WBBSE Solutions For Class 8 Geography Chapter 5 Cloud And Rain Topic A Cloud

Chapter 5 Cloud And Rain Synopsis

Clouds are defined as the aggregate of numerous tiny water droplets around dust particles or a mixture of both in the air above the ground surface. Generally, the diameter of the water droplets in clouds is 0.02 mm or less.

The clouds which occur at an average minimum height of 20000ft are known as high clouds. This cloud group consists of cirrus, cirrostratus and cirrocumulus.

Cirrus clouds are whitish transparent, light and feathery clouds, through which the sun, the moon are visible.

Cirrostratus clouds are generally white in colour and are spread in the sky like thin, white film. The clouds often form a halo around the sun or the moon.

Cirrocumulus clouds appear in the sky as cotton wool and make the sky look like the scales of a mackerel fish. The cloud indicates fair weather.

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The location of medium clouds in the sky varies between 6500ft to 20000ft. This group consists of altostratus and altocumulus clouds.

Altostratus clouds, having the fibrous appearance, grey to bluish in colour yield widespread and continuous rainfall. The sun seems dull through these clouds.

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Altocumulus clouds are characterised by wavy patterns, flat, rounded structures and white to greyish colour. The sky is visible through the gaps in these cloud masses.

Low clouds are found up to a height of 6500ft from the ground. Stratocumulus, stratus, and nimbostratus clouds come under this group.

Stratocumulus clouds are layered clouds appearing like a heap. These are also called Bumpy clouds as the layers seem to be rolling along the sky.

Stratus clouds are low-altitude, grey-coloured, fog-like clouds. These clouds pose great difficulty to mountaineers and pilots. These clouds can sometimes cause drizzle.

Nimbostratus clouds are associated with continuous and copious precipitation. They are thick, dense, grey to black in colour and indicate bad weather.

Vertical clouds are usually found at an average minimum height of 16000 ft. They consist of cumulus and cumulonimbus clouds.

Cumulus clouds are thick, and dense with a high vertical extent. The top surface is white and irregular and the bottom part is black and flat. These clouds generally fair indicate fair weather.

Cumulonimbus clouds show great vertical development and produce heavy rains or hailstorms accompanied by thunderstorms. The clouds may be whitish-grey or black in colour and dome-shaped. The top and bottom parts of these clouds are flat.

The process of conversion of water into its gaseous form, i.e., water vapour is called evaporation.

When the temperature of moist air reaches the dew point, it becomes saturated. In other words, air having 100% relative humidity is called saturated air.

The temperature at which a mass of air becomes saturated is called its dew point.

The process of conversion of water vapour into water droplets is called condensation.

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.

The major forms of precipitation include rainfall, drizzle, sleet, hail and snow.

During cloud formation, the water vapour present in the atmosphere condenses to form larger droplets of water. These droplets fall on the earth due to gravitational pull.

This is called rainfall. There are mainly three types of rainfall- convectional rainfall, orographic rainfall and cyclonic rainfall.

The relative humidity is defined as the ratio of the amount of water vapour actually present in a fixed volume of air at a particular temperature and the maximum amount of water vapour that the volume of air can hold at that temperature.

Cherrapunji in Meghalaya, being situated on the windward slope receives a mean annual rainfall of 11777mm.

Cyclonic or frontal rainfall is always associated with cyclones.

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A tropical cyclone generally occurs between 5 and 20° latitudes in both hemispheres. The innermost part (or centre) of this cyclone is known as the eye of the cyclone.

Aila, Phailin, Fani and Hudhud are some are notable examples of tropical cyclones that have occurred in recent times.

A temperate cyclone occurs when two different air masses (warm and cold) converge in the temperate region. The mid-latitude countries experience rainfall mainly in winter due to this type of cyclone.

When very tiny droplets of water (less than 0.5mm in diameter) come down to the surface of the earth as rain, it is called as a drizzle.

Sleet refers to the combined precipitation of water droplets and ice.

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.

Snowfall is common in regions with cold climates or in high mountainous areas, where temperatures are below freezing point.

