https://repos.hcu-hamburg.de:443 repOS captures, stores, indexes, preserves, and distributes digital research material. Tue, 17 Mar 2026 00:00:12 GMT 2026-03-17T00:00:12Z https://repos.hcu-hamburg.de:443/handle/hcu/1199 Title: Return Levels of Dry Extreme Events in Terrestrial Water Storage From Satellite Gravimetry and CMIP6 Global Coupled Climate Models Authors: Middendorf, Klara; Dobslaw, Henryk; Jensen, Laura; Eicker, Annette Abstract: Satellite gravimetry as realized with GRACE and GRACE-FO provides a novel opportunity to study extreme deviations from annually varying terrestrial water storage (TWS) in all continental areas of our planet. By utilizing the generalized extreme value (GEV) distribution, we estimate return levels for events that are expected to happen once every 10 (i.e., 1-in-10) years. With two GRACE-like reconstructions spanning over 40 and 114 years, respectively, we show that the currently available data record of 20 years is already sufficiently long to derive robust estimates of those return levels. When contrasting the GRACE/-FO results to model experiments from the CMIP6 archive extending until the year 2100 by concatenating historical runs and climate projections under the SSP5-8.5 socioeconomic pathway, we find that (a) the multi-model median from CMIP6 has the overall best agreement with the satellite data, thereby nicely confirming the validity of a central assumption of many climate-related studies that heavily rely on ensemble statistics. We also find that (b) CMIP6 model runs contain only modest deviations of 1-in-10 years return levels from the beginning of the 20th century when compared to present-day, but predict stronger changes toward more extreme return levels by the end of the 21st century. On the other hand, we also find substantial differences between satellite data and individual model experiments, which opens new opportunities to inform, validate and/or calibrate numerical climate models with satellite gravimetry data from GRACE, GRACE-FO, and in future also GRACE-C. Mon, 16 Mar 2026 09:18:27 GMT https://repos.hcu-hamburg.de:443/handle/hcu/1199 2026-03-16T09:18:27Z https://repos.hcu-hamburg.de:443/handle/hcu/1197 Title: Revisiting Sub‐Surface Drought Cascades With Daily Satellite Observations of Soil Moisture and Terrestrial Water Storage Authors: Blank, Daniel Hendrik; Eicker, Annette; Reager, John T.; Güntner, Andreas Abstract: The increasing frequency, intensity, and duration of extreme heat and drought events in a warming climate make it crucial to understand the relationship between surface and subsurface water storage dynamics during these events. Changes in water storage can be studied globally using satellite observations. Microwave remote sensing observes the upper few centimeters of the soil, while satellite gravimetry detects changes in the entire column of terrestrial water storage. We use daily data of the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO), satellite-based surface soil moisture data and root zone products from Soil Moisture Ocean Salinity, Soil Moisture Active Passive, and European Space Agency Climate Change Initiative on a harmonized 1 global grid to study the evolution of water storage deficits across different soil layers. The joint analysis of the three types of data provides valuable insight into the hydrological dynamics in different soil depths and subsurface water storage compartments. To identify different dynamics, we compute the rate of change from de-seasonalized water storage anomaly time series to assess how quickly the system accumulates storage deficits during drought conditions and recovers from them for different integration depths in the subsurface. The results indicate characteristic patterns of the temporal dynamics of drought recovery with fast fluctuations and short recovery times for surface soil moisture, a prolonged behavior in the root-zone, and an even slower response in the entire water column. This highlights that the cascading propagation of drought dynamics from the surface to the subsurface can be quantified by remote sensing data with daily resolution at the global scale. Mon, 09 Mar 2026 08:52:07 GMT https://repos.hcu-hamburg.de:443/handle/hcu/1197 2026-03-09T08:52:07Z https://repos.hcu-hamburg.de:443/handle/hcu/1182 Title: A Framework for Exergetic Life Cycle Assessment of Residential Buildings Authors: Shokouhi, Samira Abstract: This thesis develops a framework for integrating exergy analysis into Life Cycle Assessment (LCA) applied to residential buildings. The central research question addresses whether, from an exergy perspective encompassing both