Multiple Choice Questions (MCQ's)
Question.1. Which of the following terms refers to the sum total of weather conditions and variations over a large area for a long period of time (more than thirty years)?
(b) Annual range of temperature
Ans. (c) Climate
Question.2. Which of the following is not an elements of weather and climate?
(a) Atmospheric pressure
Ans. (d) Altitude
Question.3. Which of the following statements defines weather?
(a) Envelope of air surrounding earth
(b) State of the atmosphere over an area at any point of time
(c) Atmospheric conditions over a large area for a long period of time
(d) Generalised monthly atmospheric conditions.
Ans. (b) State of the atmosphere over an area at any point of time
Question.4. In which of the following places of India precipitation is in form of snowfall?
Ans. (b) Drass
Question.5. Which of the following places of India experiences the highest summer temperature?
Ans. (d) Jaisalmer
Question.6. Which of the following is the rainiest station?
Ans. (a) Shillong
Question.7. Which one of the following is the driest station?
Ans. (b) Leh
Question.8. Most parts of India receive rainfall during which of the following months?
(a) December to February
(b) March to May
(c) June to September
(d) October to November
Ans. (c) June to September
Question.9. In which of the following months does the Tamil Nadu coast get most of its rainfall?
(a) December to February
(b) March to May
(c) June to September
(d) October to November
Ans. (d) October to November
Question.10. Which of the following places in India experiences a very high diurnal range of temperature?
Ans. (b) Jodhpur
Question.11. In which of the following places of India there is very little difference between day and night temperatures?
Ans. (c) Thiruvananthapuram
Question.12. In which of the following places are houses built on stilts?
Ans. (a) Assam
Question.13. Which one of the following is not one of the six major controls of the climate of any place?
(c) Pressure and wind system
(d) Distance from the sea
Ans. (b) Temperature
Question.14. Latitude and altitude of a place determine which of the following climatic elements of a place?
(a) Pressure and wind system
(c) Rainfall pattern
(d) All the above
Ans. (d) All the above
Question.15. Which of the following places have cooler climate even during summers?
Ans. (c) Mussoorie
Question.16. Which of the following places of India experiences extreme type of climate?
Ans. (d) Delhi
Question.17. Due to which of the following factors does Pune receive much lesser rainfall as compared to Mumbai?
(a) It is located on the leeward side of Western Ghats
(b) It is located on windward side of Western Ghats
(d) Distance from the sea
Ans. (a) It is located on the leeward side of Western Ghats
Question.18. Which of the following latitudes passes through the middle of our country, giving it the characteristics of tropical as well as subtropical climate?
(a) Tropic of Capricorn
(b) Tropic of Cancer
Ans. (b) Tropic of Cancer
Question.19. The Indian subcontinent experiences comparatively milder winters as compared to Central Asia due to which of the following factors?
(a) The Tropic of Cancer
(b) The surrounding seas
(c) The Himalayas
(d) Ocean currents
Ans. (c) The Himalayas
Question.20. Which of the following atmospheric conditions govern the climate and associated weather conditions in India?
(a) Pressure and surface winds
(b) Upper air circulation
(c) Western cyclonic disturbances and tropical cyclones
(d) All the above
Ans. (d) All the above
Question.21. Which of the following winds brings widespread rainfall over the mainland of India?
(c) Southwest monsoon winds
(d) Sea breeze
Ans. (c) Southwest monsoon winds
Question.22. Which of the following is a component of upper air circulation?
(b) Jet stream
(c) South-west monsoon
(d) Kal Baishakhi
Ans. (b) Jet stream
Question.23. From which of the following pressure belts do the north-easterly trade winds originate?
(a) Equatorial low pressure belt
(b) Subtropical high pressure belt of the Northern Hemisphere
(c) Subtropical high pressure belt of the Southern Hemisphere
(d) Temperate low pressure belt of the Northern Hemisphere
Ans. (b) Subtropical high pressure belt of the Northern Hemisphere
Question.24. Due to which of the following reasons are the southwest monsoons rainbearing winds?
