NCERT Class 11 Geography Chapter 20 Climate

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NCERT Class 11 Geography Chapter 20 Climate

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Climate

Chapter: 20

GEOGRAPY [ PART – II ]

SHORT ANSWER TYPE QUESTIONS

Q.1. What do you understand by the term “Climate”?

Ans. Variation in the weather conditions continuously observed over a large area for at least three decades is called climate.

Q.2. What are seasons?

Ans. The common pattern of the weather (i.e. cool or hot, cloudy or bright) for months is called season. These are: winter, summer, rainy seasons in general while spring, summer, rainy, pleasant, autumn and snowfall season in particular.

Q.3. What influences have the Himalayas 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 rain bearing clouds to pour in India. The Himalayas give India, a touch of tropical climate, hot and wet summers and dry winters.

Q.4. What have given rise to variety in lives in people?

Ans. Seasonal contrasts in terms of temperature and precipitation take place in the interior of the country and these have given rise to variety in lives of people. E.g. Style of house construction, eating habits, dresses etc.

Q.5. What is Coriolis force?

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.

Q.6. Describe the pressure and wind conditions of India during winter.

Ans. High pressure area is formed at the north of the Himalayas and cold icy winds starts blowing towards Indian ocean to the south (i.e. low pressure area).

Q.7. Describe the pressure and wind conditions of India during summer.

Ans. Low pressure area 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.

Q.8. What do you understand by upper air circulation?

Ans. This is the region over which westerly winds (i.e. Jet Streams etc.) flow. These are high velocity winds blowing through a narrow zone in the troposphere.

Q.9. What are the causes of wind-reversal?

Ans. (i) High pressure area formed over the Arabian sea. 

(ii) Formation of Inter Tropical Convergence Zone (I.T.C.Z.) during summer over the Ganga plain.

(iii) High pressure area is formed at 20°g over the Indian ocean.

(iv) Formation of high pressure area over Tibetan Plateau above the sea level.

(v) Replacement of subtropical westerly jet by the easterly jet stream.

Q.10. What is El Nino?

Ans. The appearance of warm ocean current recurring every 5-8 years or so in E. Pacific off South America is called El Nino. It warms the nutrient-rich waters along the coasts of Equador and Peru and is an important factor in global weather.

Q.11. What does the word ‘Monsoon’ imply?

Ans. The word Monsoon is said to be derived from the Arabic word Mausam meaning season. The word was first applied to the winds blowing over the Arabian sea. Monsoon implies seasonal reversal of the wind pattern over the year. Monsoon winds are those seasonal or periodic which change their direction with the season. These winds blow from sea to land for six months during summer and from land to sea during winter for four months. Thus with the change of season the pattern of winds temperature and rainfall changer.

Q.12. Mention two factors which contribute to the development of the Indian monsoon.

Ans. Two factors are temperature and air pressure.

Q.13. Mention two main seasons of the Indian climate.

Ans. Two main seasons are:

1. South-west monsoon season.

2. North-east monsoon season.

Q.14. Name two transitional seasons of India with their months.

Ans. Two transitional seasons are:

1. The hot weather season (March to May).

2. The cold weather season (December to February).

Q.15. Mention local names of the thunderstorms of Assam and Bengal.

Ans. The local name of the thunder-storms in Assam is Bordoichilla and in Bengal, it is called Kalbaisakhi.

Q.16. What is the direction of wind in Kerala during the retreating monsoon season?

Ans. The direction of the winds in Kerala during the retreating monsoon is north-east and east.

Q.17. Where do you find polar type of climate in India?

Ans. The polar type of climate is found in Jammu & Kashmir, Himachal Pradesh and Uttaranchal.

Q.18. Mention the most comfortable areas of India in cold weather season.

Ans. The most comfortable areas in cold weather season are the interior parts of Karnataka, Andhra Pradesh and Tamil Nadu.

Q.19. Mention the areas of per humid climate in India.

Ans. The per humid areas are Mizoram, Tripura, Meghalaya, Lower Assam and Arunachal Pradesh in N.E. India and western coast of India, south of Goa.

Q.20. What are mango showers?

Ans. In Kerala, thunderstorm rain occurs in April and May and is known as the mango showers. This shower of pre-monsoon is useful to the crop of mango.

Q.21. Which type of climate is found in India?

Ans. Tropical monsoon climate.

Q.22. Name the hottest place in India.

Ans. Barmer (50°C) in Rajasthan.

Q.23. Name the rainiest place in India.

Ans. Mawsynram near Cherapunji (1080 cm) in Meghalaya.

Q.24. Name the coldest place in India.

Ans. Dras (Kargil) -45°C.

Q.25. Name the state with lowest annual range of temperature.

Ans. Kerala.

Q.26. What is October heat?

Ans. The oppressive weather due to high temperature and high humidity in the month of October.

Q.27. Name the coastal states struck by tropical cyclones. 

Ans. Tamil Nadu, Andhra Pradesh, West Bengal and Orissa.

Q.28. What is the cause of winter rainfall on south-east coast of India?

Ans. North-east monsoons.

Q.29. What is pre-monsoons?

Ans. Before the advance of monsoons, some local winds give pre-monsoon rainfall.

Q.30. Which part of India gets winter rainfall due to retreating monsoons?

Ans. Coromandal coast.

Q.31. State three dominant characteristics of the Indian monsoons.

Ans. The Indian monsoons have the following dominant characteristics:

(i) Change in direction of winds.

(ii) Uncertain variable rainfall.

(iii) Monsoons provide climatic unity in the sub-continent.

Q.32. Name the four seasons of India. Mention their months also.

Ans, 1. The cold weather season (December to February).

2. The hot weather season (March to May).

3. Rainy season or advancing monsoon (June to September).

4. The season of retreating monsoon (October and November).

Q.33. What are the coldest parts of India and why?

