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.
Answers:
(i) What are the controls affecting the climate of India?
Various factors, both lying within and outside India influence the climate of India. The chief
among them are the following (1) Latitude
(2) Altitude
(3) Physiography
(4) Distance from the sea
(5) Pressure and Winds:
(6) Influence of ocean currents
Ans 2(ii):
(ii) Why does India have a monsoon type of climate?
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 20 ON 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.
(iii) Which part of India does experience the highest diurnal range of temperature and why?
The difference in temperature of a particular place in a single day is called the diurnal range 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 50 OC 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 of diurnal range of
temperature in the Thar Desert.
(iv) Which winds account for rainfall along the Malabar Coast?
South-West monsoons account for the rainfall along the Malabar Coast while North-East
monsoons account for the rainfall along the Coromandal Coast or East Coast.
(v) What are Jet streams and how do they affect the climate of India?
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.
(vi) What do you understand by “break” in monsoon?
Break in 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’.
(vii) Why is the monsoon considered a unifying bond?
India is a vast country with varied topography. On the north the Himalayas protect the subcontinent 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?
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.
(ii) The bulk of rainfall in India is concentrated over a few months.
It is because of the following reasons:
1. Low pressure area remains only for a few months in North-west India and Pakistan.
2. They cause rainfall all over India.
3. After a few months the low pressure area begins to shift towards east and south east.
4. With this shift of the low pressure area rain begins to withdraw.
5. It rains only for June to September in India.
(iii) The Tamilnadu coast receives winter rainfall.
a.Tamil Nadu coast lies on the eastern coast of the Peninsula. During summer Arabian sea
branch of South-west Monsoon ascends the Western Ghats and causes maximum rainfall on its
western side.On the other hand Tamil Nadu coast remains dry due to its location off the way of
South west Monsoon as moving towards east they go on shedding their moisture.
b.During winter,the North East dry Monsoon winds blow over the Bay of Bengal.As they pass
over the Bay of Bengal they pick up moisture and bring rain to the Tamil Nadu coast as now
they are under the effect of on-shore winds,full of moisture.That is why, Tamilnadu coast
receives rainfall more in winter than in summer.
(iv) The delta region of the eastern coast is frequently struck by cyclones.
a.Rainy season does not receive rainfall regularly.
b.When there is dry season tropical cyclones develop on the Bay of Bengal.
c.Intense cyclones comes in the influence of Easterly Jet streams.They are hoosted into
India.They first strike the delta regions on the east coast and cause heavy rainfall.
d.Some cyclones also develop during the season of retreating monsoon.They are very intense
and cause havoc on Orissa,Andhra Pradesh and Tamil Nadu Coast,during October and
November.
(v) Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone.
a. Rajastan and Gujarat generally fall parallel to the Arabian branch of the South west monsoon.
They do not cause rainfall in this region as Aravalli hills fall parallel to these Monsoon winds and
do not cut as a barrier.
b. The windward side of the Western Ghats receive heaviest rainfall due to instant ascend of
SW Monsoon winds on the slopes of the Western Ghats and shed maximum moisture
there.When they cross the windward slopes and come on the leeward side they become dry
and cause very little rainfall. Hence these areas remain rainless or receive very scanty rainfall.
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 55 OC. 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 20 ON 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 10 OC 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 northwest 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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