WBBSE Class 8 Geography Chapter 5 Cloud And Rain Topic B Precipitation

Chapter 5 Topic B Precipitation Analytical Type Questions

Question 1. Explain the process of convectional rainfall with a diagram and examples.
Answer:

Process Of Convectional Rainfall With A Diagram:-

This type of rainfall is caused by convection currents generated in the atmosphere by the sun’s heat. So, it is known as convectional rainfall.

Some places on earth (especially the Equatorial region) have greater areas under waterbodies as compared to land and experience extremely hot climatic conditions due to perpendicular sun rays.

The air above land and water surfaces, being very hot and light, rises vertically, along with its moisture content. In the higher and cooler layers of the atmosphere, the air gets saturated due to a decrease in temperature and the water vapour in it cools and condenses into small droplets of water.

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The droplets gather around dust particles to form clouds. When the clouds get denser and the drops of water become bigger, they drop down as rain on Earth. This type of rainfall is known as convectional rainfall.

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Characteristics of convectional rainfall:

The characteristics of convectional rainfall are as follows-

1. Origin and another name:

Usually, cumulonimbus clouds cause convectional rain. It is also called ‘4 o’clock rain’ or ‘afternoon shower due to its occurrence in the afternoon or evening.

2. Area:

Convectional rainfall occurs on either side of the equator, up to 5°-10° latitudes and also in the tropical regions.

3. Type and nature:

This type of rainfall has a short duration but the amount is very high and the sky becomes completely clear after the rainfall.

4. Amount of rain:

It is about 200 cm-300 cm annually on average in the Equatorial region.

5. Time:

Rainfall occurs throughout the year in the Equatorial region, in the beginning of summer in the temperate regions and in the pre-monsoon or autumn season of the tropical regions.

Class 8 Geography Chapter 5 Types of Precipitation

6. Occurrence of thunderbolts:

Thunderbolts are very common along with convectional rain. Example-Thunderbolts are very common with Kalbaishakhi.

 

Example; The Equatorial region receives convectional rainfall every afternoon, while the tropical zone receives it at the beginning of summer. The state of West Bengal in India receives convectional rainfall occasionally during late summer afternoons.

Question 2. Explain orographic rainfall with an example and a diagram.
Answer:

Orographic Rainfall:-

When moist air from waterbodies blows towards land and is obstructed by a mountain in its path, it is forced to rise along the slope (windward side) of the mountain. This rapid rise helps the air to expand and cool.

Consequently, it condenses and gives plenty of rainfall on the windward slope only. This is called orographic rainfall or relief rainfall. After the rainfall, the wind becomes light enough to cross the mountain and blow downwards.

But now the wind is almost dry and cannot cause any rainfall on the other side (leeward side). Moreover, as the wind moves down the leeward side, which is also called rain shadow area, the temperature of air increases and its capacity to hold moisture also increases.

So, there is no chance of condensation or precipitation on that slope.

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For example,

1. The western slope of the Western Ghats receives a considerable amount of orographic rain, whereas the eastern slope of the same mountains is the rainshadow area.
2. Mawsynram and Cherrapunji record the highest amount of rain. Their location is on the southern windward slope of the Khasi Hills in Meghalaya. Cherrapunji receives about 11777 mm of rainfall annually, whereas Shillong on the leeward slope of the same hill and only 56km apart receives only 2207 mm of annual rain. (Mawsynram receives more than 1200mm of rainfall annually.)

 

Question 3. Which branch of the monsoon causes rainfall in Cherrapunji and why?
Answer:

Branch Of The Monsoon Causes Rainfall In Cherrapunji:-

Indian monsoon has two branches-the Arabian Sea branch and the Bay of Bengal branch. Cherrapunji, located in the northeastern part of India, receives relief rainfall from the Bay of Bengal branch of monsoon winds.

The sun is vertically overhead on and around the Tropic of Cancer in May and June. As a result, an intensely hot low-pressure zone develops in northern India.

To fill that vacuum, cold moist winds from the Bay of Bengal rush in through Bangladesh to reach north-eastern India. Here, the moist monsoon winds get obstructed by the Khasi Hills of the Meghalaya plateau and plateau and cause profuse orographic rainfall on the windward slope of the hills.

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Cherrapunji is situated on the windward slope of the Khasi Hills and so this place records the world’s highest amount of rainfall (about 11777mm).

 

Question 4. Explain the mechanism behind cyclonic rainfall in temperate regions.
Answer:

Mechanism Behind Cyclonic Rainfall In Temperate Regions:-

In the temperate regions (35°-65° north and south latitudes), air masses of different temperatures blow from opposite directions. Hot and moist air blows from the tropics in the southwest, while cold and dry air blows from the polar region in the northeast. These two meet along a line called ‘front. The front is of mainly two types- warm front and cold front.

A warm front is defined as a region in which there is an active movement of warm air over cold air. A cold front, on the other hand, is defined as a front along which cold air is invading the warm air zone.

A disturbance is created when the opposite air masses meet. The warm air mass overrides the cold air as the former is lighter. The moisture in the warm air condenses on coming into contact with the cold air and causes rainfall.

Rainfall during a temperate cyclone is drizzling and lingering, unlike tropical cyclones where thundershowers are seen.

Characteristics of Precipitation for Class 8

Question 5. Explain the phenomenon of cyclonic rainfall in the tropical region.
Answer:

Phenomenon Of Cyclonic Rainfall In The Tropical Region:-

Tropical cyclones originate on either. side of the equator (5°-20° latitudes). The extremely hot condition creates a severe low-pressure area (called the ‘eye’ of a cyclone).

The relatively cold, heavy winds from surrounding places rush to fill in the vacuum. Again, those cold winds rise, on being heated and in this process expand, cool and condense, finally to precipitate.

The speed of these whirling cold winds increases proportionately with the increasing intensity of the low-pressure eye. The eye is a smaller area that remains calm and quiet with clear skies, but the spinning cold winds outside the eye cause violent storms, along with rainfall.

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This cyclonic rain may develop into a more violent type of tropical storm. There is lighter tropical cyclonic rainfall also. Tropical cyclones are more powerful over water and lose energy while advancing landward. These cyclones usually occur in autumn.