Dew falls on leaves and blades of grass mainly in winter nights. A cloudless sky and calm weather are the necessary conditions for dew formation.

When water vapour condenses around the tiny dust particles present in air near the ground and appears like smoke, it is called fog. It generally occurs in winter and reduces horizontal visibility.

A rain gauge (also known as a udometer, pluviometer or ombrometer) is an instrument that is used to measure the amount of rainfall.

A line on a map (usually, a weather map) connecting points having an equal amounts of rainfall in a given period is known as isohyet.

Chapter 5 Topic A Clouds Analytical Type Questions

Question 1. What are clouds? How are they formed?
Answer:

Clouds:

Clouds are defined as the aggregate of numerous tiny water droplets around dust particles or a mixture of both in the air above the ground surface. Generally, the diameter of the water droplets in clouds is 0.02 mm or less.

 

 

Stages of cloud formation:

According to climatologists, clouds form through various stages. These are discussed below-

1. Evaporation:

Water from various water bodies changes to water vapour by solar insolation. Water vapour, being lighter than air, rises to the higher layers of the atmosphere.

In addition to this, moisture discharged by trees and plants during transpiration is added to the atmospheric water vapour content.

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2. Condensation:

Condensation of water vapour takes place at this stage mainly at higher altitudes, when it comes into contact with cooler air. The cooler the air, the lower is its capacity to hold moisture.

Eventually, the temperature of the moist air mass reaches its dew point and the air gets saturated. When the temperature falls below the dew point, the finer water particles combine to form droplets of water or snow.

3. Clouds and precipitation:

The tiny droplets of water and snow, while floating in the sky, settle around existing. dust particles, pollen grains and other impurities in groups or patches and float in the air to form clouds.

Precipitation from these clouds occurs when they are unable to hold the moisture any further and the water flows back into the water bodies.

Question 2. Discuss the different types of high clouds or high-altitude clouds.
Answer:

Different Types Of High Clouds Or High-Altitude Clouds:-

Normally, high clouds or high altitude clouds are on average found at a minimum height of 20000 ft above the surface of the earth.

There are three subdivisions of high-altitude clouds

1. Cirrus
2. Cirrocumulus and
3. Cirrostratus.

1. Cirrus:

The features of these clouds are

1. This type of cloud are found at maximum height and resembles feathers or fluffs of cotton or at times the tail of a mare.
2. Cirrus, being formed of tiny ice crystals, is white and transparent.
3. This cloud creates a marvellous spectrum with the light of the setting sun.
4. These clouds do not cause rainfall and denote clear weather. But when these clouds accumulate into a compact mass the weather deteriorates. If cirrostratus clouds form after this, it may also indicate an approaching storm.

2. Cirrocumulus:

The features of these clouds are

1. They are spherical in shape.
2. Formed of very minute ice particles, these clouds look like waves or bunches of white sheets floating in the sky.
3. When the entire sky gets covered with such scale-like clouds, it is called ‘mackerel sky’.
4. This cloud indicates a clear sky without any hint of rain.

3. Cirrostratus:

The features of these clouds are

1. They are milky white in colour.
2. Sometimes, halos around the sun and the moon are formed by these clouds.
3. It floats high up in the sky, forming a thin white film.
4. It also forms the rainbow.
5. It indicates an approaching storm.

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Question 3. Classify the medium clouds air, and middle altitude clouds.
Answer:

Classification The Medium Clouds Air, And Middle Altitude Clouds:-

Medium clouds or middle altitude clouds extend from 6500 ft-20000 ft in the sky.

There are two types of middle-altitude clouds

1. Altostratus and
2. Altocumulus.

1. Altostratus:

Another name for these clouds is layered clouds. The features of these clouds are

1. These may look grey to bluish in colour.
2. These clouds have a fibrous appearance.
3. These clouds are usually visible in the morning or afternoon. hours. The sun seems dull through these clouds.
4. Rainfall occurs for a long period and over a large area from these clouds.

2. Altocumulus:

The features of these clouds are

1. They look like round, rough-edged, soft balls of wool making wavy patterns in the sky.
2. The blue sky is visible through. the gaps in these clouds.
3. Their colour varies from white to grey.
4. The presence of these clouds in the sky indicates clear weather, but if they gather together, they may cause rain.

