NCERT Solutions Class 9th Social Science (Geography) Chapter – 4 Climate
| Textbook | NCERT |
| Class | 9th |
| Subject | Social Science (Geography) |
| Chapter | 4th |
| Chapter Name | Climate |
| Category | Class 9th Social Science (Geography) |
| Medium | English |
| Source | Last Doubt |
NCERT Solutions Class 9th Social Science (Geography) Chapter – 4 Climate
Chapter – 4
Climate
Question Answer
| Question 1. Choose the correct answer from the four alternatives given below. (i) Which one of the following places receives the highest rainfall in the world? (a) Silchar (b) Mawsynram (c) Cherrapunji (d) Guwahati Answer – (b) Mawsynram (ii) The wind blowing in the northern plains in summers is known as: (a) Kaal Baisakhi (b) Loo (c) TVade Winds (d) None of the above Answer – (b) Loo (iii) Which one of the following causes rainfall during winters in north-western part of India, (a) Cyclonic depression (b) Retreating monsoon (c) Western disturbances (d) Southwest monsoon Answer – (c) Western disturbances (iv) Monsoon arrives in India approximately in: (a) Early May (b) Early July (c) Early June (d) Early August Answer – (c) Early June (v) Which one of the following characterises the cold weather season in India? (a) Warm days and warm nights (b) Warm days and cold nights (c) Cool days and cold nights (d) Cold days and warm nights Answer – (c) Cool days and cold nights |
| Question 2. Answer the following questions briefly. (i) What are the factors affecting the climate of India? Answer – The factors controlling the climate of India are: • Latitude • Altitude • Pressure and winds (jet streams) • Distance from the sea • Relief or mountains (ii) Why does India have a monsoon type of climate? Answer – India has a monsoon type of climate because of the strong influence of the monsoon winds over the sub-continent. The summer monsoons cause heavy rainfall when they blow from sea to land. The winter monsoon winds blow from the interior of the continent to the sea and do not cause much rain. There is a seasonal reversal of the wind system ‘monsoon’. (iii) Which part of India does experience the highest diurnal range of temperature and why? Answer – The Thar desert experiences the highest diurnal range of temperature. This is because during the day the temperature rises to over 50°C, and at night due to the absence of the sun and lack vegetation the temperature drops to below 15°C the same night. (iv) Which winds account for rainfall along the Malabar Coast? Answer – Arabian Sea Branch of the South West summer Monsoons. (v) What are jet streams and how do they affect the climate of India? Answer – Jet streams are a narrow belt of high altitude (above 12,000 m) westerly winds in the troposphere. Their speed varies from about 110 km/h in summer to about 184 km/h in winter. A number of jet streams exist but the most constant are the mid-latitude and the sub-tropical jet stream. The jet streams located over 27°-30° north latitudes are known as subtropical westerly jet streams. These jet streams blow south of the Himalayas throughout the year except in summer. These are responsible for the western cyclonic disturbances experienced in the north and north western parts of the country. These jet streams move north of the Himalayas with the apparent migration of the sun.During the summers at about 14°N, an easterly jet stream called the subtropical easterly jet stream blows over peninsular India. (vi) Define monsoons. What do you understand by “break” in monsoon? Answer – The word monsoon has been derived from the Arabic word ‘mausim’ which means season. In this season the winds blow from land to sea for 6 months and from sea to land for 6 months. The break in the monsoon rainfall refers to the dry spells when the monsoon rain takes place only for a few days at a time. These breaks are related to the movement of the monsoon trough. When the axis of the monsoon trough lies over the plains, then the rainfall is heavier there. When the trough moves towards the Himalayas, the plains are dry but there is heavy rainfall occur over the mountains. (vii) Why is the monsoon considered a unifying bond? Answer – The subcontinent of India has a great variation in temperature conditions, despite the moderating influence created by other factors. The monsoons have a unifying influence as the rainfall that is caused affects the entire country. Water is thus supplied for agricultural activities as well as to the rivers for use all over the country. The monsoons thus bind the entire continent, where all wait eagerly for their arrival. |
| Question 3. Why does the rainfall decrease from the east to the west in Northern India? Answer – The low-pressure area in India lies in the northwest, towards which the South West Monsoon winds are attracted. After depositing moisture in south India, the Bay of Bengal branch of the South West Monsoons strikes the Khasi – Garo Hills. After causing heavy rainfall on the windward slopes, these winds turn westwards because of the presence of the lofty Himalayas. These winds then keep depositing rainfall they go up the Ganga valley towards the low-pressure area. The rainfall deposited thus keeps on decreasing as the winds proceed from east to west in Northern India, as this is the last region to be affected by the monsoons. |
