CBSE Class 11

Here we are providing Class 11 Geography Important Extra Questions and Answers Chapter 13 Water (Oceans). Important Questions for Class 11 Geography are the best resource for students which helps in class 11 board exams.

Important Questions for Class 11 Geography Chapter 13 Water (Oceans)

Water (Oceans) Important Extra Questions Very Short Answer Type

Question 1.
What are brines?
Answer:
Brines are salt solutions commonly containing a higher portion of dissolved salt than that occurring in seawater.

Question 2.
How would you classify the large water bodies?
Answer:
The large water bodies can be classified into four groups, viz., oceans, intercontinental seas, enclosed seas and fringing seas.

Question 3.
Name four major oceans of the earth.
Answer:
The four major oceans of the earth are the Pacific Ocean, Atlantic Ocean, Indian Ocean and the Arctic Ocean.

Question 4.
Give three examples of intercontinental seas.
Answer:
They are Malays Sea, Central American Sea and the Mediterranean Sea.

Question 5.
Give a few examples of enclosed seas.
Answer:
Baltic Sea, Red Sea, Hudson Bay and the Persian Gulf are some examples of enclosed seas.

Question 6.
Identify some fringing seas.
Answer:
Baring Sea, Japan Sea, East China Sea, Andaman, California, North Sea, Laurentian Sea, Bass Sea, English Channel and Irish Seas.

Question 7.
What are the factors on which the amount of rainfall entering the soil depends?
Answer:
The amount of rainfall entering the soil depends upon the rate of rainfall and the infiltration rate of the soil.

Question 8.
What are the first order relief features of the earth?
Answer:
Continents and ocean basins are the first order relief features of the earth.

Question 9.
“The continental margins consists of two major submarine features.” Name them.
Answer:
They are the continental shelf and the continental slope.

Question 10.
Mention three types of features of the ocean basin floor.
Answer:
The ocean basin floor contains three types of features, viz.,

1. abyssal plains and hills,
2. oceanic rise and
3. seamounts.

Question 11.
Name the second layer of oceans identified on the basis of their temperature structure.
Answer:
It is Theraseoline.

Question 12.
What is the major salt presents in the seawater?
Answer:
The major salt present in seawater is sodium chloride.

Question 13.
Name the deepest part of the ocean.
Answer:
The deepest part of the ocean is the Mariana Trench in the Pacific Ocean. It is from 11,034 m. deep below the sea level.

Question 14.
Where is the tallest sea mount situated?
Answer:
The tallest seamount is situated between Samoa and New Zealand which is 8690 m. high from the surrounding ocean floor.

Question 15.
What are the factors determining the salinity of seawater?
Answer:
The salinity of seawater depends upon the extent of evaporation, river discharge and precipitation.

Question 16.
What is residence time?
Answer:
The average time that an element remains dissolved in the ocean before removal is known as residence time.

Question 17.
How do you measure the salinity of seawater?
Answer:
It is measured in gm. of salt per thousand gm of seawater.

Question 18.
Why is the earth called Blue planet?
Answer:
Because of the abundance of water on its surface, the earth is often called a Blue planet.

Question 19.
What are oceanic deeps?
Answer:
Trough like depressions or trenches in the seafloor is called oceanic deeps. Deeps occur mostly at the convergence of plates in subduction zones.

Question 20.
How is the hydrological cycle expressed mathematically?
Answer:
The hydrological cycle is expressed mathematically as:

RF = RO + ET

RF includes all types of precipitations, RO is round off and ET is evapotranspiration.

Question 21.
Which is the largest ocean in the world?
Answer:
The Pacific Ocean.

Question 22.
Which sea has the maximum salinity?
Answer:
Dead Sea – 238 per thousand.

Question 23.
How much part of the earth is covered by the Pacific Ocean?
Answer:
1/3 part.

Question 24.
How much percentage of the earth is covered with water?
Answer:
71 % of the surface of the earth is covered with water.

Question 25.
What is the average salinity of ocean water?
Answer:
35 per thousand.

Question 26.
Name the two main banks of the world.
Answer:

1. The Duggar bank,
2. The Grand bank,

Question 27.
What percentage of the ocean floor is covered by the continental shelf?
Answer:
7.6%.

Water (Oceans) Important Extra Questions Short Answer Type

Question 1.
Why is earth called the ‘Blue Planet’?
Answer:
The earth is called a Blue planet because of the abundance of water found on the surface of the earth. Water covers 71 % of the earth surface.

If we take into account only the water surface of the earth, then 43% lies in the northern hemisphere and 57% in the southern hemisphere.

Question 2.
What are oceanic deeps?
Answer:
The oceanic deeps are deeper than the abyssal plains. They occupy 2% of the oceanic area. Although deeps are found in the Pacific ocean. Mariana deep is the deepest deep in the Pacific Ocean.

Question 3.
Name the most common features found on the ocean floor.
Answer:
The most common features found on the ocean floor are:

1. Continental shelf
2. Continental slope
3. Submarine canyon
4. Abyssal plains
5. Submarine ridge
6. Ocean deeps
7. Troughs

Question 4.
Define the continental shelf.
Answer:
From the coasts towards the open sea, there often exists a stretch of the shallow sea. The bed of this shallow sea bordering the continental platform is known as the continental shelf. It is a continuation of the continental block submerged below the sea. It slopes gently towards the sea, the angle of slope usually being less than one degree. The depth of the shallow seas rushing over a continental shelf varies from low tide to about 100 fathoms. Along the eastern coast of India, there exists a fairly wide strip of the continental shelf.

Question 5.
What are oceanic deeps?
Answer:
Trough like depressions or trenches in the seafloor is called oceanic deeps. Deeps occur mostly at the convergence of plates in subduction zones.

Question 6.
What are seamounts?
Answer:
Seamounts are topographical features rising from the ocean floor. A seamount is an isolated peak, usually a volcano, with a pointed summit, usually lies below the ocean surface, sometimes 3000 m. below.

Question 7.
What is an abyssal plain?
Answer:
Abyssal plain is a deep-sea plain. It is a very large and relatively level area of the ocean floor, covered with a thin layer of sediment. Thus abyssal plain is an area of the deep ocean floor having a flat bottom with a very’ faint slope. Characteristically situated at the foot of the continental rise, the abyssal plain is present in all ocean basins. It is formed by long-continued deposition of very’ fine sediments and, therefore, has a nearly perfect flatness.

Question 8.
Write a short note on the continental rise.
Answer:
Continental rise is a submarine feature of the continental margins. Along its seaward margin, the continental shelf gives way to the continental slope. The slope is abruptly replaced by the continental rise. Continental rise is a surface of much gentler slope decreasing in steepness toward the ocean basin floor. It generally has a moderate to low relief.

Question 9.
What is runoff? How does it occur?
Answer:
Runoff is th§ water flowing from a drainage area. It is that part of precipitation which run off the land surface into streams. Runoff occurs when precipitation, that does not have an opportunity to infiltrate into the soil, flows across the land surface. However, most of it enters the stream channel ultimately, which carries it to the oceans. A part of precipitation that infiltrates the soil percolates downward to the water table through springs. Broadly speaking, runoff is composed of water from both surface flow and seepage flow. It is an extremely important-segment of hydrological cycles.

Question 10.
Discuss the factors affecting the distribution of temperature of the ocean water.
Answer:
The salinity of seawater varies from place to place. At the equator, the salinity is somewhat lower due to abundant rains, greater cloudiness and low rate of evaporation. In latitudes about 20° in both the hemispheres, where evaporation is more intense and precipitation is lower, salinity is greater and in the temperate latitudes, where evaporation is less and rains. are more abundant, salinity is lower.

In Red sea, where no river flows, the salinity is 40 to 41 per thousand. In the Black sea, in which numerous rivers discharge, the salinity is 17 to 18 per thousand. In the White sea. it is between 25 and 26 per thousand, while in the Baltic sea it is 3 to 4 per thousand on an average.

Fig. 13.4: Distribution of surface water salinity in oceans

Question 11.
Why is the seawater saline?
Answer:
The seawater is saline because a number of salts are dissolved in it. The total weight of salts dissolved in the sea is 4800 million tonnes. Of these, sodium chloride, or common salt, accounts for 3800 million tonnes, sulphate for 3000 million tonnes, magnesium for 1600 million tonnes, potassium for 480 million tonnes and bromide for 83 million tonnes. The seawater may be less saline or more saline depending upon the extent of evaporation, river discharge and precipitation, but salt composition remains invariable.

Question 12.
What are the direct and indirect uses of oceans to man?
Answer:
Oceans are directly or indirectly useful to man in many ways:
Direct uses of the oceans:

1. Oceans are the storehouse of fishes.
2. They are a storehouse of minerals.
3. They provide the cheapest route for transportation.

Indirect uses: Indirectly-oceans control the climate.

Question 13.
How is the depth of seafloor measured?
Answer:
The depth of seafloor is measured with sound waves. A depth recorder is used for this purpose. The echo of the sound returning after striking the sea bottom forms the basis of it. It helps to measure the velocity and depth.

Question 14.
What do you understand by hydrosphere?
Answer:
The hydrosphere is the part of the earth submerged by oceans and seas. The vast oceans cover a total area of about 71% of the total earth’s surface. Earth is called a blue planet. Approximately 61% of the northern hemisphere and 81 % of the southern hemisphere is known as water hemisphere. The distribution of land and water is antipolar on earth. The Arctic Ocean surrounds the north pole and the Antarctic continent encircles the south pole.

