Climate

Find Out 1

Question 1

Why the houses in Rajasthan have thick walls and flat roofs?

Answer

Houses in Rajasthan have thick walls in order to create insulation from the outer extreme climate. It keeps the house cool during day and warm during nights. Roofs are flat in order to collect rain water.

Question 2

Why is it that the houses in the Tarai region and in Goa and Mangalore have sloping roofs?

Answer

The houses in the Tarai region and in Goa and Mangalore have sloping roofs because the area receives very high rainfall and sloping roof helps in easy and quick drainage.

Question 3

Why houses in Assam are built on stilts?

Answer

Houses in Assam are built on stilts to protect against annual monsoon floods caused by heavy rainfall and the Brahmaputra River. Stilts lift the houses above floodwater, keeping people and belongings dry while letting water pass below harmlessly.

Find Out 2

Question 1

Why most of the world's deserts are located in the western margins of continents in the subtropics?

Answer

Most of the world's deserts are on the western sides of continents in the subtropics because the prevailing tropical easterly winds lose their moisture as they move westward, resulting in dry conditions and little rainfall on the western margins.

Choose the right answer

Question 1(i)

Which one of the following places receives the highest rainfall in the world?

1. Silchar
2. Mawsynram
3. Cherrapunji
4. Guwahati

Answer

Mawsynram

Question 1(ii)

The wind blowing in the northern plains in summers is known as:

1. Kaal Baisakhi
2. Loo
3. Trade Winds
4. None of the above

Answer

Loo

Question 1(iii)

Monsoon arrives in India approximately in:

1. Early May
2. Early July
3. Early June
4. Early August

Answer

Early June

Question 1(iv)

Which one of the following characterises the cold weather season in India?

1. Warm days and warm nights
2. Warm days and cold nights
3. Cool days and cold nights
4. Cold days and warm nights

Answer

Warm days and cold nights

Answer the following questions briefly

Question 2(i)

What are the controls affecting the climate of India?

Answer

The controls affecting the climate of India are:

1. Latitude.
2. Altitude.
3. Pressure and wind system.
4. Distance from the sea.
5. Ocean currents.
6. Relief features.

Question 2(ii)

Why does India have a monsoon type of climate?

Answer

India has a monsoon type of climate primarily because it is located in the tropical and subtropical regions of the Northern Hemisphere and it's climate is strongly influenced by monsoon winds, which provide a rhythmic cycle of seasons, typical of Monsoon climate.

Question 2(iii)

Which part of India does experience the highest diurnal range of temperature and why?

Answer

Thar desert has the highest diurnal range of temperature with daytime highs around 50°C and nighttime lows of 15°C. This is due to the rapid heating and cooling of its sand and its inland location far away from the moderating influence of the sea.

Question 2(iv)

Which winds account for rainfall along the Malabar coast?

Answer

South-west monsoon winds bring rains along Malabar coast.

Question 2(v)

Define monsoons. What do you understand by "break" in monsoon?

Answer

Monsoon are periodic or seasonal reversing winds. They are divided into two wind systems — the Summer Monsoon that blow south-west and the Winter Monsoon that blow north-east.

The Monsoon has wet and dry spells. Monsoon rains take place only for a few days at a time. They are interspersed with rainless intervals that are referred to as 'break' in monsoon.

Question 2(vi)

Why is the monsoon considered a unifying bond?

Answer

The monsoon is considered a unifying bond because:

1. Monsoon winds are associated with the rhythmic cycle of seasons.
2. The entire agricultural calender of the whole country depends on monsoon.
3. Life of people and festivities revolve around monsoon.
4. The river valleys which carry the water of monsoon also unite as a single river valley unit.
5. People from north to south and east to west, eagerly await the arrival of the monsoon.
6. Unifying influence of the monsoon on the Indian subcontinent is quite perceptible.

Answer the following questions

Question 3

Why does the rainfall decrease from the east to the west in Northern India.

Answer

The Bay of Bengal branch of the monsoon which enters India from the northeastern side, gradually sheds its moisture as it advances westward. By the time it reaches the northwestern part of India, it doesn't have much moisture left. Hence, rainfall decreases from the east to the west in Northern India.

Question 4(i)

Give reasons as to why seasonal reversal of wind direction takes place over the Indian subcontinent?

Answer

During summers, the Northern plains are heated up and low pressure is created over the Indian mainland. This low pressure attracts the trade winds of the southern hemisphere which bring the monsoon rains. During October-November, with the apparent movement of the sun towards south, the low pressure trough over northern plain becomes weaker. It is gradually replaced by high pressure system. This cause reversal of wind direction over the Indian subcontinent.

