Lise Marie Frohn

Operational air pollution forecasts from European to local scale

Abstract A new operational air pollution forecast system, THOR, has been developed at the National Environmental Research Institute, Denmark. The integrated system consists of a series of air pollution models, covering a wide range of scales (from European scale to street scale in cities) and applications. The system is designed to automatically produce 3 days air pollution forecasts of the most important air pollution species on different scales on a continuous basis. The various models, the coupling/integration and the configuration of the models, the visualizations and the real-time performance on fast workstations with parallel architecture will be described. Some examples of model results and validations on street level are presented.

Comparison of five eulerian air pollution forecasting systems for the summer of 1999 using the German ozone monitoring data

Eulerian state-of-the-art air pollution forecasting systems on the European scale are operated routinely by several countries in Europe. DWD and FUB, both Germany, NERI, Denmark, NILU, Norway, and SMHI, Sweden, operate some of these systems. To apply such modeling systems, e.g. for regulatory purposes according to new EU directives, an evaluation and comparison of the model systems is fundamental in order to assess their reliability. One step in this direction is presented in this study: The model forecasts from all five systems have been compared to measurements of ground level ozone in Germany. The outstanding point in this investigation is the availability of a huge amount of data – from forecasts by the different model systems and from observations. This allows for a thorough interpretation of the findings and assures the significance of the observed features. Data from more than 300 measurement stations for a 5-month period (May–September 1999) of the German monitoring networks have been used in this comparison. Different spatial and temporal statistical parameters were applied in the evaluation. Generally, it was found that the most comprehensive models gave the best results. However, the less comprehensive and computational cheaper models also produced good results. The extensive comparison made it possible to point out weak points in the different models and to describe the individual model behavior for a full summer period in a climatological sense. The comparison also gave valuable information for an assessment of individual measurement stations and complete monitoring networks in terms of the representativeness of the observation data.

Assessment of the atmospheric nitrogen and sulphur inputs into the North Sea using a Lagrangian model

The atmospheric chemistry and deposition model has been applied for calculation of nitrogen and sulphur depositions to the entire North Sea area for the year 1999. The total atmospheric nitrogen and sulphur depositions to the North Sea area were determined to 709 kton (kt) N and 551 kt S, respectively. Since the North Sea area was calculated to be 747,988 km2, this is equivalent to an average deposition of 0.9 ton N km-2 and 0.7 ton S km-2, respectively. The depositions decrease strongly from the south end (about 2-3 kt N km-2) to the north end (about 0.2 kt N km-2) of the North Sea, due to increasing distance to the large source areas in the northern part of the European continent. The territorial waters of Belgium, the Netherlands and Germany receive about 50% higher deposition densities than the average value for the entire North Sea area. For the remaining territorial waters of the North Sea the depositions follow more or less the fraction of the area. The results furthermore show that about 60% of the total nitrogen deposition is related to emissions from combustion sources (nitrogen oxides) and about 40% from emissions related to agricultural activities (ammonia).

Modelling Nitrogen Deposition on a Local Scale—A Review of the Current State of the Art

Abstract. Local ammonia emissions from agricultural activities are often associated with high nitrogen deposition in the close vicinity of the sources. High nitrogen (N) inputs may significantly affect the local ecosystems. Over a longer term, high loads may change the composition of the ecosystems, leading to a general decrease in local biodiversity. In Europe there is currently a significant focus on the impact of atmospheric N load on local ecosystems among environmental managers and policy makers. Model tools designed for application in N deposition assessment and aimed for use in the regulation of anthropogenic nitrogen emissions are, therefore, under development in many European countries. The aim of this paper is to present a review of the current understanding and modelling parameterizations of atmospheric N deposition. A special focus is on the development of operational tools for use in environmental assessment and regulation related to agricultural ammonia emissions. For the often large number of environmental impact assessments needed to be carried out by local environmental managers there is, furthermore, a need for simple and fast model systems. These systems must capture the most important aspects of dispersion and deposition of N in the nearby environment of farms with animal production. The paper includes a discussion on the demands on the models applied in environmental assessment and regulation and how these demands are fulfilled in current state-of-the-art models.