(a) They blow from low pressure area of northeastern India towards the seas
(b) They are seasonal winds
(c) They blow over warm Indian Ocean and gather moisture
(d) They strike the Himalayas
Ans. (c) They blow over warm Indian Ocean and gather moisture
Question.25. Which of the following prevents the southwest monsoon winds from escaping from India?
(a) The surrounding seas
(b) The Himalayas
(c) Low pressure over Central Asia
(d) The Indian deserts
Ans. (b) The Himalayas
Question.26. The word monsoon is derived from a word which literally means which of the following?
(b) Wind pattern
Ans. (a) Seasons
Question.27. In which of the following stations of India’s mainland does the monsoons arrive first?
Ans. (a) Thiruvananthapuram
Question.28. By which of the following dates do southern parts of our islands receive their first monsoon showers?
(a) First week of April
(b) First week of May
(c) First week of June
Ans. (a) First week of April
Question.29. Which of the following stations of India experiences snowfall in winter?
Ans. (d) Srinagar
Question.30. Which of the following causes rainfall in West Bengal during the hot weather season?
(a) Mango showers
(b) Kal Baishakhi
(c) Southwest monsoon
(d) Retreating Monsoon
Ans. (b) Kal Baishakhi
Question.31. In which month the transition season changes the hot rainy season to dry winter season?
(a) December to February
(b) February to March
(c) June to July
(d) October to November
Ans. (d) October to November
Question.32. The term monsoon is originated from?
Ans. (d) Arabic
Question.33. Kal Baisakhi is associated with
Ans. (d) Bengal
Question.34. The peninsular part of India experiences peak summers earlier than northern India because :
(a) There is less rainfall in the peninsula during that time.
(b) Cold waves from Central Asia sweeps through the northern plains during the time.
(c) Due to northward movement of the sun, the global heat belt shifts northward
(d) Clouds do not form in those months
Ans. (c) Due to northward movement of the sun, the global heat belt shifts northward
Question.35. Bengal, Orissa and Andhra Pradesh coasts are frequented by cyclones because
(a) The level coastline makes the cyclones penetrate these areas earlier
(b) These areas are close to a volcano
(c) Low pressure conditions in northwest India lead to the creation of depression over Andaman sea.
(d) Heavy rainfall in these parts encourage strong wind conditions
Ans. (c) Low pressure conditions in northwest India lead to the creation of depression over Andaman sea.
Question.36. Mango showers occur in which one of the following group of two states?
(a) Bihar and West Bengal
(b) Tamil Nadu and Andhra Pradesh
(c) Karnataka and Kerala
(d) Maharashtra and Andhra Pradesh
Ans. (c) Karnataka and Kerala
Question.37. Which is the coldest place in India?
Ans. (a) Drass
Question.38. Which area is not an area of low precipitation?
(a) Western Rajasthan and Gujarat
(b) Leh in Jammu and Kashmir
(c) Deccan plateau
Ans. (d) Assam
Question.39. In winter the western cyclonic disturbances originate from which sea?
(a) Mediterranean Sea
(b) Indian Ocean
(c) Caspian Sea
(d) Arabian Sea
Ans. (a) Mediterranean Sea
Question.40. Which one of the following states suffers from loo?
(a) Tamil Nadu
(b) Uttar Pradesh
(d) None of these
Ans. (c) Gujarat
Question.41. Where does the ‘loo’ flow in summer?
(a) Peninsular India
(b) North and Northwestern India
(c) Coastal regions
(d) Eastern India
Ans. (b) North and Northwestern India
Question.42. Which one of the following terms is used for the state of atmosphere over an area at any point of time ?
Ans. (a) Weather
Short Answer Type Questions
Question.1. What are jetstreams? How do they affect the climate?
- Jetstreams are a narrow belt of high speed, high altitude, westerly winds in the troposphere. Jetstreams are an important component of the upper air circulation. They are located at an altitude of above 12000 metres. Their speed varies from 110 km/hr in summer to about 184 km/hr in winter. The most constant jetstreams identified are the mid-latitude and the subtropical jetstreams. Over India, jetstreams blow south of the Himalayas, all through the year except summer.
- The western cyclonic disturbances are experienced in the north and northwestern parts of the country during winter months. They are brought in by the flow of westerly jetstream from the Mediterranean region.
