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Recent years have seen early instrumental observations play an increasingly important role in climate research, allowing past daily-to-decadal climate variability and weather extremes to be explored in greater detail. The 18th century saw the formation of several short-lived meteorological networks of which the one organised by the Societas Meteorologica Palatina is arguably the most well-known. This network stood out as one of those few that efficiently managed to control its members, integrating, refining and publishing measurements taken from numerous stations around Europe and beyond. Although much has been written about the network in both history, science, and individual prominent series used for climatological studies, the actual measurements have not yet been digitised and published in extenso. This paper represents an important step towards filling this perceived gap in research. Here we provide an inventory listing the availability of observed variables for the 37 stations that belonged to the Society's network and discuss their historical context. Most of these observations have been digitised and a considerable fraction has been converted and formatted. In this paper we focus on the temperature and pressure measurements, which have been corrected and homogenised. We then demonstrate their potential for climate research by analysing two cases of extreme weather. The recovered series will have wide applications and could contribute to a better understanding of the mechanisms behind climatic variations and extremes, as well as the societal reactions to adverse weather. Even the shorter series could be ingested into reanalyses and improve the quality of large scale reconstructions.

Les normales climatologiques sont des produits statistiques calculés à partir de séries de données sur des périodes de 30 ans. Elles comprennent aussi bien des valeurs moyennes que d'autres paramètres statistiques, les quantiles par exemple. Définies par l'Organisation météorologique mondiale, elles permettent de caractériser le climat sur ces périodes et servent de référence pour analyser les événements climatiques en temps réel. Météo-France a entrepris depuis janvier 2021 le calcul des nouvelles normales climatiques 1991-2020 et les utilise dans l'ensemble de sa production climatologique depuis le 28 juin 2022. Climatological normals are defined as statistical products computed over a 30-year period; they include both mean and other statistical parameters, e.g. quantiles. Defined by the World Meteorological Organization, they are used to define the conditions most likely to be experienced in a given location over a period of time. They also serve as a basis in order to monitor climate events in real time. Météo-France started to compute the new climatological normals 1991-2020 and started to use them in its climatological production from June 28th, 2022.

In recent years a number of reanalysis datasets have been published that cover the past century or more, including the ‘Twentieth Century Reanalysis’ 20CRv2 and the European Reanalysis of the twentieth century ERA-20C. These datasets are widely used, showing the need for, and possible benefit of, reanalysis data products designed for climate applications. The twentieth-century reanalyses so far have assimilated only surface observations, and rely on independent estimates of monthly averaged sea-surface temperatures and sea ice concentrations as boundary conditions. While 20CRv2 uses only observations of surface and sea-level pressure, ERA-20C additionally assimilates marine winds. Here we describe an experimental reanalysis, referred to as ERA-PreSAT, which covers the period 1939–1967 and also assimilates historical upper-air data. Assessments of this dataset including comparisons with independent data show that (i) temperature biases in the Northern Hemisphere are largely reduced compared to reanalyses that assimilate surface data only, (ii) concentration of 1940s upper-air data in the northern extratropics created a strong interhemispheric asymmetry which is likely not realistic, (iii) the forecast skill in the Northern Hemisphere has increased substantially compared to reanalyses that assimilate surface data only, (iv) day-to-day and (in the northern extratropics) month-to-month correlations with independent observations (of total column ozone, upper-air data) increase over time, (v) interannual variability is well captured in the reanalysis, (vi) a signature of the stratospheric Quasi-Biennial Oscillation is present as far back as the 1940s, and (vii) tropical cyclones are not well represented. The generally encouraging results from the experimental ERA-PreSAT reanalysis underline that early upper-air data greatly contribute to our knowledge on the troposphere and lower stratosphere over the twentieth century.

Extreme droughts are weather phenomena of considerable importance, involving significant environmental and societal impacts. While those that have occurred in the comparatively recent period of instrumental measurement are identified and dated on the basis of systematic, machine-standardized meteorological and hydrological observations, droughts that took place in the pre-instrumental period are usually described only through the medium of documentary evidence. The extreme drought of 1842 in Europe presents a case in which information from documentary data can be combined with systematic instrumental observations. Seasonal, gridded European precipitation totals are used herein to describe general DJF, MAM, and JJA precipitation patterns. Annual variations in monthly temperatures and precipitation at individual stations are expressed with respect to a 1961–1990 reference period, supplemented by calculation of selected drought indices (Standardized Precipitation Index, SPI; Standardized Precipitation Evapotranspiration Index, SPEI; and Palmer Z index). The mean circulation patterns during the driest months are elucidated by means of sea-level pressure (SLP) maps, the North Atlantic Oscillation Index (NAOI), and the Central European Zonal Index (CEZI). Generally drier patterns in 1842 prevailed in January–February and at various intensities between April and August. The driest patterns in 1842 occurred in a broad zonal belt extending from France to eastern central Europe. A range of documentary data is used to describe the peculiarities of agricultural, hydrological, and socio-economic droughts, with particular attention to environmental and societal impacts and human responses to them. Although overall grain yields were not very strongly influenced, a particularly bad hay harvest, no aftermath (hay from a second cut), and low potato yields led to severe problems, especially for those who raised cattle. Finally, the 1842 drought is discussed in terms of long-term drought variability, European tree-ring-based scPDSI (self-calibrated Palmer Drought Severity Index) reconstruction, and the broader context of societal impacts.

