SEBA Class 9 Geography (Elective)|Notes & Answer| Chapter-1| Weather and Climate

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SEBA CLASS 9 QUESTION ANSWER (ENG. MEDIUM)

SEBA Class 9 Geography (Elective)|Notes & Answer| Chapter-1| Weather and Climate

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SEBA Class 9 Geography (Elective)|Notes & Answer| Chapter-1| Weather and Climate

TEXTUAL QUESTIONS AND ANSWERS

1. What do you mean ‘weather’ and ‘climate’? Distinguish between weather and climate. 

Ans. The atmospheric conditions that occur in a place for a short period of time is called weather. On the other hand, the average atmospheric conditions that prevails over a place for a long period of time (at least 30 years) is known as climate.

The differences between weather and climate are :

SL.NO.Basis of differenceWeatherClimate
(i)PeriodConsidered over a short period of time such as a day, a week, etc.Considered over a long period of time (at least 30 years).
(ii)AreaIndicates the atmospheric conditions over a small area.Refers to the atmospheric conditions over a large area.

2. Mention the elements of weather and climate.

Ans. The main elements of weather and climate are :

(i) Temperature 

(ii) Pressure of air

(iii) Humidity

(iv) Wind

(v) Precipitation

3. State the elements of weather and climate. 

Ans. The main elements of weather and climate are temperature, pressure of air, humidity, wind and precipitation.

(a) Temperature: 

The influence of temperature on weather and climate are:

  1. The earth is heated by the sun’s light and heat. As the incident solar energy reaches the earth’s surface, it gets reflected and this reflected heat warms up the lowest layer of the atmosphere-troposphere. As the air in this layer gets heated up, it moves upward and cold air from the surrounding areas move in. In this way, low pressure and high pressure centres are created.
  2. Temperature changes in the atmosphere along the vertical direction. As one moves up, temperature decreases at the rate of 6.5°C per kilometre in the troposphere. 
  3. Temperature also varies in the horizontal direction due to differences in the inclination of the sun’s rays. The temperature decreases as one moves from the equator towards the poles.

(b) Pressure of air or atmospheric pressure: 

The force exerted by air on per unit area effects weather and climate in the following ways:

  1. Air of the lower layer of the atmosphere gets much compressed causing an increase in density. When density increases, atmospheric pressure also increases. As the density of air decreases as we go up, the atmospheric pressure decreases. 
  2. Atmospheric pressure also changes horizontally. The density of air is low over the equator while it is high in the polar region. Hence, atmospheric pressure is very high in the polar regions while it is low in the equator.

(c) Humidity: 

Humidity, the amount of water vapour contained in the air influences weather and climate of a place. Temperature determines the water-holding capacity of air which contains varying amounts of water vapour at various places at varied times. The warm air can hold more water vapour and cold air can hold comparatively less amount of water vapour.

(d) Wind: 

The movement of air from a high pressure area to a low pressure area is called wind. Winds originate due to the variation in pressure and pressure is created by variation in temperature over place and time. Wind can or may increase the temperature of a place and thereby influence its climatic conditions.

(v) Precipitation: 

When the water vapour present in the air gets nacted moves upward, ge: condensed and later comes down to the earth in various forms called precipitation. The various forms of precipitation are dew, fog, mist, sieet, snowfall, rainfall, drizzie, etc. Among these, rainfall and snowfall can considerably influence the weather and climatic conditions of a place.

4. Explain the relationships among temperature, pressure and humidity. 

Ans. There is a close relationship among temperature, pressure and humidity.

  1.  The relationship between temperature and pressure is that when temperature increases atmospheric pressure decreases and vice versa.
  2. There exists a close relationship between humidity and temperature. Warm air can hold more water vapour and cold air can hold less amount of water vapour. When the temperature is high, air becomes light and light air can hold more water vapour. In other words, when there is high temperature, humidity is also high and vice versa. 
  3. The relationship between humidity and pressure is that humid air has low pressure. In other words, as humidity increases, air pressure decreases and vice versa. 

5. How are the variations in atmospheric pressure caused?

Ans. Atmospheric pressure refers to the force created by air on per unit area.lt varies on the basis of:

  1.  Air temperature: Distribution of temperature is not uniform over the earth’s surface due to the difference in the inclination of sun rays. Due to temperature variations, some regions of the earth are cold, some regions are hot while some other regions have medium temperature. High temperature has low pressure while low temperature has high pressure. That is why, the equatorial region which has high temperature experiences low pressure and polar regions which have low temperature, experience high pressure.
  2. Surface elevation or height: The atmospheric pressure decreases with increase in surface elevation or height. The atmospheric pressure decreases at the rate of 34mb (millibar) per 900 feet of height in the troposphere.