- In summer when the subtropical westerly jetstream moves north of the Himalayas, an easterly jetstream, called the tropical easterly jetstream blows over Peninsular India, approximately over 14°N latitude. Tropical cyclones that occur during the monsoons as well as in October November are influenced by the tropical easterly jetstreams. The easterly flow brings tropical cyclones from the Bay of Bengal to the coastal regions of Orissa and Andhra Pradesh.
Question.2. What is the loo? How does it affect the weather of a place?
Ans. The strong, gusty, hot, dry winds blowing during the day over the north and northwestern India during summer are known as ‘loo’. The ‘loo’ is a striking feature of the hot weather season from April to June. Loo usually occurs during the afternoon but sometimes it even continues until late in the evening.
Direct exposure to these winds may even prove to be fatal. They cause acute dehydration and sunstroke. During May and June they sometimes bring duststorms which bring temporary relief as they lower the temperatures and may bring light rain and cool breeze.
Question.3. Write a short note on the retreating monsoons.
- The months of October-November mark a period of transition from hot rainy season to cold dry winter conditions. This period is known as Retreating Monsoon or Transition season because the southwest monsoons weaken and withdraw or retreat from India.
- The retreat of monsoon is marked by clear skies and rise in temperature. While days are warm, nights are cool and pleasant. Owing to high temperature and high humidity, weather becomes oppressive. This phenomenon is known as ‘October heat’.
- With the shift of low pressure centre to the Bay of Bengal in early November, cyclonic depressions originating over the Andaman Sea move over the Eastern Coast. The Coromandel coast receives bulk of its rainfall from the retreating monsoons.
- These tropical cyclones cause heavy destruction and torrential rains in thickly populated deltaic regions of Tamil Nadu and Andhra Pradesh.
Question.4. Describe with examples how altitude affects the climate of a place.
- Altitude plays an important role in influencing the climate of a place. As one goes up to higher altitudes away from the surface of the earth, the atmosphere becomes less dense and temperature decreases. As a result hill stations like Mussoorie, Darjeeling and Udagamandalam (Ooty) in the south are cooler even during summer.
- The decrease in temperature with altitude also has its effects upon the pressure system which in turn determines the wind pattern and hence precipitation.
- Drass, Srinagar and Shimla, located on the higher slopes of the Himalayas, receive heavy snowfall during winter due to inflow of western disturbances to areas with sub-zero temperatures.
- The lofty Himalayas, on account of their high altitude, stand as a barrier and protect India from bitterly cold winds of Central Asia during winter. They also confine the rainfall from the monsoons to the mainland of India.
- Places at lower altitudes, mainly those along the coast like Mumbai, Chennai, Kolkata, have moderate climates.
Question.5. Describe with examples how distance from the sea influences the climate of a place?
Ans. The sea exerts a moderating influence on the climate of a place. Places like Mumbai, Chennai, Thiruvanthapuram, Kolkata located near the sea have equable climate or maritime climate with less difference between summer and winter temperatures. As the distance from the sea increases, its moderating influence decreases. Places away from the sea are said to have continental location. Continentality is marked by extreme weather conditions, i.e., very hot summer and very cold winter. For example, Delhi located in the interior of the country at a distance from the sea experiences an extreme type of climate.
Question.6. What form of precipitation does the upper part of the Himalayas receive and why?
Ans. The upper parts of the Himalayas have quite high altitude of around 6000 metres. Temperature is very low in these parts as temperature decreases with a rise in altitude. Precipitation takes place in the form of snowfall in all stations in the upper parts of the Himalayas due to freezing temperatures. For example, Drass located in Jammu and Kashmir records minus 45°C (–45°C) temperature on a winter night. Hence, precipitation in this region is in the form of snowfall. Srinagar in the valley of Kashmir, Shimla and Manali in Himachal Pradesh and other hill stations in the upper parts of Himalayas receive snowfall in winter due to inflow of western cyclonic disturbances from the west.
Question.7. Write a short note on the trade winds. What are the effects of trade winds on the climate of India?
- The planetary winds blowing from the Sub-Tropical High Pressure Belts to the Equatorial Low Pressure Belt or Doldrums are termed as ‘Trade Winds’.
