On using local avalanche danger level estimates for regional forecast verification

Techel, Frank; Schweizer, Jürg

doi:10.1016/j.coldregions.2017.07.012

Cited by 34 publications

(64 citation statements)

References 13 publications

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“…This finding does not mean that triggering becomes less likely but rather reflects terrain usage and the effect of avalanche warnings. In fact, Techel et al (2015) showed a decrease in ski touring activity already from level 2-Moderate to 3-Considerable and even more prominently from level 3-Considerable to 4-High. On the other hand, Wäger and Zweifel (2008) found no decrease in frequency usage from levels 2-Moderate to 3-Considerable when considering offpiste skiing.…”

Section: Discussionmentioning

confidence: 93%

“…Previously, it was suggested that the hazard would double from one level to the other (Munter, 2003). Using accident data a 2-to 3-fold increase was shown (Pfeifer, 2009;Techel et al, 2015), whereas a survey among North American avalanche professionals suggested a 10-fold increase in triggering probability when the regional danger increases by one level (Jamieson et al, 2009b). Based on avalanche observations from Colorado, Elder and Armstrong (1987) assigned avalanche frequencies per day to the four danger levels that were in use at those times: 0-3, 4-9, 10-20 and ≥ 21.…”

Section: Discussionmentioning

confidence: 99%

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On the relation between avalanche occurrence and avalanche danger level

Schweizer¹,

Mitterer²,

Techel³

et al. 2020

The Cryosphere

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Abstract. In many countries with seasonally snow-covered mountain ranges warnings are issued to alert the public about imminent avalanche danger, mostly employing an ordinal, five-level danger scale. However, as avalanche danger cannot be measured, the characterization of avalanche danger remains qualitative. The probability of avalanche occurrence in combination with the expected avalanche type and size decide on the degree of danger in a given forecast region (≳100 km2). To describe avalanche occurrence probability, the snowpack stability and its spatial distribution need to be assessed. To quantify the relation between avalanche occurrence and avalanche danger level, we analyzed a large data set of visually observed avalanches (13 918 in total) from the region of Davos (eastern Swiss Alps, ∼300 km2), all with mapped outlines, and we compared the avalanche activity to the forecast danger level on the day of occurrence (3533 danger ratings). The number of avalanches per day strongly increased with increasing danger level, confirming that not only the release probability but also the frequency of locations with a weakness in the snowpack where avalanches may initiate from increase within a region. Avalanche size did not generally increase with increasing avalanche danger level, suggesting that avalanche size may be of secondary importance compared to snowpack stability and its distribution when assessing the danger level. Moreover, the frequency of wet-snow avalanches was found to be higher than the frequency of dry-snow avalanches for a given day and danger level; also, wet-snow avalanches tended to be larger. This finding may indicate that the danger scale is not used consistently with regard to avalanche type. Even though observed avalanche occurrence and avalanche danger level are subject to uncertainties, our findings on the characteristics of avalanche activity suggest reworking the definitions of the European avalanche danger scale. The description of the danger levels can be improved, in particular by quantifying some of the many proportional quantifiers. For instance, based on our analyses, “many avalanches”, expected at danger level 4-High, means on the order of at least 10 avalanches per 100 km2. Whereas our data set is one of the most comprehensive, visually observed avalanche records are known to be inherently incomplete so that our results often refer to a lower limit and should be confirmed using other similarly comprehensive data sets.

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Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

On the relation between avalanche occurrence and avalanche danger level

Schweizer¹,

Mitterer²,

Techel³

et al. 2020

The Cryosphere

Self Cite

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show abstract

“…However, forecast accuracy generally decreases with lead time (Jamieson et al, 2008;Statham et al, 2018b). Forecast accuracy may also vary within forecast center domains, as shown by Techel and Schweizer (2017) for the case of Switzerland. We suspect that these may primarily affect the agreement rate P agree , except if the forecast bias differs temporally or spatially.…”

Section: Methodsmentioning

confidence: 99%

“…We refer to danger levels D either using their integer value (e.g., D = 1 for 1 -low) or by integer value and signal word combination 1 -low. Similarly to previous studies (e.g., Jamieson et al, 2008;Techel and Schweizer, 2017), we use the integer value of danger levels to calculate proportions and differences.…”

