(i) What are the controls affecting the climate of India?
(ii) Why does India have a monsoon type of climate?
(iii) Which part of India does experience the highest diurnal range of temperature and why?
(iv) Which winds account for rainfall along the Malabar Coast?
(v) What are Jet streams and how do they affect the climate of India?
(vi) Define monsoons. What do you understand by “break” in monsoon?
(vii) Why is the monsoon considered a unifying bond?
Ans 2(i):
Various factors, both lying within and outside India influence the climate of India. The chief among them are the following -
(1) Latitude: The Tropic of Cancer passes through the middle of the country from the Rann of Kutchh in the west to Mizoram in the east. The areas lying in the south of the Tropic of Cancer belong to the tropical area while the remaining areas lying in the north of Tropic of Cancer belong to the sub-tropical area. Therefore, India’s climate has characteristics of tropical as well as sub-tropical areas.
(2) Altitude: With the increase in altitude the atmosphere becomes less dense and temperature decreases. That is why hills are cooler during summer. India has an average height of 6000 meters in the north while in the south there is a vast coastal area with maximum elevation of about 30 meters. It is because of the differences in altitudes or relief that while it is hot during summer in the Plains of Punjab, Haryana, UP etc., the places in the mountains like Nainital, Darjeeling, and Ooty etc. are cool.
(3) Physiography: Physiography also plays an important role in determining the climate of a place. India has a varied Physiography. The Himalayas in the north act as great barrier to the cold winds from Central Asia. In absence of the Himalayas, India would have been a very cold country. The location of the Arabian Sea, the Indian Ocean and the Bay of Bengal on the three sides of India exert a moderating influence on the climate of India. This ocean, sea etc. being a huge water body acts as a store house of moisture which India needs very badly. Without these water bodies India would have been a very hot country with a climate like that of a dessert like Sahara in Africa.
(4) Western Cyclonic Disturbances: The western cyclonic disturbances are weather phenomena of the winter months brought in by the westerly flow from the Mediterranean region. They usually influence the weather of the north-western regions of India. In winter, in northern India, Punjab and Haryana get some rain from these western disturbances.
(5) Pressure and Winds: India lies in the region of north-easterly winds. These winds originate from sub-tropical high pressure belt of northern hemisphere. The fury of monsoons as well as long dry spell in India is mainly due to the pressure conditions which develop in the surrounding countries like East Africa, Iran, and Central Asia.
Winds especially Typhoons originating in China Ocean currents along with onshore winds and monsoon winds have a great control on the climate of India. Also the upper air circulation such as Jet Streams play a dominant role in determining the climate of India.
Ans 2(ii):
The word “Monsoon” is derived from the Arabic word ‘Mausim’ which literally means season. Monsoon refers to the seasonal reversal in the wind direction during a year. The monsoon winds are confined to the tropical area roughly between 20ON to 20OS latitudes. But in the Indian subcontinents, because of the Himalayan ranges, they bring the whole subcontinent under the sway of the moist bearing winds for 2 - 5 months roughly between May to October. Almost 90% rainfall in India is due to these monsoon winds. India would have been an arid land or desert if there had been no phenomena of monsoons. It is because of these reasons that the climate of India is described as monsoon type.
Ans 2(iii):
The difference in temperature of a particular place in a single day is called the diurnal change of temperature. The highest diurnal range of temperature has been found in Thar Desert of Rajasthan. At this place the day temperature may rise to 50OC and may drop down to near freezing point the same night.
The highest diurnal range of temperature has been found at the Thar Desert because there the weather conditions drastically change during the day and during the same night. The great difference between the day and night temperatures result in the highest range of diurnal range of temperature in the Thar Desert.
Ans 2(iv):
South-West monsoons account for the rainfall along the Malabar Coast while North-East monsoons account for the rainfall along the Coromeodal Coast or East Coast.
Ans 2(v):
Jet Streams are fast flowing winds blowing in a narrow zone in the high altitude above 12000 m in troposphere. There are a number of separate jet streams whose speed varies from 110 km/h in summer to about 184 km/h in winter.
