# WBBSE Class 10 Geography Solutions Chapter 2.5 Humidity and Precipitation

Detailed explanations in West Bengal Board Class 10 Geography Book Solutions Chapter 2.5 Humidity and Precipitation offer valuable context and analysis.

## WBBSE Class 10 Geography Chapter 2.5 Question Answer – Humidity and Precipitation

Answer in short : 2 Marks

Question 1.
What do you mean by ‘Hydrological cycle’?
Water is present on the earth’s surface as well as the atmosphere in different forms. This water is transported from one sphere to the other in different forms in a cyclical pattern. This circulation of water from lithosphere (earth’s surface or underground) to atmosphere and back is known as the hydrological cycle. It is mainly driven by evaporation and condensation.

Question 2.
What do you mean by humidity ?
Humidity is the general term refering to the water vapour content of air at one time and place. It is the measure of the dampness of the atmosphere.

Question 3.
What is the relation between humidity and temperature ?
Humidity capacity or moisture retaining capacity of air is directly related to the temperature condition of the air. Higher the temperature, greater is the water holding capacity of air and vice versa. Hence, cooler air gets saturated faster than hot air.

Question 4.
What do you mean by saturation of air ?
Air is said to be saturated when it holds moisture or water vapour to its fullest capacity at that particular temperature.

Question 5.
What do you mean by Absolute humidity ?
Absolute humidity refers to the total amount of water vapour present in a given volume of air. It is the weight of actual amount of water vapour present in a unit volume of air. It is measured in gram per cubic centimetre.

Question 6.
What is Relative humidity ?
The ratio of the amount of water vapour present in the air mass at a given temperature of a place to the maximum quantity that the air can hold at that particular temperature, is known as relative humidity.

Question 7.
What is Specific Humidity ?
Specific humidity is the mass of water vapour in grams contained in a kilogram of air. It represents the actual quantity of moisture in a definite amount of air. It is measured in gram/kilogram.

Question 8.
What is condensation?
The process of conversion of atmospheric water vapour back to water is known as condensation. In the atmosphere, they may occur in the forms of dew, fog, smog, cloud, mist, haze etc.

Question 9.
What is the ‘Dew point’ ?
The temperature at which air gets saturated and below which condensation begins is called the ‘Dew point’.

Question 10.
What is ‘dew’?
The water droplets formed by the condensation of water vapour on a relatively cold surface is called ‘dew’.

Question 11.
What is the difference between fog and smog?
Suspended tiny droplets or ice crystals in the air layer next to the earth, that reduce visibility to 1000 m or even lower are called fog. Combination of smoke with fog, which creates a hazy environment, reducing visibility even more, is called smog. It is more common in an industrial areas.

Question 12.
What is cloud?
A visible aggregate of tiny water droplets or ice crystals or a mixture of both suspended in the air, are called cloud. It forms when condensation meets with supersaturation conditions within the air that is free from dust and aerosols.

Question 13.
What do you mean by Precipitation?
Condensation of water vapour in the air in the form of water droplets and ice, and their falling on the ground is called precipitation. It can occur in the form of rain, snow, sleet, hail etc.

Question 14.
What is rainfall ?
When moisture-laden air rises up, condensation takes place and clouds are formed. It the clouds air further cooled, more condensation occurs and drops of water formed are big in size. These big water drops are too heavy to remain in the air and fall down towards the ground in liquid form. This is called rainfall.

Question 15.
What is an isohyet?
An isohyet is an imaginary line drawn on a map joining places receiving the same amount of rainfall in a given period, such as a month, a season or a year.

Question 16.
Name the different types of rainfall.
There are three types of rainfall-convectional, orographic or relief and cyclonic or frontal rainfall.

Question 17.
Where does convectional rainfall generally occur?
Convectional rainfall is very common in the Equatorial region where it occurs almost daily in the afternoon around 4 o’clock. Hence, it is also called the 4 o’clock rain.

Question 18.
What do you mean by climatic regions ?
The average weather conditions of a particular region during a particular period of the year, recorded for 35 years is known as climate. Depending on the predominant climate, the world can be divided into several regions. These regions are called the ‘Climatic regions’.

