Contenu du sommaire : A propos de la séquence neigeuse de décembre 1990 : Une approche des évènements extremes
Revue |
Géocarrefour Titre à cette date : Revue de géographie de Lyon |
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Numéro | volume 66, no 3, 1991 |
Titre du numéro | A propos de la séquence neigeuse de décembre 1990 : Une approche des évènements extremes |
Texte intégral en ligne | Accessible sur l'internet |
- Comité de rédaction - p. 2
- Introduction - Marcel Leroux p. 138
- Sur la nature des événements extrêmes : catastrophe et cataclysme / On the nature of exceptional events : catastrophe and cataclysm - Jacques Bethemont p. 139-142 Exceptional events should be evaluated on the basis of two normative scales ; one, an objective measure of the event, the other a subjective view of the way it is perceived. On this basis a semantic distinction is proposed between the notion of catastrophe, based on objective analysis, and that of cataclysm which refers to terrifying events of the past. In scientific literature the two approaches are often combined, although authors do not always recognise the change from one to the other. Be that as it may, a catastrophe often reveals the cohesion or helplessness of groups when faced with such an event, and it is reasonable to assume that catastrophic changes (such as those of a demographic or climatic nature) provoke major cultural changes.
La séquence neigeuse du 8 au 13 décembre 1990 dans la région Rhône-Alpes / ~~The period of snowfall from the 8-13 December 1990 in the Rhône-Alpes region~~
- Chronologie des catastrophes neigeuses dans le sud-est de la France / Chronology of the exceptional snowfall in south-east France - Gérard Staron p. 143-150 Five important climatic disasters relating to heavy snowfall affected the south of France prior to December 1990 : at the end of December 1970, the 20 and 21 December 1978, the 11 and 12 January 1981, the 26 November 1982 and between the 28 January and the 4 February 1986. Their atmospheric origin and location were strongly influenced by the Mediterranean region. The severe impact of such snowfall, increased by its high density, led to cuts in power supplies, telephone links and landward transport systems, as well as damage to property ; as a result, plans for dealing with such emergencies were put into operation (Plan ORSEC).
- L'épisode neigeux de décembre 1990 dans la région Rhône-Alpes : les aspects météorologiques / The period of heavy snowfall during December 1990 in the Rhône-Alpes region - Jean-Claude Deblaere, Guy Blanchet p. 151-160 Exceptionally heavy falls of snow affected part of the Rhône-Alpes region during the month of December 1990. These snowfalls were unusual due to their intensity and, above all, to their location, affecting essentially areas of low altitude. Typically this situation was caused by the arrival of warm, humid air from the south confronting a mass of cold, northern air, blocking depressions in advance of the Alps. A difference in temperature of only a few degrees produced a memorable result.
- La dynamique des épisodes neigeux du 8 au 13 décembre 1990 dans la région Rhône-Alpes / The dynamics of the snowfall periods in the Rhône-Alpes region from the 8-13 December 1990 - Marcel Leroux p. 161-168 Despite the existence of an apparently normal meteorological situation, both in terms of the season and isobaric pattern, snowfall occur ed in lowland areas. Initially the snow was wet and damp. Snowfall was spread over five days, covering in fact two distinct periods. The first, and longest with the heaviest falls, concerned the 8th, 9th and 10th December. The day of the 11th was a transition to the second, shorter period covering the 12th and 13 th December. These events were the result of different forms of interference between the aerological factor chiefly represented by two Polar Mobile Highs, and the topographical conditions of the Rhône corridor.
- La séquence de fort enneigement de décembre 1990 dans le département de la Loire / The sequence of heavy snowfall in the Department of the Loire during December 1990 - Jean-Bernard Suchel p. 169-176 Studies at the level of the commune in the Loire Department provide information on the depth and duration of snowfall. In adition, they offer details of the socio-economic consequences of this event. A number of critical issues are then examined in relation to the development fo these events : the heavy and sticky snow on the 9 December damaged principally electricity and telephone lines at medium and low altitudes, whereas the accumulation of snow and the formation of drifts, especially on the 13th, paralysed in particular road traffic and damaged buildings in mountainous areas, notably the Pilat.
- Les conséquences économiques et sociales de la séquence neigeuse de décembre 1990 sur la région Rhône-Alpes / The social and economic consequences of the period of snowfall in December 1990 on the Rhône-Alpes region - Jacques Comby p. 177-190 The period of heavy snowfalls which affected the Rhône-Alpes region from the 9 December to 14 December 1990 seriously disrupted regional economic activity. Assessment of the socio-economic consequences shows that disruption and damage were concentrated in the Departments of Ain and Isère, where the problems were seen as a real economic crisis. However, the inhabitants of the region saw the constraints they underwent in different ways, rendering subjective attempts to assess the real extent the phenomenon.
