala.


3. RAINY SEASON (June - September)


75% of rainfall during this season.
•By end of May, north-western region has high temperature & due to this Rajasthan develops low pressure area. This low pressure attracts south-east trade winds from the south of equator. When they cross the equator, they change their direction according to ‘Ferrel’s Law’ and they become South-West monsoons.
•Word ‘Monsoon’ from Arabic word ‘mousim’ which means season.
•They are moisture-laden winds & give heavy; rain to a greater part of India
•Peninsular shape of India divides South-West Monsoon winds into Arabian sea branch & Bay of Bengal branch
•Arabian sea branch strikes the Western Ghats & cause heavy rainfall to the western side of the Western Ghats
•Rainfall decreases as it advances towards Madhya Pradesh.
•Rainfall is very heavy in the north-eastern region, the western slopes of the Western Ghats and parts of the Himalayas, all of which receive over 2,000 mm annually.
•Climate and the south west monsoon winds control agricultural activities in India. They have an indirect bearing on crop patterns and economic activities of farmers. Majority of the people in India are farmers. If monsoons fail, the crops fail and if they are heavy, there are floods. If monsoons are good enough there is a good harvest. Thus, there is maximum dependence of agriculture on monsoons. Hence the saying – agriculture is a gamble with monsoons. 








Characteristics of monsoon winds
•The Monsoon winds are moisture-laden winds and cause heavy rainfall. They are seasonal winds.
•(4 marks): By the end of May when the weather is at its hottest in India, low pressure area develops in Rajasthan and the north west. South East trade winds from the South of the equator blow towards it but due to the rotation of the earth (Farrel’s law) change direction and become south west winds. Since they blow from across the ocean, they are moisture laden and are known as Monsoon winds. They cause heavy rainfall to greater parts of India. The Western Ghats get rainfall from the South-West monsoon winds.
• They blow from the equator across the Indian Ocean, Arabian Sea and the Bay of Bengal. As these winds blow across the west coast, they are stopped by the Western Ghats and thus giving heavy rainfall.
•Eastern side of Western Ghats becomes a rain shadow area
•Bay of Bengal branch moves towards Myanmar, north eastern parts of India, foothills of Himalayas & North Indian Plain & causes heavy rainfall.
•As they move towards the west, rainfall decreases. With the exception of Tamil Nadu, most parts of India get rainfall from South West Monsoons.
•Rajasthan , Kachchh and Ladakh have hardly any rainfall.





Monsoon in India










South West summer monsoon




By the end of May when the weather is at its hottest in India, low pressure area develops in Rajasthan and the north west. South East trade winds from the South of the equator blow towards it but due to the rotation of the earth (Farrel’s law) change direction and become south west winds. Since they blow from across the ocean, they are moisture laden and are known as Monsoon winds. They cause heavy rainfall to greater parts of India.

The Peninsular shape of India divides the South-West Monsoon winds into two branches namely the Arabian Sea branch and Bay of Bengal branch. The Arabian Sea branch strikes the Western Ghats and gives heavy rainfall to the western side. The rain decreases as it advances towards Madhya Pradesh. The Bay of Bengal branch moves towards Myanmar and the north-eastern part of India, the foothills of the Himalayas and the Northern Plains and causes heavy rainfall. The rain decreases as the winds move westwards. With the exception of Tamil Nadu, most of India’s rainfall comes from the South West Monsoons.

QUESTION: What is a monsoon?
ANS: The term Monsoon is derived from the Arabic word ‘mausim’, meaning season, applied by the Arabs to the seasonal winds of the Arabian sea. Monsoon winds mean a complete reversal in the direction of wind over a large part of the land, causing seasons.

QUESTION: What is Coriolis force? or What is Ferrel's Law?

Ans: It is the force caused by the earth's rotation. It deflects the North-East Trade Winds towards right in the Northern Hemisphere and left in the Southern Hemisphere . It is also called Ferrel's Law.

QUESTION: Describe the pressure and wind conditions of India during summer.

Low pressure is formed in the north-western India and high pressure area is formed over the southern Indian Ocean. It attracts south-west monsoon winds causing widespread rains in India.

QUESTION :Which are the two characteristic features of the tropical climate?

ANS: The two characterstics features of a tropical climate are as follows, i) High temperature throughout the year. ii) Dry winters.

QUESTION: Give the characteristics of monsoonal rainfall in India.
ANS: Characteristics of monsoon rainfall are :- i) It gives water in glut to the entire territories of India except some leeward sides, rain shadow regions and deserts. ii) Early in the season, the windward side of the Western Ghats receives heavy rainfall i.e. more than 250 cm. iii)The rain shadow areas of Deccan Plateaue and parts of Madhya Pradesh also receive scanty rainfall. iv)The maximum rainfall is recorded in the north eastern part of the country. v)The frequency and intensity of tropical depressions determine the amount and duration of monsoon rains.


