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CBSE Class 9 Social Science Climate Exam Notes WEATHER AND CLIMATE
Weather Climate 1. It refers to short run atmospheric conditions 1. Climate is the aggregate of day to day weather that exist for a given time in a specific area. conditions over a long period of time. 2. It refers to a particular station. 2. Climate refers to a large area. 3. It may change at a very short interval of time. 3. Climate remains more or less unchanged year after year. 4. It is influenced by any one of its predominant 4. It is the collective effect of all its elements. elements i.e. temperature, humidity.
CLIMATE OF INDIA
The climate of India is described as of monsoon type. Derived from an Arabic word ‘mausim’, monsoon refers to the seasonal reversal in the wind direction through the year. This type of climate is found mainly in the south and the south east Asia. Despite an overall unity and commonality in the general pattern, there are perceptible regional variations in climatic conditions within the country. The temperature touches as high as 50ºC in the western desert during the summer season, whereas it drops down as low as –40ºC in Leh during the winter. Similarly, variations are noticeable not only in the type of precipitation but also in its amount.
CLIMATIC CONTROLS
There are six major controls of climate of any place. They are - 1. latitude 2. altitude 3. pressure and wind system 4. distance from the sea 5. ocean current 6. relief features. Latitude : Due to the curvature of the earth, the amount of solar energy received varies according to the latitude. Altitude : Air temperature decreases from the equator towards the poles. As one goes from the surface of the earth to higher altitudes. The atmosphere becomes less dense and temperature decreases. The hills are therefore cooler during summer. The Pressure and Winds : The system of any area depends, on the latitude and altitude of the place. Thus it influences the temperature and rain fall pattern. Distance from the sea : The sea exerts a moderating influence on climate. As the distance from the sea increases, its moderating influence decreases. Ocean current : Ocean current along with on shore winds affects the climate of the coastal areas. Relief : It plays a major role in determining the climate of a place. High mountains act as barriers for cold or hot winds. They may also cause precipitation.
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FACTORS AFFECTING THE CLIMATE OF INDIA
Latitude : The tropic of cancer passes through the middle of the country from the Rann of Kuchchh in the west to Mizoram in the east. Almost half of the country lying south of the tropic of cancer belongs to the tropical area. All the remaining area, north of the Tropic, lies in the subtropics. Therefore, India’s climate has tropical & subtropical climate. Altitude : India has mountains, to the north, which have an average height of about 6000 metres. India has a vast coastal area where the maximum elevation is about 30 metres. The Himalayas prevent the cold winds from Central Asia from entering the subcontinent. Because of these mountains, experiences comparatively milder winter as compared to Central Asia. Pressure and winds : The climate and associated weather conditions in India are governed by the following atmospheric condition. (A) Pressure and surface winds. (B) Upper air circulation. (C) Western cyclonic disturbances and tropical cyclone. The pressure conditions exerted by the surrounding countries like East Africa, Iran, Central Asia also influence the climate condition of India. The fury of monsoons as well as long dry spell in India are mainly due to the pressure conditions in the above mentioned countries. Winds especially Typhoons, Air current and monsoon also have a great bearing on the climate of India. Typhoons originating in the China sea also have a great bearing on the weather conditions in India. Distance from the sea : The location of seas on the three sides of India has exerted a moderate influence on much of the Indian sub continent. As the distance from the sea increases its moderating influence decreases. Physiography : It plays an important role in determining the climate of a place. The location of the Himalayas in the north has acted as a great barrier to the cold winds of the north. But for the Himalayas, India would have become a cold country.
THE INDIAN MONSOON
Definition : The word monsoon comes from the Arabic word ‘mausam’ which means season. Monsoon is thus rain bearing winds which reverse their direction with the change of ‘mausam’. Facts about mechanism of Monsoons : (A) The differential heating and cooling of land and water creates low pressure on the landmass of India while the sea around experiences comparatively high pressure. (B) The shift of the position of Inter Tropical Convergence Zone (ITCZ). In summer over the Ganga plain (This is the equatorial trough normally positioned about 5º N of the equator - also known as the monsoon trough during the monsoon season). (C) The presence of high pressure area, east of Madagascar approximately at 20ºS over the Indian ocean. The intensity and position of this high pressure area affects the Indian monsoon.
