“THE ATMOSPHERE AND THE HYDROSPHERE” PROF. EMILIA SARNO Pegaso International The Atmosphere and the Hydrosphere Index “THE ATMOSPHERE AND THE HYDROSPHERE” --------------------------------------------------------------------------- 1 1 INTRODUCTION -------------------------------------------------------------------------------------------------------------- 3 2 THE ATMOSPHERE --------------------------------------------------------------------------------------------------------- 4 3 THE NOTION OF CLIMATE ----------------------------------------------------------------------------------------------- 6 4 TYPES OF CLIMATE -------------------------------------------------------------------------------------------------------- 8 4.1. 4.2. 4.3. 4.4. 4.5. 5 THE HYDROSPHERE------------------------------------------------------------------------------------------------------- 13 5.1. 5.2. 5.3. 5.4. 5.5. 6 TROPICAL WET MEGATHERMAL CLIMATES -------------------------------------------------------------------------------- 8 TROPICAL AND DESERT ARID CLIMATES ----------------------------------------------------------------------------------- 9 SUBTROPICAL AND TEMPERATE MESOTHERMAL CLIMATES ------------------------------------------------------------ 9 MICROTHERMAL CLIMATES OF THE COLD REGIONS OF THE NORTHERN HEMISPHERE-----------------------------10 POLAR AND SUBPOLAR CLIMATES -----------------------------------------------------------------------------------------10 THE WATER CYCLE -----------------------------------------------------------------------------------------------------------13 OCEANS AND SEAS -----------------------------------------------------------------------------------------------------------14 SPRINGS AND RIVERS --------------------------------------------------------------------------------------------------------17 LAKES --------------------------------------------------------------------------------------------------------------------------20 GLACIERS ----------------------------------------------------------------------------------------------------------------------21 AIR AND WATER POLLUTION ----------------------------------------------------------------------------------------- 23 BIBLIOGRAPHY -------------------------------------------------------------------------------------------------------------------- 25 Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 2 di 26 Pegaso International The Atmosphere and the Hydrosphere 1 Introduction This lesson is concerned with two fundamental aspects of Earth: the atmosphere and the hydrosphere. The first part analyses the features of the atmosphere, factors and elements of the climate, and the various types of climate. The second part examines the water cycle and the characteristics of groundwater and surface water. Both the atmosphere and the hydrosphere make life possible on Earth and condition it. For this reason it is worth providing an outline of their characteristics1. 1 For this topic, see De Vecchis, 2001; Lupia Palmieri, Parotto, 2003; Nice, 1980. Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 3 di 26 Pegaso International The Atmosphere and the Hydrosphere 2 The Atmosphere The atmosphere (from a Greek word meaning “steam sphere”) is a gaseous layer that envelops Earth. It becomes thinner with altitude, and, while it does not have a clear limit, this is established to be at 2500 km from Earth’s surface. The atmosphere is divided into the following sections: - the Troposphere, - the Stratosphere, - the Mesosphere, - the Thermosphere, - and the Exosphere. The Troposphere is the lowest zone, in direct contact with Earth’s surface and is the site of phenomena such as rain, snow, etc. It extends to approximately 10 km from Earth’s surface. The Stratosphere extends to approximately 40 km and weather phenomena are almost absent. In its middle and upper part there is a layer of concentrated ozone that absorbs most solar ultraviolet radiation, protecting living organisms. The Mesosphere, which extends from 40 to 80 km from the surface, is characterized by the rarefaction of gaseous elements and by low temperatures. The Thermosphere extends up to 300-400 km and is characterized by high temperatures. The Exosphere extends beyond 400 km, where temperature increases. Figure 1 summarizes the zones of the atmosphere2. 2 The image is from: www.bo.astro.it. Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 4 di 26 Pegaso International The Atmosphere and the Hydrosphere Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 5 di 26 Pegaso International The Atmosphere and the Hydrosphere 3 The Notion of Climate Human beings have always been concerned about the weather conditions required for their survival and for agriculture. The climate is essential for human communities, which have settled in hot or temperate areas that are appropriate for crop and livestock farming. Hence the great interest in studying the climate. The notion of climate should be distinguished from weather: the climate being the result of all weather condition observed in a year in a specific area. It is therefore the average condition of the atmosphere in a specific place. In other words, the climate is defined by the most frequent phenomena, whereas the weather is a momentary and transient situation. The climate consists of elements and factors. Elements include: temperature, humidity, precipitations, cloudiness, wind, and atmospheric pressure. Temperature denotes air heat and is measured using a thermometer. Thermal range, i.e. the difference of day and night temperature in a specific place, is also measured in this way. Air is heated by solar heat indirectly: solar heat is absorbed less by the atmosphere than by Earth’s surface, which releases it, thereby indirectly heating the air. Humidity, clouds, and