The Definition of the Atmosphere
The atmosphere is the gaseous envelope of the planet that rotates together with it. The atmosphere is extremely valuable because it links the Earth and space and remains in the continuous interaction with all the earthly shells – the hydrosphere, the lithosphere, and the biosphere. The atmospheric gas is called air; thus, the atmosphere is figuratively called the air ocean. Its role in the life of the Earth is significant. Living organisms need it to breathe and to be protected from the impact of outer space. Without the atmosphere, the Earth would become a lifeless desert, like the surface of the Moon. The atmosphere is the center of oxygen concentration and weather formation, and it is a shield that saves the Earth from cosmic impacts.
The History of Doctrines about the Atmosphere
The study of the atmosphere began in ancient times when the main subject of study was the weather phenomenon. Meteorology has given rise to the development of the science that researched the atmosphere and weather. The word meteorology is the scientific anachronism that originated in the 4th century B.C.E., in the time of Aristotle, the author of the eponymous treatise on celestial phenomena. The term meteorology is based on the Greek expression that means objects in the air. According to Aristotle, these objects include showers, comets, hailstones, meteors, rainbows, and aurora. However, the philosopher singled out hydrometeors in a particular group. Stars were not included in meteorology because it was believed that they were fixed and unchangeable. Further, the study of the atmosphere was developed in the works of Theofrastus and Pytnagoras, who continued the tradition of the classical Greek science.
For over 2000 years, the air had been considered as the core element of the atmosphere, and only in the 17th century, the Flemish physician and chemist Van Helmont used the word gas in his scientific papers. Later, his research was continued by Scheele (who described the partial properties of oxygen in the book Chemische Abhandlung von der Luft und dem Feuer), Petty (who discovered nitrous air (nitric oxide, NO), alkaline air (ammonia, NH3), acid air (hydrochloric acid, HCl), and isolated carbon monoxide (CO), and others), Priestley (who discovered dephlogisticated air by heating mercuric oxide), Dalton (who developed a table of relative atomic weights of the six elements – hydrogen, oxygen, nitrogen, carbon, sulfur, and phosphorus), Cavendish and others (Michael, 2009). However, the key discoveries were made in the course of the scientific and technological revolution, when flights made it possible to study the atmosphere’s structure and properties in detail.
Atmospheric Vertical Structure
The troposphere is the closest layer of the atmosphere to the Earth. Its thickness varies with distance from the Equator. This layer extends up to 16-18 km above the Equator, to 10-12 km in temperate zones, and to 8-10 km at the poles. It contains 80% of the mass of air and 90% of steam’s mass (Elliot & Frierson, 2009). Clouds, cyclones, and anticyclones are formed in this layer. The temperature in it depends on the altitude. On average, it is reduced by 0.65° C per 100 meters. Further, the tropopause is the transition layer of the atmosphere. Its height varies from a few hundred meters to 1-2 km. The air temperature is higher in summer than in winter in it. For example, the temperature is – 65° C in winter over the poles, and it is – 70° C at any time of year over the Equator (Thorne et al., 2010).
Further, the stratosphere is the upper limit of the atmosphere, and it is located at an altitude of 50-55 km. Turbulence is low there, and the water vapor content in the air is negligible; however, it contains ozone. Its maximum concentration is at an altitude of 20-25 km. In the stratosphere, the temperature starts to rise and it reaches + 0.8° C due to the fact that ozone interacts with ultraviolet radiation (Liu & Weng, 2009). The stratopause is the lower and intermediate layer between the stratosphere and mesosphere.
The upper boundary of the mesosphere is 80-85 km. Here, complex photochemical processes involving free radicals take place. They provide the gentle blue glow of the planet that is visible from space. The majority of comets and meteorites that enter the Earth’s atmosphere are burned in the mesosphere. Next comes the mesopause; the temperature in this interlayer constitutes at least – 90° C (Meriwether & Gerrard, 2004).
The upper measure of the thermosphere is located approximately at the height of 800 km. The air temperature increases there and it can be over + 1000° C (Elliot & Frierson, 2009). During the day, the temperature fluctuations range in the hundreds of degrees. However, the air is so rarefied that the usual understanding of the term temperature is not appropriate here.
Further, the ionosphere combines the mesosphere, thermosphere, and mesopause. The air here is composed mainly of oxygen and nitrogen molecules and quasi-neutral plasma. Entering the ionosphere, sunlight strongly ionizes air molecules. The level of ionization is directly proportional to the height; thus, at the height of 90 km the degree of ionization is lower than at 100-110 km, where electrons are concentrated (Schlatter, 2009). It promotes the short and medium radio waves reflection. The most important part of the ionosphere is the upper one, which is located at an altitude of 150-400 km. It reflects radio waves and facilitates the transfer of radio signals over long distances. The aurora phenomenon also occurs in the ionosphere.