6. Why does the wind blow?

Ans. Enfierent places navi uffieren pressure due to variation in temperature.conditions in the regions having high temperature, the air gets heated and tegnes up, creating in the process, a low pressure area. This torcer the air from the surrounding high pressure area to prove to the low pressure area. This brings about movement of air i.s. blowing of wind

7. What is precipitation?? Name the different types of precipitation. 

Ans. Condensation of water vapour present in the air increases their size which later fall down to the earth’s surface due to the force of gravity in various forms.

This is known as precipitation. The different types of precipitation are:

  1.  Dew
  2. Fog
  3. Mist
  4. Sleet
  5. Snowfall
  6. Rainfall
  7. Drizzle

8. Mention the factors affecting weather and climate.

Ans. The main factors affecting weather and climateæe :

  1.  Latitude
  2. Elevation
  3. Neamessi tossen
  4. Ocean currents
  5. Location of hills and mountains 
  6. Wind 
  7. Characteristics of land
  8. Slope of the land
  9. Vegetation

9. Explain with examples the factors of weather and climate. 

Ans. The main factors that influence weather and dimme are : 

  1. Latitude: The latitude of a place indicates how far it is from the equator. For instance in the equatorial region, the sun shines perpendicularly, so it is the hottest region of the earth. Temperature decreases gradually towards the poles as the sun rays falis obliquely in this region. The oblique rays travel a longer distance through the atmosphere having low intensity of heat whicltirings in two temperatures in the polar region. 
  2. Elevation:: Temporal verte Temperature decreases with variation in height. 6  kilometre increase in elevation. As a result, places situated on the same latitude may have different climatic conditions. e.g. Shillong and Allahabed are sittstad on the name latitude, but experience different eme’s dus to their difference in elevation, Shillong expartended much colder climate than Allahabad as the father is situated at lower sea level than that of Shillong.
  3. Nearness to the sea: A place near to the sea has a mild summer and mild winter, but a place far away from the sca has very hot summer and very cold winter. One of the main reasons for the mi climats of Gr nearness to the sea.
  4. Ocean currents: Wann ocean currents flowing by the side of places along the son coast increase temperature of the place while cold ocean currents flowing nearby reduce the temperature considerably. e.g. the warm Gulf stream has made the north-west European coast is less cold. 
  5. Location of hills and mountains: A high mountain situated in a country may prevent very hot or cold wind from entering the countrye.g. the Himalayan mountains prevent the cold winds of Central Asia from entering India. Moreover, the Himalayan ranges block the moisture-laden winds and bring rain to the windward side of mountains. The Ganga-Brahmaputra valley lying at the foothills of these mountains gets heavy rain during the monsoons. 
  6. Wind: The direction of wind has a great influence in bringing rain to a region. Wind also affects the temperature of a region. The hot wind warms the land while cold wine melts the land. In India, moisture laden winds come from the Bay of Bengal and the Arabian Sea during summer and it causes heavy rainfall in the Ganga-Brahmaputra valley in the southern region.
  7. Characteristics of the land: An alluvial land with dense vegetation does not become too hot during summer or during the day. Such a land also does not become top cold during winter or at night. But sandy soils devoid of vegetation get heated or cooled very quickly. The presence of dense vegetation also brings about good amount of rainfall.e.g. the deserts of Rajasthan become very hot during the day and get cooled at night.
  8. Slope of the land: The sloping lands facing the sun receive vertical sun rays which lead to high temperature while the lands sloping against the sun receive less solar temperature. e.g. the south-facing slopes of the Himalayas and Alps experience more temperature than that of the north-facing slopes. The windward side of the mountains also receives more rainfall than other places.
  9. Vegetation: The regions that have dense forest get good rainfall. On the other hand, regions with scanty vegetation get less rainfall. e.g. many parts of Northern India today face drought conditions due to extensive deforestation that has taken place in this region.

