1. How do the following factors influence the climate of India?
(a) Latitude (b) Altitude
(c) Distance from the sea
Ans. (a) Latitude Tropic of Cancer divides India into equal halves. The region lying North to it has sub-tropical climate, whereas South to it has tropical climate.
(b) Altitude It means the height from the sea level. With increase in height from the earth surface the temperature decreases and air becomes less dense. India has mountain ranges (the Himalayas) in the North with an average elevation of about 6000 m, whereas on the
coastal areas as well as islands, maximum elevation is about 30m. The Indian sub-continent experiences mider winters as the Himalayas act as a barriers against the cold arctic winds and stop them to enter in India.
The Himalayas also stop the South-West monsoon winds to escape from India and the whole Northern India experiences monsoon season.
(c) Distance from the Sea The regions located near the sea have moderate climate and those lying away from it have extreme climate. This is due to moderating influence of ocean current.
2. How is the climate of India governed by the atmospheric condition? Explain with three suitable examples.
Ans. The atmospheric condition plays vital role in determining the climate of any region.
The climate of India is governed by the following atmospheric conditions
(i) Pressure and Surface Winds
The surface winds blow from region of high pressure to the region of low pressure.
During winter, the high-pressure area lies North of Himalaya. Over the ocean in the South, there is low pressure .So, wind blows from land towards the sea. The reverse occurs during summer.
(ii) Upper Air Circulation
The North Easterly wind originate in sub – tropical high pressure belt of Northern hemisphere. They blow South and get deflected towards right (due to Coriolis force) over the low-pressure area of Indian sub-continent. They are dry and cold, and cause no rainfall.
Sub-tropical westerly jet stream brings Western cyclonic disturbances in North and North – Western India during winter.
(iii) Tropical Cyclone
They are part of easterly flow. They cause heavy to very heavy rainfall in Eastern coast of India during monsoon as well as in October- November.
3. What is the coriolis force? Describe briefly its effect on the world climate.
Ans. Coriolis Force :
It is an apparent force caused by the Earth’s rotation. It is responsible for deflecting winds towards the right in the Northern hemisphere and towards the left in the Southern hemisphere.
Effect of Coriolis Force on the World Climate :
Under the effect of Coriolis force, the trade winds moving from sub-tropical high-pressure belts to equatorial low-pressure belts become North-East trade winds in the Northern hemisphere and South-East trade winds in the Southern hemisphere. As a result, they bring heavy rainfall to the East coast while the West coast remains dry.
4. What are Western disturbances? How do they affect the climate of India?
Ans. The Western disturbances are weather phenomena brought in by westerly flow from the Mediterranean region. They occur in the month of winter and cause rainfall in North and North-Western part of India.
They affect the climate of India in the fallowing ways
(i) By causing cyclonic rainfall in the month of winter, which is ‘ otherwise dry, Western disturbance influences the weather of the North and North-Western India.
(ii) Although the amount of rainfall is meagre, it is highly beneficial to the Rabi crops, especially the wheat.
(iii) They cause snowfall in the mountains.
- What is the ITCZ? What is its significance?
Ans. Inter Tropical Convergence Zone (ITCZ) It is a broad trough of low pressure in equatorial latitudes from about 5° N to 5°S. It moves North or South with the apparent movement of sun.
Significance of ITCZ (i) The ITCZ is a zone of convergence of North-East and the South-East trade wind. (it) The Northward or Southward movement of it determines the spatial distribution of rainfall.
(iii) This zone is the wettest area on the planet, which does not have a dry season. Thus, it is constantly hot and humid.
- What is ‘EL Nino’? Explain any two features of it.
Ans. EL Nino The periodic development of warm ocean current along the coast of Peru as a temporary replacement of the cold Peruvian current, is called EL-Nino.
Features of EL Nino
(i) The presence of the EL-Nino leads to an increase in sea-surface temperatures.
(ii) It weakens the trade winds in the regions and causes heavy rainfall, floods or droughts in different regions of the world.
- Define burst of monsoons. Give an account of the climatic conditions of the cold weather season in India.
