La prévision des précipitations par recherche d'analogues : état de l'art et perspectives

La prévision des précipitations par analogie, adaptée des sorties de modèles numériques de prévision, s'est améliorée ces dix dernières années et est actuellement implémentée opérationnellement dans diverses infrastructures françaises. Le premier objectif de cette étude est de dresser l'état de l'art de cette approche. L'application de cette méthode nécessite une base de données contenant les champs des variables qui permettent de caractériser les situations météorologiques passées. Etant donné qu'il existe deux archives de génération différente (réanalyses ERA-40 et NCEP/NCAR), la sensibilité de cette méthode de prévision au choix de l'archive a été étudiée. Les résultats révèlent une faible sensibilité, même si de manière générale les performances sont légèrement supérieures avec l'archive ERA-40, notamment pour les événements pluvieux extrêmes. Enfin, des perspectives d'amélioration de la méthode susceptibles d'être exploitées à court terme sont évoquées. / Precipitation forecasting based on an adaptation of model outputs through an analog sorting technique has been improved for around ten years. The method runs operationally in several French institutions. First, this short paper presents the state of the art of this approach and the more recent developments. Second, a sensitivity analysis to the choice of the database from which the variables that characterise the past meteorological situations are extracted is performed. Two available archives are tested (ERA-40 and NCEP/NCAR re-analyses). The results show that despite the performances obtained with the ERA-40 database are slightly better, especially for heavy rainfall events, the sensitivity is weak. Finally, further ways for improvement that could be investigated are suggested

Precipitation forecasting through an analog sorting technique: a comparative study

This study aims at comparing two quantitative precipitation forecasting techniques based on the meteorological analogy concept. Method A considers first a selection of analogous situations at synoptic scale. Second a subset of the most similar situations in terms of hygrometry is extracted. Method B extends method A by two innovative ways, which are restricting the search for analogues with temperature information instead of the common season criterion, and exploiting the information about vertical motion considering vertical velocity. Forecasts are evaluated in a perfect prognosis context and in operational conditions as well, by mean of verification measures (Continuous Ranked Probability Skill Score and scores computed from contingency tables). Results of the case study in France show that: (1) there is an increase in forecast skill when temperature and vertical velocity are included in the procedure, (2) it is possible to anticipate rainfall events up to one week ahead and (3) the introduction of new variables such as vertical velocity may be useless beyond few days ahead if the forecast of the weather model is not reliable

Quantifying the physical alterations of river reaches using a regional river morphology reference model. A step towards river restoration.

River engineeringRiver habitat management and restoratio

What impacts of climate change on surface water in France by 2070? Results of the Explore2070 project in metropolitan France and overseas departments

International audienceLes questions relatives à la disponibilité et à la gestion de l'eau concentreront l'essentiel des mesures d'adaptation qui seront prises dans les décennies à venir pour faire face aux conséquences des changements climatiques. Ces mesures devront également prendre en compte les évolutions socio-économiques, en termes de démographie, d'aménagement du territoire et de politiques publiques (agriculture, énergie, transports, etc.). Il est dès lors primordial pour les décideurs et gestionnaires de quantifier les évolutions socio-économiques possibles, ainsi que le devenir de la ressource en eau et de sa variabilité temporelle et spatiale. C'est dans ce contexte que le projet Explore2070 avait pour objectif d'évaluer les impacts possibles des changements climatiques et socio-économiques futurs sur les grandes masses d'eau (surface, souterrain, littoral) et la biodiversité, en France métropolitaine et sur les départements d'Outre-mer (Guadeloupe, Guyane, Martinique et Réunion). Piloté par le Ministère de l'Ecologie (MEDDTL), ce projet a rassemblé de nombreux bureaux d'études et instituts de recherche pour dresser un panorama général des évolutions à attendre à l'horizon 2070. Par son ampleur et la variété de ses objectifs, ce projet doit permettre de répondre à de nombreuses questions des gestionnaires et de mieux apprécier les enjeux de ces évolutions. Dans la suite, nous présentons les travaux réalisés spécifiquement sur la quantification des évolutions des eaux de surface. Nous détaillerons dans ce qui suit la démarche générale de modélisation proposée, la nature des résultats obtenus, ainsi que la façon dont les incertitudes ont été quantifiées. Ce dernier point est indispensable pour aider à la prise de décision dans un avenir incertain. / Water availability and water management will be the focus of most of the adaptation measures that will be taken in the next decades to face the consequences of climate change. These measures will have to account for the socio-economic evolutions, in terms of population size, town and country planning, as well as public policies (agriculture, energy, transports, etc.). It is therefore essential for decision makers and managers to be able to quantify the possible socio-economic evolutions together with the evolution of water resources and their temporal and spatial variability. In this context, the Explore2070 project aimed at evaluating the possible impacts of future climate and socio-economic changes on water bodies (surface water, groundwater and coastal water) and biodiversity, in metropolitan France and overseas departments (Guadeloupe, Martinique, French Guyana, and Réunion Island). The project was managed by the French Ministry of Ecology (MEDDTL) and gathered several consultancies and research institutes to establish a general overview of the expected evolutions by 2070. Through both the extent and the variety of the project’s objectives, Explore2070 will provide answers to many questions raised by managers and better evaluate the stakes related to these evolutions. In the following, we present the work done specifically to quantify the evolution of surface water. The general modelling approach, the type of results and the way uncertainties were quantified are detailed. Uncertainty quantification is essential to help decision making in an uncertain future

