Climate Notes PDF

Climate - Notes Geography Copyright © 2014-2023 TestBook Edu Solutions Pvt. Ltd.: All rights reserved  Download Testbook App Unit Name - Clima...

Climate - Notes Geography Copyright © 2014-2023 TestBook Edu Solutions Pvt. Ltd.: All rights reserved  Download Testbook App Unit Name - Climate Chapters Covered Ch - Structure & Composition Of Atmosphere Ch - Insolation Temperature ATMOSPHERE The Atmosphere Definition and Importance: The atmosphere is the gaseous envelope surrounding the Earth, retained by the Earth's gravitational attraction. It sustains life on our planet by: Absorbing harmful ultraviolet and other high-energy radiations from the Sun Burning up meteorites and cosmic dust particles due to friction Regulating temperature by absorbing, reflecting, and radiating solar energy Supporting the water cycle and enabling weather phenomena Layers of the Atmosphere Troposphere: The troposphere is the lowest layer of the atmosphere, extending from the Earth's surface up to an altitude of 6-20 km (3.7-12.4 miles). The height of the tropopause (upper boundary) varies with latitude, being higher at the equator (around 16-18 km) and lower at the poles (around 8-10 km). This layer contains about 75% of the atmosphere's mass and 99% of its water vapor and aerosols. SUBJECT | Geography 1 of 18  Download Testbook App Temperature decreases with altitude at an average rate of 6.5°C per 1000m (3.6°F per 1000 feet) due to the adiabatic cooling of rising air. Almost all weather phenomena, such as the formation of clouds, precipitation, and atmospheric turbulence, occur within this layer. Stratosphere : The stratosphere extends from the tropopause (top of the troposphere) to an altitude of about 50 km (31 miles). Unlike the troposphere, temperature increases with altitude in the stratosphere due to the presence of the ozone layer. The ozone layer is a region of high ozone (O₃) concentration in the stratosphere, typically between 15-35 km altitude. Ozone absorbs harmful ultraviolet radiation from the Sun, protecting life on Earth from its damaging effects. This layer is incredibly dry, with little or no water vapor, and has high static stability, which means there is minimal vertical air movement. Mesosphere: The mesosphere extends from the stratopause (top of the stratosphere) to an altitude of about 80-85 km (50-53 miles). Temperature decreases with altitude in this layer due to decreasing molecular oxygen concentration, which absorbs solar radiation. Meteorites burn up in this layer due to friction with the atmosphere, creating stunning meteor showers. Thermosphere: The thermosphere is the fourth and outermost layer of the atmosphere, extending from the mesopause to an altitude of about 600 km (372 miles). Temperature increases dramatically with altitude in the thermosphere due to the absorption of high-energy X-rays and ultraviolet radiation from the Sun by oxygen molecules. This layer is where the International Space Station and many satellites orbit the Earth, as the atmosphere is extremely thin at these altitudes. Exosphere: The exosphere is the outermost region of the atmosphere, where it gradually transitions into the vacuum of space. It extends from the top of the thermosphere up to 10,000 km (6,200 miles) above the Earth's surface. SUBJECT | Geography 2 of 18  Download Testbook App In this region, atoms and molecules escape into space and the atmosphere merges with the solar wind, a stream of charged particles from the Sun. Composition of the Atmosphere The atmosphere is a mixture of gases, with the following primary constituents by volume: Nitrogen (N ₂) - 78.08%: Nitrogen is an inert gas that does not react chemically with other compounds in the atmosphere. It is essential for life processes, being a component of proteins and nucleic acids. Nitrogen is also used in the production of ammonia, nitric acid, and other industrially important compounds. Oxygen (O₂) - 20.95%: Oxygen is a highly reactive gas that supports life through respiration and combustion processes. It is also essential for the formation of ozone (O₃) in the stratosphere, which protects us from harmful ultraviolet radiation. Oxygen is used in various industrial processes, such as steel production, and in medical applications. Argon (Ar) - 0.93%: Argon is an inert gas that does not participate in chemical reactions under normal conditions. It is used in various industrial applications, such as lighting, welding, and the production of semiconductor devices. Carbon Dioxide (CO₂) - 0.04%: Carbon dioxide is a greenhouse gas that plays a vital role in regulating the Earth's temperature through the greenhouse effect. Its concentration has increased significantly due to human activities, such as the burning of fossil fuels and deforestation, leading to global warming and climate change. Carbon dioxide is essential for photosynthesis in plants and is used in various industrial processes, such as carbonation and fire extinguishers. Water Vapor (H₂O) - Variable, typically 0-4%: Water vapor is the most abundant greenhouse gas and plays a crucial role in the Earth's weather and climate systems. Its concentration varies depending on temperature and atmospheric conditions, being higher in warm, humid regions and lower in cold, dry regions. Water vapor is essential for cloud formation and precipitation, and it is a byproduct of various natural and human-made processes, such as respiration, combustion, and industrial activities. Other Trace Gases in the atmosphere include: Ozone (O₃) - Concentrated in the stratosphere, it absorbs harmful ultraviolet radiation from the Sun, protecting life on Earth. SUBJECT | Geography 3 of 18  Download Testbook App Methane (CH₄) - A potent greenhouse gas produced by natural sources, such as wetlands and ruminant animals, as well as human-made