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Climate-9th Geography

This PPt may be useful for the 9th std students. it is based on the 9th Std Geography (CBSE) book. for better understanding, some of the other related PPTs and pictures are also included in this PPT. Let enjoy your studies. yours.. R. Ezhilraman, PGT-Social Science, JNV Lepakshi, Ananthapur Andhra Pradesh

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Climate-9th Geography

  1. 1. 02-03-2015 R. Ezhilraman, PGT-Social Science 1 R. Ezhilraman PGT-Social Science JNV Lepakshi Subject: Geography For Class: IX
  2. 2. What is Climate? Climate is the characteristic condition of the atmosphere near the earth's surface at a certain place on earth. It refers to the sum total of weather conditions and variation over a large area for a long period of time. It is the long-term weather of that area which remains at least 30 years. 02-03-2015 R. Ezhilraman, PGT-Social Science 2
  3. 3. Weather refers to the state of atmosphere over an area at any point of time. The elements of both weather and climate are same. It is the combination of temperature, humidity, precipitation, wind, cloudiness and other atmospheric conditions at a specific time. What is Weather? 02-03-2015 R. Ezhilraman, PGT-Social Science 3
  4. 4. Monsoon The word monsoon is derived from the Arabic word ‘mausim’ which literally means season. ‘Monsoon’ refers to the seasonal reversal in the wind direction during a year. The World is divided into a number of Climatic Regions. The Climate of India is described as the ‘monsoon’ type. This type of climate is found in South and Southeast Asia. But, there are perceptible regional variations in climatic conditions within the country. Two important elements viz., temperature and precipitation, often vary from place to place and season to season. 02-03-2015 R. Ezhilraman, PGT-Social Science 4
  5. 5. Difference in Temperature In summer, the temperature in parts of Rajasthan Desert is 50°C, and it is around 20°C in Pahalgam in J & K. On a winter night, temperature at Drass in J & K may less than -45°C, and at Tiruvananthapuram it may be of 22°C. In some places temperature between day and night temperature differs. In the Thar Desert, it rise to 50°C, in day and drop down to near 15°C in night. But in the Andaman and Nicobar islands or in Kerala, there is no much difference in day and night temperatures. 02-03-2015 R. Ezhilraman, PGT-Social Science 5
  6. 6. Precipitation Precipitation varies in its form, types and amount and seasonal distribution. It is in the form of snowfall in the upper parts of Himalayas, it rains over the rest of the country. The annual precipitation varies from 400 cm in Meghalaya to less than 10 cm in Ladakh and western Rajasthan. Most parts of the country receive rainfall from June to September. But Tamil Nadu coast gets rain during October and November. Rainfall generally decrease from east to west in the Northern Plains. These variations have given rise to variety in lives of people, their food, clothes and houses. 02-03-2015 R. Ezhilraman, PGT-Social Science 6
  7. 7. Vegetation 02-03-2015 R. Ezhilraman, PGT-Social Science 7 Vegetation can affect both temperature and the precipitation patterns in an area.
