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Observation of different multifractal phase transitions over three typhoon events
No full textInternational audienceRainfall is extremely variable in both space and time, which makes its analysis complex. A widely used framework to properly handle these features is Universal Multifractals (UM), which is a physically based and mathematically robust framework. It relies on three parameters, meaning it is parsimonious. Two types of multifractal phase transitions can affect the analysis of a series: (i) the divergence of moments, which is related to the singular limit of the underlying cascade process at small scales and notably explains the power law fall-off observed on numerous geophysical fields, (ii) sampling limitations, which is related to the fact that great moments cannot be observed on finite series. This study employs UM to analyse the time series of rainfall intensities observed by the Parsival2 disdrometer at the 10-second resolution from three distinct typhoons over the period of July to October 2022, revealing differences and limitations in their statistical characteristics. It enables us to illustrate the  two previously mentioned concepts of divergence of moments and sampling limitations and their impact on the analysis of rainfall data. The analysis of typhoon Hinnamnor exhibited limitations due to the sampling dimension, indicating that the current data length was insufficient to capture the multifractal nature of the rainfall events for large moments, reducing the robustness of the analysis for moments greater than 5.43. It reflects sampling limitations, leading to a constrained understanding of extreme events. For typhoon Nalgae, our analysis highlighted the occurrence of divergence of moments, i.e. a limitation associated with a critical moment. As higher-order moments were calculated, we observed statistical values tending towards infinity, suggesting that extreme rainfall events significantly influenced this typhoon and pointing out the inadequacy of traditional statistical methods in such scenarios. Such multifractal phase transition is seldom observed on individual series, highlighting the interest of studying this typhoon series.  Finally, the analysis of the typhoon Nesat presented a behavior affected by both multifractal phase transitions resulting in a more complex interpretation.  Our findings provide new insights into the multifractal analysis of typhoon rainfall intensities, emphasising the importance of considering multifractal theory and its associated phase transitions when dealing with natural phenomenon data. These discoveries lay a crucial methodological foundation for more accurate prediction and response to extreme weather events. In case of rainfall, it then has some hydrological consequences notably in terms of stormwater management or optimization of dams for hydraulic production
Different Approaches to the Impacts of Climate Change, with a Common Goal: a Healthy Planet
No full textInternational audienceThis work has benefited from a multidisciplinary scientific and technical contributions geared by the HM&Co Lab of the Ecole des Ponts ParisTech (hmco.enpc.fr) towards the sustainable, desirable, and resilient city. The deepening of the Universal Multifractal (UM) concepts and the encouragement of their operational applications have been linked to several initiatives launched in recent years to better integrate the heterogeneity/intermittency into public policy practices. Considering the complex, dynamic interactions between geophysical and anthropogenic fields within a conurbation such as the Ile de France region, a transition towards the shared value economy has been considered to best stimulate sober and collaborative development, and there exist at least 3 ways to approach today’s discussions about future transformations. Their intercomparison is the core of this presentation. Following the United Nations 2030 Agenda, the first most conventional approach is based on notions of sustainable development, supported by appropriate adaptation and mitigation of climate change. Combining the notions of extreme variability and complexity would require linking together geophysical and urban scales within extreme variability, and therefore considering geosciences, and not just geophysics! Such a synergistic and integrative approach would help move beyond traditional silo thinking, addressing the complexity of data- and/or theory-driven urban geosciences. Finaly, combining the notions of scaling and nonlinear variability would ultimately require linking cascades, multiplicative chaos, and multifractals. This would initiate a break with linear stochastic models towards stronger heterogeneity / intermittency, which would in turn lead to a plausible clustering of field and activity fluctuations. The appearance of multifractal phase transitions then becomes possible, considerably amplifying the impact of any action, and would make future transformations fully efficient, effectively imitating the way in which Nature acts. This will be finally illustrated using several examples of so-called Nature Based Solutions (NBS)
Reconsidering the Existence of a Trend in the Asian Tropopause Aerosol Layer (ATAL) From 1979 to 2017
No full textInternational audienceAn enhanced aerosol layer, known as the Asian Tropopause Aerosol Layer (ATAL), has been observed within the seasonal Asian monsoon anticyclone (AMA) since the late 1990s. Given the apparently abrupt appearance of this layer based on observations, it has been speculated that it originates from increasing human made emissions in Asia. However, the ATAL confinement is a result of a dynamical feature and does not purely consist of human made components. We herein investigate the possible existence of an ATAL earlier than the late 1990s. We exploit earliest possible, high quality space-based aerosol observations from Stratospheric Aerosol and Gas Experiment, or SAGE (1979-1981), SAGE III/ISS (2017, ongoing) and revisit SAGE II (1984-2005) data analysis. We find that seasonal averaged solar occultation aerosol measurements (past and present) can neither be used to exclude the existence of the ATAL, nor to infer a significant trend. However, first CAM5-MAM7 simulations indicate the presence of an ATAL signal for the tested years 1979 and 1980, with a human made component. We hypothesize that the human made component of the ATAL likely occurred since at least the 1970s, while the natural ATAL component (e.g., from dust) has always existed. Extended simulation based ATAL evolution studies are therefore the most reliable source for early ATAL investigations