Atmospheric input of nitrogen into the North Sea: ANICE project overview.

The aim of the atmospheric nitrogen inputs into the coastal ecosystem (ANICE) project is to improve transport-chemistry models that estimate nitrogen deposition to the sea. To achieve this, experimental and modelling work is being conducted which aims to improve understanding of the processes involved in the chemical transformation, transport and deposition of atmospheric nitrogen compounds. Of particular emphasis within ANICE is the influence of coastal zone processes. Both short episodes with high deposition and chronic nitrogen inputs are considered in the project. The improved transport-chemistry models will be used to assess the atmospheric inputs of nitrogen compounds into the European regional seas (the North Sea is studied as a prototype) and evaluate the impact of various emission reduction strategies on the atmospheric nitrogen loads. Assessment of the impact of atmospheric nitrogen on coastal ecosystems will be based on comparisons of phytoplankton nitrogen requirements, other external nitrogen inputs to the ANICE area of interest and the direct nitrogen fluxes provided by ANICE. Selected results from both the experimental and modelling components are presented here. The experimental results show the large spatial and temporal variability in the concentrations of gaseous nitrogen compounds, and their influences on fluxes. Model calculations show the strong variation of both concentrations and gradients of nitric acid at fetches of up to 25km. Aerosol concentrations also show high temporal variability and experimental evidence for the reaction between nitric acid and sea salt aerosol is provided by size-segregated aerosol composition measured at both sides of the North Sea. In several occasions throughout the experimental period, air mass back trajectory analysis showed connected flow between the two sampling sites (the Weybourne Atmospheric Observatory on the North Norfolk coast of the UK and Meetpost Noordwijk, a research tower at 9km off the Dutch coast). Results from the METRAS/SEMA mesoscale chemistry transport model system for one of these cases are presented. Measurements of aerosol and rain chemical composition, using equipment mounted on a commercial ferry, show variations in composition across the North Sea. These measurements have been compared to results obtained with the transport-chemistry model ACDEP which calculates the atmospheric inputs into the whole North Sea area. Finally, the results will be made available for the assessment of the impact of atmospheric nitrogen on coastal ecosystems.

Integrated air-quality monitoring - combined use of measurements and models in monitoring programmes

Environmental context. Optimisation of allocated resources, improved quality, and better understanding of processes – these are the main advantages of applying integrated monitoring (IM). The paper describes IM as a combination of air pollution measuring and modelling, and describes how it is implemented in air-quality management in Denmark. However, the IM concept may also be applied to follow air-quality levels in other countries that currently do not have a corresponding system. It may also be applied to the environmental monitoring of other compartments. Abstract. Integrated air-quality monitoring (IM) is here defined as monitoring based on the combination of results of atmospheric measurements from usually fixed site stations, and results obtained from calculations with air-quality models. This paper outlines experience from the use of IM at the National Environmental Research Institute (NERI) within the two nationwide air-quality monitoring programmes for the Danish urban and rural environments, respectively. The measurements in these Danish monitoring programmes are used to determine actual levels and trends in pollutant concentrations and depositions of pollutants. The measurements are further used for process understanding, and for the development and validation of air-quality models. The results from the air-quality models are used in the interpretation of measurements, but they are also used to provide information about, for example, source apportionment. The model calculations are used to extend the geographical coverage of the monitoring, and to provide information about pollution loads at locations or regions that are not well covered by the limited number of measurement stations in the monitoring programmes. Finally, the air-quality models are applied to carry out scenario studies of future pollution loads, e.g. assessment of the effects of various emission reduction strategies. NERI operates and holds the overall responsibility for the Danish air-quality monitoring programmes. These monitoring programmes are designed to fulfil the Danish obligations in relation to the EU directives on air quality, as well as the Danish obligations in relation to the reporting of data to international organisations (EMEP, HELCOM, OSPARCOM, and WHO). The obtained results from the use of IM form the basis for the national assessment of the air pollution loads in relation to protection of the aquatic and terrestrial environment; in these assessments the use of IM plays a central role.