  8. 8. 02-03-2015 R. Ezhilraman, PGT-Social Science 8
  9. 9. FACTORS AFFECTING CLIMATE RELATED TO LOCATION RELATED TO AIR PRESSURE & WIND •Latitude •The Himalayan Mt. •Distribution of Land & water •Altitude •Distance from Sea Surface pressure & wind Upper air circulation Western cyclones•Relief Features 02-03-2015 R. Ezhilraman, PGT-Social Science 9
  10. 10. Latitude Latitude is the distance a place lies north or south of the equator and is measured by an imaginary line called lines of latitude. 02-03-2015 R. Ezhilraman, PGT-Social Science 10
  11. 11. EQUATORIAL REGION LATITUDE High Temp Low range High range of Temp 02-03-2015 R. Ezhilraman, PGT-Social Science 11
  12. 12. Latitude  As latitude increases, the intensity of solar energy decreases. Due to curvature of the Earth, the amount of solar energy varies according to latitude.  In India, 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 sub-tropics. Therefore, India’s climate has characteristics of tropical as well as subtropical climates. 02-03-2015 R. Ezhilraman, PGT-Social Science 12
  13. 13. Tropical, Temperate and Polar Zones • The tropical zone is between 23.5o north (the tropic of Cancer) and 23.5o south (the tropic of Capricorn) of the Equator. The Sun’s rays are most intense and the temperatures are always warm. • The temperate zones are between 23.5o and 66.5o north and between 23.5o and 66.5o south of the Equator. The Sun’s rays strike Earth at a smaller angle than near the Equator. • Polar zones are between 66.5o north and south latitudes and the poles. The sun’s rays strike Earth at a very small angle in the polar zones. 02-03-2015 R. Ezhilraman, PGT-Social Science 13
  14. 14. Highland Climates 02-03-2015 R. Ezhilraman, PGT-Social Science 14 In general, highland climates are cooler and wetter than nearby areas at lower elevations.
  15. 15. Earth’s Major Climate Zones 02-03-2015 R. Ezhilraman, PGT-Social Science 15
  16. 16. North Frigid Zone Temperate Zone Temperate Zone South Frigid Zone Torrid Zone 02-03-2015 R. Ezhilraman, PGT-Social Science 16
  17. 17. AGRA 160C in Jan DARJILING 40C in January ALTITUDE HIGH ALTITUDE LOW ALTITUDE Temperature decreased from low to high altitude 02-03-2015 R. Ezhilraman, PGT-Social Science 17
  18. 18. Air Temperature decreases with altitude. As elevation increases, the air gets cooler because of the energy drawn from the surroundings. 02-03-2015 R. Ezhilraman, PGT-Social Science 18
  19. 19. Factors That Affect Climate  Water Bodies Large bodies of water such as lakes and oceans have an important effect on the temperature of an area because the temperature of the water body influences the temperature of the air above it.  Atmospheric Circulation Global winds are another factor that influences climate because they distribute heat and moisture around Earth. 02-03-2015 R. Ezhilraman, PGT-Social Science 19
  20. 20.  Solar Activity When the Sun is most active, it contains dark blemishes called sunspots. The formation of sunspots appears to correspond with warm periods in Europe and North America.  Earth Motions Geographic changes in Earth’s land and water bodies cause changes in climate. Changes in the shape of Earth’s orbit and the tilt of Earth on its axis are other Earth motions that affect global climates. Natural Processes That Change Climates 02-03-2015 R. Ezhilraman, PGT-Social Science 20
  21. 21. Human Impact on Climate Changes  The Greenhouse Effect The greenhouse effect is a natural warming of both Earth’s lower atmosphere and Earth’s surface from solar radiation being absorbed and emitted by the atmosphere.  Global Warming As a result of increased levels of carbon dioxide and other greenhouse gases, global temperatures have increased. This increase is called global warming. 02-03-2015 R. Ezhilraman, PGT-Social Science 21
  22. 22. The Pressure and Surface Winds The pressure and wind system of any area depend on the latitude and altitude of the place. It influences the temperature and rainfall pattern. The climate and weather conditions in India are governed by the atmospheric conditions like: • Pressure and surface winds; • Upper air circulation; and • Western cyclonic disturbances and tropical cyclones. India lies in the north easterly winds region. These winds originate from the subtropical high-pressure belt of the northern hemisphere. They blow south, get deflected to the right due to the Coriolis force and move towards equatorial low-pressure area. 02-03-2015 R. Ezhilraman, PGT-Social Science 22
  23. 23. NORTH-EAST TRADE WIND SOUTH-EAST TRADE WIND INTER TROPICAL CONVERGENCE ZONE SUB TROPICAL HIGH PRESSURE SUB TROPICAL HIGH PRESSURE SUB TROPICAL LOW PRESSURE SUB TROPICAL LOW PRESSURE POLAR HIGH POLAR HIGH SURFACE WIND 02-03-2015 R. Ezhilraman, PGT-Social Science 23
  24. 24. AIR MASSES CIRCULATE GLOBALLY 02-03-2015 R. Ezhilraman, PGT-Social Science 24 • At the Equator, temperatures are relatively high. Land and water masses heat up and as a result these warm the air over them. • Air heated at the equatorial region rises to the top of the atmosphere. • More air rising beneath it forces the air mass to spread north and south toward the poles.