 

Question 4. Give a description of the different types of low clouds or low-altitude clouds.
Answer:

Different Types Of Low Clouds Or Low-Altitude Clouds:-

Low clouds or low altitude clouds are found up to a height of 6500 ft.

These are of three types

1. Stratocumulus
2. Stratus and
3. Nimbostratus.

1. Stratocumulus:

1. These are also called lower clouds. The features of these clouds are
2. Their colour varies from dark grey to black.
3. At the middle altitude, altocumulus clouds become heavier and darker and sink down to form stratocumulus clouds.
4. These are dome-shaped clouds arranged in layers looking like a heap. These are also called Bumpy clouds as the layers seem to be rolling along the sky.
5. These clouds are active and they keep moving.
6. During winter, in temperate regions, these clouds often cause heavy rainfall.

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2. Stratus:

These are arranged in layers. The features of these clouds are

1. These are grey or white in colour.
2. These create visibility problems mainly for pilots and mountaineers.
3. These look like a thick fog.
4. This type of cloud sometimes causes drizzle.

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Nimbostratus:

They are also called rain-bearing clouds. The features of these clouds are

1. These are grey or black in colour.
2. These are dense and thick clouds that cover the sky in the rainy season.
3. These clouds do not have any particular shape.
4. They cause heavy rainfall but without any thunder and lightning.
5. These may also cause hailstorms and continuous rain.

Question 5. Describe the vertical clouds.
Answer:

Vertical Clouds:-

Vertical clouds are those which are. vertically developed to a great extent. The minimum height of these clouds is 16000ft on average. These clouds look almost like trees.

These are of two types

1. Cumulus and
2. Cumulonimbus.

1. Cumulus:

These are mound-like clouds. The features of these clouds are

1. These form as a result of the rising of water vapour and condensation in the higher layers of the atmosphere.
2. The bottom of these clouds are almost flat, but the tops are irregular and undulating and resemble a cauliflower.
3. The lower parts of these clouds are dark grey or black, but the upper parts are white.
4. These are dense, thick clouds.
5. These have a ‘silver lining’ on the top.
6. They indicate clear weather.

2. Cumulonimbus:

These are rain-bearing clouds. The features of these clouds are

1. Cumulus clouds become cumulonimbus after gaining height.
2. These clouds sometimes reach about a height of 12000ft from the surface.
3. The bottom and middle portions of these clouds are black, but the sides are white or grey.
4. These clouds are whitish-grey or black in colour and dome-shaped.
5. The top and bottom parts of these clouds are flat.
6. These clouds are visible at the time of Nor’wester in the north-western sky.
7. These cause heavy rainfall, violent thunderstorms and sometimes even hailstorms. Thus, they are also called thunderclouds. Usually, cloudbursts are associated with these clouds.

Chapter 5 Topic A Clouds Analytical Type Questions Short Analytical Type Questions

Question 1. Classify the different types of clouds.
Answer:

Clouds are classified

1. According to their heights and
2. According to their shapes and formation.

1. According to height, there can be

1. High altitude (20000 ft high from the earth’s surface) clouds,
2. Middle altitude (6500 ft-20000 ft high from the surface) clouds, and
3. Low altitude (up to 6500 ft high from the surface) clouds.

2. According to shape and formation

There can be four classes of clouds. These are

1. Cirrus, a high-altitude cloud that looks like feathers,
2. Stratus, a low-altitude fog-like cloud,
3. Cumulus, a cloud that looks like a mound of fluffy cotton,
4. Cumulonimbus, a rain-bearing cloud that gives plenty of rainfall.
5. These four types of clouds can be found in combined stages too. For example, cirrocumulus and cirrostratus belong to the high-altitude clouds group, altocumulus and altostratus belong to the middle-altitude clouds group, and stratocumulus and nimbostratus belong to the low-altitude clouds group. Cumulus and cumulonimbus can be found at any height.