Development of a high resolution integrated nested model for studying air pollution in Denmark

Abstract A 3-D Eulerian transport-chemistry model, REGINA (REGIonal high resolutionN Air pollution model), based on models developed over the last decade at the National Environmental Research Institute (DREAM, DEHM, ACDEP and DEOM) is currently under development. The model will be applied to studies of air pollution phenomena (both monitoring, forecasts and scenarios) over Denmark, where there are extensive coastal areas that require a high resolution model in order to resolve the effects of e.g. land-sea interactions. The goal is to obtain a nested grid model capable of high resolution operation. It is very important to implement numerical methods suited for the high model resolution in order to make sure that significant errors are not introduced by the numerics. In this paper the model concepts of REGINA will be described. Special attention will be on the numerical methods and numerical test results concerning the advection and chemistry. Furthermore examples of model results and some preliminary validations with measurements from EMEP will be shown. The numerical test results show, that the methods chosen for the model are very accurate with small numerical errors. The next step will be to implement high resolution input data (emission, land use and meteorological data) and physical parameterisations.

Deposition of nitrogen into the North Sea

The flux of nitrogen species from the atmosphere into the ocean, with emphasis on coastal waters, was addressed during the ANICE project (Atmospheric Nitrogen Inputs into the Coastal Ecosystem). ANICE focused on quantifying the deposition of atmospheric inputs of inorganic nitrogen compounds (HNO3, NO3-, NH3 and NH4+) into the North Sea and the processes governing this deposition. The Southern North Sea was studied as a prototype. Because the physical and chemical processes are described, as opposed to empirical relations, the results can potentially be transferred to other regional seas like the Mediterranean, the North Atlantic continental shelf area and the Baltic. Two intensive field experiments were undertaken, centred around the offshore tower Meetpost Noordwijk and the Weybourne Atmospheric Observatory in East Anglia (UK). Long-term measurements were made on a ferry sailing between Hamburg and Harwich/Newcastle. These measurements provided data for sensitivity studies of a variety of problems associated with the coastal region that are not easily evaluated with larger scale models, to constrain models and to test model results. Concentrations of nitrogen compounds over the North Sea and the resulting deposition presented in this paper were obtained with the Lagrangian transport-chemistry model ACDEP. The average annual deposition in 1999 was 906kg Nkm-2. The results are compared with experimental data from the ferry. Effects of temporal and spatial variations are evaluated based on experimental results and small-scale model studies. In particular, effects of the aerosol size distribution on the nitrogen deposition are discussed.

Operational air pollution forecasts from regional scale to urban street scale. Part 2: performance evaluation

Abstract An operational air pollution forecast model system has been developed. The model system includes several models capable of calculating air pollution concentrations at different spatial scales, from European scale over urban background scale to urban street scale. The air pollution models are driven by the numerical weather forecast model, the ETA model. Operational 3 days air pollution forecasts are produced 4 times a day. Model results from the air pollution models and the weather forecast model have been compared to measurements from the Danish urban monitoring network. The performance with respect to mean values, temporal variability and daily maximum of air pollution levels, are evaluated.

Operational air pollution forecasts from regional scale to urban street scale. Part 1: system description

Abstract A new integrated operational air pollution forecast system, the DMU-ATMI THOR air pollution forecast system, has been developed. The integrated model system consist of a weather forecast model and a series of air pollution models, covering a wide range of scales (European scale, urban background scale and street scale in cities) and applications (forecasting, monitoring and scenarios). The system is designed to automatically produce 3 days air pollution forecasts of some of the most important air pollution species on different scales and on a continuous basis. The various models, the coupling/integration and the configuration of the models will be described. The model results have been compared to measurements from the Danish rural and urban monitoring networks in the paper “Performance evaluation of regional and urban air pollution forecasts” (Brandt, this issue)