| Question 4. Give reasons as to why. (i) Seasonal reversal of wind direction takes place over the Indian subcontinent? Answer – Land and water are of different densities, so the rate of heating and cooling varies. The Indian subcontinent is surrounded by water on three sides. In summer the land mass of India is warmer than the surrounding sea, therefore there is low pressure. The sea is cooler, thereby having higher pressure. So the winds blow from sea to land.In winter the land has high pressure while the sea has low pressure. Therefore, the winds blow towards the sea. Thus a seasonal reversal of wind direction takes place. (ii) The bulk of rainfall in India is concentrated over a few months. Answer – In India the bulk of the rainfall is concentrated over a few months. The main source of rainfall is the monsoon wind which blows when there is intense low pressure on the land. The surrounding waterbody is cool and has high pressure. This ideal temperature and pressure is caused in May, when the rain falls between June – September and it becomes cooler (high pressure). Rest of the year is practically dry. (iii) The Tamil Nadu coast receives winter rainfall winds. Answer – During the winter season the Tamil Nadu coast receives rain from the north east Monsoon which blow from land to sea. They do not cause any rain in the northern part of the country. But while crossing the Bay of Bengal they pick up moisture-and cause rain on the eastern coat of south India, mainly the Tamil Nadu coast. (iv) The delta region of the eastern coast is frequently struck by cyclones. Answer – The delta region of the eastern coast is frequently struck by cyclones as the low pressure conditions over north western India get transferred to the Bay the Bengal by early November. This shift is responsible for the occurrence of cyclonic depressions which originate over the Andaman sea. These then cross the eastern coast causing heavy widespread rain leading to great damage to life and property. (v) Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone. Answer – Relief/Mountains play an important role in the distribution of rainfall in India. The moisture laden winds (South West Monsoons) cause heavy rain on the windward slopes of the Western Ghats and Khasi-Garo hills. As the winds cross over to the leeward slopes, there is less rainfall as most of it has been deposited on the slope facing the winds. All the area on the leeward side is deprived of rain and is drought prone. Rajasthan also lies in the rain shadow of the Aravalli hills. |
| Question 5. Describe the regional variations in the climatic conditions of India with the help of suitable examples. Answer – Despite an overall unity in the general pattern, there are perceptible regional variations in climatic conditions within the country. The two important elements, which cause these variations, are – temperature and precipitation. • For example, in summer, the mercury occasionally touches 50°C in some parts of the Rajasthan desert, whereas it may be around 20°C in Pahalgam in Jammu and Kashmir. On a winter night, the temperature at Drass in Jammu and Kashmir may be as low as minus 45°C. Tiruvananthapuram, on the other hand, may have a temperature of 20°C. |
| Question 6. Discuss the mechanism of monsoons. Answer – To understand the mechanism of the monsoons, the following facts are important.
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| Question 7. Give an account of weather conditions and characteristics of the cold season. Answer – The weather conditions greatly change from one season to the other. These changes are particularly noticeable in the interior parts of the country. The coastal areas do not experience much variation in temperature though there is variation in rainfall patterns. The cold weather season begins from mid- November in northern India and stays till February. December and January are the coldest months in the northern part of India. • The temperature decreases from the south to the north. The average temperature of Chennai, on the eastern coast, is between 24° – 25° Celsius, while in the northern plains, it ranges between 10° – 15° Celsius. Days are warm and nights are cold. Frost is common in the north and the higher slopes of the Himalayas experience snowfall. |
| Question 8. Give the characteristics and effects of the monsoon rainfall in India. Answer – The Monsoon, unlike the trades, are not steady winds but are pulsating in nature, affected by different atmospheric conditions encountered by it, on its way over the warm tropical seas. The duration of the monsoon is between 100- 120 days from early June to mid-September. • Around the time of its arrival, the normal rainfall increases suddenly and continues constantly for several days. This is known as the ‘burst’ of the monsoon and can be distinguished from the pre-monsoon showers. • The monsoon arrives at the southern tip of the Indian peninsula generally by the first week of June. Subsequently, it divides into two – the Arabian Sea branch and the Bay of Bengal branch. The Arabian Sea branch reaches Mumbai about ten days later on approximately the 10th of June. This is a fairly rapid advance. • The Bay of Bengal branch also advances rapidly and arrives in Assam in the first week of June. The lofty mountains cause the monsoon winds to deflect towards the west over the Ganga plains. By mid-June, the Arabian Sea branch of the monsoon arrives over Saurashtra-Kuchchh and the central part of the country. • The Arabian Sea and the Bay of Bengal branches of the monsoon merge over the northwestern part of the Ganga plains. Delhi generally receives the monsoon showers from the Bay of Bengal branch by the end of June (tentative date is 29th of June). By the first week of July, western Uttar Pradesh, Punjab, Haryana and eastern Rajasthan experience the monsoon. • By mid-July, the monsoon reaches Himachal Pradesh and the rest of the country. Withdrawal or the retreat of the monsoon is a more gradual process. The withdrawal of the monsoon begins in the northwestern states of India by early September. • By mid-October, it withdraws completely from the northern half of the peninsula. The withdrawal from the southern half of the peninsula is fairly rapid. By early December, the monsoon has withdrawn from the rest of the country. • The islands receive the very first monsoon showers, progressively from south to north, from the first week of April to the first week of May. The withdrawal takes place progressively from north to south from the first week of December to the first week of January. By this time the rest of the country is already under the influence of the winter monsoon. |
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