Question 19.
How can you identify wet equatorial climate prevailing in a region?
The conditions that prove the existence of wet equatorial climate prevailing in a region are :

1. Average temperature : 25°-29°C
2. Average annual rainfall : 250 cm, rainfall occurs in all the months.
3. Maximum rainfall : occurs in March-April, and September – October.

Question 20.
How can you identify Tropical Monsoon climate?
The conditions of Tropical Monsoon climate are :

1. Average annual temperature : 24°C
2. Average summer temperature : 27°-32°C
3. Average winter temperature : 10°-27°C
4. Average rainfall : 100-150 cm
5. Highest rainfall : May to September in northern hemisphere, November to March in southern hemisphere.

Question 21.
How can you identify Tropial Hot Desert climate?
The conditions of Tropical Hot Desert climate are :

1. Average annual temperature : 20°-32°C
2. Average annual rainfall : 16-25 cm
3. Hottest months : May to August in the northern hemisphere, November to February in the Southern hemisphere.

Question 22.
How can you identify Mediterranean climate?
The conditions of Mediterranean climate are :

1. Average annual temperature : 13°-18°C
2. Average summer temperature : 14°-22°C
3. Average winter temperature : 10°-14°C
4. Average annual rainfall occuring during winter : 35-75 cm

Question 23.
How can you identify Tundra climate?
The conditions of Tundra climate are :

1. Average annual temperature : (-) 10°C to (-) 15°C
2. Average annual rainfall : 10-15 cm. Most precipitation occurs in the form of snow.
3. Hottest months : May to August in the northern hemisphere and November to February in the Southern hemisphere.

Question 24.
Mention two characteristics of absolute humidity.
(i) Absolute humidity may remain unchanged throughout the day even if Relative Humidity changes.
(ii) Absolute humidity helps to decide the amount of precipitation possible.

Question 25.
Name the instruments that help to measure humidity.
Humidity can be measured by the Dry and Wet Bulb Thermometer. It is also measured by a Hygrometer. The common types of Hygrometers used for this purpose are – Dew point Hygrometer, Hair Hygrometer, Resistant Hygrometer etc.

Question 26.
Why is fog and smog more common in urban and industrial areas ?
The air over urban and industrial areas is filled with suspended particles of dust, carbon etc. which act as a cool surface for condensation of water vapour. Thus, they cause occurrence of fog and smog much more in urban and industrial areas.

Question 27.
Name the regions of the world that experience Hot Wet Equatorial climate.
The regions that experience Hot Wet Equatorial climate are :

1. Amazon basin in Brazil, South America.
2. The Zaire basin, Congo basin, Ivory coast, Ghana, Nigeria in Africa.
3. Malaysia, Indonesia and other islands of South-East Asia.

Question 28.
Name some countries that experience tropical monsoon climate.
The countries that experience tropical monsoon climate are – (i) India, (ii) Pakistan, (iii) Bangladesh, (iv) Myanmar, (v) Cambodia, (vi) Thailand, (vii) Laos, (viii) Vietnam etc.

Question 29.
Name some hot deserts of the world.
(a) Africa – Sahara, Kalahari
(b) Asia – Arab, Thar
(c) North America – Colorado, Soneran
(d) South America – Atacama, Peru
(e) Oceania – The Great Australian desert

Question 30.
Name some important Temperate grasslands of the world.

1. Steppes of Europe and Asia (World’s largest)
2. Prairies of North America.
3. Pampas of South America
4. Veld of Africa
5. Downs of Oceania.

Question 31.
Why is the Equatorial region called ITCZ ?
The Equatorial region is called the ITCZ or the Inter Tropical Convergence Zone because the South-Eastern and North-Eastern trade winds meet at the Equatorial region near 5°-10° N and S latitudes.

Question 32.
Why is the Equatorial region called Doldrums?
The Equatorial region does not face any wind due to the convergence of the trade winds of both the hemispheres. A condition of calm persists in this region. This is called Doldrums.

Question 33.
Why is Equatorial rainfall also called 4 o’clock rainfall ?
The Equatorial region experiences convectional rainfall. The sky remain clear and bright throughout the day. But due to high rates of evaporation, dense cumulonimbus clouds accumulate at about 3-4 o’clock in the afternoon and cause heavy rainfall. Thus, it is also called 4 o’clock rainfall.

