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BETA
Wyser, Klaus
Alternative names
Publications (10 of 34) Show all publications
Betts, R. A., Alfieri, L., Bradshaw, C., Caesar, J., Feyen, L., Friedlingstein, P., . . . Wyser, K. (2018). Changes in climate extremes, fresh water availability and vulnerability to food insecurity projected at 1.5 degrees C and 2 degrees C global warming with a higher-resolution global climate model. Philosophical Transactions. Series A: Mathematical, physical, and engineering science, 376(2119), Article ID 20160452.
Open this publication in new window or tab >>Changes in climate extremes, fresh water availability and vulnerability to food insecurity projected at 1.5 degrees C and 2 degrees C global warming with a higher-resolution global climate model
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2018 (English)In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 376, no 2119, article id 20160452Article in journal (Refereed) Published
National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-4578 (URN)10.1098/rsta.2016.0452 (DOI)000429046300007 ()29610383 (PubMedID)
Available from: 2018-04-25 Created: 2018-04-25 Last updated: 2018-04-25Bibliographically approved
Dosio, A., Mentaschi, L., Fischer, E. M. & Wyser, K. (2018). Extreme heat waves under 1.5 degrees C and 2 degrees C global warming. Environmental Research Letters, 13(5), Article ID 054006.
Open this publication in new window or tab >>Extreme heat waves under 1.5 degrees C and 2 degrees C global warming
2018 (English)In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 13, no 5, article id 054006Article in journal (Refereed) Published
National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-4656 (URN)10.1088/1748-9326/aab827 (DOI)000430945200002 ()
Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2018-05-16Bibliographically approved
Koutroulis, A. G., Papadimitriou, L. V., Grillakis, M. G., Tsanis, I. K., Wyser, K. & Betts, R. A. (2018). Freshwater vulnerability under high end climate change. A pan-European assessment. Science of the Total Environment, 613, 271-286
Open this publication in new window or tab >>Freshwater vulnerability under high end climate change. A pan-European assessment
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2018 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 613, p. 271-286Article in journal (Refereed) Published
National Category
Climate Research
Identifiers
urn:nbn:se:smhi:diva-4423 (URN)10.1016/j.scitotenv.2017.09.074 (DOI)000414160500029 ()
Available from: 2017-11-21 Created: 2017-11-21 Last updated: 2017-11-21Bibliographically approved
Naumann, G., Alfieri, L., Wyser, K., Mentaschi, L., Betts, R. A., Carrao, H., . . . Feyen, L. (2018). Global Changes in Drought Conditions Under Different Levels of Warming. Geophysical Research Letters, 45(7), 3285-3296
Open this publication in new window or tab >>Global Changes in Drought Conditions Under Different Levels of Warming
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2018 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 7, p. 3285-3296Article in journal (Refereed) Published
National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-4826 (URN)10.1002/2017GL076521 (DOI)000435743400047 ()
Available from: 2018-08-06 Created: 2018-08-06 Last updated: 2018-08-06Bibliographically approved
Alfieri, L., Bisselink, B., Dottori, F., Naumann, G., de Roo, A., Salamon, P., . . . Feyen, L. (2017). Global projections of river flood risk in a warmer world. Earth's Future, 5(2), 171-182
Open this publication in new window or tab >>Global projections of river flood risk in a warmer world
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2017 (English)In: Earth's Future, ISSN 1384-5160, E-ISSN 2328-4277, Vol. 5, no 2, p. 171-182Article in journal (Refereed) Published
National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-4067 (URN)10.1002/2016EF000485 (DOI)000396932200004 ()
Available from: 2017-04-25 Created: 2017-04-25 Last updated: 2017-04-25Bibliographically approved
Bellucci, A., Haarsma, R., Gualdi, S., Athanasiadis, P. J., Caian, M., Cassou, C., . . . Yang, S. (2015). An assessment of a multi-model ensemble of decadal climate predictions. Climate Dynamics, 44(9-10), 2787-2806
Open this publication in new window or tab >>An assessment of a multi-model ensemble of decadal climate predictions
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2015 (English)In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 44, no 9-10, p. 2787-2806Article in journal (Refereed) Published
Abstract [en]