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Question 6. What do you mean by the eye of a cyclone?
Answer:

Eye Of A Cyclone:-

The centre of a tropical cyclone, which has the lowest air pressure, is called the ‘eye’ of the cyclone.

The following are its features

1. If the eye of a cyclone has very low pressure, the cyclone becomes more powerful and devastating.
2. The eye has a clear sky and calm weather without any clouds.
3. As winds move towards the central low-pressure region, i.e., the eye, according to Ferrel’s law, they move in an anti-clockwise direction in the northern hemisphere and a clockwise direction in the southern hemisphere.
4. Winds converge at the eye.
5. The radius of this eye can be 20km-80km.
6. The region around the eye is generally covered by dense cumulonimbus clouds which cause strong cyclonic winds and heavy rainfall.

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Question 7. Classify precipitation.
Answer:

Classification Of Precipitation:-

Precipitation can be classified into- liquid form and solid form.

Liquid form of precipitation:

Hot and moist air cools and condenses on reaching the upper atmosphere and forms water droplets that float as clouds. Eventually, these are brought down as rain due to the gravitational pull of the earth.

Rainfall can be of three types

1. Convectional rainfall
2. Relief or orographic rainfall, and
3. Cyclonic rainfall.

Drizzle is another liquid form of precipitation when droplets of water less than 0.5 mm in diameter come down as rain.

The solid form of precipitation:

Solid forms of precipitation are as follows

1. Snowfall:

In cold regions, tiny droplets of water alter to specks of snow and fall as a powdery substance on Earth. This is snowfall.

2. Hailstorm:

Upward air current pushes the droplets of water to a great height. Here the temperature drops and water droplets form small particles of ice.

When more droplets of water gather around these ice particles, they expand in volume and fall on earth with rain. This is called a hailstorm.

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3. Sleet:

Combined precipitation of water- droplets and ice particles.

Question 8. Differentiate between fog and cloud?
Answer:

The differences between fog and cloud include

 

Chapter 5 Topic B Precipitation Short Analytical Type Questions

Question 1. Explain the cycle of rainfall. Or, Explain the various stages of rainfall.
Answer:

Cycle Of Rainfall:-

Rainfall is the final product of the following stages

1. Evaporation:

Solar energy causes surface water from seas, oceans, rivers, lakes, and ponds to evaporate to form water vapour, which is lighter than air and rises.

2. Condensation:

The water vapour ascends, expands and cools. It condenses and converts into tiny particles of water that join each other and become larger droplets.

Short Answer Questions on Precipitation for Class 8

3. Precipitation:

When these larger droplets coalesce with each other, they cannot remain suspended any more. They are attracted by gravitational pull and cause Clouds that may rainfall on the earth’s surface.

The size of droplets varies, based on the particles they combine with. This rainwater flows back to the waterbodies as surface run-off.

Question 2. What do you know about convectional rainfall?
Answer:

Convectional Rainfall:-

In the torrid zone (including the tropics and the equator) a convection current sets in due to extremely hot conditions during the day.

The air in these regions has a lot of water vapour in it because of

1. The greater surface area of water, and
2. Higher temperature.

This moist and hot air rises rapidly and cools down on coming into contact with the cold upper layers of the atmosphere. Ultimately, it condenses to cause heavy rainfall at the third quarter of the day (or afternoon). This is known as ‘convectional rainfall.

Question 3. Why is convectional rainfall common in the Equatorial region?
Answer:

Convectional Rainfall Common In The Equatorial Region:-

When the earth’s surface gets extremely heated, the air above it becomes hot and rises vertically with all its moisture content.

In the higher layers of the atmosphere, the hot, moist air expands, cools condenses and eventually falls on Earth as rainfall. As it is caused by convection currents, it is called convectional rainfall.

The Equatorial region has a lot of water bodies and also has high temperatures. throughout the year. So, convectional rainfall occurs nearly every evening or in the late afternoon. This is also called a 40’clock rain or afternoon shower.

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Question 4. Why does the amount of convectional rainfall increase in summer?
Answer:

Amount Of Convectional Rainfall Increase In Summer:-

Convectional rainfall is chiefly associated with temperature. In summer, during the day, the sun’s rays fall vertically on the land and consequently, the air above it becomes hot. Hot air has a greater capacity to hold moisture.

With increasing temperature, this hot and moist air rises vertically (due to convection current) expands, cools and finally condenses at higher levels of the atmosphere. This causes heavy rainfall (convectional) in the Equatorial region.

With an increase in temperature in summer, the amount of convectional rainfall also increases.

Question 5. Name the areas that receive heavy rainfall in India and explain why they do so.
Answer:

India receives rainfall mainly from the southwest monsoon winds, but these are highly irregular and sporadic. It has been observed after a thorough study that two regions receive the maximum amount of rainfall in India.

This is the western slope of the Western Ghats or Western coastal plains and eastern and Northeastern parts of India.

1. Western slope of the Western Ghats:

The western slope of the Western Ghats, being the windward side, receives plenty of orographic rainfall from the Arabian Sea branch of the southwest monsoon winds.

2. Eastern and north-eastern parts of India:

The entire region is located at the eastern and northeastern foothills of the Himalayas and receives heavy rainfall. The rain-bearing winds from the Bay of Bengal branch of the southwest monsoon get obstructed here and thus cause heavy rainfall.

Question 6. Think and comment on the relation between relative humidity and air temperature.
Answer:

Relative humidity and air temperature have an inverse relationship. The capacity of air to hold moisture depends on temperature. Thus, if air temperature increases, its capacity to hold moisture increases.

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Similarly, if the air temperature decreases, its capacity to hold moisture also falls. An increase in air temperature thus implies a fall in its relative humidity. Similarly, a decrease in air temperature results in an increase in relative humidity.

Question 7. What is a windward slope?
Answer:

Windward Slope:-

When moisture-laden winds blow from water bodies towards the land, at times, these are obstructed by mountains across their path. On striking the mountains, these winds rise the mountain slopes.

The rapid rise causes them to expand, cool, condense and ultimately to precipitate on these slopes only. The side of a mountain which receives relief or orographic rainfall is called the windward slope.

