Clustering of Regional-Scale Extreme Precipitation Events in Southern Switzerland

Barton, Yannick; Giannakaki, Paraskevi; Waldow, Harald von; Chevalier, Clément; Pfahl, Stephan; Martius, Olivia

doi:10.1175/mwr-d-15-0205.1

Cited by 108 publications

(175 citation statements)

References 62 publications

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“…Therefore, we investigate the relationship between River Ammer flood variability and blocking activity over Europe during summer. Consistent with the study by Barton et al (2016), positive blocking frequency anomalies are recorded in this region during summers with increased flood frequency (Fig. 6).…”

supporting

confidence: 91%

“…This is due to the fact that the majority of flood days occur during summer (Czymzik et al, 2010). The Z500 anomaly pattern ( and is consistent with synoptic scale patterns that leads to clustering of extreme precipitation events in Switzerland (Barton et al, 2016). The corresponding precipitation anomaly maps ( Fig.…”

supporting

confidence: 78%

“…An important forcing factor which favors extreme precipitation in the Alpine realm is atmospheric blocking over northeastern Europe (Barton et al, 2016). Therefore, we investigate the relationship between River Ammer flood variability and blocking activity over Europe during summer.…”

mentioning

confidence: 99%

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Patterns of extreme weather associated with observed and proxy River Ammer flood records

Rîmbu

Ionita

Czymzik

et al. 2017

Preprint

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2 AbstractWe investigate the relationship between the variability in the frequency of River Ammer floods (southern Germany) and temperature/precipitation extremes over Europe using observational River Ammer discharge data back to 1926 and the 5500-year-long flood layer record from 35 varved Lake Ammersee sediments. We show that observed River Ammer flood frequency variability is not only related with local extreme precipitation, but also with large-scale temperature extreme anomalies. Less (more) extreme high temperatures over central and western (northeastern) Europe are recorded during periods of increased River Ammer flood frequency.We argue that changing radiative forcing due to cloudiness anomaly patterns associated with 40River Ammer floods induce these extreme temperature anomalies. Consistent patterns are obtained using observed discharge and proxy flood layer frequency data. Furthermore, a higher frequency of observed River Ammer floods and flood layers is associated with enhanced blocking activity over northeastern Europe. A blocking high over this region increases the probability of wave breaking and associated heavy precipitation over western Europe. A similar 45 blocking pattern is associated with periods of reduced solar activity. Consequently, solar modulated changes in blocking frequency over northeastern Europe could explain the connection between River Ammer floods and solar activity, as also identified in previous studies. We argue that multi-decadal to millennial flood frequency variations in the Mid-to Late Holocene flood layer record from Lake Ammersee characterizes also the extreme temperatures in northeastern 50 Europe. 55Clim. Past Discuss., https://doi

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supporting

confidence: 91%

supporting

confidence: 78%

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Patterns of extreme weather associated with observed and proxy River Ammer flood records

Rîmbu

Ionita

Czymzik

et al. 2017

Preprint

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“…In order to guarantee the temporal independence of maxima of blocks as short as months, a minimum lag time of 48 h among maxima occurring in 2 successive months but close in time was imposed for accumulations ranging from 1 h to 1 day. In fact, Fukutome et al (2015) and Barton et al (2016) found that this is the maximum declustering run length in Switzerland for hourly and daily precipitation, respectively. For 2-day rainfall accumulations, such lag time was extended to 72 h. In case of maxima of 2 separate months occurring within this lag time, the largest was assigned to the corresponding month, while the smallest was substituted with the second maximum of the other month.…”

Section: Extreme Rainfall Analysismentioning

confidence: 93%

A radar-based regional extreme rainfall analysis to derive the thresholds for a novel automatic alert system in Switzerland

Panziera

Gabella

Zanini

et al. 2016

Hydrol. Earth Syst. Sci.

