Ammonia Concentrations Over Europe – Application of the WRF-Chem Model Supported With Dynamic Emission

The study focuses on the application of a static and dynamic ammonia emission based on a Europe-wide default setting into the Weather Research and Forecasting Chemistry model (WRF-Chem) and the influence on the simulated ammonia concentrations and the overall model performance. The WRF-Chem model was run twice for the entire Europe at a spatial resolution of 36 x 36 km for the year 2012. In the first simulation we used a static emission approach (the “BASE” simulation), whereas in the second simulation, dynamic ammonia emissions were used (the “DYNAMIC” simulation). Both simulations underestimate measured concentrations of NH3 for all seasons, have similar NMGE (about 0.7 μg m-3) and modelled hourly ammonia peaks are shifted towards the afternoon hours if compared with measurements. However, for all temporal resolutions, normalised mean gross error in winter and summer is lower for DYNAMIC than for BASE. The DYNAMIC simulation also generally gives worse performance in spring for each temporal resolution. For further improvement of the modelled ammonia concentrations with WRF-Chem we suggest to use a nested approach with higher spatial resolution, which will lead to better separation of the ammonia source regions from surrounding areas, and take into account national practice and regulations in the emission model, eventually only in the nested model domain

Spatial, Temporal and Vertical Distribution of Ammonia Concentrations Over Europe – Comparing a Static and Dynamic Approach With WRF-Chem

The study focuses on the application of a dynamic ammonia emission into the Weather Research and Forecasting Chemistry model (WRF-Chem) and the influence on the simulated ammonia concentrations and the overall model performance. We have focused on agricultural ammonia sources and have analysed both hourly and daily patterns of ammonia emissions and concentrations at measurement sites located in agricultural areas or influenced by this activity. For selected episodes, we have also investigated the 3-D patterns of the ammonia concentrations in the atmosphere. The application of the dynamic ammonia emission into the WRF-Chem model (the “DYNAMIC” simulation) results in an improvement of the modelled daily ammonia concentrations in comparison to a static approach (the “BASE” simulation), which is currently widely used in chemical transport models. In the case of hourly resolution, we have observed an improvement for the DYNAMIC approach for the winter and autumn seasons, but for the entire year the modelled hourly ammonia peaks are shifted toward the afternoon hours if compared with measurements. This study indicates that the current description of the diurnal cycle of the ammonia concentration from fields is not accurate and more research is needed in order to improve the processes that describe the emission from fertilised fields. The results suggest that the governing processes in relation to the diurnal cycle are the atmospheric mixing and the emission strength. Therefore,an improved description of the diurnal profile of ammonia concentrations within atmospheric models requires a better description of the planetary boundary layer height and a stronger daily pattern of ammonia emission, e.g. through increased evaporation or increased fluxes from the surface

Modelling atmospheric transport of ?-hexachlorocyclohexane in the Northern Hemispherewith a 3-D dynamical model: DEHM-POP

International audienceThe Danish Eulerian Hemispheric Model (DEHM) is a 3-D dynamical atmospheric transport model originally developed to describe the atmospheric transport of sulphur into the Arctic. A new version of the model, DEHM-POP, developed to study the atmospheric transport and environmental fate of persistent organic pollutants (POPs) is presented. During environmental cycling, POPs can be deposited and re-emitted several times before reaching a final destination. A description of the exchange processes between the land/ocean surfaces and the atmosphere is included in the model to account for this multi-hop transport. The ?-isomer of the pesticide hexachlorocyclohexane (?-HCH) is used as tracer in the model development. The structure of the model and processes included are described in detail. The results from a model simulation showing the atmospheric transport for the years 1991 to 1998 are presented and evaluated against measurements. The annual averaged atmospheric concentration of ?-HCH for the 1990s is well described by the model; however, the shorter-term average concentration for most of the stations is not well captured. This indicates that the present simple surface description needs to be refined to get a better description of the air-surface exchange processes of POPs

Modelling atmospheric transport of persistent organic pollutants in the Northern Hemisphere with a 3-D dynamical model: DEHM-POP

International audienceThe Danish Eulerian Hemispheric Model (DEHM) is a 3-D dynamical atmospheric transport model originally developed to describe the atmospheric transport of sulphur into the Arctic. A new version of the model, DEHM-POP, developed to study the atmospheric transport and environmental fate of persistent organic pollutants (POPs) is presented. During environmental cycling, POPs can be deposited and re-emitted several times before reaching a final destination. A description of the exchange processes between the land/ocean surfaces and the atmosphere is included in the model to account for this multi-hop transport. The ?-isomer of the pesticide hexachlorocyclohexane (?-HCH) is used as tracer in the model development. The structure of the model and processes included are described in detail. The results from a model simulation showing the atmospheric transport for the years 1991 to 1998 are presented and evaluated against measurements. The annual averaged atmospheric concentration of ?-HCH for the 1990s is well described by the model; however, the shorter-term average concentration for most of the stations is not well captured. This indicates that the present simple surface description needs to be refined to get a better description of the air-surface exchange proceses of POPs

Conceptualising connections: energy demand, infrastructures and social practices

Problems of climate change present new challenges for social theory. In this paper we focus on the task of understanding and analysing car dependence, using this as a case through which to introduce and explore what we take to be central but underdeveloped questions about how infrastructures and complexes of social practice connect across space and time. In taking this approach we work with the proposition that forms of energy consumption, including those associated with automobility, are usefully understood as outcomes of interconnected patterns of social practices, including working, shopping, visiting friends and family, going to school and so forth. We also acknowledge that social practices are partly constituted by, and always embedded in material arrangements. Linking these two features together we suggest that forms of car-dependence emerge through the intersection of infrastructural arrangements that are integral to the conduct of many practices at once. We consequently explore the significance of professional – and not only ‘ordinary’ – practices, especially those of planners and designers who are involved in reconfiguring infrastructures of different scales, and in the practice dynamics that follow