A multi-model ensemble of decadal prediction experiments, performed in the framework of the EU-funded COMBINE (Comprehensive Modelling of the Earth System for Better Climate Prediction and Projection) Project following the 5th Coupled Model Intercomparison Project protocol is examined. The ensemble combines a variety of dynamical models, initialization and perturbation strategies, as well as data assimilation products employed to constrain the initial state of the system. Taking advantage of the multi-model approach, several aspects of decadal climate predictions are assessed, including predictive skill, impact of the initialization strategy and the level of uncertainty characterizing the predicted fluctuations of key climate variables. The present analysis adds to the growing evidence that the current generation of climate models adequately initialized have significant skill in predicting years ahead not only the anthropogenic warming but also part of the internal variability of the climate system. An important finding is that the multi-model ensemble mean does generally outperform the individual forecasts, a well-documented result for seasonal forecasting, supporting the need to extend the multi-model framework to real-time decadal predictions in order to maximize the predictive capabilities of currently available decadal forecast systems. The multi-model perspective did also allow a more robust assessment of the impact of the initialization strategy on the quality of decadal predictions, providing hints of an improved forecast skill under full-value (with respect to anomaly) initialization in the near-term range, over the Indo-Pacific equatorial region. Finally, the consistency across the different model predictions was assessed. Specifically, different systems reveal a general agreement in predicting the near-term evolution of surface temperatures, displaying positive correlations between different decadal hindcasts over most of the global domain.

National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-2002 (URN)10.1007/s00382-014-2164-y (DOI)000351459800026 ()
Available from: 2016-04-13 Created: 2016-03-03 Last updated: 2017-11-30Bibliographically approved
Hytteborn, J. K., Temnerud, J., Alexander, R. B., Boyer, E. W., Futter, M. N., Froberg, M., . . . Bishop, K. H. (2015). Patterns and predictability in the intra-annual organic carbon variability across the boreal and hemiboreal landscape. Science of the Total Environment, 520, 260-269
Open this publication in new window or tab >>Patterns and predictability in the intra-annual organic carbon variability across the boreal and hemiboreal landscape
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2015 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 520, p. 260-269Article in journal (Refereed) Published
Abstract [en]

Factors affecting total organic carbon (TOC) concentrations in 215 watercourses across Sweden were investigated using parameter parsimonious regression approaches to explain spatial and temporal variabilities of the TOC water quality responses. We systematically quantified the effects of discharge, seasonality, and long-term trend as factors controlling intra-annual (among year) and inter-annual (within year) variabilities of TOC by evaluating the spatial variability in model coefficients and catchment characteristics (e.g. land cover, retention time, soil type). Catchment area (0.18-47,000 km(2)) and land cover types (forests, agriculture and alpine terrain) are typical for the boreal and hemiboreal zones across Fennoscandia. Watercourses had at least 6 years of monthly water quality observations between 1990 and 2010. Statistically significant models (p < 0.05) describing variation of TOC in streamflow were identified in 209 of 215 watercourses with a mean Nash-Sutcliffe efficiency index of 0.44. Increasing long-term trends were observed in 149 (70%) of the watercourses, and intra-annual variation in TOC far exceeded inter-annual variation. The average influences of the discharge and seasonality terms on intra-annual variations in daily TOC concentration were 1.4 and 1.3 mg l(-1) (13 and 12% of the mean annual TOC), respectively. The average increase in TOC was 0.17 mg l(-1) year(-1) (1.6% year(-1)). Multivariate regression with over 90 different catchment characteristics explained 21% of the spatial variation in the linear trend coefficient, less than 20% of the variation in the discharge coefficient and 73% of the spatial variation in mean TOC. Specific discharge, water residence time, the variance of daily precipitation, and lake area, explained 45% of the spatial variation in the amplitude of the TOC seasonality. Because the main drivers of temporal variability in TOC are seasonality and discharge, first-order estimates of the influences of climatic variability and change on TOC concentration should be predictable if the studied catchments continue to respond similarly. (C) 2015 Elsevier B.V. All rights reserved.

