Ecological Impacts of Replacing Traditional Roofs with Green Roofs in Two Urban Areas

Urban land cover is dominated by impervious surface that degrades both terrestrial and aquatic ecosystems relative to predevelopment conditions. There are significant opportunities for designers of urban landscapes to use alternative land covers that have multiple functions, benefiting both human and nonhuman components of the urban ecosystem. Vegetated (green) roofs are one form of alternative land cover that has shown the potential to provide a variety of ecological benefits in urban areas. We evaluated how stormwater retention, building energy and temperature, and rooftop habitat are influenced by the use of green roofs using test plots in Georgia and Massachusetts. Green roofs were shown to recreate part of the predevelopment hydrology through increasing interception, stormwater storage, evaporation and transpiration on the rooftop and worked extremely well for small storm events. Temperature reductions were found on the green rooftop as compared to an asphalt surface, although other roof technologies that minimize temperatures, such as lighter colored membranes, provide similar benefits. Novel habitat was created on the rooftop, although the extent of this habitat was limited in part by plant survivability and the need for additional water inputs for diverse plant communities to survive. Despite the challenges, the green roof benefits reported here suggest that green roofs can be used effectively as a multifunctional land cover in urban areas

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

Temperature dependence of tropospheric ozone under NOx reductions over Germany

Due to the strong temperature dependence of surface ozone concentrations (O3), future warmer conditions may worsen ozone pollution levels despite continued efforts on emission controls of ozone precursors. Using longterm measurements of hourly O3 concentrations co-located with NOx concentrations in stations distributed throughout Germany, we assess changes in the climate penalty in summertime, defined as the slope of ozonetemperature relationship during the period 1999?2018. We find a stronger temperature sensitivity in the urban stations over the southwestern regions, especially in the first period of the study (1999?2008). We show a decrease in the climate penalty in most of stations during the second period of the study (2009?2018), with some exceptions (e.g. Berlin) where the climate penalty did not show significant changes. A key motivation of this study is to provide further insights into the impacts of NOx reductions in the O3-temperature relationship. For that, we propose a statisti-cal approach based on Generalized Additive Models (GAMs) to describe ozone production rates, inferred from hourly observations, as a function of NOx and temperature, among other variables relevant during the O3 production. The GAMs confirm lower O3 production rates during the second period (2009?2018) at most of the stations and a decreasing sensitivity to temperature. We observe that a large number of stations are transitioning to NOx-limited chemistry, consistent with a decreasing temperature dependence of O3 at moderate-high temperatures as a result of sustained NOx reductions. Moreover, the GAMs results showed changes in the shape of the function representing the O3-temperature relationship when comparing the first and second period, which suggest changes in VOC influencing the temperature dependence of O3. From these results, we infer effective VOC reductions over time that have also contributed to the observed decrease of O3 production rates. Thus, our analysis indicates that emissions reductions have been effective in a number of stations, particularly in the southwestern regions. However, we notice that in a few stations (e.g. Berlin) additional emission reductions should be required to effectively mitigate the temperature dependence of O3

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

Attribution of surface ozone to NOx and volatile organic compound sources during two different high ozone events

Increased tropospheric ozone (O3) and high temperatures affect human health during heat waves. Here, we perform a source attribution that considers separately the formation of German surface ozone from emitted NOx and volatile organic compound (VOC) precursors during two peak ozone events that took place in 2015 and 2018 which were associated with elevated temperatures. Results showed that peak ozone concentrations can be primarily attributed to nearby emissions of anthropogenic NOx (from Germany and immediately neighboring countries) and biogenic VOC. Outside of these high ozone episodes, baseline ozone concentrations are attributed primarily to long-range transport, with ozone due to remote anthropogenic NOx emissions and methane oxidation adding to the tropospheric ozone background. We show that a significant contribution to modeled O3 coming from German NOx or VOC emissions occurs mostly in southern Germany, emphasizing that the production of ozone depends on the local interplay between NOx and VOC precursors. Shipping activities in the Baltic and North seas have a large impact on ozone predicted in coastal areas, yet a small amount of ozone from these sources can also be seen far inland, showing the importance of transported ozone on pollution levels. We have also shown that changes in circulation patterns during the peak O3 episodes observed in Germany during the 2015 and 2018 heat waves can affect the contribution of different NOx emission sources to total O3; thus, the possible influence of multiple upwind source regions should be accounted for when mitigation strategies are designed. Our study also highlights the good correlation between ozone coming from German biogenic VOC emissions and total ozone, although the diurnal variation in the ozone coming from biogenic sources is not dominated by the diurnal variation in biogenic emissions, and the peaks of ozone from biogenic sources are disconnected from local emission peaks. This suggests that the formation of O3 from local German biogenic VOC emissions is not the sole factor that influences the ozone formation, and other meteorological and chemical processes affect the diel variation of ozone with a biogenic origin. Overall, this study helps to demonstrate the importance of a source attribution method to understand the sources of O3 in Germany and can be a useful tool that will help to design effective mitigation strategies

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