Atmospheric Variables

The control of atmospheric corrosion is due to the formation of films comprising basic salts, notably carbonate (Tables 2.16 and 2.17). The most widely accepted formula is 3Zn(OH)2 2ZnC03, which may be written Zn5(0H)6(C03)2- Environmental conditions that interfere with the formation of such films, or conditions that lead to the formation of soluble films, may cause quite rapid attack on zinc. One most important factor affecting the corrosion of zinc in the atmosphere is the duration and frequency of moisture contact. 

The rate of drying is an important factor because a thin film of moisture with high oxygen concentration promotes reaction. For normal exposure conditions, the films dry quite rapidly, and it is only in sheltered areas that drying times are so slow that the attack of zinc is accelerated significantly. Stiles and Edney (1989) have studied thin acidified films of water to show a steady rate of dissolution of zinc until the acidity is destroyed. 

The effect of atmospheric humidity on the corrosion of zinc is related to the conditions that may cause condensation of moisture on the metal surface and to the frequency and duration of the moisture contact. If the air temperature drops below the dew point, moisture will be deposited. The thickness of zinc, its surface roughness, and its cleanliness also influence the amount of dew deposited. Lowering the temperature of a metal surface below the air temperature in a humid atmosphere will cause moisture to condense on the metal. If the water evaporates quickly, corrosion usually is not severe and a protective film is formed on the surface. If water from rain or snow remains in contact with zinc when access to air is restricted and the humidity is high, the resulting corrosion can appear to be severe (wet storage stain, popularly known as white rust ), since the formation of a protective basic zinc carbonate is prevented. 

It is believed that the corrosion products that form when items are exposed to acid rain are more hygroscopic than those formed under more neutral conditions. This, say Haynie et al. (1990), effectively lowers the critical relative humidity from 90% to 75%, although this value is higher than the critical relative humidity for steel corrosion. The effects have been demonstrated both in the laboratory and by examples of corrosion occurring 

Test site Code Zinc corrosion, I-year results ( im) Steel/zinc ratio (mean) (1-year results)  

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The fundamental aspects of the problem are well established the measured concentrations of the CFCs indicate that they accumulate in the lower atmosphere and that they reach the stratosphere. As expected, chlorine atoms and CIO radicals are found in the stratosphere together with other species such as O, OH, HO2, NO, NO2, HCl, CIONO2, HOCl, etc. The observed concentrations are in reasonable agreement with the model predictions if the limitations of the models, as well as atmospheric variability, are taken into account. 

Laidlaw Filippelli (2008), Laidlaw et al. (2005), and Filippelli et al. (2005) have demonstrated that seasonal variations in children s blood lead levels In Syracuse, Indianapolis and New Orleans could be predicted using soil moisture and atmospheric variables suggesting that resuspension of urban soils contaminated by past use of leaded gasoline and paint were causally related to seasonal variations in blood lead. These papers concluded that urban lead contaminated soil was being re-suspended when soils were dry in the summer and autumn when... 

Aydin M, Saltzman ES, De Bruyn WJ, Montzka SA, Butler JH, Battle M (2004) Atmospheric Variability of Methyl Chloride During the Last 300 Years from an Antarctic Ice Core and Fim Air. Geophys Res Lett 31 L02109... 

In recent years it has been recognized that dynamic factors contribute much to observed temperature trends. For instance, in 1995 a marked similarity was observed between the spatial distributions of the SAT field and NAM fluctuations for the last 30 years, with a clear increase in the NAM index. The increasing trend of the index was accompanied by mild winters, changes in the spatial distribution of precipitation in Europe, and ozone layer depletion in the latitudinal belt >40°N. Similar data are available for the Southern Hemisphere. The main conclusion is that along with the ENSO event, both NAM and SAM are the leading factors in global atmospheric variability. In this connection, attention should be focused on the problem of the 30-year trend of NAM toward its increase, the more so that after 1995 the index lowered. It is still not clear whether this trend is a part of long-term oscillations. 

Govindan R.B. Vyushin D. Bunde A. Brenner S. Havlin S. and Schellnhuber H.J. (2002). Global climate models violate scaling of the observed atmospheric variability. Physical Review Letters, 89(2), art. no. 028501. 

Nicolis C. and Nicolis G. (1995). From short-scale atmospheric variability to global climate dynamics Toward a systematic theory of averaging. J. of Atm. Sci., 52(11), 1903-1913. Nielsen T.T. (1999). Characterization of lire regimes in the Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO) study area. J. Geophys. Res., 104(D23),... 

