Regional climate downscaling with prior statistical correction of the global climate forcing

International audienceA novel climate downscaling methodology that attempts to correct climate simulation biases is proposed. By combining an advanced statistical bias correction method with a dynamical downscaling it constitutes a hybrid technique that yields nearly unbiased, high-resolution, physically consistent, three-dimensional fields that can be used for climate impact studies. The method is based on a prior statistical distribution correction of large-scale global climate model (GCM) 3-dimensional output fields to be taken as boundary forcing of a dynamical regional climate model (RCM). GCM fields are corrected using meteorological reanalyses. We evaluate this methodology over a decadal experiment. The improvement in terms of spatial and temporal variability is discussed against observations for a past period. The biases of the downscaled fields are much lower using this hybrid technique, up to a factor 4 for the mean temperature bias compared to the dynamical downscaling alone without prior bias correction. Precipitation biases are subsequently improved hence offering optimistic perspectives for climate impact studies

Sets of Priors Reflecting Prior-Data Conflict and Agreement

In Bayesian statistics, the choice of prior distribution is often debatable, especially if prior knowledge is limited or data are scarce. In imprecise probability, sets of priors are used to accurately model and reflect prior knowledge. This has the advantage that prior-data conflict sensitivity can be modelled: Ranges of posterior inferences should be larger when prior and data are in conflict. We propose a new method for generating prior sets which, in addition to prior-data conflict sensitivity, allows to reflect strong prior-data agreement by decreased posterior imprecision.Comment: 12 pages, 6 figures, In: Paulo Joao Carvalho et al. (eds.), IPMU 2016: Proceedings of the 16th International Conference on Information Processing and Management of Uncertainty in Knowledge-Based Systems, Eindhoven, The Netherland

Longitudinal evaluation of the impact of standardised packaging and Minimum Excise Tax on tobacco sales and industry revenue in the UK

BACKGROUND: Standardised packaging for factory-made cigarettes (FM) and roll-your-own tobacco (RYO), and a minimum excise tax (MET) were fully implemented in the UK in May 2017 following a 12-month transition period. This paper is the first to examine effects on tobacco sales volumes and company revenues. METHODS: Analysis of UK commercial supermarket and convenience store electronic point of sale data on tobacco sales. FM and RYO products' data (May 2015–April 2018) yielded 107 572 monthly observations. Expected values from additive mixed modelling were used to calculate trends in: (1) volumes of tobacco sold overall, by cigarette type (FM and RYO) and by seven market segments; and (2) company net revenues. A 10-month period (June 2015–March 2016) before the transition to standardised packs was compared with a 10-month period after the introduction of the MET and full implementation of standardised packs (June 2017–March 2018). RESULTS: Postimplementation, the average monthly decline in stick sales was 6.4 million (95% CI 0.1 million to 12.7 million) sticks faster than prelegislation, almost doubling the speed of decline. Sales of cheap FM brands, previously increasing, plateaued after implementation. Company monthly net revenues declined from a stable £231 million (95% CI £228 million to £234 million), prelegislation, to £198 million (95% CI £191 million to £206 million) in April 2018. CONCLUSIONS: The concurrent introduction of standardised packaging and MET in the UK was associated with significant decline in sales and in tobacco industry revenues, and the end of the previous growth in cheap cigarette brands that appeal to young and price conscious smokers

An Improved Scheme for Interpolating between an Atmospheric Model and Underlying Surface Grids near Orography and Ocean Boundaries

ABSTRACT To take into account the strong nonlinearities of vertical fluxes due to small-scale heterogeneities of surface properties, more and more coupled general circulation models compute part of their atmospheric physical parameterizations, either the surface fluxes or the whole package, on the finer grid of their ocean or land model. A modification of a traditional interpolation scheme is presented to calculate the values of atmospheric variables over surface model grid points. In addition to the desirable properties of flux conservation and preservation of a constant field, the new scheme allows discontinuities in the interpolated fields at the surface model's boundaries and orographic jumps, while remaining continuous elsewhere. It can also be tuned separately for each variable. The modified scheme is then evaluated using the circulation model of the Laboratoire de Météorologie Dynamique coupled to the Laboratoire d'Océanographie Dynamique et de Climatologie tropical Pacific Ocean model using the delocalized physics method. The results show a large improvement of heat and humidity fluxes near the focus region of the South American coast in the southeastern equatorial Pacific, and a subsequent westward propagation of significant cold SST anomalies