In winter the sub-tropical westerly jet streams bring rain to the western part of India, especially Himachal Pradesh, Haryana and Punjab. In summer the sub-tropical easterly jet blows over Peninsular India approximately at 14ON and bring some rain and storm.
Ans 2(vi):
Monsoon - The word “Monsoon” is derived from the Arabic word ‘Mausim’ which literally means season. Monsoon is thus the rain-bearing winds which reverse their direction with the change of ‘mausam’ or season and blow throughout the Indian subcontinent, especially from May to October.
Break Monsoon - The monsoon rain takes place only for a few days continuously at a time. They are inter-spread with rainless intervals. Thus monsoon rains have wet and dry spells. So, this phenomena associated with the rainfall during monsoon is known as ‘break’.
Ans 2(vii):
India is a vast country with varied topography. On the north the Himalayas protect the sub-continent from the extreme cold winds of Central Asia. This enables northern India to have uniformly higher temperatures as compared to other areas on the same latitudes. Similarly the peninsular plateau, under the influence of sea from three sides, has moderate temperatures. Despite such moderating influences there are great variations in the temperature conditions.
Nevertheless, the unifying influence of the monsoons on the Indian subcontinent is quite perceptible. The Indian landscape, its animal and plant life, the agriculture calendar and the life of the people including their festivities and economic conditions revolve around the monsoon. Year after year, the people of India from North to South and from East to West eagerly await the arrival of the monsoon. These monsoon winds bind the whole country by providing water to set the agricultural activities. Thus, in view of the above the monsoon is considered as a unifying bond for this subcontinent.
Q.3: Why does the rainfall decrease from the east to the west in Northern India?
Ans: In summer, the monsoons rise both from the Bay of Bengal and the Arabian Sea. The monsoons which rise from the Bay of Bengal cause heavy rainfall in the Brahmaputra Valley and the Assam Hills (i.e. in Cherrapunji). Because of the Himalayas they then take a western turn and move up the Ganga Valley but as they proceed westwards they become drier and drier and therefore they cause less and less rain as they move forward. As such Kolkata gets a rainfall of 119 cm, Patna 105 cm, Allahabad 76 cm and Delhi 56 cm.
Q.4: Give reasons as to why,
(i) Seasonal reversal of wind direction takes place over the Indian subcontinent?
(ii) The bulk of rainfall in India is concentrated over a few months.
(iii) The Tamilnadu coast receives winter rainfall.
(iv) The delta region of the eastern coast is frequently struck by cyclones.
(v) Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone.
Ans 4(i): Monsoons blow from northeast India towards the sea during winter (November to April) but with the beginning of summer they begin to reverse their direction. During winter (October - November) with the apparent movement of sun towards the south, the low pressure trough over then northern plains becomes weaker which causes the monsoon wind to blow from northeast to south during this period.
In summer, areas of low pressure develop in north and northwest parts of India due to which winds from the high pressure area i.e. sea begin to blow towards the land masses. So, a shift in the development of monsoon trough or low pressure trough along with the change of season is the main reason for the reversal of wind direction in Indian subcontinent.
Answers of Q.4(ii) to 4(v) are given in a separate post. [Check the answers of Sample and Objective Questions, link given below].
Q.5: Describe the regional variations in the climatic conditions of India with help of suitable examples.
Ans: The climate of India is described as that of the monsoon type. But within this general pattern there are found certain regional variations in climatic conditions. This is because of the variations in temperature, precipitation, atmospheric pressure, wind, humidity and altitude from place to place. The following are a few examples which prove the above fact:
Range of Temperature - Temperature has great bearing on the climate, so difference in temperature is bound to create variation in the climate. In India there are places like, Rajasthan and south-west Punjab, where the mercury rises even up to 55OC. On the other hand, there are places like Dras, near Kargil, where the temperature sometimes, touches as low as -45OC.
