In-text Questions
Why the houses in Rajasthan have thick walls and flat roofs?
Houses in Rajasthan have thick walls to keep the inside of the house cool during the very hot days. The thick walls stop the sun’s heat from getting in. They have flat roofs because Rajasthan gets very little rain, so there is no need for a sloping roof to drain water. People can also use the flat roofs to sleep outside at night when it gets cooler.
Why is it that the houses in the Tarai region and in Goa and Mangalore have sloping roofs?
The Tarai region, Goa, and Mangalore are all places that receive very heavy rainfall. Houses there have sloping roofs so that the rainwater can flow down and drain away quickly. This prevents water from collecting on the roof, which could cause leaks and damage the house.
Why houses in Assam are built on stilts?
Assam is a state that gets a lot of rain and often has floods. To protect the houses from floodwater and the damp ground, they are built on stilts (strong posts that raise the house above the ground). This keeps the house and the people inside safe and dry.
Why most of the world’s deserts are located in the western margins of continents in the subtropics?
Most of the world’s deserts are found on the western side of continents for a couple of reasons. Firstly, the winds that blow in these areas often travel over land and do not carry much moisture. Secondly, there are often cold ocean currents flowing along these western coasts. These currents cool the air and prevent clouds and rain from forming, leading to dry, desert conditions.
Activity (Based on News Reports)
(i) On the basis of the news items above, find out the names of places and the seasons described.
- Delhi: The reports describe a cold winter with fog and also a hint of an early summer as temperatures rise.
- Chennai (Tamil Nadu): The report describes heavy rains and floods between October and December, which is the retreating monsoon or post-monsoon season.
- Mumbai: The report describes extremely heavy rainfall on July 26, which is during the advancing monsoon or rainy season.
- Srinagar / Kashmir: The reports describe a harsh winter with heavy snowfall and sub-zero temperatures.
- Shimla: The report describes a cold winter with heavy snow.
- Amritsar & Rajasthan: These places are described as being extremely cold, which is during the winter season.
(ii) Compare the rainfall description of Chennai and Mumbai and explain the reasons for the difference.
Mumbai gets its heavy rainfall during the main monsoon season, around July. This is because the Southwest Monsoon winds from the Arabian Sea hit the coast directly and cause heavy rains.
Chennai, on the other hand, gets most of its rainfall later in the year, from October to December. This is because Chennai gets its rain from the Retreating Monsoon (or Northeast Monsoon). During this time, winds blow over the Bay of Bengal, pick up moisture, and bring rain to the eastern coast where Chennai is located.
So, they get rain from two different monsoon systems at different times of the year.
(iii) Evaluate flood as a disaster with the help of a case study.
Floods are a very serious disaster, and the news report about the Mumbai floods on July 26, 2005, is a good case study. On that day, the city received over 944 mm (about 3 feet) of rain in just 24 hours. The effects were devastating:
- Over 400 people lost their lives.
- Transport systems like buses and trains stopped working.
- There was no electricity in many parts of the city.
- Many areas were completely flooded, forcing people to leave their homes.
This example shows that floods can cause a great loss of life and property and can bring a huge city to a complete standstill, showing how dangerous a disaster it is.
EXERCISE
1. Choose the correct answer.
- Which one of the following places receives the highest rainfall in the world? (b) Mawsynram
- The wind blowing in the northern plains in summers is known as: (b) Loo
- Monsoon arrives in India approximately in: (c) Early June
- Which one of the following characterises the cold weather season in India? (b) Warm days and cold nights
2. Answer the following questions briefly.
(i) What are the controls affecting the climate of India?
The six major factors that control the climate of India are:
- Latitude
- Altitude (height above sea level)
- Pressure and wind system
- Distance from the sea
- Ocean currents
- Relief features (like mountains)
(ii) Why does India have a monsoon type of climate?
India has a monsoon type of climate because of the complete change (reversal) in the direction of winds during the year. In winter, winds blow from the cool land to the warmer sea. In summer, the land gets much hotter than the sea, causing the winds to reverse and blow from the sea to the land. These summer winds, called the Southwest Monsoon, are full of moisture and bring rain to most of India.
(iii) Which part of India does experience the highest diurnal range of temperature and why?
The northwestern part of India, especially the Thar Desert in Rajasthan, experiences the highest diurnal range of temperature. This means there is a very big difference between the day and night temperatures. This happens because sand in the desert heats up very quickly during the day (up to 50°C) and cools down very quickly at night (down to 15°C). Also, this region is far away from the sea, so it does not experience the moderating effect of sea breezes.
(iv) Which winds account for rainfall along the Malabar coast?
The Southwest Monsoon winds from the Arabian Sea are responsible for the heavy rainfall along the Malabar coast (the coast of Kerala).
(v) Define monsoons. What do you understand by “break” in monsoon?
- Monsoon: A monsoon is a seasonal reversal in the wind direction over a large area that happens during a year.
- “Break” in monsoon: This refers to the period during the rainy season when the monsoon rains stop for a few days or a week, creating a dry spell, before they start again. So, the rainy season has both wet spells and rainless breaks.
(vi) Why is the monsoon considered a unifying bond?
The monsoon is considered a unifying bond for the whole country because:
- The entire country, from north to south, is connected by its dependence on monsoon rains for farming.
- The life of the people, their agricultural activities, and even their festivals revolve around the cycle of the monsoon.
