Jørgen Brandt - Academia.edu (original) (raw)
Papers by Jørgen Brandt
Journal of the Air & Waste Management Association (1995), 2016
Mumbai a highly populated city in India has been selected for air quality mapping and assessment ... more Mumbai a highly populated city in India has been selected for air quality mapping and assessment of health impact using monitored air quality data. Air quality monitoring networks in Mumbai are operated by National Environment Engineering Research Institute (NEERI), Maharashtra Pollution Control Board (MPCB) and Brihanmumbai Municipal Corporation (BMC). A monitoring station represents air quality at a particular location, while we need spatial variation for air quality management. Here, air quality monitored data of NEERI and BMC were spatially interpolated using various inbuilt interpolation techniques of ArcGIS. Inverse Distance Weight (IDW), Kriging (Spherical and Gaussian) and Spline techniques have been applied for spatial interpolation for this study. The interpolated results of air pollutants Sulpher dioxide (SO2), Nitrogen dioxide (NO2) and Suspended Particulate Matter (SPM) were compared with air quality data of MPCB in the same region. Comparison of results showed good agr...
Risk Analysis, 2015
Designing air quality policies that improve public health can benefit from information about air ... more Designing air quality policies that improve public health can benefit from information about air pollution health risks and impacts, which include respiratory and cardiovascular diseases and premature death. Several computer-based tools help automate air pollution health impact assessments and are being used for a variety of contexts. Expanding information gathered for a May 2014 World Health Organization expert meeting, we survey 12 multinational air pollution health impact assessment tools, categorize them according to key technical and operational characteristics, and identify limitations and challenges. Key characteristics include spatial resolution, pollutants and health effect outcomes evaluated, and method for characterizing population exposure, as well as tool format, accessibility, complexity, and degree of peer review and application in policy contexts. While many of the tools use common data sources for concentration-response associations, population, and baseline mortality rates, they vary in the exposure information source, format, and degree of technical complexity. We find that there is an important tradeoff between technical refinement and accessibility for a broad range of applications. Analysts should apply tools that provide the appropriate geographic scope, resolution, and maximum degree of technical rigor for the intended assessment, within resources constraints. A systematic intercomparison of the tools' inputs, assumptions, calculations, and results would be helpful to determine the appropriateness of each for different types of assessment. Future work would benefit from accounting for multiple uncertainty sources and integrating ambient air pollution health impact assessment tools with those addressing other related health risks (e.g., smoking, indoor pollution, climate change, vehicle accidents, physical activity).
Tropospheric Ozone has a damaging effect on vegetation, where it inhibits growth and reduces yiel... more Tropospheric Ozone has a damaging effect on vegetation, where it inhibits growth and reduces yield of crop production, as well as causing visible damage to plant leaves. The reduced crop production and growth of forest trees can be assessed using species specific sensitivity factors and market prices. The damages to agriculture are severe and a treat to food security. However, anthropogenic emissions of air pollution are not causing ozone damage to vegetation locally because of redox titration of ozone in the pollution source area. The ozone damage is taking effect hundreds of kilometers further downwind, where the atmospheric content of ozone has stabilized. This means that ozone damage can have a large effect outside an emitting country's borders, while the effects inside are limited or even have reducing effects of ozone damage from other sources. As part of CEEH (Centre for energy, environment and health), we are assessing ozone damage to forest and vegetation in European co...
Springer Proceedings in Complexity, 2016
Mathematical transport-chemistry models are strong tools for evaluation of emission reduction str... more Mathematical transport-chemistry models are strong tools for evaluation of emission reduction strategies, for providing information to the public, and as the central part of models for human exposure to air pollution. NERI's recently developed AirGIS is an example of such a system. An air pollution forecasting system THOR has been established and provides 72-h air pollution forecasts two to four times a day. The THOR system generates forecasts for three different scales: rural areas, urban background and street level. Various human exposure studies have been carried out in Denmark and serve the basis for model development and validation. Recently monitoring of particulate matter has been included in these studies and preliminary results indicate that exposure to indoor air pollution plays an important role for the personal exposure to PM 2.5 .