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(D) The Tibetan plateau gets intensely heated during summer which results in strong vertical air currents and the formation of high pressure over the plateau at about 9 km above sea level. (E) The movements of the westerly jet stream to the north of the Himalayas and the presence of the tropical easterly jet stream over the Indian peninsula during summer. Southern Oscillation or SO : When the tropical eastern south Pacific Ocean experiences high pressure the tropical eastern Indian Ocean experiences low pressure. But in certain years, there is a reversal in the pressure conditions and the eastern Pacific has lower pressure in comparison to the eastern Indian Ocean. This periodic change in pressure condition is known as Southern Oscillation or SO. El Nino Southern Oscillations : A warm ocean current EIL-Nino, flows past the Peruvian Coast, in place of the cold Peruvian current, every 2 to 5 years. The changes in pressure conditions are connected to the El Nino. Hence the phenomenon is referred to as ENSO. The presence of the EIL-Nino leads to an increase in sea surface temperatures and weakening of the trade winds in the region.
THE ONSET OF THE MONSOON The monsoon is pulsating in nature. affected by different atmospheric conditions encountered by it on way over the warm tropical seas. Around the time of its arrival the normal rainfall increases suddenly and continues constantly for several days. This is known as the 'burst of the monsoon'. The onset of the monsoon : The monsoon arrives at the southern tip of the Indian Peninsula generally by the first week of the June. Subsequently, it divides into two - 1. The Arabian sea Branch. 2. The Bay of Bengal Branch. 1. The Arabian sea Branch reaches Mumbai about 10 days later on approximately the 10th of June. This is fairly rapid advance. 2. The Bay of Bengal branch also advances rapidly and arrives in Assam in the first week of June. 3. The lofty mountains causes the monsoon winds to deflect towards the west over Ganga plains. 4. By mid June the Arabian sea branch of the monsoon arrives over Saurashtra-Kuchchh and the central part of the country. 5. Both the branches of the monsoon merge over the northwestern part of the Ganga plain. 6. Delhi receives the monsoon shows from the Bay of Bengal branch by the end of June. 7. By the first week of July, Western Uttar Pradesh, Punjab, Haryana and Eastern Rajasthan experience the monsoon. 8. By mid July the monsoon reaches Himachal Pradesh and rest of the country.
WITHDRAWAL OF THE MONSOON
1. It is a gradual process. It begins in northwestern states of India by early September. 2. By mid October, it withdraws completely from the northern half of the peninsula. 3. The withdrawal from the southern half of the peninsula is fairly rapid. 4. By early December, the monsoon has withdrawn from the rest of the country.
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THE SEASONS
The year can be divided into the following four seasons on the basis of the monsoon variations. 1. The cold weather season : The cold weather persists from December to February throughout India. January is the coldest month. Temperature is between 10º C to 15ºC in northern plains and 25ºC in southern parts of the country. There is high pressure in northern plains due to the cold climatic conditions. The cold dry winds blow from the high pressure towards the low pressure equatorial regions. These winds are north westerly in the Ganga plains and north easterly over the Bay of Bengal. Only two parts of the country receive rain in this season. First is the north west part of India which receives rainfall from the Mediterranean cyclone. Second is the coast of Tamil Nadu which gets rainfall in winter. 2. The Hot Weather Season : During this period there is a rapid shifted belt of heat from south to north. In May, the rising temperature leads to a low pressure in a wider area from the Thar desert to Chhota Nagpur. Because of this low pressure, the moisture laden winds from the Arabian Sea are attracted toward this area and consequently there is rain fall. Kerala and Western Ghats also experience the pre monsoons showers. Assam and Bengal also receive some rainfall by means of evening thunderstorms. But the north west remains dry and hot winds called the loo, engulf the whole area. Sometimes dust storms in Punjab, Haryana and U.P. are followed by light rain and cool breeze. 3.Advancing Monsoon Season : This season runs from June to September. During these months the south west monsoon winds blow northwards into two branches from the Arabian sea and the Bay of Bengal. They make rainfall almost in the whole of northern India. These winds blow from the oceanic high pressure area towards the low pressure area of land and make heavy rainfall. The Arabian sea branche causes heavy rainfall in the coastal areas of the Western Ghat but this rainfall decreases as the monsoon goes further. Kutch receives less rain fall. The Bay of Bengal causes heavy rain fall in the hills of Meghalaya. Mawsynram receive highest rainfall in the world As the monsoon winds take a turn from east to west because of Himalayas, the rain goes on decreasing. Due to the uncertainty and uneven distribution of rainfall, floods and droughts are common during this season. 4. The Retreating Monsoon : This season runs from October to November. At this time the monsoon start retreating. The lower temperature on the plains gives rise to gradual increase in pressure and as such the monsoons retreat from most parts of North India. Depressions originate in the southern part of the Bay of Bengal and start moving towards the east coast of India. Tamil Nadu receives high rainfall from these winds during this season. The distribution and the range of rainfall is not certain even during this season.