Ans. The Himalayan region including Jammu and Kashmir, Himachal Pradesh are the coldest parts of India. The minimum temperature is -40°C at Dras (Kargil). This is due to the fact that this place lies at a great altitude. These regions get heavy snowfall during winters and temperature remains below freezing point.

Q.34. What do you understand by the term “Loo”?

Ans. Loo: It is a hot and dry wind that blows from west in the months of May and June in the northern part of India. It increases the day temperature ranging between 45°C and 50°C. It is harmful to the human body.

Q.35. Give reasons why Mawsynram (Cherapunji) get very high rainfall.

Ans. Mawsynram is the rainiest spot in the world as it receives the heaviest amount of rainfall in a season. The location of Mawsynram is as such that it is surrounded by the hills of Khasi, Garo, Jaintia in the Meghalaya Plateau which is funnel-shaped. The Bay of Bengal branch of the S.W. monsoon is trapped by these hills resulting in the heaviest amount of rains.

SHORT ANSWER TYPE QUESTIONS

Q.1. What is a jet stream?

Ans. The high velocity winds blowing in the upper troposphere are termed as Jet Streams. It blows with a steady velocity across the Asian continent at latitude north of the Himalayas roughly parallel to Tibetan Highlands. These highlands act as the barrier in its path. So it is bifurcated into two branches namely:.

(i) Westerly jet stream. and

(ii) Easterly jet stream.

The weather conditions of India are influenced to some extent by westerly jet stream in winter and by easterly jet stream in summer. The westerly jet stream brings the western disturbances into north-west part of Indian plains and cause widespread winter rain which benefits the rabi crops. The easterly jet stream brings the tropical depressions which controls the distribution pattern of south-west monsoon rainfall in the country.

Q.2. Why is India’s climate described as monsoon type?

Ans. This is because:

(i) India is located in the tropical area between 20°N and 20°S.

(ii) Half of India in the north falls in sub-tropical zone. Here blows the North-East Trade winds. These help in formation of low pressure areas during summer.

(iii) Here exists the phenomenon of pressure and surface winds, upper air circulation, westerly disturbances and tropical cyclones.

(iv) Here acts the phenomenon of ENSO (El Nino combined with Southern Oscillations).

Q.3. What are ‘breaks’ in the monsoon?

Ans. The monsoon winds blow in southwest direction on the west coast. These are highly charged with water vapour. It advances rapidly over west coast. The rains begin rather suddenly in the first week of June. The sudden onset of rain is often termed as monsoon burst. The rainfall is heavy accompanied by thunder and lightning. The rain is so sudden and heavy that it appears as a balloon of water has been burst. The sudden onset of monsoon is called the burst of monsoon or breaking of monsoon.

Q.4. State three dominant characteris- tics of the Indian monsoon.

Ans. The Indian monsoon is characterized by the following three dominant factors:

(i) Seasonal reversal of direction in wind system. The monsoon winds blow from land to sea in winter and from sea to land in summer.

(ii) Seasonal heavy rainfall and drought are common features of the Indian monsoon.

(iii) In spite of local variations in climatic conditions, it unites the whole country in a single climatic thread of monsoon type of climate.

Q.5. What is the importance of the western disturbance in the climate of India?

Ans. The cyclones or depressions developed near the Mediterranean sea are termed as western disturbances. They move towards India through Iran and Pakistan. They come under the influence of westerly jet streams which bring them to northern part of India in winter season. They cause widespread rain in the north-west part of the Indian Plains. This winter rain is very useful and beneficial to the rabi crops.

Q.6. Describe the effect of El-Nino on Indian monsoon.

Ans. El-Nino and the Indian monsoon: El-Nino is a complex weather system that appears once every five to ten years, bringing drough floods and other weather extend to different parts of the world. The system involves ocean and atmospheric phenomenon with the appearance of warm currents off the coast of Peru in the eastern Pacific and affects weather in many places including India.

El-Nino is used in India for forecasting long range monsoon rainfall. In 1990-91 there was a wild El-Nino event and onset of south-west monsoon was delayed over most parts of the country ranging from five to twelve days.

Q.7. How does the westerly jet stream help in bringing the western disturbances to the Indian sub-continent during winter?

Ans. The western disturbances originate near the Mediterranean sea in the winter. They move eastward. The westerly jet streams prevail over the Northern Plain of India in winter. Hence, these disturbances come under the influence of the westerly jet streams which brings them to the Indian subcontinent. They cause widespread rainfall in this region. This winter rainfall is very useful and effective for rabi crops.

Q.8. What are the three important factors which influence the mechanism of Indian weather?

Ans. The three important factors which influence the mechanism of Indian weather are

1. Surface, pressure and winds.

2. Jet stream and upper air circulation.

3. Western disturbances and tropical cyclones.

Q.9. Describe the characteristics of the Hot weather season.

Ans. (i) The global heat belt shifts northward. Eg. 38°C temperature in Deccan plateau during March while Gujarat and M.P.it is 42°C in April. In May, it rises to 42°C in north western parts of the country.

(ii) The period from March to May remains the hot weather season in India.

(iii) Rise in temperature but fall in air pressure is observed in northern part of the country.

(iv) “Loo” starts blowing.

(v) Duststorms bring down the temperature.

(vi) Pre-monsoon showers including mango temporarily showers are received in the south India.

Q.10. Describe the characteristics of the Rainy season.

Ans. (i) Low pressure condition over the northern plains spurts up.

(ii) South-east trade winds starts blowing in a south-westerly direction bringing south-west monsoon.

(iii) Highest rainfall in Cherrapunji and Mawsynram and 250 cm in Western Ghats. Scanty rain in regions lying in the rain shadow area.

(iv) Breaks in rainfalls and burst of monsoon conditions are experienced.

(v) Quantum of rainfall is determined on movement of monsoon trough or the ITCZ (the Inter Tropical Convergence Zone) north to south and vice-versa.

Q.11. What is extreme? Name two places of extreme climate in India.

