Nature of the Atmosphere

Many of the physical characteristics of the atmosphere, such as wind, temperature, cloud cover, humidity, and precipitation, are easily perceived. Sometimes, chemicals in the atmosphere also can be observed, as in smoke plumes and smog, and their physical transport tracked downwind just as downstream transport of substances in a river can be measured. Other atmospheric processes are less apparent to the unaided observer, however, occurring either on the microscopic scale of a chemical reaction, or on a global scale, or at high altitudes. Such processes may be detected only by instrumentation on satellites or some high-altitude aircraft. 

The advent of aviation provided both the means and a greater incentive to investigate the atmosphere. Physical phenomena, such as winds, turbulence, 

Clouds occur frequently in the troposphere, and from an airborne vantage point it is evident that clouds are not randomly scattered in the vertical direction. Usually, clouds have bases at relatively well-defined altitudes, because rising air containing water vapor (moisture) systematically becomes cooler with height, eventually reaching its dew point, the temperature at which water vapor condenses (Section 4.2.2). Water in both liquid and solid phases in the clouds facilitates a host of chemical reactions. 

FIGURE 4-1 Vertical structure of the atmosphere. Weather phenomena are confined almost entirely to the troposphere, as are most air pollutants, which are removed by various processes before they can mix into the stratosphere. Certain long-lived pollutants, however, such as the chlorofluorocarbons (CFCs), do mix into the stratosphere, and other pollutants can be injected physically to stratospheric altitudes by processes such as volcanic eruptions or nuclear explosions. Note that more than one term may refer to a given layer of the atmosphere (adapted from Introduction to Meteorology, by F. W. Cole. Copyright 1970, John Wiley Sons, Inc. Reprinted by permission of John Wiley Sons, Inc.). 

As the plane continues to climb, the ride becomes smooth. Coffee served in open cups does not spill, providing testimony that in the tropopause [at approximately 10,000 m (33,000 ft)] and the still higher stratosphere (Fig. 4-1), the size and energy of atmospheric eddies decrease. Weather phenomena are confined almost entirely to the troposphere. Being at the edge of the stratosphere is comparable to being in the thermocline of a stratified lake (Section 2.2.2) turbulent diffusion is suppressed, and vertical Fickian transport is slowed. Chemicals released into the air near Earth s surface may mix 

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This important fact was first demonstrated by Vernon in a series of classical experiments, some of which are summarised graphically in Fig. 3.1. He showed that rusting is minimal in pure air of less than 100 l o relative humidity but that in the presence of minute concentrations of impurities, such as sulphur dioxide, serious rusting can occur without visible precipitation of moisture once the relative humidity of the air rises above a critical and comparatively low value. This value depends to some extent upon the nature of the atmospheric pollution, but, when sulphur dioxide is present, it is in the region of 70-80%. Below the critical humidity, rusting is inappreciable, even in polluted air. 

Taking into account the electrochemical nature of the atmospheric corrosion process it is absolutely necessary to use the concept of Time of Wetness (TOW). It is a concept commonly used in atmospheric corrosion of metallic materials and refers to the time when the metal is sufficiently wet for corrosion reaction to occur, that is, when an electrolyte is present in the metallic surface. Under the particular characteristics of atmospheric corrosion there are time periods where corrosion could not occur due to the absence of an electrolyte in the metallic surface. The lowest outdoor TOW values are observed in the desert regions, as also in the Antarctic and Arctic regions. Atmospheric corrosion rates of metals at these climatic conditions are also very low and in the case of cold regions, the increase of temperature leads to the increase of TOW and corrosion rate [11], In principle, TOW is a parameter that depends upon both the climatic conditions and in the characteristics of the metallic surface. 

Under indoor conditions, in the same way than outdoors, it is necessary the presence of surface humidity for corrosion to occur due to the electrochemical nature of the atmospheric corrosion process however, in indoor conditions there are no precipitations and the presence of surface water depends mainly on water content in the air and changes in temperature on the surface, as well as the presence of hygroscopic substances on the metallic surface. 

