NCERT / CBSE, Social Science (Geography)
Contemporary India - I
Chapter-4, CLIMATE
Textbook Exercise Questions - Answers
Q.1: Choose the correct answer from the four alternatives.
(i) Which one of the following places receives the highest rainfall in the world?
a. Silchar
b. Cherrapunji
c. Mawsynram
d. Guwahati
(ii) The wind blowing in the northern plains in summer is known as
a. Kaal Baisakhi
b. Trade winds
c. Loo
d. None of the above.
(iii) Which one of the following causes rainfall during winters in the North-Western part of India:
a. Cyclonic depression
b. Retreating monsoon
c. Western disturbances
d. Southwest monsoon
(iv) Monsoon arrives in India approximately in:
a. Early May
b. Early July
c. Early June
d. Early August
(v) Which one of the following characterizes 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: (i) c (ii) c (iii) c (iv) b
Q.2: Answer the following questions briefly.
(i) What are the controls affecting the climate of India?
(ii) Why does India have a monsoon type of climate?
(iii) Which part of India does experience the highest diurnal range of temperature and why?
(iv) Which winds account for rainfall along the Malabar Coast?
(v) What are Jet streams and how do they affect the climate of India?
(vi) Define monsoons. What do you understand by “break” in monsoon?
(vii) Why is the monsoon considered a unifying bond?
Ans 2(i):
Various factors, both lying within and outside India influence the climate of India. The chief among them are the following -
(1) Latitude:
The Tropic of Cancer passes through the middle of the country from the
Rann of Kutchh in the west to Mizoram in the east. The areas lying in
the south of the Tropic of Cancer belong to the tropical area while the
remaining areas lying in the north of Tropic of Cancer belong to the
sub-tropical area. Therefore, India’s climate has characteristics of
tropical as well as sub-tropical areas.
(2) Altitude:
With the increase in altitude the atmosphere becomes less dense and
temperature decreases. That is why hills are cooler during summer. India
has an average height of 6000 meters in the north while in the south
there is a vast coastal area with maximum elevation of about 30 meters.
It is because of the differences in altitudes or relief that while it is
hot during summer in the Plains of Punjab, Haryana, UP etc., the places
in the mountains like Nainital, Darjeeling, and Ooty etc. are cool.
(3) Physiography:
Physiography also plays an important role in determining the climate of
a place. India has a varied Physiography. The Himalayas in the north
act as great barrier to the cold winds from Central Asia. In absence of
the Himalayas, India would have been a very cold country. The location
of the Arabian Sea, the Indian Ocean and the Bay of Bengal on the three
sides of India exert a moderating influence on the climate of India.
This ocean, sea etc. being a huge water body acts as a store house of
moisture which India needs very badly. Without these water bodies India
would have been a very hot country with a climate like that of a dessert
like Sahara in Africa.
(4) Western Cyclonic Disturbances:
The western cyclonic disturbances are weather phenomena of the winter
months brought in by the westerly flow from the Mediterranean region.
They usually influence the weather of the north-western regions of
India. In winter, in northern India, Punjab and Haryana get some rain
from these western disturbances.
(5) Pressure and Winds:
India lies in the region of north-easterly winds. These winds originate
from sub-tropical high pressure belt of northern hemisphere. The fury
of monsoons as well as long dry spell in India is mainly due to the
pressure conditions which develop in the surrounding countries like East
Africa, Iran, and Central Asia.
Winds especially Typhoons originating
in China Ocean currents along with onshore winds and monsoon winds have
a great control on the climate of India. Also the upper air circulation
such as Jet Streams play a dominant role in determining the climate of India.
Ans 2(ii):
The
word “Monsoon” is derived from the Arabic word ‘Mausim’ which literally
means season. Monsoon refers to the seasonal reversal in the wind
direction during a year. The monsoon winds are confined to the tropical
area roughly between 20ON to 20OS latitudes. But
in the Indian subcontinents, because of the Himalayan ranges, they bring
the whole subcontinent under the sway of the moist bearing winds for 2 -
5 months roughly between May to October. Almost 90% rainfall in India
is due to these monsoon winds. India would have been an arid land or
desert if there had been no phenomena of monsoons. It is because of
these reasons that the climate of India is described as monsoon type.
Ans 2(iii):
The
difference in temperature of a particular place in a single day is
called the diurnal change of temperature. The highest diurnal range of
temperature has been found in Thar Desert of Rajasthan. At this place
the day temperature may rise to 50OC and may drop down to near freezing point the same night.
The
highest diurnal range of temperature has been found at the Thar Desert
because there the weather conditions drastically change during the day
and during the same night. The great difference between the day and
night temperatures result in the highest range of diurnal range of
temperature in the Thar Desert.