sources, such as agriculture, fossil fuel extraction, and waste management. Nitrous Oxide (N₂O) - A greenhouse gas produced by natural sources, such as microbial processes in soils and oceans, and human-made sources, including agricultural activities and industrial processes. Chlorofluorocarbons (CFCs) - Synthetic compounds that were widely used as refrigerants and aerosol propellants, but have been phased out due to their contribution to ozone depletion in the stratosphere. The atmosphere also contains suspended particulate matter, such as dust, smoke, pollen, and pollutants, which can affect air quality, visibility, and climate. These particles can either absorb or scatter solar radiation, influencing the Earth's radiation balance and climate. Importance of the Atmosphere Oxygen is very important for living beings. Carbon dioxide is very useful for plants. Dust particles present in the atmosphere create suitable conditions for the precipitation. The amount of water vapour in the atmosphere goes on changing and directly affects the plants and living beings. Ozone protects all kinds of life on the earth from the harmful ultraviolet rays of the sun. Factors Controlling Weather and Climate Distance from the Equator: The sun’s rays fall vertically on the equator. The rays are inclined on the regions away from the equator and near the poles due to the spherical shape of the earth. The vertical rays heat up the earth more than the inclined rays. Thus, the places near the equator are warmer than the places which are far away from the equator. Altitude: Altitude refers to the height above sea level. The temperature decreases at the rate of 1° C for every 165 mt of height. This is called Normal lapse rate. So, places at the higher altitude have a lower temperature. Nearness to the Sea: The climate of a place varies according to its nearness to the sea. Places near the coast experience an equable climate due to the influence of the winds from the sea. Places located in the land, far from the sea, do not SUBJECT | Geography 4 of 18  Download Testbook App experience the moderating influence of the sea, such places experience a continental type of climate. Air Definition: Air is a mixture of gases, primarily nitrogen and oxygen, with smaller amounts of other gases and particulate matter. Importance: Air is essential for sustaining life on Earth, as it provides the oxygen necessary for respiration and supports the growth of plants through photosynthesis. Clean air is crucial for human health, as polluted air can cause respiratory problems, cardiovascular diseases, and other health issues. Atmospheric Pressure and Density Definition: Atmospheric pressure is the force exerted by the weight of the air molecules above a given point on the Earth's surface. It decreases with increasing altitude due to the decrease in the number of air molecules above that point. The density of the atmosphere also decreases with altitude, as the gas molecules become more spread out. At sea level, the average atmospheric pressure is approximately 1013.25 millibars (mb) or 14.7 pounds per square inch (psi), and the air density is about 1.225 kg/m³. Atmospheric pressure and density play crucial roles in various atmospheric processes, such as weather patterns, aircraft flight, and the transmission of sound waves. Atmosphere and Weather The atmosphere is responsible for the weather phenomena experienced on Earth. Changes in temperature, humidity, wind direction, and atmospheric pressure cause weather changes. Clouds are formed by the condensation of water vapor in the atmosphere when air cools below its dew point temperature. Precipitation occurs when water droplets or ice crystals become too heavy to remain suspended in the air and fall to the Earth's surface as rain, snow, or other forms of precipitation. The movement of air masses, caused by differences in atmospheric pressure, is responsible for the formation of winds. Weather patterns are influenced by various factors, including the Earth's rotation, the distribution of land and water masses, and global air circulation patterns. Weather and Climate Weather: Weather refers to the state of the atmosphere at a particular place and time, described in terms of temperature, humidity, wind, precipitation, and cloud cover. Weather is constantly changing and is influenced by various factors, such as air pressure, wind patterns, humidity, and the presence of weather systems like fronts and cyclones. Climate: Climate is the average weather pattern observed over a long period of time (typically 30 years or more) in a particular region or location. Climate is determined by factors such as latitude, altitude, proximity to water bodies, prevailing winds, and ocean currents. SUBJECT | Geography 5 of 18  Download Testbook App Factors Affecting Weather and Climate Latitude: Latitude plays a significant role in determining the amount of solar radiation received at a particular location, which in turn affects temperature and climate patterns. Areas near the equator receive more direct sunlight and have a tropical climate, while areas closer to the poles receive less direct sunlight and have a polar or arctic climate. Altitude: As altitude increases, temperature generally decreases due to the lower density of the atmosphere and reduced insulation from atmospheric gases. High-altitude regions tend to have cooler climates and experience more extreme temperature variations compared to low-lying areas. Proximity to Water Bodies: Areas near large water bodies, such as oceans and lakes, tend to have a more moderate climate due to the moderating influence of water on temperature. Coastal regions often experience milder temperatures and higher humidity levels compared to inland areas. Prevailing Winds: Prevailing winds can carry moisture and heat from one