For example, the western slope of the Western Ghats is the windward side of the southwest monsoon winds (Arabian Sea branch).

Question 8. What is a rainshadow area?
Answer:

Rainshadow Area:-

The leeward side of a mountain is called a rainshadow area. After orographic or relief rainfall on the windward side of a mountain, when the wind crosses over the mountain and blows down the opposite or the leeward side, it has very little moisture left.

Its capacity to hold moisture also increases, as the air temperature increases. So, little or no precipitation occurs on this side. Hence, this leeward side is called a rainshadow area.

For example, the northern slope of the Khasi Hills in the Meghalaya Plateau is leeward and is therefore a rainshadow area.

Question 9. Why does the amount of rainfall received in Cherrapunji and Shillong differ drastically even though they are not very far away from each other?
Answer:

Cherrapunji is located on the windward slope of the Khasi Hills in Meghalaya, while Shillong is situated on the leeward slope of the same hill (just about 56km apart).

Due to this locational advantage, Cherrapunji receives very heavy rainfall from the southwest monsoon winds coming from the Bay of Bengal.

On the other hand, Shillong, being on the leeward side, is in the rainshadow area and remains comparatively dry even during the rainy season. The annual average rainfall at Cherrapunji is about 11777 mm, whereas Shillong records only about 2207 mm of rainfall annually.

Question 10. Why does the western slope of the Western Ghats receive heavy rainfall while the eastern slope remains dry?
Answer:

The Arabian Sea branch of the south-west monsoon winds on entering the Indian landmass, are first obstructed by the western slope of the Western Ghats.

The western slope receives plenty of orographic or relief rainfall from these moist winds. After the heavy downpour, the winds become lighter, cross the mountain and blow down the eastern slope into the interior of the Deccan Plateau.

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It causes little or an almost negligible amount of rain there. So, the eastern slope of the Western Ghats is a rainshadow area.

Question 11. Why is rainfall in Pune lower than that in Mumbai?
Answer:

Rainfall In Pune Lower Than That In Mumbai:-

The Arabian Sea branch of the southwest monsoon winds causes heavy rainfall in the western coastal plain of India due to its location on the windward side of the Western Ghats.

This plain receives about 500cm-700cm of rainfall, annually. Mumbai is situated on this side of the Western Ghats and thus receives sufficient relief rainfall.

When the same branch of south-west monsoon winds reaches the leeward side of the Western Ghats, it cannot cause any significant amount of rainfall in the Deccan Plateau region due to lack of moisture content, thus turning it into a rainshadow area.

Pune lies in this rain shadow area and thus rainfall here is lower than that in Mumbai.

Question 12. What is relative humidity?
Answer:

Relative Humidity:-

The ratio between the amount of water vapour present at a specific temperature and the amount of water vapour that the same volume of air requires to become saturated at that temperature is called relative humidity.

It is always expressed as a percentage. Relative humidity can be measured by the following formula-

For example, a definite volume of air absorbs 15 gm of water vapour at 25°C and it would be able to hold another 22.9 gm of water vapour before it becomes saturated. In that case

Question 13. What is absolute humidity?
Answer:

Absolute Humidity:-

The total amount of water vapour present in a definite volume of air at a particular temperature is called its absolute humidity. It is greater during the day than at night, in summer than in winter, in the Equatorial region than in the Polar zones.

For example, if 1 cc of air contains 5gm of water vapour, the absolute humidity of that volume of air will be 5 gm/cc.

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Question 14. Write the differences between the windward slope and the leeward slope.
Answer:

The differences between windward slope and leeward slope are as follows

 

Question 15. Write the differences between tropical cyclones and temperate cyclones.
Answer: The differences between tropical cyclones and temperate cyclones are as follows-

 

Question 16. Differentiate between precipitation and rainfall.
Answer: The differences between precipitation and rainfall are as follows-

 

Question 17. Why are dust particles necessary for the formation of clouds and rainfall?
Answer: Dust Particles Necessary For The Formation Of Clouds And Rainfall:

To start the process of condensation, there must be an abundant supply of microscopic dust particles in the air. Such particles are capable of attracting or absorbing water.

These are generally salt particles, pollens, etc. Water droplets become cool and condensed while moving in the upper air. These reside on the dust particles and form clouds. Later rainfall occurs from the clouds.

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Question 18. Why do evergreen forests grow in the Equatorial region?
Answer: Evergreen Forests Grow In The Equatorial Region:-

Evergreen rainforests are the characteristic feature of the Equatorial region. These forests generally grow in the Equatorial region because of the following-

1. High temperature:

This region has high temperature throughout the year. Temperature generally varies between 25°C to 30°C. This condition favours the growth of evergreen forests.

2. Abundant rainfall:

The average annual rainfall in this region is about 250 cm. Plenty of convectional rainfall promotes the growth of evergreen forests.

3. High humidity:

The humidity level always remains high in this region. High humidity in the atmosphere is a major factor that helps in causing plenty of rainfall.

These are the reasons why evergreen forests are found in the Equatorial region due to favourable climatic conditions.

Question 19. What disruption or inconvenience does fog cause in our daily lives?
Answer: Fog causes several problems in our daily lives. Some of these are as follows-

1. It obscures our visibility and hampers transportation via road, air and rail.
2. Fog, in combination with smoke and dust, creates ‘smog’, which is very harmful for our health.
3. Fog damages the crops.
4. Fog influences the weather conditions of places locally.

Question 20. What are the different types of rainfall in India?
Answer: India is blessed with almost all kinds of rainfall. The different kinds of rainfall prevalent in India are-

1. Convectional rainfall occurs in West Bengal during the early summer.
2. Orographic or relief rainfall is prevalent in the windward slopes of mountains across the path of southwest monsoon winds. South-west monsoon winds again have two branches-
3. The Arabian Sea branch that causes heavy rainfall along the western slope of the Western Ghats, and
4. The Bay of Bengal branch dashes against the southern slope of the Khasi Hills in Meghalaya and causes heavy rainfall there.
5. During autumn and the dewy season (called ‘Hemanta’ in Bengali), occasional cyclonic rainfall occurs in the coastal regions of India.
6. Winter rain occurs in the north and north-western part of India particularly in Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Uttar Pradesh and Punjab from the ‘western disturbances’ of the Mediterranean region.

