CLIMATE, FLORA and FAUNA Note: the Study Material Consists of 3 Parts
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Assignment 8 Class VIII Geography Chapter 9 INDIA : CLIMATE, FLORA AND FAUNA Note: The Study Material consists of 3 parts - ○ Part I - The important highlights of the chapter. ○ Part II - The activity based on the chapter. ○ Part III - The questions based on the study material that you need to answer in your respective notebook and submit when you are back to the school. PART I HIGHLIGHTS OF THE LESSON INTRODUCTION - CLIMATE OF INDIA The climate of a country is based on the detailed study of its temperature, rainfall, atmospheric pressure and direction of the winds. The climate of India is greatly influenced by two factors : (a) The Tropic of Cancer (232°N) – It divides India into two halves - north temperate zone and the south tropical zone. (b) The Great Himalayan range from northwest to northeast direction - It separates India from the rest of Asia, thus preventing the country from the bitter cold winds from Central Asia. The vast north-south extent of India 8°N to 37°N covers a distance of about 3214 km from north to south. While one can observe the unique climatic contrasts from north to south. One factor which unifies the climate of India is the fact of monsoon with alternation of seasons and reversal of winds. Therefore, the climate of India is called Tropical Monsoons. 2. FACTORS AFFECTING CLIMATE OF INDIA India experiences great variation in temperature and rainfall due to various factors affecting its climate. They are: (a) Latitude and topography (b) Influence of the Himalayas (c) Altitude (d) Distance from the sea (e) Western disturbances and tropical cyclones (1) Upper air currents and jet streams (a) Latitude and topography: The Tropic of Cancer divides India into temperate or subtropical north and tropical south. Thus, northern India experiences continental or extreme types of climate whereas the southern part experiences tropical climate. The southern peninsula experiences moderate climate as it is enclosed on three sides by the Arabian Sea, the Indian Ocean and the Bay of Bengal. Coastal regions experience marine or equable climate. (b) Influence of Himalayas: The great Himalayan ranges obstruct the bitter cold winds from Siberia from entering the Indian subcontinent. The Himalayas intercept the moisture laden South west monsoon winds forcing them to shed their moisture, resulting in heavy rainfall in the northeast and Indo-Gangetic plains. (c) Altitude: Temperature decreases with increasing altitude at the rate of 1°C for every 166m. Hence, places situated at the higher altitude are cooler as compared to places in the plains, c.g., Nainital is cooler as compared to Agra. (d)Distance from the sea: The places situated in the interior experience extreme or continental type of climate, whereas places situated at the coast experience marine or equable type of climate, e.g., Mumbai situated at the coast experiences equable climate, whereas Lucknow experiences extreme type of climate. (e) Western disturbances and tropical cyclones: Western disturbances or temperate cyclones originate in Mediterranean Sea during winter and bring rainfall in Northwest India and snowfall in the Himalayas. During summer the whole of eastern coast of India comes under the influence of tropical cyclones. They cause heavy loss to life and property (f)The upper air currents or jet streams: The Upper air CURRents or jet streams affect the onset and departure of the monsoon. 3. THE CLIMATIC CONTRASTS Due to its vast north-south extent. India experiences sharp climatic contrasts. ● The places to the north of the Tropic of Cancer experience continental type of climate, i.e. very hot during summer and very cold during winter, e.g., temperature rises upto 55°C. in Rajasthan while in Dras near Kargil, the temperature may go down to 40°C. ● The places along the eastern and western coast experience equable or marine type of climate, e.g., Mumbai and Chennai. Here the range of temperature is very low being near to the Equator. ● The annual rainfall varies from 1187 cm at Mawsynram (highest in Asia) in the state of Meghalaya to 25 cm in Rajasthan. ● Himalayas experience heavy snowfall during winter, while in the south, even in winter the places at high altitude do not receive any snowfall, being nearer to the Equator. 4. CHANGE OF SEASONS IN INDIA India's tapering peninsular topography, surrounded on three sides by water, plays an important role in determining the course of monsoon winds and resulting in unique climate of India consisting of four seasons: 1. Monsoons : The word monsoon owes its origin to an Arabic word Mausim meaning season. These winds reverse their directions seasonally. They blow from southwest to northeast for six months and from northeast to southwest for another six months. Hence, they are called southwest monsoon and northeast monsoon. 