precipitations: the evaporation of waters brings vapor up in the air, and under certain conditions, such as the decrease of temperature, vapor forms clouds, which are masses of microscopic drops of water. When these drops become larger and heavier, they fall to the ground in the form of rain or snow, depending on the degree of cooling. Atmospheric pressure and winds: the air has a weight and its force is called atmospheric pressure, which is measured using a barometer. One liter of air at sea level at 0°C weighs exactly 1.293 grams, whereas at the outer limits of the atmosphere, its weigh is billions of times lower. Air Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 6 di 26 Pegaso International The Atmosphere and the Hydrosphere pressure can vary according to temperature, altitude, and humidity. Low-pressure areas basically have a smaller atmospheric mass, whereas high-pressure area have a larger atmospheric mass. Similarly, when altitude increases, pressure decreases. Pressure differences across areas are the main cause of winds. Winds are air masses moving from high-pressure areas to low-pressure areas. Climate factors include: latitude, altitude, and elevation. Latitude, i.e. a place’s distance from the equator, affects temperature. Air temperature is higher and constant at the equator, but it decreases gradually and varies across months, at growing latitudes. This is caused by the gradient at which solar radiation reaches Earth’s surface at different latitudes (Fig. 2). Elevation is another factor that affects the climate, because as elevation increases, temperature decreases approximately by one degree in every 180 meters of elevation. Elevation is of great importance in determining local climates, as it may cause significant variation in temperature and precipitation. Fig. 2: Solar radiation Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 7 di 26 Pegaso International The Atmosphere and the Hydrosphere 4 Types of Climate Based on elements and factors, there are different types of climates. According to the Köppen classification, climates can be: - wet megathermal; - arid; - mesothermal; - microthermal; - polar and alpine. 4.1. Tropical wet megathermal climates Wet megathermal climates are characterized by a minimum temperature of 15 °C and perennial rainfalls; this climate can be found at the tropics, where vegetation is thick. Wet tropical climates can be further divided into equatorial or rainforest climates, savanna climates, and monsoon climates. This distinction is based on the pluviometric regime, i.e. on the amount of liquid precipitation. Rainfalls are regular in the first case, seasonal in the second case, and determined by monsoons in the third case3. 3 Monsoons are cyclical winds of the Indian Ocean that are accompanied by violent tropical cyclones, called typhoons—stormy systems that fall on coasts with devastating effects. Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 8 di 26 Pegaso International 4.2. The Atmosphere and the Hydrosphere Tropical and desert arid climates Temperature is never below 18 °C and is generally high, but these climates are characterized by the scarcity of rain for entire years and—in the case of deserts—for decades. It is therefore the climate of dry steppes and deserts, where there is a considerable thermal excursion between day and night. 4.3. Subtropical and temperate mesothermal climates These are temperate climates with moderate precipitations and mild winters. They can be divided into three types: Chinese climate, Mediterranean climate, and cold temperate climate. 1) The Chinese warm temperate climate, with dry winters and wet summers, can be found in China (where it is characterized by monsoons), as well as in some regions of America, Africa, and Australia. 2) The Mediterranean warm temperate climate, with dry summers and wet winters, can be found in the Mediterranean, as well as in California and Central Chile. 3) The cold temperate climate, colder than the Mediterranean climate, and with regular rains, can be found in Central and Western Europe. Winters are mild and summers are cool. Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 9 di 26 Pegaso International The Atmosphere and the Hydrosphere 4.4. Microthermal climates of the cold regions of the Northern Hemisphere Long cold periods and short summers are dominant. The mean temperature in the warmest month is slightly above 10 °C. Snowfalls are frequent. 4.5. Polar and subpolar climates In these climates the sun never sets during the summer and temperatures are very low. They can be divided into two types: 1) Tundra climates, with mean temperatures above zero only in the summer, when superficial thawing of ice occurs. It can be found in land belts near the poles. 2) Polar glacial climate is characterized by perennial ice and mean temperatures below the zero. Figure 3 shows the distribution of climates on Earth according to the types described above, whereas Figure 4 shows the different climate types of Italy. Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 10 di 26 Pegaso International The Atmosphere and the Hydrosphere Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 11 di 26 Pegaso International The Atmosphere and the Hydrosphere Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 12 di 26 Pegaso International The Atmosphere and the Hydrosphere 5 The Hydrosphere The hydrosphere consists of all ground and surface waters. Water can be found: in the lithosphere (on Earth’s surface and in rocks) in the biosphere (in the composition of flora and fauna) in the atmosphere (in the form of clouds and vapor). 