10. What are the types of climate?

Ans. The various types of climates are:

  1. Equatorial climate
  2. Monsoon climate
  3. Savanna or sudan type climate
  4. Hot desert climate
  5. Temperate desert climate
  6. Mediterranean climate
  7. Temperate humid or Chinese climate
  8. Temperate grassland climate
  9. Temperate marine climate
  10. Humid east-coast! climate
  11. Subpolar (taiga) climate
  12. Tundra climate
  13. Mountain climate

11. State the various types of climate with suitable diagrams. 

Ans. The various types of climate on the basis of latitudinal extension is shown below:

12. Write short notes on the following:

  1.  Relative humidity
  2. Atmospheric pressure
  3. Pressure belts
  4.  Types of rainfall
  5.  Effect of latitudes on climate
  6. Effect of vegetation on climate
  7.  Monsoon climate
  8.  Taiga type of climate
  9. Mediterranean climate
  10. Savanna climate
  11. Tundra climate
  12. Mountain climate

Ans. (a) Relative humidity: 

Relative humidity is the ratio of the weight of water vapour present in a definite volume of air at definite temperature and the weight of water vapour necessary for saturation of the same volume of air at the same temperature. Generally, it is expressed in percentage. The weight of water vapour

With the change of air temperature, the capacity to retain moisture increases and this also affects relative humidity. it is greater on the ocean and least over the continents. It is also very little over the desert areas.

(b) Atmospheric pressure: 

Atmospheric pressure means the force exerted by air on a per unit area. The average atmospheric pressure at sea level at 15°C is 1013.2 mb (millibar). It is measured with the help of an instrument named a barometer. Pressure differences are caused by variations in temperature and elevation. High temperature brings about low pressure and vice versa. Pressure decreases at the rate of 34 mb per 900 feet of height of the atmosphere.

(c) Pressure belts : 

Due to variation in temperature, different places have different atmospheric pressure. On the basis of pressure variations on the surface of the earth, the following permanent pressure belts have been identified in the northern and southern hemisphere :

  1. Equatorial low pressure belt
  2. Subtropical high pressure belt 
  3. Sub-polar low pressure belt
  4. Polar high pressure belt

(d) Types of rainfall 

Rainfall is one of the main forms of precipitation. It has a great influence on climate. Rainfall is of five types:

  1. Convectional rainfall: The air over the earth’s surface gets heated due to intense solar radiation and this heated air moves upward in the atmosphere. The water vapour contained in such air gets condensed and falls down as rain called convectional rainfall.
  2. Orographic rainfall: Sometimes rain occurs due to the blocking of the moisture-laden winds by the hills and mountains forcing them to go up, get condensed and fall down as rain known as orographic rainfall or relief rain.
  3. Cyclonic rainfall: The rainfall which occurs along with the cyclonic wind is known as cyclonic rainfall.
  4. Latitudinal rainfall: The rainfall which occurs in some regions due to their latitudinal position is known as latitudinal rainfall. Generally such rains are caused by planetary or permanent winds blowing over certain latitudes.
  5. Forest rainfall: The air around the forest has more moisture due to the respiration of the plants. When such air goes up, it gets condensed and falls down as rain, called forest rain.

(e) Effect of latitudes on climate: 

The latitude of a place indicates how far it is from the equator. For instance in the equatorial region, the sun shines perpendicularly, so it is the hottest region of the earth. Temperature decreases gradually towards the poles as the sun rays falis obliquely in this region. The oblique rays travel a longer distance through the atmosphere having low intensity of heat whicltirings in two temperatures in the polar region.

(f) Effect of vegetation on climate: 

Vegetation: The regions that have dense forest get good rainfall. On the other hand, regions with scanty vegetation get less rainfall.

e.g. many parts of Northern India today face drought conditions due to extensive deforestation that has taken place in this region.

(g) Monsoon climate: 

The monsoon climate is experienced in the eastern parts of the countries in the northern hemisphere lying between 10°N and 40° N latitudes. This region experiences summer temperature between 27° C and 32°C. The average annual rainfall is between 100 and 200cm. The regions that receive annual rainfall between 100 and 200cm have deciduous types of forests while regions that get more than 200cm of rainfall have evergreen forests. The main areas that have this type of climate are India, Bangladesh, South-east Asia, Southern China, Southern Japan, North-east Africa, Mexico, Florida, Northern parts of Australia and Malagasy.

(h) Taiga type of climate: 

The subpolar (Taiga) climate is experienced in the subpolar region lying between 50° and 65° N and S lines of latitude. The average summer temperature ranges from 10°C to 30°C while average winter temperature goes down to 2.5°C. This climatic region experiences heavy snowfall and very little rainfall. The main vegetation found in this region is the coniferous forests. These coniferous forests are called Taiga in Siberia.

(i) Mediterranean climate: 

The latitudinal location of the Mediterranean climatic region is 30° and 45° north and south of the equator. The summer temperature of this region varies from 21°C to 27°C while winter temperature ranges from 10°C to 13°C. This region experiences rainfall in winter. The main areas having this type of climate include regions around the Mediterranean sea, Chilean coast, southern coast of Africa, south-west coast of Australia, California in the US, etc. The main types of vegetation found in this region are evergreen and deciduous types. This region is ideal for the cultivation of horticultural varieties of fruits.