Applied Parallel …, 1996
Page 1. Coupling the Advection and the Chemical Parts of Large Air Pollution Models J. Brandt 1 ,... more Page 1. Coupling the Advection and the Chemical Parts of Large Air Pollution Models J. Brandt 1 , I. Dimov , K. Georgiev , J. Wasniewski 3 and Z. Zlatev 1 ... The Silicon Graphics POWER CHALLENGE is a parallel machine with shared memory. ...
Atmospheric Chemistry and Physics, Nov 22, 2004
A new 3-D mercury model has been developed within the Danish Arctic Monitoring and Assessment Pro... more A new 3-D mercury model has been developed within the Danish Arctic Monitoring and Assessment Programme (AMAP). The model is based on the Danish Eulerian Hemispheric Model, which in the original version has been used to study the transport of SO2, SO42- and Pb into the Arctic. It was developed for sulphur in 1990 and in 1999 also lead was included. For the current study a chemical scheme for mercury has been included and the model is now applied to the mercury transport problem. Some experiments with the formulation of the mercury chemistry during the Polar Sunrise are carried out in order to investigate the observed depletion. Some of the main conclusions of the work described in this paper are that atmospheric transport of mercury is a very important pathway into the Arctic and that mercury depletion in the Arctic troposphere during the Polar Sunrise contributes considerably to the deposition of mercury in the Arctic.
Natural emissions play an important role in determining ambient levels of harmful atmospheric pol... more Natural emissions play an important role in determining ambient levels of harmful atmospheric pollutants, especially tropospheric ozone and particulate matter (PM). Natural sources have become more important with the ongoing reductions of anthropogenic emissions and are expected to be even more significant in the future in connection with a changing climate. Despite of the efforts made for modelling of natural emissions, the uncertainties and gaps with regard to investigation and quantification of these emissions are still quite large. In this study, the large-scale atmospheric chemistry transport model, DEHM (the Danish Eulerian Hemispheric Model) is further developed, evaluated and applied to study and quantify the contributions of many compounds from the natural sources to the concentration of ozone and formation of PM. The relative contributions are calculated for the domain covering more than the Northern Hemisphere for a typical year 2006. Natural source categories adopted in the recent model consist of vegetation, lightning, soils, wild animals and oceans. Here, DEHM has been further developed to include more natural emissions of biogenic volatile organic compounds (VOCs) as well as a scheme for describing secondary organic aerosols. Moreover, the parameterization used for estimating sea-salt generation has been modified to contain additional features. Evaluation of the modeled total fine PM, against observations, is conducted for both the previous and new model versions to assess improvement of the model performance with the updated description of natural emissions. Using the developed DEHM, our simulations indicate that at the Northern Hemisphere the contribution from natural emissions to the average annual ozone concentrations over land is between 4-30 ppbV. Among the natural emissions, biogenic VOCs are found to be the most significant contributors to ozone formation. Our results show that biogenic VOCs enhance the average ozone concentration with around 11% over land areas of the Northern Hemisphere. Similarly, the highest contribution of all the natural sources to total fine particles over land is observed in South America by about 74% and sea-salt aerosols found to play the most important role. However, over the rest of regions in the model domain the largest contribution from the natural sources to PM2.5 is due to wildfires. The contribution from natural emissions to the mean PM2.5 concentration over the land areas in the model domain is about 34%.
Journal of Computational Physics, 2002
A new 3-D model REGINA (REGIonal high resolutioN Air pollution model) is under development at the... more A new 3-D model REGINA (REGIonal high resolutioN Air pollution model) is under development at the National Environmental Research Institute (NERI). The model is based on models developed over the past decades at NERI. The goal is to obtain a nested model capable of high-resolution operation. To reach this goal it is necessary to implement sufficiently accurate numerical methods. The model will be applied to studying air pollution phenomena (monitoring, forecasting, and scenarios) over Denmark. In the present paper, the outline of the new model is presented. The numerical methods for transport and chemistry are described. The horizontal transport in the model is solved using an accurate space derivatives algorithm. This method traditionally requires periodic boundary conditions, which are not applicable for nested modeling. Therefore a new method for calculating nonperiodic boundary conditions has been developed. The numerical solution to the chemistry part of the model is obtained from an implementation of a new combination of two existing numerical methods. The results from extensive testing of the numerical solution of the advection and the coupling of the solution of advection and chemistry in the model using Molenkamp-Crowley rotation tests are presented. The same tests have been applied to the model with and without nesting. The results show that the numerical methods are suitable for modeling air pollution levels at high resolution.
