NCERT Exercise
1. Choose the correct answer from the four options given below.
(i) Which of the following places receives the highest rainfall in the world?
(a) Silchar (c) Cherrapunji
(b) Mawsynram (d) Guwahati
Ans. (b) Mawsynram
(ii) The winds blowing in the northern plains during summer are called:
(a) Kal Baisakhi (c) Trade winds
(b) Loo (d) None of the above
Ans. (b) Loo
(iii) The onset of monsoon in India is around:
(a) Early May (c) Early June
(b) Early July (d) Early August
Ans. (c) Early June
(iv) Which one of the following is a characteristic of the cold season in India?
(a) Hot days and hot nights
(b) Hot days and cold nights
(c) Cold days and cold nights
(d) Cold days and hot nights
Ans. (b) Hot days and cold nights
2. Give brief answers to the following questions.
(i) What are the factors affecting the climate of India?
Ans. The following are the main factors affecting the climate of India:
(i) Geographical location of the country
(ii) Monsoon winds
(iii) Position of the Himalayas
(iv) Indian Ocean
(v) Western disturbances
(vi) Distance from the coast
(vii) Relief or landform
(viii) Extent of the country
(ii) Why does India have monsoon type of climate?
Ans. India has monsoon type of climate because:
(i) It receives rainfall during June to September due to monsoon winds.
(ii) The monsoon season in India is divided into pre-monsoon, monsoon and post-monsoon seasons.
(iii) India lies in the tropical and subtropical region. Half of its area lies south of the Tropic of Cancer 23°30'N. (iv) Atmospheric conditions, surface winds, upper air circulation, western disturbances and tropical cyclones play an important role in controlling the climate of the country.
(v) The climate of India is highly influenced by monsoon winds.
Thus, it is clear that monsoon climate is found in India due to its geographical location.
(iii) In which part of India is the daily temperature high and why?
Ans. The daily temperature is high in the north-western parts of India, such as Rajasthan, Punjab, Haryana, western Uttar Pradesh and Delhi. Here the temperature goes up to 48 degrees Celsius in summer. This happens because low air pressure conditions prevail in the north-western parts during May-June. To compensate for this low air pressure condition formed in the north-western parts of the country, hot, dry winds, called Loo, start blowing from the western direction and dust storms occur.
North-western India is surrounded by the Thar Desert. The desert sand gets heated during the day and cools down quickly at night which affects the day temperature of the neighbouring areas.
(iv) Which winds cause rainfall on the Malabar coast?
Answer: The Malabar coast situated in the southwest of India (Kerala) receives annual rainfall of about 250 cm due to the Arabian Sea branch of the southwest monsoon. When the southwest monsoon advances, the mountain range Western Ghats situated in Kerala acts as a barrier in the path of monsoon winds and clouds. Hence the Malabar coast receives the highest rainfall. However, the eastern wind-facing slope of the Western Ghats falls in the rain shadow zone during the advance of the southwest monsoon winds.
(v) Define monsoon. What do you understand by a break in the monsoon?
Answer: Monsoon is derived from the Arabic word "Mausim", which means "season" or 'season' i.e. monsoons are those winds whose direction reverses according to the season or weather.
Monsoon winds are known as advancing monsoon winds from the southwest direction from June to September and retreating winds from the northeast direction from October to December.
Monsoon rains occur continuously for some days during the rainy season and some days are rainless. Monsoon break refers to those days or time which is a rainless interval during the monsoon season.
(vi) Why is monsoon considered a unifying force?
Answer. The effect of the unity of monsoon on the Indian peninsula is very clear. The change in wind directions according to the seasons and the weather conditions related to them give a rhythm to the seasonal cycles. The uncertainties of rainfall and its uneven distribution is a distinctive feature of the monsoon.
The entire Indian landscape, its fauna and flora, its agricultural cycle, human life and their festivals and celebrations, all revolve around this monsoon rhythm. From north to south and east to west, all Indians wait for the arrival of monsoon every year. These monsoon winds provide us with water, speed up the process of agriculture and bind the entire country together.
