Avalanche extremes and atmospheric circulation patterns

Birkeland, Karl W.; Mock, Cary J.; Shinker, Jacqueline J.

doi:10.3189/172756401781819030

Cited by 47 publications

(26 citation statements)

References 25 publications

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“…The centroids are calculated by averaging . Scree test and North rule of thumb, two empirical techniques, used in the selection of principal components to be retained for rotation the days that fulfil the principle of the 'extreme scores' for a certain pattern and phase: observations with high score values for a certain component (values higher than +2 for the positive phase, or lower than −2 for the negative phase) but with low score values for the remainder (between +2 and −2) were selected (Tait and Fitzharris, 1998;Birkeland et al, 2001;Kostopoulou, 2003). Using this technique, if there is no real case that could be assigned to the PC that we are checking (i.e.…”

Section: Clusteringmentioning

confidence: 99%

Daily atmospheric circulation catalogue for western Europe using multivariate techniques

Esteban

Martín‐Vide

Mases³

2006

Intl Journal of Climatology

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This study uses principal component analysis (PCA) and clustering (CL) techniques to characterize the daily surface synoptic circulation patterns over the region 30°N-60°N by 30°W-15°E, for the period 1960-2001 using the NCEP/NCAR Reanalysis Project data. The methodology used, previously proposed by Esteban et al. (2005) to identify heavy snowfall days over Andorra (Pyrenees), involves a pre-processing approach consisting of a spatial standardization of the data used for the rotated PCA on S-mode analysis and correlation matrix, and Varimax rotation of the retained components. For the clustering process, an alternative approximation based on the PCA results (positive and negative phases) to decide the centroids and the number of groups for the K-means clustering is shown, followed by the rejection of the iterations for this non-hierarchical algorithm. Twenty sea level pressure (SLP) circulation patterns were obtained, with all days classified. The composite maps for SLP and 500 hPa geopotential height (GPH), the monthly distribution, and the long-term variability for each of the circulation patterns is obtained. The results are consistent with the subjective knowledge of the daily atmospheric circulation over the area treated, and seem to be an easy and accessible way for the synoptic studies of short-lived (from weekly to daily) phenomena. In addition, this methodology appears to be applicable to all climatic areas of the world, as it characterizes well enough the complex circulation variability at mid-latitudes, including the surface low-pressure gradient patterns normally located over the Mediterranean in summer.

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Section: Clusteringmentioning

confidence: 99%

Daily atmospheric circulation catalogue for western Europe using multivariate techniques

Esteban

Martín‐Vide

Mases³

2006

Intl Journal of Climatology

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“…Smith and McClung, 1997), but good correlations between periods of high avalanche activity and synoptic variables have also been identified (e.g. Birkeland et al, 2001). Although still a field of ongoing research, avalanche statistical forecasting models able to work in an Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Section: Introductionmentioning

confidence: 99%

Snow and weather climatic control on snow avalanche occurrence fluctuations over 50 yr in the French Alps

Castebrunet

Eckert²,

Giraud

2012

Clim. Past

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Abstract. Snow avalanche activity is controlled to a large extent by snow and weather patterns. However, its response to climate fluctuations remains poorly documented. Previous studies have focused on direct extraction of trends in avalanche and winter climate data, and this study employs a time-implicit method to model annual avalanche activity in the French Alps during the 1958-2009 period from its most representative climatic drivers. Modelled snow and weather data for different elevations and aspects are considered as covariates that explain actual observed avalanche counts, modelled instability indexes, and a combination of both avalanche activity indicators. These three series present relatively similar fluctuations over the period and good consistency with historically harsh winters. A stepwise procedure is used to obtain regression models that accurately represent trends as well as high and low peaks with a small number of physically meaningful covariates, showing their climatic relevance. The activity indicators and their regression models seen as time series show, within a high interannual variability, a predominant bell-shaped pattern presumably related to a short period of colder and snowier winters around 1980, as well as a very slight but continuous increase between 1975 and 2000 concomitant with warming. Furthermore, the regression models quantify the respective weight of the different covariates, mostly temperature anomalies and south-facing snowpack characteristics to explain the trends and most of the exceptional winters. Regional differences are discussed as well as seasonal variations between winter and spring activity and confirm rather different snow and weather regimes influencing avalanche activity over the Northern and Southern Alps, depending on the season.

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“…Specific surveys were done by Calondar (1986) and Hächler (1987) for Switzerland by Fitzharris and Bakkehoi (1986) for Norway and by Birkeland and Mock (2001) and Birkeland et al (2001) for North America. In Austria, only a little research has been done.…”

Section: Introductionmentioning

confidence: 99%

Avalanche cycles in Austria: an analysis of the major events in the last 50 years

Höller

2008

Nat Hazards

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During the last 50 years, an average of 30 persons per year was killed by avalanches in Austria. About one-third of all avalanche fatalities occurred as a result of socalled 'catastrophic avalanches'. 'Catastrophic avalanches' are spontaneously released avalanches that affect villages and cause damage to property (buildings, roads and other infrastructure). The biggest avalanche events in Austria were in 1950Austria were in /1951Austria were in (135 fatalities), in 1953Austria were in /1954 and in February 1999, when 38 persons were killed in Galtür and Valzur. This article deals with an analysis of nine major avalanche cycles in the last 55 years. An avalanche cycle in this article is defined as 50 recorded avalanches of at least size 3 in two days and/or 5 persons killed in villages within two days. The basis of this study are the well-documented records from Fliri (1998), who analysed natural disasters in the western part of Austria and the Trentino, including floods, mudflows, earthquakes and avalanches. The meteorological data were taken from two relevant observation sites in the northern part of the Austrian Alps, from two sites in an intermediate and continental region, respectively and from one site in the southern part of the Austrian Alps. Atmospheric patterns were analysed by using weather charts for the relevant periods. Both the meteorological data and the weather charts were provided by the Central Institute for Meteorology and Geodynamics (ZAMG). It was found that there was a major cycle every 6 years (on average). Two-thirds of all investigated cycles were characterised by a continuous increase of snow depth over a period of at least three days. In only three periods (1975, 1986, 1988), daily extreme values could be observed. More than 40% of all the cycles occurred in January. In two-thirds, a north-westerly oriented frontal zone was responsible for the formation of a major cycle. The remaining cycles were released by lowpressure areas over Central Europe and the Mediterranean Sea, respectively.

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Avalanche extremes and atmospheric circulation patterns

Cited by 47 publications

References 25 publications

Daily atmospheric circulation catalogue for western Europe using multivariate techniques

Daily atmospheric circulation catalogue for western Europe using multivariate techniques

Snow and weather climatic control on snow avalanche occurrence fluctuations over 50 yr in the French Alps

Avalanche cycles in Austria: an analysis of the major events in the last 50 years

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