scholarly journals Atmospheric circulation patterns associated with the variability of River Ammer floods: evidence from observed and proxy data

2016 ◽  
Vol 12 (2) ◽  
pp. 377-385 ◽  
Author(s):  
Norel Rimbu ◽  
Markus Czymzik ◽  
Monica Ionita ◽  
Gerrit Lohmann ◽  
Achim Brauer
Keyword(s):  
Time Series ◽  
Atmospheric Circulation ◽  
Western Europe ◽  
Wave Train ◽  
Heavy Precipitation ◽  
Circulation Pattern ◽  
Flood Frequency ◽  
Discharge Data ◽  
Western Asia ◽  
Instrumental Period

Abstract. The relationship between the frequency of River Ammer floods (southern Germany) and atmospheric circulation variability is investigated based on observational Ammer River discharge data back to 1926 and a flood layer time series from varved sediments of the downstream Lake Ammer for the pre-instrumental period back to 1766. A composite analysis reveals that, at synoptic timescales, observed River Ammer floods are associated with enhanced moisture transport from the Atlantic Ocean and the Mediterranean towards the Ammer region, a pronounced trough over western Europe as well as enhanced potential vorticity at upper levels. We argue that this synoptic-scale configuration can trigger heavy precipitation and floods in the Ammer region. Interannual to multidecadal increases in flood frequency, as detected in the instrumental discharge record, are associated with a wave train pattern extending from the North Atlantic to western Asia, with a prominent negative center over western Europe. A similar atmospheric circulation pattern is associated with increases in flood layer frequency in the Lake Ammer sediment record during the pre-instrumental period. We argue that the complete flood layer time series from Lake Ammer sediments covering the last 5500 years contains information about atmospheric circulation variability on interannual to millennial timescales.

scholarly journals Atmospheric circulation patterns associated to the variability of River Ammer floods: evidence from observed and proxy data

2015 ◽  
Vol 11 (5) ◽  
pp. 4483-4504 ◽  
Author(s):  
N. Rimbu ◽  
M. Czymzik ◽  
M. Ionita ◽  
G. Lohmann ◽  
A. Brauer
Keyword(s):  
Time Series ◽  
Atmospheric Circulation ◽  
Time Scales ◽  
Western Europe ◽  
Wave Train ◽  
Circulation Pattern ◽  
Flood Frequency ◽  
Discharge Data ◽  
Western Asia ◽  
Instrumental Period

Abstract. The relationship between the frequency of River Ammer floods (southern Germany) and atmospheric circulation variability is investigated based on observational Ammer discharge data back to 1926 and a flood layer time series from varved sediments of the downstream Lake Ammersee for the pre-instrumental period back to 1766. A composite analysis reveals that, at synoptic time scales, observed River Ammer floods are associated with enhanced moisture transport from the Atlantic Ocean and the Mediterranean towards the Ammer region, a pronounced trough over Western Europe as well as enhanced potential vorticity at upper levels. We argue that this synoptic scale configuration can trigger heavy precipitation and floods in the Ammer region. Interannual to multidecadal increases in flood frequency as recorded in the instrumental discharge record are associated to a wave-train pattern extending from the North Atlantic to western Asia with a prominent negative center over western Europe. A similar atmospheric circulation pattern is associated to increases in flood layer frequency in the Lake Ammersee sediment record during the pre-instrumental period. We argue that the complete flood layer time-series from Lake Ammersee sediments covering the last 5500 years, contains information about atmospheric circulation variability on inter-annual to millennial time-scales.

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

2017 ◽  
Author(s):  
Norel Rimbu ◽  
Monica Ionita ◽  
Markus Czymzik ◽  
Achim Brauer ◽  
Gerrit Lohmann
Keyword(s):  
Solar Activity ◽  
Radiative Forcing ◽  
Large Scale ◽  
Western Europe ◽  
Extreme Temperature ◽  
Heavy Precipitation ◽  
Flood Frequency ◽  
Discharge Data ◽  
Blocking High ◽  
Northeastern Europe

Abstract. We 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 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 River 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 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 Europe.

scholarly journals The Analogue Method for Precipitation Forecasting: Finding Better Analogue Situations at a Sub-Daily Time Step

2016 ◽  
Author(s):  
Pascal Horton ◽  
Charles Obled ◽  
Michel Jaboyedoff
Keyword(s):  
Time Series ◽  
Atmospheric Circulation ◽  
Time Window ◽  
Heavy Precipitation ◽  
Seasonal Effect ◽  
Precipitation Series ◽  
Time Step ◽  
Analogue Method ◽  
The Impact ◽  
Daily Time

