Référence
bibliographique complète 
JOMELLI V., DELVAL C., GRANCHER D., ESCANDE S., BRUNSTEIN D., HETU B., FILION L., PECH P. Probabilistic analysis of snow avalanches
and climate relationships in the French Alps since the 1980's. Cold Regions Science and Technology, 2007, Vol. 47, p. 180192. 
Motsclés 
Snow avalanche, climate, statistic modelling, occurrence probability, French Alps 
Organismes / Contact 
CNRS Laboratoire de Géographie Physique, UMR 8591, Meudon Bellevue,
IRD, UR Great Ice, Montpellier,
Université Paris 1, Panthéon Sorbonne CEMAGREF Division ETNA, St Martin d’Hères CEN, Université Laval, Québec jomelli@cnrsbellevue.fr 
(1)
 Paramètre(s) atmosphérique(s) modifié(s) 
(2)
 Elément(s) du milieu impacté(s) 
(3)
 Type(s) d'aléa impacté(s) 
(3)
 Soustype(s) d'aléa 
Avalanches 
Pays
/ Zone 
Massif
/ Secteur 
Site(s) d'étude 
Exposition 
Altitude 
Période(s)
d'observation 
French Alps 
Maurienne Massif 
Valloire valley 
Eastwest orientation (for the valley) 
24003200 m asl (triggering zones) 
19782003 
(1)
 Modifications des paramètres atmosphériques 

Reconstitutions  
Observations 

Modélisations 

Hypothèses 
Informations complémentaires (données utilisées, méthode, scénarios, etc.) 

(2)
 Impacts du changement climatique sur le milieu naturel 

Reconstitutions  
Observations 

Modélisations 

Hypothèses 
Sensibilité du milieu à des paramètres climatiques 
Informations complémentaires (données utilisées, méthode, scénarios, etc.) 
(3)
 Impacts du changement climatique sur l'aléa 

Reconstitutions  
Observations 
Daily basis results: Annual basis results: Link with the NAO: 
Modélisations 

Hypothèses 
Paramètre de l'aléa 
Sensibilité du paramètres de l'aléa à des paramètres climatiques 
Informations complémentaires (données utilisées, méthode, scénarios, etc.) 
Avalanche frequency  Temperature and precipiation parameter (32 meteorological parameters have been used) 
Data used in this study are from a survey of avalanches longer than 200m called EPA (Enquête Permanente des Avalanches). Daily precipitation and temperature data from the Valloire meteorological station (1460 m asl) were used. 32 meteorological parameters were tested on a daily basis: precipitation; mean, minimum and maximum temperatures; and thermal amplitude on the day of a given avalanche event, as well as 1, 2, and 3 days before a given event cumulated or not. 12 parameters were tested on an annual basis: winter mean precipitation, intense precipitations, number of times it rained during 2 or 3 successive days in a winter, freezethaw alternation, temperature anomalies… The weather classification at 500, 700, and 850 hp was also used to evaluate the relationship between avalanche occurrence and any special synoptic situation. The NAO Hurell Index (pressure ratio between Reykjavik and Lisbon) was used to test the teleconnection hypothesis. The probability model used has evaluated uncertainties associated with discrepancies between the climate at meteorological stations and at avalanche sites. The effects of climatic variables on avalanche initiation were simulated using a logistic regression model. All variables considered on a daily and annual basis were systematically tested. All statistically significant variables were retained for further analysis. Finally, bootstrap analyses were performed to test the global sensitivity of models. This method employs sampling with replacement from unique original data set. The values of the different variables of the new samples are identical to the original but the frequencies may be different. If the mean of parameters in the simulated samples was close to the parameters in the original data set, the statistical stability of the model was deduced. 
(4)  Remarques générales 

(5)
 Syntèses et préconisations