Employment Effects of a Weakening in European Anti-Tax Avoidance Rules: evidence from France
No full textThis paper provides causal evidence on how multinational enterprises’ (MNEs) presence in tax havens translates into job cuts in France following the 2006 European Court of Justice (ECJ) judgement on the Cadbury-Schweppes case, which weakened member States’controlled foreign company rules (CFC). Using French firm-level data over 2001 and 2014 we show that this weakening in European Anti-tax avoidance rules generates a sharp decline in employment in France in European MNEs having a pre-judgement presence in a European tax haven. We show that treated MNEs lose about 6% of their local employment after the ECJ decision. The effects are mainly concentrated in highly qualified workers and white collars (5% decline for each category). An event-study design shows that no effects are found for MNEs without a pre-judgement presence in a European tax haven, suggestingthat it is the weakening in the CFC rules that fosters job cuts at home. Two plausible explanations for these findings are linked to: i) a decline in the cost of opacity allowing firms to restructure and carry out otherwise expensive mass layoffs in France and ii) more stringent rules specifically affecting ”wholly artificial arrangements” (i.e. pure letter boxes), which increase the need to comply with substance rules and justify a presence in a European tax haven
Le traitement judiciaire des violences sexuelles et conjugales en France
No full textNote IPP n°107Malgré la prise de conscience collective suscitée par la vague #MeToo en octobre 2017, les violences faites aux femmes demeurent fréquentes. Dans un contexte de libération de la parole et de mobilisation accrue des pouvoirs publics, les affaires de violences sexuelles et conjugales portées à la connaissance de la justice n’ont jamais été aussi nombreuses. La réponse apportée par le système judiciaire à l’encontre de ces violences fait cependant l’objet de nombreuses critiques. Cette note cherche à apporter de nouveaux éclairages sur le traitement judiciaire des violences faites aux femmes et son évolution au cours du temps
Assessing the future IRS-MTG NH3 and temperature observations
No full textInternational audienceAmmonia (NH3) is an atmospheric pollutant mainly emitted by the agricultural sector, which has an effect on public health since it is a precursor of fine particles (PM2.5). The diurnal variability of NH3 in the atmosphere and its transformation into particles are poorly constrained and strongly depend on meteorological parameters, in particular temperature. This strongly influences our ability to correctly simulate NH3 emissions and associated particulate pollution events in atmospheric models The IRS (InfraRed Sounder) instrument which will be launched on the MTG (Meteosat Third Generation) satellite into geostationary orbit in late 2024, will offer the ability to evaluate NH3 diurnal variabilities and its dependence on atmospheric temperature with frequent measurements (every 30-45 minutes over Europe and Africa) and fine spatial resolution (4 km x 4 km at the Equator and Greenwich meridian). This work shows the potential of the European geostationary IRS-MTG mission to capture the spatio-temporal variability of ammonia and temperature focusing on a case study over the Brittany region in France. Synthetic spectra are simulated from the 4A/OP radiative transfer model using atmospheric states derived from the CHIMERE chemistry-transport model. The IRS NH3 observations are compared to the current IASI observations in terms of vertical sensitivity and error budget. The uncertainty analysis over the Brittany region is calculated using NH3 Jacobians computed from the 4A/OP radiative code and the noise covariance matrix provided by each satellite
Centralité et fécondité des gares dans l'iimaginaire écologique des villes
No full textInternational audienceL'univers des gares constitue un topos littéraire récurrent et peut-être, pourrait-on penser, éculé. Cette «grande demeure où n'habite personne et qui porte seulement le nom de la ville» 1 fournit quantité de ressources narratologiques. Que les trains la visitent encore ou bien qu'ils l'aient depuis longtemps abandonnée, la gare condensent le mouvement et dit pourtant la fixité, elle est associée à des états d'âme singuliers, déchirement de la séparation ou euphorie des retrouvailles, elle raconte l'enfance et les vacances, elle dessine aussi des souvenirs en nuances sépia. Dans cet ouvrage où l'on analyse l'apport de la nature et du vivant à la production littéraire sur la ville, on peut (et même on doit) passer et dépasser deux figures de la gare dans les récits et les romans pour se concentrer sur une troisième piste que nous souhaitons creuser davantage. La première figure narrative incontournable de la gare en littérature est celle qui;associe aux voyages ferroviaires en général. Une gare est un bâtiment qu'on fréquente communément au début ou à la fin d'un voyage en train. Elle représente donc un opérateur de liminalité dans l'espace et dans le temps. Elle offre la riche matière de motifs récurrents. À l'âge d'or du train (c'est-à-dire lorsque, entre le dernier tiers du 19 e siècle et première moitié du 20 e siècle, la société urbaine et industrielle se constitue à partir de ce type de mobilité), les romans intègrent typiquement l'histoire est connue d'un jeune homme de province qui arrive à Paris et dont on relatera la trajectoire ascendante ou non. La descente du train puis la traversée de la gare marquent physiquement et symboliquement un passage entre des mondes, entre des modes d'être. Quelques gestes banals, quelques lieux conventionnels (le guichet, le buffet) forment la toile de fond d'une angoisse ou d'une délivrance
