Class 9 Social Science (Contemporary India) Chapter 4 Climate

Key Concept: Climate vs Weather

a) Time duration

[Solution Description] Weather refers to short-term atmospheric conditions, such as daily changes in temperature and precipitation. Climate, on the other hand, refers to long-term patterns and averages of weather over extended periods, typically 30 years or more.

Key Concept: Definition of Climate

c) The sum total of weather conditions over a large area for a long period

[Solution Description]

Climate refers to the sum total of weather conditions and variations over a large area for a long period of time, typically more than thirty years. This includes patterns such as temperature, atmospheric pressure, wind, humidity, and precipitation.

Key Concept: Duration of Climate

d) Thirty years

[Solution Description]

Climate is defined as the sum total of weather conditions and variations over a large area for a long period of time, specifically more than thirty years.

Key Concept: Weather vs. Climate

c) Weather is short-term, climate is long-term

[Solution Description]

Weather refers to the state of the atmosphere over an area at any point of time, while climate refers to the sum total of weather conditions and variations over a large area for a long period of time (more than thirty years). Therefore, the correct answer is the option that states that climate is concerned with long-term patterns, while weather deals with short-term conditions.

Key Concept: Monsoon Climate

c) Arabic

[Solution Description]

The word “monsoon” is derived from the Arabic word  “mausim”, which literally means season.

Key Concept: Pressure and Winds, Monsoon

b) The heating and cooling of land and ocean create pressure differences.

[Solution Description] The monsoon is caused by the seasonal shift in the position of the subtropical high-pressure belt of the northern hemisphere. During summer, the land heats up faster than the ocean, creating a low-pressure zone over the Indian subcontinent. This draws moist winds from the Indian Ocean, leading to the southwest monsoon. In winter, the situation reverses, with high pressure over land causing dry northeast winds. This shift in wind direction is a key feature of India’s climate.

Key Concept: Seasonal contrasts, Coastal vs Interior regions

c) 15°C

[Solution Description]

Calculate the seasonal temperature range for the interior region: $30 – 10 = 20$°C. For the coastal area, the range is $25 – 20 = 5$°C. The difference in seasonal temperature range is $20 – 5 = 15$°C.

Key Concept: Pressure and Wind System, Relief Features

c) Rain shadow effect caused by mountains

[Solution Description]

The phenomenon described is known as the rain shadow effect. When moist air encounters a mountain range, it rises and cools, causing precipitation on the windward side. As the air descends on the leeward side, it warms and dries out, leading to significantly less rainfall. This effect is primarily influenced by relief features (the mountains) and the pressure and wind system that drives the air movement.

Key Concept: Altitude

b) They block cold winds, resulting in milder winters

[Solution Description]

The Himalayas act as a barrier to cold winds from Central Asia, preventing them from entering the Indian subcontinent. This results in milder winters in India compared to Central Asia.

Key Concept: Climate Zones

b) Subtropical climate

[Solution Description]

The region north of the Tropic of Cancer in India lies in the subtropical zone. This area experiences a subtropical climate, which is characterized by hot summers and cool winters, differing from the tropical climate found in the southern part of the country.

Key Concept: Altitude

b) They block cold winds from Central Asia

[Solution Description]

The Himalayas prevent the cold winds from Central Asia from entering the subcontinent. This results in comparatively milder winters in India as compared to central Asia.

Key Concept: Latitude and Climate

c) The sea moderates the temperature fluctuations.

[Solution Description]

Coastal areas experience less temperature contrast due to the moderating influence of the sea. The sea absorbs heat during the day and releases it slowly at night, reducing temperature variations. Inland regions, however, lack this moderating effect, leading to greater temperature contrasts.

Key Concept: Altitude

d) Because of the Himalayas blocking cold winds

[Solution Description]

India experiences comparatively milder winters than Central Asia due to the presence of the Himalayas. These mountains act as a barrier and prevent the cold winds from Central Asia from entering the Indian subcontinent. As a result, the temperature in India remains relatively milder during winter.