Ans. Extreme climate: The climate which has high annual range of temperature and great variation in the amount of rainfall over the year is known as extreme climate. It is also called continental or interior climate as it is found in the interior parts of the continents. For examples, Jodhpur, Delhi and Kanpur.

Q.12. What are heat waves and cold waves?

Ans. Heat waves: During the months of March to July, spell of abnormally hot weather is occasionally experienced in certain parts of India. These spells move from one region to another and are called heat waves. They have their maximum temperatures more than 6°C above normal. A heat wave with a maximum temperature of 8°C or more above the normal is considered to be severe. Heat waves occur in most of the country except the southern states of Kerala and Tamil Nadu, Pondicherry and Lakshadweep, Andaman and Nicobar Islands.

Cold waves: During the months of November and April, cold and dry winds blow in northwest India. When they attain minimum temperature below 6°C from the normal they are called cold waves. Severe cold waves occur in Jammu & Kashmir, Punjab, Uttar Pradesh, Rajasthan and Madhya Pradesh. The frequency of severe cold waves decreases towards the east and south. The southern states are almost free from cold waves.

Q.13. How have the easterlies assumed the name Trade’?

Ans. The word Trade has been derived from the German World Track. Track means the path on which winds blow in the same direction throughout the year and on the same course. The easterlies characterise these qualities. Hence they have assumed the name trade.

Q.14. Mention four characteristics of the monsoon rains.

Ans. (i) The beginning of the rains sometimes is considerably delayed over the whole or a part of the country.

(ii) There are prolonged breaks of rains, in July-August when summer crops need plenty of water.

(iii) The rains sometimes end considerably earlier than usual causing great damage to standing crops and making the sowing of winter crops difficult.

(iv) The rainfall persists more than usual in one part of the country and desist from another part.

(v) The summer rainfall comes in heavy downpour leading to considerable run off and soil erosion.

Q.15. What is a Rain Shadow?

Ans. That side of the mountain which does not get much rain is known as the rain-shadow. The winds after crossing the summits of the mountains decend along the slopes on the other side of the mountain which are too high as in the case with the Himalayas which render Tibet a dry region. The dry side of the monsoon is called the leeward side and the rainless area on the leeward side is called the rain-shadow. That side of the mountain where moisture laden winds strike and bring rain is called the windward side. When the moisture laden winds blow at right angle to the mountain ranges, we can observe these windward and leeward sides distinctly.

Q.16. Mawsynram receives the highest amount of rainfall in the world. Why?

Ans. Mawsynram is the place of highest rainfall in the world. It is located on the southern slope of Khasi hills at a highest of 1500 m above sea level. This place is inclosed by hills on three sides. The relief features give this place a funnel shaped location. The Bay of Bengal branch of monsoon is trapped in these hills. These winds try to get out of it. These are forced to rise again and again resulting in heavy rainfall. In the year of 1961 on count of 2262 cm of rainfall was recorded here.

Q.17. Discuss the reasons for uneven distribution of rainfall in India.

Ans. Reasons for uneven distribution of rainfall in India:

(i) Heavy rainfall is recorded in hill and forest areas because of altitude and dense forests which make the atmosphere cool and force the raindrops fall. E.g. Assam, the Ganga Delta, the Western Ghats, the Western Coastal regions.

(ii) Areas without elevated mountains only receive scanty rainfall because of their failure to strike against rain bearing clouds (winds) of the monsoon seasons. E.g. Scanty rainfall in Rajasthan due to Aravallis range of mountains.

(iii) Areas falling in the rain shadow or leeward sides receive sparse rainfall. E.g. Eastern side of the Western Ghats or Ladakh.

(iv) Areas falling first in the way of the rain bearing winds receive more rainfall as compared to the areas falling the last. E.g. Kolkata falls first in the way of Bay of Bengal branch of monsoon therefore, it receives more rainfalls than Delhi.

Q.18. Define the western disturbances and their effect on India.

Ans. Western disturbances are cyclonic depressions that take place over Andaman and Nicobar Islands as also over the East Mediterranean sea. These travel eastwards across Iraq, Iran, Afghanistan and Pakistan before they reach the north-western parts of the country. They receive moisture while blowing over the Caspian Sea in the north and Persian Gulf in the south.

The western disturbances are preceded by warm weather or sudden rise in temperature. These cause light rainfall in the northern plains of India. These cause snowfall in the northern Himalayas. The rainfall as also snowfall of winter season are beneficial to the rabi crops i.e. wheat, barley etc.

Q.19. What is the inter tropical convergence zone (ITCZ)? 

Ans. The ITCZ is a low pressure zone located at the equator where trade winds converage and so it is a zone where air tends to ascend.

Q.20. What is meant by bursting of monsoon? Name the place of India which gets highest rainfall.

Ans. The sudden onset of the moisture-laden winds associated with violent thunder and lightning is often termed as the break or burst of the monsoon.

Mawsynram in Meghalaya is the place where highest rainfall occurs.

Q.21. Define climatic region? What are the bases of Koppen’s classification?

Ans. A climatic region is a homogeneous climatic condition which is the result of a combination of factors. The bases of Koppen’s classification are:

(i) Temperature.

(ii) Rainfall.

Q.22. Which type(s) of cyclones cause rainfall in north-western India during winter? Where do they originate?

Ans. The farmers get rainfall in winter from western disturbances-the temperate cyclones. They come from Mediterranean sea.

Q.23. What part do the cyclones play in the season of advancing southwest monsoon? Under what conditions can the northern plains get a fair amount of rainfall? When do they receive floods?

Ans. The cyclones are formed at the head of the Bay of Bengal and then enter into the main land. These pass along the axis of the monsoon trough or I.T.C.Z. of the low pressure. Northern plains would get a fair amount of rainfall only when the monsoon trough lie in the plains. We know that the monsoon trough and its axis keep on moving northward or southward. Its movement towards south determines the quantum of good rainfall over the plains.