Question 21. Why does it not rain from all the clouds?
Answer:

The following conditions are essential for the occurrence of rainfall from clouds-

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1. To start the process of condensation, there must be an abundant supply of microscopic dust particles in the cloud, otherwise condensation will not occur.
2. The floating water droplets of a cloud are usually 0.01mm in radius. Unless these join together to become at least 0.5mm in diameter, these cannot be attracted by the gravitational pull of the earth and they cannot fall as raindrops.
3. The floating droplets of water, which form a cloud, cannot cause rainfall until they coalesce with each other.
4. The relative humidity of the atmosphere has to be 100%, otherwise, condensation and precipitation will not occur.

Question 22. Think and say why dew and fog are not classified as precipitation.
Answer:

Fog and dew are not regarded as forms of precipitation as these are not formed by the upward movement of air and do not earth’s surface due to the gravitational pull of the earth.

1. Dew:

The moisture deposited on objects such as grass, leaves and stones on the earth’s surface in winter nights is known as dew. Dew form when the sky is cloudless and when the radiation from the ground has cooled the lower layers of the atmosphere and the water vapour in it below the dew point.

2. Fog:

During winter nights, when the surface of the earth becomes very cold, the air just above it also cools and condenses, around dust particles, forming tiny droplets of water floating in the lower layer of the atmosphere appearing like smoke.

This is known as fog. Fog is essentially a type of cloud that forms at the surface of the earth, and is not any kind of precipitation.

Question 23. Different types of rainfall occur within West Bengal. Make a list of the different areas and different types of rainfall that occur there throughout the year.
Answer: The different types of rainfall occurring all over West Bengal are-

1. Convectional rainfall:

During early summer in every region of south and central Bengal, convectional rainfall occurs.

2. Cyclonic rainfall:

This type occurs in districts of North and South 24 Parganas, Kolkata, East and West Bardhaman, Bankura, East and West Midnapore, Birbhum, Howrah and Hooghly.

During the monsoon and autumn seasons, cyclonic rainfall occurs mainly in Digha, Sundarbans and Mandarmani areas.

3. Orographic rainfall:

Darjeeling, Jalpaiguri and other hilly areas in West Bengal experience this type of rainfall.

Question 24. Collect information regarding different types of rainfall that your locality experiences and note them down.
Answer:

The different types of rainfall that my locality (areas in and around Kolkata) experiences during different seasons are-

 

Question 25. Write a short note on snowfall.
Answer: Snowfall:-

If the air temperature at the higher levels of the atmosphere is below the freezing point (0°C) of water, condensation of water vapour into ice particles takes place.

Generally, as snow falls due to the gravitational pull of the earth, it passes through the warm air, melts and drops down as rain.

But in mountainous regions or cold climatic zones, where the air is very cold even near the earth’s surface, snow falls in shapes similar to sugar crystals or fluffy bunches of cotton. This is snowfall.

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Question 26. Describe the instrument used to measure the amount of rainfall.
Answer: Instrument Used To Measure The Amount Of Rainfall:-

Rainfall is measured by an instrument named a rain gauge. It consists of a funnel, usually 5 inches or 13 cm in diameter and a glass vessel or bottle of the same diameter. The funnel is fitted in such a manner that not a single drop of rainwater can escape. Rainwater is collected in the glass bottle for about 24 hours.

 

 

The instrument is placed about one foot above the ground to prevent the entry of water from outside by splashing. The water collected is then measured in a measuring glass or cylinder to get the amount of daily rainfall.

Question 27. What do you mean by hail?
Answer: When clouds or tiny droplets of water are forced to rise high up in the sky by convectional air currents, the water droplets freeze into small grains of ice.

When more droplets of water gather around these ice particles they expand in volume and fall on earth with rain. This is called hail. Hailstorms are observed in sub-tropical and temperate zones.

When more droplets of water gather around these ice particles they expand in volume and fall on earth with rain.

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Chapter 5 Topic B Precipitation Short Answer Type Questions

Question 1. What is precipitation?
Answer:

Precipitation:-

When water vapour in the atmosphere condenses and falls on the earth as water droplets or ice particles, due to the gravitational pull of the earth, it is called precipitation.

Question 2. What is rainfall?
Answer: Rainfall:

The evaporated water rises with hot, light air and condenses after reaching the upper strata of the atmosphere to form tiny droplets of water that form clouds.

When these floating water droplets join together to become bigger (with a diameter of 2mm), they drop down as rainfall due to the earth’s gravitational pull. Rainfall is a liquid form of precipitation.

Question 3. Name two places that experience convectional rainfall throughout the year.
Answer: Two Places That Experience Convectional Rainfall Throughout The Year:

Two places that experience convectional rainfall throughout the year are-

1. Amazon Basin in South America and
2. Zaire Basin in Africa.

Question 4. Why does rainfall occur from cool air?
Answer:

Rainfall Occurs From Cool Air:-

If air loses heat and becomes cool, the relative humidity increases and the air gets saturated faster. After that, the water-holding capacity of the saturated air decreases and the water droplets come down to the surface as rainfall as a result of the earth’s gravitational pull.

Therefore, when the air cools down, the water droplets become denser and rainfall occurs.

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Question 5. What do you understand from the statement “relative humidity of an area is 70%”?
Answer:

Relative Humidity Of An Area Is 70%:-

The relative humidity of an area is 70% implies that the air at that place and at that given temperature needs 30% more water vapour to reach 100%, i.e., to become saturated.

Saturated air has 100% relative humidity while dry air has 0% relative humidity.

Question 6. What is orographic rainfall?
Answer:

Orographic Rainfall:-

Being obstructed by a mountain across its path, moist air rises very rapidly along the mountain slope and expands, cools and condenses there, precipitating only on that side of the mountain. This is called orographic rainfall (‘oros’, means ‘mountain’ and ‘graphy’ means to ‘rise’). For example, orographic rainfall occurs on the western slope of the Western Ghats in India.