- On account of the Laws of Deflection due to the Coriolis force, they blow as North-East Trade Winds in the Northern Hemisphere and as South-East Trade Winds in the Southern Hemisphere. The trade winds are the most permanent and regular of all planetary winds. They blow with great force in a constant direction.
- India lies in the region of Northeasterly Trade Winds. As they originate and blow over land, the Northeasterly Trade Winds generally carry very little moisture. Therefore, they bring little or no rainfall. Hence, had trade winds been the only factor influencing India’s climate, India would have been an arid land.
- In late summer low pressure condition over Northern Plains intensifies. This attracts the trade winds of the Southern Hemisphere. The Southeast Trade Winds originating over warm subtropical areas of southern oceans cross the equator and blow in a southwesterly direction to India. They are moisture laden and bring rainfall to India as southwest monsoon.
Question.8. Discuss why Mawsynram receives the highest rainfall in the world?
Ans. Mawsynram in Meghalaya is located on the southern ranges of the Khasi Hills. When the rain bearing winds from the Bay of Bengal branch of monsoons strike the Garo, Khasi and Jaintia hills, they cause very heavy rainfall in the northeastern states located here. As Mawsynram is located at a position perpendicular to the path of the rainbearing winds which enters the deep valley of the Khasi hills, it receives rainfall of about 1141 cm per year. Hence, Mawsynram receives the highest rainfall in the world. Rainfall occurs here for almost nine months of the year.
Question.9. What is the Coriolis force? Describe briefly its effect on the climate of the world.
- An apparent force caused by the earth’s rotation is called the Coriolis force. The Coriolis force is responsible for deflecting the direction of the winds towards the right in the Northern Hemisphere and towards the left in the Southern Hemisphere. This is also known as ‘Ferrel’s Law’.
- Under the effect of Coriolis force the trade winds moving from Sub-Tropical High Pressure belts to Equatorial Low Pressure belts become Northeast Trade Winds in the Northern Hemisphere and Southeast Trade Winds in Southern Hemisphere. As a result, they bring heavy rainfall to the east coast of continents within tropics after passing over oceans. As they are offshore on the west coast, these regions turn into hot deserts.
- Westerly winds blowing from Sub-Tropical High to Temperate Low Pressure belts become the South-Westerlies in the Northern Hemisphere and the North westerlies in the Southern Hemispheres due to Coriolis force. They bring much precipitation to western coast of continents, mainly in Southern Hemisphere.
Question.10. Give reasons why the bulk of the rainfall is concentrated over a few months in India.
Ans. The major part of the annual precipitation of India is due to the southwest monsoons. The reasons behind concentration of rainfall over few months are as follows :
(a) By early June the low pressure zone over northern India intensifies and attracts the moisture laden Southwest monsoons. These onshore winds are the main source of rainfall in India. As they originate as southeast trade winds over warm subtropical southern oceans they bring abundant moisture.
(b) The advancing southwest monsoons strike the southern part of the peninsula in early June and by July, it has its sway over entire India. The duration of monsoon is between 100-120 days from early June to mid-September. Bulk of the rainfall of India is concentrated within these months. This period is known as rainy season.
(c) The Arabian Sea branch and Bay of Bengal branch of monsoon bring heavy rainfall of over 400 cm in West Coast areas and northeastern states. Even dry areas like Rajasthan and Gujarat receive some rain.
Question.11. Why do western Ghats receive more rainfall than the Eastern Ghats. Explain briefly.
Ans. In terms of relief the western Ghats are much higher (900 – 1600 meter) in comparison to the Eastern Ghats (600 meter). The Western Ghats are continuous stretches of high mountains. Therefore, when the moisture ladden Arabian Sea branch of Southwest Monsoon first strikes the Western Ghats it brings heavy rainfall along the windward side of the Western Ghats. In Eastern Ghats, rain bearing winds of Southwest Monsoon do not face such orographic barrier and hence receive much lower amount of rainfall.
Question.12. What are western disturbances? How do they effect the climate of India?