Historical reanalyses that span more than a century are needed for a wide range of studies, from understanding large‐scale climate trends to diagnosing the impacts of individual historical extreme weather events. The Twentieth Century Reanalysis (20CR) Project is an effort to fill this need. It is supported by the National Oceanic and Atmospheric Administration (NOAA), the Cooperative Institute for Research in Environmental Sciences (CIRES), and the U.S. Department of Energy (DOE), and is facilitated by collaboration with the international Atmospheric Circulation Reconstructions over the Earth initiative. 20CR is the first ensemble of sub‐daily global atmospheric conditions spanning over 100 years. This provides a best estimate of the weather at any given place and time as well as an estimate of its confidence and uncertainty. While extremely useful, version 2c of this dataset (20CRv2c) has several significant issues, including inaccurate estimates of confidence and a global sea level pressure bias in the mid‐19th century. These and other issues can reduce its effectiveness for studies at many spatial and temporal scales. Therefore, the 20CR system underwent a series of developments to generate a significant new version of the reanalysis. The version 3 system (NOAA‐CIRES‐DOE 20CRv3) uses upgraded data assimilation methods including an adaptive inflation algorithm; has a newer, higher‐resolution forecast model that specifies dry air mass; and assimilates a larger set of pressure observations. These changes have improved the ensemble‐based estimates of confidence, removed spin‐up effects in the precipitation fields, and diminished the sea‐level pressure bias. Other improvements include more accurate representations of storm intensity, smaller errors, and large‐scale reductions in model bias. The 20CRv3 system is comprehensively reviewed, focusing on the aspects that have ameliorated issues in 20CRv2c. Despite the many improvements, some challenges remain, including a systematic bias in tropical precipitation and time‐varying biases in southern high‐latitude pressure fields.

Global dynamical reanalyses of the atmosphere and ocean fundamentally rely on observations, not just for the assimilation (i.e., for the definition of the state of the Earth system components) but also in many other steps along the production chain. Observations are used to constrain the model boundary conditions, for the calibration or uncertainty determination of other observations, and for the evaluation of data products. This requires major efforts, including data rescue (for historical observations), data management (including metadatabases), compilation and quality control, and error estimation. The work on observations ideally occurs one cycle ahead of the generation cycle of reanalyses, allowing the reanalyses to make full use of it. In this paper we describe the activities within ERA-CLIM2, which range from surface, upper-air, and Southern Ocean data rescue to satellite data recalibration and from the generation of snow-cover products to the development of a global station data metadatabase. The project has not produced new data collections. Rather, the data generated has fed into global repositories and will serve future reanalysis projects. The continuation of this effort is first contingent upon the organization of data rescue and also upon a series of targeted research activities to address newly identified in situ and satellite records.

The European Reanalysis of Global Climate Observations 2 (ERA-CLIM2) is a European Union Seventh Framework Project started in January 2014 and due to be completed in December 2017. It aims to produce coupled reanalyses, which are physically consistent datasets describing the evolution of the global atmosphere, ocean, land surface, cryosphere, and the carbon cycle. ERA-CLIM2 has contributed to advancing the capacity for producing state-of-the-art climate reanalyses that extend back to the early twentieth century. ERA-CLIM2 has led to the generation of the first European ensemble of coupled ocean, sea ice, land, and atmosphere reanalyses of the twentieth century. The project has funded work to rescue and prepare observations and to advance the data-assimilation systems required to generate operational reanalyses, such as the ones planned by the European Union Copernicus Climate Change Service. This paper summarizes the main goals of the project, discusses some of its main areas of activities, and presents some of its key results.

The eruption of Mount Tambora (Indonesia) in April 1815 is the largest documented volcanic eruption in history. It is associated with a large global cooling during the following year, felt particularly in parts of Europe and North America, where the year 1816 became known as the "year without a summer". This paper describes an effort made to collect surface meteorological observations from the early instrumental period, with a focus on the years of and immediately following the eruption (1815–1817). Although the collection aimed in particular at pressure observations, correspondent temperature observations were also recovered. Some of the series had already been described in the literature, but a large part of the data, recently digitised from original weather diaries and contemporary magazines and newspapers, is presented here for the first time. The collection puts together more than 50 sub-daily series from land observatories in Europe and North America and from ships in the tropics. The pressure observations have been corrected for temperature and gravity and reduced to mean sea level. Moreover, an additional statistical correction was applied to take into account common error sources in mercury barometers. To assess the reliability of the corrected data set, the variance in the pressure observations is compared with modern climatologies, and single observations are used for synoptic analyses of three case studies in Europe. All raw observations will be made available to the scientific community in the International Surface Pressure Databank.

