Air Pollution Modeling and Its Application XII

Inhaltsverzeichnis

1. Frontmatter

2. Integrated Regional Modelling

   1. Frontmatter

   2. Modeling of a Saharan Dust Event

      G. Cautenet, F. Guillard, B. Marticorena, G. Bergametti, F. Dulac, J. Edy

      Abstract

      We have coupled a nonhydrostatic mesoscale model with a simple but comprehensive mineral aerosol source scheme, along with a spectral sedimentation scheme. We present a simulation of a Saharan dust transport event (4 days), including mass uptake estimates, 3D transport and dry deposition. The model is initialized with ECMWF data. Meteosat imagery is used to check the dust cloud uptake and trajectory.

   3. Temporal and Spatial Scales for Transport and Transformation Processes in the Eastern Mediterranean

      G. Kallos, V. Kotroni, K. Lagouvardos, A. Papadopoulos, M. Varinou, O. Kakaliagou, M. Luria, M. Peleg, A. Wanger, M. Uliasz

      Abstract

      In several studies during the past, the urban plumes have been extensively considered. In these studies, the spatial and temporal scales of episodic conditions have been described and emphasis was given to the formation and evolution of air pollution episodes within city limits (or in an area covering a few tens of kilometers around the city) and for a time period of one to two days. Moreover, the weather phenomena exhibiting strong diurnal variations (e. g. sea/land-breezes, upslope/downslope and drainage flows, orographic effects, heat islands etc.) were emphasized. The influence of the regional scale phenomena in such cases was not considered on a systematic manner. Actually, the role of phenomena with wavelengths larger than a few tens of kilometers was considered as not important for the formation of a specific air quality over the city of consideration. During the last few years, the influence of regional scale forcing on the formation of specific air quality conditions was found to be important. Kallos et al. (1993) reported that the regional scale phenomena should contribute significantly in the formation of specific air quality conditions in the Greater Athens Area (GAA). Luria et al. (1996) showed that significant degradation of the air quality in some areas should be attributed to regional scale transport phenomena. While the physicochemical properties of various urban plumes have been described at the urban scale with the aid of organized experimental campaigns and/or mesoscale and photochemical modeling (e. g. Ziomas, 1996), not enough attention was paid to the properties of the urban plume as it is passing to areas relatively far from its origin. Consequently, the urban plume impact on remote locations has not been extensively studied. Such phenomena should be considered as very important in some cases, especially in areas with specific characteristics like the Mediterranean Region.

   4. Assimilation of Satellite Data in Regional Air Quality Models

      Richard T. McNider, William B. Norris, Daniel M. Casey, Jonathan E. Pleim, Shawn J. Roselle, William M. Lapenta

      Abstract

      In regional-scale air-pollution models probably no other source of uncertainty ranks higher than the current ability to specify clouds and soil moisture. Because modeled clouds are highly parameterized, the ability of models to predict the magnitude and spatial distribution of radiative characteristics is highly suspect and subject to large error. While considerable advances have been made in the assimilation of winds and temperatures into regional models (Stauffer and Seaman, 1990), the poor representation of cloud fields from point measurements at National Weather Service stations and the almost total absence of observations of surface moisture availability has made assimilation of these variables difficult if not impossible. Yet, the correct inclusion of clouds and surface moisture are of first-order importance in regional-scale photochemistry. Consider the following points relative to these variables.

   5. Evaluation of an Aerosol Model: Responses to Meteorology and Emission Scenarios

      S. C. Pryor, R. J. Barthelmie

      Abstract

      The Fraser Valley is a complex topographic coastal environment which episodically experiences visibility degradation (and elevated aerosol concentrations) (Pryor et al., 1997). To examine concentrations and speciation of secondary inorganic aerosols and ozone in the transition between an oxidant event and period of elevated aerosol concentrations, numerical simulations were performed using a modified version of the ACDEP (Atmospheric Chemistry and Deposition) model. ACDEP is a lagrangian model which contains detailed and fully coupled gas-aerosol phase chemistry (Hertel et al., 1995). The modeling period is August 5–8, 1993, and the modeling domain is shown in Figure 1. Results calculated for two receptor sites are shown herein (locations specified in Figure 1). PIME is located in the western reaches of the valley directly east of the Vancouver metropolitan area, and CHIL is located in a region of mixed agricultural land, approximately 80 km from the Vancouver urban core. The modified ACDEP model was applied at a horizontal resolution of 5 km and with 10 layers in the vertical, increasing logarithmically from 2 m to 2 km. The meteorological parameterizations within ACDEP have been extended such that stability parameters and mixed layer depth are calculated using routinely available meteorological data.