Direction of the Rain-bearing Winds - The direction of the Rain-bearing winds has a great impact on the climate of a place. The summer monsoons arising from the Arabian Sea because of their south-west direction strike the Western Ghats first and cause a heavy rainfall there (about 250 cm). But these winds reach the Eastern Ghats last of all so there is less rainfall in Tamil Nadu and consequently it is much lower as compared to the rainfall on the Malabar Coast of the Western Ghats.
Form of Precipitation - The form of precipitation whether it is in the form of light rains or heavy snow has also a great-bearing on the climate of an area. In winter north-west of India gets some rains due to the Western Disturbances. As a result, there is little rain in the plains of Punjab and Haryana but there is heavy snowfall in the Western Himalayas especially in Himachal Pradesh and Jammu and Kashmir. It is all due to the change in the form of precipitation.
Amount of Rainfall - Difference in rainfall is bound to create variations in climate. In India, there are places like Mawsynram which receives 1080 cm of rainfall annually. This is perhaps the highest rainfall all over the world. On the other hand, there are places in India, especially in Rajasthan, which gets 20 cm of annual rainfall.
Rainfall Regime or Seasonal Distribution of Rains - In India, there are many parts which get rains only in summer while there are others which dry in that season. On the other hand, there are certain places which get rains in winter alone while there are others which get scanty or no rainfall in winter. For example Tamil Nadu and AP get much of their rainfall in winter season, and in summer they are almost dry. This seasonal distribution of rainfall has a great bearing on climate. In summer both Tamil Nadu and AP experience dry and hot season while the rest of the country especially Kerala, Karnataka and Maharashtra on the west-coast of India has a pleasant climate.
Q.6: Discuss the mechanisms of monsoons.
Ans: The word ‘monsoon’ refers to the seasonal reversal in the wind direction during a year. The monsoon winds are confined to the tropical area lying between 20ON to 20OS latitudes. The mechanism of monsoons or the phenomena of the seasonal reversal in wind direction is related to the following fact:
1. The differential heating and cooling of land and water.
2. The shift of the position of Inter Tropical Convergence Zone (ITCZ) in summer over the Ganga plain.
3. The presence of high pressure area, east of Madagascar over the Indian Ocean. The intensity and position of this high pressure area affects the Indian monsoon.
4. The Tibetan plateaus gets intensely heated during summer resulting into strong vertical air currents and the information of low pressure over the plateau.
5. The movement of the westerly Jet Stream to the north of the Himalayas and the presence of the tropical easterly Jet Stream over the Indian Peninsula during summer.
The meteorologists have found out a seesaw kind of relationship between the meteorological changes going on over the Pacific and the Indian Ocean. Whenever there is high pressure in the subtropical region of the Pacific Ocean in the northern hemisphere, the pressure in the south of Indian Ocean tends to be low and vice-versa. This is known as the ‘Southern Oscillation’ or SO which causes the shifting of winds across the equator in different directions. Besides the above facts, some other events such as ElNino, ENSO etc. are also connected to the mechanism of monsoons.
Q.7: Give an account of weather conditions and characteristics of the cold season.
Ans: The cold weather persists from December to February throughout India. January is the coldest month. During this period temperature varies from 10OC to 15OC in northern plains and 25OC in southern parts of the country. There is high pressure in northern plains due to the cold climatic conditions. The cold dry winds blow from the high pressure towards the low pressure equatorial regions. These winds are north-westerly in the Ganga plains and north-easterly over the Bay of Bengal. Only two parts of the country receive rain in this season. First is the north-west part of the country which receives rainfall, caused by the Western Cyclonic Disturbances originating in the Persian Gulf and Mediterranean regions. Second is the coast of Tamil Nadu which gets rainfall in winter because of the north-east winds on Retreating Monsoons which blow over the Bay of Bengal. But in other parts of the country, the weather is pleasant with clear skies and bright sunshine.
Q.8: Give the characteristics and effects of the monsoon rainfall in India.