However, when the monsoon trough shifts closer to the Himalayas, there are longer, dry spells in the plains while widespread rains occur in the mountainous catchment areas of the Himalayan rivers. This condition causes devastating floods spreading damage to life and property in the plains. The frequency and intensity of tropical depressions too determine, the amount and duration of monsoon rains.

Q.24. Explain why does Chennai receive more rainfalls in winter than in summer.

Ans. Chennai is the capital city of the state of Tamil Nadu. It lies on the Coromandel coast on the eastern coastal plain. This region generally receives rainfall in winters and also in summers. However, quantum of winter rainfall is always recorded larger than it is in summer. This part of the land lies at rain shadow of Western Ghats therefore, does not receive much rainfall during south-west monsoon season i.e. in summer.

The south-west monsoon is replaced by the north-east trade winds and they pick-up moisture while crossing the Bay of Bengal. These retreating monsoon winds therefore, become rain fetching winds, especially for Chennai in Coromandel coast.

Q.25. Discuss how does monsoons act as a unifying factor in India. Justify your answer with suitable examples.

Ans. It is true that there is a great diversity in climatic conditions of India due to differences in relief features, altitude, location etc. However, due to south-east monsoon winds, India has primarily a monsoon type of climate all over its terrestrial areas. The whole country is influenced by the same order of seasons. The monsoonal rhythm of season is a great unifying force in India.

Monsoons control the atmosphere conditions of the country. Throughout the country, the summers are wet and winters are dry due to on-shore and off-shore winds that blow over every nook and corner of India. The distribution of rainfall is uneven. Agriculture depends upon monsoon rainfall resulting in a subsistence agriculture. Agriculture in India is a gamble on monsoons. The folk songs like Kajari of Bhojpur and Malhar of Braj (Mathura) are associated with monsoonal rains. Thus, monsoons provide a natural base for a uniformity throughout the country.

Q.26. Which parts of India receive heavy rainfall, moderate rainfall, low rainfall and scanty rainfall?

Ans. Areas of Heavy Rainfall: Assam, the Ganga Delta, the Western Ghats, Western Coastal Regions and mountainous regions of Himachal Pradesh.

Areas of Moderate Rainfall: Madhya Pradesh, Orissa, Chhotanagpur, West Bengal, Bihar, eastern U.P., north-eastern Punjab, eastern parts of Tamil Nadu and eastern slopes of Western Ghats.

Areas of Low Rainfall: The Deccan plateau, Western U.P., South-eastern Punjab, Eastern Rajasthan and some parts of Kashmir.

Areas of Scanty Rainfall: Western Rajasthan, Kutch, South-eastern parts of Haryana and north-eastern Kashmir.

Q.27. Why does the rainfall gets on decrease as we go up the Ganga Valley but increase as we go up the Indus Valley?

Ans. We know that the monsoons in summer rise from Bay of Bengal and Arabian Sea simultaneously. The Bay of Bengal branch causes heavy rainfall in the Brahmaputra valley and Assam hills. The rain bearing winds strike at the lofty peaks of the Himalayas there and get deflected towards the west. Thus, they move up the Ganga Valley but as they proceed westwards, they become drier and cause less rain with every steps towards the west of the plains. Owing to this decreasing trend, Kolkata receives 119 cm, Patna 105 cm, Allahabad 76 cm and Delhi 56 cms rainfall. Distance from the sea also decreases the quantum of the rainfall in the areas proportionately. Places near the sea get more rainfall as compared to the places lying for away from the sea. As we move away from the Bay of Bengal to Punjab, the distance from the sea also becomes more and more leading lesser and lesser rain.

Another branch of the monsoon i.e. south- east monsoon blows from the Arabian sea. It enters in India and blows over Rajasthan but the Aravalli Hills there cannot check them and so, these winds pass on without raining there. At their access to Himachal Pradesh, these monsoon winds strike with the lofty peaks of Himalayas and cause heavy rains there. The Bay of Bengal branch also joins here and thus, the rain goes on increasing as we go up the Indus Valley.

Q.28. Describe the various conditions of retreating monsoon season and distribution of rain.

Ans. The monsoon starts retreating in the months of October and November. In this way, the speed of low air pressure becomes slow and replaced by the higher air pressure. As a result of this, the monsoon starts going back. The access of monsoon also lessens due to gradual detereoration of power. Its influential area till then is seeped into Indian lands. The conditions of surface winds start reversing and monsoon shifts back from northern plains by October month every year.

Conditions of Season: In the month of October and November, the dry winter season starts replacing the rainy season. The sky becomes clear due to removal of monsoons and the temperature starts increasing. It is popularly called the ‘October heat’ or the humidity and heat of Kwar according to the Hindu theology.

The low air pressure of north-west India transfers to the Bay of Bengal in the month of November. During this period, Andaman sea again starts raising cyclones. The summer solstice cyclones are destructive in nature. These strike the deltas of the Godavari, Krishna, Mahanadi and Kaveri rivers of Peninsular India. Sometimes, these reach upto Sunderbans and Bangladesh also. Coromandel coast receives most rainfall due to these cyclones.

Q. 29. Give three important character-istics of the summer monsoon rainfall.

Ans. The three important characteristics of the summer monsoon rainfall are as under:

(i) Monsoon Burst: The sudden onset of rain is termed as monsoon burst. It is the main characteristic of summer monsoon rainfall. It brings rainfall suddenly-a rainfall without warning. This rain brings relief to the summer affected people and land.

(ii) Breaks: The other characteristic of south-west monsoon is the tendency of breaks or spell of dry weather. These breaks are associated with the tropical depressions which have fluctuating pattern. The amount as well as the intensity of rainfall is also determined by the frequency of these depressions.

(iii) Declining trend: The summer monsoon rainfall is decreasing with the increasing distance from the sea such as: Kolkata receives rainfall 119 cm, Patna 105 cm, Allahabad 76 cm and Delhi 56 cm.

