Atmospheric simulation models

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. 

Atmospheric emissions of sulphur dioxide are either measured or estimated at their source and are thus calculated on a provincial or state basis for both Canada and the United States (Figure 2). While much research and debate continues, computer-based simulation models can use this emission information to provide reasonable estimates of how sulphur dioxide and sulphate (the final oxidized form of sulphur dioxide) are transported, transformed, and deposited via atmospheric air masses to selected regions. Such "source-receptor" models are of varying complexity but all are evaluated on their ability to reproduce the measured pattern of sulphate deposition over a network of acid rain monitoring stations across United States and Canada. In a joint effort of the U.S. Environmental Protection Agency and the Canadian Atmospheric Environment Service, eleven linear-chemistry atmospheric models of sulphur deposition were evaluated using data from 1980. It was found that on an annual basis, all but three models were able to simulate the observed deposition patterns within the uncertainty limits of the observations (22). 

The comparison of model results with observations reveals significant discrepancies, especially in the Arctic, where concentrations are overestimated by the model in ocean and atmosphere. The model does not reproduce the observed latitudinal gradient of DDT in the ocean, i.e. the modelled and observed gradients have a different sign. Observations show, that the contamination of the ocean by DDT is decreasing towards the Arctic, whereas in the model simulation contaminations are increasing. 

Another theoretical frontier involves the study of the vibrational spectroscopy of water at other conditions, or in other phases. Here it will be crucially important to use more robust water models, since many effective two-body simulation models were parameterized to give agreement with experiment at one state point room temperature and one atmosphere pressure. We have already seen that using these models at higher or lower temperatures even for liquid water leads to discrepancies. We note that a significant amount of important theoretical work on ice has already been published by Buch and others [71, 72, 111, 175, 176]. 

Dan L. Ji J. and Li Y. (2005). Climatic and biological simulations in a two-way coupled atmosphere-biosphere model (CABM). Global and Planetary Change, 47(2-4), 153-169. Dansgaard W. Johnsen S.J. Clausen H.B. Dahl-Jensen D. Gundestrup N.S. Hammer C.U. Hvidberg C.S. Steffensen J.P. Sveinbjornsdottir A.E. Jouzel J. and Bond G. (1993). Evidence for general instability of past climate from a 250-kyr ice-core record. Nature, 364, 218-220. 

Johnson C.E. Stevenson D.S. Collins W.J. and Derwent R.G. (2002). Interannual variability in methane growth rate simulated with a coupled Ocean-Atmosphere-Chemistry model. Geophysical Research Letters, 29(19), 1-4. 

Soil-Vegetation-Atmosphere Transfer Schemes (SVATs) simulated models that use parameters such as vegetation cover, soil texture, water-holding capacity of soils, surface roughness, and albedo, to make predictions on soil moisture, runoff, evapotranspiration, and runoff. 

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... 

Transport and dispersion was evaluated without any form of tuning by comparing a simulation of the ETEX-1 release to the official measurements of surface concentration. To facilitate comparisons with models evaluated during ATMES 11 (Atmospheric Transport Model Evaluation Study) an identical statistical methodology was employed (Mosca et al. 1998). Background values were subtracted so that only the pure tracer concentration was used. Measurements of zero concentration (concentrations below the background level) were included in time series to the extent that they lay between two non-zero measurements or within two before or two after a non-zero measurement. Hereby, spurious correlations between predicted and measured zero-values far away from the plume track are reduced. 

To evaluate the deposition routines a simulation of the Chernobyl accident was carried out and compared to measurements of total deposited Cesium 137 (Cs-137). The measurements were extracted from the Radioactivity Environmental Monitoring database at the Joint Research Centre, Ispra, Italy (http //rem.jrc.cec.eu.int/). The comparison date was chosen to be 1 May 1986 at 12 00 UTC, since at this time the greatest number of measurements was available. Statistical measures were calculated following the recommendations of the Atmospheric Transport Model Evaluation Study (ATMES) final report (Klug et al. 1992). 

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... 

Several types of models are commonly used to describe the dispersion of atmospheric contaminants. Among these are the box, plume, and puff models. None are suitable, however, for describing the coupled transport and reaction phenomena that characterize atmospheres in which chemical reaction processes are important. Simulation models that have been proposed for the prediction of concentrations of photochemically formed pollutants in an urban airshed are reviewed here. The development of a generalized kinetic mechanism for photochemical smog suitable for inclusion in an urban airshed model, the treatment of emissions from automobiles, aircraft, power plants, and distributed sources, and the treatment of temporal and spatial variations of primary meteorological parameters are also discussed. 

General Considerations. The nature and characteristics of atmospheric contaminants suggest certain diflBculties in the formulation of a kinetic mechanism of general validity. First, there is a multiplicity of stable chemical species in the atmosphere. Most species are present at low concentrations, thereby creating major problems in detection and analysis. A number of atmospheric constituents probably remain unidentified. Also, there are a large number of short-lived intermediate species and free radicals which participate in many individual chemical reactions. However, while we must admit to only a partial understanding of atmospheric reaction processes, it remains essential that we attempt to formulate quantitative descriptions of these processes which are suitable for inclusion in an overall simulation model. 

In consequence, the evidence from this paper requires at least a doubling of the source quantity of methane, or of the input into atmospheric balance calculations, respectively. A third source, which is bacterially generated methane, may deliver high quantities over short geologic time. This is not included here. With higher input quantities, however, the poor stability of the simulation models would possibly disappear, and a definite determination of reactants cycling velocities and subsequently a convergent prediction of climatic evolution should be possible. 

Coen, J.L., and Clark, T.L. (2001) Coupled Atmosphere-fire Model Simulations in Various Fuel Types in Complex Terrain, 4th Symposium on Fire and Forest,... 

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