ORCID Profile
0000-0002-6301-1634
Current Organisation
Rheinische Friedrich Wilhelms Universität Bonn Geographisches Institut
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Publisher: Oxford University Press (OUP)
Date: 05-2021
Abstract: Antibody-mediated rejection (AMR) remains a major management challenge in heart transplantation given the complexity of pathological diagnosis and dearth of evidence for effective management. Eculizumab, an anti-C5 monoclonal antibody which inhibits terminal complement activation, has been reported to decrease early AMR in sensitized renal transplant recipients. We report a case of a 29-year-old gentleman with chronic AMR 8 years after heart transplantation, manifesting as significant graft dysfunction. Donor-specific antibodies to DQ7 were found to be causative. Antibody-mediated rejection was managed with quadruple oral immunosuppressive therapy (mycophenolate, prednisolone, everolimus, and tacrolimus) as well as a sequence of broad-spectrum immunological therapies intravenous (IV) methylprednisolone, plasmapheresis, IV immunoglobulin, rituximab, bortezomib, tocilizumab, and splenic irradiation. No treatment had a sustained impact on donor-specific anti-HLA antibodies (DSAs) or graft function. After testing showed the DQ7 antibodies were complement-binding, a trial of eculizumab was started. This improved DSAs somewhat, and improved graft function and New York Heart Association functional class substantially. The patient was relisted for heart transplantation and successfully retransplanted in March 2018. Specifically, the new organ and recipient were matched at DQ7. After discontinuation of eculizumab, the patient has remained healthy and well, with normal graft function 28 months after retransplantation. To the best of our knowledge, this is the first case of chronic AMR in a heart transplant patient, successfully stabilized with eculizumab and bridged to retransplantation.
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-10518
Abstract: & & Teleconnections relate regional pressure patterns to local climate anomalies, influencing the variation of vegetation patterns. Over west continental Europe, droughts have been widely investigated with persistent low-frequency atmospheric circulation patterns (e.g. the North Atlantic Oscillation, NAO) with the centers over the Atlantic based on the 500mb height anomalies of the Northern Hemisphere. However, the effects of teleconnection patterns with the centers of active variability over the North and Caspian Seas is largely unexplored for droughts related to vegetation patterns. In this study, we explored the impact of the North Sea-Caspian Pattern (NCP) on regional ecohydrologic conditions in the Greater Region of Luxembourg in Western Europe. Using a Principal Component Analysis (PCA), we first decomposed the annual Normalized Difference Vegetation Index (NDVI) from the Global Inventory Monitoring and Modeling System (GIMMS) between 1981 and 2015. In the first PCA component, a distinctive greening trend of NDVI is detected since the late 1980s. However, the corresponding station observations and the ERA5 reanalysis data show that the region in west continental Europe became increasingly drier based on the difference between precipitation and evaporation. We explain the above paradoxical greening but drying patterns by the mechanism of NCP over the region. During the positive phase of NCP, the high pressure over the North Sea weakens circulation over the region and leads to warmer conditions in west continental Europe. These conditions are good for vegetation growth because the region was mainly energy-limited during the observed period at the annual scale based on a Budyko analysis. However, the positive phase of NCP also promotes ergent conditions at the lower troposphere and it reduces moisture flux over the region. In the Budyko space, the persistent positive phase of NCP would lead the energy-limited region to be water-limited. As the positive phase of NCP is expected to be more frequent along with the increasing global temperatures, the region may start to experience increasing water stress on vegetation. These results suggest that unforeseen droughts related to vegetation may be emerging in the region. New drought monitoring and management measures related to vegetation should be developed at west continental Europe, especially during the positive phase of NCP.& &
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-9365