The International Surface Pressure Databank (ISPD) is the world's largest collection of global surface and sea-level pressure observations. It was developed by extracting observations from established international archives, through international cooperation with data recovery facilitated by the Atmospheric Circulation Reconstructions over the Earth (ACRE) initiative, and directly by contributing universities, organizations, and countries. The dataset period is currently 1768–2012 and consists of three data components: observations from land stations, marine observing systems, and tropical cyclone best track pressure reports. Version 2 of the ISPD (ISPDv2) was created to be observational input for the Twentieth Century Reanalysis Project (20CR) and contains the quality control and assimilation feedback metadata from the 20CR. Since then, it has been used for various general climate and weather studies, and an updated version 3 (ISPDv3) has been used in the ERA-20C reanalysis in connection with the European Reanalysis of Global Climate Observations project (ERA-CLIM). The focus of this paper is on the ISPDv2 and the inclusion of the 20CR feedback metadata. The Research Data Archive at the National Center for Atmospheric Research provides data collection and access for the ISPDv2, and will provide access to future versions.

Observations are the foundation for understanding the climate system. Yet, currently available land meteorological data are highly fractured into various global, regional, and national holdings for different variables and time scales, from a variety of sources, and in a mixture of formats. Added to this, many data are still inaccessible for analysis and usage. To meet modern scientific and societal demands as well as emerging needs such as the provision of climate services, it is essential that we improve the management and curation of available land-based meteorological holdings. We need a comprehensive global set of data holdings, of known provenance, that is truly integrated both across essential climate variables (ECVs) and across time scales to meet the broad range of stakeholder needs. These holdings must be easily discoverable, made available in accessible formats, and backed up by multitiered user support. The present paper provides a high-level overview, based upon broad community input, of the steps that are required to bring about this integration. The significant challenge is to find a sustained means to realize this vision. This requires a long-term international program. The database that results will transform our collective ability to provide societally relevant research, analysis, and predictions in many weather- and climate-related application areas across much of the globe.

Historical, i.e. pre-1957, upper-air data are a valuable source of information on the state of the atmosphere, in some parts of the world dating back to the early 20th century. However, to date, reanalyses have only partially made use of these data, and only of observations made after 1948. Even for the period between 1948 (the starting year of the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis) and the International Geophysical Year in 1957 (the starting year of the ERA-40 reanalysis), when the global upper-air coverage reached more or less its current status, many observations have not yet been digitised. The Comprehensive Historical Upper-Air Network (CHUAN) already compiled a large collection of pre-1957 upper-air data. In the framework of the European project ERA-CLIM (European Reanalysis of Global Climate Observations), significant amounts of additional upper-air data have been catalogued (> 1.3 million station days), imaged (> 200 000 images) and digitised (> 700 000 station days) in order to prepare a new input data set for upcoming reanalyses. The records cover large parts of the globe, focussing on, so far, less well covered regions such as the tropics, the polar regions and the oceans, and on very early upper-air data from Europe and the US. The total number of digitised/inventoried records is 61/101 for moving upper-air data, i.e. data from ships, etc., and 735/1783 for fixed upper-air stations. Here, we give a detailed description of the resulting data set including the metadata and the quality checking procedures applied. The data will be included in the next version of CHUAN. The data are available at doi:10.1594/PANGAEA.821222.

10.1002/gdj3.4 Availability of long-term and high-quality instrumental climate records is still insufficient and the rich heritage of meteorological surface observations is largely underexploited in many parts of the world. This is particularly striking over the Greater Mediterranean region (GMR), where meteorological observations have been taken since the 18th century at some locations. The lack of high quality and long series here is despite this region being regarded as a climate change hot spot. This article mainly assesses relevant sources containing Mediterranean historical climate data and metadata either from online repositories worldwide or physical archives, with the emphasis here on the rich holdings kept at French archives. A particular case study is the data rescue (DARE) program undertaken by the Algerian National Meteorological Service, as well as some of the past and ongoing projects and initiatives aimed at enhancing climate data availability and accessibility over the GMR. Our findings point to the high potential for undertaking DARE activities over the GMR and the need for bringing longer and higher quality climate time series to support a diverse number of scientific and technical assessments and policies.

An abundance of methods have been developed over the years to perform the frequency analysis (FA) of extreme environmental variables. Although numerous comparisons between these methods have been implemented, no general comparison framework has been agreed upon so far. The objective of this paper is to build the foundation of a data-based comparison framework, which aims at complementing more standard comparison schemes based on Monte Carlo simulations or statistical testing. This framework is based on the following general principles: (i) emphasis is put on the predictive ability of competing FA implementations, rather than their sole descriptive ability measured by some goodness-of-fit criterion; (ii) predictive ability is quantified by means of reliability indices, describing the consistency between validation data (not used for calibration) and FA predictions; (iii) stability is also quantified, i.e., the ability of a FA implementation to yield similar estimates when calibration data change; and (iv) the necessity to subject uncertainty estimates to the same scrutiny as point estimates is recognized, and a practical approach based on the use of the predictive distribution is proposed for this purpose. This framework is then applied to a case study involving 364 gauging stations in France, where 10 FA implementations are compared. These implementations correspond to the local, regional, and local-regional estimation of Gumbel and generalized extreme value distributions. Results show that reliability and stability indices are able to reveal marked differences between FA implementations. Moreover, the case study also confirms that using the predictive distribution to indirectly scrutinize uncertainty estimates is a viable approach, with distinct FA implementations showing marked differences in the reliability of their uncertainty estimates. The proposed comparison framework therefore constitutes a valuable tool to compare the predictive reliability of competing FA implementations, along with the reliability of their uncertainty estimates.