Question 4(ii)

Give reasons as to why the bulk of rainfall in India is concentrated over a few months.

Answer

India receives the majority of its rainfall from the south-west monsoon winds, which typically last for a duration of 100 to 120 days. As a result, the country experiences a concentrated period of heavy rainfall over a few months.

Question 4(iii)

Give reasons as to why the Tamil Nadu coast receives winter rainfall.

Answer

During winter the dry offshore northeast monsoon winds blow from high pressure to low pressure. As they cross the Bay of Bengal, they gather enough moisture. When these winds reach the Coromandel coast in eastern India, they bring heavy rainfall to Tamil Nadu.

Question 4(iv)

Give reasons as to why the delta region of the eastern coast is frequently struck by cyclones.

Answer

During October-November the low-pressure conditions, over north-western India, get transferred to the Bay of Bengal. This shift is associated with the occurrence of cyclonic depression. Therefore, the delta region of the eastern coast is frequently struck by cyclones.

Question 4(v)

Give reasons as to why parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone.

Answer

Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone due to the following reasons:

1. The Arabian sea branch of the monsoon enters the Indian subcontinent from the western coast and brings heavy rainfall on windward side of Western Ghats. The leeward side gets very little rainfall as it falls in rain shadow area.
2. The Bay of Bengal branch of the monsoon gradually sheds its moisture as it moves from east to west. By the time it reaches Rajasthan and Gujarat which are located in the northwestern part of the country, it doesn't have much moisture left to cause adequate rainfall.
3. The Aravallis do not obstruct the Monsoon winds due to their parallel alignment to the winds and low heights of Aravallis.

Question 5

Describe the regional variations in the climatic conditions of India with the help of suitable examples.

Answer

There are great regional variations in India's climate which are explained with the help of some examples below:

1. In summer, temperatures can occasionally reach 50°C in some parts of the Rajasthan desert but are around 20°C in Pahalgam, Jammu and Kashmir.
2. On a winter night, temperature at Drass in Jammu and Kashmir may fall to -45°C while Thiruvananthapuram stays at a mild 22°C.
3. Coastal areas experience less contrasts in temperature conditions. Seasonal contrasts are more in the interior of the country.
4. Precipitation mostly takes the form of snowfall in the upper Himalayan regions, while the rest of the country experiences rainfall.
5. The annual precipitation varies from over 400 cm in Meghalaya to less than 10 cm in Ladakh and western Rajasthan.
6. Most of the country gets rainfall from June to September, but the Tamil Nadu coast receives most rainfall in October and November.

Question 6

Give an account of weather conditions and characteristics of the cold season.

Answer

1. The cold weather season begins from mid-November in northern India and stays till February. December and January are the coldest months in the northern part of India.
2. The temperature is higher (24-25°C) in peninsular India but lower (10-15°C) in North India.
3. Days are warm and night are cold. Frost is common in north and the higher slopes of Himalayas experience snowfall.
4. Winters are dry because, the northeast trade winds prevail over the country which blows from land to sea.
5. Tamil Nadu gets rainfall in winters as here the northeast trade winds blow from sea to land.
6. The northern plain is characterized by cyclonic western disturbances and winter rainfall. These rains are locally known as mahawat and are very important for rabi crops.
7. The peninsular region does not have a well defined cold season as the moderating influence of the sea keeps the temperature patterns relatively stable throughout the year.

Question 7

Give the characteristics and effects of the monsoon rainfall in India.

Answer

Characteristics of monsoon rainfall in India:

1. The duration of monsoon is 100-120 days from first week of June to mid september.
2. Monsoon rainfall occurs in wet and dry spells taking place only for a few days at a time. They are interspersed with rainless intervals.
3. The rainfall is unevenly distributed throughout the country. The western coast, northeastern states, and the Himalayan foothills receive more rainfall, while the northwestern (Rajasthan and parts of Gujarat) and central parts (interior of Deccan plateau and parts of Madhya Pradesh) of India receive relatively less rainfall.
4. Monsoon winds are seasonal and influenced by various atmospheric conditions. This gives them an uncertain character. The annual rainfall is highly variable from year to year.

Effects of monsoon rainfall in India:

1. The inflow of south east monsoon bring about total change in weather of the country. There is relief from scorching hot summers.
2. The Indian agricultural heavily relies on the monsoon. Adequate rainfall is crucial for the cultivation of crops such as rice, wheat, sugarcane, cotton, and pulses. A deficient monsoon can lead to droughts, crop failures, and food shortages.
3. Its uneven nature brings flood in some places and results in drought in other places.
4. The monsoon rainfall replenishes India's water resources, including rivers, reservoirs, and groundwater aquifers.