- Chronologie des catastrophes neigeuses dans le sud-est de la France / Chronology of the exceptional snowfall in south-east France - Gérard Staron p. 143-150
Des évènements extremes / ~~Exceptional Events~~
- Bilan cartographique de la sécheresse dans la moyenne vallée du Rhône d'octobre 1988 à septembre 1990 / A cartographie assessment of the drought in the middle-Rhone valley between October 1988 and September 1990 - Stéphane Aubert p. 191-196 The inclusive period between October 1988 and September 1990 has left its imprint on the recent meteorological history of the whole of Western Europe. All French regions were affected by a strong rainfall deficiency. Nevertheless, the conceptual perception of drought (i.e. its sociological approach) indicates important regional differences. In this context the middle Rhône-Saône corridor (between Mâcon to the north and Montélimar in the south), an extended area of climatic transition, illustrates this variety of perception. It is thus shown that crude statistics are inedaquate to realistically assess the conceptual approach to drought.
- Déficit pluviométrique hivernal sur la France : autopsie de la situation anticyclonique du 19 décembre 1989 au 25 janvier 1990 / The winter rainfall deficiency in France : autopsy of the anticyclonic situation from the 19 December 1989 to the 25 January 1990 - Marcel Leroux p. 197-206 The 1989-90 winter rainfall deficiency was connected with an unusually long-lived high pressure pattern. Below the anticyclonic cover were observed above normal diurnal temperatures but a strong rainfall deficiency, while the northern and southern borders of the high pressure mass had the advantage of copious rainfall. The immense «European » high does not have a «local » origin, that is to say a thermic continental one, and was not an inert airmass; instead the high pressure was continuously supplied by Polar Mobile Highs (PMH), that is to say thin layered and migratory cold airmasses, originating from the arctic basin. The PMH (a total of 25 out of 39 days) move, either along the western side of Greenland (17 for this «American » path), or along the eastern side (8 for this « Scandinavian » path). Their meeting over Europe and blocking by the PMH which have denser air due to their more direct trajectories provokes an agglutination high pressure cells over Europe.
- Vents maximums en Savoie et impact des tempêtes durant l'hiver 1989-1990 / Gale-force winds in the Department of Savoie and the impact of storms during the winter of 1989-90 - L. Boulanaache, Michel Mietton, Alain Marnezy p. 207-221 The winter of 1989-90 in the department of Savoie was marked by two periods of extremely high winds. Their dates, speeds and directions are compared with the general characteristics of such winds using long- series data from observations made at Voglans (Chambéry). Although periods of high winds occur virtually each year, seldom is the damage as great as in December 1989 and February 1990. The maximum instantaneous speeds reached record values - particularly at high altitude - but this is insufficient to account for the strength of the winds' impact. Both the intensity and the duration of the squalls, together with the structure of the forest and ground conditions - as in the case of fallen trees - influenced the situation. The cost of the damage which occurred in the west of the department in December and essentially in the east in February will amount to a minimum of 100 millions francs, to which must be added economic and ecological effects which are more difficult to estimate. The manner in which insurance policies cover such rises means that the victims of damage are unlikely to be fully reimbursed.
- R. Brousse, C. Lefèvre, Le volcanisme en France - Gérard Mottet p. 222
- L'anastrophe japonaise / The Japanese anastrophe - Philippe Pelletier p. 223-230 Generations of Japanese people have shown their ability to adapt to the constraints of their physical environment and, as far as possible, to natural disasters. This adaptation, making use of favourable elements of the environment, cannot be disassociated from economic choices such as rice culture which, with rapid urbanisation, is creating new problems. Japanese people consider, therefore, the nature of their archipelago more beneficial than evil.
- Une catastrophe d'origine administrative, l'aménagement de la Volga par la bureaucratie / An administrative disaster : the bureaucratie development of the Volga - Pascal Marchand p. 231-237 Soviet authorities wanted a major development of the Volga river despite the adverse consequences for the environment. The bureaucratic management of falls, a specifically Soviet characteristic, is explained by the subordinate role accorded to society by the state. Fortunately the consequences of this situation are not irreversible.
- Bilan cartographique de la sécheresse dans la moyenne vallée du Rhône d'octobre 1988 à septembre 1990 / A cartographie assessment of the drought in the middle-Rhone valley between October 1988 and September 1990 - Stéphane Aubert p. 191-196
- Chronique météorologique : Le temps dans la région Rhône-Alpes en 1988 / Weather in the Rhône-Alpes region during 1988 - Guy Blanchet p. 239-252