| 1. |
- Belanger, N, et al.
(författare)
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Simulation of soil chemistry and nutrient availability in a forested ecosystem of southern Quebec - I. Reconstruction of the time-series files of nutrient cycling using the MAKEDEP model
- 2002
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Ingår i: Environmental Modelling & Software. - 1364-8152. ; 17:5, s. 427-445
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Tidskriftsartikel (refereegranskat)abstract
- The MAKEDEP model is used to reconstruct the time-series input files of deposition, forest growth, uptake and litterfall needed to run the dynamic biogeochemical model SAFE. The amounts and timing of N made available for tree growth is what determines most of the model output. In this paper, the sensitivity Of MAKEDEP to various amounts and timing of N availability, including increased supplies of N prior to air pollution assuming increased biological N-2 fixation, was assessed in a small hardwood stand of southern Quebec. The scenarios of N cycling were validated for burned and unburned conditions based on the simulated tree growth and N leaching rates as well as the model's ability to recreate the trends in atmospheric deposition of major ions in northeastern North America. The N leaching rates were calculated as the residual component of all simulated processes acting as sources and sinks of N. The N availability scenarios that subtracted/added 5 mmol m(-2) yr(-1) of NH4 in the unburned and burned conditions, respectively, recreated N leaching rates and tree biomass with the most precision. Modifying the amounts of N made available prior to air pollution was also necessary for the trees to grow to reasonable values before 1900. Historical trends of deposition were linked to the changes in the continental emissions in northeastern North America. Observational data for 30 years at the Hubbard Brook Experimental Forest, New Hampshire, showed convergent trends for most ions with the deposition trends simulated with MAKEDEP.
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| 2. |
- Belanger, N, et al.
(författare)
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Simulation of soil chemistry and nutrient availability in a forested ecosytem of southern Quebec. Part II. Application of the SAFE model
- 2002
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Ingår i: Environmental Modelling & Software. - 1364-8152. ; 17:5, s. 447-465
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic soil model SAFE was calibrated and validated in a small hardwood forest of southern Quebec as a function of its ability to reproduce current soil chemistry and similar pre-industrial soil conditions despite the difference in forest history. SAFE was relatively accurate for reproducing soil chemistry, but comparison of pre-industrial soil conditions between unburned and burned stands casts doubt as to its applicability at sites where specific processes may be involved in nutrient cycling, e.g. the immobilization of N by microbes. Simulated soil chemistry in the unburned zone reinforced the conclusions of a few historical studies which support the hypothesis that acid-sensitive forest sites of northeastern USA underwent significant acidification when major inputs of acidity from the atmosphere occurred, i.e. during the 1930-1980 time span. Model projections in the mineral soil suggest that a new steady-state should be reached in the 21st century assuming no harvest, but that this equilibrium is broken if timber harvesting is done. Model output also suggests that cation nutrient deficiencies could occur in the long-term, but future Al phytotoxic responses are unlikely to occur due to a relatively high projected pH. Finally, it was demonstrated that the time-series files of nutrient cycling should be prepared with care as they can be the source of some abnormalities in model calibration.
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| 3. |
- Parker, P, et al.
(författare)
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Progress in integrated assessment and modelling
- 2002
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Ingår i: Environmental Modelling & Software. - 1364-8152. ; 17:3, s. 209-217
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Tidskriftsartikel (refereegranskat)abstract
- Environmental processes have been modelled for decades. However. the need for integrated assessment and modeling (IAM) has,town as the extent and severity of environmental problems in the 21st Century worsens. The scale of IAM is not restricted to the global level as in climate change models, but includes local and regional models of environmental problems. This paper discusses various definitions of IAM and identifies five different types of integration that Lire needed for the effective solution of environmental problems. The future is then depicted in the form of two brief scenarios: one optimistic and one pessimistic. The current state of IAM is then briefly reviewed. The issues of complexity and validation in IAM are recognised as more complex than in traditional disciplinary approaches. Communication is identified as a central issue both internally among team members and externally with decision-makers. stakeholders and other scientists. Finally it is concluded that the process of integrated assessment and modelling is considered as important as the product for any particular project. By learning to work together and recognise the contribution of all team members and participants, it is believed that we will have a strong scientific and social basis to address the environmental problems of the 21st Century.
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| 4. |
- Forsman, Åsa, 1972-, et al.