National Category
Oceanography, Hydrology and Water Resources
Research subject
Hydrology
Identifiers
urn:nbn:se:smhi:diva-1988 (URN)10.1016/j.scitotenv.2015.03.041 (DOI)000353509500028 ()25817763 (PubMedID)
Available from: 2016-04-25 Created: 2016-03-03 Last updated: 2018-01-10Bibliographically approved
Jiang, X., Waliser, D. E., Xavier, P. K., Petch, J., Klingaman, N. P., Woolnough, S. J., . . . Zhu, H. (2015). Vertical structure and physical processes of the Madden-Julian oscillation: Exploring key model physics in climate simulations. Journal of Geophysical Research - Atmospheres, 120(10), 4718-4748
Open this publication in new window or tab >>Vertical structure and physical processes of the Madden-Julian oscillation: Exploring key model physics in climate simulations
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2015 (English)In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 120, no 10, p. 4718-4748Article in journal (Refereed) Published
Abstract [en]

Aimed at reducing deficiencies in representing the Madden-Julian oscillation (MJO) in general circulation models (GCMs), a global model evaluation project on vertical structure and physical processes of the MJO was coordinated. In this paper, results from the climate simulation component of this project are reported. It is shown that the MJO remains a great challenge in these latest generation GCMs. The systematic eastward propagation of the MJO is only well simulated in about one fourth of the total participating models. The observed vertical westward tilt with altitude of the MJO is well simulated in good MJO models but not in the poor ones. Damped Kelvin wave responses to the east of convection in the lower troposphere could be responsible for the missing MJO preconditioning process in these poor MJO models. Several process-oriented diagnostics were conducted to discriminate key processes for realistic MJO simulations. While large-scale rainfall partition and low-level mean zonal winds over the Indo-Pacific in a model are not found to be closely associated with its MJO skill, two metrics, including the low-level relative humidity difference between high- and low-rain events and seasonal mean gross moist stability, exhibit statistically significant correlations with the MJO performance. It is further indicated that increased cloud-radiative feedback tends to be associated with reduced amplitude of intraseasonal variability, which is incompatible with the radiative instability theory previously proposed for the MJO. Results in this study confirm that inclusion of air-sea interaction can lead to significant improvement in simulating the MJO.

National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-1970 (URN)10.1002/2014JD022375 (DOI)000356696800017 ()
Available from: 2016-04-26 Created: 2016-03-03 Last updated: 2017-11-30Bibliographically approved
Koenigk, T., Brodeau, L., Graversen, R. G., Karlsson, J., Svensson, G., Tjernstrom, M., . . . Wyser, K. (2013). Arctic climate change in 21st century CMIP5 simulations with EC-Earth. Climate Dynamics, 40(11-12), 2719-2743
Open this publication in new window or tab >>Arctic climate change in 21st century CMIP5 simulations with EC-Earth
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2013 (English)In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 40, no 11-12, p. 2719-2743Article in journal (Refereed) Published
Abstract [en]

