Änderung des Gewitter- und Hagelpotentials im Klimawandel

In der vorliegenden Arbeit wird untersucht, inwieweit sich die Häufigkeit und Intensität von Gewitter- und Hagelereignissen in den vergangenen Jahren in Deutschland und Europa verändert hat. Mit Hilfe von regionalen Klimasimulationen wird abgeschätzt, mit welchen Änderungen des Hagelpotentials - bedingt durch den anthropogenen Klimawandel - in der Zukunft zu rechnen ist

Statistical characteristics of convective wind gusts in Germany

Due to the small-scale and non-stationary nature of the convective wind gusts usually associated with thunderstorms, there is a considerable lack of knowledge regarding their characteristics and statistics. In an effort to remedy this situation, we investigated in this study a set of 110 climate stations of the German Weather Service between 1992 and 2014 to analyze the temporal and spatial distribution, intensity, and occurrence probability of convective gusts. Similar to thunderstorm activity, the frequency of convective gusts decreases gradually from southern to northern Germany. No further spatial structures, such as a relation to orography or climate conditions, can be identified regarding their strength or likelihood. Rather, high wind speeds of above 30 m s−1 can be expected everywhere in Germany with almost similar occurrence probabilities. A comparison of the 20-year return values of convective gusts with those of turbulent gusts demonstrates that the latter have higher frequencies, especially in northern Germany. However, for higher return periods, this effect can be reversed at some stations. The values of the convective gust factors are mainly in a range between 1 and 4 but can even reach values up to 10. Besides the dependency from the averaging time period of the mean wind, the values of the gust factors additionally depend on the event duration and the storm type, respectively

Investigation of the temporal variability of thunderstorms in Central and Western Europe and the relation to large‐scale flow and teleconnection patterns

The driving factors that influence the spatial and annual variability of thunderstorms across Europe are still poorly understood. Due to a lack of long‐term, reliable and consistent information about the occurrence of convective storms, a weather type classification has been developed that estimates thunderstorm probability from a combination of appropriate meteorological quantities on the mesoscale. Based on this approach, the temporal and spatial variability of convection‐favouring environments is investigated between 1958 and 2014 using a high‐resolution reanalysis dataset. To identify potential drivers for convective days, typical upper‐level flow patterns were deduced using a multivariate approach. Our results suggest a strong link between local‐scale thunderstorm activity and large‐scale flow and air mass properties, such as stability, moisture, or vertical lifting. For example, while all over central Europe the most prominent pattern is given by a southwesterly flow type over the respective area, distinct regional discrepancies regarding further favourable flow types are observed. The crucial role of large‐scale flow is further studied by assessing the relation between Northern Hemisphere teleconnection patterns and widespread convective activity. It is found that positive phases of the East Atlantic or Scandinavian patterns go along with a significant enhancement of convection‐favouring conditions in several European regions, which can be explained by anomalies in the large‐scale temperature and flow fields. Sea‐surface temperature over the Bay of Biscay likewise impacts the convective environment, with the largest positive effect over the western part of the study area

CEDIM Forensic Disaster Analysis Group (FDA) "Volcano & Tsunami Hunga Tonga" Report No. 1

Der Vulkanausbruch im Südpazifik (Tongainseln) Mitte Januar 2022 war der weltweit stärkste seit dem Ausbruch des Pinatubo. Hunga Tonga ist ein großer unterseeischer Vulkan etwa 70 km nordwestlich von Tongatapu (Südwestpazifik). Der Vulkan besteht aus zwei kleinen Inseln, Hunga Tonga und Hunga Ha\u27apai, die durch die jüngsten Ausbrüche in den Jahren 1988, 2009 und 2014/2015 miteinander verbunden wurden. Die Eruptionssequenz begann am 20. Dezember 2021 mit einer einzelnen Eruption. Es folgten ein größeres Ereignis am 14. Januar und der Hauptausbruch am 15. Januar gegen 17:15 Uhr Ortszeit (04:15 Uhr UTC). Alle Eruptionen waren mit einem starken Überschallknall verbunden. Die Explosion der Haupteruption war über Tausende von Kilometern zu hören. Die Haupteruption löste eine große Massenbewegung aus, die als Quelle für den anschließenden Tsunami vermutet wird. Der Tsunami wurde innerhalb von 15 Minuten auf Tongatapu beobachtet und unterbrach die Energieversorgung. Der Tsunami wurde im gesamten Pazifik, im Korallenmeer und im Tasmanischen Meer mit einer Ausbreitung von bis zu 3 m gesichtet. Es kam zu schweren lokalen Überschwemmungen auf Tonga (Run-up von 2 bis 5 m) und lokal zu leichten bis mäßigen Überschwemmungen entlang des Korallenmeers (< 0,5 – 3 m) und entlang des Pazifiks (0,5 – 1,5 m). Verschiedene Inseln von Tonga wurden teilweise überflutet. Die kleinen, unbewohnten Inseln Nuku und Tau wurden vollständig erodiert. Die Überschwemmungen auf Tongatapu und Nomuka zerstörten mehrere Gebäude. Korallenriffe und Barriere-Inseln spielten eine wichtige Rolle bei der Abmilderung der Auswirkungen des Tsunami. Die größten Schäden sind auf den Bruch des Unterseekabels von Fidschi nach Tonga zurückzuführen. Die wirtschaftlichen Verluste, die mit einem solchen Ausfall verbunden sind, werden angesichts der Kosten und der Knappheit von Satellitentelefonen groß sein. Ein großes Problem stellt derzeit die Asche auf der Landebahn von Tongatapu dar, so dass Hilfsflugzeuge meist nicht landen können, um Hilfsgüter zu liefern. Zusätzliche Kosten im Zusammenhang mit den Aufräumarbeiten und der Beseitigung der Asche werden auch in der Landwirtschaft anfallen, ebenso wie mögliche Infrastrukturprobleme durch die Verunreinigung der Wasserversorgung