Ans 2(iv):
South-West
monsoons account for the rainfall along the Malabar Coast while
North-East monsoons account for the rainfall along the Coromeodal Coast
or East Coast.
Ans 2(v):
Jet
Streams are fast flowing winds blowing in a narrow zone in the high
altitude above 12000 m in troposphere. There are a number of separate
jet streams whose speed varies from 110 km/h in summer to about 184 km/h
in winter.
In
winter the sub-tropical westerly jet streams bring rain to the western
part of India, especially Himachal Pradesh, Haryana and Punjab. In
summer the sub-tropical easterly jet blows over Peninsular India
approximately at 14ON and bring some rain and storm.
Ans 2(vi):
Monsoon
- The word “Monsoon” is derived from the Arabic word ‘Mausim’ which
literally means season. Monsoon is thus the rain-bearing winds which
reverse their direction with the change of ‘mausam’ or season and blow
throughout the Indian subcontinent, especially from May to October.
Break Monsoon
- The monsoon rain takes place only for a few days continuously at a
time. They are inter-spread with rainless intervals. Thus monsoon rains
have wet and dry spells. So, this phenomena associated with the rainfall
during monsoon is known as ‘break’.
Ans 2(vii):
India
is a vast country with varied topography. On the north the Himalayas
protect the sub-continent from the extreme cold winds of Central Asia.
This enables northern India to have uniformly higher temperatures as
compared to other areas on the same latitudes. Similarly the peninsular
plateau, under the influence of sea from three sides, has moderate
temperatures. Despite such moderating influences there are great
variations in the temperature conditions.
Nevertheless,
the unifying influence of the monsoons on the Indian subcontinent is
quite perceptible. The Indian landscape, its animal and plant life, the
agriculture calendar and the life of the people including their
festivities and economic conditions revolve around the monsoon. Year
after year, the people of India from North to South and from East to
West eagerly await the arrival of the monsoon. These monsoon winds bind
the whole country by providing water to set the agricultural activities.
Thus, in view of the above the monsoon is considered as a unifying bond
for this subcontinent.
Q.3: Why does the rainfall decrease from the east to the west in Northern India?
Ans:
In summer, the monsoons rise both from the Bay of Bengal and the
Arabian Sea. The monsoons which rise from the Bay of Bengal cause heavy
rainfall in the Brahmaputra Valley and the Assam Hills (i.e. in
Cherrapunji). Because of the Himalayas they then take a western turn and
move up the Ganga Valley but as they proceed westwards they become
drier and drier and therefore they cause less and less rain as they move
forward. As such Kolkata gets a rainfall of 119 cm, Patna 105 cm,
Allahabad 76 cm and Delhi 56 cm.
Q.4: Give reasons as to why,
(i) Seasonal reversal of wind direction takes place over the Indian subcontinent?
(ii) The bulk of rainfall in India is concentrated over a few months.
(iii) The Tamilnadu coast receives winter rainfall.
(iv) The delta region of the eastern coast is frequently struck by cyclones.
(v) Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone.
Ans
4(i): Monsoons blow from northeast India towards the sea during winter
(November to April) but with the beginning of summer they begin to
reverse their direction. During winter (October - November) with the
apparent movement of sun towards the south, the low pressure trough over
then northern plains becomes weaker which causes the monsoon wind to
blow from northeast to south during this period.
In summer, areas of low pressure develop in north and northwest parts of India due to which winds from the high pressure area i.e.
sea begin to blow towards the land masses. So, a shift in the
development of monsoon trough or low pressure trough along with the
change of season is the main reason for the reversal of wind direction
in Indian subcontinent.
Answers
of Q.4(ii) to 4(v) are given in a separate post. [Check the answers of
Sample and Objective Questions, link given below].
Q.5: Describe the regional variations in the climatic conditions of India with help of suitable examples.
Ans:
The climate of India is described as that of the monsoon type. But
within this general pattern there are found certain regional variations
in climatic conditions. This is because of the variations in
temperature, precipitation, atmospheric pressure, wind, humidity and
altitude from place to place. The following are a few examples which
prove the above fact:
Range of Temperature
- Temperature has great bearing on the climate, so difference in
temperature is bound to create variation in the climate. In India there
are places like, Rajasthan and south-west Punjab, where the mercury
rises even up to 55OC. On the other hand, there are places like Dras, near Kargil, where the temperature sometimes, touches as low as -45OC.
Direction of the Rain-bearing Winds
- The direction of the Rain-bearing winds has a great impact on the
climate of a place. The summer monsoons arising from the Arabian Sea
because of their south-west direction strike the Western Ghats first and
cause a heavy rainfall there (about 250 cm). But these winds reach the
Eastern Ghats last of all so there is less rainfall in Tamil Nadu and
consequently it is much lower as compared to the rainfall on the Malabar
Coast of the Western Ghats.