region to another, affecting weather patterns and climate. For example, the westerly winds in mid-latitudes bring moisture from the oceans, contributing to the formation of precipitation and influencing climate patterns. Ocean Currents: Ocean currents can transport warm or cold water masses, influencing the climate of coastal regions. Warm currents, such as the Gulf Stream in the Atlantic Ocean, can bring warmer temperatures to coastal areas, while cold currents can have a cooling effect. Topography: The presence of mountains, valleys, and other topographic features can affect wind patterns, precipitation, and temperature distribution, leading to diverse microclimates within a region. Human Activities: Human activities, such as urbanization, deforestation, and the burning of fossil fuels, can contribute to changes in weather patterns and climate through the release of greenhouse gases, particulate matter, and alterations to the Earth's surface. Weather Phenomena Clouds: Clouds are formed by the condensation of water vapor in the atmosphere when air cools below its dew point temperature. Different types of clouds, such as cumulus, stratus, and cirrus, are classified based on their appearance and altitude. Precipitation: Precipitation occurs when water droplets or ice crystals become too heavy to remain suspended in the air and fall to the Earth's surface as rain, snow, sleet, or hail. The formation of precipitation depends on factors like temperature, humidity, and the presence of condensation nuclei. Winds: Winds are horizontal movements of air caused by differences in atmospheric pressure. Wind patterns are influenced by factors such as the Earth's rotation (Coriolis effect), temperature differences, and the presence of landforms and water bodies. Thunderstorms and Lightning: Thunderstorms are formed when warm, moist air rises and cools, leading to the formation of cumulonimbus clouds and the potential for heavy precipitation, strong winds, and lightning. Lightning is a powerful electrical discharge that occurs within thunderstorms, caused by the buildup and separation of electrical charges. Cyclones and Anticyclones: Cyclones are low-pressure systems characterized by inward-spiraling winds and often associated with heavy precipitation and severe weather. Anticyclones are high-pressure systems with outward-spiraling SUBJECT | Geography 6 of 18  Download Testbook App winds and generally fair weather conditions. Fronts: Fronts are boundaries separating air masses with different temperatures and humidity levels. Types of fronts include warm fronts, cold fronts, and occluded fronts, each with its own distinct weather patterns. Weather Forecasting and Monitoring Weather forecasting involves analyzing current atmospheric conditions and using computer models to predict future weather patterns. Weather data is collected from various sources, including ground-based weather stations, weather balloons, satellites, and radar systems. Meteorologists use this data, along with advanced computer models and knowledge of atmospheric processes, to make weather predictions. Accurate weather forecasting is crucial for various sectors, including agriculture, aviation, disaster management, and public safety. Climate Change Climate change refers to long-term shifts in global or regional climate patterns, often attributed to human activities that increase greenhouse gas concentrations in the atmosphere. The burning of fossil fuels, deforestation, and certain agricultural practices have contributed to an increase in atmospheric greenhouse gases like carbon dioxide and methane. Rising temperatures, sea-level rise, melting glaciers, and more frequent extreme weather events are some of the observed impacts of climate change. Mitigating and adapting to climate change requires global efforts to reduce greenhouse gas emissions, promote sustainable practices, and develop resilient communities. Season Definition: A year is divided into seasons depending upon variations in atmospheric conditions. They are specified periods in a year which have similar weather conditions. Season is a period of the year characterized by a particular set of weather conditions resulting from the inclination of the earth’s axis and the revolution of the earth around the sun. SUBJECT | Geography 7 of 18  Download Testbook App The same cycle of season is repeated year after year. Four seasons, each of three months duration, have been recognized in temperate regions. They are spring, summer, autumn, and winter. In our country, we have three distinct seasons which are summer, winter, and rainy. The Indian Meteorological Department has recognized four main seasons: Cold weather season (December to February) Hot weather season (March to May) Advancing monsoon season or rainy season ( June to September) Retreating monsoon season (October to November) Traditionally, there are six seasons in North India: Basant Ritu (Chaitra-Vaishakh or March-April) Greeshm Ritu ( Jyestha-Ashadh or May-June) Varsha Ritu (Shravan-Bhadrapad or July-August) Sharad Ritu (Aswina-Kartika or September-October) Hemant Ritu (Margashirsha-Posh or November-December) Shishir Ritu (Magh-Falgun or January-February) The rays of the sun are more or less direct on the equator throughout the year. Hence, equatorial regions experience the same temperature all year round. Therefore, seasons are insignificant on or near the equator. Near the coast, the oceanic influence reduces the seasonal variations. In the polar regions, there are only two seasons i.e., long winter and short summer. Temperature Definition: Temperature is a measure of the degree of hotness or coldness of a substance, typically expressed in Celsius (°C) or Fahrenheit (°F) scales. In the atmosphere, temperature varies with altitude, latitude, season, and other factors. The