Key Concept: Westerly Disturbances

c) Rainfall and cloudy weather

[Solution Description]

The syllabus mentions that Westerly Disturbances are low-pressure systems that bring cyclonic disturbances. These disturbances are generally associated with rainfall and cloudy weather in the northern plains of India during the cold weather season.

Key Concept: Continentality

c) Inland area far from any sea or ocean

[Solution Description] Continentality refers to the phenomenon where regions farther from the sea experience more extreme temperatures, i.e., very hot summers and very cold winters. Among the given options, a region located in the interior of a large landmass would experience the most extreme temperatures due to continentality.

Key Concept: Moderating Influence of the Sea

c) The sea’s ability to absorb and release heat

[Solution Description] The sea exerts a moderating influence on the climate by absorbing heat during summer and releasing it during winter, leading to milder temperature variations in coastal regions.

Key Concept: Continentality vs. Ocean Currents

b) Because of warm ocean currents

[Solution Description]

Coastal areas in India experience milder winters due to the moderating effect of ocean currents and proximity to the sea. The ocean retains heat longer than land, releasing it gradually during colder months. This results in less extreme temperature variations in coastal areas compared to inland regions, where continentality leads to harsher winters.

Key Concept: Pressure and Winds

c) They bring rainfall to the northern coast during October and November.

[Solution Description]

The north-easterly winds originate from the subtropical high-pressure belt and bring rainfall to the northern coast of India during October and November. These winds are significant for the post-monsoon rainfall in certain regions.

Key Concept: Relief Features and Precipitation

a) Moist air condenses and precipitates on the windward side

[Solution Description]

The windward side of a mountain receives moist air from the sea. As this air rises along the mountain slope, it cools down, leading to condensation and precipitation. By the time the air reaches the leeward side, it has lost most of its moisture, resulting in a relatively dry climate on that side.

Key Concept: Latitude, Climatic Controls

b) Lower latitudes receive more direct sunlight, leading to warmer climates

[Solution Description]

Latitude plays a crucial role in determining the climate of a place. Due to the curvature of the Earth, the amount of solar energy received varies with latitude. Locations closer to the equator receive more direct sunlight throughout the year, leading to higher temperatures. As one moves toward the poles, the angle at which the sun\’s rays hit the Earth becomes more oblique, resulting in less concentrated solar energy and cooler temperatures. Therefore, latitude directly affects the temperature and overall climate of a region.

Key Concept: Himalayas, Cold Winds, Milder Winters

d) Northern India experiences milder winters than Central Asia

[Solution Description]

The Himalayas act as a barrier that prevents cold winds from Central Asia from entering the Indian subcontinent. This results in northern India experiencing milder winters compared to regions at similar latitudes in Central Asia. Without the Himalayas, northern India would experience much colder winters due to the influence of these cold winds.

Key Concept: Continentality, Ocean Currents

b) City A will have colder winters than City B

[Solution Description]

City A, being inland, experiences continentality, which means it will have more extreme temperatures compared to City B. Since City B is influenced by the cold ocean current, its winters will be cooler than usual for a coastal area. However, due to the moderating effect of the sea, City B’s winter temperatures will still be less extreme than City A’s. Therefore, City A will have colder winters than City B.

Key Concept: Upper Air Circulation, Monsoon Onset

c) Helps in the distribution of rainfall

[Solution Description]

The tropical easterly jet stream flows over the southern part of India during the monsoon season and helps in the distribution of rainfall across the country by influencing the movement of weather systems.

Key Concept: Tropical Cyclones, Eastern Coast of India

b) Low-pressure conditions shifting from northwestern India to the Bay of Bengal

[Solution Description]

The primary factor contributing to the frequent occurrence of tropical cyclones along the eastern coast of India is the low-pressure conditions over northwestern India that shift to the Bay of Bengal by early November. This shift is associated with the occurrence of cyclonic depressions originating over the Andaman Sea. These cyclones cross the eastern coasts, causing heavy and widespread rain, and are often very destructive.