Question 7. What is cyclonic rainfall?
Answer:

Cyclonic Rainfall:-

Low pressure over an area attracts cold air from the surrounding high-pressure areas towards it at a great speed. The lighter hotter air of that region rises.

It expands to cool and condense in the upper layers to form clouds, finally precipitating with thunder and lightning. This is called ‘cyclonic rainfall.

It is also called frontal rain in temperate areas because a ‘front’ or boundary is formed between the two contrasting air masses.

Question 8. What is ‘Aswiner Jhar?
Answer:

As winter Jhar:-

In the months of ‘Aswin’ and ‘Kartik’ (October-November) of the Bengali year Bangladesh, West Bengal and eastern India experienced a cyclonic storm. This is called ‘Aswiner Jhar’. It is caused by the retreating monsoon winds. This is more common in the coastal regions of the Bay of Bengal.

Question 9. Name any two recent cyclones in India.
Answer:

Two Recent Cyclones In India:-

The names of two recent cyclones in India are

1. Hudhud in 2014 and
2. Fani in 2019.

Question 10. Name the different forms of condensation.
Answer: Different Forms Of Condensation:                     

The common forms of condensation are dew, frost, fog, smog and clouds. Fog and clouds are the most important concerning atmospheric processes.

Question 11. What is acid rain?
Answer: Acid Rain:

When oxides of sulphur and nitrogen released in the air due to pollution react with water vapour in the atmosphere to form acid, which when comes down to rainwater is known as acid rain.

It has harmful effects on plants, aquatic life, as well as on buildings. Acid rains mainly occur as a result of air pollution.

Question 12. What is frost?
Answer: Frost:

In cold countries and at high altitudes of the hot or torrid zone, when the night temperature is minimal, dew freezes and becomes hard and solid. This is called frost.

Question 13. What is isohyet or equipluve line?
Answer:

Isohyet Or Equipluve Line:-

The imaginary line that joins places on a map, recording equal average annual rainfall at a particular time is called the isohyet equipluve line.

The characteristics of these lines are

1. These are usually curved lines.
2. The value of the lines is maximum in the Equatorial region, while it is minimum at the poles.
3. These lines never touch or cross each other.

 

 

Question 14. Why is less dew observed in dry regions?
Answer:

Less Dew Observed In Dry Regions:-

The air in dry areas has a lesser amount of water vapour in it. So, at night when the heat radiates back from the surface, the air near the surface becomes cooler but condensation does not take place due to lack of water vapour.

Thus, less dew is observed in dry regions.

Question 15. Why is fog mainly seen in winter and on waterbodies?
Answer:

Fog Mainly Seen In Winter And On Waterbodies

The amount of heat that a landmass can absorb during the day in winter, radiates back more heat than that during long winter nights.

Thus, when the layer near the earth’s surface gets cooled, the water vapour in it condenses around dust particles present in the air and leads to the formation of fog in winter.

Also, the air above the waterbodies having more water vapour content than the landmass, causes the formation of fog mainly on waterbodies.

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Question 16. Why does a barefooted morning walk on the grass make your feet wet in winter?
Answer:

Barefooted Morning Walk On The Grass Makes Your Feet Wet In Winter:-

Dew is a form of condensation which consists of tiny droplets of water on the surface of objects rather than on dust particles in the air. It is produced when the heat radiation from the ground surface cools the lower layers of the atmosphere in night.

As a result, the water vapour in it condenses and gets deposited on trees and grass surfaces as droplets of water called dew. Thus, a barefooted morning walk on the grass makes our feet wet in winter.

Question 17. Briefly write about the drizzle.
Answer:

Drizzle:-

Often tiny droplets of water (0.5 mm or less in diameter) fall continuously on Earth from nimbostratus clouds over a large area.

It may be the result of low pressure in that region. These droplets are so light that they float along with the wind. This type of rainfall is called drizzle.

Question 18. What is mist?
Answer: Mist:

Water vapour, which condenses and descends as fine droplets, remains suspended in the air, and takes a smoke-like, appearance and is called mist. It is visible just above the earth’s surface. It is less dense and long-lasting than a fog.

Question 19. What is sleet?
Answer: Sleet:

Sleet is fine particles of ice mixed with rain. This form of precipitation occurs when the lower layers of the atmosphere are cooled down to almost the freezing point.

Question 20. What type of rainfall is generally observed in our country in the monsoon season?
Answer: Type Of Rainfall Is Generally Observed In Our Country In The Monsoon Season:

Our country receives two types of rainfall in the monsoon season.

These are

1. Orographic or relief rainfall in the mountain regions,
2. Cyclonic rainfall in many places at the end of the monsoon.

Question 21. Write a short note on moisture retaining capacity.
Answer:

Moisture Retaining Capacity:-

Moisture retaining capacity refers to the capacity of an air of a certain volume at a certain temperature to retain the maximum amount of moisture content. It is also known as humidity capacity.

It is positively related to temperature, i.e., the higher the temperature, the higher the retention capacity and vice versa. It is expressed in grams per cubic centimetre.

Class 8 Geography Solution WBBSE

Chapter 5 Topic B Precipitation Multiple Choice Questions Choose The Correct Option

Question 1. Rainfall is of-

1. 2 types
2. 3 types
3. 4 types
4. 5 types

Answer: 2. 3 types

Question 2. The most commonly occurring rainfall on the earth is-

1. Convectional rainfall
2. Orographic rainfall
3. Cyclonic rainfall
4. Sleet

Answer: 2. Orographic rainfall

Question 3. Rainfall that occurs when the sun’s heat causes water on the earth’s surface to rise as a vapour to form clouds, is known as

1. Convectional rainfall
2. Orographic rainfall
3. Drizzle
4. Cyclonic rainfall

Answer: 1. Convectional rainfall

Question 4. Convectional rainfall occurs in the Equatorial region during-

1. Summer
2. Winter
3. The entire year
4. Spring

Answer: 3. The entire year

Question 5. The type of rainfall that is observed in the Equatorial region is-

1. Convectional
2. Frontal
3. Orographic
4. Drizzle

Answer: 1. Convectional

Class 8 Geography Solution WBBSE

Question 6. Relative humidity is expressed in terms of-

1. Decimal
2. Degree
3. Percentage
4. Mass

Answer: 3. Percentage

Question 7. In comparison to cold air, warm air is-

1. Lighter
2. Of equal weight
3. Heavier
4. None of the above

Answer: 1. Lighter

Question 8. In comparison to dry wind, moisture-laden wind is-

1. Lighter
2. Heavier
3. Of equal weight
4. None of the above

Answer: 1. Lighter

Question 9. The relative humidity of saturated air is-

1. 0%
2. 100%
3. 50%
4. 150%

Answer: 2. 100%

Question 10. If the temperature of a volume of air increases, its capacity to hold moisture-

