Debris flows in the eastern Italian Alps: seasonality and atmospheric circulation patterns

Abstract

Abstract. The work examines the seasonality and large-scale atmospheric circulation patterns associated with debris-flow occurrence in the Trentino-Alto Adige region (eastern Italian Alps). Analysis is based on classification algorithms applied to a uniquely dense archive of debris flows and hourly rain gauge precipitation series covering the period 2000-2009. Results highlight the seasonal and synoptic forcing patterns linked to debris flows in the study area. Summer and fall season account for 92 % of the debris flows in the record, while atmospheric circulation characterized by zonal west, mixed and meridional south and southeast (SE-S) patterns account for 80 %. Both seasonal and circulation patterns exhibit geographical preference. In the case of seasonality, there is a strong north-south separation of summer-fall dominance, while spatial distribution of dominant circulation patterns exhibits clustering, with both zonal west and mixed patterns prevailing in the northwest and central east part of the region, while the southern part relates to meridional south and southeast pattern. Seasonal and synoptic pattern dependence is pronounced also on the debris-flow-triggering rainfall properties. Examination of rainfall intensity-duration thresholds derived for different data classes (according to season and synoptic pattern) revealed a distinct variability in estimated thresholds. These findings imply a certain control on debrisflow events and can therefore be used to improve existing alert systems.

Rain Microstructure Parameters Vary with Large-Scale Weather Conditions in Lausanne, Switzerland

“…The relationship between large-scale weather types and local weather phenomena has been verified previously, e.g., some weather types have a major influence on the generation of extremely hot days [41]. Moreover, GWLs influence stream flows [42], floods [43,44], forest fires [45], and even debris-flow events [46]. More directly, GWLs have a substantial influence on precipitation totals, particularly on their extreme values [47][48][49] and even seasonal extremes [50].…”

Landslides and synoptic weather trends in the European Alps

“…The use of broader scale atmospheric conditions can alleviate this problem although, to date, few studies have addressed this issue (e.g. Nikolopoulos et al 2015).…”

Meteorological Patterns Linked to Landslide Triggering in Asturias (NW Spain): A Preliminary Analysis

“…However, some authors [14,15] have highlighted the convenience of considering broader scale atmospheric conditions to improve the performance and reliability of the early warning systems, given that the atmospheric circulation is closely related to key factors that control the landslide triggering, such as the rainfall intensity and the frequency and duration of the precipitation events. The characterization of meteorological synoptic triggering conditions has been addressed through several studies, including those developed in British Columbia (Canada) [16], in Serra do Mar (Brazil) [17], in Italy [18], in the European Alps [19] and in Portugal [20].…”