A 3-d mercury model is in the progress of development. The model is based on the Danish Eulerian ... more A 3-d mercury model is in the progress of development. The model is based on the Danish Eulerian Hemispheric model, which in the original version have been used to study the transport of SO2, SO42- and Pb into the Arctic (see Christensen, 1997). The horizontal space of the model is defined on a regular 96x96 grid that covers most of the Northern Hemisphere with a grid-resolution of 150 km at 60oN. Meteoro-logical data are obtained from the European Centre for Medium-range Weather Forecasts (ECMWF) on a 2.5ox2.5o grid with a time resolution of 12 hours that are used as in- put to the MM5 mesoscale modelling system, which produce the final meteorological input for the DEHM model. The whole system includes also two-way nesting capa- bilities, so it is possible to do finer (150 km -> 50 km -> 16.67 km, etc) model calcu- lations over e.g. the Arctic Ocean or Greenland. In the current version the emissions of anthropogenic Mercury are based on the global inventory of Mercury emissions for 1995 on a 1ox1o grid (Pacyna et al, 2001). The chemistry is based on the scheme from the GKSS model (see Petersen et al, 1998). Some results from the model system will be presented with emphasizing on the simulation of the mercury depletion in the Arctic during the Polar Sunrise.
Transport and Chemical Transformation in the Troposphere, 2001
With a specific focus on Europe as part of the AEROCARB/CARBO-EUROPE project, we use atmospheric ... more With a specific focus on Europe as part of the AEROCARB/CARBO-EUROPE project, we use atmospheric models to assess the monthly sources and sinks of atmospheric CO2 for the year 1998. A Bayesian inverse approach is used (top-down) where the spread between modelled and measured CO2 concentrations in the atmosphere is minimised. We divide Europe into as much as 26 regions
A new model system for mapping and forecasting nitrogen deposition to the Baltic Sea has been dev... more A new model system for mapping and forecasting nitrogen deposition to the Baltic Sea has been developed. The system is based on the Lagrangian variable scale transport-chemistry model ACDEP (Atmospheric Chemistry and Deposition model), and aims at delivering deposition estimates to be used as input to marine ecosystem models. The system is tested by comparison of model results to measurements from monitoring stations around the Baltic Sea. The comparison shows that observed annual mean ambient air concentrations and wet depositions are well reproduced by the model. Diurnal mean concentrations of NH x (sum of NH 3 and NH + 4 ) and NO 2 are fairly well reproduced, whereas concentrations of total nitrate (sum of HNO 3 and NO − 3 ) are somewhat overestimated. Wet depositions of nitrate and ammonia are fairly well described for annual mean values, whereas the discrepancy is high for the monthly mean values and the wet depositions are rather poorly described concerning the diurnal mean values. The model calculations show that the annual atmospheric nitrogen deposition has a pronounced south-north gradient with depositions in the range about 1.0 T N km −2 in the south and 0.2 T N km −2 in the north. The results show that in 1999 the maximum diurnal mean deposition to the Danish waters appeared during the summer in the algae growth season. For the northern parts of the Baltic the highest depositions were distributed over most of the year. Total deposition to the Baltic Sea was for the year 1999 estimated to 318 kT N for an area of 464 406 km 2 equivalent to an average deposition of 684 kg N/km 2 .
Data assimilation can be used with air quality models to improve historical simulations or initia... more Data assimilation can be used with air quality models to improve historical simulations or initial conditions for forecasts. The ensemble Kalman filter is an assimilation technique that uses a low-dimensional representation of the background error covariances. We have coupled an offline chemical transport model, the DEHM (the Danish Eulerian hemispheric model), with an asynchronous ensemble Kalman filter (AEnKF), which accounts for timing discrepancies between observation and the analysis time. We will present the structure and initial results using this simulation-assimilation framework. To evaluate the DEHM-AEnKF system, we assimilated a single species, carbon monoxide. Carbon monoxide is a moderately long-lived atmospheric trace gas, and its concentration is measured routinely from a number of different measurement platforms. The chemistry of CO is simpler than other well-studied species (e.g., ozone). Thus CO is a good candidate species for the initial testing of a chemical data...