Abstract. The Analogue Method (AM) aims at forecasting local weather variables (predictands), such as precipitations, by means of a statistical relationship with predictors at a synoptic scale. The analogy is generally assessed in the first place on the geopotential field by mean of a comparison of the gradients, in order to sample the days with a similar atmospheric circulation. The search for candidate situations, for a given target day, is usually undertaken by comparing the state of the atmosphere at fixed hours of the day, for both the target day and the candidate analogues. The constraint being the use of daily time series, due to the length of available archives they provide, and the unavailability of equivalent archives at a finer time step. However, it is unlikely that the best analogy happens at the very same hour, but it may occur at a different time of the day. In order to assess the potential of finding better analogues at a different hour, a moving time window (MTW) has been introduced on a reduced archive of hourly precipitation totals. The MTW resulted in a better analogy in terms of the atmospheric circulation, with improved values of the analogy criteria on the whole distribution of analogue dates. The improvement was found to grow with the analogue ranks due to an accumulation of more similar situations in the selection. Moreover, the improvement is even more important for days with heavy precipitation events, which are generally related to more dynamic atmospheric situations, where timing is more specific. A seasonal effect has also been identified, with larger improvements in winter than in summer, supposedly due to the stronger effect of the diurnal cycle in summer, which favors predictors at the same hour for target and analogues. The impact of the MTW on the prediction performance has been assessed by means of a sub-daily precipitation series transformed into moving 24 h-totals at a 6-hourly time step. This resulted in an improvement of the prediction skills, which were even larger after recalibrating the AM parameters. However, attempts to reconstruct longer precipitation series of running 24 h-totals by means of simple methods failed. It emphasized the need to use time series with an appropriate chronology. These should be available in a near future, either by means of growing observed archives, or by the establishment of precipitation reanalyses through regional modeling. Then, the use of a MTW in the AM should be considered for any application, especially when the prediction quality of extreme events is important.

Improving Estimates of Heavy and Extreme Precipitation Using Daily Records from European Rain Gauges

2009 ◽  
Vol 10 (3) ◽  
pp. 701-716 ◽  
Author(s):  
Olga Zolina ◽  
Clemens Simmer ◽  
Konstantin Belyaev ◽  
Alice Kapala ◽  
Sergey Gulev
Keyword(s):  
Time Series ◽  
Extreme Precipitation ◽  
Western Europe ◽  
Daily Precipitation ◽  
Heavy Precipitation ◽  
Rain Gauge ◽  
European Russia ◽  
Correlation Pattern ◽  
Fractional Contribution ◽  
Linear Trends

Abstract The long-term variability in heavy precipitation characteristics over Europe for the period 1950–2000 is analyzed using high-quality daily records of rain gauge measurements from the European Climate Assessment (ECA) dataset. To improve the accuracy of heavy precipitation estimates, the authors suggest estimating the fractional contribution of very wet days to total precipitation from the probability distribution of daily precipitation than from the raw data, as it is adopted for the widely used R95tot precipitation index. This is feasible under the assumption that daily precipitation follows an analytical distribution like the gamma probability density function (PDF). The extended index R95tt based on the gamma PDF is compared to the classical R95tot index. The authors find that R95tt is more stable, especially when precipitation extremes are estimated from the limited number of wet days of seasonal and monthly time series. When annual daily time series are analyzed, linear trends in R95tt and R95tot are qualitatively consistent; both hint at a growing occurrence of extreme precipitation of up to 3% decade−1 in central western Europe and in south European Russia, with a somewhat more evident trend pattern for the R95tt index. Linear trends estimated for individual seasons, however, exhibit pronounced differences when derived from both indices. In particular, in winter, R95tt clearly reveals an increasing occurrence of extreme precipitation in western European Russia (up to 4% decade−1), while during summer, a downward tendency in the fractional contribution of very wet days is found in central western Europe. The new index also allows for a better association of European extreme precipitation with the North Atlantic Oscillation (NAO) index by showing a more consistent spatial correlation pattern and higher correlation levels compared to R95tot.

scholarly journals Solar modulation of flood frequency in central Europe during spring and summer on interannual to multi-centennial timescales