(j) Savanna climate: 

The savanna type of climate is also known as sudan type climate. This climate prevails in regions such as Sudan, Central India, North-central Africa, Southern Brazil, Argentina, Venezuela and Central parts of Central Australia. The average summer temperature is 27°C- 28°C and average winter temperature varies from 10°C to 15°C. The rainfall varies from 25cm to 40cm which encourages the growth of extensive grasslands. Such grasslands of Africa are called ‘Savanna’ while those of Brazil are called ‘Campos’.

(k) Tundra climate: 

The regions lying within the Arctic and Antarctic circles experience a Tundra climate which prevails in the northern-most parts of Asia, Canada and Antarctica. The region under this climate receives sunshine of low intensity for almost six months and the remaining six months are night. Summer temperature hardly goes up to 10°C while winter temperature drops down below 0°C. As the surface remains covered with ice for nine months of the year, so only lichens and some mosses grow. The population is sparse with some Eskimos and only a few other hunter groups living in such extreme cold climates.

(l) Mountain climate: 

Due to high elevation, mountains have different climatic conditions depending on the height. Equatorial type of climate prevails along the foothills region and with the increase in height climate changes. The Alpine climate exists in the middle portion. Here the air remains cold and moderate rainfall takes place. Vegetation such as grasses, shrubs, and coniferous trees are found here. The Alpine climate is suitable for sheep and cattle rearing. At high altitude, ‘tundra’ type of climate prevails. This type of climate is found in the high ranges of the mountains such as the Himalayas, Alps, Rockies, Andes, etc.

13 Answer the following questions:

(a) How far does the atmosphere extend above from the earth’s surface? 

Ans. The atmosphere extends up to a height of nearly 10,000 km from the earth’s surface.

(b) What is the lapse rate?

Ans. Lapse rate is the rate of decrease of temperature in the Troposphere on the basis of increase in altitude. This lapse rate is 6.5°C per km with increase in elevation along the atmosphere from the earth’s surface.

(c) What is the average atmospheric pressure on the sea level? 

Ans. The average atmospheric pressure at the sea level at 15°C is 1013.2 mb (millibar).

(d) What is the humidity of the air?

Ans. Humidity of air is the amount of water vapour contained in the air.

(e) What do you mean by the term ‘saturated air’? 

Ans. If a particular volume of air with particular temperature has exactly that amount of water vapour which it can hold at a particular temperature condition, then such a parcel of air is known as saturated air.

(f) What is the latitudinal extension of the equatorial climate? 

Ans. The equatorial climate prevails in the region bounded between the equator and 10° N and S lines of latitudes.

(g) in which climate is the ‘campos’ grassland found? 

Ans. The grassland named ‘campos’ is found in the savanna climate that exists in the grasslands of Brazil.

(h) Mention the latitudinal extension of the temperate desert climate region.

Ans. The temperate desert climate region lies between 30° and 40° N and S of the equator.

(i) What is the other name of the Chinese climate? 

Ans. The other name of the Chinese climate is temperate humid climate. 

(j) Give an example of the irregular wind. 

Ans. Cyclones are an example of the irregular wind.

(k) Why does the warm air mass have the capacity to hold more water vapour? 

Ans. Temperature causes air to expand and thus density of air decreases. When air density decreases, air becomes light and light air is able to hold more water vapour. Such air goes up and is able to collect the moisture present in the atmosphere. In this way, the warm air mass has the capacity to hold more water vapour.

(l) Why is there more atmospheric pressure at the lower level of the atmosphere?

 Ans. Air is compressible and hence the air at the lower layer of the atmosphere gets much compressed resulting in the increase in its density. When density of air increases, its pressure also increases. Therefore, there is more atmospheric pressure in the lower layer of the atmosphere.

SEBA Class 9 Geography(Elective) Question Answer| English Medium|

UNIT-I: PHYSICAL GEOGRAPHY

CHAPTERCHAPTER NAMELink
Chapter 1Weather and ClimateClick Here

UNIT-II: HUMAN GEOGRAPHY

Chapter 2People on the EarthClick Here
Chapter 3Population Growth and DistributionClick Here
Chapter 4Human SettlementClick Here

UNIT-III: ECONOMIC GEOGRAPHY

Chapter 5Concept and Classification of ResourceClick Here
Chapter 6Economic Activities or OccupationClick Here
Chapter 7AgricultureClick Here
Chapter 8IndustryClick Here

ADDITIONAL QUESTIONS AND ANSWERS

Very Short Questions and Answers:

1. What keeps the atmosphere attached to the earth’s surface?

Ans. Gravitational force.