  25. 25. Coriolis Effect • The rotation of the Earth causes all moving objects in the Northern Hemisphere, including air mass, to deflect to the right and those in the Southern Hemisphere to move to the left. • This Coriolis effect is absent at the Equator. • Coriolis Force- prevents a direct simple flow from the Equator to the Poles. • This is also known as ‘Ferrel’s Law’. 02-03-2015 R. Ezhilraman, PGT-Social Science 25
  26. 26. 02-03-2015 R. Ezhilraman, PGT-Social Science 26
  27. 27. The Pressure and Surface Winds in India The pressure and wind conditions in India is unique. During winter, there is a high-pressure in the north of the Himalayas. Cold dry winds blow from this region to the low-pressure areas over the oceans to the south. In summer, a low-pressure area develops over interior Asia and in north-western India. This causes a complete reversal of the direction of winds during summer. Air moves from the high-pressure area over the southern Indian Ocean, in a south- easterly direction, crosses the equator, and turns right towards the low-pressure areas over the Indian subcontinent. These are known as the Southwest Monsoon winds. These winds blow over the warm oceans, gather moisture and bring widespread rainfall over the mainland of India. 02-03-2015 R. Ezhilraman, PGT-Social Science 27
  28. 28. ARABIAN SEA BAY OF BENGAL INDIAN OCEAN LOW AND HIGH PRESSURE HIGH PRESSURE IN WINTER 02-03-2015 R. Ezhilraman, PGT-Social Science 28
  29. 29. MUMBAI CHENNAI KOLKOTA DELHI SIMLA DISTANCE FROM SEA Coastal areas have equable climate where as Interior parts have extreme climate. 02-03-2015 R. Ezhilraman, PGT-Social Science 29
  30. 30. Relief • Relief too 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 if they are high enough and lie in the path of rain-bearing winds. The leeward side of mountains remains relatively dry. 02-03-2015 R. Ezhilraman, PGT-Social Science 30
  31. 31. Receives high rainfall Receives low rainfall RELIEF 02-03-2015 R. Ezhilraman, PGT-Social Science 31
  32. 32. RELIEF The Rain Shadow Effect 02-03-2015 R. Ezhilraman, PGT-Social Science 32
  33. 33. 02-03-2015 R. Ezhilraman, PGT-Social Science 33
  34. 34. Jet Stream • The upper air circulation in India is dominated by a westerly flow, known as the jet stream. • These are a narrow belt of high altitude (above 12,000 m) westerly winds in the troposphere. Their speed varies from about 110 km/h in summer to about 184 km/h in winter. • Many jet streams have been identified. The most constant are the mid-latitude and the sub tropical jet stream. 02-03-2015 R. Ezhilraman, PGT-Social Science 34
  35. 35. TIBET JET STREAM IN WINTER 02-03-2015 R. Ezhilraman, PGT-Social Science 35
  36. 36. Jet Stream Jet streams are located at 27°-30° north latitude, are known as subtropical westerly jet streams. Over India, these jet streams blow south of the Himalayas, all through the year except in summer. The western cyclonic disturbances experienced in the north and north-western parts of the country are brought in by this westerly flow. In summer, the subtropical westerly jet stream moves north of the Himalayas with the apparent movement of the Sun. An easterly jet stream, called the tropical easterly jet stream blows over peninsular India, approximately over 14°N during the summer. 02-03-2015 R. Ezhilraman, PGT-Social Science 36
  37. 37. JET STREAM IN SUMMER 02-03-2015 R. Ezhilraman, PGT-Social Science 37
  38. 38. Western Disturbances • The western cyclonic disturbances are weather phenomena of the winter months brought in by the westerly flow from the Mediterranean region. They usually influence the weather of the north and north- western regions of India. Tropical cyclones occur during the monsoon as well as in October - November, and are part of the easterly flow. These disturbances affect the coastal regions of the country. • Thus very often the coast of Orissa and Andhra Pradesh are affected by those disasters. 02-03-2015 R. Ezhilraman, PGT-Social Science 38
  39. 39. WESTERN DISTURBANCE 02-03-2015 R. Ezhilraman, PGT-Social Science 39