Ans: Chief Characteristics and Effects of the Monsoons or Monsoon Rainfall
(a) The monsoons account for 90% of the rainfall received by India. Almost every part of the country except the east coast of Tamil Nadu receives the bulk of rainfall from the summer monsoons.
(b) The rainfall is neither continuous nor regular even in the wettest areas.
(c) Overall rainfall is not the same each year. The monsoons may be strong or weak in a particular year depending on the intensity and frequency of depression in the Bay of Bengal.
(d) The monsoon rains are not evenly distributed.
(e) A low pressure near the Himalayas may result in heavy rains in the hills causing floods in the plains or the plains may face prolonged dry spells.
(f) Sometimes, the monsoons may break too early or too late. There may be too long or too many breaks in the monsoons, which may retreat too early or too late. All these factors upset the agricultural operations making agriculture in India a mere gamble.
Sometimes, the effects of the monsoons or its uneven distribution create a number of problems. Like if there is too much rain it causes floods and havoc all around. On the other hand insufficient rain in a year or over some years results in draught, famine, food-insecurity, starvation and death.
Extra Question:Q.1: Give reasons as to why,
(i) The bulk of rainfall in India is concentrated over a few months. [Textbook Q. No 4 ii]
(ii) The Tamilnadu coast receives winter rainfall. [Textbook Q. No 4 iii]
(iii) The delta region of the eastern coast is frequently struck by cyclones. [Textbook Q. No 4 iv]
(iv) Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone. [Textbook Q. No 4 v]
Ans 1(i): The bulk of rainfall in India is concentrated over a few months beginning from June to September. During these four months, the rain bearing winds, popularly known as South-West Monsoons, blow northwards in two branches from the Arabian Sea and the Bay of Bengal. These winds blow from the oceanic high pressure areas towards the low pressure areas of land and cause a heavy rainfall. The Arabian Sea branch causes heavy rainfall exceeding 300 cm along the coastal areas of Western Ghats. The Bay of Bengal branch causes heavy rainfall in the hills of Assam, Meghalaya. Mawsynram situated in Meghalaya receives the highest rainfall in the world.
Ans 1(ii): The Tamilnadu coast receives winter rainfall can be best explained by the following reasons -
(A) In summer, when the monsoons are in full fury the Eastern Coast remain almost dry because the south-west monsoons which arise from the Arabian Sea cause much rainfall on the Western Ghats but when they reach the East coast of India they become totally dry. As such, Chennai receives no rain in summer.
(B) During winter there is high pressure on the Indian mainland while there is low pressure over the Indian Ocean as such winds from the mainland begin to blow towards the sea. These winds are called retreating monsoons which blow in the months of October and November from the land to the sea from the north-east direction. When these dry winds cross over the Bay of Bengal, they pick up moisture and when they strike against the Eastern Ghats they cause heavy rain on the east coast of India. Hence, the East Coast of southern India or the Tamil Nadu coast receives more rain in winter than in summer. In other words, we can say that Chennai has more rains only after the fury of the monsoons is over in most parts of the country in the months of October and November.
Ans 1(iii): The months of October and November are a period of transition from hot rainy season to dry winter conditions. In the second half of October, the mercury begins to fall at a rapid speed, especially in the northern India. The low pressure conditions, which were prevailing in the north India, due to hot season, now set transferred to the Bay of Bengal by November. This shift causes cyclonic depression in Andaman Sea. These tropical cyclones cause heavy and wide spread rains on the eastern coasts of India. So often they become destructive and the thickly populated deltas of Godavari, the Krishna and the Kavery are frequently struck by the cyclones which cause a lot of damage to life and property in these areas.
Ans 1(iv): Rainfall is low in some parts of Rajasthan, Thar Desert and Gujarat because there is no relief in these areas to check the Arabian Sea branch of Monsoons. The Aravalis lie parallel to the direction of the monsoons as such the monsoons bypass Rajasthan and Gujarat unobstructed and so, without giving any rain. Moreover, during summer season the temperature of these parts in Rajasthan including Thar Deserts is so high that the monsoons while passing over these areas get dry and do not cause any rain.