2. What is the climate of North-east India? 

Ans. Tropical monsoon climate.

3. In which layer of the atmosphere does the formation of clouds and rainfall take place?

Ans Troposphere.

4. Which area of the earth has the highest atmospheric pressure? 

Ans. Poles.

5. Which region of the earth has the lowest atmospheric pressure?

Ans. Equatorial region.

6. Give another name for the savanna climate.

Ans. Sudan climate.

7. Name a region in North America which enjoys a Mediterranean climate.

Ans. California.

8. Which climate is found to be ideal for the production of horticulture varieties of fruits?

Ans. Mediterranean climate.

9. Which climatic region is known as the Chinese type of climate?

Ans. Temperate humid climate.

10. Which winds bring rain to India in summer?

Ans. South-west monsoon winds. 

[B] Define/give meanings of the following:

1. Atmosphere.

Ans. The gaseous layer of air that extends upward from the earth’s surface and surrounds the earth is known as the atmosphere.

2. Hydrological cycle.

Ans. The exchange of water between the hydrosphere and the atmosphere is known as the hydrological cycle..

3. Absolute humidity. 

Ans. The actual amount of water vapour present in a definite volume of air is called absolute humidity.

4. Maritime climate.

Ans. Maritime climate is the climate which prevails at the places situated near the seas and oceans experiencing neither too warm nor too cold climate and much less temperature variation between summer and winter.

5. Continental climate.

Ans. The places located in the interior of the continents experience high temperature and the variation in summer-winter is also very high. This type of climate is called continental climate. 

[C] Answer the following questions:

1. What is the rate of decrease of temperature as one moves upward in the troposphere? 

Ans. As one moves upward in the troposphere, the temperature decreases at the rate of 6.5°C per kilometre. 

2. What is the chief cause for the changes in the atmosphere? 

Ans. The chief cause for changes in the atmosphere is temperature variation caused by the differences in the inclination of sun rays falling on the earth’s surface.

3. Which are the main factors that bring about variations in atmospheric pressure? 

Ans. The main factors that bring about variations in atmosphere pressure are air temperature and surface elevation.

4. What is the relationship between temperature and atmospheric pressure? 

Ans. The relationship between temperature and atmospheric pressure is that when temperature increases, atmospheric pressure decreases.

5. In what way does latitude influence weather and climate? 

Ans. Latitude influences weather and climate because temperature decreases as one moves from the equator towards the poles.

6. Name the major desert regions that lie close to the Tropic of Cancer.

Ans. The major desert regions lying close to the Tropic of Cancer are the Thar desert, Sahara desert, Saudi Arabia, south western part of the United states and western part of Mexico. 

7. Which are the desert regions that lie close to the Tropic of Capricorn? 

Ans. The major desert regions that lie close to the Tropic of Capricorn are the desert regions of Australia, Kalahari desert and Atacama desert.

8. Which are the main temperate grasslands of the world? 

Ans. The main temperate grasslands of the world are prairies of Canada and the USA, the steppes of Russia, the downs of Australia, the veld of South Africa and pampas of Argentina.

9. What is the latitudinal position of the monsoon climate? 

Ans. The latitudinal position of the monsoon climate is that it generally prevails between 10°N and 40°N lines of latitudes.

10. What is the latitudinal position of the Mediterranean climate?

Ans. The latitudinal position of the Mediterranean climatic region is that it lies between 30° and 45° N and S of the equator.

11. What are the major pressure belts of the world?

Ans. The major pressure belts of the world are:

  1.  Equilateral low pressure belt 
  2. Subtropical high pressure belt
  3. Sub-polar low pressure belt 
  4. Polar high pressure belt

Short Questions and Answers:

1. What are the different layers of the atmosphere? Which is the closest layer to the earth’s surface?

Ans. The atmosphere consists of the following four layers:

  1. Troposphere
  2. Stratosphere
  3. Mesosphere
  4. Thermosphere

The layer closest to the earth’s surface is the troposphere.

2. What is the troposphere? What are its main features? 

Ans. The lowest layer of the atmosphere is known as the troposphere.

Its main features are: 

  1. As this layer is attached to the earth’s surface, it contains lots of moisture and water vapour.
  2. All weather phenomena such as formation of clouds, rainfall, etc. take place in this layer.

3. Name some regions that have equatorial climate. 

Ans. The equatorial climate is experienced in the regions close to the equator which includes Northern Australia, New Guinea, Indonesia, Malaysia, Congo, Amazon basin, etc.

4. What is the latitudinal position of the humid east-coast climate? Name the regions that experience this type of climate. 