Water (Oceans) Important Extra Questions Long Answer Type

Question 1.
Prepare a map of the Atlantic Ocean floor, mentioning ocean basins and mid-Atlantic ridges.
Answer:
The Atlantic Ocean covers about one-sixth of the earth’s area. Resembling ‘S’ in shape, the ocean is bounded on the west by North America and South America, and On the east by Europe and Africa. To the south, it extends up to Antarctica and in the north, it is bounded by Greenland and Iceland.

The mid-Atlantic ridge, running from north to south in ‘S’ form is about 14,450 km. long and about 4000 m. high. The ridge has a broad fracture in the middle and slopes on both sides gently. The mid-oceanic ridge in the North Atlantic is known as Dolphin Ridge, and that in the South Atlant ic as the Challenger Ridge. A number of islands are located on the ridge.

The mid-Atlantic ridge divides the ocean into two major basins, namely, the East and West Atlantic basins. Some other basins in the Atlantic are the North American basin, The Labrador basin, The Brazil basin. The Argentina, Agulhas, Angola, and the West.

Fig. 13.3: Major Relief features of the Atlantic Ocean

Question 2.
What type of relief features exists in the ocean basin floor?
Answer:
The ocean basin is an extensive region of the basin floor, generally lying at a depth ranging between 2,500 and 6,000 m. It covers about 76.2% of the ocean’s area.

The ocean basin floor contains three types of relief features:

1. abyssal plains and hills,
2. oceanic rise and
3. seamounts.

An abyssal plain is an area of the deep ocean floor having a flat bottom with a very faint slope. Characteristically situated at the foot of the continental rise, the abyssal plain is present in all ocean basins. Abyssal plains are surfaces formed by long-continued deposition of very fine sediments and, therefore, have a nearly perfect flatness. Abyssal hills are small hills rising to heights of a few tens of metres to a few hundred metres above the sea basin floor.

The ocean rise is an area hundreds of km. in the breadth over which the surface rises several hundred metres above the surrounding abyssal plain. Within the rise, the relief may range from subdued to very rugged.

Seamounts are the isolated peaks that rise 1000 ms. or more above the seafloor. Many of the seamounts are conspicuously flat-topped and extremely steep riched, named guyot.

Question 3.
Identify various layers of the ocean based on the level of salinity.
Answer:
The salinity of the water is the ratio of the total weight of dissolved
solids to the weight of water. It is variable in quantity, differentiating in value from place to place over the oceans and at various depths. The average salinity is 35 per thousand. The relationship of salinity to depth is analogous with the three-layer temperature systems.

1. First and the topmost layer is the shallow surface layer of high salinity (35.0 to 36.5 per thousand)
2. Below this layer is a zone of the rapid decrease in salinity, called a halocline. It corresponds with the thermocline.
3. Below the halocline, differences in salinity’ are very small and salinity lies in the range of 34.6 to 34.9 per thousand for most of the ocean body. Thus, the salinity decreases with the increasing depth.

Question 4.
Discuss the longitudinal variation in the salinity of ocean water.
Answer:
The salinity of seawater varies from place to place. At the equator, the salinity is somewhat lower due to abundant rains, greater cloudiness and low rate of evaporation. In latitudes about 20° in both the hemispheres, where evaporation is more intense and precipitation is lower, salinity is greater and in the temperate latitudes, where evaporation is less and rains. are more abundant, salinity is lower.

In Red sea, where no river flows, the salinity is 40 to 41 per thousand. In the Black sea, in which numerous rivers discharge, the salinity is 17 to 18 per thousand. In the White sea. it is between 25 and 26 per thousand, while in the Baltic sea it is 3 to 4 per thousand on an average.

Fig. 13.4: Distribution of surface water salinity in oceans

Question 5.
Describe the hydrological cycle in brief.
Answer:
The hydrological cycle is the continuous circulation of water from the earth’s surface to the atmosphere. Water from the oceans is evaporated and lifted into the atmosphere. It is eventually condensed and is returned back to the earth’s surface in the form of rain, hail, snow or sleet.

Some of the precipitation, after wetting the foliage and ground, runs off over the surface to the streams. It is the water that sometimes causes erosion and is the main contribution to floods. Of the precipitation that soaks into the ground, some are available for growing plants and for evaporation. Some reach the deeper zones and percolates through springs and seeps to maintain streams during the dry period. The streams, in turn, eventually return the water back to the oceans where it originated. It is because of this never-ending circulation that the process has come to be known as the hydrological cycle.

The hydrological cycle is mathematically expressed as:

RF = RO + ET, where RF-includes all types of precipitation, RO is runoff and ET is evapotranspiration.

Runoff occurs when precipitation, that does not have an opportunity to infiltrate into soil, flows across the land surface. However, most of it enters the stream channel ultimately, which carries it to the oceans. A part of precipitation that infiltrates the soil percolates downward to the water table through springs. Broadly speaking, runoff is composed of water from both surface flow and seepage flow. It is an extremely important segment of the hydrological cycle. Rainwater that reaches the soil surface is wholly or partly absorbed by the soil in the process of infiltration. The amount of rainfall entering the soil depends upon the s* rate of rainfall and infiltration rate of the soil.

Here we are providing Class 11 Geography Important Extra Questions and Answers Chapter 12 World Climate and Climate Change. Important Questions for Class 11 Geography are the best resource for students which helps in class 11 board exams.

Important Questions for Class 11 Geography Chapter 12 World Climate and Climate Change

World Climate and Climate Change Important Extra Questions Very Short Answer Type

Question 1.
What is a climatic region?
Answer:
A climatic region is defined as an area on the earth’s surface, where an approximately homogenous set of climatic conditions is produced by the combined effect of climatic groups.

Question 2.
Into how many regions was the earth divided by the ancient Greeks?
Answer:
The earth was divided into three regions, the winterless tropical region, the summerless polar region, and the intermediate having both 1 winter and summer.

Question 3.
What criteria was followed by KOEPPEN to classify climates?
Answer:
KOEPPEN’s classification is based upon annual and monthly r means of temperature and precipitation.

Question 4.
Why did Trewartha use only a limited number of climatic types?
Answer:
Because he realized that a large number of climatic types and sub-types are too difficult to remember.

Question 5.
How do human activities add methane and carbon dioxide to the atmosphere?
Answer:
Methane and carbon dioxide are added to the atmosphere by burning fossil fuels and by various agricultural activities.

Question 6.
What is the Greenhouse effect on the atmosphere?
Answer:
The concept of heating of the atmosphere indirectly from the earth’s surface is called the Greenhouse effect.

Question 7.
Which elements serve as major determinants of climate?
Answer:
Climate is long-term meaning daily weather conditions as determined by temperature, precipitation, pressure, winds, and humidity.

Question 8.
Which element is regarded as the basic factor of climate and why?
Answer:
Temperature is regarded as the basic factor of climate because other elements are directly or indirectly related to it.

Question 9.
Name the major divisions of the world on the basis of temperature.
Answer:
On the basis of temperature, the world has been divided into three zones, viz., Torrid, Frigid, and Temperate.

Question 10.
Mention various climatic regimes based on rainfall patterns.
Answer:
Wet climates, humid climates, sub-humid climates, semi-arid climates, and arid climates are the various regimes based on rainfall patterns.

Question 11.
Name the scholars who have attempted to devise the classification of world climates.
Answer:
Vladimir Peter KOEPPEN, C.W. Thomthwaite, and Glen T. Trewartha have so far presented a classification of world climates.

Question 12.
What climatic group is designated by ‘A’ type climate in Trewartha’s classification?
Answer:
In Trewartha’s classification, ‘A’ type climate designates ‘Tropical Humid Climate’.

Question 13.
Which type of climate is represented by ‘Ar’?
Answer:
‘Ar’ represents the tropical wet climate.

Question 14.
What is the other name of tropical wet and dry climate?
Answer:
The tropical wet and dry climate is also called the ‘Savanna’ climate.

Question 15.
Name two sub-types of polar climate.
Answer:
The two sub-types of polar climate are Tundra and Ice-cap.

Question 16.
Name the principal Greenhouse gases.
Answer:
Carbon dioxide, methane, and chlorofluorocarbon are the principal gases of the Greenhouse effect.

Question 17.
Which element is common in the principal Greenhouse gases?
Answer:
Carbon is the common element in principal Greenhouse gases.

Question 18.
In which part of the world ice-coring program have been undertaken so far?
Answer:
So far, the ice-coring programs have been undertaken in Antarctica and Greenland ice-caps.

Question 19.
Name the important elements of climate.
Answer:

1. Temperature,
2. Precipitation.

Question 20.
Who did the first classification of climate?
Answer:
Greeks.

Question 21.
What was the basis of classification done by Greeks?
Answer:
Temperature.

Question 22.
Into how many main groups did Trewartha divide the world climate?
Answer:
Into six groups.

Question 23.
Which type of climate is known for the minimum range of annual temperature?
Answer:
Equatorial climate.

Question 24.
What is the characteristic of the steppe type of climate?
Answer:
It is characterized by meager rainfall, low temperature, location in the interiors, and the effects of mountain barriers.