DISTRIBUTION OF RAINFALL
1. The Western Coast and North Eastern India receive over about 400 cm of rainfall annually. 2. Western Rajasthan and adjoining parts of Gujarat receive less than 60 cm. 3. Rain fall is equally low in the interior of the Deccan plateau and east of the Sahyadris. 4. A third area of low precipitation is around Leh in Jammu and Kashmir.
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5. The rest of the country receives moderate rainfall. 6. Snow fall is restricted to the Himalayan region.
MONSOON AS A UNIFYING BOND
Effect of the Himalayas : The Himalayas extending from north west to north east act as a great meteoreological barrier. These high mountains lend the entire country, a some what tropical touch. For example the temperature is almost uniformly high throughout India during most of the year, specially during the summer months. The Himalayas act as a closed base with which the monsoon winds blow and show their unique performances. Effects of the monsoon : Moreover, the all pervading effects of the monsoons on the Indian subcontinent have also lent unity to India. With few exceptions here and there. India gets most of its rainfall due to these common winds and that to in the summer season. The concentration of rainfall over few months in a year keeps the whole land water-thirst for a greater part of the year. This thirst for water is universal throughout India. Hence, the need for developing the different means of irrigation (such as canals, wells, tube-well, etc.) is felt all over India. Thus the vagaries (uncertainties) of monsoons is felt all over the country.
GLOSSARY
1. Climate : Sum total of weather conditions and variations over a large area for a long period of time. The regular pattern of weather conditions of particular place. 2. Weather : It refers to the state of the atmosphere over an area at any point of time. 3. Range of temperature : Difference between the maximum & minimum recorded temperature. 4. Precipitation : The water that falls to the earth from the atmosphere in the form of rain, snow hail, dew etc. 5. Jetstream : The fast blowing air current in the upper level of atmosphere. 6. Monsoon : Monsoon refers to the seasonal reversal in the wind directions throughout the year. 7. Loo : It is a local wind which blows during the hot season in north India. 8. Cylone : An area of low pressure. 9. Tropical climate : A relatively high temperature almost throughout the year and predominantly dry winter. 10. October heat : It is the conditions of high temperature and humidity due to which the weather becomes oppressive. 11. Extreme climate : The climate in which the summer ins extremely hot and winter is quite cold. 12. Trade winds : Trade winds are those which blow steady in the same direction and on the same course. 13. Western Disturbance : Shallow cyclonic depression originating over the mediterranean sea and disturbing fineweather conditions in north western parts of India. 14. Windward side : The side of the mountain where moisture winds strike and bring heavy rain. 15. Leeward side : The side of the mountain which receives less rainfall. 16. Rain shadow : The rainless area on the leeward side.
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17. Break or Brust of Monsoon : The sudden approach of the moisture ladenwinds which are associate with violent thunder the lighting. 18. Catchment areas : The area from which the river derives its water from the hills. 19. Equable climate : It is one which is neither too hot in summer nor too cold in winter. typhoon - violently revolving storm.
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EXERCISE
A. VERY SHORT ANSWER TYPE QUESTIONS
Q.1 What is climate ?
Q.2 Name the elements of weather and climate.
Q.3 What does monsoon imply ?
Q.4 Mention the major factors that control the climate of any place.
Q.5 What is Southern Oscillation ?
Q.6 What is El Nino ?
Q.7 Where are monsoon winds confined in India ?
Q.8 Where does the law pressure area develop in May ?
Q.9 Name the two branches of the monsoon ?
Q.10 What are the ‘retreating monsoon’ ?
Q.11 Why does Tamil Nadu coast receive winter rainfall ?
Q.12 What is jet stream ?
Q.13 What is the importance of Jet stream ?
Q.14 Name two states where mango showers are common ?
Q.15 What is meant by breaking of monsoon ?
Q.16 Name some regions for which the tropical cyclone are very destructive.
Q.17 What is loo ?
Q.18 Name two hottest stations in the month of May.
Q.19 Write the main features of monsoon rain in India.
Q.20 What is cold wave ?
Q.21 Name the states where dust storms are very common.
Q.22 How is average rainfall calculated ?
Q.23 Write any one effect of Jet stream ?
B. SHORT ANSWER TYPE QUESTIONS
Q.1 India has diverse climate condition. Explain.
Q.2 Why do south-westerly winds cause rain in India ?