Pollution atmosphérique et climat

National audienceClimate change and air quality are closely related: through the policy measures implemented to mitigate these major environmental threats but also through the geophysical processes that drive them. We designed, developed and implemented a comprehensive regional air quality and climate modelling system to investigate future air quality in Europe taking into account the combined pressure of future climate change and long range transport. Using the prospective scenarios of the last generation of pathways for both climate change (emissions of well mixed greenhouse gases) and air pollutants, we can provide a quantitative view into the possible future air quality in Europe. We find that ozone pollution will decrease substantially under the most stringent scenario but the efforts of the air quality legislation will be adversely compensated by the penalty of global warming and long range transport for the business as usual scenario. For particulate matter, the projected reduction of emissions efficiently reduces exposure levels.Changement climatique et qualité de l'air sont intimement liés : à travers les politiques de gestion mises en oeuvre pour atténuer ces menaces environnementales majeures mais aussi à travers les processus géophysiques qui les gouvernent. Afin de pouvoir étudier l'évolution de la pollution atmosphérique en Europe en prenant en compte l'influence conjointe du changement climatique et du transport à longue distance, nous avons conçu, développé et mis en oeuvre un système complet de modélisation régionale du climat et de la qualité de l'air. En utilisant des scénarios prospectifs de dernière génération relatifs au changement climatique (émissions de gaz à effet de serre) mais aussi pour les polluants à courte durée de vie, nous avons pu proposer une quantification de l'évolution future de la qualité de l'air en Europe. D'après le scénario le plus volontariste, la pollution liée à l'ozone sera réduite de manière substantielle mais les efforts positifs induits par les politiques de gestion de la qualité de l'air seront contrebalancés par le changement climatique et le transport à longue distance pour le scénario statu-quo. En ce qui concerne les particules, les réductions d'émissions futures réduiront de manière efficace les niveaux d'exposition

Medical students’ challenges and suggestions regarding research training: a synthesis of comments from a cross-sectional survey

Background: We previously reported on a cross-sectional study of students from the Michael G. DeGroote School of Medicine at McMaster University that found most respondents wanted more opportunities to participate in research. Students provided additional comments that we synthesized to enrich the findings of our quantitative analysis.   Methods: From our previously administered 13-item, online questionnaire, run across three campuses in Ontario, Canada, 498 of 618 medical students completed our survey and 360 (72%) provided optional written comments, which we synthesized using thematic analysis in this current study.  Results: Major themes that emerged were: (1) Active student participation to identify research opportunities and interested mentors are needed; (2) Types of research involvement; (3) Uncertainty whether research training translates into useable skills; (4) Desire for a formalized research curriculum and centralization of research opportunities across campuses.  Conclusion: Programs should stress to interested students the importance of actively looking for research opportunities and consider both large and small-group educational sessions

Continuously-Tempered PDMP samplers

New sampling algorithms based on simulating continuous-time stochastic processes called piecewise deterministic Markov processes (PDMPs) have shown considerable promise. However, these methods can struggle to sample from multi-modal or heavy-tailed distributions. We show how tempering ideas can improve the mixing of PDMPs in such cases. We introduce an extended distribution defined over the state of the posterior distribution and an inverse temperature, which interpolates between a tractable distribution when the inverse temperature is 0 and the posterior when the inverse temperature is 1. The marginal distribution of the inverse temperature is a mixture of a continuous distribution on [0,1) and a point mass at 1: which means that we obtain samples when the inverse temperature is 1, and these are draws from the posterior, but sampling algorithms will also explore distributions at lower temperatures which will improve mixing. We show how PDMPs, and particularly the Zig-Zag sampler, can be implemented to sample from such an extended distribution. The resulting algorithm is easy to implement and we show empirically that it can outperform existing PDMP-based samplers on challenging multimodal posteriors

Pratiques Paysannes De Production Durable Des Graines De Voandzou [Vigna Subterranea (L.) Verdc.] Pour La Sécurité Alimentaire Dans Le Cameroun Septentrional

Bambara groundnut is a leguminous plant with high nutritive value of Sub Saharan Africa. In spite of its high potential in alimentation, the Bambara groundnut is less popularized. This crop grows on acid, dry and less fertile soils and may therefore be a resilient crop in the context of climatic variability. The present work aims to identify of all the morphotypes of this culture and the usual tools of conservation of its seeds during the storage process. Investigations carried out during 3 agricultural campaigns showed that women more than 40 years old represents more than 98% of producers of Bambara groundnuts in northern Cameroon. The production concerns 54 morphotypes use as food or as medicinal plants. During storage of grains of this legumes, the major pest is the bruchid Callosobruchus maculatus Fab. (Coleoptera : Chrysomelidae). Under traditional production way, the limitation of the postharvest losses due to this pest is done either by the use of 21 local plants as botanical insecticide or by the use of 25 industrial chemical pesticides