Atmospheric Simulations

We have investigated the atmospheric implications ot our newly calculated absorption cross sections with the Garcia-Solomon 2D dynamical/chemical model [85,86], to which we have added sultur chemistry and aerosol microphysics [87]. The model spans 56 pressure levels trom 2 to 112 km above sea level, and 36 latitudes trom 89.5°S to 89.5°N. Further details ot the sultur chemistry and 

FIGURE 8.3 Calculated and observed SO2 mixing ratios for the April-May period between 26°N to 32°N latitude. 2D model calculations incorporate our calculated vibrational transitions in the visible region and three values for the Lyman-a cross section no Lyman-a cross section (solid), the Lyman-a cross section of 6.4 x 10 cm molecule (dot dash) and Lyman-a cross section of 6.3 x 10 cm molecule (dashed). Observations from Spacelab 3 (circles with horizontal lines) from 1985 [12]. 

The previously calculated vibrational transitions for H2SO4 are similar to the ones we calculate here and as expected there is very little change in the simulated 

We have shown that modern theoretical methods are capable of calculating cross sections for sulfuric acid purely ab initio. This includes vibrational transitions, low lying electronic transitions and transitions to high energy Rydberg states. The results obtained are of an accuracy that is suitable as input parameters for atmospheric modeling of the photolysis of sulfuric acid. 

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Explicit mechanisms attempt to include all nonmethane hydrocarbons believed present in the system with an explicit representation of their known chemical reactions. Atmospheric simulation experiments with controlled NMHC concentrations can be used to develop explicit mechanisms. Examples of these are Leone and Seinfeld (164), Hough (165) and Atkinson et al (169). Rate constants for homogeneous (gas-phase) reactions and photolytic processes are fairly well established for many NMHC. Most of the lower alkanes and alkenes have been extensively studied, and the reactions of the higher family members, although little studied, should be comparable to the lower members of the family. Terpenes and aromatic hydrocarbons, on the other hand, are still inadequately understood, in spite of considerable experimental effort. Parameterization of NMHC chemistry results when NMHC s known to be present in the atmosphere are not explicitly incorporated into the mechanism, but rather are assigned to augment the concentration of NMHC s of similar chemical nature which the... 

Early works were typically carried out using single atmosphere exposure conditions, either air (or moist air) representing the cathode side environment [124-129, 139, 142,144-162] or a reducing atmosphere simulating the anode side environment [124, 125, 127-129, 144, 145], Lately, studies have been also performed to determine the oxidation/corrosion behavior of metal and alloys under dual-atmosphere exposure conditions that closely simulate the interconnect exposure conditions during SOFC operation [154-159], The alloys studied include both Fe-Cr base FSSs and Ni or Ni-Cr base heat-resistant alloys, as well as Cr or Cr base alloys. 

A major difficulty of the physico-chemical studies is to link the observations in the atmosphere and the kinetic data determined in the laboratory (elementary reaction kinetics and atmospheric simulation in smog chambers). The most amenable method of comparing field information with kinetic data is by means of the chemical residence time r, defined by the relationship ... 

Outdoor simulation chamber EUPHORE Solar UV/VIS Atmospheric simulation Brockmann et al. (1996)... 

In the present paper, we show that it is possible to calculate both vibrational and electronic transitions of H2SO4 with an accuracy that is useful in atmospheric simulations. We calculate the absorption cross sections from the infrared to the vacuum UV region. In Section 2 we describe the vibrational local mode model used to calculate OH-stretching and SOH-bending vibrational transitions as well as their combinations and overtones [42-44]. This model provides frequencies and intensities of the dominant vibrational transitions from the infrared to the visible region. In Section 3 we present vertical excitation energies and oscillator strengths of the electronic transitions calculated with coupled cluster response theory. These coupled cluster calculations provide us with an accurate estimate of the lowest... 

Our theoretical results in Sections 2 and 3 should provide a useful reference for absorption cross sections of H2SO4 in the region of interest to atmospheric modeling. The presented results show that it is possible to provide theoretical estimates that are of sufficient accuracy to alleviate the need to employ speculative cross sections in atmospheric simulations [10,12,13,18]. 

In perspective, integrated NWP-ACTM modelling may be a promising way for future atmospheric simulation systems leading to a new generation of models for improved meteorological, environmental and chemical weather forecasting. 

Collins WD, Rasch PJ, Boville BA, Hack JJ, McCaa JR, Williamson DL, Briegleb BP (2006a) The formulation and atmospheric simulation of the community atmosphere model, Version 3 (CAM3). J Climate 19 2144-2161... 

McGregor JL, Dix MR (2005) The conformal-cubic atmospheric model progress and plans. In Workshop on high resolution atmospheric simulations and cooperative output data analysis, Yokohama, Japan. JSPS hrtemational Meeting Series. JSPS and JAMSTEC, Yokohama, 2 p. Available http //www.es.jamstec.go.jp/esc/research/AtmOcn/hires2005/abstract/4-2 mcgregor. pdf... 