Removing barriers to plant-based diets: assisting doctors with vegan patients
No full textInternational audienceShifting to plant-based diets can alleviate many of the externalities associated with the current food system. Spontaneous shifts in diet are often hindered by consumers’ imperfect knowledge about the health risks and benefits, which leads them to seek advice from their doctors. However, doctors have often had only limited nutrition training, and often express negative opinions of plant-based diets, even though recent evidence suggests that they confer substantial health benefits. We here explore whether providing doctors (general practitioners) with information about the risks and benefits of plant-based diets significantly changes their attitudes and medical practices. We run a survey experiment on a representative sample of French doctors and assess the impact of an information campaign developed by doctors to inform their colleagues about plant-based nutrition through case studies. Our confirmatory analysis shows that our information campaign effectively changes doctors’ views about plant-based diets (Cohen's d: 0.71). To a smaller extent, we find a positive but not statistically nor economically significant effect of the intervention on the doctors’ (hypothetical) medical practice with patients who follow a plant-based diet (Cohen's d: 0.22)
L’évolution du cadre bâti en Turquie, entre risque sismique et rentabilité du secteur de la construction : négociations et controverses sociotechniques
No full textInternational audienceThis article aims to study the transformation of seismic risk in Istanbul’s urban areas, focusing specifically on developments in the building sector. Since the 1999 earthquakes in the Marmara region, many laws, codes and standards governing building materials have been established in Turkey as a response to the threat of earthquake-induced building collapse. Describing successive assemblages of actors involved in using building tools to negotiate seismic risk management, we examine how risk and the urban environment are evolving conjointly. The first part of the analysis examines the construction sector’s regulatory framework since 1999, which has shifted responsibility for seismic risk from the state to construction industry actors; that is, service providers, construction auditors, material producers and civil engineers. It then goes on to explain the choices made by players in the building industry who favor the demolition and reconstruction of buildings rather than their rehabilitation. This process, however, generates economic and financial risks correlated with that of building collapse, the interactions of which highlight controversies surrounding the circumvention of construction standards, sometimes leading to increased individual vulnerability. We conclude that earthquake hazards are gradually being diluted into a more complex assemblage of risks, involving the interdependence of multiple factors that play a role in the fragility of the built environment and the actors concerned.Cet article vise à étudier les reconfigurations du risque sismique dans l’espace urbain à Istanbul à partir des manières dont celui-ci est pris en charge par le secteur de la construction. Depuis les séismes de 1999 dans la région de Marmara, de nombreux dispositifs (lois, codes et normes) encadrant les matériaux de construction ont été développés en Turquie comme réponse au risque d’effondrement des bâtiments en cas de secousse sismique. En décrivant les assemblages successifs d’acteurs négociant la prise en charge du risque sismique par les outils de construction, nous examinons les évolutions conjointes entre les risques et l’urbain. Un premier temps de l’analyse est consacré à l’encadrement du secteur de la construction depuis 1999, conduisant à déplacer la responsabilité envers le risque sismique de l’État vers les acteurs de ce secteur : prestataires, audits sur la construction, producteurs de matériaux, ingénieurs en génie civil. Dans un second temps, l’article explique les choix qui conduisent les acteurs de la construction à favoriser la démolition et la reconstruction des bâtiments plutôt que leur réhabilitation. Ce processus engendre des risques économiques et financiers corrélés à la prise en charge du risque d’effondrement des bâtiments. Enfin les interactions entre les risques mettent en évidence des controverses sur le contournement des normes de la construction conduisant parfois à renforcer la vulnérabilité des individus. Nous concluons que l’aléa sismique se retrouve progressivement dilué dans une perception de risques plus complexe mettant en jeu une interdépendance de facteurs multiples renforçant la vulnérabilité du cadre bâti et sur les acteurs
COVID-19 scaling dynamics in growth and decline phases
No full textThe definition of optimal COVID-19 mitigation strategies remains worldwide on the top of public health agendas, particularly when facing a second wave. It requires a better understanding and a refined modelling of its dynamics. We emphasise the fact that epidemic models are phenomenologically based on the paradigm of a cascade of contacts that propagates infection. However, the introduction of ad-hoc characteristic times and corresponding rates spuriously break their scale symmetry.Here we theoretically argue and empirically demonstrate that COVID-19 dynamics, during both growth and decline phases, is a cascade with a rather universal scale symmetry whose power-law statistics drastically differ from those of an exponential process. This involves slower but longer phases which are furthermore linked by a fairly simple symmetry. These results explain biases of epidemic models and help to improve them. Due to their generality, these results pave the way to a renewed approach to epidemics, and more generally to growth phenomena