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a)Retreating monsoon |
i) Prevails in the Northern Plains. [c] |
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b)Poor rainfall |
ii) Blows during the day. [d] |
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c)October heat |
iii) North-Eastern parts of India. [e] |
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d)Sea breeze |
iv) Rainfall in the Coromandel Coast. [a] |
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e)Rainfall over 200 cm |
v) Rain shadow. [b] |
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f)Coastal areas |
vi) Equable climate. [f] |
3. Answer the following question in brief.
a. Why is the advancing monsoon also called the south-west monsoon?
= The advancing monsoon winds cross the Equator and get deflected as the south-west winds. These winds are moisture-laden as they blow largely over the Indian Ocean. These South-west winds, as they strike the west coast of India, are called the south-west monsoon winds.
b. Why do monsoon winds enter the west coast of India in the month of June?
= Monsoons winds enter the west coast of India in the month of June because by the end of May, the low pressure belt in the Gangetic Plain becomes more intense. There is a strong pressure gradient from south to north. The south-west winds strike the west-coast of India.
c. What is meant by October heat?
= By the middle of September, the temperature decreases considerably and so does the intensity of low-pressure in north-west India. Monsoon starts withdrawing from Punjab and Rajasthan in this period. In the beginning of October, clear skies prevail over the Northern Plains. People in the plains experience the phenomenon of October heat.
d. What are the effects of tropical cyclones?
= Tropical cyclones originate near the Andaman Islands in the Bay of Bengal. They travel towards the west and north-west and one of the deltas along the east-coast. The Kaveri Delta and the Krishna-Godavari Delta are often affected by such cyclones. Some cyclones reach the Mahanadi Delta and the Ganga Delta as well.
e. Which regions in south India get rainfall during winter?
= The Coromandal Coast gets most of the rainfall during the retreating monsoon season during winter.
f. Which regions regions receive very high rainfall?
= On the southern slopes of the Khasi and Jaintia Hills that are at right angles to the path of the Bay of Bengal branch of the monsoon.
g. Give a brief description of the following.
i) Subtropical westerly jet stream.
= The subtropical western jets blow over the Himalayas during winter and influence the western disturbances to move eastward towards India from the Mediterranean Sea. The western disturbances are surface winds and get pulled by the high speed upper atmosphere jet streams in their direction.
ii) ITCZ
= This is a convergence zone for the south-east and north-east trade winds. The Inter Tropical Convergence Zone or ITCZ usually lies on the Equator(0°). However, during summer, with the Sun's apparent shift of the overhead position on the Tropic of Cancer, the ITCZ shifts a few degrees to the north. This also attracts the south-east trade winds, which cross the Equator and enter India as south-west monsoon winds. Thus the shifting of the position of ITCZ plays a major role in influencing the arrival of monsoons in India.
iii) Tropical cyclones.
= The Tropical cyclones originate near the Andaman Islands in the Bay of Bengal. They travel towards the west or north-west and reach one of the deltas along the east coast. The Kaveri Delta and the Krishna-Godavari Delta are often affected by such cyclones. Some cyclones reach the Mahanadi Delta and the Ganga Delta as well.
iv) Extreme climate.
= Srinagar and Bikaner have annual range of temperature exceeding 20°C. These places have extreme climate. Temperature in these places shows considerable fluctuation between summer and winter.
v) Rain Shadow.
= The Himalayas act as a climatic divide and force the wind to ascend up the slopes. This produces heavy rainfall on the windward slope. The leeward slope is a rain shadow, which is dry and receives very little rainfall.
4. Answer the following questions in detail.
a. How does ITCZ influence the monsoon in India?
= This is a convergence zone for the south-east and north-east trade winds. The Inter Tropical Convergence Zone or ITCZ usually lies on the Equator(0°). However, during summer, with the Sun's apparent shift of the overhead position on the Tropic of Cancer, the ITCZ shifts a few degrees to the north. This also attracts the south-east trade winds, which cross the Equator and enter India as south-west monsoon winds. Thus the shifting of the position of ITCZ plays a major role in influencing the arrival of monsoons in India.
b. What are jet streams? What is their importance with regards to the climate of India.
= Jet streams are a narrow belt of high speed, upper air current blowing above 1200 m above the Earth's surface.
The subtropical westerly jets blow over the Himalayas during winter and influence the western disturbances to move eastward towards India from the Mediterranean Sea. The western disturbances are surface winds and get pulled by the high speed upper atmosphere jet stream in their direction. In a similar way, the tropical easterly jet streams blow over peninsular India during summer and tend to influence the movement of the south-east trade winds towards India. As a result, they influence monsoon rainfall over India.
c. Why does the Coromondel Coast get more rainfall during the retreating monsoon?
= The Coromondel Coast gets more rainfall during the retreating monsoon because of the Tropical cyclones which originate near the Andaman Islands in the Bay of Bengal. They travel towards the Kaveri Delta and the Krishna-Godavari Delta.
d. What is the impact of monsoon in India.
= The seasonal cyclone of the monsoon has its impact all over India. Farmers prepare their fields and eagerly await the arrival of the monsoon. Most of the crop grow in the Peninsular Plateau depends only on rainfall.
Late arrival of the monsoon or early retreat of the monsoon causes low yields of kharip crops or failure of crops. The monsoon rainfall varies from year to year. Floods and droughts are common in one part of India or another. Floods occur frequently in Assam and north Bihar. Droughts occur in the interior of the peninsula and in Rajasthan and Gujarat.
e. Describe the pattern of rainfall in different parts of the country.
= There are two regions receiving very high annual rainfall of more than 200 cm. These are:
i) The Western Ghats and the Western Coastal Plain.
ii) Parts of the North-East.
Annual rainfall of 100-200 cm is received in the following areas:
i) The Himalayan region, from Kashmir to Sikkim.
ii) The Ganga Plains in Bihar and West Bengal.
iii) The north-eastern part of the Peninsular Plateau.
iv) Parts of east coast.
v) Assam Valley and Purvanchal Hills.
Three regions get low annual rainfall of less than 60 cm. These are:
i) North-West India covering the Rajasthan desert.
ii) Rain-shadow region on the leeward side of the Western Ghats.
iii) The region beyond the Greater Himalayas in Jammu and Kashmir.
6. Thought Provoking question answer:
a. Why does Mumbai receive more rainfall than Pune?
= Mumbai is located on the crest of the Western Ghats, gets more rainfall, where as Pune located a few kilometres away to the east of the Western Ghats, gets an annual rainfall of only 70 cm as it is a rainshadow region.
b. Why is temperature in Shimla lesser than Delhi in winter?
= Temperature decreases at the rate of 1°C for every 165 m. Shimla is located in mountain region whereas Delhi is located in plains. Having higher altitude, Shimla has lesser temperature than Delhi in winter.
c. Why is Kanniyakumari warmer than Chandigarh in winter?
= The surrounding seas have a moderating effect on the temperature of the coastal regions. So, Kanniyakumari is warmer than Chandigarh as it is located in coastal region and Chandigarh is located in interior region.
d. Why does Kerala receive rainfall much earlier than Delhi?
= Kerala receives rainfall much earlier than Delhi because the south-west monsoon winds break or burst over the beginning of June. Then it reaches Delhi much later.
e. Why does Mumbai have an equable climate, whereas Nagpur experiences an extreme climate?
= Seas have a moderating effect on the temperature of the coastal regions. For example, in Maharashtra, Mumbai has an equable climate, while Nagpur in the interior experiences an extreme climate.