   6. Mesoscale Flow and Pollutants Transport Modelling in North-East Sicily

      P. Grossi, G. Graziani, C. Cerutti

      Abstract

      The area around Milazzo, a city located on a narrow peninsula, north-east Sicily, is heavily polluted by the presence of power plants and refinery. In this work, the atmospheric pollution levels resulting from two circulation regimes are simulated. First, westerly synoptic winds are considered, as the most likely meteorological conditions (Graziani et al., 1997). Then, a less frequent but most dangerous situation with southerly winds is examined. In this meteorological condition, weak winds can develop that may favour the accumulation of pollutants in the most populated area of the city of Milazzo. The RAMS model (version 3b) is used to calculate the flow, in its non-hydrostatic configuration, due to the highly complex terrain. RAMS is initialised and nudged with data from ECMWF model and a multiple nested grid configuration is selected to solve both local flow and large scale circulation over the Mediterranean. The time-dependent RAMS output is used to drive the Lagrangian particle model MONTECARLO, written in terrain following co-ordinates. In the model, buoyancy of hot emissions in convective conditions is taken into account. Non-reactive SO₂ sources are only considered. Both meteorological and concentration model outputs are compared with observations performed during the 1996 Spring campaign (Cerutti et al., 1996).

   7. Mesoscale Modeling of Transport and Deposition of Heavy Metals in Southern Poland

      Marek Uliasz, Krzysztof Olendrzyński, Jerzy Bartnicki

      Abstract

      The Katowice province in southern Poland experiences serious air pollution problems including deposition of heavy metals which is among the highest in Europe (Bartnicki et al. 1996; Olendrzyński et al., 1996). Heavy metals deposit onto surfaces at relatively low rates, however, due to their toxicity and accumulation in soils, long-term deposition needs to be evaluated. Long-range transport models applied to the whole of Europe cannot simulate high values of local deposition fluxes because of their low spatial resolution. A typical grid cell of the long-range models can cover the whole Katowice province. Therefore, it is necessary to apply a high resolution transport and deposition model linked to a three-dimensional mesoscale/regional meteorological model. Recent advances in computer technology, especially availability of modern workstations, allows one to integrate 3-dimensional mesoscale meteorological models over extended time periods, months or even years, to provide necessary input fields for long term dispersion modeling (Uliasz et al., 1996; Pielke and Uliasz, 1997). This paper presents selected results from the METKAT (heavy METals in the KATowice province) project launched by the International Institute for Applied Systems Analysis in cooperation with two Polish research institutions, Institute for Ecology of Industrial Areas (IEIA), Katowice, and Institute of Meteorology and Water Management (IMWM) in Warsaw, The goal of the project was to investigate high local deposition fluxes of arsenic (As), cadmium (Cd), lead (Pb) and zinc (Zn) in the Katowice province with the aid of mesoscale modeling. The extended description of the METKAT study is provided by Uliasz and Olendrzyński (1996).

   8. Biomass Burning: Local and Regional Redistribution

      J. Edy, S. Cautenet

      Abstract

      Tropical biomass biogeochemistry is one of the most poorly understood on the earth. The tropics account for about 60% of the global annual net primary productivity and this enormous productivity is characterized by many chemical species which are emitted as gas or aerosols and can modify the global radiative balance. Biomass burning is associated with agricultural activity in the savannah, the destruction of tropical forests and the use of wood as “fuel”. They release into the atmosphere large quantities of CO2 and a variety of chemically active species such as CO, NOx, N₂O, CH₄, and others expressed in (^{1, 2}). The biomass annually burned in the world represents about 1.8 to 4.7 GT. of carbon (³), savannah fires being the dominant component with about 1-1.6 GT. of carbon burned. Savannah fires alone contribute approximately 10% of the global CO emissions. This phenomenon is especially important in Africa. The contribution of African savannah fires to global emission of trace gas and aerosols has been estimated by (⁴). During dry season, pollution events are similar in magnitude to those observed in industrialised regions as observed in high levels of acid precipitation that were reported in these region (⁵).

   9. High Resolution, Long-Period Modelling of Photochemical Oxidants over Europe

      Joakim Langner, Christer Persson, Lennart Robertson

      Abstract

      Concentrations of surface ozone over Europe currently exceeds the critical levels over which damage to vegetation and health may occur in many locations. This is true also in northern Europe and over Sweden regarding critical levels for vegetation and also occasionally, during summer in southern Sweden, regarding critical levels for human health. Optimising measures to reduce these exeedances, both nationally and internationally, requires a better understanding of the importance of various types of precursor emissions and processes influencing the distribution of photochemical oxidants.