Q.30. The amount of rainfall in a year at Jaisalmer rarely exceeds 12 centimetres. Give three main reasons in support of this statement.

Ans. Following are the reasons for low rainfall at Jaisalmer:

(i) Jaisalmer lies to the west of Aravallis in Rajasthan. The Bay of Bengal branch of monsoon becomes dry when it reaches this area.

(ii) The direction of Arabian sea branch of monsoon is from south-west to north-east. The Aravalli mountain also has the same direction i.e., it lies from south-west to north-east. Hence they do not obstruct these monsoon winds. Hence there is no rainfall.

(iii) This area lies in the subtropical high pressure belt, where winds have decreased moisture contents which do not give rainfall.

(iv) This area lies away from the high Himalayas and hence does not get rainfall at all.

Q.31. “The distribution of rainfall in India is not uniform.” Give three important reasons in support of this statement.

Ans. After observing rainfall distribution map of India, the distinguished characteristics are that the rainfall is highly unevenly distributed:

1. The rainfall declines abruptly from Bengal coast to west and north-west in the northern plains.

2. The rainfall in the peninsular plateau decreases eastward. 

Such uneven distribution is determined by the following factors:

1. Presence of geographic features such as the Western Ghats, the foothills of Himalayan mountain and the N.E. hills. They receive annual rainfall more than 185 cm and it represents only 10% of country’s area.

2. The direction and distance covered by monsoon branches is another factor creating variation in the rainfall distribution in the northern plains and interior Deccan Plateau. On this basis, 30% of country’s area receives less than 60 cm of annual rainfall and remaining 60% of the area receives between 60 cm to the 185 cm.

Q.32. The western part of Rajasthan remains almost dry during south-west monsoon season. Give three important reasons in support of this statement.

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 Sea branch of monsoon winds. The Aravalli mountains are not very high.

(iii) The direction of the Aravalli mountains is parallel to the direction of Arabian Sea winds. Hence, these winds cross over Rajasthan without giving rainfall.

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

Q.33. What is the Inter-Tropical Convergence Zone (I.T.C.Z.)?

Ans. The Equatorial low pressure belt near the surface of the Equator is called Inter-Tropical Convergence Zone. It lies over 25°N in the summer season. It forms a zone of convergence over Northern India and Pakistan. The equitorial low pressure zone invites the inflow of winds from different directions. It also attracts the maritime air from the Southern Hemisphere. This moist air current is known as south-west monsoon.

Q.34. The coastal areas of India do not register any significant change in temperature even during winter and summer. Why?

Ans. The coastal areas of India do not register any significant seasonal change in temperature due to the following reasons:

(a) The influence of surrounding sea keeps them with equable temperature conditions such as the mean monthly temperature of Trivendrum and Mumbai fluctuates very slightly.

(b) As we know the sea waters are reservoirs of the warmth and they get heated and cooled down slowly due to convectional processes of heating and cooling and, hence, they remain warmers in winter and cooler in summers, keeping the coastal areas equable in temperature.

(c) The warm ocean currents too, keep the coastal areas with almost equable temperature throughout the year.

Q.35. Give reasons:

(i) North-western India receives rainfall in winter also.

Ans. The north-western plains of India experience winter rainfall due to the invasion of the western disturbances rising from the Mediterranean sea, steered by the westerly jetstream. As the western disturbances are associated with the cyclonic winds, they bring rainfall.

(ii) A high pressure centre develops over northwestern India in winter.

Ans. In winter the sun shines vertically over the Tropic of Capricorn and the north western part of India away from marine influence experiences low temperature and high atmospheric pressure. The minimum temperature is much below than 10° to 12°C. So a high pressure centre develops over this part of the country.

(iii) During the southwest monsoon season, winds in Ganga valley generally blow from east to west.

Ans. The Bay of Bengal current splits into two branches-one advances towards North-Eastern India, Myanmar, Thailand and the other crossing the Bay of Bengal directed westward into the monsoon trough of low pressure. The wind in Ganga plain therefore blows from the east to west and the rainfall decreases westward.

(iv) The annual range of temperature is more in Delhi than in Mumbai.

Ans. The distribution of temperature is determined by some factors. The places located far inland have a greater range of temperature than those located near the sea. Delhi is located far away of sea therefore it has more annual range of temperature than that of Mumbai as Mumbai is located near the sea.

Q.36. Write two characteristics of Mango showers.

Ans. (i) Mango-showers are actually pre- monsoon showers or onset of summer monsoons. These are common in Kerala and coastal areas of Karnataka in the month of March and April.

(ii) These are locally known as mango-showers because these help in the early ripening of mangoes. These are local storms which develop due to high temperatures.

Q.37. What is the average amount of rainfall over the plains of India?

Ans. The average amount of rainfall over the plains of India decreases from north-east to north-west. Hence, the plain is divided into three zones of average amount of rainfall. They are as under:

Name of Zones	Average Amount of Rainfall in Centimeters
(i) The plains of Bihar, Bengal and Eastern U.P	100-200
(ii) The plains of central and western U.P	60-100
(iii) The plains of Punjab and Haryana	40-60

Q.38. Describe two main features of Kal-baisakhi.

Ans. Kal-baisakhi are local thunder storms experienced in the month of Baisakh (April) in West Bengal. The North-Westerly and Northerly winds which blow in the N.E. part of India cause very sharp showers in this region. These winds are called Nor-Westers. These cause evening thunderstorms which cause havoc in this part. The word Kal-baishakhi is local name for these storms. It means Kal = calamity, Baisakhi = month of Baisakh (calamity of the month of Baisakh).

Q.39. India would have been an arid land or desert, if there had been no phenomena of monsoons. Explain it giving four points.

Ans. Monsoons are the rain bearing winds in India. India’s climate, (temperature and rainfall) depend entirely on monsoons. India would have been arid, like West Asia, has there been no monsoons. The winds would have become dry till these reached western parts (like Rajasthan). Without monsoons, there would not have been dense forests in India. It would have the desert vegetation like bushes and shrubs. Monsoons are wet and these pick up moisture from Indian oceans, but here the prevailing winds would have come from land and would have been dry.