5.1. The water cycle The water cycle consists of the circulation of water within the hydrosphere, including physical state changes (liquid, solid, and gaseous). This creates constant exchanges of water masses among the atmosphere, the earth, surface or ground waters, and organisms. Changes include the following physical processes: evaporation, condensation, precipitation, infiltration (Fig. 5). Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 13 di 26 Pegaso International The Atmosphere and the Hydrosphere Fig. 5: Water evaporation forms clouds; rain falls from clouds; rivers flow into oceans; water reservoirs on emerged lands fill up; ground water returns to the ocean. 5.2. Oceans and seas Sea water covers 72% of Earth’s surface. The larger masses are called oceans, whereas seas are defined as areas surrounded by emerged lands on multiple sides. The most notable characteristic of sea water is salinity or saltiness, which is based on the amount of salt contained in 1 kg of water. The average salinity is 35 per thousand, therefore 35 grams of salt per 1 kg of water. The salts contained in sea water include sodium chloride, magnesium chloride, calcium chloride, etc. Salinity Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 14 di 26 Pegaso International The Atmosphere and the Hydrosphere is higher in tropical seas and lower in colder seas (Fig. 6). Sea water also contains oxygen and other dissolved gases. Temperature varies according to depth. Oceans are vast, deep stretches of saline water. According to the definition provided in 1953 by the International Hydrographic Bureau, there is one big ocean divided into three basins: Pacific Ocean, 180,000,000 square km Atlantic Ocean, 106,000,000 square km Indian Ocean, 75,000,000 square km. Earth is called “the Blue Planet” due to the color of oceans. Oceanic masses are essential for the ecologic equilibrium of the planet and for human beings. They are huge water reservoirs that fuel the water cycle: water evaporates from oceans into the atmosphere, then falls on the land in the form of precipitations, and finally flows back into oceans through rivers. Oceans are also heat reservoirs that absorb solar radiation and slowly release it. Therefore oceans also help attenuate temperature variation. Furthermore, ocean water is important as it provides human beings with huge amounts of fish, as well as with petroleum and natural gas, which are contained in submarine reservoirs. The most important organisms in ocean ecosystems are algae and bacteria, which are called phytoplankton. Phytoplankton is the primary producer of oxygen in marine environments. Seas are defined as bodies of salt water surrounded by land. This also includes closed salt lakes such as the Caspian Sea, the Dead Sea, and the Sea of Galilee. Oceans and seas are constantly moving. Their motion consists of waves, tides, and currents. Waves are caused by wind and produce a vertical movement. Waves can reach 15 meters in height, especially in deep water, whereas they slow down as they approach the coast and eventually break on the beach. Tides are periodical upward (high tide) or downward (low tide) movements of large Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 15 di 26 Pegaso International The Atmosphere and the Hydrosphere masses of water that occur on a daily basis, and are caused by the gravitational forces exerted by the Moon and the Sun. Sea currents are water masses driven by winds in a specific direction. Their motion depends on the push exerted by constant prevailing winds such as trade winds or monsoons. Currents may be warm (from equatorial regions) or cold (from polar regions). Fig. 6: The salinity of ocean and sea water Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 16 di 26 Pegaso International 5.3. The Atmosphere and the Hydrosphere Springs and rivers Once rain falls on the land, it penetrates into the subsoil or stays on the surface. Terrains that allow water to pass through them are called permeable. When water penetrates the soil, it forms aquifers—that is, underground reservoirs. If the water contained in these reservoirs emerges from the surface on a mountain or hill slope, it creates a spring. Springs feed rivers and streams; river waterways are generally longer and more regular than streams. Therefore a river is a waterway that is constantly fed by springs, rainwater, and snow. The banks through which rivers and streams flow are called beds. The parameters for studying rivers are the following: basin length gradient speed flow regime mouth. The portion of land that contributes to a river with its waters is called drainage basin; a river’s drainage basin is separated from another’s by watersheds. Each basin includes both the main river and its tributaries (Fig. 7). A river’s length is measured from its source and can extend across thousands of kilometers. The longest rivers in the world are the Nile-Kagera in Africa (6671 km), Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 17 di 26 Pegaso International The Atmosphere and the Hydrosphere the Amazon-Ucayali in South America (6280 km), the Mississippi in North America (5970 km), and the Volga in Europe (3531 km). A river’s gradient is the ratio of the height difference between its source and its mouth to its length. Rivers that have their sources on mountains have a high gradient. A river’s speed varies according to its gradient, as well as to its depth and bed. The flow is the volume of water (in cubic meters) that passes in one second through a transversal section. Each river has an average flow, a minimum flow (for example during the summer) and a maximum flow (when the water level increases due to snow or rain). A river’s regime is the overall average value of its flows. A river’s mouth, that is the point where it enters the sea or the ocean, can be a delta or an estuary. A delta is formed by debris and sands that a river carries to its mouth. The debris prevent the river from flowing directly into the sea, creating ramifications that take the shape of the Greek letter delta. Generally deltas are formed when the sea is shallow. Rivers with delta mouths include the Mississippi, the Nile, the Danube, and the Po (Fig. 8). Conversely, an estuary is formed when river banks widen in the shape of a funnel and the sea is able to wipe out the sediments carried by the river. Some examples of estuaries include the Thames and the Seine. Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 18 di 26 Pegaso International The Atmosphere and the Hydrosphere Fig. 7: Po River drainage basin Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 19 di 26 Pegaso International The Atmosphere and the Hydrosphere Fig. 8: Po delta 5.4. Lakes Lakes, or lake basins, are large masses of freshwater that collect in land cavities. They are deeper than ponds. Swamps or marshes are depressions covered by shallow water and thick vegetation. Lakes are fed by precipitations or by streams, called inflows. Part of their water evaporates or flows out through rivers called outflows. Lakes have various origins: large alpine lakes are formed by glacial deposits obstructing a valley. Oval-shaped lakes generally have a volcanic origin. Lakes that are formed by tectonic processes are called tectonic lakes. Lakes are very important for human life, as they make travelling easier, and mitigate the climate of surrounding areas. Lake waters are used for irrigation and for tourism (Fig. 9). Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 20 di 26 Pegaso International 5.5. The Atmosphere and the Hydrosphere Glaciers Masses of snow accumulating on mountains form different types of glaciers. Large ice caps in Greenland and Antarctica are thick and extend to the coast, where large ice blocks break off, forming icebergs. Piedmont glaciers are formed by multiple ice caps. The most common type of glaciers are alpine or valley glaciers, which originate in a concavity in the rock and descend to the valley with a long ice tongue. Glaciers move at a certain rate based on their size and on temperature variation (Fig. 10). Fig. 9: Lake Sartirana in Lombardy Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 21 di 26 Pegaso International The Atmosphere and the Hydrosphere Fig. 10: The Brenva Glacier near Courmayeur Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 22 di 26 Pegaso International The Atmosphere and the Hydrosphere 6 Air and Water Pollution The term pollution denotes the contamination of the natural environment through substances that alter its chemical and physical composition. Air pollution consists of the contamination of air with substances that may have negative effects on human beings, animals, and vegetation. Pollutants can be divided into two types: anthropogenic, i.e. produced by man, and natural. Natural substances can be further divided into primary, i.e. naturally occurring in the environment, and secondary, as the result of chemical and physical reactions. The main causes of anthropogenic pollution are motor vehicles, factories, thermal power stations, fuel-powered central heating systems, and waste incineration (Fig. 11). Regarding the formation of secondary pollutants, reactions between nitrogen oxide and hydrocarbons in the presence of sunlight are particularly toxic. The product of these reactions is smog4, and is one of the worst forms of pollution. Nitrogen oxides are responsible for the decline in the volume of ozone that envelops out planet and protects it from ultraviolet radiation, which is dangerous for living creatures. This decline causes the so-called ozone hole. Furthermore, air pollutants fall back on Earth through rainwater and give rise to acid rains. Water pollution is the alteration of water-based ecosystem, and can originate from natural or anthropogenic causes. Natural pollution is caused by landslides, floods, or atmospheric and seasonal events. However, natural pollution does not cause particular damages, as water is able to purify itself. Anthropogenic causes include industrial and agricultural waste, and wastewaters being poured into seas or rivers. Industrial or agricultural processes release highly toxic, non4 The term smog connotes the dramatic reduction in visibility that derives from these chemical processes. Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 23 di 26 Pegaso International The Atmosphere and the Hydrosphere biodegradable substances into waters, such as colorants, acids, dyes, foams, metal powders, or chemical fertilizers. In these cases, water is unable to purify itself. Air and water pollution also contaminates vegetation, and therefore affects the entire Earth system. Fig. 11: An example of industrial pollution Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 24 di 26 Pegaso International The Atmosphere and the Hydrosphere Bibliography G. Bologna, Stato del pianeta e sostenibilità. Rapporto annuale. Edizione Ambiente, Milan, 1999. G. De Vecchis, Appunti di Geografia Generale, Kappa, Rome, 2001. L.B. Leopold, L’acqua. Introduzione all’idrologia, Zanichelli, Bologna, 1978. E. Lupia Palmieri, M. Parotto, Il globo terrestre e la sua evoluzione, Zanichelli, Bologna, 2003. T. L. McKnight, D. Hess, Geografia fisica, Piccin, Perugia, 2006. B. Nice, Geografia, De Agostini, Novara, 1980. M. Pinna, Le variazioni del clima. Dall’ultima grande glaciazione alle prospettive per il XXI secolo, Franco Angeli, Milan, 1996. Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 25 di 26 Pegaso International The Atmosphere and the Hydrosphere Please note: This material is intended solely for the personal use of students and is protected by copyright laws. Total or partial reproduction or reuse is strictly forbidden under Italian Copyright Law (Law No. 633 of April 22, 1941). 26 di 26
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