troposphere, the lowest layer of the atmosphere, exhibits a general decrease in temperature with increasing altitude, known as the environmental lapse rate (approximately 6.5°C/1000m or 3.6°F/1000ft). Temperature variations in the atmosphere are influenced by factors such as: Latitude: Areas closer to the equator receive more direct sunlight, resulting in higher temperatures than regions closer to the poles. Altitude: Higher altitudes have lower temperatures due to the decreasing density of the atmosphere and reduced insulation from atmospheric gases. Land and water masses: Water bodies tend to moderate temperatures, while land masses experience greater temperature extremes due to their lower heat capacity. Cloud cover: Clouds can reflect incoming solar radiation, leading to cooler temperatures during the day, but also trap outgoing longwave radiation, resulting in warmer temperatures at night. Greenhouse gases: Gases like carbon dioxide, methane, and water vapor absorb and re-emit infrared radiation, contributing to the greenhouse effect and warming the Earth's surface and lower atmosphere. Air Pressure SUBJECT | Geography 8 of 18  Download Testbook App Definition: Air pressure is the force exerted by the weight of the atmosphere on a given surface area. It is typically measured using a barometer and expressed in units like millibars (mb) or hectopascals (hPa). Air pressure decreases with increasing altitude due to the decreasing density of the atmosphere. At sea level, the average air pressure is approximately 1013.25 millibars (mb) or 14.7 pounds per square inch (psi). Differences in air pressure are the driving force behind wind and atmospheric circulation patterns. High-pressure systems are associated with fair weather conditions, while low-pressure systems often bring cloudy, rainy, or stormy weather. Air pressure is also influenced by temperature, with warm air being less dense and exerting less pressure than cooler air. Winds and Their Types Definition: Wind is the horizontal movement of air caused by differences in air pressure. Winds flow from areas of high pressure to areas of low pressure, seeking to restore equilibrium. The Coriolis effect, caused by the Earth's rotation, deflects wind patterns, resulting in clockwise rotation in the Northern Hemisphere and counterclockwise rotation in the Southern Hemisphere. Types of winds include: Planetary winds: Global-scale wind patterns driven by the uneven heating of the Earth's surface and the Coriolis effect, such as trade winds, westerlies, and polar easterlies. Local winds: Winds influenced by local geographic features and temperature differences, such as land and sea breezes, mountain and valley winds, and katabatic winds. Cyclonic winds: Winds associated with cyclones (low-pressure systems), such as hurricanes, typhoons, and extratropical cyclones, which can be destructive and bring heavy precipitation and strong winds. Jet streams: Narrow bands of strong winds in the upper troposphere and lower stratosphere, resulting from temperature contrasts between air masses and influenced by the Earth's rotation. Moisture Definition: Moisture in the atmosphere refers to the presence of water vapor, a gaseous form of water. Water vapor is a greenhouse gas that plays a crucial role in the Earth's weather and climate systems. The amount of water vapor the air can hold depends on its temperature, with warmer air having a higher capacity to hold moisture than cooler air. Relative humidity is a measure of the amount of water vapor present in the air compared to the maximum amount the air can hold at a given temperature. High relative humidity can lead to the formation of clouds, fog, and precipitation, while low relative humidity can contribute to dry conditions. The hydrological cycle, which involves evaporation, condensation, precipitation, and surface runoff, governs the distribution and movement of moisture in the atmosphere. Moisture sources include evaporation from water bodies, transpiration from plants, and moisture transport by wind patterns. SUBJECT | Geography 9 of 18  Download Testbook App The distribution of moisture in the atmosphere is influenced by factors such as temperature, air pressure, wind patterns, and the presence of landforms and water bodies. Insolation Definition: The earth receives almost all of its energy from the sun. The earth in turn radiates back to space the energy received from the sun. As a result, the earth neither warms up nor does it get cooled over a period of time. Thus, the amount of heat received by different parts of the earth is not the same. This variation causes pressure differences in the atmosphere, leading to the transfer of heat from one region to the other by winds. Solar Radiation: The earth’s surface receives most of its energy in short wavelengths. The energy received by the earth is known as incoming solar radiation which in short is termed as insolation. As the earth is a geoid resembling a sphere, the sun’s rays fall obliquely at the top of the atmosphere and the earth intercepts a very small portion of the sun’s energy. Only two billionths or (two units of energy out of 1,00,00,00,000 units of energy radiated by the sun) of the total solar radiation reaches the earth’s surface. The amount of insolation received on the earth’s surface is far less than that radiated from the sun because of the small size of the earth and its distance from the sun. Moreover, water vapour, dust particles, ozone, and other gases present in the atmosphere absorb a small amount of insolation. On an average, the earth receives 1.94 calories per sq. cm per minute at the top of its atmosphere. The solar output received at the top of the atmosphere varies slightly in a year due to the variations in the distance between the earth and the sun. During its revolution around