World Climate and Climate Change Important Extra Questions Short Answer Type

Question 1.
Explain why the tropical humid climate is found in an irregular belt of 20° to 40° latitudes.
Answer:
The tropical belt extends across the two tropics, viz., Tropic of Cancer and Tropic of Capricorn in Northern and Southern hemisphere respectively. It is one of the belts which, for part of the year, comes under the influence of trade winds but for the rest of the year is subjected to conventional rain. Moreover, the trade winds which blow from north-east and southeast also bring a considerable amount of rainfall.

Question 2.
What could be the possible consequences of the continued addition of carbon dioxide and methane gases to the atmosphere?
Answer:
The continued addition of carbon dioxide and methane gases to the atmosphere will increase the atmospheric temperature to an extent that it will cause ice to melt in the Arctic Ocean and in Antarctica. As a result, sea levels will rise causing the drowning of central lowlands and islands, altering rainfall and evaporation patterns, creating new plant diseases and part problems, and enlarging the ozone hole. Enlargement of the ozone hole, in turn, will cause more and more ultraviolet radiation to reach the earth’s surface, leading to a further rise in temperature of the lower layers of the atmosphere.

Question 3.
Match the following :

Answer:

Question 4.
Discuss the bases of climatic classifications of Koeppen and Thornthwaite.
Answer:
Koeppen’s classification is based upon annual and monthly means of temperature and precipitation. Native vegetation was considered as the best expression of the totality of climate. Similarly, Thornthwaite followed Koeppen’s principle that plant is nature’s meteorological instrument capable of integrating climatic elements like precipitation effectiveness and potential evapotranspiration.

Question 5.
Discuss the aims and objectives of Trewartha’s classification.
Answer:
Trewartha believed that people who need to understand and use the climatic environment for their own purposes should have the parts of climate presented realistically. At the same time, he also recognized the merits of the genetic type of climatic classification. According to him, “genetic not only increases interest and adds to the scientific quality of climatic analysis, but also gives an extra dimension of insight to the student’s understanding of the description.” Genetic classification of climates emphasizes the causes or origin of their formation based on weather processes.

Question 6.
What type of weather conditions characterizes sub-tropical climate?
Answer:
Sub-tropical climates are found between tropical and temperate climatic zones. In this type of climate, the temperature is above 18°C for nearly 8 months. Winters are mild and short. The coastal areas have rainfall throughout the year while continental areas receive less rainfall.

On the basis of seasonal distribution of precipitation, sub-tropical climates have two sub-types, viz., sub-tropical humid and sub-tropical dry summer climates.

Question 7.
How do the carbon dioxide contents of the atmosphere play a dominant role in causing worldwide climatic changes?
Answer:
The carbon dioxide contents of the atmosphere play a dominant role in causing worldwide climatic change. Carbon dioxide is transparent to incoming solar radiation but absorbs outgoing longwave terrestrial radiation. The absorbed terrestrial radiation is radiated back to the earth’s surface. Thus, it is clear that any appreciable change in carbon dioxide content would bring about changes in the temperature of the atmosphere.

Question 8.
Explain the Greenhouse effect.
Answer:
The concept of heating of the atmosphere indirectly from the earth’s surface is called the greenhouse effect. This effect of the atmosphere is analogous to that of a glasshouse, which lets through most of the incoming short wave solar energy but greatly retards the outgoing longwave earth radiation, thus maintaining surface temperatures considerably higher than they otherwise would be. One can build an instantaneous greenhouse. If the car is parked in the sun for about two hours with the windows closed, the interior temperature will rise. It will be more than the temperature outside.

Question 9.
Describe major reservoirs of carbon on earth.
Answer:
The carbon in the system moves between several major reservoirs. The atmosphere contains more than 750 billion tonnes of carbon at any given time, while 2000 billion tonnes are stored on land, and approximately 4000 billion tonnes are contained in the ocean. Living terrestrial organic matter is estimated to contain between 450 and 600 billion tonnes. World fossil fuel reserves also constitute an important carbon reservoir of some 5000 billion tonnes. The burning of fossil fuels adds more than 5 billion tonnes of carbon dioxide to the atmosphere every year.

Question 10.
Explain why the tropical humid climate is found in an irregular belt of 20° to 40° latitude.
Answer:
The tropical belt extends across the two tropics, viz., Tropic of Cancer and Tropic of Capricorn in Northern and Southern hemispheres respectively. It is one of the belts which, for part of the year, comes under the influence of trade winds but for the rest of the year is subjected to convectional rain. Moreover, the trade winds which blow from north-east and south-east also bring a considerable amount of rainfall.

Question 11.
What are ice-coring programs? How do they help us know about the climate of the earth in the past?
Answer:
Ice-coring programs analyze the trapped gases in Greenland and Antarctica ice-caps during the last 1,00,000 years. Analysis of these trapped gases, like oxygen, carbon dioxide, etc., reveals the cooling or heating trends of the earth, on the basis of which climatic changes have been studied in the past.

Question 12.
Distinguish between Genetic and Empirical classification of climate?
Answer:
Genetic classification of climates emphasizes the cause or origin of their formation based on weather processes. The Empirical classification, on the other hand, is based on observations related to factors for climatic differentiation.

Question 13.
Divide the world into temperature zones.
Answer:
The earth is divided into three main temperature zones :
1. Torrid Zone (Hot Zone): Occurs between 0° to 30° N and S latitudes with a mean annual temperature of more than 20°C.

2. Temperate Zones: Subdivided into
(a) warm temperate zone (between 10° to 20°C temperature, 30° to 40° N and S),
(b) cool temperate zone (0°C to 10°C temperature, 45° to 60° N and S).

3. Frigid Zones (Cool Zones): Occur between 60° to 90° N and S latitudes.

Question 14.
What is the significance of 10°C summer isotherm?
Answer:
10°C isotherm in summer indicates the limit of tree growth. In the Tundra region, trees do not grow because the temperatures are below’ 1.0°C in summer.

Question 15.
In which latitudes the tropical humid climate extend and what are its features?
Answer:
The tropical humid climate (A) stretches along the equator in the irregular belt of 20° to 40° latitude in both hemispheres. The features of this climate are that the temperature and rainfall are high throughout the year. In the coastal region, the average temperature of the coldest month is 18°C.

World Climate and Climate Change Important Extra Questions Long Answer Type

Question 1.
Give an account of any four factors which control the climate of a region.
Answer:
These are the following factors that control the climate of a region :

1. Altitude: Regions on the higher altitude have a cold climate and on the lower altitude have a warm climate.
2. Location: The climate of a region depends on the location of that region. If the location is close to the equator, the climate will be hot and wet.
3. Distance from the sea: Regions that are closer to the sea have a moderate climate and others have an extreme type of climate.
4. The direction of the mountains: The extension of the Himalayas does not allow the cold winds of Central Asia into India and the temperature of India does not come down.

Question 2.
Describe in brief Koeppen’s classification of climate.
Answer:
Koeppen’s classification is strictly empirical as it is neither based on weather process (wind belt, air masses, fronts, and storms) nor does it emphasize causes of formation of climatic type. The classification is based upon annual and monthly means of temperature and precipitation. Natural vegetation is considered the best expression of the totality of climate. On the basis of the climate needs of certain types of vegetation, Koeppen identified five major groups: A to E, to which he added a sixth category of mountain zone (H).

‘A’ is the tropical zone, with a temperature exceeding 20°C all the 12 months.

‘B’ is the sub-tropical zone, where for 4 to 11 months temperature exceeds 20°C, and for 1 to 8 months the temperature ranges between 10° to 20°C.

‘C’ is the temperate zone, where the temperature ranges between 10° to 20°C for 4 to 12 months.

‘D’ is the cold zone, with temperature ranging between 10° to 20°C for 1 to 4 months and below 10°C for 8 to 11 months.

‘E’ is the polar zone, where the temperature remains below 10°C throughout the year.

These major climatic groups were sub-divided on the basis of variation in rainfall and temperature characteristics.

Question 3.
Discuss the global climatic changes in detail.
Answer:
The atmosphere is well structured and fairly dynamic in nature. The dynamism is more complex near the earth’s surface where the changes take place both spatially and temporally. These changes may be induced internally within the earth’s atmospheric system or externally by extra-terrestrial factors. Some of these changes are the results of human intervention and, hence, may be slowed down by human efforts. Global warming is one of the changes caused by man’s continual and growing introduction of carbon dioxide as well as some other so-called greenhouse gases, like carbon and chlorofluorocarbon, into the atmosphere.

The atoms and molecules of atmospheric gases cause absorption and back radiation of sunlight by the greenhouse gases, especially water, carbon dioxide, and methane. The concentration of water in the atmosphere is controlled by evaporation from oceans. Carbon dioxide is introduced into the atmosphere by volcanism. Methane is produced by the metabolization of bacteria in wood/grass-eating animals.

Human activities also add methane and carbon dioxide to the .atmosphere by burning fossil fuels and by various agricultural activities.

The carbon dioxide contents of the atmosphere play a dominant role in causing worldwide climatic changes. The gas is transparent to incoming solar radiation but absorbs outgoing long-wave terrestrial radiation. This absorbed terrestrial radiation is radiated back to the earth’s surface. Thus, it is clear that any appreciable change in carbon dioxide content would bring about a change in temperature in the lower layers of the atmosphere. Methane, which rapidly gets oxidized into carbon dioxide, is 20 times more effective than CO₂

Rapid industrialization and technological changes, a revolution in agriculture and transport sectors have resulted in large supplies of carbon dioxide, methane and chlorofluorocarbon gases into the atmosphere.