Dandin Philippe, Fleuter Gérard, Javelle Jean-Pierre, Jourdain Sylvie, Roucaute Emeline, Schneider Michel. Recherche et sauvetage d’informations météorologiques anciennes : un apport et un regard nécessaires sur le climat. In: La Gazette des archives, n°230, 2013-2. Les sources d’archives pour l’étude du climat et de l’environnement. pp. 45-65.

Les series pluviometriques infra-quotidiennes disponibles dans la base de donnees climatologiques de Meteo-France sont generalement de duree assez courte pour l’estimation locale des valeurs extremes (moins de 20 ans) tandis que d’importants fonds documentaires au format papier existent dans les archives des Centres Departementaux et des differents gestionnaires de reseau. Dans le cadre du projet EXTRAFLO, subventionne par l’Agence Nationale de la Recherche (ANR), Meteo-France a valide en contexte operationnel, un outil moderne de digitalisation des pluviogrammes, nomme Digitalise. Des actions de digitali-sation de plusieurs longues series ont ete engagees pour evaluer leur apport pour la connaissance des valeurs extremes. Apres avoir verifie les conditions d’utilisation de la methode, une procedure de validation des donnees a ete definie. La comparaison des donnees pluviographiques anciennes aux observations quotidiennes des pluviometres met en evidence quelques biais significatifs dans les differentes gammes d’intensite, bien correlees avec le type d’instrument utilise. Ces nouvelles series presentent toutefois un grand interet pour l’estimation des extremes pluviometriques notamment aux pas de temps infra quotidien, avec une reduction significative des intervalles de confiance liee a l’allongement des chroniques Sur la base de ces resultats, un programme de saisie de series pluviographiques anciennes est en cours de definition avec les services regionaux de Meteo-France et pourra etre etendu aux partenaires interesses pouvant beneficier de la mise a disposition gracieuse du logiciel Digitalise.

One major concern of climate change is the possible rise of temperature extreme events, in terms of occurrence and intensity. To study this phenomenon, reliable daily series are required, for instance to compute daily-based indices: high-order quantiles, annual extrema, number of days exceeding thresholds, and so on. Because observed series are likely to be affected by changes in the measurement conditions, adapted homogenization procedures are required. Although a very large number of procedures have been proposed for adjustment of observed series at a monthly time scale, few have been proposed for adjustment of daily temperature series. This article proposes a new adjustment method for temperature series at a daily time scale. This method, called spline daily homogenization (SPLIDHOM), relies on an indirect nonlinear regression method. Estimation of the regression functions is performed by cubic smoothing splines. This method is able to adjust the mean of the series as well as high-order quantiles and moments of the series. When using well-correlated series, SPLIDHOM improves the results of two widely used methods, as a result of an optimal selection of the smoothing parameter. Applications to the Toulouse, France, temperature series are shown as a real example.

This study analyzes extremes of geostrophic wind speeds derived from sub-daily surface pressure observations at 13 sites in the European region from the Iberian peninsula to Scandinavia for the period from 1878 or later to 2007. It extends previous studies on storminess conditions in the Northeast (NE) Atlantic-European region. It also briefly discusses the relationship between storminess and the North Atlantic Oscillation (NAO). The results show that storminess conditions in the region from the Northeast Atlantic to western Europe have undergone substantial decadal or longer time scale fluctuations, with considerable seasonal and regional differences (especially between winter and summer, and between the British Isles-North Sea area and other parts of the region). In the North Sea and the Alps areas, there has been a notable increase in the occurrence frequency of strong geostrophic winds from the mid to the late twentieth century. The results also show that, in the cold season (December–March), the NAO-storminess relationship is significantly positive in the north-central part of this region, but negative in the south-southeastern part.

The Climatology Department of Meteo-France aims at enriching the French climatological heritage in reliable and usable series. It lies within the general scope of climate change studies and allows the study of particular events. Climate change studies over the 20th century were subject to various publications. Data of the last decades of the 19th century are being researched and keyed, considering the fact that the weather station network has been organized gradually since 1856. Various European projects enable to capitalize the efforts put in each country concerning long-term data and offer products useful for the characterization of past events. High monthly rainfall amounts occur in April and May, frequency of South-West Oceanic regime is higher than expected. High rainfall events occur at the end of May.

[Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAU [Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAU; International audience; This paper presents a comparison of models for extreme rainfall and flood values. Based on a large set of thousands of rainfall and discharge data, the French ExtraFlo project showed that design estimate of extreme values based on the fitting of a distribution on a limited sample of maximum values is very inaccurate when only a few decades of observation are available. Some interesting alternatives are possible, using a regional approach, or historical data when available, or simulation methods, or sedimentological or geochemical signatures of flood deposits.; Cette communication présente les principaux résultats du projet ExtraFlo sur l'estimation des pluies et crues extrêmes. A partir d'un jeu de données conséquent de plusieurs milliers de stations, une procédure d'inter-comparaison a permis d'évaluer les performances d'une trentaine d'implémentations différentes issues de différentes combinaisons (modèle probabiliste, méthode d'estimation, cadre local / régional / mixte local et régional). Le projet ExtraFlo a permis de mettre en évidence le manque de robustesse des approches basées sur le traitement statistique d'une série de quelques dizaines d'années d'observation. Des alternatives intéressantes existent, basées sur l'exploitation des records de pluie et de débit à l'échelle d'une région, de la collecte de données historiques quand cela est possible, de méthodes de simulation basées sur le couplage d'un générateur d'averses avec un modèle hydrologique pour la transformation des pluies en débit, ou des traces morphologiques laissées par les crues anciennes.

Future reanalyses might profit from assimilating additional historical surface as well as upper-air data. In the framework of the European Reanalysis of Global Climate Observations (ERACLIM; www.era-clim.eu) project, significant amounts of pre-1957 upper-air and surface data have been cataloged (>2.5 million station days), imaged (>450,000 images), and digitized (>1.25 million station days) to prepare new input datasets for upcoming reanalyses. These data cover large parts of the globe, focusing henceforth on less well-covered regions such as the tropics, the polar regions, and the oceans and on very early twentieth-century upper-air data from Europe and the United States. The total numbers of digitized/inventoried records (i.e., time series of meteorological data at fixed stations or from moving observational platforms) are 80/214 (surface), 735/1,783 (upper air), and 61/101 [moving upper-air (i.e., data from ships, etc.)]. Here, the authors give an overview of the data rescue activities, the data, and the applied quality checking procedures and demonstrate their usefulness for analyzing past weather and climate. The data will be made available online (at www.era-clim.eu). The upper-air data will be included in the next version of the Comprehensive Historical Upper-Air Network (CHUAN) and are also available online (http://doi.pangaea.de/10.1594/PANGAEA.821222).

Introduction L’evolution reglementaire de la politique de gestion des risques des etablissements de sante (ES) incite a developper au cours des formations des outils valides par la HAS dont l’analyse de scenario clinique (ASC). L’ASC permet a partir d’un evenement indesirable grave (EIG) survenu dans un autre ES, de reflechir sur les causes, d’identifier les vulnerabilites, les points forts et les actions d’amelioration a mettre en oeuvre pour eviter ce dysfonctionnement. Notre objectif est de tester cette methode de gestion du risque a priori au risque transfusionnel. Materiel et methode La methode a ete experimentee dans notre etablissement par l’EOH. Nous avons integre l’ASC dans la journee de formation transfusionnelle validante pour le DPC. Le prealable etait la construction d’un scenario adapte, a partir d’un accident immunologique par incompatibilite ABO. L’animation des seances etait assuree par deux professionnels : le correspondant d’hemovigilance et un cadre de sante forme a la gestion des risques. Une enquete de satisfaction de la methode aupres des participants a ete realisee. Resultats Les criteres de reussite de l’ASC etaient reunis : 1 animateur expert en gestion du risque transfusionnel et 1 animateur expert forme a la methode, des professionnels de plusieurs unites de soins, un suivi rigoureux des etapes et du temps. Les axes d’amelioration portant essentiellement sur la realisation de la carte de groupe et l’etape reception ont ete reevalues 3 mois apres. Neuf questionnaires de satisfaction ont ete analyses ; les professionnels etaient satisfaits trouvant la methode facile. Ils se sont impliques dans le recherche des causes de l’accident ABO. Conclusion L’ASC est une methode simple, efficace qui en 1 heure, permet aux professionnels d’analyser leurs pratiques, d’identifier leurs defaillances et de proposer des solutions. Les EIG analyses (IG, EIR grade 2 a 4…) constituent une base de donnees interessante pour la creation de scenarii.