Large ozone concentrations have harmful effects on forests and crops when these exceed some criti... more Large ozone concentrations have harmful effects on forests and crops when these exceed some critical levels. It is believed that the damages in USA due to high ozone concentrations exceed several billions dollars. Therefore it is worthwhile to investigate different actions that could be applied in the attempts to reduce the harmful effects. One needs reliable mathematical models in such studies. Reliable models are normally very big and it is difficult to treat them numerically, because they lead, after some kind of discretization and after the implementation of some appropriate splitting procedure, to several very huge systems of ordinary differential equations (up to order of 106). Moreover, these systems have to be treated numerically during many time-steps (typically several thousand time-steps per run are necessary). The use of modern parallel and/or vector machines is an important condition in the efforts to handle successfully big air pollution models. If the numerical algori...
International Journal of Computational Science and Engineering, 2007
... This is a major part of the computational work and is based on scheme described in Section 3.... more ... This is a major part of the computational work and is based on scheme described in Section 3. Let us reiterate here that ... 7 Numerical examples ... The first example is a linear first-oder PDE, which is in some sense similar to the problems arising in the advection sub-model when ...
Flood forecasting specialists and operational water managers require ready access to a wide range... more Flood forecasting specialists and operational water managers require ready access to a wide range of information including both current and forecasted meteorological conditions, and current and forecasted hydrological conditions to make decisions to initiate flood response measures or to issue flood warnings. Effective flood forecasting systems must provide reliable, accurate and timely forecasts for a range of catchments; from small rapidly responding upstream catchments to larger, more slowly responding downstream locations, often within the same region. Using meteorological observations and quantitative precipitation forecasts to produce hydrological flood forecasts provides valuable increases in lead-time that can be exploited to mitigate the effects of extreme floods. However while the value of accurate meteorological and hydrological forecasts are widely recognised real-time flood management decisions must be based on an understanding of the uncertainties and associated risks....
Physics and Chemistry of the Earth, Parts A/B/C, 2002
Journal of the Air & Waste Management Association (1995), 2016
Mumbai a highly populated city in India has been selected for air quality mapping and assessment ... more Mumbai a highly populated city in India has been selected for air quality mapping and assessment of health impact using monitored air quality data. Air quality monitoring networks in Mumbai are operated by National Environment Engineering Research Institute (NEERI), Maharashtra Pollution Control Board (MPCB) and Brihanmumbai Municipal Corporation (BMC). A monitoring station represents air quality at a particular location, while we need spatial variation for air quality management. Here, air quality monitored data of NEERI and BMC were spatially interpolated using various inbuilt interpolation techniques of ArcGIS. Inverse Distance Weight (IDW), Kriging (Spherical and Gaussian) and Spline techniques have been applied for spatial interpolation for this study. The interpolated results of air pollutants Sulpher dioxide (SO2), Nitrogen dioxide (NO2) and Suspended Particulate Matter (SPM) were compared with air quality data of MPCB in the same region. Comparison of results showed good agr...
Risk Analysis, 2015
Designing air quality policies that improve public health can benefit from information about air ... more Designing air quality policies that improve public health can benefit from information about air pollution health risks and impacts, which include respiratory and cardiovascular diseases and premature death. Several computer-based tools help automate air pollution health impact assessments and are being used for a variety of contexts. Expanding information gathered for a May 2014 World Health Organization expert meeting, we survey 12 multinational air pollution health impact assessment tools, categorize them according to key technical and operational characteristics, and identify limitations and challenges. Key characteristics include spatial resolution, pollutants and health effect outcomes evaluated, and method for characterizing population exposure, as well as tool format, accessibility, complexity, and degree of peer review and application in policy contexts. While many of the tools use common data sources for concentration-response associations, population, and baseline mortality rates, they vary in the exposure information source, format, and degree of technical complexity. We find that there is an important tradeoff between technical refinement and accessibility for a broad range of applications. Analysts should apply tools that provide the appropriate geographic scope, resolution, and maximum degree of technical rigor for the intended assessment, within resources constraints. A systematic intercomparison of the tools' inputs, assumptions, calculations, and results would be helpful to determine the appropriateness of each for different types of assessment. Future work would benefit from accounting for multiple uncertainty sources and integrating ambient air pollution health impact assessment tools with those addressing other related health risks (e.g., smoking, indoor pollution, climate change, vehicle accidents, physical activity).
