Filip Lefebre

The 1979–2005 Greenland Ice Sheet Melt Extent from Passive Microwave Data Using an Improved Version of the Melt Retrieval XPGR Algorithm

Analysis of passive microwave satellite observations over the Greenland ice sheet reveals a significant increase in surface melt over the period 1979-2005. Since 1979, the total melt area was found to have increased by +1.22 x 10(7) km(2). An improved version of the cross-polarized gradient ratio (XPGR) technique is used to identify the melt from the brightness temperatures. The improvements in the melt retrieval XPGR algorithm as well as the surface melt acceleration are discussed with results from a coupled atmosphere-snow regional climate model. From 1979 to 2005, the ablation period has been increasing everywhere over the melt zone except in the regions where the model simulates an increased summer snowfall. Indeed, more snowfall in summer decreases the liquid water content of the snowpack, raises the albedo and therefore reduces the melt. Finally, the observed melt acceleration over the Greenland ice sheet is highly correlated with both Greenland and global warming suggesting a continuing surface melt increase in the future.

Modelling changes of aerosol compositions over Belgium and Europe

Seasonal changes in aerosol compositions over Belgium and Europe are simulated with an extended version of the EUROS model. EUROS is capable of modelling mass and chemical composition of aerosols in two size fractions (PM2.5 and PM10-2.5). The chemical composition is expressed in terms of seven components: ammonium, nitrate, sulphate, primary inorganic compounds, elementary carbon, primary organic compounds and Secondary Organic Compounds (SOA). A comparison of modelled and measured aerosol concentrations showed that modelled concentrations are generally consistent with observed concentrations. The chemical composition of the aerosol showed a strong dependence on the season. High aerosol concentrations during the summer were mainly due to high concentrations of the secondary components nitrate, ammonium, sulphate and SOA in the size fraction PM2.5. In contrast, during autumn and winter, increased PM-concentrations were mainly due to higher concentrations of primary components, especially in the size fraction PM10-2.5.

Making High Resolution Air Quality Maps for Flanders, Belgium

Using a combination of models, high resolution air quality maps for Flanders (Belgium) have been made. First of all, the Eulerian air quality model AURORA has simulated for a complete year the air pollutant concentrations over the region on a 3 × 3 km² resolution. These results are calibrated using the RIO-interpolation model on air quality station data. Thereafter, an extra simulation using the bi-Gaussian IFDM model is made on a resolution of 1 × 1 km², with a finer resolution (up to 25 m) close to the major roads. The nesting methodology of IFDM in AURORA is designed to avoid double counting of the roads. The results are highly detailed PM10, PM2.5, NO2 and EC maps for Flanders. Using station data and data from several measurement campaigns, the maps have been validated and it has been shown that the maps show indeed a highly detailed picture of the air quality in Flanders. These data will be used in assessing the air quality and human exposure to it in Flanders, and in assessing policy scenarios designed to improve the air quality.

Evaluation of Aurora Simulated Benzene Concentrations for the Urban Area of Antwerp

Urban air quality is a major topic in the European environmental policy because more than 70 % of the European inhabitants and a major part of the working places are located inside an urbanized area. This leads to increased levels of human exposure to harmful air pollutants such as ground-level ozone, nitrogen dioxide, volatile organic components and fine particles. In particular, the road traffic emitted BTEX-aromatics (Benzene-Toluene-Ethylbenzene and Xylene) are characteristic for local urban air pollution. Moreover, benzene is highly carcinogenic and therefore an annual averaged limit value of 5 μg m-3 has been set in the framework of the Air Quality Framework Directives 96/62/EC and 2000/69/EC (WHO, 2000). This limit value should be obtained in 2010. Traffic related benzene concentrations are controlled by the petrol composition, the car park composition and traffic speed as well as the atmospheric conditions.

Chapter 5.4 Modelling seasonal changes of aerosol compositions over Belgium and Europe

Abstract The EUROpean Smog model (EUROS) was extended with two special modular algorithms for atmospheric particles. The first module is the Caltech Atmospheric Chemistry Mechanism (CACM) which describes in a mechanistic way the formation of precursors of secondary organic aerosols. The second module is the Model of Aerosol Dynamics, Reaction, Ionization and Dissolution (MADRID 2), which describes the formation of secondary aerosols by means of an equilibrium between the gas phase and the aerosol phase. It includes inorganic as well as hydrophilic and hydrophobic organic compounds. Through this extension, the EUROS model was able to model mass and chemical composition of aerosols in two size fractions (PM 2.5 and PM 10-2.5 ). The model was validated for 3 seasonal episodes in 2002 and 2003. A comparison between modelled and observed aerosol concentrations showed that the trends in PM 10 concentrations are well captured. A strong seasonal dependency was found in the chemical composition of the aerosols. Large contributions of secondary inorganic components were found for summer episodes with high aerosol concentrations, whereas during autumn/winter episodes the concentrations of secondary aerosol were less abundant.

Assessment of different land use development scenarios in terms of traffic flows and associated air quality

Compact and polycentric city forms are associated with minimal consumption of land and energy, and are often promoted as the more sustainable and hence preferred mode of urban development. In this context, a series of numerical simulations was performed to evaluate the impact of two urban development scenarios on air quality and related human exposure. The area that was selected consists of a highly urbanised region in the Ruhr area, located in the north-western part of Germany in central North Rhine-Westphalia with a total population in excess of 5.5 million. The choice for this particular area was mainly motivated by its size and importance, as well as its conversion potential. Two distinct scenarios were selected. The first is referred to as ‘urban sprawl’ and is characterized by a significant increase in built-up surface. This scenario supposes a continuation of the current process of people leaving the highly occupied central part of the study area to settle in the greener surroundings. In the second scenario, referred to as ‘satellite cities’, persons and jobs were displaced to five existing towns located near the core of the urban area. Models dealing with land use, traffic flows, and atmospheric dispersion were applied, first under conditions representative of the urbanised area as it is today. Subsequently, the urban development scenarios were implemented using spatial modelling techniques, and the impact of the scenarios with respect to air quality was evaluated, including an estimate of human exposure to air pollution and the associated external costs.

Developments and Applications in Urban Air Pollution Modelling

An integrated assessment approach is presented to evaluate the impact of abatement strategies and mobility scenarios on transport emissions and urban air quality. The system consists of a set of flexible models that can be connected in a modular way within the framework of the impact pathway methodology. The MIMOSA model is used to evaluate road transport emissions. The AURORA model is used for urban air quality assessment and management. The evaluation of health impacts and environmental damage costs is carried out by applying the ExternE methodology.

AURORA: An Air Quality Model For Urban Regions Using An Optimal Resolution Approach

For the assessment of air quality in cities, we developed an integrated model system, known as AURORA (Air quality modelling in Urban Regions using an Optimal Resolution Approach). This urban air quality management system has been designed for urban and regional policy support and reflects the state-of-the-art in air quality modelling, using fast and advanced numerical techniques. Modules for meteorological input data, emissions, advection, diffusion and chemistry have been designed, tested and coupled through a user interface. The model system is implemented in the cities Antwerp and Hasselt (B) and is being applied in various EU 5th framework projects (BUGS, DECADE).