Chapter 4: Climate - PDF

# CHAPTER - 4 [CLIMATE] ## What is climate? Climate refers to the sum total of weather conditions and variations over a large area for a long period of time (more than thirty years). ## What is weather? Weather is the state of atmosphere over an area at any point of time. ## What do you mean by...

# CHAPTER - 4 [CLIMATE] ## What is climate? Climate refers to the sum total of weather conditions and variations over a large area for a long period of time (more than thirty years). ## What is weather? Weather is the state of atmosphere over an area at any point of time. ## What do you mean by the term 'monsoon'? The term 'monsoon' refers to the seasonal reversal in the wind direction during a year. It is derived from the Arabic word 'mausim' which literally means season. ## What are the elements of weather and climate? - Temprature - Atmospheric pressure - Wind - Humidity - Precipitation ## Name the climatic controls. - Latitude - Altitude - Pressure and winds - Distance from the sea. - Relief - Ocean currents. ## What are monsoons? Monsoon refers to the seasonal reversal of winds direction during a year. ## Explain the cold weather season. The cold weather season begins from mid November in nathern India and stays till February. - December and January are the coldest months in the northern part of India. - The temprature decreases from south to the north. - The average temperature of Chennai on the east. - Days are warm and nights are cold. - Frost is common in the north. - The higher slopes of the Himalayas experience snowfall. - The northeast trade winds prevail over the country. - They blow from land to sea, and hence, for most part of the country, it is a dry season. - Some amount of rainfall occurs on the Tamil Nadu coast from these winds as, here they 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. - The weather is normally marked by clear sky, low temperatures and low humidity and feeble, variable winds. ## Explain the characteristics of advancing monsoon. Southeast trade winds originate over the warm sub-tropical areas of the southern ocean. - This season ranges from June to September. - The southwest monsoon brings rainfall in the entire country except northwest. - This season experiences breaks in monsoon and hence has wet and dry spells. - There are tropical depressions. - It has irregular, erratic monsoon. ## Explain the characteristics of retreating/ post monsoons. This season ranges from October to November. - Here, the temprature is warm. - The pressure is initially low and gradually becomes high. - The days are hot, nights are cool and the air is moist - This season experiences October heat which is caused due to high temprature and humidity. ## Explain the distribution of rainfall in India. Altitude and the distance from the sea affects the distribution of rainfall. Areas with high rainfall cause floods and areas with low rainfall lead to drought. - Parts of western coast and northeast India receive over 400 cm of rainfall annually. - It is less than 60 cm in western Rajasthan and Punjab adjoining parts of Gujrat, Haryana and Punjab. - Rainfall is equally low in the interior of the Deccan plateau, and east of the Sahyadris. - Leh also has low rainfall. - The rest of the country receives moderate rainfall. - Snowfall is restricted to the Himalayan region. ## Why does India have a monsoon type of climate? India has a monsoon type of climate. Strong influence of the monsoon winds over the subcontinent. The summer monsoon cause heavy rainfall when the blow from sea to land. The winter monsoon winds blow from the interior of the continent to the sea and do not cause much rain. There is a seasonal reversal of wind called a monsoon ## Which part of India does experience the highest diurnal range of temperature and why? The Thar desert experiences the highest diurnal range of temprature. This is because during the day, the temprature rises to over 50°c and at night, due to the absence of Sun and lack of vegetation, the temprature drops to below 15°c. cet ## What do you understand by break in monsoon? The break in the monsoon refers to the dry spells. When the monsoon takes place only for a few days at a time. These breaks are related to the movement of the monsoon trough. When the axis of the monsoon trough lies over the plains, the rainfall is heavy. When the trough moves towards the Himalayas, the plains are dry but there is heavy rainfall on the mountains. ## Why is the monsoon considered 'a unifying bond'? The subcontinent of India has a great variation in temprature conditions, despite the moderating influence created by other factors. The monsoons have a 'unifying' influence as the rainfall