The analysis of large data sets in meteorological and air quality studies is often made though the examination of specific case studies, especially when time-consuming computational models are ...employed. This paper presents the development of a tool to identify specific case studies, termed as representative days, that would subsequently be modelled. The success of such tools should be judged on the discrimination between the specified cases: and the degree to which they capture and recreate historical characteristics of the original data set. The developed approach utilises a principal component algorithm with varimax rotation (r-PCA) and the subtractive clustering algorithm coupled with a cluster validity criterion. In this paper, the developed tool is applied to a data set from the North Sea, utilizing two years worth of data from the DNMI operational forecasting model. The results will be subsequently used in photochemical and radiative forcing modelling tools as part of the EC funded project AEOLOS, with the ultimate goal to estimate the global warming potential of non-radioactive tracing substances such as SF6 and PFCs, which are heavily used in the oil industry.PUBLICATION ABSTRACT
When developing a physically based mathematical description of hydrological processes over natural watersheds, the modeler faces the requirement of complete spatial specification of the various ...hydro-geological parameters as well as the ground surface characteristics. The usual approach, i.e. the use of representative average values in simplified configurations of the actual conditions, often leads to discrepancies. A detailed description of the topography is therefore needed but, on a complex topography, the accurate determination of overland cascades and streams often poses difficult problems.
The proposed method aims to provide some more insight into the above-mentioned problems. In order to simulate overland trajectories of runoff water and channel flow paths, the method represents the topography using a network of non-overlapping triangular surfaces of known properties (i.e. slope, orientation, area, soil texture, land-use), created with an appropriate digital elevation model. The simulated overland cascades may feed channels, terminate to local minima of altitude or reach the boundaries of the domain under consideration. The model allows for the use of variable resolution and has nesting capabilities.
The method has been applied on the Lucky Hills watersheds at Walnut Gulch, Arizona, using four different resolution schemes. The examination of the model's output shows that the various overland trajectories and channel flow paths are accurately computed in accordance with the model's specifications. Additionally, each simulated river network ended up at an outlet that precisely coincided (within the resolution) with the fixed position of the measurement station. No tuning efforts were undertaken and the model did not need calibration. This method seems to be advantageous compared to many of those in use, since it is fully automatic and time saving while proven to accurately simulate the drainage network. In addition, the method creates a detailed database easily accessible for the forthcoming assessment of the hydrologic response of the watershed in the frame of a distributed model.
The advantageous utilization of triangular prismatic grid for flow simulation over irregular geometries is widely recognized. Such grid is here utilized to diagnose the atmospheric conditions and ...pollutant dispersion over complex inhomogeneous surfaces. One case with an extremely complex surface is resolved with regular prismatic grid. A second case, including parts of flat and mountainous areas, is resolved with completely unstructured grid. The atmospheric calculations rely on field data. The detailed surface description achieved through the triangular mesh allows facing lack of observations at significant sites, while it permits the selective use of the measurements for the determination of the local atmospheric conditions. The simulations are compared against observed pollutant concentrations. A quite satisfactory agreement is obtained, indicating that diagnostic models using improved surface resolution can provide reasonable results over complex terrain. This is considered very important since the use of diagnostic models is strongly suggested in emergency response cases.
Data assimilation (DA) procedures were developed and implemented in the frames of the meteorological pre-processor (MPP) of an emergency response system (ERS) to enable simultaneous use of different ...meteorological measurements (wind velocity, cloud cover, net radiation, precipitation) with Numerical Weather Prediction (NWP) data. The DA procedures were based on the optimal interpolation algorithm and the method of iterations to optimal solution, combined with methods for scaling the weighting coefficient between fields obtained by the measurements and those obtained by the NWP data. For validation purposes, the calculation by the MPP meteorological fields were compared against measurements performed in two real-scale experiments (ETEX1 and 2). Data from ground-based synoptic weather stations were used for the improvement, through DA procedures, of the first-guess fields obtained from the NWP data, while measurements from surface stations, sonic anemometer and sodar were used for comparison with the results of the MPP. The performance of the two developed DA procedures was evaluated through statistical indices (root mean square and systematic deviation of wind speed and direction) and through graphical representations. Both DA procedures improved the agreement between computed and measured meteorological fields in both examined experiments.
A set of methods has been compiled to compare gridded air emission inventories that have been derived, on the same spatial grid, using widely differing techniques. Top-down and bottom-up inventories ...for Milan, Italy and for the Greater Athens area (GAA), Greece were used to test and apply these methods. The applicability of each method to certain source sectors was assessed by conducting sensitivity analyses. Whilst some of the methods (such as regression calculations or the Moran coefficient) appeared very sensitive to variations of point source emissions, others (e.g. the construction of difference maps) proved more appropriate for characterizing line source differences. Area sources could best be dealt with by using the newly developed acceptability criterion. The development of these tools allows a reproducible comparison of sets of emission inventories and consequently supports developments towards improvement.
Hospital sales to physicians Gounaris, N
Medical products sales : MPS : the official journal of the American Surgical Trade Association
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Journal Article
The advantageous utilization of triangular prismatic grid for flow simulation over irregular geometries is widely recognized. Such grid is here utilized to diagnose the atmospheric conditions and ...pollutant dispersion over complex inhomogeneous surfaces. One case with an extremely complex surface is resolved with regular prismatic grid. A second case, including parts of flat and mountainous areas, is resolved with completely unstructured grid. The atmospheric calculations rely on field data. The detailed surface description achieved through the triangular mesh allows facing lack of observations at significant sites, while it permits the selective use of the measurements for the determination of the local atmospheric conditions. The simulations are compared against observed pollutant concentrations. A quite satisfactory agreement is obtained, indicating that diagnostic models using improved surface resolution can provide reasonable results over complex terrain. This is considered very important since the use of diagnostic models is strongly suggested in emergency response cases. (Author)
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