Of the many climatic parameters, the temperature is the most affected one due to urbanization and industrialization. The thermal characteristics of urban areas are in marked contrast to those of the surrounding countryside.

Man is considered as an engine of climatic change. In support of this, rice farmers, coal miners, dairy farmers, and shifting agriculturists contribute their rate in global warming.

Question 4.
Describe the advantages of Trewartha’s classification over Koeppan’s classification.
Answer:
On the basis of grouping, climate types are either genetic or empirical. Genetic classification emphasizes the causes or origin of their formation based on weather processes. The empirical classification, on the other hand, is based on observation related to factors for climatic differentiation.

Koeppen’s classification is strictly empirical as it is neither based on weather process nor does it emphasize causes of formation of climatic type. The classification is based upon annual and monthly means of temperature and precipitation. Natural vegetation is considered the best expression of the totality of climate. Koeppen followed the principle that plant is nature’s meteorological instruments capable of integrating climatic elements like precipitation effectiveness and potential evapotranspiration.

The climate classification system devised by G.T. Trewartha represents a compromise between purely empirical and genetic methods. Besides being simple and explanatory, it combines the fundamentals of the empirical as well as genetic classification schemes. Trewartha, while proposing his climatic classification, was conscious of the fact that the classification systems of Koeppen, being based on certain statistical parameters. of a few weather elements, were cumbersome and complex. The empirical quantitative classification system, as devised by the author, produced such a large number of climatic types and sub-types that it was rather too difficult to remember them. Keeping this aspect in view, Trewartha recognized only a limited number of climatic types, i.e., 6 major types and 10 sub-types.

The major climatic groups included: Tropical humid climate
(A) Dry climate
(B) Sub-tropical
(C) Temperate climate
(D) Boreal climate
(E) Polar climate
(F) Each of these, except Boreal
(E) the climate has two sub-types.

Question 5.
Write a note on temperate climates.
Answer:
The temperate climate is found in the vast landmasses of middle latitudes (40° and 65°). This climatic band of severe winters is found between the sub-tropical and boreal type of climates.

The two sub-types of temperate climate are temperate marine and temperate continental. They are primarily demarcated on the basis of summer temperatures.

The temperate marine climate has mild winters and fairly warm i- summers. Throughout the year, the average temperature is above 0°C. Rainfall is experienced throughout the year. This type of climate is found on the western sides of continents in the temperate zone.

The temperate continental climate is found in the interior of the continents in middle latitudes. The impact of land is visible as it is characterized by harsh winters and cool summers. The extreme cooling of the ground is associated with anticyclones. Annual precipitation is low, though it takes place throughout the year. This type of climate is found in north-eastern Asia, eastern Canada, and Eurasia.

Here we are providing Class 11 Geography Important Extra Questions and Answers Chapter 11 Water in the Atmosphere. Important Questions for Class 11 Geography are the best resource for students which helps in class 11 board exams.

Important Questions for Class 11 Geography Chapter 11 Water in the Atmosphere

Water in the Atmosphere Important Extra Questions Very Short Answer Type

Question 1.
What is the greatest source of atmospheric moisture?
Answer:
The surface of the ocean is the greatest source of atmospheric moisture.

Question 2.
What is meant by humidity?
Answer:
The state of the atmosphere with respect to its content of moisture or water vapour is called humidity.

Question 3.
What is meant by sensible temperature?
Answer:
It is the cold or heat felt by the human body, depending not only on actual temperature but also on relative humidity and wind.

Question 4.
Name three states in which water exists.
Answer:
Water exists in three states or forms:

1. Solid (ice),
2. Liquid (water),
3. Gas (water vapour).

Question 5.
What is the measure of absolute humidity?
Answer:
Absolute humidity is measured in grams per cubic metre (g/m³).

Question 6.
What is the dew point?
Answer:
It is the temperature at which air, on cooling, becomes saturated with water vapour, and below which condensation begins and dew forms.

Question 7.
Why dew and frost form on grass quite readily?
Answer:
Because grass is a good radiator and, therefore, cools quickly.

Question 8.
Identify various forms of precipitation.
Answer:
Various forms of precipitation include rainfall, snowfall, hail, sleet and drizzle.

Question 9.
Name three types of precipitation.
Answer:
The three types of precipitation are convectional, orographic and cyclonic precipitation.

Question 10.
How does precipitation take place?
Answer:
Precipitation takes place as a result of the continued condensation and growth of the moisture particles until they become too large to remain suspended in the air.

Question 11.
What is the source of atmospheric moisture?
Answer:
The oceanic surface is the main source of atmospheric moisture.

Question 12.
Which factors control evaporation?
Answer:
There are three main factors which control evaporation:

1. aridity,
2. temperature,
3. movement of air.

Question 13.
Name the various types of clouds.
Answer:
Cirrus clouds, stratus clouds, stratocumulus and cumulus clouds.

Question 14.
What are the different types of fog?
Answer:
Fogs are of three types: radiating, advection and frontal fog.

Question 15.
What is condensation?
Answer:
Cooling of saturated air is called condensation.

Question 16.
What are the different types of rainfall?
Answer:
Rainfall is of three types: convectional, orographic and cyclonic rainfall.

Question 17.
What is sublimation?
Answer:
The process of conversion of ice into liquid or vapour is known as sublimation.

Question 18.
Name the temperature at which a given sample of air becomes saturated.
Answer:
Dew point.

Question 19.
What do you mean by saturated air?
Answer:
The air that contains moisture to full capacity.

Question 20.
What is relative humidity?
Answer:
The ratio of the amount of water vapour actually presents in the air at a particular temperature to the amount of water vapour required to saturate the same air at the same temperature.

Question 21.
What is sleet?
Answer:
The falling of frozen raindrops and frozen melted snow on the earth’s surface is known as sleet.

Question 22.
Name the various types of humidity.
Answer:
Absolute humidity, specific humidity and relative humidity.

Water in the Atmosphere Important Extra Questions Short Answer Type

Question 1.
Describe various processes involved in the change of state (form) of water.
Answer:
Water exists in three forms, solid (ice), liquid (water) and gas-(vapour). All three states are interchangeable. The change of solid to ‘ liquid is called melting; from liquid to solid is freezing; from liquid to gas is evaporation and from gas to liquid is condensation. But sometimes ice directly converts into vapour or vice-versa. This is called sublimation.

Question 2.
Describe various sources of atmospheric moisture on the earth.
Answer:
The surface of the ocean is the greatest source of atmospheric moisture. Besides, smaller water bodies, vegetation and damp surfaces also contribute significant amounts of moisture.

Question 3.
What is relative humidity and how is it measured?
Answer:
The amount of water vapour in the air compared with the amount that would be present if the air was saturated at that temperature. It is expressed in percentage determined by dividing the absolute humidity by water holding capacity of air. If the air is saturated, its relative humidity is 100%; if only half saturated, the relative humidity. is 50%. Since the capacity of air for absorbing and retaining moisture varies with temperature, the relative humidity of air mass can be altered by merely lowering its temperature without changing the actual amount of moisture present in it.

Question 4.
Discuss the reasons which impede the formation of dew or frost.
Answer:
On cool nights in early winter, when Radiation from the ground is relatively rapid, the air in contact with the ground may be chilled to the dew point and moisture condenses on the leaves and grass in the form of dew. If the dew point is below the freezing point, the condensation takes place in the form of ice crystals or frost. The formation of dew or frost is impeded by

1. Dry air,
2. Wind mixes the air and prevents its lower portion from reaching the dew point, and
3. Clouds which slow down terrestrial radiation.

Question 5.
What are the middle clouds?
Answer:
The clouds which form at height of2000-7000 km. above the ground are called middle clouds. Altostratus and altocumulus are examples.

Altostratus – It is a uniform sheet of cloud, grey or bluish in colour and usually has a fibrous structure.

Altocumulus – These are flattened globular masses of clouds arranged in lines or waves. They have large globules with shadows.

Question 6.
Why does the amount of water vapour decrease rapidly with altitude?
Answer:
Water vapour in the atmosphere is the result of the evaporation of water from the earth’s surface, a continual process dependent on air. Since the air becomes thinner with the altitude, so also does the water vapour.

Question 7.
What is condensation and how does it take place?
Answer:
Condensation is the process of water vapour changing to a liquid state. If the air is cooled below its dew point, some of the air’s water vapour becomes liquid. Thus, any amount of cooling of saturated air starts the process of condensation. Condensation may start with the addition of any further water vapour to the saturated air, or with the reduction of its temperature.

Question 8.
What is precipitation? What are the conditions to determine the form of precipitation?
Answer:
Precipitation is a process of condensation of water vapour in ‘ the atmosphere which falls to the earth in the form of rain, snow, hail or sleet. These are the various forms of precipitation.
Conditions for precipitation.

1. There should be evaporation so that the relative humidity is „ high in the air.
2. There should be adiabatic cooling of the moist air.
3. There should be dust particles in the air.

Question 9.
What are the effects of humidity?
Answer:
The main effects of humidity are:

1. The skin of the human body starts to crack due to low relative humidity.
2. It causes joint pain in the human body.
3. The high relative humidity is harmful to the human body.
4. The joints of furniture get loosened.