Ans. The western cyclonic disturbances are weather phenomena of the winter months brought in by the westerly flow from the Mediterranean region. This phenomena usually influence the weather conditions of North and Northwestern regions of India. Tropical cyclones occur during October-November as a consequence of this western disturbances.
A characteristic feature of the cold weather season over the northern plains is the inflow of cyclonic disturbances from the west and the Northwest. These low pressure systems originate over the Mediterranean Sea and Western Asia and move into India along with the westerly flow. Under its influence cause the much needed rainfall over the plains and snowfalls in the mountains. The total amount of winter rainfall, locally known as Mahawat, is small but they are of immense value for the cultivation of rabi crops.
Question.13. Explain how monsoon acts as a unifying bond in the country. OR
Why are the monsoons considered as a unifying bond? Explain. OR
How do monsoon acts as a unifying bond for India? Explain.
Ans. The unifying influence of the monsoon on the Indian subcontinent is felt through its seasonal alternation of the wind systems and the associated weather conditions. It is also perceptible through uncertainties and uneven distribution of monsoon rainfall. The Indian landscape, its flora and fauna, agricultural seasons, livelihood of the people including festivals etc. are governed by the monsoon. Year after year people anxiously wait for the arrival of monsoon. The river valleys which carry monsoon water also unite the country as a single river valley unit.
Question.24. Define monsoon. Differentiate between ‘Burst of the Monsoon’ and ‘Break of the Monsoon.
Ans. The word ‘monsoon’ is derived from the Arabic word ‘mausim’ which means season. It is basically a seasonal rain bearing winds, lasting for 100 – 120 days from early June to mid September. At the time of its arrival, the normal rainfall increases suddenly and continues constantly for several days. This is known as ‘burst of the monsoon’. The phenomenon can be distinguished from the pre-monsoon showers.
Another phenomenon associated with the monsoon is its tendency to have breaks in rainfall. The monsoon rains take place only for a few days at a time. They are interspersed with rainless intervals. These breaks in monsoon are related to the movement of the monsoon trough.
Long Answer Type Questions
Question.1. Write a brief note on the south-west monsoon and its influence on the climate of India.
- The word ‘monsoon’ is derived from the Arabic word ‘mausim’ which means season. It is marked by complete reversal of wind system according to seasons. The summer period is marked by the south-west monsons.
- The low pressure centre over northern India intensifies by early June. It attracts the southeasterly trade winds from the Southern Hemisphere which become south-westerly winds after crossing the equator due to the coriolis effect. As they originate over warm sub-tropical areas of Southern Oceans they bring abundant moisture to India’s mainland as southwest monsoon. The southwest monsoon strikes the southern parts of the peninsula in early June and by mid-July has its sway over entire India. The duration of the monsoon is between 100-120 days from early June to mid-September. This period is known as the Rainy Season. The two branches of southwest monsoons – the Arabian Sea branch and the Bay of Bengal branch–advance through the country and merge over the Northern Plains.
- They provide heavy torrential rainfall in the West Coast and Northeastern states. Even Rajasthan receives some amount of rain. The bulk of the rainfall in India (75% to 90%) is caused by the advancing southwest monsoons and is concentrated within the Rainy Season. India has hot, wet tropical monsoon climate on account of it. The south-west monsoon is pulsating in nature marked by wet spells followed by dry spells termed as ‘breaks’. The south-west monsoons are uncertain and variable in nature. They may cause floods in some parts and droughts in other parts. The entire climatic regime of India is dependent upon the south-west monsoons.
Question.2. Why does the rainfall decrease from east to west in Northern India? Write a brief note explaining why.
- The bulk of rainfall in India comes from the southwest monsoons. The Arabian Sea branch of south-west monsoon approaches from the western side of the peninsula and moves in a southwesterly direction and reaches the Northern Plains by first week of July.
- The Bay of Bengal branch of southwest monsoon brings heavy rainfall to the northeastern states. It arrives in Assam in the first week of June. The lofty mountains of the Purvanchals causes the monsoon winds to deflect towards the west over the Ganga Plains.
- They cause heavy rainfall on the eastern parts of the Northern Plains as the moisture content of the onshore winds are high. As the winds move westwards their moisture content decreases and bence, the rainfall decreases.