Key Concept: Relief Features, Latitude

a) Milder winters due to barrier effect

[Solution Description] The Himalayas act as a barrier to cold winds from Central Asia, preventing them from entering the Indian subcontinent. This results in milder winters in India compared to Central Asia, which is located at similar latitudes but lacks such a mountain barrier. The elevation and positioning of the Himalayas play a crucial role in moderating the climate.

Key Concept: Cold Weather Season

b) December and January

[Solution Description]

The cold weather season in northern India begins from mid-November and lasts until February. December and January are the coldest months in this region.

Key Concept: Cold Weather Season

c) Due to the moderating influence of the sea

[Solution Description]

The peninsular region of India does not have a well-defined cold season due to the moderating influence of the sea. This results in hardly any noticeable seasonal change in temperature pattern during winters.

Key Concept: South-West Monsoon Winds

d) South-West

[Solution Description]

The south-west monsoon winds originate from the south-east trade winds of the southern hemisphere. After crossing the equator, they change direction and blow in a south-westerly direction, entering the Indian peninsula as the south-west monsoon.

Key Concept: Monsoon Breaks

b) Movement of the monsoon trough

[Solution Description]

Breaks in the southwest monsoon rainfall occur due to the movement of the monsoon trough. When the axis of the monsoon shifts closer to the Himalayas, it leads to longer dry spells in the plains and heavy rainfall in the mountainous catchment areas.

Key Concept: Impact of Cyclones

c) Damage to Life and Property

[Solution Description] Cyclones crossing the eastern coasts of India, including the Tamil Nadu Coast, cause heavy and widespread rain. These cyclones often lead to significant damage to life and property, especially in densely populated delta regions like Godavari, Krishna, and Kaveri.

Key Concept: Temperature Variation, Altitude Influence

c) $17.0°C$

[Solution Description] The average annual temperature variation is calculated by finding the difference between the maximum and minimum temperatures observed in a year. Here, the maximum temperature is $12.0°C$ in May, and the minimum temperature is $-5.0°C$ in January. Therefore, the variation is $12.0 – (-5.0) = 17.0°C$.

Key Concept: Cold Weather Season, Northeast Trade Winds

c) Tamil Nadu

[Solution Description]

During the cold weather season in India, the northeast trade winds blow from land to sea, making most parts of the country dry. However, the Tamil Nadu coast receives rainfall because these winds blow from sea to land in this region.

Key Concept: Winter Rainfall, Importance

c) Northern Plains

[Solution Description]

Winter rainfall in India, known as Mahawat, is primarily caused by Western Disturbances originating from the Mediterranean region. These disturbances bring rainfall to the northern parts of India, particularly the states of Punjab, Haryana, Delhi, and Uttar Pradesh during the winter months.

Key Concept: Temperature variation, Influence of oceans

c) Moderating influence of the oceans

[Solution Description]

The temperature in peninsular India remains lower during the hot weather season due to the moderating influence of the oceans. The surrounding water bodies absorb heat and release it slowly, which helps in maintaining a relatively stable and lower temperature. This is in contrast to the northwestern parts of the country, where the absence of such large water bodies leads to higher temperatures.

Key Concept: Rising Temperature, Low Air Pressure

c) Rising temperatures cause air to expand and reduce air pressure

[Solution Description]

Rising temperatures cause the air to expand and become less dense. This decrease in air density leads to a drop in air pressure because there are fewer air molecules exerting force per unit area. The warm air rises, creating a region of low pressure at the surface.

Key Concept: Loo, Temperature Variations, Geographical Influence

b) Because of the moderating influence of the oceans

[Solution Description]

The moderating influence of the oceans keeps temperatures in peninsular India lower during the hot weather season. In contrast, the northwestern parts experience higher temperatures due to their distance from the oceans and the presence of the Thar Desert, which intensifies heat absorption and retention.