Question 10.
Why does the amount of water vapour decrease rapidly with altitude?
Answer:
The amount of water in the atmosphere is variable from place to place and from time to time. It decreases rapidly with altitude. The temperature decreases as the altitude increases.

Question 11.
How is rainfall caused?
Answer:
The moist air is cooled, saturated and condensation takes place. Water vapour condenses on a large number of dust particles to form clouds.

The cloud droplets merge to form raindrops. When these raindrops become so heavy that air cannot hold them, these fall on the earth in the form of rainfall. The release of moisture in the form of drops of water is called rainfall.

Question 12.
Describe the conditions for the formation of dew.
Answer:
Following are the favourable conditions for the formation of dew:

1. Clear sky
2. Calmness, i.e., the wind should not blow
3. High relative humidity
4. Rich vegetation cover
5. Long nights

Water in the Atmosphere Important Extra Questions Long Answer Type

Question 1.
Distinguish between:
1. Relative humidity and Absolute humidity.
2. Evaporation and Condensation.
3. Dew and Frost.
Answer:
1. Relative humidity and Absolute humidity:
Relative humidity:
The amount of water vapour in the air compared with the amount that would be present if the air was saturated at that temperature. It is expressed in percentage determined by dividing the absolute humidity by water holding capacity of air. If the air is saturated, its relative humidity is 100%; if only half saturated, the relative humidity. is 50%. Since the capacity of air for absorbing and retaining moisture varies with temperature, the relative humidity of air mass can be altered by merely lowering its temperature without changing the actual amount of moisture present in it.

Absolute humidity:
It is the actual amount of water vapour present per unit volume of air and it is measured in grams per cubic meter.

2. Evaporation and Condensation
Evaporation is the process by which a solid or liquid is converted to a gaseous state or vapour. It occurs whenever energy is transported to an evaporated surface and temperature rises. The molecules become more mobile and overcome the forces binding them to the water surface and break away resulting in evaporation.

Condensation:
Condensation is the process of water vapour changing to a liquid state. If the air is cooled below its dew point, some of the air’s water vapour becomes liquid. Thus, any amount of cooling of saturated air starts the process of condensation. Condensation may start with the addition of any further water vapour to the saturated air, or with the reduction of its temperature.

3. Dew and Frost:
Dew: When the moisture is deposited in the form of water droplets on cooler surfaces of solid objects, such as stones, grass blades and plant leaves, it is known as dew. Clear sky, calm air, high relative humidity, cold and long nights are the ideal conditions for the formation of dew.

Frost: Frost forms on cold surfaces at a dew point which is at or below the freezing point when an excess of moisture is deposited in the form of minute ice crystals instead of droplets of water.

Question 2.
Write short notes on:
(a) Convectional precipitation
(b) Cyclonic precipitation
(c) Orographic precipitation
Answer:
(a) Convectional precipitation:
It occurs when moist air over the heated ground becomes warmer than the surrounding air and is forced to rise, expand, cool and yield some of its moisture.

Convectional rain is common in low latitudes and usually comes in the form of short heavy showers, often during the hottest part of the day. Thunder and lightning generally accompany the showers. If the convection currents are especially strong and turbulent, hail is formed.

(b) Cyclonic precipitation:
It occurs in low-pressure areas, where cyclonic winds coming from various directions converge and force the large volumes of light air to rise and cause rain.

Cyclonic precipitation is generally associated with the passage of depression in middle or high latitudes, as the warm moist air mass of the depression rises and over-rides colder, heavier air.

(c) Orographic precipitation:
It is caused due to relief. It occurs when the moist wind is forced to rise over a mountain or any other height. Precipitation occurs due to cooling of moisture-laden air as it rises over a high relief barrier. It happens, particularly on the windward slopes! On the other side of the barrier or on the leeward side of the slopes, there develops rain shadow area with no or very little rainfall because as the moisture-laden wind descends down the slope, after precipitating on the windward side, it becomes warmer and drier. Such a situation occurs along the western coasts of Qudra, North America and South America. The moist air from the Arabian Sea is forced by Sahyadri hills of the Western Ghats to rise up resulting in expansion, cooling and rainfall.

Amount of precipitation depends on slope, the height of the hills, temperature and moisture content of the air mass. On the other side of the mountain, the descending wind is devoid of moisture and, hence, does not give rain. The eastern slope of Sahyadri mountains in India falls in the rain shadow area.

Question 3.
Describe the factors controlling the rate of evaporation and evapotranspiration.
Answer:
vaporation is the process by which liquid water or ice changes into water vapour. It occurs whenever energy is transported to an evaporated surface and temperature rises. The molecules become more mobile and overcome the forces binding them to the water surface and break away resulting in evaporation.

Evapotranspiration, on the other hand, is the amount of moisture transferred to the atmosphere by evaporation of liquid and solid water plus transpiration from living tissues principally from the plants.

Factors like the temperature of the air, source of moisture, vegetation cover, latitude, permeability and water retention effect evaporation and evapotranspiration.

Evaporation depends upon air temperature. Greater the temperature, higher is the rate of evaporation and so on. Therefore, the highest rate of evaporation occurs in deserts in conditions Of great heat and lack of surface cone.

The surface of oceans is the greatest source of atmospheric moisture.

Vegetation is an important factor, particularly in evapotranspiration. Because, under transpiration, the loss of water takes place from the green plants resulting in a stream of water with dissolved mineral salts surfing up through the plants.

Question 4.
Describe the various forms of precipitation and the major precipitation regimes of the world.
Answer:
Precipitation results from the continued condensation and growth of the moisture particles until they become too large to remain suspended in the air.

If condensation takes place at a temperature above 0°C, the resulting precipitation is in the form of rain.

If the process through a layer of colder air on the way down, it may freeze and fall as sleet.

In a strong turbulent current of a thunderstorm, water drops may be carried upward into freezing temperatures and eventually fall as hail. In fact, violent air currents may keep hailstones shuttling up and down until they grow to enormous sizes.

When the more. moisture crystallises into ice particles from vapour at a temperature below freezing point, it called snow. If snowflakes grow without interference, they form beautiful symmetrical, six-sided Crystals.

Ice-storms result when rain, already near the freezing point, falls on colder ground and vegetation and freezes upon contact.

Major precipitation regimes:
(a) Convectional precipitation:
It occurs when moist air over the heated ground becomes warmer than the surrounding air and is forced to rise, expand, cool and yield some of its moisture.

Convectional rain is common in low latitudes and usually comes in the form of short heavy showers, often during the hottest part of the day. Thunder and lightning generally accompany the showers. If the convection currents are especially strong and turbulent, hail is formed.

(b) Cyclonic precipitation:
It occurs in low-pressure areas, where cyclonic winds coming from various directions converge and force the large volumes of light air to rise and cause rain.

Cyclonic precipitation is generally associated with the passage of depression in middle or high latitudes, as the warm moist air mass of the depression rises and over-rides colder, heavier air.

(c) Orographic precipitation:
It is caused due to relief. It occurs when the moist wind is forced to rise over a mountain or any other height. Precipitation occurs due to cooling of moisture-laden air as it rises over a high relief barrier. It happens, particularly on the windward slopes! On the other side of the barrier or on the leeward side of the slopes, there develops rain shadow area with no or very little rainfall because as the moisture-laden wind descends down the slope, after precipitating on the windward side, it becomes warmer and drier. Such a situation occurs along the western coasts of Qudra, North America and South America. The moist air from the Arabian Sea is forced by Sahyadri hills of the Western Ghats to rise up resulting in expansion, cooling and rainfall.

Amount of precipitation depends on slope, the height of the hills, temperature and moisture content of the air mass. On the other side of the mountain, the descending wind is devoid of moisture and, hence, does not give rain. The eastern slope of Sahyadri mountains in India falls in the rain shadow area.

Question 5.
Why dew is not formed on cloudy, windy nights and in shady places?
Answer:
Dew is formed when objects radiate heat thoroughly so that the moist air coming into contact with them may be sufficiently cooled down and the water vapour condenses into water droplets. The clouds act as a blanket for the earth’s surface. They check the radiation of heat so it does not radiate heat thoroughly. Hence, dew is not formed on cloudy nights and in shady places.

Similarly, dew is not formed on windy nights, because the winds blow fast and the moist air does not come long enough into contact with cold objects to get cooled. Hence, condensation does not take place and no dew can be formed.

Here we are providing Class 11 Geography Important Extra Questions and Answers Chapter 10 Atmospheric Circulation and Weather Systems. Important Questions for Class 11 Geography are the best resource for students which helps in class 11 board exams.

Important Questions for Class 11 Geography Chapter 10 Atmospheric Circulation and Weather Systems

Atmospheric Circulation and Weather Systems Important Extra Questions Very Short Answer Type

Question 1.
What is atmospheric pressure?
Answer:
Atmospheric pressure is the weight of the column of air on the surface of the earth at sea level.

Question 2.
What is atmospheric pressure at sea-level?
Answer:
The atmospheric pressure at sea level is about 1 kilogram per cm2.

Question 3.
What are factors determining the amount of pressure at a particular point?
Answer:
The amount of pressure exerted by air at a particular time is determined by temperature and density.

Question 4.
How the air pressure is the measure?
Answer:
The air pressure is measured as a force per unit area. The units of measurements are millibar (Mb).

Question 5.
What kind of relationship exists between pressure and temperature?
Answer:
There exists an inverse relationship between pressure and temperature.