Q.40. Distinguish between rainfall and precipitation.

Ans.

Precipitation	Rainfall
1. In this process, the condensed water from the clouds, falls through the atmosphere and reaches the earth’s surface as rainfall, sleet, hail or snowfall.	1. It is only one form of precipitation.
2. This process results in aggregating million of cloud particles into a smaller number of bigger droplets.	2. In this process, the condensed raindrops drops change into bigger drops of water and fall through the atmosphere on the surface of the earth.
3. Precipitation is observed in the forms of sleet, snowfall and hail etc.	3. It is in single form i.e. fall of water drops on the surface of the earth.

Q.41. Distinguish between windward side and leeward side.

Ans.

Windward side	Leeward side
It is that side of the mountain which comes across the striking winds and gets heavy rainfall.	The other side of mountain where winds descend after shedding much of the rainfall.

Q.42. Distinguish between the south-west monsoon and the north-east monsoon.

Ans.

South-West Monsoon	North-East Monsoon
1. These monsoon winds blow northward from the Arabian sea and the Bay of Bengal.	1. These monsoon winds blow from north-east towards the sea-side.
2. These monsoon winds blow from June to September.	2. These winds blow from October to November.
3. These winds cause country-wide rainfall.	3. These cause rainfall only in Coromandel coast including Tamil Nadu when these strike at the wetlands of the Eastern Ghats.
4. These blow from oceanic high pressure areas towards the low pressure areas of land.	4. These winds blow from land to sea as a result of reversal in the direction of wind or start of retreating monsoon season.
5. These winds blow during advancing monsoon season.	5. These winds blow during retreating monsoon season.

Q.43. Distinguish between:

(i) Equable climate and Extreme climate

Ans.

Equable climate	Extreme climate
1. This climate is neither too hot in summer nor too cold in winter.	1. In this climate summers are very hot and winters are very cold.
2. The annual and daily range of temperature is low.	2. The annual and daily range of temperature is very high.
3. This climate is generally found in coastal areas and is called maritime climate.	3. This climate is generally found in inland areas and called continental or extreme climate.
4. The rainfall is moderate and well-distributed throughout the year.	4. The rainfall is low and is limited to summer season.
5. Mumbai has an equable climate.	5. Delhi has an extreme type of climate.

Q.44. Which one of the given three graphs-A, B and C, depicts the climatic data of Delhi? Give one reason each with reference to

(i) temperature, and its range.

(ii) amount of rainfall. and

(iii) rainfall regime in support of your answer in selecting the graph.

Ans. Graph ‘C’ depicts the climatic data of Delhi because 

(i) The summer temperature is as high as 40°C. The winter temperature is 7°C only. The range of temperature hence is quite high i.e. 33°C.

(ii) The amount of rainfall is quite less, 70 cm, in comparison to the other two stations.

(iii) Delhi gets most of its rainfall in the months of July, August and September. Other months are almost dry. Other two stations get heavy rainfall in comparison to Delhi.

Q.45. ‘Monsoon is a gamble for the Indian farmers’. Explain.

Ans. Agriculture prosperity of the country depends very much on timely and adequately distributed rainfall. If it fails, agriculture is very badly affected. For this reason it is often said that the Indian agriculture is a gamble in the hands of the monsoon.

The failure of summer monsoon results in famines and food shortage. Therefore, monsoon is a gamble for the Indian farmer.

Q.46. Given below are the Climatic graphs of three stations. Which one of the given graphs depicts the climatic data of Jodhpur? Give three reasons with reference to

(i) temperature and its range.

(ii) amount of rainfall. and

(iii) rainfall regime in support of your answer in selecting the graph.

Ans. (i) Graph ‘C’ depicts the climatic data of Jodhpur. Reasons (i) Jodhpur is located in the desert area of western Rajasthan. The graph shows that during summer months temperature is very high. It is more than 40°C in the month of April and May. During winter season the temperature goes down to 23°C. Hence the annual range of temperature is very high (43-23)=20°C.

(ii) The rainfall is very low. It is about 100 mm in the month of August.

(iii) Whatever rainfall Jodhpur gets, is in the months of July and August. October to May are dry months.

Q.47. Why is Shillong has more rains than Kolkata?

Ans. Shillong receives an annual rainfall of 225 cm while Kolkata gets an annual rainfall of 119 cm. Bay of Bengal branch of the Monsoon gives rainfall in these areas. One branch of Monsoon moves up the Brahmaputra Valley. The topographical location (hills of Meghalaya) is responsible for more rainfall at Shillong. The other sub-branch of the Monsoon moves up the Ganges Valley. But there is no relief barrier near Kolkata to cause heavy rainfall.

Q.48. South-east monsoons are generally interspersed with spells of dry weather. Why?

Ans. It is one of the salient features of S.W. monsoon winds to have breaks or spells of dry weather in between two successive showers. Such dry spells are caused due to inflow of fluctuating tropical depressions. The amount as well as intensity of rainfall is determined by the frequency of these depressions. The rainfall by south-west monsoon is cyclonic. The time lag between two cyclones causes dry weather. The generally variable character of monsoon rainfall is caused by variations in the directions and frequency of tropical depressions. This leads to dry spells or sometimes drought conditions.

Q.49. Why is the western part of Rajasthan arid in spite of the Aravalli Hills?

Ans. The western part of Rajasthan is desert. It gets an annual rainfall less than 20 cm. This is due to the following Reasoning (R):s:

(i) Rajasthan is under the influence of S.W. summer monsoons. The Aravallis system lies winds parallel to the direction of S.W. monsoon winds coming from Arabian Sea. So this mountain system is unable to check these winds and hence, western Rajasthan is practically dry. The southern parts get some rainfall.