Abstract: & & Drought conditions of Southeast China are associated with the sea surface temperature warm pool in the tropical Western Pacific, which is related to low-frequency hydroclimatic patterns and their teleconnections. Empirically, the moisture influx to the region is linked to the interannual and decadal teleconnections, including the Pacific Decadal Oscillation (PDO), the Pacific-Japan Oscillation (PJO) and the Silk Road Pattern (SRP). However, it is still unclear how those teleconnection patterns affect drought conditions in Southeast China via changes in monsoons& #8217 dynamics or wave activities. In this study, we use ERA5 reanalysis over the 1950-2019 period to explore the impacts of the PDO, PJO and SRP on Asian monsoons& #8217 dynamics and regional drought conditions over Southeast China, based on a self-calibrating Palmer Drought Severity Index (scPDSI). We specially use station data from the Greater Bay Area (GBA) which is a national key region for development in Southeast China which is affected by seasonal droughts in winters. Results indicate that drought conditions in Southeast China are significantly related to monsoons: the East Asia Monsoon (EAM), the Western North Pacific Monsoon (WNPM) and the Webster-Yang Monsoon (WYM), between 1950-2019. The strength of monsoons is modulated by PDO, PJO and SRP. A negative phase of SRP corresponds to a southward shift of the Asian westerly jet, strengthening winter Asian monsoons and causing drier conditions in the GBA. Similarly, a cold phase of PDO contributes to drier conditions in the GBA, by weakening Asian monsoons. For the negative phase of PJO, the trade wind of the Walker cell is weakened by the meridional pressure dipole over the West Pacific adjacent to the Southeast China coast. This pressure dipole reduces moisture influx to the continent by the weakened trade wind and leads to less precipitation over East China. Such three climate factors are also interacted through the modulations of monsoons and wave-activities. An extension of the Eliassen-Palm (EP) flux shows that the SRP relates to convective and dynamic wave-activities, which could explain changes in monsoons& #8217 dynamics and drought conditions in Southeast China. To investigate the future drought conditions over Southeast China, bias-corrected historical and RCP8.5 scenarios are used for six of the Coupled Model Intercomparison Project Phase 5 (CMIP5) models (i.e. ACCESS1, BCC, CNRM, IPSL, MPI, and GFDL) between 1861-2100. Among six models, IPSL and GFDL models reproduce the teleconnections well between changes in the monsoons and drought conditions over the GBA, for both historical simulations and future projections. Our results provide insights into the mechanisms of teleconnection patterns affecting drought monitoring and risk management in Southeast China.& & &
Publisher: Wiley
Date: 24-06-2022
DOI: 10.1002/ECO.2446
Abstract: Emerging drought stress on vegetation over western Eurasia is linked to varying teleconnection patterns. The North Sea–Caspian Pattern (NCP) is a relatively less studied Eurasian teleconnection pattern, which has a role on drought conditions and the consequence of changing conditions on vegetation. Between 1981 and 2015, we found that the Standardized Precipitation Index (SPI) and the Normalized Difference Vegetation Index (NDVI) have different trend patterns over various parts of western Eurasia. Specifically, the vegetation greenness is linked with wetter conditions over Scandinavia, and vegetation cover decreases over a drying central Asia. However, western Russia and Franceare paradoxically becoming greener under drier conditions. Using the Budyko framework, such paradoxical patterns are found in energy‐limited environmental systems, where vegetation growth is primarily promoted by warmer temperatures. While most studies focused on the impacts of the North Atlantic Oscillation (NAO), we test whether the NCP explains better the variability of meteorological drought and vegetation response over western Eurasia. We hypothesised that the positive phases of the NCP are correlated to high pressure anomalies over the North Sea, which can be associated with weakening onshore moisture advection, leading to warmer and dryness conditions. These conditions are driving vegetation greening, as western Eurasia is mainly energy limited. However, we show that as the climate is warming along with the teleconnection impacts, the future ecosystem over western Eurasia will be transferred from energy‐limited to water‐limited systems. This suggests that the observed vegetation greening over past three decades is unlikely to sustain in the future.
