NCERT Exercise
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 (c) Cherrapunji
(b) Mawsynram (d) Guwahati
Ans. (b) Mawsynram
(ii) The wind blowing in the northern plains in summers is
known as:
(a) Kaal Baisakhi (c)
Trade Winds
(b) Loo (d)
None of the above
Ans. (b) Loo
(iii) Which one of the following causes rainfall during
winters in north-western part of India.
(a) Cyclonic depression (c) Western disturbances
(b) Retreating monsoon (d) Southwest monsoon
Ans. (c) Western disturbances
(iv) Monsoon arrives in India approximately in:
(a) Early May (c) Early June
(b) Early July (d) Early August
Ans. (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
Ans. (b) Warm days and cold nights
2. Answer the following questions briefly.
(i) What are the controls affecting the climate of India?
Ans. India’s climate is
strongly influenced by the Himalayas and the Thar Desert. Monsoon winds,
geographical location of the country, winds blown from the West and other
relief features of the earth plays a great role in directing the climate of
India.
There are
the following factors affecting the climate of India:
(i) Monsoon winds: India's climate is controlled by monsoon
winds. In summer, monsoons are on shore winds. These winds give most of
rainfall to the country. In winter the monsoon winds blow from land to sea as
N.E. Monsoons. These are dry winds.
(ii) Extent of the country: India is a vast country. The northern
part lies in the temperate region and experiences hot summers and cool winters.
The southern part lies nearer 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 these to
give rainfall.
(iv) The Indian Ocean: India lies at the head of the Indian
Ocean. S.W. Monsoons originate from this ocean in summer and give 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. They are
responsible rainfall in north-western parts of India in winter.
(vi) Distance from the sea: The coastal areas experience
marine climate. Generally, these areas have equable climate, but the interior
regions experience extreme or continental type of climate, e.g. north-west
India.
(vii) Relief of the land: Relief influences the distribution
of temperature and rainfall in India. Mountainous areas have low temperatures.
The windward slopes such as Western Ghats receive heavy rainfall while the
leeward slopes (Deccan Plateau) lie in the rain-shadow and are dry.
(ii) Why
does India have a monsoon type of climate?
Ans. India has a monsoon type
of climate because:
(i) It is strongly directed by
the monsoon winds during June to September.
(ii) Monsoon season in
India is further divided into Pre-monsoon, monsoon and post-monsoon seasons.
(iii) India exists in
the tropical and sub-tropical area. Half of its area located at the south to
the Tropic of Cancer 23°30’N.
(iv) The atmospheric
conditions, surface winds, upper air circulation, western disturbances and
tropical cyclones play a significant role in controlling the climate of the
country.
(v) The climate of
India is strongly influenced by monsoon winds. India has a monsoon type of climate
due to its geographical location.
(iii) Which part of India does experience the highest
diurnal range of temperature and why?
Ans. The north-western parts of India, like
Haryana, Punjab, Rajasthan, UP., Delhi, experience diurnal temperature. Here
the temperature goes up to 48 Celsius. This happens because the low-pressure conditions intensify the north-western parts during May-June. Hot, dry winds
namely Loo, starts blowing and dust storms spurt as south-westerly winds blow
violently to compensate the low pressure condition formed in north-western
parts of the country.
The north-western
India is surrounded by the desert. The desert sand becomes hot during the day
and quickly cools down in the night which affects the daytime temperature of
the neighboring regions.
(iv) Which winds account for rainfall along the Malabar Coast?
Ans. Malabar coast in the southwest of India
received very high account about 250 cms of rainfall due to the Southwest monsoon (the Arabian Sea branch of monsoon). When the Southwest monsoon heat
the Malabar coast, the western ghat’s elevation work as a barrier in the way of
monsoon winds and clouds. So Malabar coast received the high amount of
rainfall. Although the leeward side of the western ghat comes in rain shadow
zone during the onwards of Southwest Monsoon winds.
(v) What are Jet streams and how do they affect the
climate of India?
Ans. Jet streams are high-velocity westerly
winds blowing through a narrow zone, around 12,000 meters over the troposphere.
These are actually, westerly winds blowing at higher altitude. Their velocity
(speed) recorded in summer is about 110 km/h and about 184 km/h. in winter.
These blow at the mid-latitude and over sub-tropical regions (north half of
India).
These streams are
located over 27-30° north latitude. The westerly flows are responsible for
western disturbances and the easterly flows cause tropical depressions during
monsoon and even in early winter season.
(vi) Define monsoons. What do you understand by “break” in
monsoon?
Ans. Monsoons are generally rain bearing and
directing winds. This term has been derived from the Arabic word "mausim”
first used by the Arab traders who used to visit India for trading purposes
through sea routes. It means season. We therefore, can state them seasonal
reversal of the wind system in monsoon.