the sun, the earth is farthest from the sun (152 million km) on 4th July. This position of the earth is called aphelion. On 3rd January, the earth is the nearest to the sun (147 million km). This position is called perihelion. Therefore, the annual insolation received by the earth on 3rd January is slightly more than the amount received on 4th July. However, the effect of this variation in the solar output is masked by other factors like the distribution of land and sea and the atmospheric circulation. Hence, this variation in the solar output does not have a great effect on daily weather changes on the surface of the earth. Variability of Insolation at the Surface of the Earth The amount and the intensity of insolation vary during a day, in a season, and in a year. The factors that cause these variations in insolation are: Angle of inclination of the sun’s rays: Since the earth is round, the sun’s rays strike the surface at different angles at different places. The angle formed by the sun’s ray with the tangent of the earth’s circle at a point is called the angle of incidence. It influences the insolation in two ways. First, when the sun is almost overhead, the rays of the sun are vertical. The angle of incidence is large, hence, they are concentrated in a smaller area, giving more amount of insolation at that place. If the sun’s rays are oblique, the angle of incidence is small and the sun’s rays have to heat up a greater area, resulting in less amount of insolation received there. Secondly, the sun’s rays, with a small angle, traverse more of the atmosphere, than rays striking at a large angle. The longer the path of the sun's SUBJECT | Geography 10 of 18  Download Testbook App rays, the greater the amount of reflection and absorption of heat by the atmosphere. As a result, the intensity of insolation at a place is less. Length of the day: Duration of the day varies from place to place and season to season. It decides the amount of insolation received on earth’s surface. The longer the duration of the day, the greater the amount of insolation received. Conversely, a shorter duration of the day leads to receipt of less insolation. Rotation of the Earth on its axis: The earth’s axis, making an angle of 66.5° with the plane of its orbit around the sun, has a greater influence on the amount of insolation received at different latitudes. Do You Know? Amount of insolation at a place depends upon the angle of incidence, duration of the day, and transparency of the atmosphere. Length of the Day in Hours and Minutes on Winter and Summer Solstices in the Northern Hemisphere Latitude December 22 June 21 0° 12 Hours 12 Hours 20° 10 Hours 48 Minutes 13 Hours 12 Minutes 40° 09 Hours 08 Minutes 14 Hours 52 Minutes 60° 05 Hours 33 Minutes 18 Hours 27 Minutes 90° 0 06 Months The Passage of Solar Radiation through the Atmosphere (Transparency of the Atmosphere) Transparency of the atmosphere also determines the amount of insolation reaching the earth’s surface. The transparency depends upon cloud cover, its thickness, dust particles and water vapour, as they reflect, absorb or transmit insolation. Thick clouds hinder the insolation to reach the earth while clear sky helps it to reach the surface. Water vapour absorbs insolation, resulting in less amount of insolation reaching the surface. SUBJECT | Geography 11 of 18  Download Testbook App Spatial Distribution of Insolation at the Earth’s Surface: The insolation received at the surface varies from about 320 Watt/m² in the tropics to about 70 Watt/m² in the poles. Maximum insolation is received over the subtropical deserts, where the cloudiness is the least. The Equator receives comparatively less insolation than the tropics. Generally, at the same latitude, the insolation is more over the continent than over the oceans. In winter, the middle and higher latitudes receive less radiation than in summer. Heating and Cooling of the Atmosphere: Heating of the atmosphere is an indirect process. There are different ways of heating and cooling of the atmosphere. Conduction: The earth after being heated by insolation transmits the heat to the atmospheric layers near to the earth in long wave form. The air in contact with the land gets heated slowly and the upper layers in contact with the lower layers also get heated. This process is called conduction. Conduction takes place when two bodies of unequal temperature are in contact with one another, there is a flow of energy from the warmer to cooler body. The transfer of heat continues until both the bodies attain the same temperature or the contact is broken. Conduction is important in heating the lower layers of the atmosphere. Convection: Transfer of heat by movement of a mass or substance from one place to another, generally vertical, is called convection. The air of the lower layers of the atmosphere gets heated either by the earth’s radiation or by conduction. The heating of the air leads to its expansion. Its density decreases, and it moves upwards. Continuous ascent of heated air creates a vacuum in the lower layers of the atmosphere. As a consequence, cooler air comes down to fill the vacuum, leading to convection. The cyclic movement associated with the convectional process in the atmosphere transfers heat from the lower layer to the upper layer and heats up the atmosphere. Advection: The transfer of heat through horizontal movement of air is called advection. Horizontal movement of the air is relatively more important than the vertical movement. In middle latitudes, most of the diurnal (day and night) variations in daily weather are caused by advection alone. In tropical regions, particularly in northern India during summer season, local winds called ‘loo’ is the outcome of the advection process. Radiation: Radiation is the process by which solar energy reaches