Ambient conditions prevailing during hail events in central Europe

Around 26 000 severe convective storm tracks between 2005 and 2014 have been estimated from 2D radar reflectivity for parts of Europe, including Germany, France, Belgium, and Luxembourg. This event set was further combined with eyewitness reports, environmental conditions, and synoptic-scale fronts based on the ERA-Interim (ECMWF Reanalysis) reanalysis. Our analyses reveal that on average about a quarter of all severe thunderstorms in the investigation area were associated with a front. Over complex terrains, such as in southern Germany, the proportion of frontal convective storms is around 10 %–15 %, while over flat terrain half of the events require a front to trigger convection. Frontal storm tracks associated with hail on average produce larger hailstones and have a longer track. These events usually develop in a high-shear environment. Using composites of environmental conditions centered around the hailstorm tracks, we found that dynamical proxies such as deep-layer shear or storm-relative helicity become important when separating hail diameters and, in particular, their lengths; 0–3 km helicity as a dynamical proxy performs better compared to wind shear for the separation. In contrast, thermodynamical proxies such as the lifted index or lapse rate show only small differences between the different intensity classes.ISSN:1561-8633ISSN:1684-998

CEDIM Forensic Disaster Analysis Group (FDA): Noto Earthquake Japan (Jan. 2024)

The 2024 Noto earthquake in Japan, with a magnitude of 7.5 Mw, occurred on 1 January 2024 at 16:10 local time - seven kilometers north-northwest of the coast of Suzu. The strongest intensity was observed on the Noto Peninsula near the epicenter and towards the Sea of Japan; the quake was felt throughout Japan, including the Tokyo area. A USGS landslide model shows a maximum slip of about 3.7 meters along the fault plane with a total length of almost 200 km. A tsunami warning was issued shortly after the earthquake, with a maximum wave height of 5 meters predicted for the Noto peninsula. The waves that eventually were mostly just under 1 meter, except in the town of Suzu, located in a small bay, where several boats were damaged and houses along the coast were destroyed. Eyewitnesses reported waves as high as 3 meters. Low wave heights were reported from the other coasts of the Sea of Okhotsk. CEDIM damage estimates (based on JMA/RL intensity data and Shakemap) average $4.9 bn (with a range of$2.3 bn to $11.1 bn). This estimate excludes significant indirect losses, but includes direct damage to buildings, infrastructure, and production. Most of the significant economic damage is concentrated on the Noto Peninsula, particularly in the cities of Wajima, Suzu, and Nanao

CEDIM Forensic Disaster Analysis Group (FDA): Winter storm series: Ylenia, Zeynep, Antonia (int: Dudley, Eunice, Franklin) - February 2022 (NW & Central Europe)

Over a period of about a week, a series of powerful low-pressure systems swept across northwestern Europe and northern Central Europe. The wind fields of the very intense low pressure systems particularly affected the south of Ireland and England, northern Belgium, the Netherlands, the northern half of Germany, and the southwestern Baltic Sea region. Gale-force winds were recorded in many places, and even inland the wind reached speeds of more than 118 kph in places. The Needles station on the Isle of Wight possibly set a new wind speed record for England with as much as 196 kph. New peak wind speeds for the month of February were also recorded at some stations in Germany. These extraordinary wind speeds were most likely caused by a so-called sting jet. Hundreds of thousands of people were affected by power outages, and there were also considerable restrictions, particularly on rail services, which were completely shut down in some regions. Hamburg recorded a very severe storm surge for the first time since 2013, with water levels exceeding 3.5 meters above mean high tide. The hurricane-force low pressure systems claimed several lives and caused major property damage, which initial estimates put at more than 1 billion euros for Germany alone

Exceptional sequence of severe thunderstorms and related flash floods in May and June 2016 in Germany – Part 1: Meteorological background

Abstract. During a 15-day episode from 26 May to 9 June 2016, Germany was affected by an exceptionally large number of severe thunderstorms. Heavy rainfall, related flash floods and creek flooding, hail, and tornadoes caused substantial losses running into billions of euros (EUR). This paper analyzes the key features of the severe thunderstorm episode using extreme value statistics, an aggregated precipitation severity index, and two different objective weather-type classification schemes. It is shown that the thunderstorm episode was caused by the interaction of high moisture content, low thermal stability, weak wind speed, and large-scale lifting by surface lows, persisting over almost 2 weeks due to atmospheric blocking. For the long-term assessment of the recent thunderstorm episode, we draw comparisons to a 55-year period (1960–2014) regarding clusters of convective days with variable length (2–15 days) based on precipitation severity, convection-favoring weather patterns, and compound events with low stability and weak flow. It is found that clusters with more than 8 consecutive convective days are very rare. For example, a 10-day cluster with convective weather patterns prevailing during the recent thunderstorm episode has a probability of less than 1 %

Severe thunderstorms with large hail across Germany in June 2019

From 10 to 12 June 2019, severe thunderstorms affected large parts of Germany. Hail larger than golf ball size caused considerable damage, especially in the Munich area where losses amount to EUR 1 billion. This event thus ranks among the ten most expensive hail events in Europe in the last 40 years. Atmospheric blocking in combination with a moist, unstably stratified air mass provided an excellent setting for the development of severe, hail‐producing thunderstorms across the country. imageGerman Research Foundation http://dx.doi.org/10.13039/50110000165