Atmospheric air consists of a mechanical mixture of gases, water vapor, and impurities. The average air composition is the following in the first 100 km of the atmosphere: 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.03% carbon dioxide, and only 0.01% for all other gases (hydrogen, helium, water vapor, and ozone) (Shakhashiri, 2007). Gases that comprise the air are perpetually mixing; thus, the percentage of gases is fairly constant, except for the case of carbon dioxide. The combustion of oil, gas, and coal and the reduction of the amount of forests increase the amount of carbon dioxide in the atmosphere. It contributes to the increase in the temperature on the Earth because it absorbs and re-emits the solar energy and delays the Earth’s heat radiation.
Further, the atmosphere composition includes ozone, a special kind of gas that performs vital functions. The concentration of ozone in the atmosphere is quite small: up to one-thousandth of a percent of the atmosphere’s total volume (0.001%). The ozone layer (ozonosphere) is an area of ??the Earth where an active formation of ozone occurs. The ozonosphere starts at 10-12 km from the planet surface and extends up to the height of 50-55 km; the greatest concentration of ozone is at an altitude of 19-23 km (Sivasakthivel & Siva Kumar Reddy, 2011). At an altitude of 25-35 km, the concentration of this gas is identified as the ozone shield (ozone layer). In the stratosphere, it performs a vital function of protecting the surface of the Earth by delaying the ultraviolet radiation of the Sun (NASA, 2006).
Today, there is a global problem of the ozone layer destruction. It collapses because of industrial development and air pollution by exhaust gases. The complete disappearance of the ozone layer would mean the termination of the higher forms of life on the Earth. Even the thinning of this layer leads to an increase in the number of cancer diseases, causes deaths of unicellular organisms that belong to different ecosystems, influences the genetic code of living organisms, and increases the number of mutations. In 1987, the United States and 30 other countries signed the Montreal Protocol to phase out the production and use of the ozone depleting substances (ODS); in September 2009, the Protocol became the first international agreement which was supported by 196 parties (EPA, 2009).
The Interaction of the Atmosphere with the Hydrosphere and the Lithosphere
The interaction between the atmosphere, the hydrosphere, and the lithosphere forms a thermodynamic system characterized by a continuous exchange of heat and moisture. The world ocean is an active absorber of carbon dioxide contained in the air, and, at the same time, it is the habitat of algae that contribute to the supply of atmospheric oxygen. Thus, the ocean maintains a constant composition of the air. These relationships are significant and multifaceted because the atmosphere and the ocean are now considered as a single complex interacting system. Moreover, this relationship is genetic because the evolution of the atmosphere and hydrosphere is a single process.
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In addition, the atmosphere is closely linked with the lithosphere in its development. Due to geological and geochemical processes, it has been receiving to receive a significant portion of gases from the earth. At the same time, the atmosphere always influences the lithosphere by the powerful physical and chemical weathering. Oxygen and other gases, together with various exogenous relief formation factors, such as fluctuations in temperature, winds (breezes, trade winds, monsoons, cyclones and anticyclones), and precipitation, substantially modify rocks and the whole surface of the Earth. Thus, the atmosphere is part of a single planetary set.
The Problems and the Effects of the Atmosphere Pollution
The problem of air pollution is one of the greatest global challenges mankind faces. The toxic substances present in the air not only make it harmful to living organisms but also cause serious climate changes.
Due to human activities, the concentration of carbon dioxide has increased by almost 30% over the past 200 years (World Nuclear Association, 2014). Nevertheless, people continue to burn fossil fuels and to destroy forests. These activities lead to colossal global environmental problems. In addition, fuel combustion in thermal power plants is accompanied by the emission of sulfur dioxide. Incomplete combustion causes carbon monoxide release in the air. Moreover, such particulate pollutants as soot and dust are also produced by mechanisms and human activity. The atmosphere can be protected not only by domestic and international efforts but due to the attempts of each individual to use cleaner fuels, promote alternative energy sources, practice proper waste disposal, etc.
The atmosphere is the gaseous envelope that surrounds the Earth. The presence of the atmosphere is one of the most important conditions for life on the planet. It consists of multiple layers that differ by their characteristics and play a significant role in the protection of the planet from cosmic impacts. The gas composition of the atmosphere includes such special gases as oxygen, which is required for respiration, and ozone, which protects the planet from solar radiation. The atmosphere is closely connected to the hydrosphere and the lithosphere. It contributes to the formation of the planet’s climate and topography. The atmosphere is subjected to a constant pollution due to the industrial development and human activities. This issue requires constant monitoring to prevent the depletion of the ozone shield and global climate changes.