Question 2. What do you understand by saturated air?
Answer:

Saturated Air:-

Air is said to be saturated when it contains the maximum amount of moisture it can hold at a given temperature. The upper limit of absorbing water vapour depends on the temperature of air.

If the temperature increases, the capacity of air to hold moisture also increases and vice versa. For example, at 25°C, 1cc air can hold 30gm of moisture at the most.

If it actually contains 30 gm of moisture at 25°C, then it will be called saturated air, but if that volume of air has 15 gm of moisture under the same conditions, it will be called unsaturated air.

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Features of saturated air include

1. It can hold the maximum amount of water vapour at a given temperature.
2. Atmospheric temperature needs to reach the dew point so that the air becomes saturated.
3. Saturated air plays a very significant role in causing rainfall and snowfall.

Question 3. Why is the amount of water vapour in air different in different areas?
Answer:

The Amount Of Water Vapour In Air Different In Different Areas:-

The variation in the amount of water vapour depends on the following conditions-

1. Waterbodies:

The location of a greater number of water bodies in an area helps in the rapid and widespread evaporation of water, if the temperature over there is favourably high.

Example-The equatorial region records maximum humidity.

2. Sun rays:

The angular distance of the sun’s rays is another important factor because the vertical rays of the sun heat up a particular place more intensely than the Islanting or oblique ones.

Example-The polar regions have very little evaporation.

3. Natural vegetation:

The extent of natural vegetation or forests is an important factor as well. Trees, shrubs and bushes transpire and a lot of vapour is emitted in this process.

Example-The equatorial evergreen forests have dense fog-like vapours in the atmosphere, while the deserts have very dry weather due to the absence of vegetation.

Question 4. Differentiate between evaporation and condensation.
Answer:

The differences between evaporation and condensation are

 

Question 5. Differentiate between dew point and freezing point.
Answer:

The differences between dew point and freezing point are-

 

Question 6. How important are clouds as a component of climate?
Answer:

Clouds As A Component Of Climate:-

Clouds are an important component of the climate of a region.

This is due to the following reasons

1. Rainfall is not possible without cloud cover even though all clouds do not cause rainfall.
2. If there are clouds in the sky during the daytime, the temperature decreases, since the sun’s rays cannot reach the earth’s surface.
3. The cloudless sky during day and cloudy sky at night cause a rise in temperature.
4. Clouds are responsible for maintaining a balance in the temperature of the atmosphere.

Question 7. Why is a cloudy night hotter than a cloudless one?
Answer:

Cloudy Night Hotter Than A Cloudless One

The earth’s surface receives solar energy during the day and gets heated by the processes of conduction, convection and radiation. At night, the atmosphere becomes cooler by discharging this heat to outer space (in the absence of the sun).

But if the sky has a cloud cover at night, it has a blanketing effect on the earth. This retains the heat inside the atmosphere, thereby making the night warmer than a cloudless one.

On the other hand, a cloudless sky allows the outward radiation of heat from the earth’s surface, making the night cooler.

 

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Question 8. What are the effects of the presence of water vapour in the atmosphere?
Answer:

Effects Of The Presence Of Water Vapour In The Atmosphere:-

The effects of the presence of water vapour in the atmosphere are-

1. Clouds are created from water vapour.
2. Air containing water vapour is lighter than dry air. Thus, it helps in creating regions of low air pressure.
3. Air filled with water vapour absorbs heat.
4. Excess water vapour in the atmosphere makes the air humid. This humid air makes human beings uncomfortable.
5. When water vapour in air condenses and causes rainfall, some amount of heat is released by it. This heat automatically leads to an increase in the temperature of the atmosphere.

Question 9. Put a kettle or container of water on the burner and heat it. After some time white steam will be seen coming out of the nozzle or top of the kettle or container. What actually is this steam?
Answer:

The water, on boiling, forms water vapour within the kettle, which rises and puts pressure under the lid of the kettle or comes out through the mouth of the kettle as white smoke.

If you put your palm over that smoke, you will see tiny water droplets accumulating on your skin.