Impacts of climate change on air pollution levels in the Northern Hemisphere with special focus on Europe and the Arctic

International audienceThe response of a selected number of chemical species is inspected with respect to climate change. The coupled Atmosphere-Ocean General Circulation Model ECHAM4-OPYC3 is providing meteorological fields for the Chemical long-range Transport Model DEHM. Three selected decades (1990s, 2040s and 2090s) are inspected. The 1990s are used as a reference and validation period. In this decade an evaluation of the output from the DEHM model with ECHAM4-OPYC3 meteorology input data is carried out. The model results are tested against similar model simulations with MM5 meteorology and against observations from the EMEP monitoring sites in Europe. The test results from the validation period show that the overall statistics (e.g. mean values and standard deviations) are similar for the two simulations. However, as one would expect the model setup with climate input data fails to predict correctly the timing of the variability in the observations. The overall performance of the ECHAM4-OPYC3 setup as meteorological input to the DEHM model is shown to be acceptable according to the applied ranking method. It is concluded that running a chemical long-range transport model on data from a "free run" climate model is scientifically sound. From the model runs of the three decades, it is found that the overall trend detected in the evolution of the chemical species, is the same between the 1990 decade and the 2040 decade and between the 2040 decade and the 2090 decade, respectively. The dominating impacts from climate change on a large number of the chemical species are related to the predicted temperature increase. Throughout the 21th century the ECHAM4-OPYC3 projects a global mean temperature increase of 3 K with local maxima up to 11 K in the Arctic winter based on the IPCC A2 emission scenario. As a consequence of this temperature increase, the temperature dependent biogenic emission of isoprene is predicted to increase significantly over land by the DEHM model. This leads to an increase in the O3 production and together with an increase in water vapor to an increase in the number of free OH radicals. Furthermore this increase in the number of OH radicals contributes to a significant change in the typical life time of many species, since OH are participating in a large number of chemical reactions. It is e.g. found that more SO42? will be present in the future over the already polluted areas and this increase can be explained by an enhanced conversion of SO2 to SO42?

Decarbonisation and its discontents: a critical energy justice perspective on four low-carbon transitions

Low carbon transitions are often assumed as normative goods, because they supposedly reduce carbon emissions, yet without vigilance there is evidence that they can in fact create new injustices and vulnerabilities, while also failing to address pre-existing structural drivers of injustice in energy markets and the wider socio-economy. With this in mind, we examine four European low-carbon transitions from an unusual normative perspective: that of energy justice. Because a multitude of studies looks at the co-benefits renewable energy, low-carbon mobility, or climate change mitigation, we instead ask in this paper: what are the types of injustices associated with low-carbon transitions? Relatedly, in what ways do low-carbon transitions worsen social risks or vulnerabilities? Lastly, what policies might be deployed to make these transitions more just? We answer these questions by first elaborating an “energy justice” framework consisting of four distinct dimensions—distributive justice (costs and benefits), procedural justice (due process), cosmopolitan justice (global externalities), and recognition justice (vulnerable groups). We then examine four European low-carbon transitions—nuclear power in France, smart meters in Great Britain, electric vehicles in Norway, and solar energy in Germany—through this critical justice lens. In doing so, we draw from original data collected from 64 semi-structured interviews with expert partisans as well as five public focus groups and the monitoring of twelve internet forums. We document 120 distinct energy injustices across these four transitions, including 19 commonly recurring injustices. We aim to show how when low-carbon transitions unfold, deeper injustices related to equity, distribution, and fairness invariably arise

Modelling societal transitions with agent transformation

Transition models explain long-term and large-scale processes fundamentally changing the structure of a societal system. Our concern is that most transition models are too static. Although they capture a move of focus from static equilibria to transitions between dynamic equilibria, they are still rooted in an "equilibriumist" approach. Improvement is possible with agent-based models that give attention to endogenous system processes called "transformation processes". These models can render far more dynamic pictures of societal systems in transition, and are no longer remote from descriptions in the emerging transition literature

Varied sensitivity to therapy of HIV-1 strains in CD4+ lymphocyte sub-populations upon ART initiation

<p>Abstract</p> <p>Background</p> <p>Although antiretroviral therapy (ART) has proven its success against HIV-1, the long lifespan of infected cells and viral latency prevent eradication. In this study we analyzed the sensitivity to ART of HIV-1 strains in naïve, central memory and effector memory CD4⁺lymphocyte subsets.</p> <p>Methods</p> <p>From five patients cellular HIV-1 infection levels were quantified before and after initiation of therapy (2-5 weeks). Through sequencing the C2V3 region of the HIV-1 gp120 envelope, we studied the effect of short-term therapy on virus variants derived from naïve, central memory and effector memory CD4⁺lymphocyte subsets.</p> <p>Results</p> <p>During short-term ART, HIV-1 infection levels declined in all lymphocyte subsets but not as much as RNA levels in serum. Virus diversity in the naïve and central memory lymphocyte populations remained unchanged, whilst diversity decreased in serum and the effector memory lymphocytes. ART differentially affected the virus populations co-circulating in one individual harboring a dual HIV-1 infection. Changes in V3 charge were found in all individuals after ART initiation with increases within the effector memory subset and decreases found in the naïve cell population.</p> <p>Conclusions</p> <p>During early ART virus diversity is affected mainly in the serum and effector memory cell compartments. Differential alterations in V3 charge were observed between effector memory and naïve populations. While certain cell populations can be targeted preferentially during early ART, some virus strains demonstrate varied sensitivity to therapy, as shown from studying two strains within a dual HIV-1 infected individual.</p