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Subject: Extreme events ×

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Now showing 1 - 5 of 5
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    Changes in meandering of the Northern Hemisphere circulation
    (Bristol : Institute of Physics Publishing, 2016) Di Capua, G.; Coumou, D.
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    Agricultural water balance in the polder Scheidgraben (Brandenburg)
    (Berlin ; Heidelberg : Springer, 2022) Drastig, Katrin; Schmidtke, Lea; Jacobs, Helen; Recker, Martin
    A predicted increase in water demand for irrigated agriculture in the wake of climate change, and the threat of more extensive periods of drought, poses a challenge to the availability of groundwater resources in Germany. In this study, water availability and water withdrawal for agricultural irrigation are calculated for the polder Scheidgraben (Brandenburg). The agricultural water demand in the Scheidgraben polder is modeled using the AgroHyd Farmmodel. Climate data, soil data, plant-specific data and operating data of all farms in the polder are used as a data basis. In the dry years 2018 and 2019, more than 20% of the potentially available water in the Scheidgraben polder was used for irrigation. The use of water resources by agricultural water withdrawals in the area may increasingly be a problem in the future. In some regions of Brandenburg, region-specific calculations for water management are necessary due to a wide range of conflicts and thus steadily increasing challenges for water authorities.
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    Increasing compound warm spells and droughts in the Mediterranean Basin
    (Amsterdam [u.a.] : Elsevier, 2021) Vogel, Johannes; Paton, Eva; Aich, Valentin; Bronstert, Axel
    The co-occurrence of warm spells and droughts can lead to detrimental socio-economic and ecological impacts, largely surpassing the impacts of either warm spells or droughts alone. We quantify changes in the number of compound warm spells and droughts from 1979 to 2018 in the Mediterranean Basin using the ERA5 data set. We analyse two types of compound events: 1) warm season compound events, which are extreme in absolute terms in the warm season from May to October and 2) year-round deseasonalised compound events, which are extreme in relative terms respective to the time of the year. The number of compound events increases significantly and especially warm spells are increasing strongly – with an annual growth rates of 3.9 (3.5) % for warm season (deseasonalised) compound events and 4.6 (4.4) % for warm spells –, whereas for droughts the change is more ambiguous depending on the applied definition. Therefore, the rise in the number of compound events is primarily driven by temperature changes and not the lack of precipitation. The months July and August show the highest increases in warm season compound events, whereas the highest increases of deseasonalised compound events occur in spring and early summer. This increase in deseasonalised compound events can potentially have a significant impact on the functioning of Mediterranean ecosystems as this is the peak phase of ecosystem productivity and a vital phenophase.
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    Adiabatic theory of champion solitons
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2016) Pickartz, Sabrina; Bandelow, Uwe; Amiranashvili, Shalva
    We consider scattering of small-amplitude dispersive waves at an intense optical soliton which constitutes a nonlinear perturbation of the refractive index. Specifically, we consider a single-mode optical fiber and a group velocity matched pair: an optical soliton and a nearly perfectly reflected dispersive wave, a fiber-optical analogue of the event horizon. By combining (i) an adiabatic approach that is used in soliton perturbation theory and (ii) scattering theory from Quantum Mechanics, we give a quantitative account for the evolution of all soliton parameters. In particular, we quantify the increase in the soliton peak power that may result in spontaneous appearance of an extremely large, so-called champion soliton. The presented adiabatic theory agrees well with the numerical solutions of the pulse propagation equation. Moreover, for the first time we predict the full frequency band of the scattered dispersive waves and explain an emerging caustic structure in the space-time domain.
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    Efficient all-optical control of solitons
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2016) Pickartz, Sabrina; Bandelow, Uwe; Amiranashvili, Shalva
    We consider the phenomenon of an optical soliton controlled (e.g. amplified) by a much weaker second pulse which is efficiently scattered at the soliton. An important problem in this context is to quantify the small range of parameters at which the interaction takes place. This has been achieved by using adiabatic ODEs for the soliton characteristics, which is much faster than an empirical scan of the full propagation equations for all parameters in question.