The Arctic climate change is analyzed in an ensemble of future projection simulations performed with the global coupled climate model EC-Earth2.3. EC-Earth simulates the twentieth century Arctic climate relatively well but the Arctic is about 2 K too cold and the sea ice thickness and extent are overestimated. In the twenty-first century, the results show a continuation and strengthening of the Arctic trends observed over the recent decades, which leads to a dramatically changed Arctic climate, especially in the high emission scenario RCP8.5. The annually averaged Arctic mean near-surface temperature increases by 12 K in RCP8.5, with largest warming in the Barents Sea region. The warming is most pronounced in winter and autumn and in the lower atmosphere. The Arctic winter temperature inversion is reduced in all scenarios and disappears in RCP8.5. The Arctic becomes ice free in September in all RCP8.5 simulations after a rapid reduction event without recovery around year 2060. Taking into account the overestimation of ice in the twentieth century, our model results indicate a likely ice-free Arctic in September around 2040. Sea ice reductions are most pronounced in the Barents Sea in all RCPs, which lead to the most dramatic changes in this region. Here, surface heat fluxes are strongly enhanced and the cloudiness is substantially decreased. The meridional heat flux into the Arctic is reduced in the atmosphere but increases in the ocean. This oceanic increase is dominated by an enhanced heat flux into the Barents Sea, which strongly contributes to the large sea ice reduction and surface-air warming in this region. Increased precipitation and river runoff lead to more freshwater input into the Arctic Ocean. However, most of the additional freshwater is stored in the Arctic Ocean while the total Arctic freshwater export only slightly increases.

Keywords
Arctic climate, Future scenarios, CMIP5, Global coupled atmosphere-ocean modeling, Coupled Arctic climate processes
National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-375 (URN)10.1007/s00382-012-1505-y (DOI)000319360800010 ()
Available from: 2015-04-07 Created: 2015-03-31 Last updated: 2017-12-04Bibliographically approved
Sheldon, Johnston, M., Eliasson, S., Eriksson, P., Forbes, R. M., Wyser, K. & Zelinka, M. D. (2013). Diagnosing the average spatio-temporal impact of convective systems - Part 1: A methodology for evaluating climate models. Atmospheric Chemistry And Physics, 13(23), 12043-12058
Open this publication in new window or tab >>Diagnosing the average spatio-temporal impact of convective systems - Part 1: A methodology for evaluating climate models
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2013 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 23, p. 12043-12058Article in journal (Refereed) Published
Abstract [en]

An earlier method to determine the mean response of upper-tropospheric water to localised deep convective systems (DC systems) is improved and applied to the EC-Earth climate model. Following Zelinka and Hartmann (2009), several fields related to moist processes and radiation from various satellites are composited with respect to the local maxima in rain rate to determine their spatio-temporal evolution with deep convection in the central Pacific Ocean. Major improvements to the earlier study are the isolation of DC systems in time so as to prevent multiple sampling of the same event, and a revised definition of the mean background state that allows for better characterisation of the DC-system-induced anomalies. The observed DC systems in this study propagate westward at similar to 4 ms(-1). Both the upper-tropospheric relative humidity and the outgoing longwave radiation are substantially perturbed over a broad horizontal extent and for periods > 30 h. The cloud fraction anomaly is fairly constant with height but small maximum can be seen around 200 hPa. The cloud ice water content anomaly is mostly confined to pressures greater than 150 hPa and reaches its maximum around 450 hPa, a few hours after the peak convection. Consistent with the large increase in upper-tropospheric cloud ice water content, albedo increases dramatically and persists about 30 h after peak convection. Applying the compositing technique to EC-Earth allows an assessment of the model representation of DC systems. The model captures the large-scale responses, most notably for outgoing longwave radiation, but there are a number of important differences. DC systems appear to propagate east-ward in the model, suggesting a strong link to Kelvin waves instead of equatorial Rossby waves. The diurnal cycle in the model is more pronounced and appears to trigger new convection further to the west each time. Finally, the modelled ice water content anomaly peaks at pressures greater than 500 hPa and in the upper troposphere between 250 hPa and 500 hPa, there is less ice than the observations and it does not persist as long after peak convection. The modelled upper-tropospheric cloud fraction anomaly, however, is of a comparable magnitude and exhibits a similar longevity as the observations.

National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-395 (URN)10.5194/acp-13-12043-2013 (DOI)000328616800029 ()
Available from: 2015-04-10 Created: 2015-03-31 Last updated: 2017-12-04Bibliographically approved
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