Perhaps the most tedious and mundane aspect in the development and validation of an atmospheric simulation model is the compilation of a complete contaminant emissions inventory. Yet, such an inventory must be made before a model can be validated since the spatial and temporal distribution of contaminant emissions comprises a direct input to the overall simulation model. Ground-level sources enter into the boundary conditions of the conservation equations through the function Qi y t) introduced previously elevated sources enter as Si x,y,z,t) in the conservation equations themselves. 

Xue, M K.K. Droegemeier, and Wong, V. (2000) The Advanced Regional Prediction System (ARPS) - A multiscale nonhydrostatic atmospheric simulation and prediction tool. Part I Model dynamics and verification, Meteor. Atmos. Physics. 75, 161-193. 

Brauers, T., B. Bohn, F.-J. Johnen, F. Rohrer, S. Rodriguez Bares, R. Tilhnann, and A. Wahner The atmosphere simulation chamber SAPHIR a tool for the investigation of photochemistry. Presented at the EGS -AGU - BUG Joint Assembly, Nice, France, April 11 (2003). See also http //www.fe-juelich.de/icg/icg-ii/saphir/home. 

Karl M., Th. Brauers, H.-P. Dom, F. Holland, M. Komenda, D. Poppe, F. Rohrer, L. Rupp, A. Schaub and A. Wahner, Kinetic study of the OH-isoprene and Os-isoprene reaction in the atmosphere simulation chamber, SAPHIR, Geophys. Res. Lett. 31 (2004), L05117, doi 10.1029/2003GL019189. 

It has been demonstrated that atmospheric simulation chambers offer the unique possibility for studying the impact of real car exhaust under almost real-world conditions on tropospheric photosmog formation. 

The book covers information for producing multicomponent test gas atmospheres including sorbent evaluation, methods development, dosimeter lasting, instrument calibration, atmospheric simulation, and gas analysis. 

FIGURE 4 The calculated change (%) in July surface sulfate concentrations between 1850 and 1990 atmospheres simulated by IMAGES using the IS92a emission scenario. 

Exfoliation is commonly experienced on exposure of susceptible aluminum alloys to marine atmospheres. Simulation in the laboratory is accomplished by controlled intermittent spray with 5% NaCl containing added acetic acid to pH 3 at 35-50°C (95-120°F) [28]. In practice, severe exfoliation corrosion has been experienced in water irrigation piping constructed of type 6061 alloy [29]. The cause in this instance was ascribed to pipe fabrication methods and presence of excess amounts of impurity elements (e.g., Fe, Cu, and Mn). 

Nine boimdary conditions of the 3D SMART model are relevant for the concerned sea-atmosphere simulation. The horizontal open boundary condition 0 = 3c/3n =o with n J. 5/2 defines the gradient at the boundary to be zero for both water and air. This suppresses dispersion but permits advection through the open boundary. The no-flux boundary condition 0 = uc — Ddcdn g assures that neither dispersive nor advective flux passes through a solid boundary. At the sea and air boundary layer, dispersion is replaced with the Henry coefficient equilibrium assumption c , = Cat/h. This requires that natural gas is simulated in both, sea and atmosphere. The vertical open boundary condition for the atmosphere extrapolates the vertical gradient to the other side of the... 

The time step is 0.4 seconds irtilizing a semi-implicit fluid flow guided matrix reordering solver. The seawater simulation has been calibrated with tidal and current measurements and wind data have been fed into the atmosphere simulation. Ideally the Henry coefficient shall be dependent on temperature and salinity fields supplied by the hydrodynamic computation. The numerical demonstrator shown in figure 3 shows the coupled simulation of tracer in sea and atmosphere. The differing plume travel-direction in sea (eastward) and atmosphere (southward) can be recognized. 

Laboratory studies to study the oxidation of isoprene imder carefully controlled conditions, in particular using atmospheric simulation chambers, in order to corrfirm the presence of reaction products and the rates of competing channels. 

Karl M, Dom H-P, Holland F, Koppmann R, Poppe D, Rupp L, Schaub A, Wahner A (2006) Product study of the reaction of OH radicals with isoprene in the atmosphere simulation chamber SAPHIR. J Atmos Chem 55 167-187... 

Rohrer, F., Bohn, B., Brauers, T., Britning, D., Johnen, F.-J., Wahner, A., Kleffmann, J. Characterisation of the photolytic HONO-source in the atmosphere simulation chamber SAPHIR. Atmos. Chem. Phys. 5, 2189-2201 (2005)... 

It is also possible to change the temperature during measurement and to pressurize and control the atmosphere simulating oxidizing or reducing conditions as in technical gasification systems [81]. 

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