(ii) This area lies at a great distance from the Bay of Bengal. The Bay of Bengal monsoon becomes dry and lose its moisture when it reaches Rajasthan.

(iii) This area is away from the Himalayan region. So it does not come under the influence of monsoon giving rain in the sub-Himalayan region.

Q.50. Explain the important features of Winter Season of India.

Ans. By October, the rainy season comes to an end all over the country and the days become short and the night become long. The rays of the sun are not overhead. The air turns cooler in the plains marking the coming of the winter season.

The winter season lasts from November to February every year. In the Northern Plains, very cold wind blow making the winter months severe. December and January are the coldest months in the northern plain. The mean daily temperature remains below 21°C over most parts of northern India.

Most of the hilly areas receive heavy snowfall. January is the coldest month in the Northern Plains. The winter season in Peninsular India is mild as a result of the influence of the surrounding water bodies. The coromandel Coast receives heavy rainfall during this season.

The desert is cool during the day but cold at night. The air starts warming up in the month of March, and the weather is neither cold nor hot. This time of early summer is also called the spring season. Every part of our country regularly experiences this cycle of seasons.

LONG ANSWER TYPE QUESTIONS

Q.1. Describe the distribution of temperature during summer and winter seasons in India.

Ans. Winter Season: The winter season lasts from mid-November to February. The isothermal map of January shows the following characteristics:

1. The coastal regions have moderate temperature throughout the year. Hence, it is recordes 25°C in winter and 35°C in summer.

2. It decreases northwards. Hence, the region lying south of the Tropic of Cancer has 20°C and north of it has 10°C-15°C temperature.

3. The hilly regions remain ice-covered in the winter season.

4. The temperature in the winter season is well-marked in northern India as compared to Southern India.

5. The interior parts of the country are oldest areas with the mean daily maximum temperature varying 28°C in the peninsular region to 19°C in north-west.

6. The mean daily minimum temperature shows greater diversity during the season. It

varies from 24°C in peninsular to 5°C in north-west parts of the country.

7. The night temperature, sometimes, fall below freezing point under the influence of cold waves which affect the weather conditions in north-west India.

8. The lowest temperature is recorded in Ladakh. It is -40°C in Dras in Kargil.

Summer Season: (i) The highest temperature is registered in the northwest and west. Barmer is a place where the highest temperature is 50°C.

(ii) The isotherm of mean maximum temperature of 32.5° runs parallel from the Tropic of Cancer of Kanyakumari while the temperature increases from the south to north on the eastern coast. It varies from 35°C to 37.5°C. But it again goes down on Orissa and West Bengal coast.

(iii) Many parts in north-west and central part of India register 42.5°C temperature.

(iv) In northern India, the temperature goes upto 37.5° from Punjab to Chhotanagpur.

(v) The mean minimum temperature does not go below 20°C in northern India.

Q.2. Notwithstanding the broad climate unity, the climate of India has many regional variations. Elaborate this statement giving suitable examples.

Ans. The climate of India has many regional variations. But due to the influence of monsoons, India as a whole is considered a climatic unity. There are many factors which produce regional variations:

1. Temperature: In summer in the western deserts, temperature touches 55°C and it drops down to as low as minus 45°C in Leh. Churu in Rajasthan may record 50°C or more in June while in Tewang it is 19°C on the same day.

2. Rainfall: Mawsynram receives 1080 cm. in a year while Jaisalmer in Rajasthan rarely gets more than 9 cm during the same period.

3. Monsoons: The date of onset of monsoon and withdrawal of monsoon differ in various parts. The west coast has monsoon in the first week of June while the interior parts like Punjab have monsoon by the first week of July only.

4. Season: The southern parts of the country have uniform high temperatures throughout the year. There is no winter season in the south. On the other hand seasonal extremes are found in the north. In Spite of these differences and variations the climate of India is monsoonal in rhythm and character.

Q.3. Describe the pattern of rainfall distribution in India.

Ans. There is a great variation in the distribution of rainfall. Over 80% rainfall is received in the four rainy months. During cold weather, India receives about 25 cm of rainfall. The amount of rainfall however decreases rapidly in the interior of the peninsula. The average rainfall in India is about 125 cm but it has great spatial variations.

1. The highest rainfall occurs along the west coast, Western Ghats, the Himalayan areas and the southern hills of Meghalaya. It is more than 400 cm.

2. In the Brahmaputra valley and adjoining hills, rainfall is less than 200 cm.

3. Southern parts of Gujarat, east Tamil Nadu, northern peninsula, northern Ganga plain and Manipur get rainfall between 100-200 cm.

4. Parts of Andhra Pradesh, Karnataka and Maharashtra get the rainfall below 50 cm.

5. Rest of India gets rainfall between 50 to 100 cm.

Q.4. Explain the meaning of ‘onset’ and ‘withdrawal’ of the Indian monsoon.

Ans. Onset of Monsoon: Due to the rapid rise in temperature in May over north-west India the air pressure decreases and the low pressure is established there. To fill up this area of low pressure, the air is suck in from the Arabian Sea and Bay of Bengal. The south-east trade winds of the Southern Hemisphere also join the air circulation over India as the south westerly winds. The south west monsoon strikes on the coast of Kerala in the first week of June and slowly it extends northwards. It is the onset of monsoon.

Withdrawal of Monsoon: By the end of September the south-west monsoon becomes weak as the low pressure trough shifts southward. By the beginning of October the low pressure centres over northern parts move over the Bay of Bengal and by early November it moves over Karnataka and Tamil Nadu. By the middle of December the centres of low pressure is completely removed from the peninsula. It is the withdrawal of monsoon.

Q.5. Discuss Thornthwaite classifi- cation of Indian climate.

Ans. Thornth waite’s method is based on the concept of water balance. The relationship between precipitation and water need is called the water balance. If the precipitation is more than the maximum amount of evaporation and transpiration, the area is wet, if it is less than water need, it is dry. To determine water balance a clear cut distinction between actual evaporation and potential transpiration is necessary.