3. Why does the amount of rainfall decrease from east to west in North India?
Ans. The amount of rainfall in the North Indian plains situated in the foothills of the Himalayas in northern India decreases continuously from east to west because when the Bay of Bengal branch of the monsoon hits the Himalayas and moves from Kolkata in the east to Delhi in the west, the distance from the coast increases and these winds gradually come bringing rain, then the moisture (humidity) in them decreases. Therefore, there is a decrease in rainfall from east to west.
4. Give reasons.
(i) Why is there a seasonal change in the direction of wind in the Indian subcontinent?
Ans. In winters, as the sun moves southwards, the low pressure area over the northern plains weakens due to which the monsoon winds blow from north-east to south during this period. During summers, a low pressure area develops in the interior of the Asian continent affecting north-western India. Due to this, winds start blowing from the sea towards the land. With the change in the progress of monsoon, the change in weather causes reversal of the direction of winds in the Indian subcontinent.
(ii) Most of the rainfall in India occurs in a few months only. Why?
Ans. Most of the rainfall in India occurs during the four months of the rainy season i.e. June, July, August and September. This is the time of the south-west monsoon. During this period, moisture-laden winds blow from the sea towards the land. The tropical cyclones that develop during this period increase the amount of rainfall. Therefore, most of the rainfall in India occurs in a few months only.
(iii) The Tamil Nadu coast receives rainfall during winter. Why?
Ans. Most of the rainfall on the Coromandel coast in Tamil Nadu occurs in October, November and December due to the retreating north-east monsoon winds. These winds bring moisture from the Bay of Bengal and cause heavy rainfall on the Coromandel coast on the east coast. Therefore, Tamil Nadu receives rainfall during winter, when the monsoon season is over in most parts of the country.
(iv) The delta region of the east coast is frequently affected by cyclones. Why?
Ans. Tropical cyclones occur during the monsoon months as well as in the months of October and November and are a part of the easterly flow and affect the coastal areas of the country.
These tropical cyclones are low pressure areas over the Bay of Bengal especially during seasonal changes (March-April and October-November months). These tropical cyclones are often destructive. They cause heavy rainfall. These cyclones strike West Bengal and Bangladesh (Ganga Delta). They cross the east coast and affect the states of Orissa, Andhra Pradesh, Tamil Nadu and Kerala. The densely populated areas of the Mahanadi, Godavari, Krishna and Kaveri deltas are the main areas affected by these tropical cyclones.
(v) Rajasthan, some parts of Gujarat and the rain shadow region of the Western Ghats are drought-affected areas. Why?
Ans. The western part of Rajasthan is desert. It receives less than 20 cm of annual rainfall. Rajasthan is under the influence of the southwest summer monsoon. The Aravalli mountain range lies parallel to the direction of the southwest monsoon coming from the Arabian Sea. Hence, the following mountain system is unable to block these winds.
This region is located at a considerable distance from the Bay of Bengal. On reaching Rajasthan, the Bay of Bengal monsoon becomes dry and loses its moisture. Hence, western Rajasthan is a dry region.
Also, Rajasthan and Gujarat are at a considerable distance from the Himalayan region, hence they do not come under the influence of the monsoon that brings rain to the sub-Himalayan region.
The leeward slopes of the Western Ghats lie in the rain-shadow, but there is no guarantee of rainfall, hence this region also falls under the drought prone regions of the country.
5. Explain the regional variations in the climatic conditions of India with examples.
Ans.
(i) Despite almost uniformity in the general pattern, there are clear regional variations in the climatic conditions of the country. (ii) In summer, the temperature in some places in the Rajasthan desert reaches about 50°C, while the temperature in Pahalgam in Jammu and Kashmir is about 20°C. On winter nights, the temperature in Drass in Jammu and Kashmir may be -45°C, while in Thiruvananthapuram it may be 22°C.
(iii) In some areas, the difference between night and day temperatures is very high. In the Thar Desert, the day temperature may be as high as 50°C, while the same night it may drop to 15°C. On the other hand, in Kerala or Andaman and Nicobar, the day and night temperatures are almost the same.
(iv) Precipitation in the Himalayas occurs mostly as snow and in the rest of the country it occurs as rain. (v) Annual rainfall varies from 400 cm in Meghalaya to less than 10 cm in Ladakh and western Rajasthan.
(vi) Most parts of the country receive rainfall from June to September, but some areas like Tamil Nadu coast receive most of the rainfall in October and November.