that is caused affects the entire country. Water is thus supplied for agricultural activities as well as to the rivers for use all over the country. The monsoons thus, bind the entire country, where all wait eagerly for their arrival. ## Why does the rainfall decrease from the east to west in nothern India? The low pressure area in India lies in the northwest, towards which the southwest monsoon winds are attracted. After, shading moisture in south India, the bay of Bengal branch of the South West monsoon strike the khasi-Garo Hills. After causing heavy rainfall on the windward slopes, these winds turn into westwards because of the presence of the lofty Himalayas. These winds then keep shading rainfall as they go up the Ganga valley towards the low-pressure area. The rainfall shaded does thus keeps decreasing as the winds proceed from east to west in nothern India, as this is the last region to be affected by the monsoons ## Give reason as to why seasonal reversal of wind direction takes place over the Indian subcontinent? Land and water are of different densities, so the rate of heating and cooling varies. The Indian subcontinent is surrounded by water on three sides. In summer, the landmass of India is warmer than the surrounding sea. Therefore, there is a low pressure. The sea is cooler, thereby having, higher pressure. So the winds blow from sea to land. In winter the land has high pressure while the sea has low pressure. Therefore, the winds blow towards the sea. Thus, a seasonal reversal of wind direction takes place. ## The bulk of rainfall in India is concentrated over a few months. In India, the bulk of ther rainfall is concentrated over a few months. The main source of rainfall is the monsoon wind which blows when there is intense low pressure on the land and high pressure on the surrounding water body. This ideal temprature and pressure is caused in May, when the rain falls between June to September and it becomes cooler. (high pressure). Rest of the year is practically dry ## The Tamil Nadu coast recieves winter rainfall. During the winter season, the Tamil Nadu coast recieves rain from the northeast monsoon which blow from land to sea. They do not cause any rain in the nothern part of the cour country. But, while crossing the bay of Bengal, they pick up moisture and cause rain on the eastern coast of South India, mainly the Tamil Nady coast. ## The delta region. of eastern coast is frequently struck by cyclones. The delta region of eastern coast is frege frequently struck by cyclones as the low pressure conditions of northwestern India get transferred to the Bay of Bengal by early November. This shift is responsible for occurence of cyclonic depressions which originate over the Andaman sea, these then cross the eastern coast causing heavy rain widespread rain leading to great damage to life and property. ## Parts of Rajasthan, Gujarat and the leeward side of the western Chats are drought-prone. Relief / mountains play an important role in the distribution of rainfall in India. The moisture Laden winds (Southwest monsoon) causes heavy rain in the wind ward slopes of the Western ghats and Khasi - Garo Hills. As the winds cross over to the leeward slopes, there is less rainfall as most of it has been shaded on the slopes facing the winds. All the area on the leeward side is deprived of rain and is drought-prone. Rajasthan also lies on the rain shadow of the Aravalli Hills. ## Describe the regional variations in the Climatic conditions of India with the help of suitable example. There is a great regional variation in climatic conditions of India (mainly temperature and rainfall). In summers, Hie temprature rises above Soc in Some parts of Rajasthan - While in Jambu & Kashmir, it is in about 20°c. The temprature in Drass during winters goes down to even-minus-45°c, While in Thiruvanthpuram Thiruvananthapuram it is 22c. The precipitation varies from over 400cm in Meghalaya to less than 10cm in Ladakh and western Rajasthan while the precipitation in most of India is in the form of rain, The larger part of the country between June - September. Parts of Tamil Nadu recieves ## Differentiate between soothe northeast and southwest monsoon. | Northeast | Southwest | |---|---| | They blow in winter from November, to January Feb | They blow is Summer from June to september. | | They blow from land to sea. | They blow from high pressure (sea) to low pressure (land) | | These are dry as they originate from Land. | They are moisture laden. | | While crossing the Bay of Bengal they pick up masture and give rainfall to the Goramandel coast. | They blow in two Branches - Arabian sea and Bay of Bengal and provide 75% to 90% of rainfall. |