Causes of increased flood frequency in central Europe in the 19th century

Brönnimann, Stefan; Frigerio, Luca; Schwander, Mikhaël; Rohrer, Mario; Stucki, Peter; Franke, Jörg

doi:10.5194/cp-15-1395-2019

Cited by 14 publications

(9 citation statements)

References 37 publications

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“…We calculate it separately for the warm season (May to October, for Basel) and cold season (November to April, Beaucaire) in order analyse the seasonally-varying relation of weather types with temperature anomalies. The calculation of the FPI is based on Quinn and Wilby (2013) and is performed exactly as in Brönnimann et al (2019). We first determined the 98 th percentile of daily streamflow within the respective seasonal window and marked all days above this percentile as extreme events.…”

Section: Flood Probability Indexmentioning

confidence: 99%

“…This was repeated for different lead times up to 5 days such that the weather on preceding days is also considered. Lead times 5 to 0 were weighted as in Brönnimann et al (2019): 1/16, 1/8, 3/16, 1/4, 1/4, and 1/8. This yields an FPI for each day in the past (note that the index was calibrated in the data after 1900, but calculated back to 1763).…”

Section: Flood Probability Indexmentioning

confidence: 99%

“…The causes of this multidecadal flood variability are not well understood. Atmospheric circulation changes played a role (Jacobeit et al, 2003;Mudelsee et al, 2004;Quinn and Wilby, 2013;Brönnimann et al, 2019), but this has not been well quantified. Furthermore, the relation to climate change is unclear.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Warming and Atmospheric Circulation Changes on Multidecadal European Flood Variability

Brönnimann

Stucki

Franke

et al. 2021

Preprint

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Abstract. European flood frequency and intensity change on a multidecadal scale. Floods were more frequent in the 19th (Central Europe) and early 20th century (Western Europe) than during the mid-20th century and again more frequent since the 1970s. The causes of this variability are not well understood and the relation to climate change is unclear. Palaeoclimate studies from the northern Alps suggest that past flood-rich periods coincided with cold periods. In contrast, some studies suggest that more floods might occur in a future, warming world. Here we reconcile the apparent contradiction by addressing and quantifying the contribution of atmospheric processes to multidecadal flood variability. For this, we use long series of annual peak streamflow, daily weather data, reanalyses, and reconstructions. We show that both changes in atmospheric circulation and moisture content affected multidecadal changes of annual peak streamflow in Central and Western Europe over the past two centuries. We find that during the 19th and early 20th century, atmospheric circulation changes led to high peak values of moisture flux convergence. The circulation was more conducive to strong and long-lasting precipitation events than in the mid-20th century. These changes are also partly reflected in the seasonal mean circulation and reproduced in atmospheric model simulations, pointing to a possible role of oceanic variability. For the period after 1980, increasing moisture content in a warming atmosphere led to extremely high moisture flux convergence. Thus, the main atmospheric driver of flood variability changed from atmospheric circulation variability to water vapour increase.

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Section: Flood Probability Indexmentioning

confidence: 99%

Section: Flood Probability Indexmentioning

confidence: 99%

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Influence of Warming and Atmospheric Circulation Changes on Multidecadal European Flood Variability

Brönnimann

Stucki

Franke

et al. 2021

Preprint

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“…Over the long run, increasing flood frequency in the European Alps during Holocene cold periods may be linked to a southward shift of the Hadley cell and a weakening of the Açores high allowing a southward shift of the Westerlies and meandering circulations (Glur et al, 2013;Wirth et al, 2013). More recently, the flood-rich period in Central Europe in the 19th century appears to be associated with a more zonal and southward-shifted circulation (Brönnimann et al, 2019). In the period 1948-2007, the seesaw between increasing precipitation frequency in Northern Europe and a decreasing precipitation frequency in Southern Europe in winter is well controlled by changes in atmospheric circulation (Vautard and Yiou, 2009).…”

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confidence: 99%

Past Evolution and Recent Changes in Western Europe Large-scale Circulation

Blanc

Blanchet

Creutin

2021

Preprint

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Abstract. Detecting trends in regional large-scale circulation (LSC) is an important challenge as LSC is a key driver of local weather conditions. In this work, we investigate the past evolution of Western Europe LSC based on the 500 hPa geopotential height fields from 20CRv2c (1851–2010), ERA20C (1900–2010) and ERA5 (1950–2010) reanalyses. We focus on the evolution of large-scale circulation characteristics using three atmospheric descriptors that are based on analogy – characterizing the geopotential shape stationarity and how well a geopotential shape is reproduced in the climatology – together with a non-analogy descriptor accounting for the intensity of the centers of action. These descriptors were shown relevant to study precipitation extremes and variability in the Northwestern Alps in previous studies. Even though LSC characteristics and trends are consistent among the three reanalyses after 1950, we find major differences between 20CRv2c and ERA20C from 1900 to 1950 in accordance with previous studies. Notably, ERA20C produces flatter geopotential shapes in the beginning of the 20th century and shows a reinforcement of the meridional pressure gradient that is not observed in 20CRv2c. We then focus on the recent changes in LSC from 1950 to 2019 using ERA5. We combine the four atmospheric descriptors with an existing weather pattern classification to study the recent changes in the main atmospheric influences over France and Western Europe (Atlantic, Mediterranean, Northeast, Anticyclonic). We show that little changes are found in Northeast circulations. However, we show that Atlantic circulations (zonal flows) tend to become more similar to known Atlantic circulations in winter. Anticyclonic conditions tend to become more stationary in summer – a change that can potentially affect summer heatwaves. Furthermore, Mediterranean circulations tend to become more stationary, more similar to known Mediterranean circulations and associated with stronger centers of action in autumn, which could have implications for autumn extreme precipitation in the Mediterranean-influenced regions of the Southwestern Alps.

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“…The reconstruction from 1864 onward is available from: https://doi.org/10.1594/PANGAEA.907579 (Pfister, 2019). The weather types are available from: https://doi.org/10.5194/cp-15-1395-2019 (Brönnimann et al, 2019c). The historical instrumental data are available from: https://doi.org/10.1594/PANGAEA.909141 .…”

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confidence: 99%

Synthetic weather diaries: concept and application to Swiss weather in 1816

Brönnimann

2020

Clim. Past

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Abstract. Climate science is about to produce numerical daily weather reconstructions based on meteorological measurements for central Europe 250 years back. Using a pilot reconstruction covering Switzerland at a 2×2 km2 resolution for 1816, this paper presents methods to translate numerical reconstructions and derived indices into text describing daily weather and the state of vegetation. This facilitates comparison with historical sources and analyses of the effects of weather on different aspects of life. The translation, termed “synthetic weather diary”, could possibly be used to train machine learning approaches to do the reverse: reconstruct past weather from categorised text entries in diaries.

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Causes of increased flood frequency in central Europe in the 19th century

Cited by 14 publications

References 37 publications

Influence of Warming and Atmospheric Circulation Changes on Multidecadal European Flood Variability

Influence of Warming and Atmospheric Circulation Changes on Multidecadal European Flood Variability

Past Evolution and Recent Changes in Western Europe Large-scale Circulation

Synthetic weather diaries: concept and application to Swiss weather in 1816

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