Key Concept: Temperature Variation, Loo, Dust Storms

d) Northwestern India

[Solution Description]

The syllabus mentions that in May, temperatures of 45° Celsius are common in the northwestern parts of the country. Additionally, the ‘loo’ and dust storms are prevalent in northern and northwestern India during this season. Therefore, the region that experiences the highest temperature in May and is affected by the ‘loo’ and dust storms is the northwestern part of India.

Key Concept: Monsoon Winds, Rainfall Distribution

c) The orographic lifting of moisture-laden winds

[Solution Description]

The south-west monsoon winds originate over warm subtropical areas of the southern oceans and cross the equator to enter the Indian peninsula as the south-west monsoon. As these winds blow over the warm oceans, they pick up abundant moisture. When these moisture-laden winds encounter the Western Ghats, they are forced to rise due to the orographic effect. This ascent cools the air, causing condensation and heavy rainfall on the windward side of the Western Ghats.

Key Concept: Regional Variations in Rainfall, Monsoon Characteristics

c) Owing to the retreating northeast monsoon

[Solution Description]

The Tamil Nadu coast receives significant rainfall during the winter months due to the retreating monsoon or northeast monsoon. During this period, the winds blow from land to sea over most of India, but they blow from sea to land over the Tamil Nadu coast, bringing moisture and causing rainfall. This is a unique feature of the region’s climate, which contrasts with the rest of India where the bulk of rainfall occurs during the southwest monsoon season.

Key Concept: Rain Shadow, Relief, Precipitation

c) Rain shadow effect caused by the Western Ghats

[Solution Description] The interior of the Deccan plateau and east of the Sahyadris lie on the leeward side of the Western Ghats. When moisture-laden winds from the Arabian Sea hit the Western Ghats, they rise and cool, causing heavy rainfall on the windward side. As these winds descend on the leeward side, they become dry, resulting in minimal rainfall. This phenomenon is known as the rain shadow effect.

Key Concept: Monsoon Trough Movement, Breaks in Monsoon

b) The axis of the monsoon trough shifts closer to the Himalayas.

[Solution Description]

The monsoon trough is a region of low pressure that drives the monsoon winds. When the axis of this trough shifts closer to the Himalayas, it causes the rain-bearing winds to move away from the plains. This results in longer dry spells in the plains as the rainfall activity becomes concentrated in the mountainous regions. Consequently, the plains experience reduced rainfall, leading to dry conditions.

Key Concept: Retreating Monsoon, Cyclonic Depressions

c) Owing to the transfer of low-pressure conditions to the Bay of Bengal

[Solution Description]

The retreating monsoon season is marked by the shift of low-pressure conditions from north-western India to the Bay of Bengal. This shift leads to the formation of cyclonic depressions that originate over the Andaman Sea. These cyclones move towards the eastern coasts of India, bringing with them moist air from the Bay of Bengal. As the cyclones make landfall, the warm moist air rises, cools, and condenses, resulting in heavy and widespread rainfall. This phenomenon is particularly pronounced along the Coromandel Coast, where the bulk of the rainfall during this period is derived from these cyclonic depressions.

Key Concept: Retreating Monsoon, Cyclonic Depressions

c) Movement of the sun towards the south and weakening of the monsoon trough

[Solution Description]

During the retreating monsoon season, the low-pressure conditions over north-western India weaken due to the apparent movement of the sun towards the south. This weakening causes the low-pressure system to shift towards the Bay of Bengal by early November. This shift is associated with the formation of cyclonic depressions, which originate over the Andaman Sea and cause heavy rainfall along the eastern coast of India.

Key Concept: October Heat, Weather Patterns

b) Residual moisture from the monsoon and increased solar radiation

[Solution Description]

The “October Heat” phenomenon occurs due to the withdrawal of the southwest monsoon, which leaves behind residual moisture in the atmosphere. This moisture, combined with clear skies and increased solar radiation, leads to a rise in temperature and humidity levels. Additionally, the absence of rain allows the land to heat up more quickly.

Key Concept: Cyclonic Depressions, Monsoon Trough

d) The monsoon trough shifts southward.