La reconstitution de la séquence hydrométéorologique ayant conduit à la crue de l'Isère des 1er et 2 novembre 1859 a été mené en quatre étapes. La première, conduite par Météo-France, a consisté à rechercher, collecter et critiquer les données encore disponibles, notamment, les stations mesurant la pression atmosphérique en France. Cela a permis de tracer pour tout le mois d'octobre 1859 les cartes de pression au niveau de la mer, et de les interpréter en termes de circulation et de types de temps. Pour chaque journée de 1859, ces cartes ont été utilisées par le Cemagref de Lyon pour rechercher, dans la période récente (1953-2005) des situations analogues (~35) mais dont on connaissait cette fois les précipitations sur le bassin de l'Isère, d'où une appréciation probabiliste des quantités potentiellement tombées en 1859. En utilisant ce signal, ainsi que les précipitations mesurées en 1859 en quelques stations, toutes situées en périphérie du bassin, l'INPG-LTHE a essayé de proposer un scénario vraisemblable des précipitations, mais aussi des températures, sur l'Isère et ses différents sous-bassins. Après expertise par EdF et Météo-France, ce scénario a été introduit dans un modèle Pluie-Neige-Débit par le SPC Alpes Nord. La comparaison entre débits simulés et observés à Grenoble sur le mois d'octobre 1859 a conduit à moduler encore un peu le scénario, insuffisamment contraint par les seules stations pluviométriques. Après assimilation de ces débits de crue, qu'il reproduit alors correctement, le scénario final illustre l'enchaînement et l'importance des périodes d'humectation du bassin par les pluies du 7 au 20 octobre, d'accumulation de neige à basse altitude entre le 21 et le 30, puis son relargage sous l'effet du réchauffement et des pluies intenses des 31 octobre et 1er novembre. C'est cette séquence exceptionnelle qui explique l'ampleur de la crue. / Reconstructing the hydrometeorological scenario that has lead to the 1859 historical flood of the Isère river has been performed in four steps. In the first one, Meteo-France has searched for, collected, and criticized old data sets still available, in particular at stations measuring the atmospheric pressure, in France or nearby. This allowed to reconstruct sea level pressure fields for the month of October 1859, and to interpret them in terms of circulation and weather types. For each single day of 1859, this pressure map was used by Cemagref to sort out, within the recent period (1953-2008), analog situations (~35) for which we further have the precipitations on the Isère catchment, giving therefore a probabilistic hint of what has potentially been received in 1859. Using this signal, combined with the precipitation actually observed in 1859 at a few stations, unfortunately all located outside the catchment, INPG-LTHE has proposed a likely scenario for precipitation amounts, but also for temperature, over the whole catchment and several subbasins. This scenario has gone through the expertise of EdF and MeteoFrance forecasters, and then defines inputs in a Snow-Rainfall-Runoff model developed by the SPC Alpes Nord. Comparisons between simulated and observed daily discharges lead to some further tuning of the scenario, insufficiently constrained by the few rain gauges available. After the assimilation of the downstream discharges, the resulting scenario reproduces well the flood peak and illustrates how important was the links between a wetting phase by the 7 to 20th October rainfalls, then the build up of a snowpack even at low elevation from the 21 to the 30th, and then its washing out by the strong warming and intense rains of October 31st and November 1st. This is this very unusual sequence that explain the high return period of this flood.

A new database of weather and circulation type catalogs is presented comprising 17 automated classification methods and five subjective classifications. It was compiled within COST Action 733 “Harmonisation and Applications of Weather Type Classifications for European regions” in order to evaluate different methods for weather and circulation type classification. This paper gives a technical description of the included methods using a new conceptual categorization for classification methods reflecting the strategy for the definition of types. Methods using predefined types include manual and threshold based classifications while methods producing types derived from the input data include those based on eigenvector techniques, leader algorithms and optimization algorithms. In order to allow direct comparisons between the methods, the circulation input data and the methods’ configuration were harmonized for producing a subset of standard catalogs of the automated methods. The harmonization includes the data source, the climatic parameters used, the classification period as well as the spatial domain and the number of types. Frequency based characteristics of the resulting catalogs are presented, including variation of class sizes, persistence, seasonal and inter-annual variability as well as trends of the annual frequency time series. The methodological concept of the classifications is partly reflected by these properties of the resulting catalogs. It is shown that the types of subjective classifications compared to automated methods show higher persistence, inter-annual variation and long-term trends. Among the automated classifications optimization methods show a tendency for longer persistence and higher seasonal variation. However, it is also concluded that the distance metric used and the data preprocessing play at least an equally important role for the properties of the resulting classification compared to the algorithm used for type definition and assignment.

EnglishAs part of its mission to preserve climate history, Meteo-France has begun the process of saving ancient climate data. This rescue of historical climate data entails not only exhaustive searches and preservation efforts of such archives, but also the characterization and dissemination of the associated data and meta-data. The primary aim for this effort is to contribute to climate research, by enriching national and international climate databases with these historical meteorological observations. This paper describes comprehensively the data rescue process, from identification to analysis, and shows how the resulting, often unpublished, information contributes to the understanding of climate evolution. francaisDans le cadre de sa mission de conservation de la memoire du climat, Meteo-France s'est engage dans l'action de sauvetage de donnees anciennes climatologiques. Cette action de sauvetage suppose la recherche et la conservation des archives meteorologiques, la recuperation, la qualification et la mise a disposition des donnees et des metadonnees qu'elles contiennent. Son premier objectif est de contribuer a la recherche sur le climat et, a cette fin, d'enrichir les bases de donnees climatologiques nationales et internationales pour rendre accessibles les observations meteorologiques historiques. Cet article presente la chaine du sauvetage et du traitement des donnees anciennes, puis illustre l'apport de ces informations, souvent inedites, pour le diagnostic sur l'evolution du climat.

