Josef Brechler

Emissions of biogenic VOC from forest ecosystems in central Europe: Estimation and comparison with anthropogenic emission inventory

This paper describes a method of estimating emission fluxes of biogenic volatile organic compounds (BVOCs) based on the approach proposed by Guenther et al. (1995) and the high-resolution Corine land-cover 2000 database (1x1km resolution). The computed emission fluxes for the Czech Republic (selected for analysis as being representative of a heavily cultivated, central European country) are compared with anthropogenic emissions, both for the entire country and for individual administrative regions. In some regions, BVOC emissions are as high as anthropogenic emissions; however, in most regions the BVOC emissions are approximately 50% of the anthropogenic emissions. The yearly course of BVOC emissions (represented by monoterpenes and isoprene) is presented, along with the spatial distribution of annual mean values. Differences in emission distributions during winter (January) and summer (June) are also considered.

Large Eddy Simulation of the Stable Boundary Layer

The model CLMM (Charles University Large-eddy Microscale Model) is a large-eddy simulation model for atmospheric flows. It solves Navier-Stokes equations for incompressible flow using the projection method and the 3rd order Runge-Kutta method in time. The spatial discretization is performed using the finite volume method on a uniform staggered grid. The capability of the model to compute flows influenced by buoyancy is evaluated in this study in the case of stable stratification of the planetary boundary layer. The results are compared to the results of the project GABLS [2] with a good agreement.

Large eddy simulation modelling of the dispersion of radioactive particulate matter

Field experiments with a Radioactive Dispersion Device (RDD) were performed by the National Radiation Protection Institute (NRPI) of the Czech Republic. We present the results of computer simulations of these experiments using a new microscale model, Charles University Large Eddy Microscale Model (CLMM). The model was first validated using wind tunnel data for the dispersion of continuous passive scalar release around a building with a similar aspect ratio to the building used in the experiments. The results for surface contamination by deposition are highly sensitivity to the particle size distribution, which in the present case has a large scatter.

Model Assessment of Air-Pollution in Prague

Results of relatively simple gaussian dispersion model are presented. This model, developed in the beginning of this decade, is suitable mainly for determination of spatial distributions of annual mean concentrations of such kinds of air-pollution as sulphur dioxide (SO2), mixture of nitrogen oxides (NOx) or suspended particulate matter (SPM) from all types of emission sources located within the city - point sources, line sources and area sources. Model has been used in years 1994, 1996 and 1998 to assess the air-pollution distributions of the above mentioned kinds in the Prague area and the development of the air quality state. It contributed to the decision making process when possible impact of some changes in traffic system or in system of domestic heating, for example, has been investigated. In this contribution, behaviour of sulphur dioxide (SO2) and mixture of nitrogen oxides (NOx) ground concentration distributions are analyzed with respect to changing emission situation in Prague in recent years. Results show that SO2 ground concentration level decreases mainly due to changes in local heating methods and type of fuel used. Different trend can be seen in NOx ground concentrations thanks to rapid increase in the traffic density.

Dispersion and Deposition of Radioactive Particulate Matter from an Explosion

Several experiments of dispersion of radioactive particulate matter after an explosion have been performed by the National Radiation Protection Institute of the Czech Republic. These experiments were set up to simulate an attack by a so-called “dirty bomb”. Many pieces of experimental equipment were used to measure aerosol concentration, deposited activity, dose rates and basic meteorological parameters. In this contribution we perform a computer simulation of this experiment using our in-house CFD (LES) code. We mainly concentrate on deposition of activity in the area of interest and the time evolution of concentration. These experiments are also used as a model short scale scenario for Working group 9 of project EMRAS II coordinated by the IAEA.

Finite Volume Microscale Air-Flow Modelling Using the Immersed Boundary Method

This contribution describes results of computation of a turbulent flow over a square cylinder by 2D large eddy simulation. Solid wall boundary conditions were described by the immersed boundary method.

Air pollution exposure monitoring and estimation VII. Estimation of population exposure in a central European airshed

In order to clarify the local variation in exposure and source-receptor relationships, a dispersion model for estimating air pollution concentrations was developed for a polluted area in the Czech Republic. Three models characterized by different spatial resolution were integrated into one modelling tool. A regional-scale dispersion model accounted for pollution contribution from sources outside the modelling area. Local- and urban-scale dispersion models were used to calculate local concentration distributions. Calculated concentration distributions were evaluated. Deviations between observed and calculated concentrations were not correlated in space, except in episodes, and concentrations measured at spatially representative stations were assimilated into the model results using statistical interpolation (simple kriging). The results indicated that centralized heating plants and local home heating were the most important sources for sulfur dioxide (SO2) pollution. Both high and low level sources may contribute to the accumulation of pollution concentrations in episodes. The measured concentrations were important for the description of distributions in episodes characterized by complex wind and dispersion conditions. The applicability of source oriented model calculations to correctly represent measured concentrations in the pollution episodes was limited due to the fact that meteorological conditions representative of high concentration episodes were characterized by very low wind speed and variable wind directions. About 8,000 individuals were given an exposure estimate representing contribution from local emissions, based on the estimated hourly outdoor exposure to SO2 at their home/work addresses in the 3 month study period in the autumn of 1991. The results showed that, for 5% of participants, the maximum hourly contribution of local emissions was over 380 microg m(-3). For the 3 month average, both large-scale and local-scale pollution contribute significantly. For primary compounds, such as SO2, steep gradients are observed in the vicinity of strong local sources. These gradients are important for exposure characteristics and health effect quantification, and often will not be captured by an existing monitoring network. The calculations can be extended to other periods or to different compounds.

On the Comparison of Nesting of Lagrangian Air-Pollution Model Smog to Numerical Weather Prediction Model ETA and Eulerian CTM CAMX to NWP Model MM5: Ozone Episode Simulation

711 The spatial distribution of air pollution on the local scale of parts of the territory in Czech Republic is simulated by means of Charles University Lagrangian puff model SMOG nested in NWP model ETA. The results are used for the assessment of the concentration fields of ozone, nitrogen oxides and other ozone precursors. A current improved version of the model based on Bednar et al. (2001) covers up to 18 groups of basic compounds and it is based on trajectory computation and puff interaction both by means of Gaussian diffusion, mixing and chemical reactions of basic species. Results of summer photochemical smog episode simulations are compared to results obtained by another couple adopted in the framework of the national project as a basis for further development of data assimilation techniques, Eulerian CTM CAMx nested in NWP model MM5. There are measured data from field campaigns for some episodes as well as air-quality monitoring station data available for comparison of model results with reality. Usually, there is a problem with emission data for the simulations and definitely they are far from actual instantaneous data. Both the couples have rather older databases of emissions available with many uncertainities, for

Modelling Activity in the Framework of the National Project “Transformation of Air-Pollution, Modelling its Transport and Dispersion”

In the framework of the presented activity a spatial distribution of tropospheric ozone is modelled. An overview of the ozone distribution will be given for local modelling study with very high resolution. Model results will be tested against measured data that will be collected both from field campaigns and from existing monitoring networks. Within this modelling activity results of some formerly and simultaneously solved projects can be also used.

Non-hydrostatic model of airflow over irregular topography — Theoretical bases

SummaryThis article deals with some problems connected with the formulation of a non-hydrostatic mesoscale model of airflow in the atmosphere. Due to an irregular surface a terrain-following coordinate system is used and the equations of the model are transformed into this system. Sound waves are eliminated by the use of the anelastic approximation. The influence of boundaries is minimized by the use of open boundary conditions at the lateral boundaries of the computational domain and of the absorbing layer beneath the upper boundary.