Tropospheric Ozone has a damaging effect on vegetation, where it inhibits growth and reduces yiel... more Tropospheric Ozone has a damaging effect on vegetation, where it inhibits growth and reduces yield of crop production, as well as causing visible damage to plant leaves. The reduced crop production and growth of forest trees can be assessed using species specific sensitivity factors and market prices. The damages to agriculture are severe and a treat to food security. However, anthropogenic emissions of air pollution are not causing ozone damage to vegetation locally because of redox titration of ozone in the pollution source area. The ozone damage is taking effect hundreds of kilometers further downwind, where the atmospheric content of ozone has stabilized. This means that ozone damage can have a large effect outside an emitting country's borders, while the effects inside are limited or even have reducing effects of ozone damage from other sources. As part of CEEH (Centre for energy, environment and health), we are assessing ozone damage to forest and vegetation in European co...
Springer Proceedings in Complexity, 2016
Mathematical transport-chemistry models are strong tools for evaluation of emission reduction str... more Mathematical transport-chemistry models are strong tools for evaluation of emission reduction strategies, for providing information to the public, and as the central part of models for human exposure to air pollution. NERI's recently developed AirGIS is an example of such a system. An air pollution forecasting system THOR has been established and provides 72-h air pollution forecasts two to four times a day. The THOR system generates forecasts for three different scales: rural areas, urban background and street level. Various human exposure studies have been carried out in Denmark and serve the basis for model development and validation. Recently monitoring of particulate matter has been included in these studies and preliminary results indicate that exposure to indoor air pollution plays an important role for the personal exposure to PM 2.5 .
Applied Parallel …, 1996
Page 1. Coupling the Advection and the Chemical Parts of Large Air Pollution Models J. Brandt 1 ,... more Page 1. Coupling the Advection and the Chemical Parts of Large Air Pollution Models J. Brandt 1 , I. Dimov , K. Georgiev , J. Wasniewski 3 and Z. Zlatev 1 ... The Silicon Graphics POWER CHALLENGE is a parallel machine with shared memory. ...
Atmospheric Chemistry and Physics, Nov 22, 2004
A new 3-D mercury model has been developed within the Danish Arctic Monitoring and Assessment Pro... more A new 3-D mercury model has been developed within the Danish Arctic Monitoring and Assessment Programme (AMAP). The model is based on the Danish Eulerian Hemispheric Model, which in the original version has been used to study the transport of SO2, SO42- and Pb into the Arctic. It was developed for sulphur in 1990 and in 1999 also lead was included. For the current study a chemical scheme for mercury has been included and the model is now applied to the mercury transport problem. Some experiments with the formulation of the mercury chemistry during the Polar Sunrise are carried out in order to investigate the observed depletion. Some of the main conclusions of the work described in this paper are that atmospheric transport of mercury is a very important pathway into the Arctic and that mercury depletion in the Arctic troposphere during the Polar Sunrise contributes considerably to the deposition of mercury in the Arctic.