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Q.3 Which are the rainest months of India. Give reason.
Q.4 Why are the parts of Rajasthan, Gujrat and leeward side of the western Ghats drought - prone ?
Q.5 ‘Chennai gets more rainfall in winter than in summer’. Give two reason.
Q.6 Name and give the direction of winds that cause snow and rainfall in the northern parts of India during winter season.
Q.7 Name the months which are known for retreating monsoon. Write some which are known for retreating monsoon. Write some main features of this climate.
Q.8 What is October heat ?
Q.9 What are western disturbances ? Name two areas receiving rains from them. Write any one benefit of these.
Q.10 What are Jet streams ? How do they help to cause rain in Punjab and western Himalayas during the winter ?
Q.11 Why do premonsoon showers remains localised ?
Q.12 What is the difference between cyclone and anticyclone ?
Q.13 Why does Mawsynram in Meghalaya receive the highest rainfall in the world ?
Q.14 Why is Cherapunji rainier than Kolkata ?
Q.15 Why does Delhi receive more rain then Jodhpur ?
Q.16 Distinguish between summer and winter monsoon.
Q.17 Distinguish between windward and leeward side.
Q.18 How are the nature and mechanism of monsoon understood ?
Q.19 Mention any three feature of the distribution of annual rainfall in India.
Q.20 Write two features of “mango showers”.
C. LONG ANSWER TYPE QUESTIONS
Q.1 Discuss the distribution of precipitation in the country and the consequences of its uneven distribution.
Q.2 Discuss the factors which influence the climate of India.
Q.3 Describe how the location and relief are important factor in determining the climate of India.
Q.4 Discuss the main features of hot weather season in India. Also write its duration.
Q.5 What is a climatic divide ? How do the Himalayas act as climatic divide ?
Q.6 Describe the main features of advancing monsoon under the following heads.
(I) Duration (II) Pressure condition
(III) Prevailing winds (IV) Rain fall
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Q.7 Describe the main features of Retreating monsoon under the following heads. (A) Duration (B) Pressure conditions (C) Prevailing (D) Rain fall
Q.8 Describe the regional variations in the climatic candition of India with the help of suitable examples?
D. MULTIPLE CHOICE QUESTIONS
Q.1 Where is monsoon type of climate mainly found ?
(A) South and South East Asia
(B) North and Northwest Asia
(C) North Asia
(D) West Asia
Q.2 Which part of India experiences the highest range of temperature in a day ?
(A) North India (B) Thar desert
(C) Western part (D) All the above
Q.3 Where does malabar coast lie ?
(A) Eastern Ghat (B) South India
(C) Western Ghat (D) None of these
Q.4 Name two coldest areas in India -
(A) Srinagar and Jammu
(B) Dras and Kargil
(C) Shilong and Kolkata
(D) None of these
Q.5 Name the place in India receiving highest rainfall-
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(A) Mawsynram (B) Delhi
(C) Chennai (D) Mumbai
Q.6 Name two states where mango shower are common -
(A) Rajasthan & Bihar
(B) Gujarat and Tamil Nadu
(C) Uttar Pradesh & Madhya Pradesh
(D) Kerala & Karnataka
Q.7 Name two months associated with retreating monsoon -
(A) July & August
(B) October & November
(C) May & June
(D) All the above
Q.8 What is the name given to the climate of India ?
(A) Cold climate (B) Warm climate
(C) Monsoon climate (D) All the above
Q.9 The local wind which is hot and dry is called-
(A) Cyclone (B) Trade wind
(C) Jet (D) Loo
Q.10 From where do western disturbances come to India ?
(A) Pacific ocean (B) Mediterranean sea
(C) Indian ocean (D) Bay of Bengal
Q.11 What kind of weather precedes western disturbances ?
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(A) Cold weather (B) Warm weather
(C) Both (D) None of these
Q.12 What is the velocity of rain bearing winds during the monsoon -
(A) 30 km per hour (B) 40 km per hour
(C) 50 km per hour (D) 45 km per hour
Q.13 Name the water body from which the cyclonic depression origins -
(A) Nicobar sea (B) Bay of Bengal
(C) Arabian sea (D) Andaman sea
Q.14 Name the hill which deflects the Bay of Bengal branch of advancing monsoon to India-
(A) Nilgiri hills (B) Vindhya hills
(C) Arakan hills (D) None of these
Q.15 Monsoon arrives in India approximately in -
(A) Early May (B) Early June
(C) Early July (D) Early August
ANSWER KEY
Q.No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Ans. ABCBADBCDBBBDCB