1. Increases
2. Remains the same
3. Decreases
4. None of the above

Answer: 1. Increases

Question 11. Rainshadow regions are formed along the

1. Slopes of the foothills
2. Leeward slope
3. Windward slope
4. Intermediate slope

Answer: 2. Leeward slope

Question 12. The branch of monsoon wind that causes rainfall in Mawsynram, India, is the

1. Bay of Bengal branch
2. Arabian Sea branch
3. Indian Ocean branch
4. Pacific Ocean branch

Answer: 1. Bay of Bengal branch

Question 13. The slope of the Khasi-Jaintia hills, on which Shillong is located, is the

1. Northern slope
2. Eastern slope
3. Southern slope
4. Western slope

Answer: 1. Northern slope

Question 14. The part of the hill that experiences relief rainfall is the

1. Windward slope
2. Speak
3. Leeward slope
4. Foothills

Answer: 1. Windward slope

Class 8 Geography Solution WBBSE

Question 15. Rainfall that occurs when a warm air mass meets a cold air mass, and the warm, less dense air is pushed up over the cold, dense air is called-

1. Convectional rainfall
2. Orogenic rainfall
3. Drizzle
4. Frontal rainfall

Answer: 4. Frontal rainfall

Question 16. Frontal rainfall is observed in the

1. Equatorial regions
2. Temperate regions
3. Polar regions
4. Tropical regions

Answer: 2. Temperate regions

Question 17. ‘Ashwiner Jhar’ in West Bengal is an example of-

1. Local rainfall
2. Relief rainfall
3. Convectional rainfall
4. Cyclonic rainfall

Answer: 4. Cyclonic rainfall

Question 18. The rainfall that is commonly associated with thunderstorms is-

1. Drizzle
2. Convectional rainfall
3. Cyclonic rainfall
4. Relief rainfall

Answer: 2. Convectional rainfall

Question 19. Rainfall due to the effect of temperate cyclones is observed in-

1. Western India
2. Central Europe
3. Eastern India
4. Southern India

Answer: 2. Central Europe

Question 20. Tropical cyclones are formed in-

1. 5°-20° latitudes
2. 35°-60° latitudes
3. 20°-35° latitudes
4. 60°-80° latitudes

Answer: 1. 5°-20° latitudes

Question 21. The Kalbaishakhi rain that occurs in April and May in India is an example of

1. Convectional rainfall
2. Orographic rainfall
3. Cyclonic rainfall
4. Rainfall due to the formation of the anticyclonic condition

Answer: 1. Convectional rainfall

Question 22. The unit that measures rainfall is-

1. Celsius
2. Millibar
3. Centimetre
4. Pascal

Answer: 3. Centimetre

Question 23. The instrument used to measure rainfall is known as

1. Altimeter
2. Barometer
3. Anemometer
4. Rain Gauge.

Answer: 4. Rain Gauge.

Question 24. A line on a map connecting places having the same amount of rainfall in a given period is known as-

1. Isotherm
2. Isobar
3. Isohume
4. Isohyet

Answer: 4. Isohyet

Question 25. ‘Ashwiner Jhar’ occurs in

1. January
2. April
3. July
4. October

Answer: 4. October

 

Chapter 5 Topic B Precipitation Very Short Answer Type Questions Fill In The Blanks

Question 1. _______ is the phenomenon by which water in its solid and liquid forms falls to the ground from clouds due to gravity.
Answer: Precipitation

Question 2. Tiny water droplets condense to form clouds, which keep growing till they become too heavy to remain suspended in the atmosphere and then fall from the sky as _______, due to gravitational pull.
Answer: Rain

Question 3. _______cyclones typically form over large bodies of relatively warm water.
Answer: Tropical

Question 4. A relative humidity of 100% indicates that the air is _______ with water.
Answer: Saturated

Question 5. _______ rainfall occurs when moist air rises as it moves over a mountain range.
Answer: Orographic

Question 6. The area to the north of Meghalaya Plateau is a _______ area.
Answer: Rainshadow

Question 7. West Bengal experiences spells of heavy convectional rain during the _______ afternoons.
Answer: Summer

Question 8. The highest amount of rainfall in the world is recorded in _______.
Answer: Mawsynram

Question 9. The foothills of the eastern Himalayas _______ experience rainfall.
Answer: Orographic

Question 10. The southwest monsoons strike the western coast of India and cause heavy rainfall on the _______ slope of the Western Ghats.
Answer: western

Question 11. The western slope of the Western Ghats experiences _______ type of rainfall.
Answer: Orographic

Question 12. A high _______ content is necessary for precipitation.
Answer: Water vapour

Question 13. The western disturbances over the northern Indian subcontinent are actually _______ cyclones.
Answer: Temperate

Question 14. One of the rainshadow areas in India is _______on the Meghalaya plateau.
Answer: Shillong

Question 15. _______ refers to a kind of fog that has soot or smoke particles.
Answer: Smog

Question 16. Most thunderstorms occur from _______ clouds.
Answer: cumulonimbus

Class 8 Geography Solution WBBSE

Write True Or False

Question 1. Rain helps to cool down the weather.
Answer: True

Question 2. Cyclonic rainfall in temperate regions occurs during the winter season.
Answer: True

Question 3. The moisture retention capacity of warm air is lower.
Answer: False

Question 4. Tropical cyclones become weak while moving on the landmasses.
Answer: True

Question 5. The wettest places on the earth are usually located in the Equatorial region.
Answer: False

Question 6. Cyclonic rainfall is most common in the Equatorial region.
Answer: False

Question 7. Rain is the most common form of precipitation.
Answer: True

Question 8. Convectional rain occurs on the earth’s surface when a conditionally unstable or moist atmosphere becomes heated more than its surroundings, leading to significant evaporation.
Answer: True

Question 9. All types of clouds lead to rainfall.
Answer: False

Question 10. Most of the rainfall in India is a result of orographic rainfall.
Answer: True

Question 11. Convectional rainfall is more common in high latitudes.
Answer: False

WBBSE Chapter 5 Topic B Precipitation Match The Columns

1.