Ans. The humid east-coast climate is located in the east coastal regions of the continents between 50° and 60° N and S lines of latitudes. The east coast of Canada, Manchuria, Korea, North Japan and south-eastern coast of South America experience this type of climate.

5. Where do we find temperate desert climate? Name the various temperate desert regions of the world. 

Ans. The temperate desert climate prevails in the central parts of the continents located between 30° and 40° N and S of the equator. The regions that enjoy this type of climate include Gobi desert, Tarim, Turfan, Turkmen and some parts of Iran, Idaho, Utah, Nevada of North America and Patagonia deserts of South America.

6. What is known as the rain shadow area? Give an example. 

Ans. Generally hills and mountains block the moisture-laden winds and this forces these winds to go up, cool, condense and fall down as rain on the windward side of the mountains. As a result, the leeward side of the mountain, i.e. the other side of the mountain does not get much rain. The region that lies in this part or close to this region is known as rain shadow area. e.g. Tibetan plateau which lies in the rain shadow area of the Himalayas remains devoid of rainfall.

7. How do atmospheric conditions change according to place and time?

Ans. Atmospheric conditions vary depending on the place and time. The main reason for this variation is the differences in the inclination of sun rays. Some places get direct sunlight while others get slanting sun rays. Therefore, different places experience different temperatures at the same time. Temperature differences bring about differences in atmospheric pressure, humidity and rainfall leading to variations in atmospheric conditions of a place. Similarly, places get different types of sun rays during different seasons bringing about in the process temperature variations. This in turn, brings about variations in atmospheric pressure. Therefore, the same place will have different atmospheric conditions during different seasons of the year.

8. Which instrument is used for the calculation of atmospheric pressure? How is it calculated? 

Ans. An instrument named a barometer is used to measure the atmospheric pressure of a place. This instrument consists of a tube which is inserted into a pot of mercury. Mercury level goes up depending on the pressure of the air around. One-inch of height of mercury in the tube stands for 33.9 millibar. Average pressure at the sea level is equal to 29.92 inch of mercury level or 760 mm of mercury column. Therefore average atmospheric pressure at sea level is 1013.2 mb. approximately.

9. Which are the different categories of wind?

Ans. The main categories of wind are: 

  1. Permanent or planetary winds
  2. Periodical winds
  3. Irregular winds
  4. Local winds 

10. Mention the latitudinal location of the mediterranean climate. Which parts of the world enjoy this type of climate?

Ans. The Mediterranean climate prevails in the western coastal regions of the continents lying between 30° and 45° N and S of the equator. In the northern hemisphere, this climate prevails in the countries that lie along the Mediterranean sea and California in the US. In the southern hemisphere, this climate is found in the Chilean coast, southern coast of Africa and south-western coast of Australia.

Give Reasons – why:

1. Atmospheric pressure decreases with height. 

Ans. Atmospheric pressure decreases at the rate of 34 mb for every 900 feet of height. In other words, as we go up from the sea level through the atmosphere the depth of the atmosphere decreases which causes density to decrease. When density decreases, atmospheric pressure also decreases.

2. The water vapour holding capacity of the atmosphere vary. 

Ans. Due to differences in the inclination of the sun rays falling on the earth’s surface, the temperature of the atmosphere varies according to seasons and height. Differences in temperature bring about differences in water vapour holding capacity of the air. Warm air can hold more water vapour and cold air can hold comparatively less amount of water vapour. Thus, the water vapour holding capacity of the atmosphere varies from time to time and place to place. 

3. Atmospheric conditions vary from place to place.

Ans. The atmospheric conditions vary from place to place due to differences in the inclination of the sunrays. Some places get direct sunlight while others get slanting sun rays which are less intense in heat and light. Polar regions get oblique sun rays which do not have much heat or light. As a result, temperature varies from place to place. When temperature varies, it affects the pressure, humidity, wind, precipitation and rainfall. Due to this reason, atmospheric conditions vary from place to place.

4. Temperature decreases from the equator to the poles. 

Ans. The temperature decreases from the equator to the poles because sunrays become more and more oblique from the equator to the poles. Oblique rays have to travel a longer distance through the atmosphere and therefore, these have low intensity of heat. Thus, temperature decreases from the equator to the poles.

5. Shillong experiences a much colder climate than that of Allahabad though both are situated on the same latitude. 

Ans. Although Allahabad and Shillong are situated on the same latitude, yet both these cities experience different types of climates. Shillong has a much colder climate than that of Allahabad. This is because Shillong is situated on a higher elevation than that of Allahabad. Temperature decreases at the rate of 6.5°C per kilometre of height. Hence, Shillong has a colder climate than that of Allahabad.