Temperature is the main factor that affects sintering and solid-state transformation experimental observations, however, have shown that the nature of the atmosphere in which the catalyst is heated may also play a part to an extent in the sintering process. For example, the presence of water vapor accelerates crystallization and structure modifications in oxide supports (Forzatti and Lietti, 1999). 

OXYGEN PRESENT IN THE AIR—NATURE OF THE ATMOSPHERE—ITS PROPERTIES—OTHER PRODUCTS FROM THE CANDLE—CARBONIC ACID—ITS PROPERTIES. 

XT TE have now seen that we can produce hydrogen and oxygen from the water that we obtained from the candle. Hydrogen, you know, comes from the candle, and oxygen, you believe, comes from the air. But then you have a right to ask me, How is it that the air and the oxygen do not equally well burn the candle If you remember what happened when I put a jar of oxygen over a piece of candle, you recollect there was a very different kind of combustion to that which took place in the air. Now, why is this It is a very important question, and one I shall endeavour to make you understand it relates most intimately to the nature of the atmosphere, and is most important to us. 

OXYGEN PRESENT IN THE AIR-NATURE OF THE ATMOSPHERE-ITS PROPERTIES-OTHER PRODUCTS FROM THE CANDLE-CARBONIC ACID-ITS PROPERTIES. 

Anpo and coworkers (Anpo, 2004 Anpo and Che, 1999) investigated the PL behavior of Ti02 photocatalysts in the presence of various kinds of reactants. The dependence of the PL intensity on the nature of the atmosphere was explained in terms of surface band bending of Ti02 particles, its extent depending on the electronegativity or electroaffinity of the reactant molecules. Furthermore, such an effect on the PL intensity was found to be reversible after elimination of the reactant molecules by... 

Pay, Trans. Faraday Boo., 1911, 7, 136. F6ry and Cheneveau (Oompt. rend., 1909, 148, 401) suggest that the melting-point of the metal, like that of silver, is influeneHi by the nature of the atmosphere in which fusion takes plaoe, hut Waidner and Burgess (ibid., p. 1177) do not accept the explanation. 

In the specific case of emissions of sulphur dioxide and oxides of nitrogen, the change in oxidizing nature of the atmosphere subsequent to chemical reactions in the atmosphere, and upon deposition, results in changes in the acid base and redox equilibria in the aqueous phases. 

Atmosphere The nature of the atmosphere surrounding the sample is important in relation to the transfer of heat and the chemistry of the sample reaction. Common sample atmospheres are shown in Table 36.1. In addition, the flow rate of the gas is important a static system will not remove reaction products from the sample. 

Another example of epoxy-polysulphide coating application is for the Indian Molasses Co. Ltd tank farm facilities in Mangalore where the nature of the atmosphere is highly corrosive. Several tanks have been coated (Figure 10.8) (Morton International, undated d). 

The relatively soft nature of the atmospheric pressure LC/MS methods is obvious from the spectra shown in Figs. 9, 10, and 12. To generate fragmentation, it is... 

Copolymers of styrene with acetophenone oxime acrylate were produced using benzophenone as a sensitiser . The total number of amino groups was found to be unaffected by the nature of the atmosphere. Organic dyes have been found to sensitise the photopolymerisation of a polyimide using the tetra-t-butylperester... 

Lecture V Oxygen Present in The Air - Nature of The Atmosphere - Carbonic Acid... 

This brief discussion serves to highlight the complex, interrelated nature of changes in atmospheric trace species on overall atmospheric properties. One might not have expected, for example, that increases in CO. would have impacts on strato.spheric ozone or that increases in CH4, a trace gas largely consumed in the troposphere, would also exert an effect on stratospheric ozone. We return to the highly coupled nature of the atmospheric chemistry-climate system in Chapter 21. 

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