"Monsoon Break
refers to the happening of wet and dry spells during the rainy season. Monsoon
rains take place only for a few days at a time. They are interspersed with
rainless intervals. The monsoon rains take place for a few days continuously
with some rainless breaks. These wet and dry spells of the monsoon rains is
termed as monsoon break.
(vii) Why is the monsoon considered a unifying bond?
Ans. The term "unifying
bond" implies an attachment or affection of something with another. India
has a unique combination of seasons. The different parts of the country
experience different climates during the same time. The location of Himalayas in
the northern India acts as a barrier that saves the country from the strong
cold winds of the Central Asia. The other places with the same latitude
experience extremely cold winds. In the same way, the peninsular India is
covered by the seas from three sides. This arrangement also makes sure a
moderate temperature in India. India is a country where people belonging to
different ethnicities live together. India is an epitome of Unity in Diversity.
Though different parts of the country have different climate in the same time,
but Monsoon is a period which happens to come around the same time every years.
The seasonal reversal of the wind system provides a rhythmic cycle of seasons.
Indian festivities, plant and animal lives, agricultural calendar, etc. share
close ties with the monsoon. Hence, monsoon acts as a unifying bond in India.
3. Why does the rainfall decrease from the east
to the west in Northern India.
Ans. The rainfall decreases from
east to the west in Northern India because monsoon rises from both the Arabian
Sea and the Bay of Bengal, which causes heavy rainfall in the Brahmaputra
valley and the Assam hills. As soon as they move toward Himalayas they take
western turn and move up the Ganga valley, but due its westward approach it
become drier and drier resulting in lesser rainfall North West India. The
shrinking moisture levels results in decrease in rainfall from east to the west.
4. Give reasons as to why.
(i) Seasonal reversal of wind direction takes place over
the Indian subcontinent?
Ans. In winters, the sun moves toward the south, the low pressure
channel over the northern plains becomes feebler causing the monsoon wind to
blow from northeast to south during this period. During summers, low pressure
area develops in the interior of Asian continent impacting the North-Western
India. Because of this sea begin to blow toward the landmasses. The shift in
the progress of monsoon combined with the variation in season causes reversal
of wind direction in the Indian sub-continent.
(ii) The bulk of rainfall in India is concentrated over a
few months.
Ans. The bulk of rainfall in India is received during the four months
of the rainy season i.e. June, July, August and September. This is the period
of South-West Monsoons blowing from sea to land. These seas to land winds are
the rain giver, as these moisture-laden winds are on-shore winds. The tropical
cyclones add to the amount of rainfall. Easterly tropical jet stream, too,
helps in the monsoonal rain during this period.
(iii) The Tamil Nadu coast receives winter rainfall.
Ans. Konkan Coast faces
On-Shore South West Monsoons during summer. The moist laden winds cause heavy
rainfall (more than 250 cms). But these winds do not result in heavy rainfall
on the Coromandel Coast lies on the east of Eastern Ghats. Coromandel Coast
also receives winter rainfall from North Eastern Monsoons, but on Konkan Coast
these winds are off-shore and do not result in rainfall. Thus Coromandel Coast
gets rainfall in both the seasons, but the total amount is less than that of
Konkan Coast.
Tamil Nadu gets most
of rain from North-Eastern Monsoons in October, November and December. These
Winds after picking up moisture from Bay of Bengal fetch more rain on the
eastern coast. This is why; Tamil Nadu receives rain in winter when the fury of
monsoons is over in most parts of the country.
(iv) The delta region of the eastern coast is frequently
struck by cyclones.
Ans. Tropical cyclones are depressions originating over Bay of
Bengal. These tropical cyclones are often destructive. They cause heavy rains.
These cyclones strike West Bengal and Bangladesh (Ganga Delta). They cross the Eastern
coast and affect the states of Orissa, Andhra Pradesh, Tamil Nadu and Kerala.
The thickly populated deltas of Mahanadi, Godavari, Krishna and Kaveri are the
main targets of these tropical cyclones. Likely MOCHA Cyclone struck the
eastern coast in May 2023.
(v) Parts of Rajasthan, Gujarat and the leeward side of
the Western Ghats are drought-prone.
Ans. The western part of Rajasthan
is desert. It gets an annual rainfall less than 20 cms. Rajasthan is under the
influence of South West Summer monsoons. The Aravallis system lies parallel to
the direction of South West monsoons coming from Arabian Sea. So these low
mountain system is unable to check these winds, so western Rajasthan is
practically dry. The southern parts get some rainfall. This area lies at a
great distance from the Bay of Bengal. The Bay of Bengal monsoons become dry
and lose their moisture when they reach Rajasthan. Also, Rajasthan and Gujarat
are at a great distance from the Himalayan region so, they do not come under
the influence of monsoons giving rain in the sub-Himalayan region. The leeward
slopes of Western Ghats remain in rain-shadow, but there is no guarantee of
rainfall hence, this area also comes under the drought prone areas of the
country.
