Attribution of ground-level ozone to anthropogenic and natural sources of nitrogen oxides and reactive carbon in a global chemical transport model

We perform a source attribution for tropospheric and ground-level ozone using a novel technique that accounts separately for the contributions of the two chemically distinct emitted precursors (reactive carbon and oxides of nitrogen) to the chemical production of ozone in the troposphere. By tagging anthropogenic emissions of these precursors according to the geographical region from which they are emitted, we determine source-receptor relationships for ground-level ozone. Our methodology reproduces earlier results obtained via other techniques for ozone source attribution, and it also delivers additional information about the modelled processes responsible for the intercontinental transport of ozone, which is especially strong during the spring months. The current generation of chemical transport models used to support international negotiations aimed at reducing the intercontinental transport of ozone shows especially strong inter-model differences in simulated springtime ozone. Current models also simulate a large range of different responses of surface ozone to methane, which is one of the major precursors of ground-level ozone. Using our novel source attribution technique, we show that emissions of NOx (oxides of nitrogen) from international shipping over the high seas play a disproportionately strong role in our model system regarding the hemispheric-scale response of surface ozone to changes in methane, as well as to the springtime maximum in intercontinental transport of ozone and its precursors. We recommend a renewed focus on the improvement of the representation of the chemistry of ship NOx emissions in current-generation models. We demonstrate the utility of ozone source attribution as a powerful model diagnostic tool and recommend that similar source attribution techniques become a standard part of future model intercomparison studies

A comparison of long-term trends in observations and emission inventories of NOx

Air pollution is a pressing issue that is associated with adverse effects on human health, ecosystems, and climate. Despite many years of effort to improve air quality, nitrogen dioxide (NO2) limit values are still regularly exceeded in Europe, particularly in cities and along streets. This study explores how concentrations of nitrogen oxides (NOx = NO + NO2) in European urban areas have changed over the last decades and how this relates to changes in emissions. To do so, the incremental approach was used, comparing urban increments (i.e. urban background minus rural concentrations) to total emissions, and roadside increments (i.e. urban roadside concentrations minus urban background concentrations) to traffic emissions. In total, nine European cities were assessed. The study revealed that potentially confounding factors like the impact of urban pollution at rural monitoring sites through atmospheric transport are generally negligible for NOx. The approach proves therefore particularly useful for this pollutant. The estimated urban increments all showed downward trends, and for the majority of the cities the trends aligned well with the total emissions. However, it was found that factors like a very densely populated surrounding or local emission sources in the rural area such as shipping traffic on inland waterways restrict the application of the approach for some cities. The roadside increments showed an overall very diverse picture in their absolute values and trends and also in their relation to traffic emissions. This variability and the discrepancies between roadside increments and emissions could be attributed to a combination of local influencing factors at the street level and different aspects introducing inaccuracies to the trends of the emis-sion inventories used, including deficient emission factors. Applying the incremental approach was evaluated as useful for long-term pan-European studies, but at the same time it was found to be restricted to certain regions and cities due to data availability issues. The results also highlight that using emission inventories for the prediction of future health impacts and compliance with limit values needs to consider the distinct variability in the concentrations not only across but also within cities

The new urban intermediaries? The new middle classes and the remaking of London

In this article the position of the new middle classes that are currently leading the gentrification of much of inner London is considered. The author considers the arguments over whether the social structure of inner London is becoming increasingly polarised. He suggests that the middle income groups may in fact be taking on the role of social intermediaries between those high income groups, who are not reliant on state services, particularly education, and those who are most disadvantaged in inner London’s labour and housing markets and totally reliant on state services. The emerging education market  is a crucial arena for the middle classes who need to pass on their cultural capital to their children. It is also an opportunity to provide institutions of upward social mobility for the socially disadvantaged. At present it is unclear whether the new middle class presence in London is a force for social inclusion or is likely to add to social exclusion. The author’s conclusion is that the middle classes are more vulnerable to the costs of social exclusion than the upper classes and therefore have an incentive to become the intermediaries in London’s social structure. Short term pressures however to achieve advantage for their children are currently working against this, at least as far as the education system is concerned. The relationship between the middle classes and the marginalised social groups is still under negotiation. Sections of the middle class do however have the « potential » to act as intermediaries and therefore as agents for social inclusion.Cet article interroge la position des nouvelles classes moyennes, agents du processus de « gentrification » dans une grande partie des quartiers centraux de Londres. L’auteur examine les analyses selon lesquelles, au centre de Londres, la structure sociale connaîtrait une polarisation  croissante. Selon lui les groupes à revenus moyens pourraient occuper une position d’intermédiaires sociaux entre les groupes à fort capital économique, non dépendants des services publics (en particulier l’enseignement) et les plus désavantagés sur les marchés du travail et du logement du centre ville, qui eux dépendent entièrement de ces services. Le nouveau marché de l’éducation constitue un champ dont la maîtrise est essentielle pour les classes moyennes qui doivent assurer la transmission de leur capital culturel à leurs enfants. Ce marché pourrait également proposer un cadre institutionnel favorable à la mobilité sociale des catégories défavorisées. L’implantation de la nouvelle classe moyenne à Londres constitue-t-elle un facteur d’intégration sociale ou est-elle susceptible d’accentuer les phénomènes d’exclusion ? Il est difficile aujourd’hui de conclure sur ce point. Pour l’auteur, les classes moyennes sont plus sensibles aux coûts de l’exclusion sociale que les classes plus élevées, ce qui peut les inciter à jouer un rôle d’intermédiaire dans la structure sociale londonienne. S’y opposent cependant les contraintes immédiates  qui les poussent à assurer à leurs enfants une position privilégiée, du moins dans le champ éducatif. Les relations entre les classes moyennes et les groupes sociaux marginalisés sont encore en voie de négociation. Toutefois certaines fractions de la classe moyenne ont les moyens d’occuper cette position, de se comporter en agents du processus d’intégration sociale