  40. 40. OCEAN CURRENTS Solar energy, wind, and Earth’s rotation creates Ocean currents Current- the systematic patters of water movement. Gyres- two great circular water motion.  Northern Hemisphere- the ocean current moves clockwise.  Southern Hemisphere- the ocean current move anti-clockwise.  Trade winds push warm surface waters westward at the equator.  As the waters encounter the continents, they split into north- and south-flowing currents along the eastern coast, forming north and south gyres. 02-03-2015 R. Ezhilraman, PGT-Social Science 40
  41. 41. Surface Water blown by the winds at point A will weirs to the right of its initial path and continue eastward. Water at point B weirs to the right and continues westward. 02-03-2015 R. Ezhilraman, PGT-Social Science 41
  42. 42. 02-03-2015 R. Ezhilraman, PGT-Social Science 42
  43. 43. 02-03-2015 R. Ezhilraman, PGT-Social Science 43
  44. 44. Winds driven by uneven solar heating and Earth’s spin, drive the movement of the ocean’s surface currents. The prime movers are the powerful westerlies and the persistent trade winds (easterlies) 02-03-2015 R. Ezhilraman, PGT-Social Science 44
  45. 45.  The Köppen climate classification system uses mean monthly and annual values of temperature and precipitation to classify climates.  According to the Köppen classification, the earth can be divided into several major climatic zones and bands: The Köppen Climate Classification System  Tropical climate  Subtropical climate  Arid climate  Equatorial climate  Semiarid climate  Mediterranean climate  Temperate climate  Oceanic climate  Continental climate  Subarctic climate  Polar climate  Climate of Antarctica 02-03-2015 R. Ezhilraman, PGT-Social Science 45
  46. 46. Tropical Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 46
  47. 47. Subtropical Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 47
  48. 48. Arid Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 48
  49. 49. Equatorial Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 49
  50. 50. Semiarid Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 50
  51. 51. Mediterranean Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 51
  52. 52. Temperate Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 52
  53. 53. Oceanic Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 53
  54. 54. Continental Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 54
  55. 55. Subarctic Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 55
  56. 56. Polar Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 56
  57. 57. Polar Climate 02-03-2015 R. Ezhilraman, PGT-Social Science 57 Polar climates are those in which the mean temperature of the warmest month is below 10o C.
  58. 58. Climate of Antarctica 02-03-2015 R. Ezhilraman, PGT-Social Science 58
  59. 59. The Indian Monsoon The climate of India is strongly influenced by monsoon winds. The sailors who came to India in historic times were one of the first to have noticed the phenomenon of the monsoon. They benefited from the reversal of the wind system as they came by sailing ships at the mercy of winds. The Arabs, who had also come to India as traders named this seasonal reversal of the wind system ‘monsoon’. 02-03-2015 R. Ezhilraman, PGT-Social Science 59
  60. 60. Atmospheric Conditions over the Indian Subcontinent in the Month of January 02-03-2015 R. Ezhilraman, PGT-Social Science 60
  61. 61. Atmospheric Conditions over the Indian Subcontinent in the Month of June 02-03-2015 R. Ezhilraman, PGT-Social Science 61
  62. 62. Facts of Mechanism of the Monsoons 02-03-2015 R. Ezhilraman, PGT-Social Science 62 In India, the monsoons are experienced in the tropical area roughly between 20°N and 20°S. The Following facts are the Mechanism of the Monsoons. (a) The differential heating and cooling of land and water creates low pressure on the landmass of India while the seas around experience 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 5°N of the equator. It is also known as the monsoon-trough during the monsoon season).