5. Describe the regional variations in the
climatic conditions of India with the help of suitable examples.
Ans. In India, there are perceptible regional
variations in climatic conditions within the country.
(i) In summer, the temperature may be 50°C or
more in some parts of Rajasthan desert, whereas it may be around 20°C in
Pahalgam in Jammu and Kashmir. On a winter night, the temperature at Dassin
Jammu and Kashmir may be as low as -45°C, while Thiruvananthapuram may have a
temperature of +20°C.
(ii) In certain places there is a wide
difference between day and night temperatures. In the Thar Desert, the day
temperature may be 50°C and drops down to near freezing point the same night.
On the other hand, there is hardly any difference between day and night
temperatures in the Andaman and Nicobar Islands or in Kerala.
(iii) While precipitation is mostly in the
form of snowfall in the upper parts of Himalayas, it only rains over the rest
of the country.
(iv) The annual precipitation varies from 400
cm in Meghalaya to less than 10 cm in Ladakh and Western Rajasthan.
(v) Most parts of the
country receive rainfall from June to September, but Tamil Nadu coast receives
rainfall during autumn and early winter.
6. Discuss the mechanism of monsoons.
Ans. To understand the mechanism of
monsoons the following facts are important:
(i) The difference in the rate of heating and
cooling of land and sea on a large scale. During summers a low pressure area
develops on the Indian landmass while the seas around experience comparatively
high pressure.
(ii) The shift of the position of the
Inter-Tropical Convergence Zone. This is the equatorial trough normally
positioned about 5°N of the equator, also known as the monsoon trough during
the monsoon season.
(iii) The presence of high pressure area, east
of Madagascar approximately at 20°S over the Indian Ocean. The intensity and
position of this high pressure area affects the Indian monsoons.
(iv) The Tibetan high level plateau gets
intensely heated during summers which results in strong vertical currents and
formation of high pressure over the plateau at about 9 kilometers above sea
level.
(v) The movement of the westerly jet to the
north of the Himalayas and the presence of the tropical easterly jet over the
Indian peninsula during summers.
Apart from this, it
has also been noticed that changes in the pressure conditions over the southern
Oceans also affect the monsoons.
7. Give an account of weather conditions and
characteristics of the cold season.
Ans. The temperature, atmospheric pressure,
wind, humidity and precipitation usually determine the weather conditions at
any point of time (a day or a week) and the space. Weather is generally
expressed as cool, hot, windy, calm, cloudy, bright, wet or dry. Actually,
atmospheric conditions are called the weather. We experience hot weather in
summers, cold weather in winters, wet weather in rainy season and cool and dry
during October-November and the March and April respectively.
Weather phenomenon changes rapidly. Any day
may have different weather conditions. We just feel suffocated due to humidity
and scorching heat of July month. Suddenly clear sky is covered with clouds and
it starts raining with lightning and strong wind. Something of such strange
happens when cyclonic depression cause damages in deltas of the Mahanadi,
Kaveri, Godavari and Krishna rivers.
Following are the characteristics of the cold
season.
(i) It begins from mid-November in Northern
India and pervades here till February. The mid-months, i.e., December and
January are the coldest months.
(ii) The temperature gradually decreases
during this period from south to the north. For example, in Chennai 20°-25°C
while it is 10°15°C in northern plains.
(iii) Days are experienced warm while the
nights are cold. Days are cut short while nights are longer.
(iv) Most part of the country remains dry
(i.e., without winter rain) during this period and only Tamil Nadu coast
including Coromandel coast receive heavy winter rains.
(v) Coastal areas
enjoy moderate temperature throughout the year while the rest of the country
experiences cold, heat, humid and moderate according to the cycle of the
seasonal change. It means reversal of winds or monsoon type climate has more
seasonal variations to experience.
8. Give the characteristics and effects of the
monsoon rainfall in India.
Ans. The characteristics of Monsoon
season is discussed below:
a. It gives water into most of the parts of
the country except some leeward sides’ rain shadow regions and desert areas.
b. Early in the season, the windward side of
the Western Ghats receives heavy rainfall of more than 250 cm.
c. The rain shadow areas of Deccan Plateau and
parts of Madhya Pradesh also get scanty rains.
d. The maximum rainfall is recorded in the
north-eastern parts of the country. Mawsynram happens to be the wettest place
in the world.
e. Indian monsoon takes “breaks” viz. sprinkled
with rainless intervals. This happens because of the monsoon trough, caused due
to spatial distribution of rainfall.
f. The frequency and intensity of tropical
depressions also determine the amount and duration of monsoons.
g. The monsoon trough over the northern plains
becomes weaker causing the months of October-November, a period of transition
from hot rainy season to dry winter conditions.
The effects of Monsoon season is discussed
below:
a. When the rains are heavy, the rivers get
flooded causing heavy damage in the plains year after year.
b. A dry spell would cause as much misery as
the river floods.