scholarly journals Rivers in the sky, flooding on the ground: the role of atmospheric rivers in inland flooding in central Europe

2020 ◽  
Vol 24 (11) ◽  
pp. 5125-5147
Author(s):  
Monica Ionita ◽  
Viorica Nagavciuc ◽  
Bin Guan
Keyword(s):  
North Atlantic ◽  
Heavy Rainfall ◽  
Large Scale ◽  
Pressure Center ◽  
Atmospheric Rivers ◽  
Extreme Flooding ◽  
Large Scale Atmospheric Circulation ◽  
Rhine Catchment ◽  
Lower Rhine

Abstract. The role of large-scale atmospheric circulation and atmospheric rivers (ARs) in producing extreme flooding and heavy rainfall events in the lower part of the Rhine catchment area is examined in this study. Analysis of the largest 10 floods in the lower Rhine, between 1817 and 2015, shows that all these extreme flood peaks have been preceded up to 7 d in advance by intense moisture transport from the tropical North Atlantic basin in the form of narrow bands also known as atmospheric rivers. Most of the ARs associated with these flood events are embedded in the trailing fronts of the extratropical cyclones. The typical large-scale atmospheric circulation leading to heavy rainfall and flooding in the lower Rhine is characterized by a low pressure center south of Greenland, which migrates toward Europe, and a stable high pressure center over the northern part of Africa and the southern part of Europe and projects on the positive phase of the North Atlantic Oscillation. On the days preceding the flood peaks, lower (upper) level convergence (divergence) is observed over the analyzed region, which indicates strong vertical motions and heavy rainfall. Vertically integrated water vapor transport (IVT) exceeds 600 kg m−1 s−1 for the largest floods, marking these as very strong ARs. The results presented in this study offer new insights regarding the importance of moisture transport as a driver of extreme flooding in the lower part of the Rhine catchment area, and we show, for the first time, that ARs are a useful tool for the identification of potentially damaging floods in inland Europe.

scholarly journals Rivers in the sky, flooding on the ground

2020 ◽  
Author(s):  
Monica Ionita ◽  
Viorica Nagavciuc ◽  
Bin Guan
Keyword(s):  
Atmospheric Circulation ◽  
Heavy Rainfall ◽  
Large Scale ◽  
Rhine River ◽  
Flood Events ◽  
Pressure Center ◽  
Atmospheric Rivers ◽  
Extreme Flooding ◽  
Large Scale Atmospheric Circulation ◽  
Lower Rhine

Abstract. The role of the large scale atmospheric circulation and atmospheric rivers (ARs) in producing extreme flooding and heavy rainfall events in the lower part of Rhine River catchment area is examined in this study. Analysis of the largest 10 floods in the lower Rhine, between 1817–2015, indicate that all these extreme flood peaks have been preceded up to 7 days in advance by intense moisture transport from the tropical North Atlantic basin, in the form of narrow bands, also know as atmospheric rivers. The influence of ARs on the Rhine River flood events is done via the prevailing large-scale atmospheric circulation. Most of the ARs associated with these flood events are embedded in the trailing fronts of the extratropical cyclones. The typical large scale atmospheric circulation leading to heavy rainfall and flooding in the lower Rhine is characterized by a low pressure center south of Greenland which migrates towards Europe and a stable high pressure center over the northern part of Africa and southern part of Europe. The days preceding the flood peaks, lower (upper) level convergence (divergence) is observed over the analyzed region, which is an indication of strong vertical motions and heavy rainfall. The results presented in this study offer new insights regarding the importance of tropical moisture transport as driver of extreme flooding in the lower part of Rhine River catchment area and we show for the first time that ARs are an useful tool for the identification of potential damaging floods inland Europe.

scholarly journals Extreme Floods in the Eastern Part of Europe: Large-Scale Drivers and Associated Impacts

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1122
Author(s):  
Monica Ionita ◽  
Viorica Nagavciuc
Keyword(s):  
Water Vapor ◽  
Heavy Rainfall ◽  
Large Scale ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Flood Events ◽  
Rainfall Events ◽  
Catchment Areas ◽  
Large Scale Atmospheric Circulation ◽  
Heavy Rainfall Events

The role of the large-scale atmospheric circulation in producing heavy rainfall events and floods in the eastern part of Europe, with a special focus on the Siret and Prut catchment areas (Romania), is analyzed in this study. Moreover, a detailed analysis of the socio-economic impacts of the most extreme flood events (e.g., July 2008, June–July 2010, and June 2020) is given. Analysis of the largest flood events indicates that the flood peaks have been preceded up to 6 days in advance by intrusions of high Potential Vorticity (PV) anomalies toward the southeastern part of Europe, persistent cut-off lows over the analyzed region, and increased water vapor transport over the catchment areas of Siret and Prut Rivers. The vertically integrated water vapor transport prior to the flood peak exceeds 300 kg m−1 s−1, leading to heavy rainfall events. We also show that the implementation of the Flood Management Plan in Romania had positive results during the 2020 flood event compared with the other flood events, when the authorities took several precaution measurements that mitigated in a better way the socio-economic impact and risks of the flood event. The results presented in this study offer new insights regarding the importance of large-scale atmospheric circulation and water vapor transport as drivers of extreme flooding in the eastern part of Europe and could lead to a better flood forecast and flood risk management.