   10. Application of the Urban Airshed Model in the Fraser Valley of British Columia, Canada and Implications to Local Ozone Control Strategies

       Joanne L. Pottier

       Abstract

       The Fraser Valley in the southwestern province of British Columbia, Canada is one of Canada’s highest ozone concentration areas where the National Ambient Air Quality Objective of 82 ppb per hour is exceeded several times a year under high pressure ridge conditions (Taylor, 1991; McKendry, 1994). Modeling efforts are aimed at supporting local regulatory agencies in their attempt to apply appropriate control strategies to the problem. The complex nature of the Fraser Valley offers a modeling challenge. The irregular terrain (Figure 1) generates complex mesoscale flows and modeling is further complicated by changing land use from the urban centre of Vancouver in the west to agricultural farmland in the east. Located on the east coast of the Pacific Ocean, the area is not influenced by upstream transport and thus provides a unique closed system in which to assess and verify model behavior.

   11. Estimates of Sensitivities of Photochemical Grid Models to Uncertainties in Input Parameters, as Applied to UAM-IV on the New York Domain

       Steven R. Hanna, Joseph C. Chang, Mark E. Fernau, D. Alan Hansen

       Abstract

       Because photochemical grid models such as UAM-IV are being used to make policy decisions concerning emissions controls, it is important to know what confidence bounds we can place on the model predictions of, for example, how ozone will respond to changes in emissions. These are presently unknown. The factors influencing prediction error can be classified as input errors, as model formulation errors, or as random stochastic processes. In the present study we include among inputs such things as initial and boundary conditions, emissions, meteorological variables and chemical rate constants. Bias, imprecision and variability can contribute to the error. Formulation errors would include such things as inaccuracies in advection schemes, numerical solvers, process representations, and temporal and spatial resolution. Sometimes the distinction between input and formulation errors is not well drawn. The study described here has been limited by time and resource constraints to an examination of the prediction error associated only with input, not with model formulation, errors. We therefore implicitly assume, without justification, that the model physics and chemistry are correctly formulated. Since model formulation can influence not only simulation fidelity but how input errors are propagated through the model to output errors, we view the results of this study more as a methodological demonstration than a definitive uncertainty analysis.

   12. Effects of Initial and Boundary Values of Reactive Nitrogen Compounds and Hydrocarbons on the Ozone Concentration in the Free Troposphere

       B. Schell, H. Feldmann, M. Memmesheimer, A. Ebel

       Abstract

       The initialisation and the treatment of the boundary conditions of a mesoscale chemistry-transport-model, covering a limited area, are of great importance. The choice of the initial and boundary values can significantly influence the results of a simulation, so that they should be determined as well as possible (NAPAP, 1991). For this reason it is important to provide realistic conditions, if possible derived from current measurements. Unfortunately trace species in the troposphere, especially in the middle and upper free troposphere, are not observed continuously so that relatively little is known about background concentrations. Usually there are no current observations available which can be used as input data for episodic simulations. The available measurements show a high variability in the concentrations of the trace species. To analyse and to quantify the effects of a variation of the initial and boundary values for model results sensitivity studies were carried out with the European Air Pollution Dispersion modeling system (EURAD) using different initial and boundary scenarios. Therefore the literature has been reviewed and a set of initial and boundary values were derived based on available observation data. With regard to the formation of ozone the focus was set on reactive nitrogen species and hydrocarbons, which are important photooxidant precursor species. First a set of simulations with different scenarios representing free tropospheric conditions is calculated with a boxmodel version of the EURAD model in order to determine the non-linear dependencies of the gas phase chemistry. Furthermore a sensitivity study with the full three dimensional model is performed for a summersmog episode.

   13. Fast Sensitivity Analysis of Three-Dimensional Photochemical Models

       Y. J. Yang, J. G. Wilkinson, A. G. Russell

       Abstract

       Photochemical air quality models increasingly are being used to understand the atmospheric dynamics of air pollutants and as the basis of emission control regulations. The response of the these model predictions to system parameters or emission controls provides valuable information for the strategy design to improve air quality. Such information can be pursued via sensitivity analysis, the systematic calculation of sensitivity coefficients, to quantitatively measure these dependencies. However, sensitivity analysis has not seen as wide of use as desired, in part because of the implementation complexity as well as computational limitations. For these reasons, sensitivity analysis has been applied primarily to subsystems of air quality models (e. g. Koda et al., 1974; Rabitz et al., 1983; Milford et al., 1992), or to limited aspects in air quality models (Cho et al., 1987). The “brute-force” method has been the most frequently used to determine model sensitivities, but it rapidly becomes less viable and prohibitively inefficient for a model when a large number of sensitivity coefficients needs to be computed.