QUESTION: Discuss the mechanisms of the Indian monsoons.
ANS: The mechanism of Indian Monsoons :- i)The different heating and cooling of land and water : At the end of May, due to high temperature, low pressure is created on the landmass of India while seas around experience comparatively high pressure. It fixes the direction of the moisture laden wind from sea to land.ii)The shift of the position of Inter Tropical Convergence Zone (ITCZ) : In summer, low pressure trough is positioned over the Ganga plain, making the region suitable for the occurrence of rain. iii)The intensity and position of the high atmospheric pressure over the Indian ocean affects the Indian monsoon. iv)The Tibetan plateau gets intensely heated during summer which results in strong vertical air currents and formation of high pressure over the plateau at about 9km above the sea level. v)The movements of the westerly Jet Streams to the north of the Himalayas and the presence of the tropical easterly Jet Streams over the Indian Peninsula during the summer affects monsoon.

4. Retreating Monsoon Season
•= South-West monsoon winds start retreating from the beginning of Oct due to decrease in temperature & increase in pressure.
•Transition period from rainy season to winter season.
•Cyclonic depressions are formed in Bay of Bengal & they move towards eastern coast.
•They give heavy rainfall to coasts of Tamil Nadu, A.P., Orissa. They often cause widespread destruction to the coastal areas.
•India gets 13% of total annual rainfall during this season.


QUESTION: What is meant by retreating monsoons?
ANS: The South-West monsoon becomes a weak current and withdraws from Punjab by mid-September. It leaves the Ganga delta by late October. By early November, it leaves the southern part of the peninsula. These particular months from September to November are termed as the period of ‘retreating monsoon’. During this time, the days are hot, nights are cool and the daily range of temperature is high.


QUESTION: The Coramandel coast has more rainy months but less rainfall than the Konkan coast. Why?


ANS: Konkan coast faces on-shores S.W. Monsoon during summer. These moisture laden winds give heavy rainfall. But these winds do not give much rainfall on the Coramandel Coast as it lies in the rainshadow of Western Ghats. Coramandel Coast also receives winter rainfall from N.E Monsoon, but on Konkan Coast these winds are off-shore and do not give any rainfall. Thus Coramandel Coast gets rainfall in both the seasons, but the total amount of rainfall is less than that of Konkan Coast.


Chennai gets most of rain from retreating monsoon in October and November. These winds after picking up moisture from Bay of Bengal give more rain on the east coast. Thus Chennai gets most of rain in winter when the fury of monsoon is over in most parts of the country.

QUESTION: What do you understand by ‘break’ in the monsoon?

ANS: Sudden approach of the moisture laden winds associated with violent thunder and lightening is known as ‘break’ or ‘burst’ in the monsoon.

QUESTION: The western part of Rajasthan remains almost dry during south-west monsoon season. Give reasons.


ANS: The western part of Rajasthan remains almost dry during south-west monsoon season because:


i. The monsoon winds blow from east dropping much of its moisture along the path. When they reach Rajasthan, they are almost dry.


ii. There is no mountain high enough to check the flow of the Arabian branch of monsoon winds. The Aravalli mountains are not high. The direction of the Aravalli mountains is parallel to the direction of Arabian Sea winds. Hence, these winds cross over Rajasthan without giving rainfall.


iii. The intense heat of western Rajasthan desert does not allow the condensation of moisture to take place and hence no rain is there.

QUESTION: Give reasons as to why the Delta region of the eastern coast is frequently struck by cyclones.
ANS: By early November, the low pressure conditions, which were over the North-western India, get transferred to the Bay of Bengal. This shift is associated with occurrence of cyclonic depressions, which originate over the Andaman Sea and cause heavy rain along the eastern coast of India. The deltas of Godavari, Krishna and Kaveri are frequently struck by cyclones which cause great damage to life and property. At times, these cyclones also cause destructive rainfall in the coastal regions of Orissa, West Bengal and Bangladesh. Coromandel coast gets bulk of its rainfall from these depressions.

QUESTION: Why does India have a monsoon type of climate?
ANS: India has a monsoon type of climate because :-i)It is strongly governed by the monsoon winds. ii)Pre-monsoon, monsoon and post-monsoon duration is called seasons here. iii)India exists in the tropical area (half of it is lying at south to the Tropic of Cancer )iv)There is an active coriolis force, that deflects winds towards the right in the Northern hemisphere and left in the southern hemisphere.

QUESTION: Distinguish between South-west monsoon and North-east monsoon.
ANS: i.South-West MonsooN season is from June to September and North-East season starts from December and ends in February.
ii) South-Wesr does not rain continuously. There are rainless intervals in this season. North-East moonsoon does not possess any rainless intervals.
iii) South-West monsoon blows in India namely the Arabian Sea branch and Bay of Bengal branch whereas North-East does not have any branches.
iv) Major portion of annual rainfall in India is due to South-West type of monsoon.Only minor portion of the annual rainfall in India is due to North-East type of monsoon.

DISTRIBUTION OF RAINFALL

•Rainfall – seasonal, uncertain, unevenly distributed.
•Most of it comes during South-West Monsoon period.
•Rainfall may be too much or too little.
•There also a long dry periods in between.
•On the basis of quantity of rainfall, we can divide India into 5 major rainfall regions.