- The Arabian Sea branch of monsoons approach the Northern Plains from the west. But the highlands, the Aravalis, in the western part of the country, lie parallel to the direction of the onshore winds. Hence, very less or no rainfall is experienced in the western limits of the plains.
- They provide more rainfall on the central and eastern parts of the plains when the rain bearing winds strike the Himalayas.
- Both the branches merge over the northwestern part of the Ganga Plains. Delhi receives its showers from either of the branches. The location of the monsoon trough over the Northern Plains also determines the amount of rainfall. When the axis of the trough lies over the plains, rainfall is good in these parts, especially in the eastern parts where tropical depressions from Bay of Bengal approach. When the monsoon trough moves northwards towards Himalayas, there are dry spells over the Northern Plains and heavy rainfall occurs in the Himalayas.
- Hence, due to the above reasons, rainfall decreases from east to west in Northern India.
Question.3. Distinguish between southwest monsoon and northeast monsoon.
Ans. The monsoon type of climate is marked by complete reversal of wind system according to seasons. The summer period is marked by the southwest monsoons while the winter period is marked by northeast monsoons. The points of difference between them are as follows :
(a) The southwest monsoons blow in a southwesterly direction to the mainland of India from June to September. While, the northwest monsoons blow in a northeasterly direction across India from mid-November to February.
(b) The southwest monsoons are seasonal winds influenced by differential heating of land and water. The southeasterly trade winds are attracted by low pressure over northern India. They are deflected to southwest after crossing the equator due to the Coriolis force while the northeast monsoons are the northeasterly trade winds.
(c) The southwest monsoons are onshore winds as they blow from the Indian Ocean as Arabian Sea and Bay of Bengal branches to land areas. Hence, they are moisture laden winds and bring heavy rainfall. While the northeast monsoons are offshore winds as they blow from land to sea. As a result they are mostly devoid of moisture.
(d) The southwest monsoons are responsible for the bulk of the rainfall in India (75% to 90%). They make Mawsynram in Meghalaya the rainiest station in the world. During the northeast monsoons some rainfall is brought by occassional western disturbances in north India. The northeast monsoons provide some rainfall in eastern coastal plain of Tamil Nadu after passing over Bay of Bengal.
(e) The southwest monsoons are warm winds. While the northeast monsoons are cold winds.
Question.4. Explain the major factors influencing climate in India.
Ans. The important factors that influence the climate of India can be identified as follows :
(a) Latitudinal Location. India lies in the Northern Hemisphere with the Tropic of Cancer (23°30′N) passing almost through the middle of India. Areas to its south have tropical type of climate, while areas to its north have characteristics of sub-tropical climate.
(b) Altitude and Relief Features. The mountainous areas to the north of the Himalayas have average altitude of upto 6000 metres. Stations located here are cool even in summer and receive snowfall during winter. The lofty Himalayas along the northern borders of India act as a mighty barrier protecting India from the cold winds from Central Asia in winter. As a result India experiences milder winters as compared to Central Asia. It also concentrates the monsoon rains within the mainland of India. The compact physical setting of India with the mountains in the north and Indian Ocean to the south of the peninsula, lends a broad common climatic framework to India.
(c) Pressure and Winds. The pressure and wind conditions over India are unique. They result in seasonal reversal of the wind system and monsoon winds dominate the climate of India. The bulk of the rainfall in the country is brought by the southwest monsoons. Upper air circulation and the position of jet streams in upper troposphere influence the monsoons. Western cyclonic disturbances in winter and tropical cyclones during retreating monsoon season bring rainfall and affect the climate.
(d) Distance from the sea. Places at coastal locations, e.g. Mumbai, Chennai, Kolkata, have maritime or equable climate due to the moderating influence of the sea. But places in the interior of the country, far from the sea, experience extreme climate due to continentality, e.g. Dehli.
Question.5. Write briefly about the Arabian Sea branch of the monsoon.