The refusal to permit organ sampling is of around 30% and is one of the principle causes for the lack of sampling. This study was aimed at establishing the frequency of decisions taken with regard to donations and the factors associated with refusal.A prospective study was conducted between April 2, 2000 and March 31, 2001 in hospitals authorised to perform organ sampling in the Western area of France. For each potential donor identified, a questionnaire was filled in after each interview. A logistical model was used in order to identify the independent and statistical factors associated with the refusal to allow sampling of an organ or tissue.Among the potentials donors, 265 brain dead donors, and 868 donors with ceased heart beats for tissue sampling, were included. The refusal rate was of respectively 32.8 and 45 %. Only 2.4% of potential donors carried cards identifying them as such. While living, the rate of refusal expressed by the two types of potential donors was similar (9%). The brain dead potential donors had more frequently expressed their consent for donation (20.7 vs. 9%). In the organ donors, the interviews were conducted by two persons in only 37.9% of cases, and in 2.4% of cases of potential tissue donors. In the potential organ donors, only those with a card identifying them as such and the hesitations of the family at the start of the interview were significantly associated with a lesser frequency of refusal. In potential tissue donors, the hesitations of the family reduced the refusal rate but age, religious beliefs, death etiology and the person conducting the interview increased it.The encouraging efforts made for the awareness of donation during a person's lifetime must continue and the use of a donor card extended. The development of co-ordination posters in the hospitals would enhance the development of binomial interviews with the families.

EnglishA new dataset of monthly homogeneous series of temperature has been produced by Meteo-France. It provides an unprecedented coverage of the metropolitan territory, with 228 minimum and 251 maximum temperature series of high quality. It allows a robust estimate of the French temperature evolution from the 1950s to the late 2000s. This new dataset is consistent with both a former set of French series covering the 20th century and international datasets, in term of trends and interannual variability. However, it provides a more precise diagnosis at local scale. From 1959 to 2009, the mean warming over France (+0.3 °C per decade) is mainly explained by spring and summer temperatures increase. It is greater than the one experienced over the 20th century (+0.1 °C per decade), due to an acceleration of the warming since the 1970s. francaisMeteo-France vient de produire un nouveau jeu de series homogeneisees mensuelles de temperatures. Ce sont 228 series de temperature minimale et 251 series de temperature maximale qui couvrent tout le territoire metropolitain avec une qualite et une densite inegalees. Ces series de reference permettent de faire un diagnostic fiable de l'evolution des temperatures en France metropolitaine depuis les annees 1950 jusqu'a la fin des annees 2000. Le nouveau jeu montre une bonne coherence des tendances et de la variabilite en moyenne sur la France, avec les series produites precedemment disponibles sur le XXe siecle, ainsi qu'avec un jeu de donnees international. Il apporte cependant un diagnostic plus precis, et a une echelle locale, sur les dernieres decennies. Le rechauffement moyen annuel sur la France est d'environ +0,3 °C par decennie sur la periode 1959-2009 et s'explique principalement par l'augmentation des temperatures au printemps et en ete. Il est nettement plus fort que la tendance de +0,1 °C par decennie precedemment etablie sur tout le XXe siecle, a cause d'une acceleration du rechauffement depuis les annees 1970.

EnglishHomogenised series of temperature and precipitation data for the late 20th century in New-Caledonia are presented. Annual mean minimum and maximum temperatures have increased by 0.3 and 0.2°C per decade respectively.A quantile-quantile downscaling method has been performed on IPCC AR4 numerical simulations in order to study the impact of climate change on New-Caledonia in the future. The minimum and maximum temperatures would increase by between 1.5 and 2.7°C by the end of the 21st century, relative to the 1971-1999 period, depending on greenhouse gases emission scenarios. It also appears that the temperature of the future would support an increase in the frequency of the years that climatically favour outbreaks of dengue fever. No significant trend appears in observations of total annual precipitation, or in projections. francaisLes longues series d'observations de temperatures et de precipitations de la fin du XXe siecle en Nouvelle-Caledonie ont ete homogeneisees puis analysees. Les moyennes annuelles des temperatures minimales et maximales ont augmente respectivement de 0,3 et 0,2 °C par decennie sur la periode 1970-2009. Les effets futurs du changement climatique en Nouvelle-Caledonie ont ete etudies en effectuant une descente d'echelle par la methode quantile-quantile a partir de simulations numeriques realisees pour le quatrieme rapport du GIEC. Selon les scenarios d'emissions de gaz a effet de serre, l'augmentation des temperatures minimales et maximales se situerait entre +1,5 et +2,7 °C en un siecle, relativement a la periode 1971-1999. Il apparait egalement que les conditions de temperature du futur entraineraient une augmentation de la frequence des annees meteorologiquement favorables aux epidemies de dengue. Quant aux cumuls annuels de precipitations, aucune tendance significative n'apparait, ni dans les observations, ni dans les projections.

