Question 1:
Choose the right 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 |
(ii) The wind blowing in the Northern Plains in the summers is known as
| (a) Kaal Baisakhi | (c) Trade Winds |
| (b) Loo | (d) None of the above |
(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 |
(iv) Monsoon arrives in India approximately in
| (a) Early May | (c) Early June |
| (b) Early July | (d) Early August |
(v) Which one of the following characterises the cold weather season in India?
| (a) Warm days and warm nights | (c) Cool days and cold nights |
| (b) Warm days and cold nights | (d) Cold days and warm nights |
Answer:
(i) Which one of the following places receives the highest rainfall in the world?
| (a) Silchar | (c) Cherrapunji |
(b) Mawsynram | (d) Guwahati |
(ii) The wind blowing in the Northern Plains in the summers is known as
| (a) Kaal Baisakhi | (c) Trade Winds |
| (b) Loo | (d) None of the above |
(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 |
(iv) Monsoon arrives in India approximately in
| (a) Early May | (c) Early June |
| (b) Early July | (d) Early August |
(v) Which one of the following characterises the cold weather season in India?
| (a) Warm days and warm nights | (c) Cool days and cold nights |
| (b) Warm days and cold nights | (d) Cold days and warm nights |
Question 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?
Answer:
(i) The controls affecting the climate of India are: latitude, altitude, pressure and wind system, distance from the sea, ocean currents and relief features.
(ii) The climate of India is strongly influenced by monsoon winds. Hence, it has a monsoon type of climate.
(iii) The north-western part of India comprising the Indian Desert experiences the highest diurnal range of temperature. This is because of the fact that sand (found in ample quantity in this region) gains and loses heat very quickly. As a result of this phenomenon, there is a wide difference between day and night temperatures in this region. The day temperature may rise to 50°C and drop down to near 15°C the same night.
(iv) The south-west monsoon winds are responsible for rainfall along the Malabar Coast.
(v) Jet streams are a narrow belt of high-altitude winds in the troposphere. The sub-tropical westerly jet stream blowing south of the Himalayas are responsible for the western cyclonic disturbances experienced in the north and north-western parts of the country during the winter months. The sub-tropical easterly jet stream blowing over peninsular India is responsible for the tropical cyclones that affect the eastern coastal regions of India during the monsoon as well as during the October to November period.
(vi) Monsoon refers to the complete reversal of winds over a large area leading to a change of seasons.
“Break” in monsoon refers to the wet and dry spells of the monsoon. In other words, the monsoon rains take place for a few days at a time. They are interspersed with rainless intervals.
(vii) Despite variations in temperature conditions across India, a sense of unity is imposed by the monsoon. The seasonal alteration of the wind systems and the associated weather conditions provide a rhythmic cycle of seasons that binds the entire country.
Question 3:
Why does the rainfall decrease from the east to the west in Northern India?
Answer:
The amount of rainfall decreases from east to west in Northern India because of the progressive decrease in the humidity of the winds. As the moisture-bearing winds of the Bay of Bengal branch of the southwest monsoon move further and further inland, they exhaust most of the moisture they carry along with them. This consequently leads to a gradual decrease in the amount of rainfall from east to west.
Question 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 Tamil Nadu 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.
Answer:
(i) The seasonal reversal of wind direction over the Indian subcontinent is the result of the Coriolis force. It is an apparent force caused by the Earth’s rotation. The Coriolois force is responsible for deflecting winds towards the right in the northern hemisphere and towards the left in the southern hemisphere.
(ii) The rainfall received by India is largely due to the south-west monsoon winds. The duration of the monsoon is between 100 to 120 days. Hence, the bulk of rainfall received by the country is concentrated over a few months.
(iii) During the winter season, north-east trade winds prevail over India. They blow from land to sea and hence, for most part of the country, it is a dry season. However, the Tamil Nadu Coast receives winter rainfall due to these winds. This is because in this region these winds blow from sea to land, thereby carrying moisture along with them.
(iv) The delta region of the eastern coast of India is frequently struck by cyclones. This is because the cyclonic depressions that originate over the Andaman Sea are brought in by the sub-tropical easterly jet stream blowing over peninsular India during the monsoon as well as during the October to November period.