Climate shapes community flowering periods across biomes

Published online 11 May 2022Aim: Climate shapes the composition and function of plant communities globally, but it remains unclear how this influence extends to floral traits. Flowering phenology, or the time period in which a species flowers, has well-studied relationships with climatic signals at the species level but has rarely been explored at a cross-community and continental scale. Here, we characterise the distribution of flowering periods (months of flowering) across continental plant communities encompassing six biomes, and determine the influence of climate on community flowering period lengths.Location: Australia.Ta xo n: Flowering plants.Methods: We combined plant composition and abundance data from 629 standardised floristic surveys (AusPlots) with data on flowering period from the AusTraits database and additional primary literature for 2983 species. We assessed abundance- weighted community mean flowering periods across biomes and tested their relationship with climatic annual means and the predictability of climate conditions using regression models. Results: Combined, temperature and precipitation (annual mean and predictability) explain 29% of variation in continental community flowering period. Plant communities with higher mean temperatures and lower mean precipitation have longer mean flowering periods. Moreover, plant communities in climates with predictable temperatures and, to a lesser extent, predictable precipitation have shorter mean flowering periods. Flowering period varies by biome, being longest in deserts and shortest in al-pine and montane communities. For instance, desert communities experience low and unpredictable precipitation and high, unpredictable temperatures and have longer mean flowering periods, with desert species typically flowering at any time of year in response to rain.Main conclusions: Current climate conditions shape flowering periods across biomes, with implications for phenology under climate change. Shifts in flowering periods across climatic gradients reflect changes in plant strategies, affecting patterns of plant growth and reproduction as well as the availability of floral resources for pollinators across the landscape.Ruby E. Stephens, Hervé Sauquet, Greg R. Guerin, Mingkai Jiang, Daniel Falster, Rachael V. Gallaghe

Chromosome‐level reference genome of the soursop (Annona muricata) : a new resource for Magnoliid research and tropical pomology

The flowering plant family Annonaceae includes important commercially grown tropical crops, but development of promising species is hindered by a lack of genomic resources to build breeding programs. Annonaceae are part of the magnoliids, an ancient lineage of angiosperms for which evolutionary relationships with other major clades remain unclear. To provide resources to breeders and evolutionary researchers, we report a chromosome-level genome assembly of the soursop (Annona muricata). We assembled the genome using 444.32 Gb of DNA sequences (676x sequencing depth) from PacBio and Illumina short-reads, in combination with 10x Genomics and Bionano data (v1). A total of 949 scaffolds were assembled to a final size of 656.77 Mb, with a scaffold N50 of 3.43 Mb (v1), and then further improved to seven pseudo-chromosomes using Hi-C sequencing data (v2; scaffold N50: 93.2 Mb, total size in chromosomes: 639.6 Mb). Heterozygosity was very low (0.06%), while repeat sequences accounted for 54.87% of the genome, and 23,375 protein-coding genes with an average of 4.79 exons per gene were annotated using de novo, RNA-seq and homology-based approaches. Reconstruction of the historical population size showed a slow continuous contraction, probably related to Cenozoic climate changes. The soursop is the first genome assembled in Annonaceae, supporting further studies of floral evolution in magnoliids, providing an essential resource for delineating relationships of ancient angiosperm lineages. Both genome-assisted improvement and conservation efforts will be strengthened by the availability of the soursop genome. As a community resource, this assembly will further strengthen the role of Annonaceae as model species for research on the ecology, evolution and domestication potential of tropical species in pomology and agroforestry