EnglishThe authors propose a way to classify windstorms based on the expert knowledge of weather forecasters. This would provide insurance companies with meteorological statistics so that they could evaluate storm risks; they would also be able to calculate statistical values on groups of windstorms with meteorological and geographical similarities. A forecaster analysed fifty storms and put them in twelve categories. The criteria were then automated using rules which depend only on observed surface meteorological data. The automated scheme was then applied to Meteo-France records since 1962. As a result 524 events were selected as storms and we class them into seven main types. francaisUne methode de classification des tempetes, fondee sur l'expertise d'un previsionniste, est proposee, afin de fournir a des compagnies d'assurance et de reassurance les elements meteorologiques permettant de quantifier l'intensite des dommages dus aux vents forts et d'effectuer des calculs statistiques sur des groupes de tempetes qui presentent des caracteristiques meteorologiques et geographiques communes. Un previsionniste analyse une cinquantaine de situations de tempetes et met ainsi en evidence les caracteristiques meteorologiques de douze types de tempetes. Les resultats de cette typologie sont ensuite automatises grâce a la determination de regles decisionnelles reposant sur des criteres calculables a partir de donnees meteorologiques observees au sol. En utilisant les donnees archivees de Meteo-France depuis 1962, on parvient alors a selectionner 524 situations de vents forts et a les classer, de facon automatique, en sept grands types de tempetes.

EnglishUsing climatic data to study climatic change requires the implementation of some successive methods of data processing. After an initial test of spatial consistency, missing data are reconstituted by the Aurelhy method. Then, the homogeneity of the series should be tested. As it is difficult to explain the results of internal homogeneity tests, relative homogeneity has to be studied and reference series used. Taking the great variability of the climate in the southeastern part of France into account, results particularly demonstrate the interest of the Alexandersson method. An attempt to correct detected inhomogeneities can then be made by using the stations' historical data. After data have been processed, it becomes realistic to search for climatic trend. Results confirm previous studies, with specially the detection of a nocturnal warming. francaisL'utilisation des donnees climatiques pour la connaissance de l'evolution du climat necessite la mise en oeuvre d'un certain nombre d'operations successives de traitement des donnees. Apres un controle initial de coherence spatiale, les donnees manquantes sont reconstituees a l'aide de la methode Aurelhy. Il faut ensuite tester l'homogeneite des series. Les tests d'homogeneite interne etant difficiles a interpreter, on se tourne vers l'homogeneite relative et le calcul de series de reference. L'analyse des resultats, integrant la grande variabilite du climat de la zone etudiee (Sud-Est de la France), montre en particulier l'interet de la methode d'Alexandersson. En utilisant l'historique des postes, une tentative de correction des heterogeneites detectees est ensuite menee. Ce n'est qu'apres cette chaine de traitement des donnees que la recherche d'une tendance peut etre abordee. Les resultats obtenus corroborent les etudes precedentes, avec en particulier la mise en evidence d'un rechauffement nocturne.

EnglishA System of local forecasting of minimum screen temperatures and actinothermal indices at 10 cm height in four sites of the Champagne vineyard, two located dovvn slope and two located at mid-slope, has been developed. This System combines the use of output data of the generai numerical weather forecasting (cloud cover, wind speed and direction), of a simplified simulation model of night air cooling on flat terrain in the case of a clear sky anticyclonic situation, and a procedure for local adaptation for the calculation of air temperatures in the vineyard. This third step is based on a topoclimatic study done previously, using 9-year temperature data series, which enabled us to calculate thermal differences between a site within the wine region and the reference synoptical station (in Reims), as a function of the wind direction. This forecasting System, activated at 15 h UTC for the next morning, has been tested during spring 1989 (50 nights altogether). The results of the tests are the following : for clear sky nights (18 nights out of 50) the mean absolute deviation between observed and forecasted values of minimum screen temperature in Reims is 1.7°C. The absolute deviation (calculated over these 18 nights) between observed values and forecasted values of the actinothermal index is less than 1.5°C in 5 0% of the cases with some differences between sites. The diagnosis of frost risk, defined as the occurrence of an actinothermal index (i.e. surface temperature) less than -2.5°C, has been successf ully forecasted for the most frost-exposed site. francaisCet article presente un systeme de prevision des temperatures minimales sous abri et des indices actinothermiques en quatre points du vignoble champenois : Avize, Bouzy, Chambrecy, Mailly. Les differentes etapes de realisation de la prevision sont decrites : utilisation des donnees de la prevision generale, utilisation eventuelle d'un logiciel de simulation de refroidissement nocturne par temps anticyclonique, et adaptation locale. Cette derniere necessite une etude topoclimatique prealable des series de mesures thermometriques observees aux quatre sites. Le systeme a ete teste au cours des printemps 1988 et 1989 par la station meteorologique de Reims, la prevision etant realisee a 15h UTC pour la nuit suivante. Les resultats du test de l'annee 1989 sont les suivants: pour les nuits de ciel clair l'ecart absolu moyen entre valeurs observees et prevues de la temperature minimale sous abri a Reims est de 1,7°C tandis que l'ecart absolu moyen entre valeurs observees et prevues de l'indice actinothermique est inferieur a 1,5°C dans 6 0% des cas a Avize et Mailly. Pour Chambrecy, le poste le plus gelif, les quatre nuits avec risque de gel ont ete correctement prevues, une fausse alerte ayant ete declenchee une seule fois.