2016 ◽  
Vol 12 (3) ◽  
pp. 799-805 ◽  
Author(s):  
Markus Czymzik ◽  
Raimund Muscheler ◽  
Achim Brauer
Keyword(s):  
Solar Activity ◽  
Atmospheric Circulation ◽  
Central Europe ◽  
Empirical Support ◽  
Total Solar Irradiance ◽  
Flood Frequency ◽  
Solar Modulation ◽  
Top Down ◽  
Discharge Data ◽  
Atmospheric Circulation Patterns

Abstract. Solar influences on climate variability are one of the most controversially discussed topics in climate research. We analyze solar forcing of flood frequency in central Europe during spring and summer on interannual to multi-centennial timescales, integrating daily discharge data of the River Ammer (southern Germany) back to AD 1926 (∼  solar cycles 16–23) and the 5500-year flood layer record from varved sediments of the downstream Ammersee. Flood frequency in the River Ammer discharge record is significantly correlated to changes in solar activity when the flood record lags the solar signal by 2–3 years (2-year lag: r = −0.375, p = 0.01; 3-year lag: r = −0.371, p = 0.03). Flood layer frequency in the Ammersee sediment record depicts distinct multi-decadal variations and significant correlations to a total solar irradiance reconstruction (r = −0.4, p <  0.0001) and 14C production rates (r = 0.37, p <  0.0001), reflecting changes in solar activity. On all timescales, flood frequency is higher when solar activity is reduced. In addition, the configuration of atmospheric circulation associated with periods of increased River Ammer flood frequency broadly resembles that during intervals of reduced solar activity, as expected to be induced by the so-called solar top-down mechanism by model studies. Both atmospheric patterns are characterized by an increase in meridional airflow associated with enhanced atmospheric blocking over central Europe. Therefore, the significant correlations as well as similar atmospheric circulation patterns might provide empirical support for a solar influence on hydroclimate extremes in central Europe during spring and summer by the so-called solar top-down mechanism.

Cloudiness and weather variation in central Svalbard in July 2013 as related to atmospheric circulation

2013 ◽  
Vol 3 (2) ◽  
pp. 184-195 ◽  
Author(s):  
Kamil Láska ◽  
Zuzana Chládová ◽  
Klára Ambrožová ◽  
Jan Husák
Keyword(s):  
Wind Speed ◽  
Atmospheric Circulation ◽  
Air Temperature ◽  
Rapid Change ◽  
Weather Conditions ◽  
Heavy Precipitation ◽  
Circulation Pattern ◽  
Free Zone ◽  
Circulation Types ◽  
Weather Variation

The paper describes synoptic situations and associated weather conditions in the central part of the Svalbard Arctic archipelago (Petuniabukta, Billefjorden) during two weeks of the summer 2013. The circulation types in July 2013 were compared with the long-term average circulation pattern in the period 1961–2010. Cloudiness and weather conditions in different atmospheric circulation types were described. Atmospheric pressure, 2-m air temperature, precipitation, 6-m wind speed and wind direction data from an automatic weather station located on the coastal glacier-free zone of Petuniabukta were used for further analysis. From July 5 to 19, 2013, radiation and advection weather types, heavy precipitation, rapid change of wind speed, 2-m air temperature and high cloudiness variation were described in detail within of the five most frequent synoptic situations. Foehn and halo phenomena were also reported in the study period.

scholarly journals A dynamical adjustment perspective on extreme event attribution

2021 ◽  
Author(s):  
Laurent Terray
Keyword(s):  
Atmospheric Circulation ◽  
Extreme Events ◽  
Western Europe ◽  
Climate Model ◽  
Extreme Event ◽  
Dynamic Component ◽  
Western Asia ◽  
Event Attribution ◽  
Climate Model Simulations

Abstract. Here we demonstrate that dynamical adjustment allows a straightforward approach to extreme event attribution within a conditional framework. We illustrate the potential of the approach with two iconic extreme events that occurred in 2010: the early winter European cold spell and the Russian summer heat wave. We use a dynamical adjustment approach based on constructed atmospheric circulation analogues to isolate the various contributions to these two extreme events using only observational and reanalysis datasets. Dynamical adjustment results confirm previous findings regarding the role of atmospheric circulation in the two extreme events and provide a quantitative estimate of the various dynamic and thermodynamic contributions to the event amplitude. Furthermore, the approach is also used to identify the drivers of the recent 1979–2018 trends in summer extreme maximum and minimum temperature changes over western Europe and western Asia. The results suggest a significant role of the dynamic component in explaining temperature extreme changes in different regions, including regions around the Black and Caspian Seas as well as central Europe and the coasts of western Europe. Finally, dynamical adjustment offers a simple and complementary storyline approach to extreme event attribution with the advantage that no climate model simulations are needed, making it a promising candidate for the fast-track component of any real-time extreme event attribution system.