Yamagata T. Behera S.K. Luo J.J. Masson S. Jury M.R. and Rao S.A. (2004). Coupled Ocean-Atmosphere variability in the tropical Indian Ocean. In C. Wang, X.-P. Xie, and J.A. Carton (eds), Earth Climate The Ocean-Atmosphere Interactions. Springer-Verlag, Berlin, pp. 189-212. 

Kraner, A.W., Schroeder, G.L. Evans, R.D. (1964) Measurements of the effects of atmospheric variables on radon-222 flux and soil gas concentrations. In The Natural Radiation Environment, ed. J. A.S. Adams W.M. Lowder, University of Chicago Press, pp. 191-215. 

PRINCIPLES OF METEOROLOGICAL ANALYSIS, Walter J. Saucier. Highly respected, abundantly illustrated classic reviews atmospheric variables, hydrostatics, static stability, various analyses (scalar, cross-section, isobaric, isentropic, more). For intermediate meteorology students. 454pp. 6X 9X. 65979-8 Pa. 12.95... 

The atmospheric variability has also been examined in previous studies. Solomon et al. [32] examined intrasampler variance and found small but consistent differences between the recoveries of four adjacent rotorod samplers and also between the recoveries of three adjacent rotoslide samplers. Although the authors suggested that the intrasampler variance reflected minor differences in... 

The critical need to achieve high signal-to-noise ratios for spatially resolved measurement of several free radicals has spawned a number of research efforts aimed at improving our ability to observe such radicals as OH, HO2, NO, NO2, etc., with orders of magnitude better sensitivity than was previously available. A major impetus behind this research has been the realization that atmospheric variability on the spatial scale of a hundred meters in the vertical drives fluctuations in several of the key reactiye species, which provide ample concentration variation to carry out covariance studies to establish cause and effect within subsets of free radical reaction sets. 

Offermann, D., K.-U. Grossman, P. Varthol, P. Knieling, M. Riese, and R. Tank, Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) experiment and middle atmosphere variability. J Geophys Res 104, 16,311, 1999. 

Wiedemann (143) determined the titanium content of a nonstoichiometric titanium carbide by a multistep, variable atmosphere, variable temperature program, TG method. The sample was first heated in a chlorine atmosphere to 975°C. This converted the titanium to volatile titanium chloride, leaving a residue of carbon in the sample container. The amount of carbon residue was then determined by heating from 475-600°C in an air atmosphere, resulting in the oxidation of carbon to carbon dioxide. These processes are illustrated in the TG curve in Figure 4.34. 

The correlations for ay and az in the previous subsection require knowledge of atmospheric variables that may not be available. In that case, one needs correlations for a, and Pasquill stability categories A through F introduced in Chapter 16 provide a basis for such correlations. 

Dunbar RB and Gole JE (1993) Coral records of ocean-atmosphere variability. NOAA Climate and Global Change Program Special Report No. 10, Boulder, CO UCAR. 

The evaluation and classification of atmospheric metal corrosivity help develop corrosion protection strategies and optimize material service Hfe. Two fundamental approaches are used to estimate the relationships between atmospheric corrosion rates of metals and the atmospheric variables such as pollutants types and their concentration in the atmosphere, the temperature, and the time of wetness. 

One would generally prefer to operate in a fast scan mode without a chopper, as it allows monitoring of the source variability, atmospheric variability and noise spikes, and also faster operation. However, depending on the detector time of response. 

There is an enormous range of scales in atmospheric motion, as indicated in Fig. 1. For many subjects the detailed description of the small-scale turbulent motions is not required. In addition, the randottmess of atmospheric turbulence makes a deterministic description difficult. As such, there is a need to separate the small scales of atmospheric mrbulence from mean motions on the larger scales. Let C denote an atmospheric variable, such as specific humidity. Then C represents a mean or smoothed value of C, typically taken on a horizontal scale of order 10 km or a time scale in the order of 30 min to 1 h. A local or instantaneous value of C would differ from C. Thus, we have... 

Atmospheric mesoscale models are based on a set of conservation equations for velocity, heat, density, water, and other trace atmospheric gases and aerosols. The equation of state used in these equations is the ideal law. The conservation-of-velocity equation is derived from Newton s second law of motion (F = ma) as applied to the rotating earth. The conservation-of-heat equation is derived from the first law of thermodynamics. The remaining conservation equations are written as a change in an atmospheric variable (e.g., water) in a Lagrangian framework where sources and sinks are identified. 

The concept of zonal mean, or zonal average, is especially useful for describing the meteorology of the stratosphere, so a brief definition is in order The zonal mean of an atmospheric variable, is the average taken in the east-west (longitudinal) direction. Denoting longitude by X, the zonal mean T is defined as... 

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