(v) Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone because of the scanty rainfall received by these regions during the monsoon rains. The progressive decrease in the humidity of the winds of the Bay of Bengal branch causes the amount of rainfall to decrease from east to west in northern India. As the leeward side is the rain-shadow area, the regions lying in this region receive very little rain from the Arabian Sea branch. It is the windward side of the Ghats that receives the maximum rain.
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Question 5:
Describe the regional variations in the climatic conditions of India with the help of suitable examples.
Answer:
Despite the overall unity accorded by the monsoon, there are visible regional variations in climatic conditions within India. Regardless of the moderating influences of the Himalayas in the north and the sea in the south, variations do exist in temperature, humidity and precipitation. For example, in summer, some parts of the Rajasthan desert, in north-western India, record temperatures of 50°C, while it may be around 20°C in Pahalgam in Jammu and Kashmir, in the north of the country. On a winter night, the temperature at Drass in Jammu and Kashmir may be as low as minus 45°C, while Thiruvananthapuram may have a temperature of 22°C. In general, coastal areas experience less contrasts in temperature conditions. Seasonal contrasts are more in the interior of the country.
Another case in point is precipitation. While precipitation is mostly in the form of snowfall in the upper parts of the Himalayas, it rains over the rest of the country. The annual precipitation varies from over 400 cm in Meghalaya to less than 10 cm in Ladakh and western Rajasthan. Most parts of the country receive rainfall from June to September, but some parts like the Tamil Nadu coast get most of their rain during October and November.
Question 6:
Discuss the mechanism of monsoons.
Answer:
During summer, a low-pressure area develops over interior Asia as well as over north and north-western India. At the same time, there is a high-pressure system over the southern Indian Ocean. Winds move from a high-pressure area to a low-pressure area. As a result, the low-pressure system attracts the southeast trade winds of the southern hemisphere. On crossing the equator, these trade winds—due to the Coriolis force—turn right towards the low-pressure areas over the Indian subcontinent. After crossing the equator, these winds start blowing in a south-westerly direction, and enter the Indian peninsula as the southwest monsoon. As these winds blow over warm oceans, they bring abundant moisture to the subcontinent. Arriving at the southern tip of the Indian peninsula, the wind system breaks up into two branches − the Arabian Sea branch and the Bay of Bengal branch. The Arabian Sea branch hits the Western Ghats, while the Bay of Bengal branch flows over the Bay of Bengal and hits the eastern Himalayas. The coastal areas west of the Western Ghats receive much of the rainfall from the Arabian Sea Branch, while the regions lying east of the Western Ghats do not receive much rain from these winds. The north-eastern parts of the country receive much of their rainfall from the Bay of Bengal Branch. As these winds move from east to west, the moisture they carry progressively declines. As a result, rainfall decreases from east to west. The Arabian Sea branch moves towards the north-east from the south-west, and joins the Bay of Bengal branch over the northern part of the country. The duration of the monsoon is between 100 to 120 days. By the end of this period, the low pressure system over north and north-west India gradually weakens, and this leads to the retreat of the monsoon winds.
Question 7:
Give an account of weather conditions and characteristics of the cold season.
Answer:
The Cold Weather Season
Beginning from mid-November, the winter season lasts till February. The weather is usually marked by clear sky, low temperatures and low humidity, and feeble and variable winds. The temperature decreases from the south to the north, with the peninsular region not showing any noticeable seasonal change in temperature pattern due to the moderating influence of the sea. The coldest months are December and January. The days are generally warm and the nights are cold. Frost is common in the north and the higher slopes of the Himalayas experience snowfall.
During this season, the sub-tropical westerly jet streams blowing south of the Himalayas bring in cyclonic disturbances from the Mediterranean region. These cause winter rains over the plains and snowfall in the mountains. The Tamil Nadu coast also receives winter rainfall due to the blowing of the north-east trade winds from sea to land.
Question 8:
Give the characteristics and effects of the monsoon rainfall in India.