- The Indian Peninsula divides the southwest advancing monsoons into two branches – the Arabian Sea branch and the Bay of Bengal branch. The Arabian Sea branch of monsoons approaches the western coast of India from the Arabian Sea in a southwesterly direction. It arrives at Thiruvananthapuram on the 1st of June. By 10th of June it reaches Mumbai. The onshore moisture laden winds strike the Western Ghats and provide heavy rainfall on its windward side. As a result Mumbai in the windward side receives much more rainfall than Pune which is located on the leeward side of the Western Ghats.
- The Deccan Plateau lies in the rain shadow area and hence receives less rainfall.
- By mid-June the Arabian Sea branch of the monsoon arrives over Saurashtra-Kuchchh and the central part of the country.
- In the western and northwestern parts of the country, the highlands, the Aravalis, lie parallel to the direction of the incoming Arabian Sea branch of monsoons. Hence, these areas do not receive much rainfall because the rain bearing winds do not strike any barrier.
- By the first week of July, western Uttar Pradesh, Punjab, Haryana and eastern Rajasthan experience the monsoons.
- The Arabian Sea branch of monsoons merges with the Bay of Bengal branch over the northwestern part of the Ganga plains. Delhi receives its rain from either of the two branches.
Question.6. Write in brief about the mechanism of the monsoons. OR
What is meant by the term ‘monsoon’? Give the main characteristics of monsoons.
Ans. The mechanism of monsoons can be explained by the following facts :
(a) The differential heating and cooling of land and water creates low pressure on the landmass in summer which attracts moisture-bearing winds from the high pressure centres over the sea.
(b) The shift of the position of Inter – Tropical Convergence Zone (ITCZ) in summer, over the Ganga plain from the equatorial region, creates a monsoon trough that attracts winds. The shifting of the axis of the trough effects the duration and intensity of monsoons.
(c) The movement of the westerly jetstream to the north of the Himalayas and the presence of the tropical easterly jetstream over Indian Peninsula during summer bring in the tropical depressions and cyclones associated with monsoons.
(d) The intensity and position of the high pressure area east of Madagascar, approximately at 20°S over the Indian Oceans, affects Indian monsoon.
(e) The Tibetan plateau gets intensely heated during summer, which results in strong vertical air currents. High pressure is formed over the plateau at about 9 km above sea level. Periodic change in pressure conditions over southern oceans, known as Southern Oscillation and effect of El Nino also influences the monsoons.
Question.7. Write a brief account of the conditions and characteristics of the retreating monsoons.
- The months of October-November mark a period of transition from hot rainy season to cold dry winter conditions. With the apparent movement of the sun southwards, the low pressure monsoon trough over the Northern Plains weakens and is gradually replaced by a high pressure system. The low pressure conditions shift to the Bay of Bengal.
- As a result, the southwest monsoon winds weaken and start withdrawing gradually from India.
- By the beginning of October it withdraws from the Northern Plains. This period is known as the Retreating Monsoon or Transition season because the monsoons withdraw or retreat from India. The Retreating Monsoon season is marked by clear skies and rise in temperature. While days are warm, nights are cool and pleasant. High rate of evaporation from the land that is still moist results in high humidity and oppressive weather conditions during the day. This phenomenon is known as ‘October heat’.
- With the shift of low pressure zone to over the Bay of Bengal in early November, cyclonic depressions originating over the Andaman Sea moves over the Eastern Coast. The tropical cyclones and associated heavy rainfall cause heavy destruction in the thickly populated deltaic areas of Tamil Nadu and Andhra Pradesh and sometimes Orissa, West Bengal and Bangladesh.
- The bulk of the rainfall of the Coromandel coast is derived from these cyclones and depressions. The retreat or withdrawl of monsoon is a gradual process and takes a long time.
Question.8. Describe how the Himalayas affect the climate of India.
- The lofty Himalayas stand as a mighty barrier along the entire northern boundary of India.
- They have a profound influence on India’s climate. The high mountains with an elevation of 6000 metres act as an effective climatic divide. In winter they prevent the cold winds from Central Asia from entering India. As a result, India experiences comparatively milder winters as compared to Central Asia.
- The mountain wall blocks the monsoon winds, preventing their escape out of India. It concentrates rainfall from the monsoon winds within India.