Chapter 5 Topic A Clouds Analytical Type Questions Short Answer Type Questions

Question 1. What are clouds?
Answer:

Clouds:-

Clouds are defined as the aggregate of numerous tiny water droplets around dust particles or a mixture of both water droplets and dust particles, in the air above the ground surface. Generally, the diameter of the water droplets in clouds is 0.02mm or less.

Question 2. What is oversaturated air?
Answer:

Oversaturated Air:-

If, at a given temperature, a fixed volume of air contains more water vapour than what is required to make it totally saturated, it is called oversaturated air.

Question 3. What is unsaturated air?
Answer:

Unsaturated Air:-

When, at a particular temperature, a fixed volume of air contains less water vapour than what is required by it to become saturated, it is called unsaturated air.

This kind of air has the capacity to hold more water vapour if its temperature increases.

Question 4. When does air become saturated?
Answer:

Air Become Saturated:-

Air has the capacity to hold water vapour and its water-holding capacity depends on its temperature. The moisture content increases or decreases with an increase or decrease in temperature.

A volume of air becomes totally saturated when it holds moisture to its maximum capacity. Saturated air has 100% relative humidity.

WBBSE Class 8 Geography Chapter 5

Question 5. What is dew point?
Answer:

Dew Point:-

The temperature at which a mass of air becomes saturated is called its dew point. At the dew point, air gets totally saturated and cannot hold any more moisture, or rather, water vapour changes into water droplets to cause precipitation, at dew point.

Question 6. What is condensation?
Answer:

Condensation:-

The process of conversion of water vapour into water droplets is called condensation. When saturated air cools down further, the water vapour in it condenses to form small droplets of water.

Question 7. What is vaporisation?
Answer:

Vaporisation:-

The process by which water from oceans, seas, rivers, lakes, ponds, reservoirs, etc., changes into vapour due to solar insolation, is called vaporisation.

Question 8. What is latent heat?
Answer:

Latent Heat:-

Latent heat is the heat required to convert the physical state of matter without any change in temperature, such as solid to liquid, liquid to gas, gas to liquid and again liquid to solid.

Example-Temperature of boiling water at 100°C remains constant until the last drop of water evaporates. This is because all the heat being added to the liquid is absorbed as latest heat of vapourisation and carried away by the vapour molecules.

Chapter 5 Topic A Clouds Analytical Type Questions Multiple Choice Questions Choose The Correct Option

Question 1. Cirrus clouds appear like-

1. Light feathers
2. Cotton wool
3. Clumpy layers
4. Mackerel sky

Answer: 1. Light feathers

Question 2. According to height, cirrocumulus clouds are grouped under-

1. High altitude clouds
2. Middle altitude clouds
3. Low altitude clouds
4. Vertical clouds

Answer: 1. High-altitude clouds

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Question 3. According to height, stratocumulus clouds are grouped under-

1. High altitude clouds
2. Middle altitude clouds
3. Low altitude clouds
4. Vertical clouds

Answer: 3. Low-altitude clouds

Question 4. Thunderclouds are otherwise known as-

1. Altostratus
2. Cirrocumulus
3. Cirrus
4. Cumulonimbus

Answer: 4. Cumulonimbus

Question 5. The cloud that forecasts continuous rain is-

1. Altostratus
2. Altocumulus
3. Cumulonimbus
4. Cirrus

Answer: 1. Altostratus

Question 6. Nimbostratus clouds indicate whether that is-

1. Calm
2. Likely to drizzle
3. Bad
4. Likely to have heavy rainfall

Answer: 3. Bad

Question 7. The cloud known by Mackerel Sky is-

1. Cirrocumulus
2. Altocumulus
3. Stratus
4. Cumulonimbus

Answer: 1. Cirrocumulus

Question 8. The colour of Altostratus cloud is generally-

1. Yellowish
2. Violet
3. Milky white
4. Bluish-grey

Answer: 4. Bluish-grey

Question 9. The type of cloud generally associated with convectional rainfall is-