Question 6.
In which direction the earth rotates on its axis?
Answer:
On its axis, the earth rotates from west to east.

Question 7.
How many pressure belts are there in all?
Answer:
There are seven pressure belts in all.

Question 8.
Give the latitudinal extent of the sub-polar low-pressure belt.
Answer:
Between 45” North and Arctic Circle in the northern hemisphere, and 45° South and Antarctic Circle in the southern hemisphere.

Question 9.
What are the other names used for westerlies?
Answer:
The other names used for westerlies are ‘roaring forties’, ‘furious fifties’, and ‘striking sixties’.

Question 10.
Name two places with the heaviest rainfall in India.
Answer:
The two places with the heaviest rainfall in India are Mawsinram and Cherrapunji.

Question 11.
What do the properties of air masses include?
Answer:
The properties of air masses include their temperature, humidity, hydrostatic moisture content, stability, and abundance of minor content.

Question 12.
Where are the polar maritime air masses located?
Answer:
They are located over warmer high latitude oceans of North Pacific, North Atlantic Ocean, and entire sweep of southern hemisphere oceans, fringing Antarctica.

Question 13.
Give the full form of ITCZ.
Answer:
Inter-Tropical Convergence Zone.

Question 14.
What is a millibar?
Answer:
It is a unit of measurement of atmospheric pressure.

Question 15.
What are the two types of pressure systems?
Answer:
The two types of pressure systems are high-pressure systems and low-pressure systems.

Question 16.
What is a pressure gradient?
Answer:
The pressure gradient is defined as the decrease in pressure per unit distance in the direction in which the pressure decreases most rapidly.

Question 17.
What are isobars?
Answer:
The isobars are imaginary lines drawn through places having equal atmospheric pressure at sea-level.

Question 18.
Why does pressure decrease with altitude?
Answer:
Because the air becomes thinner or its density decreases rapidly upwards from the surface of the earth.

Question 19.
What are tertiary winds?
Answer:
These are local winds like land and sea breeze.

Question 20.
Name the instrument by which the atmospheric pressure is measured.
Answer:
Barometer.

Question 21.
What is the standard sea-level pressure in millibars?
Answer:
1013.25 Mb.

Question 22.
How do air pressure and winds influence the weather?
Answer:
They control temperature and precipitation.

Question 23.
What is the normal rate of pressure decrease with altitude?
Answer:
1 Mb for every ascent of 110 meters.

Question 24.
Name the hot winds which blow in the USA and Canada.
Answer:
Chinook.

Question 25.
Where do you find the maximum and minimum deflection of winds by the Coriolis effect?
Answer:
At poles and equator respectively.

Question 26.
Name two broad types of cyclones.
Answer:
Temperate and tropical cyclones.

Question 27.
What are the two other names of temperate cyclones?
Answer:
Depressions and western disturbances.

Atmospheric Circulation and Weather Systems Important Extra Questions Short Answer Type

Question 1.
How do air pressure and winds influence the weather?
Answer:
Air pressure and winds control temperature and precipitation. Even a minor change in pressure changes the velocity and direction of winds and this, in turn, brings about changes in temperature and precipitation.

Question 2.
What is Coriolis force and who discovered it first?
Answer:
On the rotating earth, a point on the equator moves the fastest. As we go towards the poles, the speed decreases, reaching about zero at the pole. It is because of this difference in speed that any moving body, such as winds and ocean currents, gets deflected when it moves towards the equator or away from the equator. This force or deflection is called Coriolis. It was discovered by Coriolis, a French mathematician.

Question 3.
Explain Ferrel’s law.
Answer:
Ferrel’s law states that all moving bodies like wind and ocean currents get deflected from their normal paths towards the right in the northern hemisphere and towards the left in the southern hemisphere. The role of deflection increases with the distance from the equator. As a result, by the time the poleward directed winds reach 25 degrees latitude, they are deflected into nearly west to east flow.

Question 4.
Explain the occurrence and importance of ITCZ.
Answer:
The ITCZ means Inter-Tropical Convergence Zone. It is also known as Inter-Tropical Front (ITF). It is an equatorial front. It is a broad trough of low pressure defined more sharply over land than over the ocean. The tropical maritime air masses converge here. In ITCZ, the north-east trade winds and the south-east trade winds meet. This zone is mainly stationed over the equator but moves north and south according to the season. The air mass may be almost stagnant, the winds light and variable. Hence the air belt is calm, known as doldrums.

Question 5.
What is a pressure gradient?
Answer:
The pressure gradient is the rate at which pressure rises or falls. The gradient is steep when pressure changes in a short distance and mild when pressure changes at long distances. The pressure gradient is shown by isobars. When isobars are closer, the pressure gradient is steep and vice-versa.

Question 6.
What are tertiary winds?
Answer:
These winds are generated by the influence of the surrounding terrain. They include mountain and valley winds, land and sea-breezes, and other local winds such as loo, foehn, chinook and mistral, etc. Some winds are hot and some winds are cold winds. All are local winds.

Question 7.
What are roaring forties?
Answer:
The southern hemisphere has mostly sea and very little land. Westerlies, therefore, blow without any hindrance and with great velocity. Their roar can be heard far and wide. The westerlies here are called roaring forties.

Question 8.
Give the relation between pressure and temperature.
Answer:
The pressure and temperature have an inverse relationship with each other. As the air gets heated, it expands and rises upwards. The higher the temperature, the lower is the pressure. On the other hand, cold air contracts and becomes heavy. It results in high pressure.

Question 9.
What do you understand by Horse Latitude?
Answer:
The latitudes near the tropics are known as horse latitudes. In this zone, no permanent winds blow. It is a region of high pressure due to descending winds.

The sailing ships from Europe to America had to face problems due to the absence of backing winds. Therefore, some horses were thrown into the sea to make their ships lighter and to move further. This is why these latitudes are known as horse latitudes.

Question 10.
What is a jet stream? Explain.
Answer:
The winds with a high velocity which blow at high altitude are called the jet stream. This strong current of air is located near 90° north latitude. It affects the weather patterns of the world. High flying planes use these as super tailwinds to save time and fuel.

Question 11.
Describe the local winds in brief.
Answer:
Winds having special characteristics under local conditions are known as local winds.

1. Hot winds: Chinook in Canada and USA, foehn in Switzerland.
2. Dry winds: Sirocco in south Europe, Khanzim in Egypt, Hermatton in West Africa, Simoon of Arabia, Santa Anna of California, Zenda of Argentina.
3. Cold winds: Boro and Mistral in Southern Europe, Pampero in Argentina, Buran in Siberia.

Question 12.
Write a short note on ‘doldrums’.
Answer:
The doldrum is an equatorial low-pressure belt between 5°N to 5°S latitudes. It is known as the-belt of calm. The air is constantly heated due to the high temperature. The air expands and rises as convection currents. There are no surface winds. Sailing ships often found them becalmed in this belt due to the absence of backing winds.

Question 13.
What is the importance of air mass?
Answer:
Air mass is important for climatological study. Air masses are related to atmospheric disturbances, cyclones, storms, and fronts.

• The distribution and location of air provide an essential understanding of regional climate.
• Air masses transfer heat from lower latitude to higher latitudes.
• Atmosphericdisturbancesdevelopalongfrontsofdifferentairmasses.
• Air masses are associated with particular types of wind belts and determine the weather characteristics.

Question 14.
What do you understand by valley breeze?
Answer:
The valley breeze occurs during day time. Due to insolation, the valley bottom gets heated. The hot air becomes light and ascends towards the upper slopes. It is known as the valley breeze.

Fig. 10.3: Slopes heated by insolation

Atmospheric Circulation and Weather Systems Important Extra Questions Long Answer Type

Question 1.
Distinguish between:
1. planetary and periodic winds,
2. the sea breeze and land breeze.
Answer:
1. Planetary and periodic winds:
Planetary winds are related to the general circulatory pattern of winds on the rotating earth’s surface. These winds constitute the large-scale motion of the atmosphere under the influence of pressure gradients. They ignore seasonal heating and land-water contrast on the earth’s surface. They are also called permanent or primary wind system of the earth’s surface and comprise trade winds, westerlies, and polar easterlies. These winds blow constantly in a particular direction throughout the year.

Fig. 10.4: Planetary winds

The winds that change their direction periodically with the change in season are called periodic or secondary winds. Monsoon, air masses and fronts, cyclones and anticyclones, land and sea breezes, and mountain and valley breezes are the wind systems that periodically change their courses diurnally or seasonally.

2. Land and sea breezes:
Daily temperature contacts between land and water produce a small diurnal reversal of winds called land and sea breezes. Both are basically caused by differential heating of land and sea.

During the day, the land gets heated up much faster than the sea. The sea remains comparatively cool with higher pressure, so the sea breeze blows in from the sea to land during the day. Its speed is between 5-20 miles/hour and it is generally stronger in tropical than temperate regions.

Its influence does not normally exceed 15 miles from the coast. It is most deeply felt when one stands facing the sea in a coastal area.

At night, the reverse takes place. As the land cools down much faster than the sea, the cold and heavy air produces a region of local high pressure. The sea conserves its heat and remains quite warm. Its pressure is comparatively low. A land breeze thus blows out from land to sea.

Fishermen in the tropics often take advantage of the outgoing land breeze and sail out with it.

Question 2.
Describe the global pattern of the distribution of pressure.
Answer:
The horizontal distribution of pressure, or its global pattern in general, presents an alternate belt of low and high-pressure areas.