scholarly journals The 2010/2011 snow season in California's Sierra Nevada: Role of atmospheric rivers and modes of large-scale variability

2013 ◽  
Vol 49 (10) ◽  
pp. 6731-6743 ◽  
Author(s):  
Bin Guan ◽  
Noah P. Molotch ◽  
Duane E. Waliser ◽  
Eric J. Fetzer ◽  
Paul J. Neiman
Keyword(s):  
Sierra Nevada ◽  
Large Scale ◽  
Atmospheric Rivers ◽  
Snow Season

scholarly journals Potential Large-Scale Forcing Mechanisms Driving Enhanced North Atlantic Tropical Cyclone Activity since the Mid-1990s

2018 ◽  
Vol 31 (4) ◽  
pp. 1377-1397 ◽  
Author(s):  
Haikun Zhao ◽  
Xingyi Duan ◽  
G. B. Raga ◽  
Fengpeng Sun
Keyword(s):  
Tropical Cyclone ◽  
North Atlantic ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Low Level ◽  
The North ◽  
Recent Increase ◽  
Forcing Mechanisms ◽  
Interdecadal Changes

A significant increase of tropical cyclone (TC) frequency is observed over the North Atlantic (NATL) basin during the recent decades (1995–2014). In this study, the changes in large-scale controls of the NATL TC activity are compared between two periods, one before and one since 1995, when a regime change is observed. The results herein suggest that the significantly enhanced NATL TC frequency is related mainly to the combined effect of changes in the magnitudes of large-scale atmospheric and oceanic factors and their association with TC frequency. Interdecadal changes in the role of vertical wind shear and local sea surface temperatures (SSTs) over the NATL appear to be two important contributors to the recent increase of NATL TC frequency. Low-level vorticity plays a relatively weak role in the recent increase of TC frequency. These changes in the role of large-scale factors largely depend on interdecadal changes of tropical SST anomalies (SSTAs). Enhanced low-level westerlies to the east of the positive SSTAs have been observed over the tropical Atlantic since 1995, with a pattern nearly opposite to that seen before 1995. Moreover, the large-scale contributors to the NATL TC frequency increase since 1995 are likely related to both local and remote SSTAs. Quantification of the impacts of local and remote SSTAs on the increase of TC frequency over the NATL basin and the physical mechanisms require numerical simulations and further observational analyses.

scholarly journals Quantitative reconstruction of sea-surface conditions over the last ~150 yr in the Beaufort Sea based on dinoflagellate cyst assemblages: the role of large-scale atmospheric circulation patterns

2012 ◽  
Vol 9 (6) ◽  
pp. 7257-7289 ◽  
Author(s):  
L. Durantou ◽  
A. Rochon ◽  
D. Ledu ◽  
G. Massé
Keyword(s):  
Surface Waters ◽  
Large Scale ◽  
Beaufort Sea ◽  
Sea Surface ◽  
The Arctic ◽  
Surface Conditions ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Large Scale Atmospheric Circulation

Abstract. Dinoflagellate cyst (dinocyst) assemblages have been widely used over the Arctic Ocean to reconstruct sea-surface parameters on a quantitative basis. Such reconstructions provide insights into the role of anthropogenic vs natural forcings in the actual climatic trend. Here, we present the palynological analysis of a 36 cm-long core collected from the Mackenzie Through in the Canadian Beaufort Sea. Dinocyst assemblages were used to quantitatively reconstruct the evolution of sea surface conditions (temperature, salinity, sea ice) and freshwater palynomorphs influxes were used as local paleo-river discharge indicators over the last ~150 yr. Dinocyst assemblages are dominated by autotrophic taxa (68 to 96 %). Pentapharsodinium dalei is the dominant specie throughout most of the core, except at the top where the assemblages are dominated by Operculodinium centrocarpum. Quantitative reconstructions of sea surface parameters display a serie of relatively warm, lower sea ice and saline episodes in surface waters, alternately with relatively cool and low salinity episodes. The warm episodes are characterized with high dinocyst productivity. Variations of dinocyst influxes and reconstructed sea surface conditions are closely linked to large scale atmospheric circulation patterns such as the Pacific Decadal Oscillation (PDO) and to a lesser degree, the Arctic Oscillation (AO). Positive phases of the PDO correspond to increases of dinocyst influxes, warmer and saltier surface waters, which we associate with upwelling events of warm and relatively saline water from Pacific origin. Freshwater palynomorph influxes increased in three phases from AD 1857 until reaching maximum values in AD 1991, suggesting that the Mackenzie River discharge followed the same trend when its discharge peaked between AD 1989 and AD 1992. The PDO mode seems to dominate the climatic variations at multi-annual to decadal timescales in the Western Canadian Arctic and Beaufort Sea areas.