  63. 63. Inter Tropical Convergence Zone (ITCZ) 02-03-2015 R. Ezhilraman, PGT-Social Science 63 The Inter Tropical Convergence Zone (ITCZ) is a broad trough of low pressure in equatorial latitudes. This is where the northeast and the southeast trade winds converge. This convergence zone lies more or less parallel to the equator but moves north or south with the apparent movement of the sun.
  64. 64. Facts of Mechanism of the Monsoons 02-03-2015 R. Ezhilraman, PGT-Social Science 64 (c) The presence of the high-pressure area, east of Madagascar, nearly at 20°S over the Indian Ocean. The intensity of this high-pressure area affects the Indian Monsoon. (d) The Tibetan plateau gets intensely heated during summer, results in strong vertical air currents and the formation of low pressure over the plateau at about 9 km above sea level. (e) The movement 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.
  65. 65. Southern Oscillation 02-03-2015 R. Ezhilraman, PGT-Social Science 65 The changes in the pressure conditions over the southern oceans also affect the monsoons. When the tropical eastern south Pacific Ocean experiences high pressure, the tropical eastern Indian Ocean experiences low pressure. But sometimes, 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 conditions is known as the Southern Oscillation or SO. The difference in pressure over Tahiti in Pacific Ocean and Darwin in northern Australia of Indian Ocean is predicted the intensity of the monsoons. If the pressure differences were negative, it would mean below average and late monsoons. A feature connected with the SO is the El Nino, a warm ocean current that 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 (El Nino Southern Oscillations).
  66. 66. Darwin Tahiti SOUTHERN OSCILLATION 02-03-2015 R. Ezhilraman, PGT-Social Science 66
  67. 67. Effect of El Niño 02-03-2015 R. Ezhilraman, PGT-Social Science 67 El Nino is a name given to the periodic development of a warm ocean current along the coast of Peru as a temporary replacement of the cold Peruvian current. ‘El Nino’ is a Spanish word meaning ‘the child’, and refers to the baby Christ, as this current starts flowing during Christmas. The presence of the El Nino leads to an increase in sea- surface temperatures and weakening of the trade winds in the region.
  68. 68. Homboldt Cold Current EL-NINO EFFECTS 1990 Delay in Monsoon Equatorial Warm Current El-Nino 02-03-2015 R. Ezhilraman, PGT-Social Science 68
  69. 69. Beginning of the Monsoon 02-03-2015 R. Ezhilraman, PGT-Social Science 69 The duration of the monsoon is between 100-120 days from early June to mid-September. During its arrival, the normal rainfall increases suddenly and continues constantly for several days. This is known as the ‘burst’ of the monsoon, and can be distinguished from the pre-monsoon showers. The monsoon arrives at the southern tip of the Indian peninsula generally by the first week of June. Subsequently, it proceeds into two – (i) the Arabian Sea branch and (ii) the Bay of Bengal branch.
  70. 70. Beginning of the Monsoon 02-03-2015 R. Ezhilraman, PGT-Social Science 70 The Arabian Sea branch reaches Mumbai about ten days later on approximately the 10th of June. This is a fairly rapid advance. The Bay of Bengal branch also advances rapidly and arrives in Assam in the first week of June. The lofty mountains causes the monsoon winds to deflect towards the west over the Ganga plains. By mid-June the Arabian Sea branch of the monsoon arrives over Saurashtra-Kuchchh and the central part of the country. The Arabian Sea and the Bay of Bengal branches of the monsoon merge over the north-western part of the Ganga plains. Delhi generally receives the monsoon showers from the Bay of Bengal branch by the end of June (tentative date is 29th of June). By the July first week, western Uttar Pradesh, Punjab, Haryana and eastern Rajasthan experience the monsoon. By mid-July, the monsoon reaches Himachal Pradesh and the rest of the country.