Answer: 1. C, 2. D, 3. B, 4. E, 5. A

 

Answer In One Or Two Words

Question 1. By which process does the air heat up in case of convectional rainfall?
Answer: Convection.

Question 2. Name two countries that experience convectional rainfall throughout the year.
Answer: Uganda, Indonesia.

Question 3. Name a rainshadow region in India.
Answer: Deccan Plateau.

Question 4. Which slope of the mountain receives less rainfall?
Answer: Leeward slope.

Question 5. How many types of cyclonic rainfall are there?
Answer: Two.

Question 6. By what name is the autumn cyclone called in West Bengal?
Answer: Aswiner Jhar.

Question 7. What type of rainfall is observed in India during autumn?
Answer: Cyclonic rainfall.

Question 8. Which type of cyclone persists for a long time?
Answer: Temperate cyclones.

Question 9. Name the strongest tropical cyclone in the world.
Answer: Tornado.

Class 8 Geography Solution WBBSE

Chapter 5 Topic B Precipitation Conceptual Questions And Answers Who am I?

Question 1. I am the highest cloud. I look like a mare’s tail. I create a remarkable spectrum during the sunset. However, I do not cause rainfall.’ Who am I?
Answer: Cirrus cloud

Question 2. ‘I am a vertical, dome-shaped cloud. I cause rainfall with thunderstorms.’-Who am I?
Answer: Cumulonimbus cloud

Question 3. I am born from water due to insolation. I am light and I float in the air. I form clouds and fog.’ Who am I?
Answer: Water vapour

Question 4. I occur in the regions that have a higher percentage of water bodies and which receive vertical rays of the sun.’ -Who am I?
Answer: Convectional rainfall

Question 5. ‘I stay at the centre of a cyclone. The sky in my area remains clear and calm but my surroundings experience storms.’ -Who am I?
Answer: Eye of a cyclone

Question 6. I drop down as a solid substance from clouds instead of raindrops due to the extremely cold weather.’ Who am I?
Answer: Snow

Question 7. ‘You can see me in early winter mornings. I bar your visibility. I am almost like smoke.’ -Who am I?
Answer: Fog

Question 8. I stick on the blades of grass like tiny droplets of water, early in the morning. I am mostly seen in winter.’-Who am I?
Answer: Dew

Scrambled Words

1. MLUCO UNBIASED
2. UROICR MLUSUC
3. PEH CARURJNI
4. LFNWASLO

Answers:

1. CUMULONIMBUS
2. CIRROCUMULUS
3. CHERRAPUNJI
4. SNOWFALL

Fill Up The Blanks In The Knowledge Hive

Question 1. Fill in the knowledge hive with information on the cumulonimbus cloud.

 

Answers:

1. It is a vertical cloud.
2. It is dome-shaped and greyish or black in colour.
3. This cloud sometimes causes hailstorms also.
4. This cloud causes heavy rainfall along with thunderstorms.
5. This cloud is also called a thundercloud.

 

Chapter 5 Topic B Precipitation Strike the odd one out

Question 1. Cirrus, Cirrostratus, Cirrocumulus, Stratus
Answer: Stratus (not a high cloud)

Question 2. Stratus, Stratocumulus, Cirrus, Nimbostratus
Answers: Cirrus (not a low cloud)

Question 3. Convectional rainfall, Torrential rainfall, Cyclonic rainfall, Orographic rainfall
Answers: Torrential rainfall (not a type of rainfall)

Question 4. Snowfall, Dew, Sleet, Hailstorm
Answers: Dew (not a type of precipitation)

 

Correct The Following

1. The cirrus clouds appear like the scales of a mackerel fish.

2. Cumulus cloud is also known as a thundercloud.

3. The process by which water changes from liquid to vapour is known as condensation.

4. Hailstorm is a mixture of water droplets and snowflakes.

Answers:

1. Cirrocumulus
2. Cumulonimbus
3. Evaporation
4. Sleet

Crossword

 

CLUES

Down:

1. Place that gets the highest amount of rainfall in the world.
2. This type of cyclones occur in the mid-latitudes in winter.
3. Rainfall is produced when moist air moves up the sides of hills and mountains.

Across:

4. Phenomenon of moisture falling on ground from clouds due to gravity.
5. Cyclonic storm in the South China Sea.
6. Imaginary line joining places having equal amounts of rainfall.

Answers:

Down: 1. MAWSYNRAM, 2. TEMPERATE, 3. OROGRAPHIC
Across: 4. PRECIPITATION, 5. TYPHOON, 6. ISOHYET

 

Chapter 5 Topic B Precipitation Advanced Questions And Answers

Question 1. Write a short note on smog.
Answer:

Smog:-

Fog mixed with smoke is called smog. It is a consequence of air pollution and is very harmful for the living world. Industrial towns emit poisonous gases from factories which combine with the fog to form smog.

The cities of London and Los Angeles suffer from deadly smog during winter evenings.

Question 2. What are nor’westers?
Answer:

Nor’wester:-

It is a kind of abrupt or sudden wind that causes rainfall with thunder, lightning and hail at times, in the summer afternoons in eastern India, including West Bengal and its adjacent areas.

As the wind comes from the northwest, it is called the Nor’wester. This rainfall is also known as ‘Kalbaishakhi’.

Question 3. What are Western disturbances?
Answer:

Western Disturbances:-

During winter February), India enjoys sunny and pleasant weather conditions because of the sun’s apparent annual migration to the southern hemisphere after September 23.

Due to the shifting of wind belts along with climatic belts, the Mediterranean region comes under the influence of the westerlies that cause cyclones and heavy rain.