- People all over India eagerly wait for the monsoon’s arrival every year.
- The rivers, filled with monsoon water, flow across states and also unite the country.
3. Why does the rainfall decrease from the east to the west in Northern India?
The Bay of Bengal branch of the monsoon winds enters Northern India from the east. As these winds travel westwards over the Ganga plains, they continuously release moisture in the form of rain. By the time they reach the western parts like Punjab, Haryana, and Rajasthan, they have already lost most of their moisture. Therefore, the amount of rainfall decreases as the winds move from east to west.
4. Give reasons as to why.
(i) Seasonal reversal of wind direction takes place over the Indian subcontinent?
This happens because of the difference in heating of land and water. In summer, the land in and around India gets very hot, creating a low-pressure area. The sea remains cooler, creating a high-pressure area. So, winds blow from the high-pressure sea to the low-pressure land. In winter, this reverses. The land becomes very cold (high pressure) while the sea is warmer (low pressure), so winds blow from land to sea.
(ii) The bulk of rainfall in India is concentrated over a few months.
Most of the rainfall in India comes from the Southwest Monsoon winds. These winds blow only for a few months, mainly from June to September. During the rest of the year, the winds are either dry or blow from the land towards the sea, so there is very little rain.
(iii) The Tamil Nadu coast receives winter rainfall.
In winter, the dry Northeast winds start blowing. When these winds pass over the Bay of Bengal, they pick up moisture. These moisture-filled winds then strike the Tamil Nadu coast, causing rainfall there during the winter months.
(iv) The delta region of the eastern coast is frequently struck by cyclones.
During October and November, the low-pressure conditions over the land shift to the Bay of Bengal. This condition helps in the formation of powerful cyclonic storms over the Andaman Sea. These storms then move towards the eastern coast of India and often strike the delta regions of rivers like the Godavari, Krishna, and Kaveri.
(v) Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone.
Rajasthan and Gujarat: These areas receive very little rain because the Arabian Sea branch of the monsoon flows parallel to the Aravalli hills and does not get blocked to cause rain. The Bay of Bengal branch has lost most of its moisture by the time it reaches this far west.
Leeward side of Western Ghats: This area lies in the “rain shadow”. The monsoon winds from the Arabian Sea are forced to rise by the high Western Ghats, causing heavy rain on the windward (western) side. After crossing the mountains, the winds descend on the leeward (eastern) side, become dry, and cause very little rain.
5. Describe the regional variations in the climatic conditions of India with the help of suitable examples.
India has large variations in its climatic conditions from region to region.
- Temperature Variations: In summer, the temperature in the Rajasthan desert can reach 50°C, while in Pahalgam (Kashmir) it is only around 20°C. In winter, Drass (Ladakh) can be as cold as -45°C, while Thiruvananthapuram (Kerala) has a comfortable temperature of 22°C.
- Precipitation Variations: Precipitation in the upper Himalayas is in the form of snowfall, while the rest of the country receives rain. Mawsynram in Meghalaya gets over 400 cm of rainfall annually, whereas Ladakh and western Rajasthan get less than 10 cm. Most of the country gets rain between June and September, but the Tamil Nadu coast gets most of its rain during October and November.
6. Give an account of weather conditions and characteristics of the cold season.
The cold weather season, or winter, in India lasts from mid-November to February.
- Temperature: Temperatures are generally low, especially in the north. The average temperature in the northern plains is between 10°C and 15°C. Days are usually warm, and nights are cold.
- Weather: The sky is normally clear, and the weather is pleasant with low humidity. Frost is common in the north.
- Winds: The Northeast trade winds blow from land to sea, so it is a dry season for most of the country.
- Rainfall: Some parts of the country get winter rain. The Tamil Nadu coast gets rain from the Northeast monsoon. The northern plains get some rain, locally called ‘mahawat’, from western cyclonic disturbances, which is very good for rabi crops like wheat.
7. Give the characteristics and effects of the monsoon rainfall in India.
Characteristics:
- Monsoon rains are concentrated in a few months, from June to September.
- The rainfall is unevenly distributed, with some places getting very heavy rain and others getting very little.
- The monsoon often has ‘breaks’, which are dry spells in between periods of rain.
- Its arrival and retreat can be irregular, sometimes coming early and sometimes late.
Effects:
- Positive Effects: The monsoon provides water for agriculture, which is the main occupation for a majority of Indians. It recharges rivers and groundwater. It also provides relief from the intense summer heat.
- Negative Effects: Due to its uncertain nature, the monsoon can cause problems. Very heavy rains can lead to devastating floods, while very little rain can lead to droughts. This uncertainty affects the farming schedule and the lives of millions of farmers.
MAP SKILLS
On an outline map of India, show the following.
- Areas receiving rainfall over 400 cm.
Answer: On the map, you should shade the western coastal strip (along the Western Ghats) and parts of Northeast India (especially Meghalaya). - Areas receiving less than 20 cm of rainfall.
Answer: On the map, you should shade the region of Ladakh in the north and the Thar Desert area in western Rajasthan. - The direction of the south-west monsoon over India.
Answer: You should draw arrows to show the winds.- Draw arrows coming from the southwest over the Arabian Sea and hitting the west coast of India.
- Draw another set of arrows coming from the Bay of Bengal, curving towards the northeast, and then moving westwards over the northern plains of India.