Question 34.
What is a temperature and rainfall graph ?
Temperature and rainfall graph is a type of composite thematic map, where the average monthly temperature is represented by the line graph and the total monthly rainfall is represented by bar graphs on the same graph paper. It helps to compare and analyse the temperature and rainfall conditions of a place at the same time.

Answer in brief : 3 Marks

Question 1.
What is the importances of water vapour in the atmosphere?
The importances of water vapour in the atmosphere are –

1. Water vapour absorbs some insolation as well as back radiation of earth’s heat. Thus, it reduces atmospheric temperature to a certain extent.
2. It releases latent heat while condensation and may increase temperature to a certain extent.
3. Without water vapour, precipitation of no kind would have been possible (rain, snow, dew, fog etc.)
4. Too much presence of water vapour makes the atmospheric condition very humid and uneasy.
5. It influences growing of certain industries like cement, jute and flour.

Question 2.
Compare between Absolute Humidity and Relative humidity.

 Absolute Humidity Relative Humidity i. Represents the total or absolute amount of water vapour present in the unit volume of air at that particular temperature. i. Represents the ratio between the present amount of water vapour and the total amount of water vapour that the unit volume of air can hold at that particular temperature. ii. It is an absolute amount. ii. It is a ratio. iii. It is expressed in ‘grams’. iii. It is expressed in percentage. iv. It can remain constant throughout the day. iv. It changes with change in atmospheric temperature in a day. v. Does not give any idea whether rainfall may occur or not. v. Gives an idea whether rainfall may occur or not.

Question 3.
How is rainfall measured ?
Rainfall is measured with the help of an instrument called ‘Rain Gauge’. The rain gauge is planted till its half in the ground in an open space, where the rain water can directly fall into the instrument. This collected water is then poured into a measuring cylinder to record the amount of rainfall. It is expressed in millimetres or inches. Nowadays, a self-recording instrument called the ‘Hyetograph’ is used for measuring rainfall.

Question 4.
What is a rain-shadow area ?
In maintainous areas, the moisture-laden clouds hit with the windward slope and shed the rains over there. The opposite or leeward slope of the mountain does not receive much or any rainfall. This drier slope of the mountain is called the rain-shadow area.

Question 5.
List the major climates of the world and their average annual temperature and rainfall conditions.

 Climate Average annual temperature 250 cm i. Wet equatorial climate 25°-27° C 100-150 cm ii. Tropical Monsoon climate 25° C below  16 cm iii. Hot desert climate 30°-35° C 35-75 cm iv. Mediterranean climate 13°-18° C 25-50 cm v. Steppe Climate 16°-20° C 100-150 cm vi. China Climate 27° C in summer 4° C in winter 250 cm (West) vii. West coast Oceanic climate 16° C in summer, 4° C in winter 75 cm (East) viii. West continental climate 20°-25° C in summer Below 0° C in winter 50-100 cm ix. Wet temperate climate 10° C in summer Below 0° C in winter 25-50 cm x. Tundra climate -12° C 10-40 cm

Question 6.
What are the controlling factors of relative humidity?
The controlling factors of relative humidity are –

1. Temperature – Temperature is inversely related to relative humidity. If temperature increases, water holding capacity of air increases, hence humidity decreases.
2. Water vapour – Increase in amount of water vapour in the air increases relative humidity.
3. Rainfall – Increase in rainfall is the result of increase in relative humidity.
4. Air pressure – Relative humidity is usually higher in regions of low pressure.

Answer in details : 5 Marks

Question 1.
Discuss the Convectional rainfall.

Rainfall which is caused due to convectional currents in the atmosphere is called convectional rainfall. Excessive heating causes too much evaporation. Thus air is filled with water vapour. This heated and light air rises upwards until temperature reduces and reaches its dew point. The water vapour then condenses and forms

cumulus clouds. They further develop into cumulo-nimbus clouds at about 11 \mathrm{km} height. These clouds are very heavy and bring about rainfall, usually accompanied by thunder and lighting. These are also called Thunder showers. Convectional rainfall is most common in the Equatorial region, where it occurs almost daily in the afternoon around 4 o’clock. Hence, they are also called the 4 o’clock rains.

Question 2.
Discuss the occurrence of Orographic or Relief rainfall.