Ans. Burst of Monsoons When monsoons arrive in India, the normal rainfall increases suddenly and continues constantly for several days. This is called ‘burst of monsoon’.
Climatic Conditions of the Cold Weather
(i) Cold weather season prevails from November to February.
(ii) The temperature decreases from South to the North.
(iii) Days are warm and nights are cold.
(iv) The North-East trade winds prevail over the country. These winds cause some amount of rainfall on the Tamil Nadu coast.
(v) The weather is marked by clear sky, low temperatures and low humidity and feeble, variable winds.
(vi) Low pressure systems originate over the Mediterranean sea and move into India, along with the Westerly flow.
They cause the much needed winter rains over the plains and snowfall in the mountains.
- State what is monsoon. Name the two branches of monsoon and explain any one.
Ans. Monsoon It refers to the seasonal reversal in the wind direction during a year.
The two branches of monsoon are
(i) Arabian Sea branch (ii) Bay of Bengal branch
Bay of Bengal Branch
- This branch of monsoon moves along the Bay of Bengal. It advances rapidly and arrives in the North-Eastern part of the country in first week of June.
- The lofty mountains cause this branch of monsoon winds to deflect towards the West over the Ganga plains.
- It merges with .the Arabian Sea branch over the North-Western part of the Ganga plains.
- (a) How is the Arabian Sea branch of South-West monsoons responsible for good rainfall in Northern plains of India?
- Why does not it give rain in Central Peninsula?
Ans. (a) The part of South-West monsoons which blows over Arabian sea is responsible for high rainfall on the Western coast and Northern plains of India.
These winds enter through Saurashtra and enter Northern plains. These winds strike the Himalayas and , give fairly good rainfall as they have abundant moisture.
(b) South-West monsoon winds are perpendicular to the direction of Western Ghats. Thus, they give heavy rainfall on the windward side of the Western Ghats. Central Peninsula lies on the leeward side of the Western Ghats. Thus, the Arabian Sea branch of South-West monsoon does not reach this region.
- How does the change in pressure conditions over the Southern oceans affect the monsoons?
Ans. The change in pressure conditions over the Southern oceans affects the monsoon as
(i) When the tropical Eastern South Pacific Ocean experiences high pressure, the tropical Eastern Indian Ocean experiences low pressure. In this condition, the monsoon rainfall will be average.
(ii) In some years, it is reverse when pressure difference is negative – means below average and late monsoon.
(iii) The change in pressure conditions is connected to the EL Nino.
- Define ‘Kaal Baisakhi’ and ‘Loo1. In which parts of India are they experienced?
Define Kaal Baisakhi, Mango Showers and Loo.
Ans. Kaal Baisakhi These are the local thunderstorms associated with violent winds, torrential downpours, often accompanied by hail. They occur in West Bengal.
Loo These are strong, gusty, hot, dry winds blowing during the day over the North and North-Western India.
Mango Showers The pre-monsoon showers, which help in the ripening of mangoes in coastal Kerala and Karnataka are known as Mango showers.
12. Why do the Western Ghats receive more rainfall than the Eastern Ghats? Explain briefly.
Ans. Western Ghats receive more rainfall than the Eastern Ghats because
(i) Western Ghats receive rainfall from the Arabian Sea monsoon winds. As these winds blow over warm oceans, they bring abundant moisture.
(ii) The Western Ghats do not allow the winds to cross over without shedding their moisture on the Western slopes.
(iii) When these winds reach the Eastern Ghat, they are almost dry. .
(iv) Another branch of South-West monsoon i.e. the’ Bay of Bengal branch, moves parallel to the Eastern Ghats. In this way, this region is located in an unfavourable position with reference to the monsoon winds.
13. Where is Mawsynram located? Why does Mawsynram receive the highest amount of rainfall?
Ans. Mawsynram is located in the Southern ranges of the Khasi hills in Meghalaya at a height of 1500 m above the sea level. It receives the highest (annual 1140 cm)rainfall of the world.
Mawsynram receives the highest amount of rainfall because
(i) This place is enclosed by hills on three sides.
(ii) The relief features give this place funnel shaped location.