Form of Precipitation
- The form of precipitation whether it is in the form of light rains or
heavy snow has also a great-bearing on the climate of an area. In
winter north-west of India gets some rains due to the Western
Disturbances. As a result, there is little rain in the plains of Punjab
and Haryana but there is heavy snowfall in the Western Himalayas
especially in Himachal Pradesh and Jammu and Kashmir. It is all due to
the change in the form of precipitation.
Amount of Rainfall
- Difference in rainfall is bound to create variations in climate. In
India, there are places like Mawsynram which receives 1080 cm of
rainfall annually. This is perhaps the highest rainfall all over the
world. On the other hand, there are places in India, especially in
Rajasthan, which gets 20 cm of annual rainfall.
Rainfall Regime or Seasonal Distribution of Rains
- In India, there are many parts which get rains only in summer while
there are others which dry in that season. On the other hand, there are
certain places which get rains in winter alone while there are others
which get scanty or no rainfall in winter. For example Tamil Nadu and AP
get much of their rainfall in winter season, and in summer they are
almost dry. This seasonal distribution of rainfall has a great bearing
on climate. In summer both Tamil Nadu and AP experience dry and hot
season while the rest of the country especially Kerala, Karnataka and
Maharashtra on the west-coast of India has a pleasant climate.
Q.6: Discuss the mechanisms of monsoons.
Ans:
The word ‘monsoon’ refers to the seasonal reversal in the wind
direction during a year. The monsoon winds are confined to the tropical
area lying between 20ON to 20OS latitudes. The
mechanism of monsoons or the phenomena of the seasonal reversal in wind
direction is related to the following fact:
1. The differential heating and cooling of land and water.
2. The shift of the position of Inter Tropical Convergence Zone (ITCZ) in summer over the Ganga plain.
3.
The presence of high pressure area, east of Madagascar over the Indian
Ocean. The intensity and position of this high pressure area affects the
Indian monsoon.
4.
The Tibetan plateaus gets intensely heated during summer resulting into
strong vertical air currents and the information of low pressure over
the plateau.
5.
The movement of the westerly Jet Stream to the north of the Himalayas
and the presence of the tropical easterly Jet Stream over the Indian
Peninsula during summer.
The
meteorologists have found out a seesaw kind of relationship between the
meteorological changes going on over the Pacific and the Indian Ocean.
Whenever there is high pressure in the subtropical region of the Pacific
Ocean in the northern hemisphere, the pressure in the south of Indian
Ocean tends to be low and vice-versa. This is known as the ‘Southern Oscillation’ or SO
which causes the shifting of winds across the equator in different
directions. Besides the above facts, some other events such as ElNino,
ENSO etc. are also connected to the mechanism of monsoons.
Q.7: Give an account of weather conditions and characteristics of the cold season.
Ans:
The cold weather persists from December to February throughout India.
January is the coldest month. During this period temperature varies from
10OC to 15OC in northern plains and 25OC
in southern parts of the country. There is high pressure in northern
plains due to the cold climatic conditions. The cold dry winds blow from
the high pressure towards the low pressure equatorial regions. These
winds are north-westerly in the Ganga plains and north-easterly over the
Bay of Bengal. Only two parts of the country receive rain in this
season. First is the north-west part of the country which receives
rainfall, caused by the Western Cyclonic Disturbances originating in the
Persian Gulf and Mediterranean regions. Second is the coast of Tamil
Nadu which gets rainfall in winter because of the north-east winds on
Retreating Monsoons which blow over the Bay of Bengal. But in other
parts of the country, the weather is pleasant with clear skies and
bright sunshine.
Q.8: Give the characteristics and effects of the monsoon rainfall in India.
Ans: Chief Characteristics and Effects of the Monsoons or Monsoon Rainfall
(a)
The monsoons account for 90% of the rainfall received by India. Almost
every part of the country except the east coast of Tamil Nadu receives
the bulk of rainfall from the summer monsoons.
(b) The rainfall is neither continuous nor regular even in the wettest areas.
(c)
Overall rainfall is not the same each year. The monsoons may be strong
or weak in a particular year depending on the intensity and frequency of
depression in the Bay of Bengal.
(d) The monsoon rains are not evenly distributed.
(e)
A low pressure near the Himalayas may result in heavy rains in the
hills causing floods in the plains or the plains may face prolonged dry
spells.
(f)
Sometimes, the monsoons may break too early or too late. There may be
too long or too many breaks in the monsoons, which may retreat too early
or too late. All these factors upset the agricultural operations making
agriculture in India a mere gamble.
Sometimes,
the effects of the monsoons or its uneven distribution create a number
of problems. Like if there is too much rain it causes floods and havoc
all around. On the other hand insufficient rain in a year or over some
years results in draught, famine, food-insecurity, starvation and death.
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