Answer:
Characteristics of monsoon rainfall in India:
(i) The duration of the monsoon is between 100 to 120 days from early June to mid-September.
(ii) Around the time of its arrival, the normal rainfall increases suddenly and continues for several days. This is known as the ‘burst’ of the monsoon.
(iii) The monsoon has characteristic wet and dry spells or ‘breaks’ in rainfall. The monsoon rains take place only for a few days at a time. They are interspersed with rainless intervals.
(iv) The moisture is carried by pulsating south westerlies that are affected by different atmospheric conditions, thereby giving monsoon rains an uncertain character. The annual rainfall is highly variable from year to year
(v) The rainfall is unevenly distributed across the Indian landscape. Parts of the western coast and north-eastern India receive the maximum rainfall. Regions such as parts of Rajasthan, Gujarat, Leh and the leeward side of the Western Ghats receive very little rainfall.
Effects of monsoon rainfall in India:
(a) Indian agriculture is largely dependent upon the water from the monsoon rains. Late, low or excessive rains have a negative impact upon crops.
(b) Due to the uneven distribution of rainfall across the country, there are some regions that are drought prone and some that are flood afflicted.
(c) The monsoon provides India with a distinct climatic pattern. Hence, in spite of the presence of great regional variations, it has a unifying influence upon the country and its people.
Question 1:
In Table-I the average mean monthly temperatures and amounts of rainfall of ten representative stations have been given. It is for you to study on your own and convert them into ‘temperature and rainfall’ graphs. A glance at these visual representations will help you to grasp instantly the similarities and differences between them. One such graph (Figure 1) is already prepared for you. See if you can arrive at some broad generalisations about our diverse climatic conditions. We hope you are in for a great joy of learning. Do the following activities.
Figure 1: Temperature and Rainfall of Delhi
Answer:
Question 2:
Re-arrange the ten stations in two different sequences:
(i) According to their distance from the equator.
(ii) According to their altitude above mean sea-level.
Answer:
(i) According to their distance from the equator:
Tiruvanantapuram (closest)
Bangalore
Chennai
Mumbai
Nagpur
Kolkata
Shillong
Jodhpur
Delhi
Leh (farthest)
(ii) According to their altitude above mean sea-level:
Kolkata (lowest)
Chennai
Mumbai
Tiruvanatapuram
Delhi
Jodhpur
Nagpur
Bangalore
Shillong
Leh (highest)
Question 3:
(i) Name two rainiest stations.
(ii) Name two driest stations.
(iii) Two stations with most equable climate.
(iv) Two stations with most extreme climate.
(v) Two stations most influenced by the Arabian branch of southwest monsoons.
(vi) Two stations most influenced by the Bay of Bengal branch of south-west monsoons.
(vii) Two stations influenced by both branches of the south-west monsoons
(viii) Two stations influenced by retreating and north-east monsoons.
(ix) Two stations receiving winter showers from the western disturbances.
(x) The two hottest stations in the months of
(a) February (b) April (c) May (d) June
Answer:
(i) Two rainiest stations: Shillong and Mumbai
(ii) Two driest stations: Leh and Jodhpur
(iii) Two stations with most equable climate: Bangalore and Tiruvanantapuram
(iv) Two stations with most extreme climate: Leh and Jodhpur
(v) Two stations most influenced by the Arabian branch of southwest monsoons: Tiruvanatapuram and Mumbai
(vi) Two stations most influenced by the Bay of Bengal branch of south-west monsoons: Shillong and Kolkata
(vii) Two stations influenced by both branches of the south-west monsoons: Delhi and Kolkata
(viii) Two stations influenced by retreating and north-east monsoons: Chennai and Bangalore
(ix) Two stations receiving winter showers from the western disturbances: Jodhpur and Delhi
(x) The two hottest stations −
(a) In the month February: Tiruvanatapuram and Chennai
(b) In the month April: Nagpur and Kolkata
(c) In the month of May: Nagpur and Jodhpur
(d) In the month of June: Jodhpur and Delhi
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Question 4:
Now find out:
(i) Why are Tiruvanantapuram and Shillong rainier in June than in July?