Publisher: MDPI AG
Date: 19-05-2017
DOI: 10.3390/W9050358
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-13363
Abstract: & & Precipitation extremes are commonly linked with land use types. The UKCP18 Convection-Permitting Model (CPM) Projections at 5km high resolution simulation provide opportunities to investigate probable relationships between precipitation extremes and land use types. Changes in the duration and severity of extreme precipitation events can be linked to landscape characteristics, which affect the risk of rapid and local hydrological hazards.& & & & Based on publicly accessible data and a standard approach, Local Climate Zones (LCZs) provide coherent descriptions of the form and function of urban landscapes. From the World Urban Database and Access Portal, the LCZ is used to translate relevant land attributes to urban canopy parameters for climate and weather modelling applications at appropriate scales. Using the Severn River Basin as a case study, we use LCZ data to calculate urban fractions to investigate the roles of urban land types to the extreme distribution parameters.& & & & In conjunction with the LCZ data, the Corine Land Cover (CLC) and the Moderate Resolution Imaging Spectroradiometer (MODIS) datasets are used to benchmark how future changes in rainfall intensities and seasonal patterns might be related to land use. The results are used to generate possible hypotheses to run different CPM models based on the LCZ data.& & & & Based on these findings, we present a novel land-use-based approach for water hazard management addressing hydrological risk connected to regional climate resilience. For management authorities and infrastructure owners, precipitation extreme risk related to land use is critical for their long-term investment planning. The proposed methodology would be advantageous to many UK water regulators and stakeholders in generating more informative precipitation extreme estimations based on land use, for the high greenhouse gas emissions scenario RCP8.5.& &
Publisher: Wiley
Date: 09-2021
DOI: 10.1002/HYP.14356
Abstract: Ocean–atmosphere modes of climate variability in the Pacific and Indian oceans, as well as monsoons, regulate the regional wet and dry episodes in tropical regions. However, how those modes of climate variability, and their interactions, lead to spatial differences in drought patterns over tropical Asia at seasonal to interannual time scales remains unclear. This study aims to analyse the hydroclimate processes for both short‐ and long‐term spatial drought patterns (3‐, 6, 12‐ and 24‐months) over Peninsular Malaysia using the Standardized Precipitation Index, Standardized Precipitation Evapotranspiration Index, and Palmer Drought Severity Index. Besides that, a generalized least squares regression is used to explore underlying circulation mechanisms of these spatio‐temporal drought patterns. The tested drought indices indicate a tendency towards wetter conditions over Peninsular Malaysia. Based on principal component analysis, distinct spatio‐temporal drought patterns are revealed, suggesting North–South and East–West gradients in drought distribution. The Pacific El Nino Southern Oscillation (ENSO), the South Western Indian Ocean (SWIO) variability, and the quasi‐biennial oscillation (QBO) are significant contributors to the observed spatio‐temporal variability in drought. Both the ENSO and the SWIO modulate the North–South gradient in drought conditions over Peninsular Malaysia, while the QBO contributes more to the East–West gradient. Through modulating regional moisture fluxes, the warm phases of the ENSO and the SWIO, and the western phases of the QBO weaken the southwest and northeast monsoon, leading to precipitation deficits and droughts over Peninsular Malaysia. The East–West or North–South gradients in droughts are related to the middle mountains blocking southwest and northeast moisture fluxes towards Peninsular Malaysia. In addition, the ENSO and QBO variations are significantly leading to short‐term droughts (less than a year), while the SWIO is significantly associated with longer‐duration droughts (2 years or more). Overall, this work demonstrates how spatio‐temporal drought patterns in tropical regions are related to monsoons and moisture transports affected by the oscillations over the Pacific and Indian oceans, which is important for national water risk management.
Publisher: MDPI AG
Date: 19-07-2017
DOI: 10.3390/W9070542
Abstract: Quantifying the travel times, pathways, and dispersion of solutes moving through stream environments is critical for understanding the biogeochemical cycling processes that control ecosystem functioning. Validation of stream solute transport and exchange process models requires data obtained from in-stream measurement of chemical concentration changes through time. This can be expensive and time consuming, leading to a need for cheap distributed sensor arrays that respond instantly and record chemical transport at points of interest on timescales of seconds. To meet this need we apply new, low-cost (in the order of a euro per sensor) potentiometric chloride sensors used in a distributed array to obtain data with high spatial and temporal resolution. The application here is to monitoring in-stream hydrodynamic transport and dispersive mixing of an injected chemical, in this case NaCl. We present data obtained from the distributed sensor array under baseflow conditions for stream reaches in Luxembourg and Western Australia. The reaches were selected to provide a range of increasingly complex in-channel flow patterns. Mid-channel sensor results are comparable to data obtained from more expensive electrical conductivity meters, but simultaneous acquisition of tracer data at several positions across the channel allows far greater spatial resolution of hydrodynamic mixing processes and identification of chemical ‘dead zones’ in the study reaches.
Location: Germany
No related grants have been discovered for Julian Klaus.