Abstract
AbstractThe relationship between River Ammer flood frequency variability, extreme summer climate over Europe, and solar forcing is investigated. First, we used observational data to evaluate extreme weather and climate anomaly patterns associated with flood and solar forcing as well as the possible dynamical mechanisms behind them. Then, the annual resolution flood layer record from the Lake Ammer sediments is analysed to evaluate millennial‐scale variability of floods and possible related extreme climate patterns back to 5,500 years BP. A composite analysis reveals that observed River Ammer flood frequency variability at interannual to multidecadal time scales is connected to large‐scale extreme precipitation and temperature patterns. From a synoptic‐scale perspective, the extreme precipitation pattern associated with floods is related to an increase in the frequency of high upper‐level potential vorticity (PV) events over western Europe and a decrease over eastern Europe and western Russia. Increased (decreased) frequency of upper‐level high PV events is related to more (less) surface extreme precipitation occurrence. Furthermore, we show that increased frequency of upper‐level high PV events over western Europe is associated with enhanced blocking activity over eastern Europe. Therefore, the out of phase interannual to millennial‐scale variations of River Ammer flood frequency and solar irradiance, as presented in previous studies, can be explained by a solar modulation of eastern European‐western Russia summer blocking and associated upstream upper‐level wave breaking activity. In addition, we identify two distinct quasi‐periodic signals in both frequency of Lake Ammer flood layer and solar irradiance records with periods of ~900 years and ~2,300 years. We argue that similar cycles should dominate millennial‐scale variations of blocking activity in eastern Europe‐western Russia as well as extreme precipitation and flood frequency variability over central and western Europe during the last ~5,500 years.
Highlights
Over the past decades, Europe has experienced heavy floods with major socioeconomic consequences
To understand how floods are related to extreme temperature and precipitation (Figure 2) we look first at atmospheric circulation patterns associated with daily River Ammer floods, that is, daily discharge higher than 125 m3/s
We investigated the observed and proxy River Ammer flood variability and its relationship to solar irradiance forcing during summer
Summary
Europe has experienced heavy floods with major socioeconomic consequences. The R20mm index describes the number of days in summer with total daily precipitation higher than 20 mm (e.g., Zhang et al, 2011) It is analysed in connection with observed River Ammer flood variability. Open solar flux data at annual resolution are available at the KNMI webpage (www.knmi.nl) Based on this record, we construct the blocking frequency as well as upper PV patterns associated with low solar activity during the observational period. The second is the Holocene total solar irradiance (TSI) reconstruction of Steinhilber et al (2009), which is used to analyse the relationship between millennial-scale TSI variability and frequency of flood layer in the Lake Ammer sediments during the last ~5,500 years (Czymzik et al, 2016). Singular spectrum analysis (SSA) (e.g., Ghil et al, 2002) was applied to search for quasiperiodic signals in the TSI and flood layer records
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