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Abstract. This paper presents a regional extreme rainfall analysis based on 10 years of radar data for the 159 regions adopted for official natural hazard warnings in Switzerland. Moreover, a nowcasting tool aimed at issuing heavy precipitation regional alerts is introduced. The two topics are closely related, since the extreme rainfall analysis provides the thresholds used by the nowcasting system for the alerts. Warm and cold seasons' monthly maxima of several statistical quantities describing regional rainfall are fitted to a generalized extreme value distribution in order to derive the precipitation amounts corresponding to sub-annual return periods for durations of 1, 3, 6, 12, 24 and 48 h. It is shown that regional return levels exhibit a large spatial variability in Switzerland, and that their spatial distribution strongly depends on the duration of the aggregation period: for accumulations of 3 h and shorter, the largest return levels are found over the northerly alpine slopes, whereas for longer durations the southern Alps exhibit the largest values. The inner alpine chain shows the lowest values, in agreement with previous rainfall climatologies.The nowcasting system presented here is aimed to issue heavy rainfall alerts for a large variety of end users, who are interested in different precipitation characteristics and regions, such as, for example, small urban areas, remote alpine catchments or administrative districts. The alerts are issued not only if the rainfall measured in the immediate past or forecast in the near future exceeds some predefined thresholds but also as soon as the sum of past and forecast precipitation is larger than threshold values. This precipitation total, in fact, has primary importance in applications for which antecedent rainfall is as important as predicted one, such as urban floods early warning systems. The rainfall fields, the statistical quantity representing regional rainfall and the frequency of alerts issued in case of continuous threshold exceedance are some of the configurable parameters of the tool.The analysis of the urban flood which occurred in the city of Schaffhausen in May 2013 suggests that this alert tool might have complementary skill with respect to radar-based thunderstorm nowcasting systems for storms which do not show a clear convective signature.

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“…For the floods of 2002 also in central Europe, Ulbrich et al (2003) describe several intense rainfall episodes in the first half of August that finally led to the extreme discharges. In southern Switzerland, severe flooding of the Lago Maggiore in September 1993 was preceded by a series of high precipitation events in the watershed (Barton et al, 2014). Antecedent conditions might even be relevant for the development of flash floods: Marchi et al (2010) found that the runoff coefficient, i.e., the fraction of the total rainfall that is routed into runoff, of 58 flash floods in Europe was statistically higher for wetter antecedent precipitation.…”

Section: P Froidevaux Et Al: Flood-triggering Precipitation In Switmentioning

confidence: 99%

Flood triggering in Switzerland: the role of daily to monthly preceding precipitation

Froidevaux

Schwanbeck

Weingartner

et al. 2015

Hydrol. Earth Syst. Sci.

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Abstract. Determining the role of different precipitation periods for peak discharge generation is crucial for both projecting future changes in flood probability and for short-and medium-range flood forecasting. In this study, catchmentaveraged daily precipitation time series are analyzed prior to annual peak discharge events (floods) in Switzerland. The high number of floods considered -more than 4000 events from 101 catchments have been analyzed -allows to derive significant information about the role of antecedent precipitation for peak discharge generation. Based on the analysis of precipitation times series, a new separation of flood-related precipitation periods is proposed: (i) the period 0 to 1 day before flood days, when the maximum flood-triggering precipitation rates are generally observed, (ii) the period 2 to 3 days before flood days, when longer-lasting synoptic situations generate "significantly higher than normal" precipitation amounts, and (iii) the period from 4 days to 1 month before flood days when previous wet episodes may have already preconditioned the catchment. The novelty of this study lies in the separation of antecedent precipitation into the precursor antecedent precipitation (4 days before floods or earlier, called PRE-AP) and the short range precipitation (0 to 3 days before floods, a period when precipitation is often driven by one persistent weather situation like e.g., a stationary low-pressure system). A precise separation of "antecedent" and "peak-triggering" precipitation is not attempted. Instead, the strict definition of antecedent precipitation periods permits a direct comparison of all catchments.The precipitation accumulating 0 to 3 days before an event is the most relevant for floods in Switzerland. PRE-AP precipitation has only a weak and region-specific influence on flood probability. Floods were significantly more frequent after wet PRE-AP periods only in the Jura Mountains, in the western and eastern Swiss plateau, and at the outlet of large lakes. As a general rule, wet PRE-AP periods enhance the flood probability in catchments with gentle topography, high infiltration rates, and large storage capacity (karstic cavities, deep soils, large reservoirs). In contrast, floods were significantly less frequent after wet PRE-AP periods in glacial catchments because of reduced melt.For the majority of catchments however, no significant correlation between precipitation amounts and flood occurrences is found when the last 3 days before floods are omitted in the precipitation amounts. Moreover, the PRE-AP was not higher for extreme floods than for annual floods with a high frequency and was very close to climatology for all floods. The fact that floods are not significantly more frequent nor more intense after wet PRE-AP is a clear indicator of a short discharge memory of Pre-Alpine, Alpine and South Alpine Swiss catchments. Our study poses the question whether the impact of long-term precursory precipitation for floods in such catchments is not overestimated in the general ...

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Clustering of Regional-Scale Extreme Precipitation Events in Southern Switzerland

Cited by 108 publications

References 62 publications

Patterns of extreme weather associated with observed and proxy River Ammer flood records

Patterns of extreme weather associated with observed and proxy River Ammer flood records

A radar-based regional extreme rainfall analysis to derive the thresholds for a novel automatic alert system in Switzerland

Flood triggering in Switzerland: the role of daily to monthly preceding precipitation

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