2. On the basis of monsoon variations the year may be divided into four main seasons: (a) The hot dry season (March to May). (b) The rainy season or the season of southwest monsoon (June to September). (c) The season of the retreating southwest monsoon (October and November). (d) season or the season of the last monsoon (December to February). (a) The hot dry season (March to May) This season is characterised by dry weather and excessive heat practically all over the country. Temperature conditions over the land ● During the summer solstice the sun shines directly overhead at the Tropic of Cancer. ● The mainland of India experiences intense heat during the months of March to May. As a result low pressure conditions develop over the land while high pressure prevails over the surrounding seas. ● There is a steady increase in temperature from south to north with the highest in the interior. Rajasthan experiences the highest temperature between 45° to 55°C. In central India, the temperature is above 32°C over most of the interior, whereas in the coastal areas the average temperature remains 26°C and above. Pressure conditions ● The warmest areas shift from Deccan to Northwest India during May, where a low pressure trough develops between the Thar desert and the Chota Nagpur plateau. ● Since the surrounding areas are cooler and have high pressure, the prevailing southeast trade winds are attracted towards the low pressure area and blow from southwest to northeast, known as southwest monsoon. Here hot season ends and southwest monsoon sets in the month of June. Storms during hot season ● During May, the winds surrounding the low trough area are drawn into circulation. ● These local winds give rise to thunderstorms with REMINStrong dusty winds often causing a Mshower of rain in Punjab, Haryana and Uttar Pradesh. Local winds during hot season ● Kali Baisakhi : In West Bengal or Assam the local winds are called Kali Baisakhi (calamity of Baisakh month). ● Loo are hot dusty winds and are also called sandstorms which blow between the months of May and June in the northern plains. ● Mango showers: These occur in South India during April/May. They bring a little rain which is important for mango, tea, coffee crops. Hence, they are called mango showers. Characteristic features of hot season ● This season is marked by dry weather and excessive heat. ● In this season the sun shines directly overhead at the Tropic of Cancer. ● The range of temperature is very high. ● The brief spell of showers experienced in this season is very useful for tea crop in Assam, rice in West Bengal and mango, tea and coffee in the south. (b) The rainy season of the southwest monsoon (from June to September) Onset of the monsoon over the Malabar coast in Kerala is a spectacular event. There is a miraculous change in the general scenario of the country. The landscape seems suddenly transformed with lush green fields and overflowing rivers. ● Origin of Monsoon: Monsoons are basically land and sea breezes on a large scale. During hot season, because of the excessive heat, a low pressure develops over the landmass of India while the surrounding water bodies remain relatively cool and a high pressure develops over the seas. ● The intense low pressure over the land attracts the trade winds blowing in the Southern Hemisphere. These winds, after crossing the equator, are deflected towards right in the Northern Hemisphere and blow towards the mainland of India from southwest to northeast. These are called southwest monsoon. ● The southwest monsoon divides into two branches due to tapering topography of peninsular India. (i) The Arabian Sea branch (ii) The Bay of Bengal branch The Arabian Sea branch : The Arabian Sea branch of southwest monsoon generally strikes the Western Coast of India in Kerala on 1st June. It gives very heavy rainfall along the windward side of Western Ghats as these winds are unable to cross over the Western Ghats. ● This rainfall is called orographic or relief rainfall. ● The Deccan plateau lying in the rain shadow of the Western Ghats receives very little rainfall, e.g., Mumbai situated on the western side of the Western Ghats receives heavy rainfall (more than 200 cm) whereas Pune only a little distance away, receives little rainfall. ● The duration and amount of rainfall goes on decreasing as the Arabian Sea branch moves northward. The Arabian Sea branch gives little rainfall to Rajasthan due to the following reasons: ● The southwest monsoon winds run parallel to the Aravalis. They do not give rainfall in Rajasthan as they do not get any obstruction from the Aravalis. ● The moisture laden winds passing over Rajasthan do not give much rainfall because the heat in the desert increases their capacity to hold moisture. Hence, they do not shed any moisture in Rajasthan. ● The Arabian Sea branch gets exhausted by the time it sheds its remaining Punjab and moisture there. (ii) The Bay of Bengal branch: The Bay of Bengal branch of southwest monsoon advances towards northeast after picking moisture from the Bay of Bengal.