NCERT Solutions Class 9 Geography Chapter – Climate: The climate of India is monsoon type and various factors are responsible for onset and advancement of monsoon in India. Solutions of the chapter ‘Climate’ Class 9 are given below.
NCERT Solutions for Class 9 Social Science Geography Chapter 4 Climate
Find Out: Page No: 27
1. Find out why the houses in Rajasthan have thick walls and flat roofs.
Houses in Rajasthan have thick walls and flat roofs. The thick walls do not allow the heat to get into the houses while the flat roofs help to retain the little water that comes as rain in the desert.
2. Find out why is it that the houses in the Tarai region and in Goa and Mangalore have sloping roofs.
The Tarai region, Goa and Mangalore receive heavy rains during monsoon seasons thus the houses have sloping roofs so that the rainwater flows off the roof.
3. Why are houses in Assam built on stilts?
The houses are built on stilts in Assam as there is danger of floods and wild animals in large areas of Assam.
4. 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 located in the western margins of continents in the subtropics because trade winds that blow in the region shed their moisture on the eastern side.They become dry by the time they reach the western margin of the continent. Cold ocean currents also tend to stabilise the air over the coast and inhibit cloud formation.
Exercises: Page No: 39
Q.1. Choose the correct answer from the four alternatives given below.
(i) Which one of the following places receives the highest rainfall in the world?
(ii) The wind blowing in the northern plains in summers is known as:
(a) Kaal Baisakhi
(c) Trade Winds
(d) None of the above
(iii) Which one of the following causes rainfall during winters in north-western part of India,
(a) Cyclonic depression
(b) Retreating monsoon
(c) Western disturbances
(d) Southwest monsoon
(c) Western disturbances
(iv) Monsoon arrives in India approximately in:
(a) Early May
(b) Early July
(c) Early June
(d) Early August
(c) Early June
(v) Which one of the following characterises 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
(c) Cool days and cold nights
Q.2. Answer the following questions briefly.
(i) What are the factors affecting the climate of India?
The factors controlling the climate of India are:
- Pressure and winds (jet streams)
- Distance from the sea
- Relief or mountains
(ii) Why does India have a monsoon type of climate?
India has a monsoon type of climate because of the strong influence of the monsoon winds over the sub-continent. The summer monsoons cause heavy rainfall when they blow from sea to land. The winter monsoon winds blow from the interior of the continent to the sea and do not cause much rain. There is a seasonal reversal of the wind system ‘monsoon’.
(iii) Which part of India does experience the highest diurnal range of temperature and why?
The Thar desert experiences the highest diurnal range of temperature. This is because during the day the temperature rises to over 50°C, and at night due to the absence of the sun and lack vegetation the temperature drops to below 15°C the same night.
(iv) Which winds account for rainfall along the Malabar Coast?
Arabian Sea Branch of the South West summer Monsoons.
(v) What are jet streams and how do they affect the climate of India?
Jet streams are high velocity westerly winds blowing through a narrow zone in the upper troposphere. The westerly flows are responsible for the western disturbances experienced in the north and north-western parts of the country. The easterly jet streams cause tropical depressions during the monsoon as well as October-November months.
(vi) Define monsoons. What do you understand by “break” in monsoon?
The word monsoon has been derived from the Arabic word ‘mausim’ which means season. In this season the winds blow from land to sea for 6 months and from sea to land for 6 months. The break in the monsoon rainfall refers to the dry spells when the monsoon rain takes place
only for a few days at a time. These breaks are related to the movement of the monsoon trough. When the axis of the monsoon trough lies over the plains, then the rainfall is heavier there. When the trough moves towards the Himalayas, the plains are dry but there is heavy rainfall occur over the mountains.
(vii) Why is the monsoon considered a unifying bond?
The monsoon is considered a unifying bond because:
- The Indian landscape, its flora and fauna, etc. are highly influenced by the monsoon.
- These monsoon winds bind the whole country by providing water for agricultural activities
- Most of the festivals in India that are related to agricultural cycle may be known by different names in different parts of the country, but their celebration is decided by the monsoon.
- Year after year, people of India from north to south and from east to west, eagerly await the arrival of the monsoon. The river valleys which carry this water also unite as a single river valley unit.
Q.3. Why does the rainfall decrease from the east to the west in Northern India?
The Bay of Bengal branch of south-west monsoon moves towards northeast carrying more moisture and they give heavy rainfall in this region. As they move further towards west, they carry less moisture content with themselves resulting in decrease in rainfall in the west.
Q.4. Give reasons as to why:
(i) Seasonal reversal of wind direction takes place over the Indian subcontinent?
Land and water are of different densities, so the rate of heating and cooling varies. The Indian subcontinent is surrounded by water on three sides. In summer the land mass of India is warmer than the surrounding sea, therefore there is low pressure. The sea is cooler, thereby having higher pressure. So the winds blow from sea to land.
In winter the land has high pressure while the sea has low pressure. Therefore, the winds blow towards the sea. Thus a seasonal reversal of wind direction takes place.
(ii) The bulk of rainfall in India is concentrated over a few months.