the earth and the earth loses energy to outer space. When the source of heat transmits heat directly to an object through heat waves, it is known as a radiation process. In this process, heat travels through empty space. The vast amount of heat energy coming to and leaving the earth is in the form of radiation. The following facts about radiation are worth noting: Climate in India India's diverse climate is influenced by several geographical factors, leading to a wide range of weather conditions across the country. Monsoons: India's climate is heavily influenced by monsoon winds. The southwest monsoon brings most of the country's annual rainfall between June and September. This monsoon starts from the Indian Ocean and brings moisture-laden winds SUBJECT | Geography 12 of 18  Download Testbook App to the subcontinent. The northeast monsoon affects the coastal regions of the eastern Indian peninsula during October and November, causing rainfall primarily in Tamil Nadu and parts of Andhra Pradesh. Climatic Zones: India can be divided into several climatic zones: Tropical Rainy Climate: Dominated by the monsoons, this climate affects the majority of the country, especially the southern and eastern parts. Dry Climate: Found in the northwestern part of India, including Rajasthan and Gujarat, characterized by very little rainfall and high temperatures. Temperate Climate: Prevails in the Himalayan region, with cold winters and relatively cool summers. Seasonal Variation: The Indian climate is categorized into three main seasons: Summer (March to May): Hot weather prevails with temperatures reaching up to 50°C in some parts. Monsoon ( June to September): Brings rainfall across the country, which is crucial for agriculture. Winter (December to February): Cooler temperatures, especially in the northern regions, with snowfall in the higher altitudes of the Himalayas. Vegetation in India India is a land of great variety of natural vegetation. Himalayan heights are marked with temperate vegetation; the Western Ghats and the Andaman Nicobar Islands have tropical rainforests, the deltaic regions have tropical forests and mangroves; the desert and semi desert areas of Rajasthan are known for cactii, a wide variety of bushes and thorny vegetation. Depending upon the variations in the climate and the soil, the vegetation of India changes from one region to another. On the basis of certain common features such as predominant vegetation type and climatic regions, Indian forests can be divided into the following groups: Natural Vegetation in India Moist Tropical Evergreen Vegetation These are the tropical rain forests which are further divided into two subtypes on the basis of their characteristics as under: The Wet Tropical Evergreen Vegetation: These forests are found in the western slope of the Western Ghats, hills of the northeastern region and the Andaman and Nicobar Islands. They are found in warm and humid areas with an annual precipitation of over 200 cm and mean annual temperature above 22°C. It resembles equatorial vegetation. Tropical evergreen forests are well stratified, with layers closer to the ground and are covered with shrubs and creepers, with short structured trees followed by a tall variety of trees. In these forests, trees reach great heights up to 60 m or above. There is no definite time for trees to shed their leaves, flowering and fruition. As such these forests appear green all the year round. Species found in these forests include rosewood, mahogony, aini, ebony, etc. The major characteristics of this type of vegetation are: These forests are dense and have lofty evergreen trees, often as high as 60 metres and above. SUBJECT | Geography 13 of 18  Download Testbook App The number of vegetal species per unit area is too large to exploit them commercially. Mahogany, cinchona, bamboos and palms are typical species of plants found in these forests. Undergrowth is very dense and thick. Grass is almost absent. The wood of these trees is very hard and heavy to work with. Moist Tropical Semi-evergreen Vegetation: It is found between wet evergreen vegetation and moist temperate deciduous vegetation (or say less rainy parts). Such forests have a mixture of evergreen and moist deciduous trees. The under growing climbers provide an evergreen character to these forests. Main species are white cedar, hollock and kail. The British were aware of the economic value of the forests in India, hence, large scale exploitation of these forests was started. The structure of forests was also changed. The oak forests in Garhwal and Kumaon were replaced by pine (chirs) which were needed to lay railway lines. Forests were also cleared for introducing plantations of tea, rubber and coffee. The British also used timber for construction activities as it acts as an insulator of heat. The protectional use of forests was, thus, replaced by commercial use. This type of vegetation is found on the Meghalaya plateau, Sahyadris and Andaman and Nicobar Islands. This vegetation is confined to areas receiving an annual rainfall of about 250 to 300 cms. Its important characteristics are: The vegetation cover is less dense than the wet evergreen forests. Timber of these forests is fine textured and of good quality. Rosewood, aini and telsur are important trees in Sahyadris, champa joon and gurjan in Assam and Meghalaya and ironwood, ebony and laurel grew in other regions. Shifting agriculture and over exploitation of forests have depleted this vegetal cover to a great extent. Tropical Deciduous Vegetation These are the most widespread forests in India. They are also called the monsoon forests. They spread over regions which receive rainfall between 100-200 cm. On the basis of the availability of water, these forests are further divided into moist and dry deciduous. Moist Tropical