  71. 71. 02-03-2015 R. Ezhilraman, PGT-Social Science 71
  72. 72. End of the Monsoon 02-03-2015 R. Ezhilraman, PGT-Social Science 72 Withdrawal or the retreat of the monsoon is a more gradual process. The withdrawal of the monsoon begins in north-western states of India by early September. By mid-October, it withdraws completely from the northern half of the peninsula. Then it quickly withdraw from the southern half of the peninsula. By early December, the monsoon has totally withdrawn from the country. The islands receive the very first monsoon showers, from south to north, between the last week of April and the first week of May. Then it withdraw from north to south during the first week of December to the first week of January. By this time, the other parts of the country is already influencing the winter monsoon.
  73. 73. 02-03-2015 R. Ezhilraman, PGT-Social Science 73
  74. 74. RHYTHM OF SEASONS COLD WEATHER RETREATING MONSOONHOT WEATHER SOUTH WEST MONSOON Let us discuss each of them individually 02-03-2015R. Ezhilraman, PGT-Social Science 75
  75. 75. 02-03-2015 R. Ezhilraman, PGT-Social Science 76 The monsoon type of climate is characterised by a distinct seasonal pattern. The weather conditions greatly change from one season to the other. These changes are particularly noticeable in the interior parts of the country. But, the coastal areas do not experience much variation in temperature though there is variation in rainfall pattern. In India, Four main seasons can be identified: (i) the cold weather season, (ii) the hot weather season, (iii)the advancing monsoon and (iv) the retreating monsoon with some regional variations.
  76. 76. COLD WEATHER SEASON ►It extends from December to February. ►Vertical sun rays shift towards southern hemisphere. ►North India experiences intense cold where as this season is not well defined in south India. ►Light wind blow makes this season pleasant in south India. ►Occasional tropical cyclone visit eastern coast in this season. Tropical Cyclone 02-03-2015R. Ezhilraman, PGT-Social Science 77
  77. 77. 02-03-2015 R. Ezhilraman, PGT-Social Science 78 The cold weather season begins from mid- November in northern India and stays till February. December and January are the coldest months. The temperature decreases from south to the north. The average temperature of Chennai, on the eastern coast is between 24°-25° Celsius, while in the northern plains, it ranges between 10°-15° Celsius. Days are warm and nights are cold. Frost is common in the north and the higher slopes of the Himalayas experience snowfall. During winter, the northeast trade winds blow from land to sea. So, most part of the country faces a dry season. Some amount of rainfall occurs on the Tamil Nadu coast from these winds as, trade winds blow from sea to land. In the northern part of the country, a feeble high-pressure region develops, with light winds moving outwards from this area. Influenced by the relief, these winds blow through the Ganga valley from the west and the northwest. The weather is normally marked by clear sky, low temperatures and low humidity and feeble, variable winds.
  78. 78. 250 C 250 C 200 C 200 C 200 C 150 C 200 C 100 C` TEMPERATURE- JANUARY 02-03-2015R. Ezhilraman, PGT-Social Science 79
  79. 79. PRESSURE- JANUARY 101 4 HIGH PRESSURE 02-03-2015R. Ezhilraman, PGT-Social Science 80
  80. 80. 02-03-2015 R. Ezhilraman, PGT-Social Science 81 In the northern plains, there is the inflow of cyclonic disturbances from the west and the northwest. These low- pressure systems, from the Mediterranean Sea and western Asia and move into India, along with the westerly flow. They cause the winter rains (locally known as ‘mahawat’) over the plains and snowfall in the mountains. Although the amount of rainfall is small, it is more importance for cultivating the ‘rabi’ crops. But, the peninsular region does not have a well-defined cold season. There is rare seasonal change in temperature pattern during winters due to the moderating influence of the sea.