Usefulness of the Reversible Jump Markov Chain Monte Carlo Model in Regional Flood Frequency Analysis

Regional flood frequency analysis is a convenient way to reduce estimation uncertainty when few data are available at the gauging site. In this work, a model that allows a non-null probability to a regional fixed shape parameter is presented. This methodology is integrated within a Bayesian framework and uses reversible jump techniques. The performance on stochastic data of this new estimator is compared to two other models: a conventional Bayesian analysis and the index flood approach. Results show that the proposed estimator is absolutely suited to regional estimation when only a few data are available at the target site. Moreover, unlike the index flood estimator, target site index flood error estimation seems to have less impact on Bayesian estimators. Some suggestions about configurations of the pooling groups are also presented to increase the performance of each estimator

SCOPE Climate: a 142-year daily high-resolution ensemble meteorological reconstruction dataset over France

SCOPE Climate (Spatially COherent Probabilistic Extended Climate dataset) is a 25-member ensemble of 142-year daily high-resolution reconstructions of precipitation, temperature, and Penman–Monteith reference evapotranspiration over France, from 1 January 1871 to 29 December 2012. SCOPE Climate provides an ensemble of 25 spatially coherent gridded multivariate time series. It is derived from the statistical downscaling of the Twentieth Century Reanalysis (20CR) by the SCOPE method, which is based on the analogue approach. SCOPE Climate performs well in comparison to both dependent and independent data for precipitation and temperature. The ensemble aspect corresponds to the uncertainty related to the SCOPE method. SCOPE Climate is the first century-long gridded high-resolution homogeneous dataset available over France and thus has paved the way for improving knowledge on specific past meteorological events or for improving knowledge on climate variability, since the end of the 19th century. This dataset has also been designed as a forcing dataset for long-term hydrological applications and studies of the hydrological consequences of climate variability over France. SCOPE Climate is freely available for any non-commercial use and can be downloaded as NetCDF files from https://doi.org/10.5281/zenodo.1299760 for precipitation, https://doi.org/10.5281/zenodo.1299712 for temperature, and https://doi.org/10.5281/zenodo.1251843 for reference evapotranspiration.</p

Chromosome-level reference genome of the soursop (Annona muricata): A new resource for Magnoliid research and tropical pomology

The flowering plant family Annonaceae includes important commercially grown tropical crops, but development of promising species is hindered by a lack of genomic resources to build breeding programs. Annonaceae are part of the magnoliids, an ancient lineage of angiosperms for which evolutionary relationships with other major clades remain unclear. To provide resources to breeders and evolutionary researchers, we report a chromosome‐level genome assembly of the soursop (Annona muricata). We assembled the genome using 444.32 Gb of DNA sequences (676× sequencing depth) from PacBio and Illumina short‐reads, in combination with 10× Genomics and Bionano data (v1). A total of 949 scaffolds were assembled to a final size of 656.77 Mb, with a scaffold N50 of 3.43 Mb (v1), and then further improved to seven pseudo‐chromosomes using Hi‐C sequencing data (v2; scaffold N50: 93.2 Mb, total size in chromosomes: 639.6 Mb). Heterozygosity was very low (0.06%), while repeat sequences accounted for 54.87% of the genome, and 23,375 protein‐coding genes with an average of 4.79 exons per gene were annotated using de novo, RNA‐seq and homology‐based approaches. Reconstruction of the historical population size showed a slow continuous contraction, probably related to Cenozoic climate changes. The soursop is the first genome assembled in Annonaceae, supporting further studies of floral evolution in magnoliids, providing an essential resource for delineating relationships of ancient angiosperm lineages. Both genome‐assisted improvement and conservation efforts will be strengthened by the availability of the soursop genome. As a community resource, this assembly will further strengthen the role of Annonaceae as model species for research on the ecology, evolution and domestication potential of tropical species in pomology and agroforestry