(iii) The Bay of Bengal monsoon is trapped in these hills. These winds try to get out of there, but are forced to pour down there.
14. Explain any four features of advancing monsoon with reference to India.
Ans. The advancing monsoon prevails during the months of June, July, August and September.
The features ofadvancing monsoon are
(i) It brings a total change in weather conditions.
(ii) Early in the season of advancing monsoon, the windward side of Western Ghats receives very heavy rainfall. The maximum rainfall of this season occurs in North-Eastern India.
(iii) It has wet and dry spells. The intervening dry period is called ‘Breaks’ in monsoon.
(iv) The monsoon is known for its uncertainties, and the spatial distribution of rainfall is uneven.
15. Why are South-West monsoons less rainy in TamilNadu? Explain.
Ans. Tamil Nadu lies in the Eastern coast of India.
South-West monsoon is less rainy in Tamil Nadu due to the following reasons
(i) The Arabian Sea branch hits the Western Ghats and causes heavy rainfall there. By the time it advances towards Chennai, it becomes off-shore and gives less rain.
(ii) Bay of Bengal branch blows parallel to Tamil Nadu and does not give rainfall.
16. Why does Chennai receive less rainfall through South-West monsoon?
Ans. Chennai is located in the South-Eeastern coast of India. It receives less rainfall through South-West monsoon due to the following reasons
(i) Bay of Bengal branch of South-West monsoon passes parallel to Chennai coast.
(ii) Due to the presence of Western Ghat on its way of flow, Arabian sea branch of South-West monsoon could not cross over and give little or no rain in Chennai.
17. Why are the delta regions of Eastern India struck by cyclones?
Ans. By early November, the low-pressure conditions over North-Western India, get transferred to the Bay of Bengal.
With this shift, there is occurrence of cyclonic depression (originating over the Andaman sea).
These cyclones, after coming under influence of retreating monsoon, cross the Eastern coasts (direction of flow East to West) of India. They cause heavy and widespread rain.
Therefore, the delta regions of Eastern India are struck by cyclone.
18. Why North-West India receives rainfall in winter? Give any three reasons.
Ans. North-West India receives rainfall in winter because
(i) Cyclonic disturbances occur from the West and the North-West.
(ii) These low-pressure systems originate over the Mediterranean . sea and Western Asia and move into India alongwith Westerly flow.
(iii) They cause winter rains over Punjab, Haryana and Northern plains.
19. Mention any four characteristics of the Indian monsoon.
Ans. Monsoon is the seasonal reversal of wind. India has monsoon type of climate.
It has following characteristics
(i) Monsoon which comes as South-West monsoon in Indian sub-continent proceeds into two branches after hitting the Southern tip ^
- Bay of Bengal branch
- Arabian sea branch
- Monsoon occurs in alteration of dry and wet spells. The intervening dry spells of monsoon is called ‘Breaks’ in monsoon.
- There is variation in intensity, frequency and duration of monsoon. This causes floods in one place and drought in other at the same time.
- Monsoon is often irregular in its arrival and retreat.
- Why is the distribution of rainfall in India not uniform? Explain any three reasons.
Ans. There is spatial and temporal variation of rainfall in India. Various factors contributed to this uneven distribution of rainfall in India.
(i) Relief Relief factors (e.g. high mountains and hills) act as a barrier to rain bearing winds. When such winds collide with the high mountains, they cause orographic rainfall on the windward side. The leeward side on the other hand remains drier, e.g. due to Western Ghat, the Western coastal plains get heavy rainfall.
(ii) Distance from the sea (Continentality) As the distance from the sea increases, the moisture content of the wind decreases. So, the interior of landmass are much drier than those in coastal region.
(iii) Direction of Wind The regions lying in the direction of flow of wind are rainier than those not lying on its direction, e.g. Tamil Nadu coast which lies parallel to Bay of Bangal branch does not get rainfall from South-West monsoon.
- “There is a great variation in the amount and type of precipitation in India.” Justify the statement.