1. Very low rainfall region (less than 40 cms per year)
•Found in Karakoram ranges, northern Kashmir & Western parts of Kachchh and Rajasthan (Thar Desert)
•Royli in Rajasthan gets only 8.3 cm of rainfall in a year. (region of very low rainfall in India)


2. Low rainfall region(40 cms to 60cms per year)
•Found in Zaskar range, parts of Punjab & Haryana, Central Rajasthan, Western Gujarat and rain-shadow of Western Ghats.


3. Moderate rainfall region(60cm to 100cm per year)
Found over a greater part of India, excluding areas of low rainfall & heavy rainfall.
•Most of the rain is from South-West Monsoon winds.
 


4. Heavy rainfall region(100cm – 200 cm per year)
Found in 4 separate areas.
•A narrow belt of western coast
•Eastern coastal belt
•Foothills of Himalayas
•A part of north-east India


5. Very heavy rainfall region(over 200 cm per year)
Found on the western side of Western Ghats (Agumbe, Kudremukh), foothills of Himalayas, Meghalaya plateau ((Shillong plateau) & Andaman & Nicobar Islands.
•Mawsynram in Meghalaya plateau has recorded 1141 cm of rainfall per year & it is the place which gets the heaviest rainfall in India .

Because of India's size, its climate depends not only on the time of year, but also the location.
In general, temperatures tend to be cooler in the north, especially between September and March.
The south is coolest between November to January. In addition to winter and summer there is also monsoon, spring and autumn.
In monsoon although it rains nearly every day, the downpour tends to come and go quickly leaving behind a clean, glistening landscape.
•Climate plays a very important role in economic development of a nation.
•South-West Monsoons control the agriculture of India, which is main occupation of people.
•When monsoons fail, there is drought, and crops fail.
•When monsoons are heavy, there are floods, they also cause destruction to life and property.
•Hence ‘Indian agriculture is a gamble with the Monsoons’.


FEW IMPORTANT QUESTIONS :



1. Discuss the unifying role of the Indian monsoon.
There is great diversity of the climatic conditions in India due to different location and land relief patterns. But these diversities are subdued by the monsoon, which blow over the whole country. The arrival of the monsoon is most welcome all over the country. Several festivals are celebrated welcoming the monsoonal rainfall in India. Monsoon gives relief from the scorching heat. The monsoonal rainfall provides water for agricultural activities. The entire life of the Indian people revolves around the monsoon.

2. What influences have the Himalayans on India's climate?

ANS: The Himalayas' lofty peaks act as an effective climatic divide.These protect India from cold and chilly winds originating near the Arctic Circle. These compel the rainbearing clouds to pour in India. The Himalayas give India, a touch of tropical climates, hot summers and dry winters.


Shall we revise the lesson?



1. Which type of climate is found in India?



2. Name the hottest place in India?



3. Name the rainiest place in India?



4. Name the coldest place in India.



5. Name the lowest annual range of temperature.



6. What is climate?



7. What is the cause of winter rainfall on south-east coast of India?



8. Which part of India gets winter rainfall due to retreating monsoons in India?



9. What is jet stream?


MORE QUESTIONS:

QUESTION1: Why does Central Plateau of India receive scanty rainfall?
Central Plateau of India receives scanty rainfall because it comes under rain-shadow region of the Western Ghats as well as of the Eastern Ghats.

QUESTION 2:What is coriolis force?
It is the force caused by the earth’s rotation. It deflects the North-East trade winds towards right in the Northern Hemisphere and left in the Southern Hemisphere.

QUESTION 3: What are the controlling elements of the climate of India?
India’s climate is controlled by latitude, altitude, pressure and winds, distance from the sea, ocean currents and physiography.

QUESTION 4: What do you mean by a rain shadow area?
A rain-shadow area is the slope of the hill which is away from the direction of the moisture laden wind. This area experiences very little amount of rainfall. E.g. eastern slope of the Western Ghats is the rain shadow area.

QUESTION 5: What are the western disturbances?
The disturbances brought by the easterly and westerly Jet streams are known as the western disturbances. These are experienced in the north and north-western part of India.

QUESTION 6: What is a Mango shower?
The pre-monsoon shower which helps in the ripening of mangoes in coastal Kerala and Karnataka is known as mango-shower.

QUESTION 7: Namei) Two rainiest stations.ii) Two driest stations in India.
i) Mawsynram and Cherrapunji.

ii) Leh and Thar desert (Indian desert).

QUESTION 8: Which are the two characteristic features of the tropical climate?
The two characterstics features of a tropical climate are as follows, i) High temperature throughout the year. ii) Dry winters.

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Jaydeep Mehta,
23 Jul 2013 22:29
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Jaydeep Mehta,
23 Jul 2013 22:30
ć
ď
Jaydeep Mehta,
23 Jul 2013 22:30
ć
ď
Jaydeep Mehta,
23 Jul 2013 22:30
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