Deciduous Vegetation: This is the most widespread vegetal cover of India. This type of vegetation is found in areas receiving annual rainfall of 100 to 200 cm. These forests are found in the northeastern states along the foothills of Himalayas, eastern slopes of the Western Ghats and Odisha. Teak, sal, shisham, hurra, mahua, amla, semul, kusum, and sandalwood etc. are the main species of these forests. The important characteristics of this vegetation are: The trees shed their leaves once a year in the dry season. This is a typical monsoon vegetation consisting of a larger number of commercially important species than the evergreen forests. Large scale cutting of trees for timber has depleted these forests hopelessly. Dry Tropical Vegetation (Tropical Thorn Forests): This type of vegetation is divided into two groups as under: Dry Tropical Deciduous Vegetation: It is found in regions receiving annual rainfall between 70 to 100 cms. These regions include parts of Uttar Pradesh, northern and western Madhya Pradesh, parts of Gujarat, SUBJECT | Geography 14 of 18  Download Testbook App Maharashtra, Andhra Pradesh, Karnataka and Tamil Nadu. These areas experience a long dry season and a moderate rainfall limited at best to four months. In the higher rainfall regions of the Peninsular plateau and the northern Indian plain, these forests have a parkland landscape with open stretches in which teak and other trees interspersed with patches of grass are common. As the dry season begins, the trees shed their leaves completely and the forest appears like a vast grassland with naked trees all around. Tendu, palas, amaltas, bel, khair, axlewood, etc. are the common trees of these forests. In the western and southern part of Rajasthan, vegetation cover is very scanty due to low rainfall and overgrazing. The important characteristics of this vegetation are: Stretches of open grass are most common between groups of trees. Teak is the dominant tree of this type of vegetation. The trees shed their leaves during the long dry season. Dry Tropical Thorny Vegetation: It is found in areas receiving annual rainfall less than 50 cm. These areas include north and northwestern parts of India and the leeward side of the Sahyadris. It includes semi-arid areas of south west Punjab, Haryana, Rajasthan, Gujarat, Madhya Pradesh and Uttar Pradesh. In these forests, plants remain leafless for most part of the year and give an expression of scrub vegetation. Important species found are babool, ber, and wild date palm, khair, neem, khejri, palas, etc. Tussocky grass grows upto a height of 2 m as the undergrowth. The important characteristics of this type of vegetation are: Vast, poor and coarse grasslands are interspersed with widely spaced trees and bushes. Acacia, euphorbias, cactus etc. are true representatives of this type of vegetation. Wild palm and spiny and thorny varieties are also found here and there. Tidal Vegetation This type of vegetation grows mainly in the deltaic regions of the Ganga, Mahanadi, Godavari and Krishna which are flooded by tides and high sea waves. Mangrove is the representative of this type of vegetation. Sundari is the typical tree of tidal forests. It is found in abundance in the lower Ganga delta of West Bengal. This is the reason why it is popularly known as Sunderban. It is known for its hard and durable timber. Littoral and Swamp Vegetation India has a rich variety of wetland habitats. About 70 per cent of this comprises areas under paddy cultivation. The total area of wet land is 3.9 million hectares. Two sites — Chilika Lake (Odisha) and Keoladeo National Park (Bharatpur) are protected as water-fowl habitats under the Convention of Wetlands of International Importance (Ramsar Convention). The country’s wetlands have been grouped into eight categories, viz. the reservoirs of the Deccan Plateau in the south together with the lagoons and other wetlands of the southern west coast; the vast saline expanses of Rajasthan, Gujarat and the Gulf of Kachchh; freshwater lakes and reservoirs from Gujarat eastwards through Rajasthan (Keoladeo National Park) and Madhya Pradesh; the delta wetlands and lagoons of India’s east coast (Chilika Lake); SUBJECT | Geography 15 of 18  Download Testbook App the freshwater marshes of the Gangetic Plain; the floodplains of the Brahmaputra; the marshes and swamps in the hills of northeast India and the Himalayan foothills; the lakes and rivers of the montane region of Kashmir and Ladakh; and the mangrove forest and other wetlands of the island arcs of the Andaman and Nicobar Islands. Mangroves grow along the coasts in the salt, marshes, tidal creeks, mud flats and estuaries. They consist of a number of salt-tolerant species of plants. Crisscrossed by creeks of stagnant water and tidal flows, these forests give shelter to a wide variety of birds} In India, the mangrove forests spread over 6,740 sq. km which is 7 percent of the world’s mangrove forests. They are highly developed in the Andaman and Nicobar Islands and the Sundarbans of West Bengal. Other areas of significance are the Mahanadi, the Godavari and the Krishna deltas. These forests too, are being encroached upon, and hence, need conservation. The Mountain Vegetation (Montane Forests) Due to the difference in temperature and other weather conditions of northern and peninsular mountain ranges, there exists difference in the vegetal cover of these two groups of mountain ranges. Hence, the mountain vegetation can be classified as the mountain vegetation of the Peninsular plateau and the mountain vegetation of the Himalayan ranges. The Mountain Vegetation of Peninsular Plateau: The high altitude area of the plateau region include Nilgiri, Annamalai and Palni hills, Mahabaleshwar in Western Ghats, Satpura and Maikal hills. The important characteristics of vegetation