Section: Avalanche Danger Level Statisticsmentioning

confidence: 99%

“…Thresholds for the color classes were defined using the Fisher-Jenks algorithm minimizing within-class variation (Slocum et al, 2005; R package classInt: Bivand, 2017). Techel and Schweizer, 2017). Similar to VDA, each of the Swiss warning regions can be linked to a higher-order spatial hierarchy (SLF, 2015, p. 41) 3 .…”

Section: Size Of the Warning Regions P Vcrit And Spatial Variatiomentioning

confidence: 99%

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Spatial consistency and bias in avalanche forecasts – a case study in the European Alps

Techel

Mitterer

Ceaglio

et al. 2018

Nat. Hazards Earth Syst. Sci.

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Abstract. In the European Alps, the public is provided with regional avalanche forecasts, issued by about 30 forecast centers throughout the winter, covering a spatially contiguous area. A key element in these forecasts is the communication of avalanche danger according to the five-level, ordinal European Avalanche Danger Scale (EADS). Consistency in the application of the avalanche danger levels by the individual forecast centers is essential to avoid misunderstandings or misinterpretations by users, particularly those utilizing bulletins issued by different forecast centers. As the quality of avalanche forecasts is difficult to verify, due to the categorical nature of the EADS, we investigated forecast goodness by focusing on spatial consistency and bias, exploring real forecast danger levels from four winter seasons (477 forecast days). We describe the operational constraints associated with the production and communication of the avalanche bulletins, and we propose a methodology to quantitatively explore spatial consistency and bias. We note that the forecast danger level agreed significantly less often when compared across national and forecast center boundaries (about 60 %) than within forecast center boundaries (about 90 %). Furthermore, several forecast centers showed significant systematic differences in terms of more frequently using lower (or higher) danger levels than their neighbors. Discrepancies seemed to be greatest when analyzing the proportion of forecasts with danger level 4 – high and 5 – very high. The size of the warning regions, the smallest geographically clearly specified areas underlying the forecast products, differed considerably between forecast centers. Region size also had a significant impact on all summary statistics and is a key parameter influencing the issued danger level, but it also limits the communication of spatial variations in the danger level. Operational constraints in the production and communication of avalanche forecasts and variation in the ways the EADS is interpreted locally may contribute to inconsistencies and may be potential sources for misinterpretation by forecast users. All these issues highlight the need to further harmonize the forecast production process and the way avalanche hazard is communicated to increase consistency and hence facilitate cross-border forecast interpretation by traveling users.

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Impacts of Climate Change on Snow Avalanche Activity Along a Transportation Corridor in the Tianshan Mountains

Hao

Zhang

Cui

et al. 2023

Int J Disaster Risk Sci

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Snow avalanches can repeatedly occur along the same track under different snowpack and meteorological conditions during the snow season in areas of snow avalanche activity. The snowfall, air temperature, and snow cover can change dramatically in a warming climate, causing significant changes in the snow avalanche risk. But how the risk of snow avalanche activity during the snow season will change under a warming climate remains an open question. Based on the observed meteorological and snowpack data from 1968 to 2021 and the snow avalanche activity data during the 2011–2021 snow seasons along a transportation corridor in the central Tianshan Mountains that has a typical continental snow climate, we analyzed the temporal distribution of the snow avalanche activity and the impacts of climate change on it. The results indicate that the frequency of the snow avalanche activity is characterized by a Gaussian bimodal distribution, resulting from interactions between the snowfall, air temperature, and snowpack evolution. In addition, the active period of wet snow avalanches triggered by temperature surges and high solar radiation has gradually moved forward from the second half to the first half of March with climate warming. The frequency and size of snowfall-triggered snow avalanches showed only a slight and insignificant increase. These findings are important for rationally arranging snow avalanche relief resources to improve the risk management of snow avalanche disasters, and highlight the necessity to immediately design risk mitigation strategies and disaster risk policies to improve our adaptation to climate change.

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On using local avalanche danger level estimates for regional forecast verification

Cited by 34 publications

References 13 publications

On the relation between avalanche occurrence and avalanche danger level

On the relation between avalanche occurrence and avalanche danger level

Spatial consistency and bias in avalanche forecasts – a case study in the European Alps

Impacts of Climate Change on Snow Avalanche Activity Along a Transportation Corridor in the Tianshan Mountains

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