(författare)
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Reduced models for efficient simulation of spatially integrated outputs of one-dimensional substance transport models
- 2003
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Ingår i: Environmental Modelling & Software. - 1364-8152 .- 1873-6726. ; 18:4, s. 319-327
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Tidskriftsartikel (refereegranskat)abstract
- We examined under what circumstances the results of a large number of runs of the one-dimensional, physics-based SOIL/SOILN nitrate transport model can be combined into a reduced (or meta) model. We considered the total flow of nitrate from a given area and investigated when and how hidden linear structures can be extracted from the underlying model. The presence of such structures can justify the use of spatially aggregated inputs to compute spatially aggregated outputs. Extensive Monte-Carlo simulations showed that some linear structures emerged when the outputs for a long period of time were summed. Other linear structures appeared as relationships between two different components of the model outputs. However, different cropping systems respond differently to changes in anthropogenic or meteorological forcings. Therefore, we derived a reduced model of long-term leaching of nitrogen from the root zone in an agricultural area by combining each combination of soil type and cropping system. Reduced models can help make process-oriented models more transparent, and they are particularly suitable for incorporation into decision support systems.
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| 5. |
- Jansson, Per-Erik., et al.
(författare)
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A coupled model of water, heat and mass transfer using object orientation to improve flexibility and functionality
- 2001
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Ingår i: Environmental Modelling & Software. - 1364-8152 .- 1873-6726. ; 16:1, s. 37-46
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Tidskriftsartikel (refereegranskat)abstract
- The challenge of our software development is to introduce user-friendly document-orientation and graphical features that are typical in Windows software and to retain the possibility of easily extending existing legacy Fortran code. Keys to this development were the use of five development tools and our special management of shared memory. Numerical development of the code was thus continued in Fortran while the newly introduced multiple-document interface allows the new graphical features that are considered more user friendly (e.g. tool bar, status bar, animation, etc.) can be further refined and adjusted using Visual C++6.0 and the MS Visual Studio. Object orientation makes it possible to include modules with different type of dependencies that restrict the user interface to the specific use of the model. A large number of sub-models are combined and all input/output data have been adapted to an object-oriented standard. Multiple-run features and built-in links to a common database are new important features.
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| 6. |
- Sivertun, Åke, 1950-, et al.
(författare)
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Non-point source critical area analysis in the Gissel÷ watershed using GIS
- 2003
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Ingår i: Environmental Modelling & Software. - 1364-8152 .- 1873-6726. ; 18:10, s. 887-898
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Tidskriftsartikel (refereegranskat)abstract
- In the southeast in Norrk÷ping, Sweden, is a small fjord-like bay called SlΣtbaken. The water quality in SlΣtbaken - with its narrow outlet to the Baltic Sea - depends highly on the water quality of the streams that flow in it. While point pollution sources can be identified easily in general, the non-point sources are harder to find. The most important sources for non-point pollution are agricultural areas, and the pollutants are mostly nutrients like phosphorus, which come from the fertilisation of the fields. One important catchment area for SlΣtbaken is the 57.7 km2 Gissel÷ river basin (part of the topographic map 8GNO), which contains large agricultural areas. The transport of water pollutants is based on the same hydrological processes as erosion and sediment transport. The implementation of such a model in a GIS allows the analysis of a large area with a high resolution. When choosing the model, special attention was paid to the possibility of using a verified model that is easy to implement in a commercial GIS without the need of too much expert knowledge. This may allow its widespread use in many administrative applications that need non-point source information. A feasibility test for an enhanced GIS USLE model was done in the Gissel÷ drainage basin before it was implemented for all river basins in the whole administrative area of Norrk÷pings kommun. It is possible to use the suggested simplified USLE model to estimate the load of both pollutants and sediments, and it is able to show the areas that are critical for the water quality at the outlet of the water basin. The model has been evaluated in three studies [Int. J. Geogr. Inf. Syst. 2 (4) (1988) 365, A GIS to target critical areas for non point source management, in: Proceedings of the International Non Point Source Management Symposium, Austin, TX, November 7, 1989, Vatten 48 (1992) 117]. Then, implemented in a very simple GIS that allowed only rough estimates of terrain models and distances, the model was able to estimate the total suspended solids (TSS) and total phosphorus (TP) loads in the Svartσ river basin of 1539 km2 in the same region as Gissel÷ and the Bornsj÷ river basin outside Stockholm. Besides an estimated R2 of 0.91-0.98 (verified by a more than one year measurement from manual and automated sampling stations in the whole river basin), the benefit with the GIS implemented USLE was the possibility to identify the risk areas with high spatial accuracy. During the last decade, both available databases and software have changed the possibilities to identify areas at risk of nutrient leakage. Schein [GIS Methods for Monitoring Sustainable Development by Analysis of Land-use and Land Cover Changes in the Surroundings of Link÷ping (Sweden), Institut fⁿr Photogrammetrie und Fernerkundung, Technische UniversitΣt Dresden, Germany] and Schein and Sivertun [Method and models for sustainable development monitoring and analyses in GIS, in: Proceedings of the International Workshop on Geo-Spatial Knowledge Processing for Natural Resource Management, University of Insubria, Varese, Italy, June 28-29, 2001] show that the enhanced land use data available through the European Union agricultural support program can be used together with remote sensing data to fine tune the modified GIS USLE model. The problems with the new 50 x 50 m digital elevation data now available are also pointed out here. Obvious errors in the data and possibilities to enhance the model by introducing a better terrain model were two important suggestions in these works. In this article, two modifications to the original model are suggested. One is enhancement of the digital terrain model by using height curves from the digital 1:50 000 scale topographic map, and the other is a smooth distance function that better reflects the impact of nutrients on water bodies. Because of its easy implementation on standard low cost systems, the GIS USLE model is suitable for analysing huge areas for critical places. The results can lead to more detailed studies in the risk areas thus identified or to investigations on the effect of land use changes, or can be used simply for taking care in the use of fertilisers and other chemicals in the critical agricultural areas.