There is low rainfall on the leeward side of the Western Ghats and in interior of Deccan Plateau because that area comes in the rain shadow area. The Western Ghats on the western side and the Eastern Ghats on the eastern side do not allow the rain bearing winds to bypass them as such leeward side of the Western Ghats and in interior parts of Deccan Plateau get very low rainfall.
Q.2: What is an ‘Equable Climate’? Give example.
Ans: The coastal regions, influenced by the cool sea breeze, are known for their equable and moderate climate. The climate of coastal regions is known s Equable Climate.
Q.3: What is ‘Extreme Climate’? Give examples.
Ans: The climate in which the summer is extremely hot and winter is extremely cold, also known as Continentality. This type of climate is found in the arid regions of Rajasthan and south-west Punjab. Continentality increases with increase in distance of the place from sea.
Q.4: What is ‘Rain Shadow’?
Ans: Rain Shadow
That side of mountain which does not get much rain is known as the Rain Shadow. The wins after crossing the summits of the mountains descend along the slopes on the other side of the mountains, but in descending they get warmed up and become dry. The other reason is that the moist winds may not cross over the other side of the mountains which are too high as is the case with the Himalayas which render Tibet a dry region.
The dry side of the mountain is called the Leeward side and the rainless area on the leeward is called the Rain Shadow.
That side of the mountain where moisture laden winds strike and bring rain is called the Windward side.
Q.5: What are the elements of Weather and Climate?
Ans: The elements of weather and climate are the same which are - temperature, precipitation, humidity, atmospheric pressure and wind.
Q.6: Which place in India records the highest rainfall in the world?
Ans: Mawsynram is the rainiest place in India as well as in the world.
Q.7: Which part of India experiences the highest range of temperature in a day?
Ans: thar Desert in Rajasthan.
Q.8: Name the season in which Eastern Coast (Coromondal) receives rainfall.
Ans: Winter season.
Q.9: What are Jet Streams?
Ans: Jet Streams are the fast blowing westerly winds found in a narrow zone at high altitudes above 12000 m in the troposphere. A number of separate jet streams have been identified whose speed varies from 110 km/hr to 184 km/hr.
Q.10: What are the reasons behind the disasters like flood, cyclones etc. along the coastal regions of Orissa and Andhra Pradesh?
Ans: The cyclonic disturbances affecting the coastal regions of Orissa and Andhra Pradesh occur due to the tropical cyclones during the monsoons as well as in October - November. During monsoons, these disturbances are caused by tropical cyclones which are a part of easterly flow.
During October - November with the apparent movement of sun towards the south, the low pressure trough over the northern plains is shifted towards the Bay of Bengal. This shift is associated with occurrence of cyclonic depressions which originated over the Andaman Sea. These cyclones while crossing the Eastern Coasts cause heavy and widespread rainfall. Sometimes, these tropical cyclones arrive at the coasts of Orissa, AP, West Bengal and Bangladesh and cause great damage to life and property.
Q.11: Why Chennai has more rains only after the fury of the monsoons is over in most parts of the country?
Ans: Refer to the Answer of Q. No.1 (ii) above.
Q.12: Write short notes on:
(a) Loo
(b) Kaal Baisakhi
(c) Mango Shower
(d) Mahawat
Ans:
(a) Loo :
These are strong, gusty, hot, dry winds blowing during a day over the North and North-Western India. Direct exposure to these winds may even prove to be fatal.
(b) Kaal Baisakhi :
During the months of April and May the localized thunderstorms associated with violent winds, torrential downpours often accompanied by hail are known as the Kaal Baisakhi. This term is more popular in West Bengal.
(c) Mango Shower :
Towards the close of the summer season, pre-monsoon showers are common especially, in Kerala and Karnataka. They help in the early ripening of mangoes, and are often referred to Mango Showers.
(d) Mahawat :
The total amount of rainfall over the northern plains during winter is locally known as ’Mahawat’. It is important for the cultivation of Rabi crops.
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