For Doing it Yourself

Question 1

In Table-I, the average mean monthly temperatures and amounts of rainfall of 10 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 I) 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

(2) Re-arrange the 10 stations in two different sequences:

(i) According to their distance from the equator.

(ii) According to their altitude above mean sea level.

(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 influenced by retreating monsoons.

(vi) The two hottest stations in the months of:
      (a) February
      (b) April
      (c) May
      (d) June

(4) Now find out

(i) Why are Thiruvananthapuram and Shillong rainier in June than in July?

(ii) Why is July rainier in Mumbai than in Thiruvananthapuram ?

(iii) Why are southwest 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?

(5) Now think why

• Thiruvananthapuram 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 Thiruvananthapuram 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

(1) The temperature and rainfall graphs for stations are shown below:

(2) The re-arranged stations:

(i) According to increasing order of their distance from the equator:

Thiruvananthapuram → Bangalore → Chennai → Mumbai → Nagpur → Kolkata → Shillong → Jodhpur → Delhi → Leh

(ii) According to increasing order of their altitude above mean sea level.

Kolkata → Chennai → Mumbai → Thiruvananthapuram → Delhi → Jodhpur → Nagpur → Bengaluru → Shillong → Leh

(3)

(i) Two rainiest stations — Shillong, Mumbai

(ii) Two driest stations — Leh, Jodhpur

(iii) Two stations with most equable climate — Mumbai, Kolkata

(iv) Two stations with most extreme climate — Leh, Jodhpur

(v) Two stations influenced by retreating monsoons — Chennai, Bengaluru

(vi) The two hottest stations in the months of:
      (a) February — Thiruvananthapuram, Chennai
      (b) April — Nagpur, Chennai
      (c) May — Nagpur, Jodhpur
      (d) June — Delhi, Jodhpur

(4)

(i) Thiruvananthapuram receives rainfall from the Arabian sea branch of the monsoon and Shillong receives rainfall from the Bay of Bengal branch of the monsoon in first week of June. Later these branches move ahead and these places receive less rainfall in July.

(ii) The Arabian sea branch hits Thiruvananthapuram on 1 June while it reaches Mumbai on 10 June. So, Thiruvananthapuram receives most of the rainfall in June but Mumbai gets most of rainfall in July.

(iii) The southwest monsoons has two branches: the Arabian sea branch and the Bay of Bengal branch. The Arabian sea branch brings rainfall on western Ghats. Chennai is situated on the leeward side of Western ghats and therefore get very less rainfall. The Bay of Bengal branch moves towards north-eastern states and bring heavy rainfall. Therefore, southwest monsoons are less rainy in Chennai.

(iv) Due to lofty Himalayas, the monsoon wind do not escape and remains near Shillong bringing heavy rainfall there. Therefore, Shillong is rainier than Kolkata.

(v) The Bay of Bengal branch of Monsoon reaches Shillong earlier than Kolkata. Therefore, Kolkata rainier in July than in June unlike Shillong which is rainier in June than in July.

(vi) Jodhpur is located to the west of Delhi. As the monsoon winds traverse Northern India from east to west, they gradually shed their moisture. Hence, when these winds reach Delhi, they retain more moisture and result in greater rainfall compared to Jodhpur.

(5)

• Thiruvananthapuram has equable climate because it is situated near sea which has a moderating effect on its climate.

• Chennai does not get rainfall from Southwest monsoons during June to september. It gets its share of rainfall from retreating monsoon and prevalent northwest trade winds that bring moisture from Bay of Bengal during October-November.

• Jodhpur is situated in Thar desert. This area gets very less rainfall. The sand is heated up quickly during day and increases the temperature. Therefore, Jodhpur has a hot desert type of climate.

• Leh has moderate precipitation almost throughout the year because it is situated on landlocked plateau and the place is dry due to low temperature.

• Delhi and Jodhpur get rainfall mostly from monsoon and some from western disturbances. Thiruvananthapuram receives rainfall from monsoon as well as from local factors as it is situated near sea. Shillong is surrounded by lofty mountains that do not allow the rain bringing winds from Bay of Bengal to escape. Therefore, while in Delhi and Jodhpur most of the rain is confined to nearly three months, in Thiruvananthapuram and Shillong it is almost nine months of the year.

In spite of the above facts, we can say that monsoon unifies India as one because monsoon brings rainfall to most of India from north to south in span of 2-3 months. All the festivals and agricultural practices revolve around the monsoon rains.