   14. Integrating Observations and Modeling in Ozone Management Efforts

       S. Trivikrama Rao, Eric Zalewsky, Igor G. Zurbenko, P. Steven Porter, Gopal Sistla, Winston Hao, Nianjun Zhou, Jia-Yeong Ku, George Kallos, D. Alan Hansen

       Abstract

       Many urban areas in the Eastern United States have been classified to be in non-attainment for ozone, placing a high priority on finding cost-effective emission control measures for improving ambient ozone air quality. Recognizing the complexities associated with the nation’s ozone non-attainment problem, the 1990 Clean Air Amendments mandated the use of grid-based photochemical models for evaluating emission control strategies in urban areas having a serious or higher designation. Given the influx of elevated concentrations of ozone and its precursors into the urban-scale modeling domains (regional-scale transport), many states in the Eastern U.S. were unable to demonstrate ozone attainment for urban areas in their 1994 State Implementation Plans (SIPs) submittal using the urban-scale models. The 1994 SIPs were based on the UAM-IV photochemical model (Morris et al., 1990), which is an urban-scale model that reflects the state-of-science of the late 1980’s. Systems Applications International (SAI) recently developed the UAM-V, a regional-scale ozone air quality model, which contains some new features over the UAM-IV such as multi-scale modeling capability, grid nesting, plume-in-grid (PiG) treatment for point sources, etc. (SAI, 1995). Of particular interest is this model’s treatment of subgrid-scale processes relating to the transport, transformation, and interaction of elevated plumes with the ground-level plume.

   15. Study of the Role of a Stratiform Cloud Layer on the Redistribution of Hydrogen Peroxide

       Nicole Audiffren, Emmanuel Buisson, Nadine Chaumerliac

       Abstract

       Due to its high density of urban and industrial sources, the eastern United States often experiences widespread pollution episodes during the summer (Logan, 1985; Vukovich and Fishman, 1986). The effects of such continental emmissions on the oxiding capacity of atmosphere over the North Atlantic have been studied for many years. Most of the earlier works (Zeller et al., 1977; Kelleher and Feder, 1978; Spicer, 1982) presented evidence for the transport of plumes from the eastern seaboard of the United States out over 100 km or more of the North Atlantic. Measurements at Kejimbuijk National Park in Canada (Brice et al., 1988; Beattie and Wepdale, 1989), begun in 1979, demonstrate transport of these plumes to central Nova Scotia, located at a distance of than 500 km more. The 1993 North Atlantic Regional Experiment (N.A.R.E.) intensive provided further evidences for the transport of anthropogenic pollutants and ozone precussors (CH₄, CO,...) from the continent sources out over the Atlantic ocean (Fehsenfeld et al., 1996). We expect that many tropospheric photo-oxidants are generated by chemical reactions, in particular the hydrogen peroxide. This latter presents a real interest for acidification of the clouds and in gas-phase as a efficient source of OH.

   16. Influence of the Resolution of Emissions and Topography on the Air Pollution Distribution in a Mesoscale Area

       Klaus Nester, Hans-Jürgen Panitz, Franz Fiedler, Walburga Wilms

       Abstract

       The air pollution in a region is influenced by all atmospheric scales. Because it is not possible to resolve all scales in a single model, different models have been developed which describe the air pollution in certain regions, like the European scale model EURAD (EURopean Acid Deposition model (Ebel et al., 1989)) and the mesoscale model system KAMM/DRAIS (KArlsruher Meteorologisches Modell (Adrian and Fiedler, 1991)/DReidimensionales Ausbreitungs- und Immissions-Simulationsmodell (Schwartz, 1996)). Those effects which are smaller than the grid resolution of a model (subgrid effects) have to be considered by appropriate parameterizations or by nesting procedures. Effects resulting from scales which are even larger than the model domain are usually introduced into the model by the boundary conditions.

   17. A Comparison of Calpuff Modeling Results With 1977 Inel Field Data Results

       John S. Irwin

       Abstract

       CALPUFF is a non-steady-state, multi-layer puff dispersion model that simulates the effects of time and space varying meteorological conditions. The puff modeling simulation results are compared with data obtained following a single 3-hour late-afternoon tracer release conducted on April 19, 1977 near Idaho Falls, Idaho, USA. Samplers were positioned on arcs at downwind distances of 3.2, 48 and 90 km. Low-level instrumented masts provided hourly values of wind and temperature at 17 sites within the experimental area. Hourly rawindsondes were available 600 m northwest of the release point. And hourly pibals provided winds aloft at three other sites within the area. In this discussion, alternative combinations of the available meteorological data were used to assess the differences to be seen in the simulation results. Analysis of the results suggests that the simulated lateral dispersion along each arc was best characterized when all of the surface and upper wind observations were used and that the position of the simulated maximum on each arc was poorly characterized regardless of data used.