6. The Ganga-Brahmaputra valley receives heavy rainfall during the monsoon season.

Ans. During the monsoon season, south-west monsoon winds blow from the Indian Ocean and the Bay of Bengal towards north India. As these winds proceed ahead, the moisture-laden winds are blocked by the high southern slopes of the Himalayas forcing the winds to go up, cool, condense and fall down as rain on the windward side of the mountains. The Ganga Brahmaputra valley lies very close to the windward slopes of the Himalayas. Hence, this region gets an abundance of rainfall.

7. The Tibetan plateau receives very little rainfall although the Himalayan foothills receive high rainfall. 

Ans. The moisture-laden south-west monsoon winds coming from the Indian Ocean and the Bay of Bengal are blocked by the southern slopes of the Himalayas forcing these winds to go up, cool, condense and fall down as rain on the windward side of the Himalayas. Hence, the foothills of the Himalayas receive heavy rainfall during summer. On the other hand, Tibetan plateau which lies on the leeward side, i.e. the rain shadow area of the Himalayas, gels very little rainfall.

Long Questions and Answers: 

1.Explain briefly the vertical and horizontal distribution of temperature.

Ans. The distribution of temperature in the atmosphere takes place in two ways: 

  1. Vertical distribution of temperature: The distribution of temperature from the earth’s surface towards the thermosphere, topmost layer of the atmosphere, is known as vertical distribution of temperature. In the troposphere, the lowest layer of the atmosphere, the temperature decreases at the rate of 6.5°C per kilometre of height (altitude) in the atmosphere. This is known as the lapse rate of the temperature. In the layers beyond the troposphere, the variation of temperature differs.
  2. Horizontal distribution of temperature : The distribution of temperature over the surface of the earth from the north pole to south pole is known as horizontal distribution of temperature. Since the earth is inclined by 23 1⁰/2 at its axis, different regions of the earth experience varied temperatures. The hottest region of the earth is the equatorial region. Temperature decreases from the equator towards the poles. Secondly, as the land is heated more quickly than water, the temperature over the land surface and water also varies in different seasons. The temperature also difiers near the sea coast due to the influence of the ocean currents and sea breeze.

2. Give an account of the vertical and horizontal distribution of pressure of the atmosphere. 

Ans. Atmospheric pressure varies in both horizontal and vertical direction in the following ways. The average atmospheric pressure at the sea level at 15°C is 1013.2 mb (millibar) but as one moves upward, air pressure decreases by one inch of mercury column or at the rate of 34 mb per 900 feet of height in the atmosphere. However, this rate is not constant in all the layers of the atmosphere and it varies depending on the layer of the atmosphere.

  1. Horizontal distribution of pressure: Atmospheric pressure is highest on the two poles of the earth. On the other hand, atmospheric pressure is quite low in the equatorial region due to increase in the temperature. As the air gets heated, it moves upwards creating a low pressure belt in the region. Further, atmospheric pressure varies according to the change of seasons which occurs due to variation in temperature. As a result, atmospheric pressure also varies from place to place in different seasons.

3. Give a brief description of the various climate types.

Ans. A brief description of the different types of climate are: 