There is an inverse relationship between pressure and temperature. The equatorial region having high temperature has low pressure, while the polar regions with low temperature have high pressure. These pressure belts are thermally induced. Logically, there should have been a gradual increase in pressure from the equator towards the poles.

Fig. Pressure belts of the world (See fig.9.1)

There are two intermediate zones of subtropical highs in the vicinity of 30°N and S and two sub-polar lows in the vicinity of 60°N and S. The dynamic control, viz., pressure gradient force, rotation of the earth, are responsible for the formation of these pressure belts.

Thus there are seven pressure belts:

1. An equatorial trough of low pressure.
2. Sub-tropical high-pressure belt (Northern hemisphere)
3. Sub-polar low-pressure belt (Northern hemisphere)
4. Sub-polar low-pressure belt (Southern hemisphere)
5. Sub-tropical high-pressure belt (Southern hemisphere)
6. Polar high (Northern hemisphere)
7. Polar high (Southern hemisphere)

Question 3.
Discuss the seasonal variations in the pressure distribution over the earth’s surface.
Answer:
Despite a broad generalized pattern of pressure distribution on the earth, pressure conditions vary considerably on the basis of prevailing weather conditions in different parts of the world. The horizontal distribution of pressure on the earth’s surface is shown by isobar. Just as there is a daily range of temperature on the surface of tire earth, so there is the diurnal rhythm of pressure.

The direction and rate of change in pressure are called pressure gradient. It is at right angles to isobars, just as the slope of the land surface is at right angles to contour, lines. The rate of change or steepness of the gradient is shown by the spacing of isobars. Closely spacing isobars show’ steep pressure gradient, and widely spaced isobars show’ gentle gradient.

The zonal distribution of pressure is modified by continents and oceans, in summer, the relatively hot continents intensify the low-pressure cells and weaken or destroy high-pressure cells. In a similar manner, the corresponding cooler oceans weaken the low-pressure cells and the high-pressure cells. In winter the situation is reversed. ,

Fig. 10.6: Horizontal distribution of pressure and winds

Question 4.
What are cyclones? Describe the various types of cyclones.
Answer:
Cyclones constitute the most fundamental and climatically the most significant atmospheric disturbances affecting the weather. On the basis of the areas of their origin, they are classified into two types: temperate and tropical.

Temperate cyclones: Temperate1 cyclones are concentrated in the middle latitudes between 35° and 65° in both hemispheres. They are generally extensive having a vertical thickness ranging from 9 to 11 km. and a diameter of about 1,000 km. It is just like a spearhead, having the shape of an upturned ‘V’. The approaching temperate cyclones are noticed by the appearance of dark clouds in the background of white clouds.

According to polar front theory, the highs and lows of westerly wind belts result from the interactions and alteration of two contrasting types of air masses, one in the polar region and the other in the subtropics. Cold air from highs moves toward the equator and is deflected westward, forming the northeast and southeast polar winds. Warmer air from the subtropical highs moves toward the poles and by an eastward deflection from the westerly winds.

Fig. 10.7: Temperate cyclones

As soon as the cyclone approaches, there is drizzle followed by heavy rainfall. The velocity of the wind increases. On the approach of the warm front, the fall in the pressure stops, and the sky becomes clear. This gives the clue that the center of the cyclones has reached. Immediately after this, the temperature begins to fall and the sky becomes cloudy and raining again. This indicates the approach of a cold front.

Tropical cyclones: These are violent storms that originate over tropical seas and move over the coastal areas bringing about large-scale destruction caused by violent winds, very heavy rainfall, and storm surges. They are known as cyclones in the Indian ocean, hurricanes in the Atlantic, typhoons in the western Pacific and South China sea, and willy-willies in west Australia. The conditions favorable for the formation and intensification of tropical storms are:

• Large sea surface with a temperature higher than 27°C.
• Presence of the Coriolis force.
• Small variations in the vertical wind speed.
• A pre-existing weak low-pressure area or low level cyclonic
  circulation.
• Upper divergence above the sea level system.

The cyclone creates stone surges and they inundate the coastland. Over the Indian sea, the cyclonic storms occur in the pre-monsoon

Question 5.
Define and describe the fronts.
Answer:
The contact line between air masses of different properties is called a front. A cold front develops where the cold air mass moves under warm air mass and lifts it up. On the other hand, the trailing edge of a cold air mass that is followed by warm air is called a warm front. In each case, precipitation is likely to occur because warm air is rising over the cold air. Thus duration and intensity of precipitation along the few from.s are quite different. The cold front is steep and produces showery and sometimes violet precipitation for a longer period of time. If the cold front moves faster than the warm front in such a trap, part or all the pocket of warm air may be lifted from the surface, thus producing air occluded front. Often exculpation of the air masses lose earlier characters and form new fronts.

Here we are providing Class 11 Geography Important Extra Questions and Answers Chapter 9 Solar Radiation, Heat Balance and Temperature. Important Questions for Class 11 Geography are the best resource for students which helps in class 11 board exams.

Important Questions for Class 11 Geography Chapter 9 Solar Radiation, Heat Balance and Temperature

Solar Radiation, Heat Balance and Temperature Important Extra Questions Very Short Answer Type

Question 1.
What is insolation?
Answer:
The incoming solar radiation is called insolation.

Question 2.
How much energy radiated by the sun is intercepted by the earth?
Answer:
Only A of the billionth fraction of the energy radiated from the sun is intercepted by the earth.

Question 3.
What is isotherm?
Answer:
Isotherms are imaginary lines joining places having equal temperatures.

Question 4.
Where does the energy radiate from the sun come from?
Answer:
The energy radiated from the sun comes from nuclear reactions in its core.

Question 5.
What is the temperature at the core of the sun?
Answer:
The temperature at the core of sun-is about 15,000,000°C.

Question 6.
What is the radiant energy of sun commonly known as?
Answer:
The radiant energy of the sun is commonly known as short waves or electromagnetic waves.

Question 7.
At what speed the short waves travel?
Answer:
The short waves travel at a speed of light, i.e., about 2,98,000 km. per second.

Question 8.
What is terrestrial radiation?
Answer:
The longwave radiation, i.e., re-emittance of the energy received from the earth’s surface, is terrestrial radiation.

Question 9.
Name the processes which control the heat budget of the earth ., and the atmosphere.
Answer:
They are the processes of absorption, reflection and scattering.

Question 10.
Define heat budget.
Answer:
The gains and losses in heat by incoming and outgoing radiation is known as heat budget.

Question 11.
What is advection?
Answer:
Transfer of heat through the horizontal movement of the air is called advection.

Question 12.
What is meant by temperature gradient?
Answer:
The rate of change of temperature is called the temperature gradient.

Question 13.
Name two months of the year which represent the seasonal extremes of temperature.
Answer:
January and July months represent the seasonal extreme of temperature.

Question 14.
Define Planck’s law.
Answer:
Planck’s law states that hotter a body, the more energy it will ‘ radiate and shorter is the wavelength of that radiation.

Question 15.
What is specific heat?
Answer:
Specific heat is the energy needed to raise the temperature of one grain of a substance by one degree Celsius.

Question 16.
What is insolation?
Answer:
The incoming solar radiation is termed as insolation. It comes in the form of short waves.

Question 17.
What are the methods by which the atmosphere is heated?
Answer:
The atmosphere gets heated in the following ways:
(a) Radiation,
(b) Conduction,
(c) Convection,
(d) Advection.

Question 18.
Why do isotherms bend while crossing the continents and oceans?
Answer:
Due to differential heating and cooling of land and seawater.

Question 19.
How much energy radiated by the sun is intercepted by the earth?
Answer:
1/2000 million part of the total energy radiated by the sun is intercepted by the earth.

Question 20.
Which is the most important process of heating the atmosphere?
Answer:
Terrestrial radiation.

Question 21.
What is the temperature?
Answer:
Warmth or coolness of the air is called its temperature.

Question 22.
What is the extent of the Torrid Zone?
Answer:
23’/2°N to 23’/2°S.

Question 23.
What is the extent of the Frigid Zone?
Answer:
66V20 to poles.

Question 24.
Name the type of climate found in coastal areas.
Answer:
Maritime (moderate).

Question 25.
Why is the temperature of the earth increasing?
Answer:
Due to the increase in carbon dioxide.

Question 26.
What is insolation?
Answer:
The incoming solar radiation is termed as insolation.

Solar Radiation, Heat Balance and Temperature Important Extra Questions Short Answer Type

Question 1.
What is air drainage?
Answer:
The cold air acts almost like water and moves down the slope to pile up deeply in pockets and valley bottoms with warm air above. This is called air drainage. It protects plants from frost damages.

Question 2.
What are the characteristics of isotherms?
Answer:
Main characteristics of isotherms are:

1. Isotherms run along the latitudes.
2. Isotherms take sudden bends at the land-water edge because of land-water contact.
3. They are drawn at equal space which indicates the latitudinal thermal gradient.
4. Isotherms change their positions.

Question 3.
Discuss the variation in the distribution of insolation over the earth’s surface.
Answer:
The incoming solar radiation is called insolation. Insolation is * greatest at the equator. It decreases polewards. The total amount of insolation received at the equator is roughly about 4 times of that received at the poles. In tropical regions, the amount of insolation is only large but there is also little seasonal variation. It is because all their places between Tropic of Cancer and Capricorn experience overhead sun twice during the course of a year. Insolation is maximum twice in a belt between 23°30’ and 66°30′.