[Solution Description]

The shift of low-pressure conditions from north-western India to the Bay of Bengal by early November is primarily due to the movement of the monsoon trough. This trough is a region of low atmospheric pressure that influences the direction and intensity of weather systems. As the monsoon retreats, this trough shifts southward, leading to the formation of cyclonic depressions over the Bay of Bengal.

Key Concept: Rainfall Variability

b) Due to high variability in rainfall

[Solution Description] The syllabus explains that due to the high variability of rainfall in low rainfall areas, such as parts of Rajasthan and Gujarat, these regions are prone to droughts. Hence, the correct answer is due to high variability in rainfall.

Key Concept: Rainfall Variability

d) Due to high variability in rainfall

[Solution Description]

Areas of low rainfall, such as parts of Rajasthan and Gujarat, experience high variability in annual rainfall. This variability leads to insufficient water supply, making these regions more prone to drought conditions.

Key Concept: Areas Receiving Low Rainfall

b) Ladakh

[Solution Description] The region around Leh in Jammu and Kashmir is characterized by low precipitation due to its high altitude and distance from monsoon winds.

Key Concept: Monsoon Impact

b) Regional variations in climatic conditions

[Solution Description]

The monsoon climate in India is characterized by regional variations in climatic conditions despite an overall unity in the general pattern, particularly in temperature and precipitation.

Key Concept: Drought-Prone Areas

c) Western Rajasthan

[Solution Description]

The regions of western Rajasthan, adjoining parts of Gujarat, Haryana, and Punjab receive less than 60 cm of rainfall annually. This makes them highly susceptible to droughts. Additionally, the interior of the Deccan plateau and east of the Sahyadris also receive low rainfall, making them drought-prone. Leh in Jammu and Kashmir is another area with low precipitation. Comparing these regions, western Rajasthan and its adjoining parts are the most drought-prone due to their consistently low rainfall.

Key Concept: Seasonal alteration

b) It provides a rhythmic cycle of seasons

[Solution Description]

The seasonal alteration of wind systems in India provides a rhythmic cycle of seasons, which is crucial for agricultural activities and the overall lifestyle of the people. This change in weather conditions is a typical feature of the monsoons.

Key Concept: Agriculture and Monsoon

c) Provides water for agricultural activities

[Solution Description]

The monsoon season provides the necessary water for agricultural activities, setting them in motion and ensuring the growth of crops across the country.

Key Concept: Monsoon as a Unifying Bond

c) It influences the timing and nature of festivals like Teej and Onam.

[Solution Description]

The monsoon plays a significant role in shaping the cultural festivals of India. The arrival of the monsoon is eagerly awaited as it marks the beginning of the agricultural season, which is crucial for the economy and lifestyle. Festivals like Teej and Onam are celebrated to welcome the monsoon, reflecting its importance in Indian culture and traditions.

Key Concept: Monsoon’s Impact on Agriculture

c) By determining the timing of planting and harvesting

[Solution Description]

The monsoon determines the timing of planting and harvesting by providing the necessary water for crops. It sets the agricultural activities in motion, ensuring that farmers can cultivate their fields and produce food for the population.

Key Concept: Irregular Monsoon Patterns

c) Disrupts farming schedules and crop yields

[Solution Description]

The irregularity of monsoon patterns, characterized by unpredictable arrival and retreat times, as well as varying intensity, frequency, and duration of rainfall, significantly disrupts the farming schedules of millions of farmers across India. This unpredictability can lead to either excessive rainfall causing floods or insufficient rainfall leading to droughts, both of which adversely affect crop yields and agricultural productivity.

Key Concept: Mountain Barriers and Rainfall

a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.

[Solution Description]

The assertion states that the Himalayas act as a barrier to the monsoon winds, which is true. The reason explains that the monsoon winds rise over the Himalayas, causing orographic rainfall on the windward side and a rain shadow effect on the leeward side. This is also true and directly explains the assertion. Therefore, both the assertion and reason are true, and the reason correctly explains the assertion.