resource use and emissions, it is more sustainable to renovate an existing residential building or to construct a new one using improved materials and low-emission heating systems. The study employs a multi-dimensional exergy-based assessment approach, quantifying three primary categories: (1) Resource Exergy Consumption of Energy (RExC-E), calculated using Resource Exergy Analysis (REA); (2) Cumulative Exergy Consumption including Chemical Exergy Consumption of Materials (CExC-M) derived from standard chemical exergy values and Primary Exergy Consumption of Energy (PExC-E) for construction materials, ;and (3) Chemical Exergy of Emissions (CExE) for environmental outputs. This integrated framework provides a unified thermodynamic basis for evaluating both resource depletion and environmental emissions. The methodology is demonstrated through a case study of a representative 1999 German multi-family row house (Neu-Ulm), comparing three fundamentally different scenarios over a 50-year period (2025–2075): (1) the original building in its existing state; (2) a renovated scenario with thermal envelope improvements and renewable heating; and (3) a new-build scenario with advanced components, timber structure, and efficient systems. Key findings indicate that the renovated scenario yields the lowest Overall Exergy Impact, demonstrating that upgrading heating systems and building envelopes before the end of a building's service life can substantially reduce environmental impacts. The new-build scenario, despite improvements in operational energy, exhibits higher total exergy due to substantial material burdens from new construction. Sensitivity analysis reveals that strategic decisions regarding material reuse, such as retaining the original foundation, can significantly improve the environmental performance of new construction. The study demonstrates that exergy-based LCA can provide robust thermodynamic foundations for sustainability assessment, offering advantages over conventional LCA by incorporating energy quality and enabling unified comparison of resource consumption and emissions. However, limitations remain regarding methodological consistency. The research supports renovation as the most effective strategy for minimizing exergetic and environmental impacts in building stock interventions, while highlighting the critical importance of methodological transparency and scope definition in exergy-based assessments. Tue, 24 Feb 2026 07:12:13 GMT https://repos.hcu-hamburg.de:443/handle/hcu/1182 2026-02-24T07:12:13Z https://repos.hcu-hamburg.de:443/handle/hcu/1198 Title: Crafting open innovation for collaboration: Insights into multi-actor dynamics for the circular economy transformation Authors: Ibach, Merle; Tatum, Kimberly; Knieling, Jörg Abstract: The European Union’s circular economy (CE) policy aims to foster closed-loop systems that reduce waste and resource use, yet its practical implementation remains limited. Open innovation (OI)—the cross-organizational sharing of knowledge and collaborative problem-solving—offers a promising but underexplored pathway to accelerate circular economy transformation, particularly by enabling collaboration among diverse actors. This study addresses a critical research gap by examining how OI instruments mobilize multi-actor collaboration for circular economy goals, using an in-depth case study of Fab City Hamburg (FCH)—a pioneering initiative combining OI and CE principles to promote local, open, and circular production. Drawing on qualitative analysis of two circular open labs within FCH and integrating insights from transition theory with the small wins governance framework, we offer original insights into the dynamics of open innovation for circular economy transformation. Our findings reveal that open innovation instruments foster spreading and partial deepening of circular practices by supporting learning, experimentation, and community-building. However, significant barriers to broadening collaborations persist, including conflicting understandings of openness and circularity, organizational asymmetries, and unstable funding structures. The study contributes to the literature on CE and OI by offering a multi-actor, governance-oriented perspective on collaborative circular innovation. We highlight both synergies and frictions in applying OI to CE contexts and provide practical guidance for policymakers, intermediaries, and practitioners seeking to foster collaborative innovation and overcome barriers in circular economy transitions. Wed, 18 Feb 2026 10:48:10 GMT https://repos.hcu-hamburg.de:443/handle/hcu/1198 2026-02-18T10:48:10Z