Question 4.
What are the effects of the atmosphere on insolation?
Answer:
The energy from the sun passes through different layers of the atmosphere before it reaches the ground. Atmospheric gases are essentially transparent to visible light, but suspended particles of liquid or solid material can absorb or reflect light. A thick cloud may allow less than 10% of sunlight to reach the earth’s surface. Clouds generally behave like mirrors. They reflect sunlight off in different directions rather than absorbing. Reflected sunlight is permanently lost from the earth. The blue colour of the daytime sky is due to the scattering of sunlight.

Question 5.
Define temperature.
Answer:
The temperature is the measurement of available or sensible heat energy in a system. It is a measure of hotness or coldness of the body. Such property determines whether the heat will flow out or into an object when it comes in contact with other objects.

Question 6.
Explain why the angle of the sun’s rays falls variably on different latitudes.
Answer:
The earth revolves around the sun once in a year in an elliptical path called the ‘plane of ecliptic’. At the same time, the earth rotates on its axis in 24 hours. The earth’s axis is tilted making an angle of 66°30′ from the plane. Due to inclination of the earth’s axis, the angle of the sun’s rays falling on the earth’s surface varies from vertical on the equator to more and more slanting as one moves towards the poles.

Question 7.
Explain how the ocean currents influence the temperature distribution over the earth surface.
Answer:
Ocean currents are large movements of ocean water from places of warm temperature to colder temperature or vice-versa. Their movement affects the temperature of the adjacent areas. The warm currents raise the temperature of adjoining colder landmasses. The climate of north-western Europe is modified to a large extent by ocean currents of the North Atlantic Ocean. The cold currents of the western coast of South Africa or South America lower the temperature of adjacent warmer lands.

Question 8.
What is the role played by prevailing winds in temperature modification?
Answer:
Prevailing winds also affect the temperature conditions of the areas. The moderating effects of oceans are brought to the adjacent lands through winds. On the contrary, off-shore winds take the effects of warm or cold currents away from the land.

Question 9.
What is the difference between direct radiation and diffused radiation?
Answer:
The sun emits short wave radiation to space and the earth’s surface. The solar energy strikes the upper limits of the atmosphere and it gradually reaches the earth’s surface directly or indirectly (scattered) and is absorbed. It is estimated that out of 100 units of incoming solar energy, 22 units travel directly to the earth’s surface. This energy flow is called direct radiation. Some of the scattered rays eventually also find their way down indirectly to the earth’s surface. They are collectively called diffused radiation.

Question 10.
What is global warming? What are its causes?
Answer:
The burning of fossil fuels, the cultivation of the soil, industrialisation of land on a large scale, rapid means of transport and deforestation have caused an imbalance in the atmosphere. These activities are increasing the amount of carbon dioxide. Thus, the greenhouse effect has raised the average temperature of the earth by 0,5°C. By the year 2000, the earth’s average temperature will go up by 2°C.

This is called global warming. It is causing a rise in the sea level due to melting of glaciers. It is threatening to submerge many coastal areas.

Question 11.
Why do different parallels receive different amounts of insolation?
Answer:
Due to the inclination of the earth’s axis, the angle of the sun’s rays falling on the earth’s surface varies from vertical on the equator to more and more slanting as one moves towards the poles. This latitudinal difference in the angle of incidence of sun’s rays leads to different amounts of insolation received at different parallels.

Fig.9.5: Incidence of the sun’s rays on the earth’s surface

Question 12.
How does the angle of the sun’s rays falling on the ground affect the amount of insolation?
Answer:
The amount of insolation reaching the earth’s surface depends largely on the inclination or angle of the sun’s rays. Vertical rays and those nearly 80 in the lower latitudes are more effective in increasing temperature than the oblique rays in the higher latitudes, although the duration of sunshine may be much longer in the latter case. Moreover, the oblique rays spread over a larger area on the earth’s surface whereas the vertical rays are concentrated over a smaller area, the intensity of heat being lighter in the area insolated by vertical rays.

Question 13.
Differentiate between advection and convection.
Answer:
Transfer of heat through the horizontal movement of the air is called advection, whereas the vertical mixing of the air is termed as convection. Convection is caused by the circulatory movement of the air itself and the pull of gravity.

Question 14.
Isotherms do not show the correct temperature of a place. Discuss.
Answer:
Isotherms show the temperature of a place supposing it to be at sea level. The temperature is reduced to sea level to avoid the effect of relief. Thus, isotherms do not show the actual temperature of a place.

Solar Radiation, Heat Balance and Temperature Important Extra Questions Long Answer Type

Question 1.
Discuss the impact of tilting of earth’s axis on insolation in the northern and southern hemisphere.
Answer:
The earth rotates on its axis in 24 hours. The earth’s axis is tilted at an angle of 66°30′ from the plane.

Fig.9.6 : Solstices and equinoxes

When the northern hemisphere is tilted towards the sun, it receives the maximum amount of insolation. On 21 st June, the sun is overhead the Tropic of Cancer and it is the longest day of the year for the northern hemisphere. All this time, the southern hemisphere is away from the sun and 21st June is the shortest day of the year for the southern hemisphere. On 21st March and 23rd September, the sun is over the equator and the length of the day is the same everywhere throughout the world. This position is called the equinox.

On 21st December, the southern hemisphere is in front of the sun and receives the maximum daylight. It is, however, the tropics that receive the maximum insolation.

Question 2.
Discuss the impact of altitude on temperature over the atmosphere.
Answer:
Altitude is the height of a point above mean sea level, measured vertically. The temperature decreases with increasing height and latitude from the earth’s surface. This vertical decrease in temperature takes place at the rate of 0.65° per 100 metres or 165 metres per 1°C. These variations are normal throughout the troposphere and are termed as normal lapse rate. The atmosphere near the surface is denser and contains a large amount of water vapour and dust particles. Being closer to the land surface, it absorbs more terrestrial heat than that of the upper air. Hence, the temperature is higher in the lower part of the atmosphere than in the upper part, where the air is cleaner. That is why the higher we go, the cooler it is. Ootacamund, Mount Abu, Panchmarhi are cooler in summer than plains.

Question 3.
What are the basic mechanisms of heat transfer? Discuss the importance of these mechanisms with reference to the atmosphere.
Answer:
There are three basic mechanisms of heat transfer:

1. Radiation,
2. Conduction, and
3. Convection.

1. Radiation: Radiation is the act of transmitting energy in the form of particles of electromagnetic waves. The process is similar to that of transmission of light from an electric bulb. There are two forms of radiations: solar radiation and terrestrial radiation. The atmosphere gets heated up, in fact, through terrestrial radiation and not by solar radiation.

2. Conduction: When two bodies of unequal temperatures are in contact with one another, there is a flow of energy in the form of heat from warmer to cooler body. The layer of air resting upon the warmer earth becomes heated by the process of conduction. The actual conduction during the course of the day affects only the lowest layer of the atmosphere.

3. Convection: Convection is the process of heat transfer caused by the dying circulatory movement of the fluid itself. It takes place due to difference in temperature, and hence in density, and the pull of gravity. Convection produces vertical movement. The horizontal movement of a similar nature is called advection.

Fig97: Convection circulation

A cyclic circulation helps in transforming the heat of lower layers to the upper layers of the atmosphere. This process of heating is convection.

Question 4.
How is the atmosphere heated? Discuss the role of terrestrial radiation in this process.
Answer:
The only source of heat for the earth or the atmosphere is the sun. But the sun does not heat the atmosphere directly. The solar radiation or energy emitted from the sun travels through space and reaches the earth’s surface in the form of insolation or incoming solar radiation. The incoming solar radiation has no significant role in heating the atmosphere. But it helps the earth’s surface. The earth, in turn, reradiates this energy in the form of terrestrial radiation.

Thus the earth functions as a transformer in an electric circuit, receiving energy in one state and transmitting it to another. The sun heats the earth and earth heats the atmosphere. Nearly 51 % of solar energy reaches the earth directly or indirectly. The sun emits short wave radiations to space. The earth, on the other hand, radiates it back in long waves. The terrestrial radiation warms up the layers of atmosphere above it by direct contact or through the transmission of heat by upward movement of air currents.

Fig.9.8: The annual radiation budget of the earth. Units are percentages of the total solar radiation received at the outer edge of the atmosphere.

Question 5.
How many shapes the sun has? Describe photosphere.
Answer:
The sun has three shapes: the core and the interior. The innermost portion of the sun is extremely hot and hence here hydrogen atoms combine to form a smaller number of heavier helium atoms. In this process, certain mass is converted into energy.

The Photosphere: Photosphere is the solar surface. The energy produced in the core reaches to this surface. Most of the sun’s energy comes from the photosphere and we see it as a solar disc. In the photosphere, there are granules that transport energy from the base of the photosphere to its surface. Sunspots are dark regions on the photospheres. They are formed due to strong magnetic fields. The energy is released in the form of x-ray and ultra-violet radiations from the sunspots.

Above the photosphere occurs the sun’s atmosphere. The lower part is chromosphere and the upper is the corona. They are visible only during solar eclipses. Corona exudes electromagnetic energy. These energy particles can be captured by earth’s magnetic field in the ionosphere and their interaction with gases produce the aurora.