  81. 81. WIND DIRECTION- WINTER Bay of Bengal 02-03-2015R. Ezhilraman, PGT-Social Science 82
  82. 82. WINTER RAINFALL RAINFALL DUE TO WESTERN DISTURBANCES RAINFALL DUE TO NORTH EAST WIND 02-03-2015R. Ezhilraman, PGT-Social Science 83
  83. 83.  Winter is cold.  Children dress warmly to play in the snow.  Animals head to their winter homes. 02-03-2015R. Ezhilraman, PGT-Social Science 84
  84. 84. HOT WEATHER SEASON ► It extends from March to May. ► Vertical sun rays shift towards Northern hemisphere. ► Temperature rises gradually from south to north. ► Highest Temperature experiences in Karnataka in March, Madhya Pradesh in April and Rajasthan in May. March 300C April 380C May 480C 02-03-2015R. Ezhilraman, PGT-Social Science 85
  85. 85. 02-03-2015 R. Ezhilraman, PGT-Social Science 86 Due to the apparent northward movement of the Sun, the global heat belt shifts northward. So, from March to May, it is hot weather season in India. In March, the highest temperature is about 38°C, in Deccan plateau. In April, temperatures in Gujarat and Madhya Pradesh are around 42°C. In May, 45°C temperature is common in the north-western parts of the country. In peninsular India, temperatures remain lower due to the moderating influence of the oceans. The summer months experience rising temperature and falling air pressure in the northern part of the country. By the end of May, an elongated low-pressure area develops in the region extending from the Thar Desert in the northwest to Patna and Chotanagpur plateau in the east and southeast. Circulation of air begins to set in around this trough.
  86. 86. TEMPERATURE- JULY 250 C 300 C 02-03-2015R. Ezhilraman, PGT-Social Science 87
  87. 87. PRESSURE- JULY 02-03-2015R. Ezhilraman, PGT-Social Science 88
  88. 88. LOO KALBAISAKHI BARDOLI CHHEERHA MANGO SHOWER BLOSSOM SHOWER STORMS IN HOT WEATHER SEASON 02-03-2015R. Ezhilraman, PGT-Social Science 89
  89. 89. 02-03-2015 R. Ezhilraman, PGT-Social Science 90 An important feature of the summer season is the ‘loo’. These are strong, gusty, hot, dry winds blowing during the day, sometimes till late evening over the north and North-western India. Direct exposure to these winds may be harmful. Dust storms are very common during May in northern India. These storms bring temporary relief as they lower the temperature and may bring light rain and cool breeze. This is also the season for localised thunderstorms, associated with violent winds. In West Bengal, these storms are known as the ‘Kaal Baisakhi’. By close of the summer season, pre-monsoon showers are common especially, in Kerala and Karnataka. They help in the early ripening of mangoes, and are often referred to as ‘mango showers’.
  90. 90.  Long, hot days.  Summer fruit and vegetables are ready to be picked.  You see many bees and butterflies fly flower to flower. 02-03-2015R. Ezhilraman, PGT-Social Science 91
  91. 91. Advancing Monsoon (The Rainy Season) SOUTH WEST MONSOON SEASON ► It extends from June to September. ► Intense heating in north west India creates low pressure region. ► Low pressure attract the wind from the surrounding region. ► After having rains for a few days sometime monsoon fails to occur for one or more weeks is known as break in the monsoon. HIGH TEMPERATURELOW PRESSURE 02-03-2015R. Ezhilraman, PGT-Social Science 92
  92. 92. INTER TROPICAL CONVERGENCE ZONEEQUATOR MONSOON WIND Arabian sea Branch Bay of Bengal Branch 02-03-2015R. Ezhilraman, PGT-Social Science 93
  93. 93. ONSET OF SW MONSOON 02-03-2015R. Ezhilraman, PGT-Social Science 94
  94. 94. 02-03-2015R. Ezhilraman, PGT-Social Science 95 By early June, the low-pressure condition over the northern plains attracts the trade winds of the southern hemisphere. These south- east trade winds originate over the warm subtropical areas of the southern oceans. These winds are strong and blow at an average velocity of 30 kmph. With the exception of the extreme north-west, the monsoon winds cover the country in about a month. The south-west monsoon entirely changes the weather in India. The Western Ghats receives heavy rainfall, more than 250 cm. The rain shadow areas like Deccan Plateau and parts of Madhya Pradesh also receives rain. The north-eastern part of the country receives the maximum rainfall. Mawsynram in the southern ranges of the Khasi Hills receives the highest average rainfall in the world. Rainfall in the Ganga valley decreases from the east to the west. Rajasthan and parts of Gujarat get scanty rainfall.