(ii) Why is July rainier in Mumbai than in Tiruvanantapuram?
(iii) Why are south-west monsoons less rainy in Chennai?
(iv) Why is Shillong rainier than Kolkata?
(v) Why is Kolkata rainier in July than in June unlike Shillong which is rainier in June than in July?
(vi) Why does Delhi receive more rain than Jodhpur?
Answer:
(i) The south-west monsoons hit Tiruvanantapuram and Shillong around the first of June. Tiruvanantapuram receives rain from the Arabian Sea branch while Shillong receives rain from the Bay of Bengal branch. After causing rains in these regions, these two branches keep moving on to the other parts of the country (the Arabian Sea Branch moves from south-west to north-east, while the Bay of Bengal branch moves from north-east to north-west). As a result, these regions receive lesser rainfall in the months succeeding June.
(ii) The Arabian Sea branch of the south-west monsoons reaches Tiruvanantapuram around the first of June. It reaches Mumbai around the tenth of June. So, Tiruvanantapuram receives much of its rainfall in the month of June, while Mumbai receives much of its rainfall in the month of July.
(iii) Chennai lies on the leeward side of the Western Ghats, and far away from the western coast. The Arabian Sea branch causes greater rainfall on the western coastline, while the eastern branch passes over Bay of Bengal, on to the north-eastern part of the country. As a result, Chennai gets low rainfall from the south-west monsoons.
(iv) Shillong is enclosed by hills and mountains, which causes the Bay of Bengal branch of the south-west monsoons to accumulate in this region. This is the reason why this region experiences heavy rainfall. On the other hand, Kolkata does not lie in a hilly area. Thus, it receives lesser rainfall as compared to Shillong.
(v) The Bay of Bengal branch of the south-west monsoons reaches Shillong around the first of June. It gradually progresses from east to west. As a result, the amount of rainfall received by this region decreases from June to July. The monsoon winds reach Kolkata later than they arrive in Shillong. Hence, Kolkata receives more rainfall in July.
(vi) Due to the progressive decrease in the humidity of the monsoon winds, the amount of rainfall decreases from east to west in northern India. Delhi lies to the east of Jodhpur. Hence, the former receives more rain than the latter.
Question 5:
Now think why
— Tiruvananthapuram has equable climate?
— Chennai has more rains only after the fury of monsoon is over in most parts of the country?
— Jodhpur has a hot desert type of climate?
— Leh has moderate precipitation almost throughout the year?
— While in Delhi and Jodhpur most of the rain is confined to nearly three months, in
Tiruvanantapuram and Shillong it is almost nine months of the year?
In spite of these facts see carefully if there are strong evidences to conclude that the monsoons still provide a very strong framework lending overall climatic unity to the whole country.
Answer:
Tiruvanantapuram has an equable climate because of its proximity to the sea. The sea exerts a moderating influence on the climate of the region.
For most parts of the country, the months of October to November form a period of transition from hot rainy season to dry winter conditions. However, Chennai experiences a lot of rainfall during this period because of the retreating monsoons, and also because of the tropical cyclones.
Jodhpur lies in the north-western part of the country. The Great Indian Desert is located in this region. Due to the presence of sand, the region experiences high diurnal range of temperature. Hence, Jodhpur has a hot desert type of climate.
While it receives scanty rainfall throughout the year, Leh does experience snowfall due to the extremely low temperatures. As a result, it experiences moderate precipitation almost throughout the year.
Being located in the interior parts of the country, Delhi and Jodhpur receive rainfall mostly from the south-west monsoons. Hence, the rains in these regions are confined to the monsoon period. While Tiruvanantapuram and Shillong do receive heavy rains during the monsoons, their proximity to the sea makes them experience rains apart from the ones received during the monsoon period.
Though factors like wind systems, pressure, latitude, altitude, distance from the sea, presence of mountains, etc., are responsible for the presence of variations across the country, the seasonal arrival and retreat of monsoons provides a kind of climatic unity to the entire country. In spite of the differences, a distinct climatic pattern is evident—a climate characterised by hot rainy summers and cold dry winters.