The principal water surplus areas in India are the Western Ghats of the peninsula which provide water to Krishna, Godavari and Kaveri rivers. Other areas are Meghalaya, eastern mountain ranges and Western Himalayas. The northern plains, Karnataka and Andhra Pradesh have almost no water surplus.

The greatest water deficient regions in northwest India include Rajasthan, Punjab and Haryana.

Based on moisture indices the following five climates are identified:

A Per humid: with I_m of 100 of more.

B Humid: with I_m between 20 and 100

C₂ Moist suv-humid: with I_m between 0 and 20

C₁ Dry sub-humid: with  I_m between 0 and -20

D Semi-arid: with  I_m between -40 to -20

E Arid: with  I_m of -40 and less.

Q.6. Regions receiving winter rainfall in north-west and southern India have different reasons. Explain.

Ans. Winter rainfall in north-west India: Northwest India receives winter rainfall from low pressure systems, called the western disturbances or depressions. These depressions originate from Mediterranean sea and Persian Gulf. They travel eastward across Iran and Pakistan and reach India during the winter season. They are generally active between December and February. They cause much rainfall over plain areas of northwest region of India. The rainfall caused by western disturbances decreases from north and north- west towards east.

Southern India: The Tamil Nadu coast in Southern India receives rainfall during October and November. It is caused by the North-east monsoons. During this season, several cyclonic storms develop in the Bay of Bengal which move from the north-east to south-west causing substantial rainfall on the coast of Tamil Nadu.

Q.7. Examine the factors which affect the climate of India.

Ans. Factors affecting the climate of India :

(i) Monsoon winds: India has a monsoon climate. It is controlled by monsoon winds. In summer, the monsoon winds blow from sea to land as S.W. monsoon. These on-shore winds give most of the rainfall to the country. In winter, the Monsoon winds blow from land to sea as N.E. Monsoon. These are dry winds.

(ii) Expanse of the country: India is a vast country. The northern part lies in the tropical region and experiences hot summers and cool winters. The southern part lies near the equator and has hot season throughout the year.

(iii) Location of the Himalayas: The Himalayas act as a climatic barrier. This mountain wall protects India from the cold winds of Central Asia in winter. The Himalayas check the on-shore S.W. Monsoons and force them to give rainfall.

(iv) The Indian Ocean: India lies at the head of the Indian Ocean. S. W. Monsoon originates from this ocean in summer and provides rainfall over most of the country. Cyclones also originate over this ocean.

(v) The Western Disturbances: The western disturbances (cyclones) originate from the Mediterranean Sea and enter India in winter. These provide rainfall in N.W. parts of India in winter.

(vi) Distance from the sea: The coastal areas experience maritime climate. These areas have equable climate. But the areas in the interior experience extreme or continental type of climate such as northwest part of India.

(vii) Relief of the land: Relief influences the distribution of temperature and rainfall in India. Mountainous areas have low temperature. The windward slopes such as Western Ghats receive heavy rainfall while the leeward slopes (Deccan Plateau) lie in the rain-shadow, and are dry.

Q.8. Describe the main characteristics of rainfall in India.

Ans. Characteristics of rainfall in India: The average annual rainfall in India is about 125 cm. It is estimated that more than 85% of this rainfall is received in summer. The main characteristics of summer rainfall are as follows:

1. Monsoonal Rainfall: Most of the rain is received from S.W. summer monsoon during the period mid-June to mid-September. It is a seasonal rainfall.

2. Uncertain Rainfall: Summer rainfall is quite uncertain. Sometimes monsoons start early resulting in floods. Often the on-set of monsoons is delayed resulting in drought. The early or late retreat of monsoons also results is serious drought.

3. Unequal Distribution: The rainfall is unevenly distributed over the country. About 10% of the country gets more than 200 cm of rain while 25% of the country gets less than 75 cm of rain and rest of the country gets 100 to 200 cm of rainfall.

4. Heavy Rainfall: Indian rainfall is heavy and downpouring type. It is often said, “It pours, it never rains in India.”

5. Relief Rainfall: The amount of rainfall is determined by the presence of mountains. High mountains force monsoons to rise and give rain.

6. No continuity of rainfall: Summer rain is characterized by breaks or dry spells.

7. Variable Rainfall: Most of the areas have variable rainfall, as much as 30 cm plus or minus. Due to variability in areas of low rain, famines occur.

Q.9. Draw rainfall and temperature graphs of Thiruvanthapuram, Delhi and jodhpur with the data given below:

Q.10. The Coromandel coast has more rainy months but less rainfall than the Konkan coast. Why?

Ans. Konkan coast faces on-shore S.W. Monsoon during summer. These moisture laden winds give heavy rainfall (more than 300 cm). But these winds do not give much rainfall on the Coromandel Coast as it lies in the rain shadow of Western Ghats. Coromandel 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 Coromandel Coast gets rainfall in both the seasons, but the total amount is less than that of Konkan Coast. Total rainfall at Chennai is 128 cm, but it is 180 cm at Mumbai.

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.

Q.11. How many distinct season are found in India as per the Indian Meteorogical Department ? Discuss the weather conditions associated with any one season in detail.

Ans. The meteorological department. has recognised the following seasons:

1. The cold weather season.

2. The hot weather season.

3. The southwest monsoon season.

4. The retreating monsoon season.

The Cold Weather Season: It starts in by mid-November in Northern India. December and January are the coldest months. The mean daily temperature remains below 21°C over most part of the country. The night temperature may be quite low. 

The peninsular region of India does not have any well defined cold weather season. There is hardly any seasonal change in the distribution pattern of the temperature in coastal areas because of the coastal influence of the sea and the nearness of equator.

Winds start blowing from North-East to South-West due to low pressure.

Rainfall occurs in northwestern India due to western disturbances. Central parts of India and northern parts of southern peninsula also get winter rainfall occa