  95. 95. 02-03-2015R. Ezhilraman, PGT-Social Science 96 The monsoon rains take place only for a few days at a time. They are interspersed with rainless intervals. These breaks in monsoon are related to the movement of the monsoon trough. The trough and its axis keep on moving northward or southward, which determines the spatial distribution of rainfall. Whenever the axis shifts closer to the Himalayas, widespread rain occur in the mountainous catchment areas of the Himalayan rivers, which also cause floods. The frequency and intensity of tropical depressions determine the amount and duration of monsoon rains. These depressions form at the Bay of Bengal and cross over to the mainland. The depressions follow the axis of the “monsoon trough of low pressure”. It causes heavy floods in one part, and droughts in the other. Sometimes it disturbs the farming schedule of millions of farmers all over the country.
  96. 96. ►It extends from October to November ►Vertical sun rays start shifting towards Northern hemisphere. ►Low pressure region shift from northern parts of India towards south. ►Owing to the conditions of high temperature and humidity, the weather becomes rather oppressive. This is commonly known as the ‘October heat’ RETREATING MONSOON SEASON LOW PRESSURE 02-03-2015R. Ezhilraman, PGT-Social Science 97
  97. 97. WITHDRAWAL OF MONSOON 02-03-2015R. Ezhilraman, PGT-Social Science 98
  98. 98. 02-03-2015R. Ezhilraman, PGT-Social Science 99 Parts of western coast and north-eastern India receive over about 400 cm of rainfall annually. But, in western Rajasthan and adjoining parts of Gujarat, Haryana and Punjab it is less than 60 cm. Rainfall is equally low in the interior of the Deccan plateau, and east of the Sahyadris. Because of low precipitation found around Leh in Jammu and Kashmir. The rest of the country receives moderate rainfall. Snowfall is restricted to the Himalayan region. Based on the nature of monsoons, the annual rainfall is highly variable from year to year. Variability is high in the regions of low rainfall such as parts of Rajasthan, Gujarat and the leeward side of the Western Ghats. Similarly, the areas of high rainfall are often affected by floods, areas of low rainfall are drought-prone.
  99. 99. DISTRIBUTION OF RAINFALL > 200cm 100-200cm 50-100 cm < 50cm 02-03-2015R. Ezhilraman, PGT-Social Science 100
  100. 100.  The sun shines more and the days begin to get warmer.  Spring is a time when baby animals are born.  Spring is a time when plants and trees wake up after a long winters nap.  Spring showers help to warm the earth, moisten the soil, helping new plants to grow. 02-03-2015R. Ezhilraman, PGT-Social Science 101
  101. 101.  Leaves change to yellow, orange, and red.  Picking fruit and vegetables.  Animals get ready for winter. 02-03-2015R. Ezhilraman, PGT-Social Science 102
  102. 102. 02-03-2015R. Ezhilraman, PGT-Social Science 103 The Himalayas protect the subcontinent from extremely cold winds from central Asia. This enables northern India to have uniformly higher temperatures when compared to other areas on the same latitudes. Similarly, the peninsular plateau, under the influence of the sea from three sides, has moderate temperatures. The unifying influence of the monsoon on the Indian subcontinent is quite perceptible. The seasonal alteration of the wind systems and the associated weather conditions provide a rhythmic cycle of seasons. The Indian landscape, its animal and plant life, its entire agricultural calendar and the life of the people, including their festivities, revolve around this phenomenon.
  103. 103. 02-03-2015R. Ezhilraman, PGT-Social Science 104

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