Natural emissions play an important role in determining ambient levels of harmful atmospheric pol... more Natural emissions play an important role in determining ambient levels of harmful atmospheric pollutants, especially tropospheric ozone and particulate matter (PM). Natural sources have become more important with the ongoing reductions of anthropogenic emissions and are expected to be even more significant in the future in connection with a changing climate. Despite of the efforts made for modelling of natural emissions, the uncertainties and gaps with regard to investigation and quantification of these emissions are still quite large. In this study, the large-scale atmospheric chemistry transport model, DEHM (the Danish Eulerian Hemispheric Model) is further developed, evaluated and applied to study and quantify the contributions of many compounds from the natural sources to the concentration of ozone and formation of PM. The relative contributions are calculated for the domain covering more than the Northern Hemisphere for a typical year 2006. Natural source categories adopted in the recent model consist of vegetation, lightning, soils, wild animals and oceans. Here, DEHM has been further developed to include more natural emissions of biogenic volatile organic compounds (VOCs) as well as a scheme for describing secondary organic aerosols. Moreover, the parameterization used for estimating sea-salt generation has been modified to contain additional features. Evaluation of the modeled total fine PM, against observations, is conducted for both the previous and new model versions to assess improvement of the model performance with the updated description of natural emissions. Using the developed DEHM, our simulations indicate that at the Northern Hemisphere the contribution from natural emissions to the average annual ozone concentrations over land is between 4-30 ppbV. Among the natural emissions, biogenic VOCs are found to be the most significant contributors to ozone formation. Our results show that biogenic VOCs enhance the average ozone concentration with around 11% over land areas of the Northern Hemisphere. Similarly, the highest contribution of all the natural sources to total fine particles over land is observed in South America by about 74% and sea-salt aerosols found to play the most important role. However, over the rest of regions in the model domain the largest contribution from the natural sources to PM2.5 is due to wildfires. The contribution from natural emissions to the mean PM2.5 concentration over the land areas in the model domain is about 34%.
Journal of Computational Physics, 2002
A new 3-D model REGINA (REGIonal high resolutioN Air pollution model) is under development at the... more A new 3-D model REGINA (REGIonal high resolutioN Air pollution model) is under development at the National Environmental Research Institute (NERI). The model is based on models developed over the past decades at NERI. The goal is to obtain a nested model capable of high-resolution operation. To reach this goal it is necessary to implement sufficiently accurate numerical methods. The model will be applied to studying air pollution phenomena (monitoring, forecasting, and scenarios) over Denmark. In the present paper, the outline of the new model is presented. The numerical methods for transport and chemistry are described. The horizontal transport in the model is solved using an accurate space derivatives algorithm. This method traditionally requires periodic boundary conditions, which are not applicable for nested modeling. Therefore a new method for calculating nonperiodic boundary conditions has been developed. The numerical solution to the chemistry part of the model is obtained from an implementation of a new combination of two existing numerical methods. The results from extensive testing of the numerical solution of the advection and the coupling of the solution of advection and chemistry in the model using Molenkamp-Crowley rotation tests are presented. The same tests have been applied to the model with and without nesting. The results show that the numerical methods are suitable for modeling air pollution levels at high resolution.
A 3-d mercury model is in the progress of development. The model is based on the Danish Eulerian ... more A 3-d mercury model is in the progress of development. The model is based on the Danish Eulerian Hemispheric model, which in the original version have been used to study the transport of SO2, SO42- and Pb into the Arctic (see Christensen, 1997). The horizontal space of the model is defined on a regular 96x96 grid that covers most of the Northern Hemisphere with a grid-resolution of 150 km at 60oN. Meteoro-logical data are obtained from the European Centre for Medium-range Weather Forecasts (ECMWF) on a 2.5ox2.5o grid with a time resolution of 12 hours that are used as in- put to the MM5 mesoscale modelling system, which produce the final meteorological input for the DEHM model. The whole system includes also two-way nesting capa- bilities, so it is possible to do finer (150 km -> 50 km -> 16.67 km, etc) model calcu- lations over e.g. the Arctic Ocean or Greenland. In the current version the emissions of anthropogenic Mercury are based on the global inventory of Mercury emissions for 1995 on a 1ox1o grid (Pacyna et al, 2001). The chemistry is based on the scheme from the GKSS model (see Petersen et al, 1998). Some results from the model system will be presented with emphasizing on the simulation of the mercury depletion in the Arctic during the Polar Sunrise.