  1. Equatorial climate: The equatorial type of climate is found in the region lying between the equator and 10° N and S lines of latitudes. This region experiences high temperature and high rainfall throughout the year. On an average, this region receives more than 200 cm of annual rainfall. Therefore, this region has extensive forests of evergreen type. The main areas enjoying equatorial climate are Northern Australia, New Guinea, Indonesia, Malaysia, Congo and Amazon basin. 
  2. Monsoon climate: The monsoon climate is experienced in the eastern parts of the countries in the northern hemisphere lying between 10°N and 40° N latitudes. This region experiences summer temperature between 27° C and 32°C. The average annual rainfall is between 100 and 200cm. The regions that receive annual rainfall between 100 and 200cm have deciduous type of forests while regions that get more than 200cm of rainfall have evergreen forests. The main areas that have this type of climate are India, Bangladesh, South-east Asia, Southern China, Southern Japan, North-east Africa, Mexico, Florida, Northern parts of Australia and Malagasy.
  3. Savanna climate: The savanna type of climate is also known as sudan type climate. This climate prevails in regions such as Sudan, Central India, North-central Africa, Southern Brazil, Argentina, Venezuela and Central parts of Central Australia. The average summer temperature is 27°C-28°C and average winter temperature varies from 10°C to 15°C. The rainfall varies from 25cm to 40cm which encourages the growth of extensive grasslands. Such grasslands of Africa are called ‘Savanna’ while those of Brazil are called ‘Campos’.
  4. Hot desert climate: The hot desert climate prevails in the hot desert regions. This region experiences summer temperatures of more than 30°C and average winter temperature is about 10°C. This region gets very little rainfall. The main desert regions that come under this climatic type are the Thar desert, Sahara desert, Saudi Arabia, south-western parts of the USA, western parts of Mexico, Kalahari, Atacama deserts and desert regions of Australia.
  5. Temperate desert climate: The temperate desert climate region lies between 30° and 40° north and south of the equator. This climatic region gets less than 10 cm of rainfall annually. The average summer temperature varies from 30°C to 42°C and average winter temperature drops below 0°C with frequent snowfalls. The main temperate desert regions are Gobi deserts, Tarim, Turfan, Turkmen and certain regions of Iran, Idaho, Utah and Nevada desert regions of USA, Patagonia deserts of South America.
  6. Mediterranean climate: The latitudinal location of the Mediterranean climatic region is 30° and 45° north and south of the equator. The summer temperature of this region varies from 21°C to 27°C while winter temperature ranges from 10°C to 13°C. This region experiences rainfall in winter. The main areas having this type of climate include regions around the Mediterranean sea, Chilean coast, southern coast of Africa, south-west coast of Australia, California in the US, etc. The main types of vegetation found in this region are evergreen and deciduous types. This region is ideal for the cultivation of horticultural varieties of fruits.
  7. Temperature humid climate: Temperate humid climate or humid type of climate is found in the regions that lie between 25° and 40° lines of latitudes. The average summer temperature of this region varies from 10°C to 13°C and winter temperature ranges from 10°C to 13°C. The annual average rainfall varies from 60 to 100 cm. Rainfall occurs mostly during summer and the vegetation mostly consists of evergreen and deciduous trees.
  8. Temperate grassland climate: The temperate grassland climate is found in the region that lies between 15° and 40° N and S lines of latitudes. The average summer temperature of this climate varies from 15°C to 20°C while winter temperature drops lower than 0°C. This region gets rainfall between 25 cm to 50 cm which is ideal for the growth of tall grass. As a result, this region has extensive grasslands such as the prairies of Canada and USA, the steppes of Russia, the downs of Australia, the veld of South Africa and the pampas of Argentina.
  9. Temperate maritime climate: Temperate maritime climate is found in the regions that lie between 40°N and S and 60°N and S lines of latitudes. The average summer temperature of this region varies from 15°C to 18°C and average winter temperature is between 5°C and 10°C. This climatic region gets rainfall throughout the year due to the influence of westerlies. On an average, some regions receive more than 500 cm of rainfall annually. Since this type of climate is mostly found in the western coastal region, it is also called west coastal climate.
  10. Humid east-coast climate: The humid east-coast climate is found in the region that lies between 50° and 60°N and S lines of latitudes. The average summer temperature varies from 15°C to 20°C while the average winter temperature ranges from 6°C to 7º C. This climatic region gets 100cm of rainfall on an average annually.

The main areas that come under this climatic type include the east-coast of Canada, Manchuria, Korea, North Japan and south-eastern parts of South America.

  1. Sub-polar (taiga) climate:The sub-polar (Taiga) climate is experienced in the sub-polar region lying between 50° and 65° N and S lines of latitude. The average summer temperature ranges from 10°C to 30°C while average winter temperature goes down to 2.5°C. This climatic region experiences heavy snowfall and very little rainfall. The main vegetation found in this region is the coniferous forests. These coniferous forests are called Taiga in Siberia.
  2. Tundra climate: The regions lying within the Arctic and Antarctic circles experience Tundra climate which prevails in the northern-most parts of Asia, Canada and Antarctica. The region under this climate receives sunshine of low intensity for almost six months and the remaining six months are night. Summer temperature hardly goes up to 10°C while winter temperature drops down below 0°C. As the surface remains covered with ice for nine months of the year, so only lichens and some mosses grow. The population is sparse with some Eskimos and only a few other hunter groups live in such extreme cold climates.
  3. Mountain climate: Due to high elevation, mountains have different climatic conditions depending on the height. Equatorial type of climate prevails along the foothills region and with the increase in height climate changes. The Alpine climate exists in the middle portion. Here the air remains cold and moderate rainfall takes place. Vegetation such as grasses, shrubs, and coniferous trees are found here. The Alpine climate is suitable for sheep and cattle rearing. At high altitude, ‘tundra’ type of climate prevails. This type of climate is found in the high ranges of the mountains such as the Himalayas, Alps, Rockies, Andes, etc.

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