This rain and storm that comes from the west in winter is called ‘western disturbances. Under the influence of the western disturbances, Jammu and Kashmir, Himachal Pradesh, Uttarakhand, western UP, Haryana and Punjab receive this type of winter rainfall.

This winter rain is beneficial for the cultivation of wheat in Punjab.

Question 4. Why is the Bay of Bengal more prone to cyclones than the Arabian Sea?
Answer:

Bay of Bengal more prone to cyclones than the Arabian Sea:-

The reasons for Bay of Bengal being more prone to cyclones than the Arabian Sea are as follows-

1. The Arabian Sea has a greater expanse of water than the Bay of Bengal, which is rather restricted by land on three sides. So, the Bay of Bengal retains heat for a longer time. As a consequence, it creates a low-pressure zone, which gives rise to cyclones.
2. The water of the Bay of Bengal is denser than that of the Arabian Sea. Due to the lack of suitable conditions, the bay water cannot lose heat quickly. So, a higher atmospheric temperature leads to the formation of a low-pressure zone, which further leads to the occurrence of cyclones.

The Bay of Bengal is thus more prone to cyclones than the Arabian Sea.

 

Chapter 5 Topic B Precipitation Formative

 

Participation

This segment will indicate how much the students have actively participated and taken the initiative during the class.

The heat of the sun is responsible for the formation of water vapour from waterbodies. Since water vapour is lighter than air, it rises and accumulates to form clouds. With reference to this information, answer the following:

Question 1. Apart from the sun’s heat, what else is responsible for the formation of water vapour?
Answer: Moisture is added to the atmosphere due to the transpiration process in plants.

Question 2. What is the relation between cloud formation and rainfall?
Answer: Clouds filled with water vapour cause rainfall on Earth due to gravity.

Question 3. How many types of rainfall are there?
Answer: There are three types of rainfall.

Question 4. Which instrument is used to measure the amount of rainfall?
Answer: Rain gauge.

 

Interpretation And Application

This segment will test whether the students have understood the topics, or whether they are just mugging up.

Question 1. Take some water in a glass plate and a glass jar and keep them exposed to the weather. What change will be observed in the amount of water kept in the two vessels after two or three days?
Answer:

If we take some water in a glass plate and a glass jar and keep them exposed to the weather, we will see the amount of water has changed. Both the glass plate and the glass jar will have a lesser amount of water than it was kept in them earlier.

But the water in the glass jar will be more than the glass plate. The glass plate having a flat area, Fig. Set up for the experiment gets more sunlight, hence more water will evaporate from its surface.

 

 

On the other hand, the glass jar having a narrow mouth, less amount of water will be evaporated from it. Thus it can be said that the rate of evaporation depends on the area of the upper surface of the water bodies.

Question 2. Keep a few cubes of ice in a tumbler. After a while, droplets of water accumulate on the tumbler. Your hands get wet when you hold the tumbler. Air around the tumbler has cool down on its contact and the water vapour in it becomes a water droplets. Which process does this happen as a result of?
Answer:

It is observed that if some ice cubes are kept in a glass, water droplets accumulate outside the glass. When the air around the cold glass comes into contact with it, the water vapour accumulates on the glass surface as water droplets.

Thus, on holding the glass, our hands get wet. This process is known as condensation. This is how clouds form.

 

 

Question 3. Prepare a model of orographic rainfall and point out windward and leeward slopes. ▸ Materials required: Thermocol, knife, gum, cotton, colour, painting brush, several thin sticks, pen.
Answer:

Model-making:

With the help of these materials, the model can be prepared following the steps given below-

Stage-1:

A big sheet of thermocol is taken and cut into rectangular shapes. Then with the help of gum, they are fixed, one above the other.

Stage-2:

When the gum dries up, with the help of a knife, shapes of waterbody, landmasses and mountains are made on them. (As shown in the picture.)

Stage-3:

After that, blue colour for a waterbody, yellow for a landmass and grey for the mountain are used to paint the surface.

Stage-4:

Now using those thin sticks and glue, clouds are made with cotton. Those cotton are painted grey to make it look as original cloud.

Stage-5:

Small pieces of thermocouple are cut. ‘Ocean’, landmass’, ‘windward slope’ and ‘leeward slope’ are written on paper individually and fixed on the pieces of thermocol. Now with sticks those clouds are fixed where they are necessary.

 

 

Questioning And Experimentation

This segment will investigate the student’s understanding of the subject,

Question 1. Among all the clouds that you have come to know, note down the types you observe in the sky against the dates on which you see them.
Answer:

I am Samir Rehman, a resident of Howrah. The clouds that I could identify in the sky are-

1. Cirrus cloud: 26 October, 29 September.
2. Cirrostratus cloud: 11 July, 6 August, 21 September, 1 October.
3. Cirrocumulus cloud: 7 October, 10 October, 14 November, 19 November, 3 December, 4 December
4. Altostratus cloud: 7 July, 8 July.
5. Altocumulus cloud: 16 October, 19 October
6. Stratocumulus cloud: 12 October, 14 October
7. Stratus cloud: 29 June, 30 June, 1 July, 2 July
8. Nimbostratus cloud: 3 July-5 July, 14 August-16 August
9. Cumulonimbus cloud: 14 April-18 April, 26 April, 2 May, 11 May, 19 May

Aesthetics And Creativity

This segment will check the aesthetic sense and creativity of the students.

Question 1. Hand-made clouds: Try to form clouds in your own home.
Answer:

Materials:

1. A plastic bottle of 1-litre capacity,
2. Hot water (not boiling),
3. Matchsticks.

Process:

1. The lower portion of the bottle is filled with hot water.
2. A lighted matchstick is put inside the bottle and made sure that the bottle is filled with smoke.
3. Then the lid is put on the bottle and closed.
4. Finally, pressure is put on the bottle using hands a few times. Once that is done, it is observed that a cloud has formed within the bottle.

 

 

Reasons:

1. Hot water in the bottle increases the moisture-retaining capacity of the air within the bottle.
2. The temperature of the matchstick helps the air inside the bottle to saturate.
3. When air containing water vapour cools down a bit, the water vapour within it transforms into tiny water droplets and floats around. These together make up the cloud inside the bottle.