Ans. There are variations not only in the forms and types of precipitation but also in its amount and the seasonal distribution. Such as
(i) In the upper parts of the Himalayas,
precipitation occurs most likely in the form of snowfall, whereas it rains over the rest of the country.
(ii) Parts of Western coast and North-Eastern India receive over about 400 cm of rainfall annually, e.g. Meghalaya. On the other hand, some regions like Ladakh, Western Rajasthan, parts of Gujarat and the Leeward side of Western Ghats receive rainfall less than 10 cm annually.
Thus, it can be concluded that there is a great variation in the amount and type of precipitation.
- Chennai receives rainfall in winter. Why?
Ans. Chennai receives rainfall in winter due to the following reasons
(i) The North-East winds pick up moisture while crossing Bay of Bengal. These winds are on-shore in Tamil-Nadu coast and hence cause rainfall there.
(ii) During the months of October and November, the low-pressure area over North-Western India get transferred to the Bay of Bengal. This shift is associated with cyclonic depression which originate over Andaman sea and causes rainfall in coastal areas e.g. in Chennai.
- Why is it said that “Monsoon wind is known for its uncertainties”? Explain any fours reasons.
Ans. Monsoon wind is known for its uncertainties because
(i) The movement of low-pressure trough controls the spatial distribution of rainfall.
(ii) The alteration of wet and dry spells varies in intensity, frequency and duration.
(iii) It sometime causes heavy floods in one part, it may be responsible for drought in other.
(iv) It is often irregular in its arrival and retreat.
- “Indian monsoon is said to be a unifying bond for the people of the country.” Suppose the monsoon is disturbed for a prolonged period of time. What do you think, how will it affect the country?
Ans. In the following ways, it will affect the country
(i) There will be a change in landscape.
(ii) The fauna and flora will be disturbed.
(iii) Due to change in cycle of season, Indian agricultural cycle will be disturbed.
(iv) Many of the festivals like Baisakhi, Pongal, Onam, Bihu, etc will come to an end.
(v) Rivers will run short of water so religious rituals will be disturbed.
(vi) Drinking water will go^short.
(vii) River navigation and many of the recreational activities will come to a halt.
25. study the following climatic data and answer the questions that follow.
- Name the rainiest month of the year. How much is the rainfall in this month?
- What is the annual range of temperature here?
- Name the hottest month and write the temperature.
Ans. (a) The rainiest month of the year is July. The rainfall in this month is 19.3 cm.
(b) The annual range of temperature is 33.3°C -14.4°C = 18.9°C
(c) The hottest month of the year is June and the temperature is 33.3°C.
26. Study the climate data of a station given below and answer the following questions.
- Calculate the annual range of temperature of this station.
- Which month receives less rainfall and how much?
Ans. (a) The annual range of temperature is the difference between the highest and the lowest temperatures recorded in the given year.
The highest temperature recorded = 26.7 °C The lowest temperature recorded = 10.9 °C Annual range of temperature = 26.7 °C —10.9 °C = 15.8°C
(b) (i) The month that received the lowest rainfall is January.
(ii) The rainfall in January was 7mm.
27. Some terms related to the climate of India are given below. Classify them into the seasons in which they fall (Winter, Summer, Advancing Monsoon and Retreating Monsoon).
28. Bring out any one similarity and two differences between climate and weather.
Ans. Similarity between climate and weather
Both weather and climate have the same elements i.e. humidity, precipitation, temperature, wind and atmospheric pressure. Both indicate the atmospheric condition of a region.
Differences between climate and weather
- “You have visited a place as a leader of your school team. The Principal has asked you to make a report on the climate of the place”.
To conclude about the climate which factors would you take into consideration?
Ans. The factors that can be taken into consideration to conclude about the climate are
(i) Latitude of the place (ii) Distance from the sea
(iii) Altitude of the place (iv) Precipitation received at the place
(v) Relief features of the place
30. Differentiate between the cold weather season and the hot weather season in India by explaining two distinctive features of each.
Ans. Differences between the cold weather season and the hot weather season are as follows
31. Distinguish between the South-West monsoon and North-East monsoon.
Ans. Differences between the South-West monsoon and North-East monsoon are as follows