Transport and Chemical Transformation in the Troposphere, 2001
With a specific focus on Europe as part of the AEROCARB/CARBO-EUROPE project, we use atmospheric ... more With a specific focus on Europe as part of the AEROCARB/CARBO-EUROPE project, we use atmospheric models to assess the monthly sources and sinks of atmospheric CO2 for the year 1998. A Bayesian inverse approach is used (top-down) where the spread between modelled and measured CO2 concentrations in the atmosphere is minimised. We divide Europe into as much as 26 regions
A new model system for mapping and forecasting nitrogen deposition to the Baltic Sea has been dev... more A new model system for mapping and forecasting nitrogen deposition to the Baltic Sea has been developed. The system is based on the Lagrangian variable scale transport-chemistry model ACDEP (Atmospheric Chemistry and Deposition model), and aims at delivering deposition estimates to be used as input to marine ecosystem models. The system is tested by comparison of model results to measurements from monitoring stations around the Baltic Sea. The comparison shows that observed annual mean ambient air concentrations and wet depositions are well reproduced by the model. Diurnal mean concentrations of NH x (sum of NH 3 and NH + 4 ) and NO 2 are fairly well reproduced, whereas concentrations of total nitrate (sum of HNO 3 and NO − 3 ) are somewhat overestimated. Wet depositions of nitrate and ammonia are fairly well described for annual mean values, whereas the discrepancy is high for the monthly mean values and the wet depositions are rather poorly described concerning the diurnal mean values. The model calculations show that the annual atmospheric nitrogen deposition has a pronounced south-north gradient with depositions in the range about 1.0 T N km −2 in the south and 0.2 T N km −2 in the north. The results show that in 1999 the maximum diurnal mean deposition to the Danish waters appeared during the summer in the algae growth season. For the northern parts of the Baltic the highest depositions were distributed over most of the year. Total deposition to the Baltic Sea was for the year 1999 estimated to 318 kT N for an area of 464 406 km 2 equivalent to an average deposition of 684 kg N/km 2 .
Data assimilation can be used with air quality models to improve historical simulations or initia... more Data assimilation can be used with air quality models to improve historical simulations or initial conditions for forecasts. The ensemble Kalman filter is an assimilation technique that uses a low-dimensional representation of the background error covariances. We have coupled an offline chemical transport model, the DEHM (the Danish Eulerian hemispheric model), with an asynchronous ensemble Kalman filter (AEnKF), which accounts for timing discrepancies between observation and the analysis time. We will present the structure and initial results using this simulation-assimilation framework. To evaluate the DEHM-AEnKF system, we assimilated a single species, carbon monoxide. Carbon monoxide is a moderately long-lived atmospheric trace gas, and its concentration is measured routinely from a number of different measurement platforms. The chemistry of CO is simpler than other well-studied species (e.g., ozone). Thus CO is a good candidate species for the initial testing of a chemical data...
Large ozone concentrations have harmful effects on forests and crops when these exceed some criti... more Large ozone concentrations have harmful effects on forests and crops when these exceed some critical levels. It is believed that the damages in USA due to high ozone concentrations exceed several billions dollars. Therefore it is worthwhile to investigate different actions that could be applied in the attempts to reduce the harmful effects. One needs reliable mathematical models in such studies. Reliable models are normally very big and it is difficult to treat them numerically, because they lead, after some kind of discretization and after the implementation of some appropriate splitting procedure, to several very huge systems of ordinary differential equations (up to order of 106). Moreover, these systems have to be treated numerically during many time-steps (typically several thousand time-steps per run are necessary). The use of modern parallel and/or vector machines is an important condition in the efforts to handle successfully big air pollution models. If the numerical algori...
International Journal of Computational Science and Engineering, 2007
... This is a major part of the computational work and is based on scheme described in Section 3.... more ... This is a major part of the computational work and is based on scheme described in Section 3. Let us reiterate here that ... 7 Numerical examples ... The first example is a linear first-oder PDE, which is in some sense similar to the problems arising in the advection sub-model when ...
Flood forecasting specialists and operational water managers require ready access to a wide range... more Flood forecasting specialists and operational water managers require ready access to a wide range of information including both current and forecasted meteorological conditions, and current and forecasted hydrological conditions to make decisions to initiate flood response measures or to issue flood warnings. Effective flood forecasting systems must provide reliable, accurate and timely forecasts for a range of catchments; from small rapidly responding upstream catchments to larger, more slowly responding downstream locations, often within the same region. Using meteorological observations and quantitative precipitation forecasts to produce hydrological flood forecasts provides valuable increases in lead-time that can be exploited to mitigate the effects of extreme floods. However while the value of accurate meteorological and hydrological forecasts are widely recognised real-time flood management decisions must be based on an understanding of the uncertainties and associated risks....
Physics and Chemistry of the Earth, Parts A/B/C, 2002