scholarly journals Moisture Origin and Meridional Transport in Atmospheric Rivers and Their Association with Multiple Cyclones*

2013 ◽  
Vol 141 (8) ◽  
pp. 2850-2868 ◽  
Author(s):  
Harald Sodemann ◽  
Andreas Stohl
Keyword(s):  
Water Vapor ◽  
North Atlantic ◽  
Large Scale ◽  
Mesoscale Model ◽  
Storm Track ◽  
Conveyor Belt ◽  
Tracer Transport ◽  
Atmospheric Rivers ◽  
The North ◽  
The North Atlantic

Abstract During December 2006 many cyclones traveled across the North Atlantic, causing temperature and precipitation in Norway to be well above average. Large excursions of high vertically integrated water vapor, often referred to as atmospheric rivers, reached from the subtropics to high latitudes, inducing precipitation over western Scandinavia. The sources and transport of atmospheric water vapor in the North Atlantic storm track during that month are examined by means of a mesoscale model fitted with water vapor tracers. Decomposition of the modeled total water vapor field into numerical water vapor tracers tagged by evaporation latitude shows that when an atmospheric river was present, a higher fraction of water vapor from remote, southerly source regions caused more intense precipitation. The tracer transport analysis revealed that the atmospheric rivers were composed of a sequence of meridional excursions of water vapor, in close correspondence with the upper-level flow configuration. In cyclone cores, fast turnover of water vapor by evaporation and condensation were identified, leading to a rapid assimilation of water from the underlying ocean surface. In the regions of long-range transport, water vapor tracers from the southern midlatitudes and subtropics dominated over local contributions. By advection of water vapor along their trailing cold fronts cyclones were reinforcing the atmospheric rivers. At the same time the warm conveyor belt circulation was feeding off the atmospheric rivers by large-scale ascent and precipitation. Pronounced atmospheric rivers could persist in the domain throughout more than one cyclone's life cycle. These findings emphasize the interrelation between midlatitude cyclones and atmospheric rivers but also their distinction from the warm conveyor belt airstream.

scholarly journals Past long-term summer warming over western Europe in new generation climate models: role of large-scale atmospheric circulation

2020 ◽  
Vol 15 (8) ◽  
pp. 084038
Author(s):  
Julien Boé ◽  
Laurent Terray ◽  
Marie-Pierre Moine ◽  
Sophie Valcke ◽  
Alessio Bellucci ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Western Europe ◽  
Climate Models ◽  
Summer Warming ◽  
New Generation ◽  
Large Scale Atmospheric Circulation

scholarly journals What drives flood trends along the Rhine River: climate or river training?

2012 ◽  
Vol 9 (12) ◽  
pp. 13537-13567 ◽  
Author(s):  
S. Vorogushyn ◽  
B. Merz
Keyword(s):  
Large Scale ◽  
Rhine River ◽  
Annual Maximum ◽  
The Past ◽  
Time Period ◽  
River Training ◽  
Detention Basins ◽  
Annual Maximum Series ◽  
Lower Rhine

Abstract. The Rhine River catchment was heavily trained over the past decades and faced the construction of the Rhine weir cascade, flood protection dikes and detention basins. For the same time period, several studies detected positive trends in flood flows and faced the challenge of flood trend attribution, i.e. identifying the drivers of observed change. The presented study addresses the question about the responsible drivers for changes in annual maximum daily flows at Rhine gauges starting from Maxau down to Lobith. In particular, the role of river training measures including the Rhine weir cascade and a series of detention basins in enhancing Rhine floods was investigated. By applying homogenisation relationships to the original flow records in the period from 1952 till 2009, the annual maximum series were computed that would have been recorded had river training measures not been in place. Using multiple trend analysis, the relative changes in the homogenised time series were found to be smaller up to about 20% points compared to the original records. This effect is attributable to the river training measures and primarily to the construction of the Rhine weir cascade. The increase in Rhine flood discharges was partly caused by the unfavourable superposition of the Rhine and Neckar flood waves. It resulted from the acceleration of the Rhine waves due to construction of the weir cascade. However, at the same time, the tributary flows across the entire Upper and Lower Rhine, which enhance annual Rhine peaks, showed very strong positive trends. This suggests the dominance of a large-scale driver such as climate variability/change which acted along with river training. In particular, the analysis suggests that the river training measures fell in a period with increasing flood trends driven by factors other than river training of the Rhine main channel.

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