of this region are: Stretches of open rolling grass plains with undeveloped forests or bushes are found. The wet temperate forests below 1500 metres are less dense than those found above this height. The forests have thick undergrowth, epiphytes, mosses and ferns. Magnolia, laurel, elm are common trees. Cinchona and eucalyptus have been introduced from outside the country. The Mountain Vegetation of the Himalayan Ranges: In mountainous areas, the decrease in temperature with increasing altitude leads to a corresponding change in natural vegetation. Mountain forests can be classified into two types, the northern mountain forests and the southern mountain forests. The Himalayan ranges show a succession of vegetation from the tropical to the tundra, which change with the altitude. Deciduous forests are found in the foothills of the Himalayas. It is succeeded by the wet temperate type of forests between an altitude of 1,000-2,000 m. In the higher hill ranges of northeastern India, hilly areas of West Bengal and Uttaranchal, evergreen broad leaf trees such as oak and chestnut are predominant. Between 1,500-1,750 m, pine forests are also well-developed in this zone, with Chir Pine as a very useful commercial tree. Deodar, a highly valued endemic species, grows mainly in the western part of the Himalayan range. Deodar is a durable wood mainly used in construction activity. Similarly, the chinar and the walnut, which sustain the famous Kashmir handicrafts, belong to this zone. Blue pine and spruce appear at altitudes of 2,225-3,048 m. At many places in this zone, temperate grasslands are also found. But in the higher reaches there is a transition to Alpine forests and pastures. Silver firs, junipers, pines, SUBJECT | Geography 16 of 18  Download Testbook App birch and rhododendrons, etc. occur between 3,000-4,000 m. However, these pastures are used extensively for transhumance by tribes like the Gujjars, the Bakarwals, the Bhotiyas and the Gaddis. The southern slopes of the Himalayas carry a thicker vegetation cover because of relatively higher precipitation than the drier north-facing slopes. At higher altitudes, mosses and lichens form part of the tundra vegetation. The southern mountain forests include the forests found in three distinct areas of Peninsular India viz; the Western Ghats, the Vindhyas and the Nilgiris. As they are closer to the tropics, and only 1,500 m above the sea level, vegetation is temperate in the higher regions, and subtropical on the lower regions of the Western Ghats, especially in Kerala, Tamil Nadu and Karnataka. The temperate forests are called Sholas in the Nilgiris, Anaimalai and Palani hills. Some of the other trees of this forest of economic significance include, magnolia, laurel, cinchona and wattle. Such forests are also found in the Satpura and the Maikal ranges. In the Himalayan mountain region, the vegetation is different at increasing altitudes. Generally, this can be divided into following types: Moist Tropical Deciduous Forests: These are found along the foothills in the Siwaliks, upto the height of 1000 metres. We have already learnt about these forests. Wet Temperate Evergreen Forests: These are found in the areas lying between 1000 to 3000 metres. The important characteristics of these forests are: These are very thick forests of lofty trees. Oak and chestnut are the predominant trees of the eastern Himalayan region while chir and pine are in the western part. Sal is an important tree in lower altitudes. Deodar, silver fir and spruce are predominant trees between the height of 2000 and 3000 metres. These forests are less dense as compared to the forests at lesser elevations. These forests are of great economic importance to the local population. Dry Temperate Vegetation: It is found on the higher hilly slopes of this mountain region which has moderate temperatures and rainfall between 70 cm and 100 cm. Important characteristics of this type of vegetation are: This vegetation resembles Mediterranean vegetation. Wild olives, acacia are important trees along with hard, coarse and thick savanna grass. Oak and deodar are found here and there. Alpine Vegetation: It is found between the altitude 3000 and 4000 metres. The important characteristics of these forests are: These are far less dense, Silver fir, juniper, birch, pine and rhododendron are important trees of these forests. However, all of them have only stunted growth. Alpine pastures are still found at higher altitudes. The trees get progressively stunted as they approach the snow line. Wildlife in India SUBJECT | Geography 17 of 18  Download Testbook App India's diverse ecosystems support a vast array of wildlife: Mammals: India has a rich variety of mammals due to its diverse habitats. This includes the Bengal tiger, Asiatic lion (found only in the Gir Forest of Gujarat), Indian elephant, one-horned rhinoceros (primarily in Assam), and numerous deer species. Birds: India is a haven for bird watchers with over 1,200 species. This includes the Indian peafowl, various species of parakeets, the Indian hornbill, and migratory birds such as Siberian cranes. Reptiles and Amphibians: The country is home to numerous reptiles like the king cobra, Indian python, and various species of crocodiles and turtles. Amphibians like the Indian bullfrog and various other species are also common. Aquatic Life: India's long coastline and numerous rivers host diverse marine and freshwater species, including the Ganges river dolphin and a variety of fish and coral species. Conservation Efforts: India has implemented various conservation programs such as Project Tiger and Project Elephant to protect these species and their habitats. The country has established numerous national parks, wildlife sanctuaries, and biosphere reserves for this purpose. SUBJECT | Geography 18 of 18