In India the bulk of the rainfall is concentrated over a few months. The main source of rainfall is the monsoon wind which blows when there is intense low pressure on the land. The surrounding waterbody is cool and has high pressure. This ideal temperature and pressure are caused in May, when the rain falls between June – September and it becomes cooler (high pressure). Rest of the year is practically dry.
(iii) The Tamil Nadu coast receives winter rainfall winds.
During the winter season the Tamil Nadu coast receives rain from the north east Monsoon which blow from land to sea. They do not cause any rain in the northern part of the country. But while crossing the Bay of Bengal they pick up moisture-and cause rain on the eastern coast of south India, mainly the Tamil Nadu coast.
(iv) The delta region of the eastern coast is frequently struck by cyclones.
The delta region of the eastern coast is frequently struck by cyclones as the low-pressure conditions over north western India get transferred to the Bay the Bengal by early November. This shift is responsible for the occurrence of cyclonic depressions which originate over the Andaman sea. These then cross the eastern coast causing heavy widespread rain leading to great damage to life and property.
(v) Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone.
Relief/Mountains play an important role in the distribution of rainfall in India. The moisture laden winds (South West Monsoons) cause heavy rain on the windward slopes of the Western Ghats and Khasi-Garo hills. As the winds cross over to the leeward slopes, there is less rainfall as most of it has been deposited on the slope facing the winds. All the area on the leeward side is deprived of rain and is drought prone. Rajasthan also lies in the rain shadow of the Aravalli hills.
Q.5. Describe the regional variations in the climatic conditions of India with the help of suitable examples.
The great regional variations in the climatic conditions of India are seen mainly in temperature and rainfall.
Temperature: In summer the temperature rises above 50° Cin some parts of Rajasthan while in Jammu and Kashmir it may be around 20 C at the same time. During winter the temperature goes down to even minus 45 C while it may be around 22 c in the Thiruvananthapuram.
Coastal areas have a moderate climate while the interior of India has extreme or continental climate.
Precipitation: The rainfall is as high as 400cm in in Meghalaya while it is less than 10 cm in W. Rajasthan and Ladakh. Most part of India gets rainfall between June to September while Tamil Nadu receives rainfall between November and December.
Q.6. Discuss the mechanism of monsoons.
Following are the factors responsible for the mechanism of monsoon:
- The differential heating and cooling of land and water creates low pressure on the landmass of India while the seas around experience comparatively high pressure.
- The Inter Tropical Convergence Zone (ITCZ) is normally positioned about 5°N of the equator. It shifts over the Ganga plains during summer. It is also known as the monsoon trough during the monsoon season.
- The high-pressure area, east of Madagascar is approximately 20°S over the Indian Ocean. This area affects the Indian Monsoon.
- The Tibetan plateau gets intensely heated during summer. This results in strong vertical air currents and formation of high pressure over the plateau. This high-pressure zone is about 9 km above the sea level.
- The westerly jet stream moves to the north of the Himalayas, and the tropical easterly jet stream moves over the Indian Peninsula during summer.
- The periodic change in pressure conditions between Pacific Ocean and the Indian Ocean that is known as the Southern Oscillation or SO also affects the monsoon.
- The difference in pressure over Tahiti and Darwin is computed to predict the intensity of the monsoons. Tahiti (18°S/149°W) lies in the Pacific Ocean and Darwin (12°30’S/131°E) lies in northern Australia. If the pressure differences are negative, it means a below average and late monsoon
Q.7. Give an account of weather conditions and characteristics of the cold season.
During the cold season, the skies are clear, temperatures and humidity are low and the winds are feeble and variable.
The temperature is higher in the south due to the moderating influence of the sea but decreases as one goes northwards where it ranges between 10° and 15° Celsius. Frost is common in the north and there is snowfall in the higher slopes of the Himalayas. Winds blow from land to sea and are dry except when they pick up moisture from the Bay of Bengal and cause rainfall in Tamil Nadu.
A characteristic feature of the cold weather season is the low-pressure system which enters northwest India from the Mediterranean Sea. These are also known as the temperate or westerly depression cyclones and cause winter rain and snowfall in the hills/mountains. This rain is beneficial for the growth of ‘Rabi’ crops.
Q.8. Give the characteristics and effects of the monsoon rainfall in India.
Characteristics of the monsoon rainfall in India:
- The duration of the monsoon varies from 100 to 120 days from early June to mid- September.
- Around the time of its arrival, the normal rainfall increase suddenly and continues regularly for several days. This is called the ‘burst’ of the monsoon.
- They are distinguished from the pre-monsoon showers because of their increase in rainfall amount and regularity.
- The monsoon arrives at the southern tip of the Indian Peninsular generally by the first week of June.
- The rainfall is unevenly distributed across the country.
Effects of the monsoon rainfall in India:
- Agriculture in India largely depends on Indian monsoons for water. Late, Low or excessive rains have a negative impact on crops.
- Due to uneven distribution of rainfall across the country, there are few places that are drought prone and few are flood affected.
- The monsoon provides India with a diverse climatic pattern. Hence, in spite of the presence of great regional variations, it has a unifying influence upon the country and its people.
Q.9. On an outline map of India, show the following.
(i) Areas receiving rainfall over 400 cm.
(ii) Areas receiving less than 20 cm of rainfall.
(iii) The direction of the South-West Monsoon over India.