(vii) Generally, coastal areas have less temperature variation. In the interior parts of the country, seasonal variation is more.
(viii) In the northern plains, the amount of rainfall generally decreases from east to west.
6. Describe the condition and characteristics of winter season.
Ans. Winter:-
Winter season starts from mid-November in northern India and lasts till February. December and January are the coldest months in the northern part of India. The temperature decreases as we move from south to north. The average temperature of Chennai on the east coast is between 24°C to 25°C, while in the northern plains it is between 10°C to 15°C. Days are hot and nights are cold. Frost is common in the north and snowfall occurs on the upper slopes of the Himalayas.
In this season, north-eastern trade winds blow in the country. These blow from land to sea and hence most parts of the country have dry weather. Due to these winds, some amount of rainfall occurs on the coast of Tamil Nadu, because there these winds blow from sea to land.
In the northern part of the country, a weak high pressure area is formed, with light winds flowing out of this region. Influenced by the relief, these winds blow from the west and north-west into the Ganga valley. Generally, the skies are clear, temperature and humidity are low and the winds are slack and variable during this season.
Inflow of cyclonic disturbances from the west and north-west into the northern plains is a special feature during winter. This low pressure system originates over the Mediterranean Sea and western Asia and enters India with westerly winds. This causes rainfall in the plains during winter and snowfall in the mountains, which is much needed at that time. Though the total amount of winter rainfall, locally called 'mahavat', is less, it is very important for the Rabi crops.
Winter is not pronounced in the peninsular parts. Due to the influence of sea winds, there is negligible change in the temperature pattern here even during winter.
7. Explain the monsoon rainfall in India and its characteristics.
Answer.
1. The climate of India is called monsoon climate. The climate of India is greatly influenced by monsoon winds. The word monsoon is derived from the Arabic word 'Mausim', which literally means - season. Monsoon means change in the direction of wind according to the season during a year.
2. The effect of monsoon remains in tropical areas between about 20° north and 20° south.
3. Monsoon winds are not regular, but they are of pulsating nature. During flow over tropical seas, they are affected by various atmospheric conditions.
4. The duration of monsoon is from early June to mid-September, between 100 to 120 days.
5. At the time of its arrival, there is a sudden increase in normal rainfall and it continues for several days continuously. This is called monsoon burst.
6. Generally, in the first week of June, the monsoon enters from the southern tip of the Indian peninsula. After this, it gets divided into two parts - Arabian Sea branch and Bay of Bengal branch.
7. The withdrawal of monsoon is a relatively gradual process, which starts from the northwestern states of India in September.
8. Due to monsoon winds, heavy rainfall (more than 250 cm) occurs in the windward parts of the Western Ghats in South India. Whereas the areas of the leeward slope fall in the rain shadow region.
9. A place called Mawsynram in Meghalaya receives the highest rainfall in the world from monsoon winds.
10. The amount of rainfall decreases from east to west in the Ganga valley.
11. Very little rainfall occurs in some parts of Rajasthan and Gujarat.
12. ‘Gap in rainfall’ is another important phenomenon related to monsoon. These breaks in the monsoon are related to the movement of the monsoon trough. Due to various reasons, the trough and its axis keep shifting towards north or south, which determines the spatial distribution of rainfall. When the axis of the monsoon trough is above the plains, then these areas receive good rainfall. On the other hand, when the axis moves near the Himalayas, the plains remain dry for a long time.
13. The intensity and frequency of tropical low pressure also determines the amount and time of monsoon rainfall.
14. Uncertainties of rainfall and its uneven distribution is a specific characteristic of monsoon. Monsoon is known for its uncertainty. There is a difference in the intensity, frequency and time period of dry and wet conditions. Due to this, if there is a flood in one part, then there is drought in the other part. Its arrival and return is often erratic. Therefore, it sometimes disorganizes the agricultural work of the farmers of the country. 15. The entire Indian landscape, its fauna and flora, its agricultural cycle, human life and their festivals, all revolve around this monsoon rhythm. From north to south and east to west, all Indians await the arrival of the monsoon every year.
Map Skills
Show the following on an outline map of India.
(i) Areas receiving more than 400 cm of rainfall.
(ii) Areas receiving less than 20 cm of rainfall.
(iii) Direction of the south-west monsoon over India.