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| 7. |
- Skalin, J., et al.
(författare)
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A nonlinear time series model of El Niño
- 2001
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Ingår i: Environmental modelling & software : with environment data news. - : Elsevier Ltd. - 1873-6726 .- 1364-8152. ; 16:2, s. 139-146
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Tidskriftsartikel (refereegranskat)abstract
- A smooth transition autoregressive model is estimated for the Southern Oscillation Index, an index commonly used as a measure of El Niño events. Using standard measures there is no indication of nonstationarity in the index. A logistic smooth transition autoregressive model describes the most turbulent periods in the data (these correspond to El Niño events) better than a linear autoregressive model. The estimated nonlinear model passes a battery of diagnostic tests. A generalised impulse response function indicates local instability, but as deterministic extrapolation from the estimated model converges, the nonlinear model may still be useful for forecasting the El Niño Southern Oscillation a few months ahead.
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| 8. |
- An, Li, et al.
(författare)
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Modeling agent decision and behavior in the light of data science and artificial intelligence
- 2023
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Ingår i: Environmental Modelling & Software. - 1364-8152 .- 1873-6726. ; 166
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Tidskriftsartikel (refereegranskat)abstract
- Agent-based modeling (ABM) has been widely used in numerous disciplines and practice domains, subject to many eulogies and criticisms. This article presents key advances and challenges in agent-based modeling over the last two decades and shows that understanding agents' behaviors is a major priority for various research fields. We demonstrate that artificial intelligence and data science will likely generate revolutionary impacts for science and technology towards understanding agent decisions and behaviors in complex systems. We propose an innovative approach that leverages reinforcement learning and convolutional neural networks to equip agents with the intelligence of self-learning their behavior rules directly from data. We call for further developments of ABM, especially modeling agent behaviors, in the light of data science and artificial intelligence.
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| 9. |
- Antosz, Patrycja, et al.
(författare)
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What do you want theory for? - A pragmatic analysis of the roles of theory in agent-based modelling
- 2023
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Ingår i: Environmental Modelling & Software. - 1364-8152 .- 1873-6726. ; 168
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Tidskriftsartikel (refereegranskat)abstract
- There has been some discussion about agent-based modelling (ABM) and theory, particularly how ABM might facilitate theory building. However, there is confusion about the different ways they could relate and some scepticism as to whether theory is needed if one has an ABM. This paper distinguishes some of the different ways that the term “theory” is used in ABM papers in three important ABM journals: Environmental Modelling & Software, Computers, Environment and Urban Systems and the Journal of Artificial Societies and Social Simulation. Apart from the simple-minded identification of theory with mathematics, we distinguish nine different ways that theory and ABM relate. This analysis is situated with respect to some of the expectations and philosophical background behind the idea of “theory”. The paper concludes with some ways in which theory and ABM could work better together, some possible ways forward and suggests that a more cautious approach to generalisation might be more appropriate.
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| 10. |
- Ayllón, Daniel, et al.
(författare)
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Keeping modelling notebooks with TRACE : Good for you and good for environmental research and management support
- 2021
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Ingår i: Environmental Modelling & Software. - : Elsevier BV. - 1364-8152 .- 1873-6726. ; 136
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Tidskriftsartikel (refereegranskat)abstract
- The acceptance and usefulness of simulation models are often limited by the efficiency, transparency, reproducibility, and reliability of the modelling process. We address these issues by suggesting that modellers (1) “trace” the iterative modelling process by keeping a modelling notebook corresponding to the laboratory notebooks used by empirical researchers, (2) use a standardized notebook structure and terminology based on the existing TRACE documentation framework, and (3) use their notebooks to compile TRACE documents that supplement publications and reports. These practices have benefits for model developers, users, and stakeholders: improved and efficient model design, analysis, testing, and application; increased model acceptance and reuse; and replicability and reproducibility of the model and the simulation experiments. Using TRACE terminology and structure in modelling notebooks facilitates production of TRACE documents. We explain the rationale of TRACE, provide example TRACE documents, and suggest strategies for keeping “TRACE Modelling Notebooks.”
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