1. Cumulus
2. Cirrus
3. Cumulonimbus
4. Cirrocumulus

Answer: 3. Cumulonimbus

WBBSE Class 8 Geography Chapter 5

Question 10. The changing of water from gaseous form to liquid form is known as-

1. Rainfall
2. Condensation
3. Vapourisation
4. Precipitation

Answer: 2. Condensation

Question 11. Air that contains maximum amount of moisture that it can hold at particular temperature is known as-

1. Saturated air
2. Monsoon wind
3. Unsaturated air
4. Supersaturated air

Answer: 1. Saturated air

Question 12. The temperature at which air becomes saturated is known as-

1. Freezing point
2. Cthermal capacity
3. Dew point
4. Heat

Answer: 3. Dew point

Very Short Answer Type Questions Fill In The Blanks

Question 1. __________ is a visible mass of condensed water vapour floating in the atmosphere, typically high above the ground.
Answer: Cloud

Question 2. __________ clouds appear in the sky as sand ripples in the desert.
Answer: Cirrocumulus

Question 3. Clouds are mainly seen in the __________ layer of the atmosphere.
Answer: Troposphere

Question 4. The __________ cloud sometimes spreads out on top to form an ‘anvil head.
Answer: Cumulonimbus

Question 5. __________ clouds are sometimes called as ‘sheep clouds’ or ‘wool-pack clouds.
Answer: Altocumulus

Question 6. Cooler air has __________ capacity of retaining water vapour.
Answer: Less

Question 7. When air is __________, it cannot hold any more water vapour.
Answer: Saturated

WBBSE Class 8 Geography Chapter 5

Question 8. Water vapour in air __________ to form fog, a natural weather condition.
Answer: Condenses

Question 9. The process by which heat from the sun turns water from the surface of lakes and oceans into water vapour is known as __________.
Answer: Evaporation

Question 10. The __________ is the temperature at which the water vapour in a sample of air at constant barometric pressure condenses into water.
Answer: Dew point

Question 11. Water vapour releases latent heat into the atmosphere when it __________ to form clouds.
Answer: Condenses

Question 12. As water vapour condenses to form clouds, it releases __________ heat into the atmosphere.
Answer: Latent

Question 13. Water from the surface of lakes, rivers, seas __________ and oceans rises in the atmosphere.
Answer: vapourises

Question 14. When moisture-laden air moves up, its __________ and __________ decrease.
Answer: Temperature, pressure

WBBSE Class 8 Geography Chapter 5

Chapter 5 Topic A Clouds Analytical Type Questions Write True Or False

Question 1. Clouds are very significant because all forms of precipitation occur from them.
Answer: True

Question 2. Nimbostratus are high clouds with detached segments.
Answer: False

Question 3. Cirrus clouds are indicative of a long period of precipitation.
Answer: False

Question 4. Stratocumulus clouds are also known as bumpy clouds.
Answer: True

Question 5. Altostratus clouds are indicative of widespread, continuous precipitation.
Answer: True

Question 6. The process of condensation begins only when the relative humidity of ascending air becomes 50%.
Answer: False

Question 7. Generally, water droplets in clouds are macroscopic in size.
Answer: False

Question 8. Halos around the sun and the moon are visible due to the presence of cirrostratus clouds.
Answer: True

Question 9. Temperature and humidity of air are directly related.
Answer: True

Question 10. The process of conversion of solids directly to the gaseous state is called sublimation.
Answer: True

Match The Columns

1.

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

WBBSE Class 8 Geography Chapter 5

Answer In One Or Two Words

Question 1. Name two components of clouds.
Answer: Water vapour and dust.

Question 2. Name the cloud that indicates an advancing storm.
Answer: Cirrostratus cloud.

Question 3. Which cloud is also known as ‘bumpy cloud’?
Answer: Stratocumulus cloud.

Question 4. Which type of cloud causes convectional rainfall?
Answer: Cumulonimbus cloud.

Question 5. Which cloud is also known as the ‘thunder cloud’?
Answer: Cumulonimbus cloud.

Question 6. What is the name of the potential heat energy in water vapour?
Answer: Latent heat.

Question 7. On which particle does water vapour condense to form clouds?
Answer: Hygroscopic nuclei.

Question 8. Give an example of hygroscopic nuclei.
Answer: Salt particle.