Basic studies of baroclinic flows

Computations were completed of transition curves in the conventional annulus, including hysteresis effect. The model GEOSIM was used to compute the transition between axisymmetric flow and baroclinic wave flow in the conventional annulus experiments. Thorough testing and documentation of the GEOSIM code were also completed. The Spacelab 3 results from the Geophysical Fluid Flow Cell (GFFC) were reviewed and numerical modeling was performed of many of the cases with horizontal temperature gradients as well as heating from below, with different rates of rotation. A numerical study of the lower transition to axisymmetric flow in the baroclinic annulus was performed using GEOSIM

Universality and template synthesis of cosmic ray air shower radio emission

Accurate prediction of the radio emission from cosmic ray air showers relies on computationally demanding Monte Carlo simulations such as CoREAS. We aim to expedite this process via a semi-analytical synthesis model while maintaining high accuracy by using simulated radio pulses as templates. We present our key concept for template processing focusing on the development of the particle cascade and its empirical effect on the locally produced radio signal. In this context the universality of the radio emission from small sections of an air shower also becomes important where most previous studies focus on integral quantities observable at far distances.Comment: Proceedings of the 36th ICRC, Madison, USA, PoS(ICRC2019)29

Power Relations and Social Mix in Metropolitan Neighbourhoods in North America and Europe: Moving Beyond Gentrification?

Research on spatial segregation has suggested that social mix may be a temporary phase in class displacement, where relations between different groups are at best divided or ‘tectonic’, for instance in England. Political and policy discourses, by contrast, tend to uncritically valorize social mix as a means to breaking up concentrations of poverty and providing neighbourhoods with a middle-class voice. In the literature, little attention has been paid to power dynamics in socially mixed neighbourhoods and the implications this may have for understanding theory and policy. The five articles that make up this symposium address the ways in which social and ethnic groups interact in major cities in Europe and North America and, as the title suggests, this involves taking into account power relations, domination and negotiation between the different groups. There is a need to connect the experience of the deployment of power within neighbourhoods (and between them) with the discussions of power mechanisms at work in wider urban processes

The impact of atmospheric blocking on the compounding effect of ozone pollution and temperature: a copula-based approach

Ozone pollution and high temperatures have adverse health impacts that can be amplified by the combined effects of ozone and temperature. Moreover, changes in weather patterns are expected to alter ozone pollution episodes and temperature extremes. In particular, atmospheric blocking is a high-impact, large-scale phenomenon at mid-high latitudes that has been associated with temperature extremes. This study examines the impact of atmospheric blocking on the ozone and temperature dependence among measurement stations over Europe during the period 1999–2015. We use a copula-based method to model the dependence between the two variables under blocking and non-blocking conditions. This approach allows us to examine the impact of blocks on the joint probability distribution. Our results showed that blocks lead to increasing strength in the upper tail dependence of ozone and temperature extremes (> 95th percentile) in north-west and central Europe (e.g. the UK, Belgium, Netherlands, Luxembourg, Germany and the north-west of France). The analysis of the probability hazard scenarios revealed that blocks generally enhance the probability of compound ozone and temperature events by 20 % in a large number of stations over central Europe. The probability of ozone or temperature exceedances increases 30 % (on average) under the presence of atmospheric blocking. Furthermore, we found that, in a number of stations over north-western Europe, atmospheric blocking increases the probability of ozone exceedances by 30 % given high temperatures. Our results point out the strong influence of atmospheric blocking on the compounding effect of ozone and temperature events, suggesting that blocks might be considered a relevant predicting factor when assessing the risks of ozone-heat-related health effects