LamaH: Large-sample Data for Hydrology in Central Europe

2021 ◽  
Author(s):  
Christoph Klingler ◽  
Mathew Herrnegger ◽  
Frederik Kratzert ◽  
Karsten Schulz
Keyword(s):  
Time Series ◽  
Time Series Data ◽  
Vegetation Indices ◽  
River Network ◽  
Series Data ◽  
High Temporal Resolution ◽  
Stream Length ◽  
Discharge Data ◽  
Large Sample ◽  
Access To Data

&lt;p&gt;Open large-sample datasets are important for various reasons: i) they enable large-sample analyses, ii) they democratize access to data, iii) they enable large-sample comparative studies and foster reproducibility, and iv) they are a key driver for recent developments of machine-learning based modelling approaches.&lt;/p&gt;&lt;p&gt;Recently, various large-sample datasets have been released (e.g. different country-specific CAMELS datasets), however, all of them contain only data of individual catchments distributed across entire countries and not connected river networks.&lt;/p&gt;&lt;p&gt;Here, we present LamaH, a new dataset covering all of Austria and the foreign upstream areas of the Danube, spanning a total of 170.000 km&amp;#178; in 9 different countries with discharge observations for 882 gauges. The dataset also includes 15 different meteorological time series, derived from ERA5-Land, for two different basin delineations: First, corresponding to the entire upstream area of a particular gauge, and second, corresponding only to the area between a particular gauge and its upstream gauges. The time series data for both, meteorological and discharge data, is included in hourly and daily resolution and covers a period of over 35 years (with some exceptions in discharge data for a couple of gauges).&lt;/p&gt;&lt;p&gt;Sticking closely to the CAMELS datasets, LamaH also contains more than 60 catchment attributes, derived for both types of basin delineations. The attributes include climatic, hydrological and vegetation indices, land cover information, as well as soil, geological and topographical properties. Additionally, the runoff gauges are classified by over 20 different attributes, including information about human impact and indicators for data quality and completeness. Lastly, LamaH also contains attributes for the river network itself, like gauge topology, stream length and the slope between two sequential gauges.&lt;/p&gt;&lt;p&gt;Given the scope of LamaH, we hope that this dataset will serve as a solid database for further investigations in various tasks of hydrology. The extent of data combined with the interconnected river network and the high temporal resolution of the time series might reveal deeper insights into water transfer and storage with appropriate methods of modelling.&lt;/p&gt;

scholarly journals Joint impact of rainfall and tidal level on flood risk in a coastal city with a complex river network: a case study of Fuzhou City, China

2013 ◽  
Vol 17 (2) ◽  
pp. 679-689 ◽  
Author(s):  
J. J. Lian ◽  
K. Xu ◽  
C. Ma
Keyword(s):  
Flood Risk ◽  
Joint Probability ◽  
Heavy Precipitation ◽  
River Network ◽  
Flood Frequency ◽  
Combined Effect ◽  
Multiple Sources ◽  
Tidal Level ◽  
Sea Levels ◽  
Coastal Cities

Abstract. Coastal cities are particularly vulnerable to flood under multivariable conditions, such as heavy precipitation, high sea levels, and storms. The combined effect of multiple sources and the joint probability of extremes should be considered to assess and manage flood risk better. This paper aims to study the combined effect of rainfall and the tidal level of the receiving water body on flood probability and severity in Fuzhou City, which has a complex river network. Flood severity under a range of precipitation intensities, with return periods (RPs) of 5 yr to 100 yr, and tidal levels was assessed through a hydrodynamic model verified by data observed during Typhoon Longwang in 2005. According to the percentages of the river network where flooding occurred, the threshold conditions for flood severity were estimated in two scenarios: with and without working pumps. In Fuzhou City, working pumps efficiently reduce flood risk from precipitation within a 20-yr RP. However, the pumps may not work efficiently when rainfall exceeds a 100-yr RP because of the limited conveyance capacity of the river network. Joint risk probability was estimated through the optimal copula. The joint probability of rainfall and tidal level both exceeding their threshold values is very low, and the greatest threat in Fuzhou comes from heavy rainfall. However, the tidal level poses an extra risk of flood. Given that this extra risk is ignored in the design of flood defense in Fuzhou, flood frequency and severity may be higher than understood during design.

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