- When the moisture laden monsoon winds strike the Himalayas, heavy rainfall is caused in the foothills region. The Northern Plains of India receive rainfall from the Bay of Bengal branch of monsoons because the eastern mountains deflect these winds over the Ganga Plains.
- The Himalayas are responsible for giving the subtopical areas in northern India a touch of the tropical climate with hot, wet summer and mildly cold, dry winters. The alignment of the Himalayas also influences climate, So Ladakh on the leeward side of the Himalayas is a cold desert while Mawsynram on the southern ranges of Purvanchal receives the highest rainfall in the world.
Question.9. Give an account of the weather condition and characteristics of the cold season.
Ans. The period between mid-November to February is the cold weather season in India. December and January are the coldest months in the northern part of India. The cold weather season is characterised by the following features :
(a) A high pressure region develops in the northern part of the country with the apparent movement of the sun southwards.
(b) The northeast trade winds prevail over the country. As they blow from land to sea, for most parts of the country it is a dry season.
(c) Light winds move outwards from the high pressure area. Under the influence of relief, these winds blow from the west and northwest in the Ganga Valley.
(d) Days are warm and nights are cool during the season. Weather is marked by clear sky, low temperature and low humidity and feeble variable winds mainly in the north.
(e) Temperature is lower in the northern parts, ranging between 10° to 15°C. Temperature is higher in southern India, between 24° to 25°C, as in Chennai.
(f) Frost is common in northern parts.
(g) The higher slopes of the Himalayas, e.g. places like Srinagar, Leh and Shimla, experience snowfall.
(h) The western cyclonic disturbances are characteristic weather phenomena of the winter months. Their inflow from the west and northwest is brought in by the westerly flow from the Mediterranean Sea region. They cause the much needed winter rains over the plains and snowfall in the mountains in the northwestern India.
(i) The peninsular region does not have a well-defined cold season due to moderating influence of the sea. Rainfall occurs on Tamil Nadu coast during winter because the northeast winds blow from sea to land here.
Question.10. Give a brief account of the hot weather season in India.
Ans. The period between April to June is the hot weather season or summer in India. The characteristic features of the hot weather season are as follows :
(a) The global heat belt shifts northward due to the apparent northward movement of the sun.
(b) The temperature recordings taken during April to June of stations at different latitudes, show the influence of the shifting of the heat belts. In March temperature in Deccan is about 38°C. In April, temperatures in Madhya Pradesh and Gujarat are around 42°C. In May, temperature of 45°C is common in northwestern India. Peninsular India has moderate temperature due to influence of sea.
(c) The rising temperatures lead to fall in air pressure in the northern parts. Toward the end of May, an elongated low pressure area develops in the north extending from the Thar desert in the northwest to Patna and Chhota Nagpur platean in the east.
(d) Strong, gusty, hot, dry winds, locally called ‘loo’ blow during the afternoon over north and northwestern India. They may continue till late evening.
(e) Duststorms are common during May in Punjab, Haryana, Delhi, Eastern Rajasthan and Western Uttar Pradesh. Sometimes they bring light rain and pleasant cool breeze that provide temporary relief from the heat.
(f) High temperature during the day causes violent, localised thunderstorms by the evening. These thunderstroms are associated with violent winds and torrential downpour, often accompanied with rain. They are known as ‘Kal Baisakhi’ or calamity of the month of Baisakh in West Bengal.
(g) In late May pre-monsoon showers occur, especially in Karnataka and Kerala. They are known as mango showers as they help in the early ripening of mangoes.
Question.1. On the outline map of India, mark and label the areas that receives seasonal rainfall from June to September.
(a) Less than 20 cm
(b) 40-60 cm
(c) 100-200 cm
(d) Above 400 cm
Question.2. On an outline map of India, mark and label the following:
(a) Direction of the south-west monsoons with arrows
(b) The places that receive annual rainfall above 200 cm
(c) The places that receive annual rainfall below 40 cm
(d) The places that receive annual rainfall of 60-100 cm
Question.3. On the outline map of India below, mark and label the following:
(a) Places that receive snowfall in winter
(b) The north-east monsoon with arrows
(c) The place that receives the highest rainfall in the world
(d) The coast of South India that receives high rainfall in winter