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  • 1. Ahmadalipour, Ali
    et al.
    Moradkhani, Hamid
    Rana, Arun
    SMHI.
    Accounting for downscaling and model uncertainty in fine-resolution seasonal climate projections over the Columbia River Basin2018In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, no 1-2, p. 717-733Article in journal (Refereed)
  • 2. Angel Gaertner, Miguel
    et al.
    Jesus Gonzalez-Aleman, Juan
    Romera, Raquel
    Dominguez, Marta
    Gil, Victoria
    Sanchez, Enrique
    Gallardo, Clemente
    Marcello Miglietta, Mario
    Walsh, Kevin J. E.
    Sein, Dmitry V.
    Somot, Samuel
    Dell'Aquila, Alessandro
    Teichmann, Claas
    Ahrens, Bodo
    Buonomo, Erasmo
    Colette, Augustin
    Bastin, Sophie
    van Meijgaard, Erik
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Simulation of medicanes over the Mediterranean Sea in a regional climate model ensemble: impact of ocean-atmosphere coupling and increased resolution2018In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 51, no 3, p. 1041-1057Article in journal (Refereed)
  • 3. Bellucci, A.
    et al.
    Haarsma, R.
    Gualdi, S.
    Athanasiadis, P. J.
    Caian, Mihaela
    SMHI, Research Department, Climate research - Rossby Centre.
    Cassou, C.
    Fernandez, E.
    Germe, A.
    Jungclaus, J.
    Kroeger, J.
    Matei, D.
    Mueller, W.
    Pohlmann, H.
    Salas y Melia, D.
    Sanchez, E.
    Smith, D.
    Terray, L.
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Yang, S.
    An assessment of a multi-model ensemble of decadal climate predictions2015In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 44, no 9-10, p. 2787-2806Article in journal (Refereed)
    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.

  • 4.
    Berg, Peter
    et al.
    SMHI, Research Department, Hydrology.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Koenigk, Torben
    SMHI, Research Department, Climate research - Rossby Centre.
    On the effects of constraining atmospheric circulation in a coupled atmosphere-ocean Arctic regional climate model2016In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 46, no 11-12, p. 3499-3515Article in journal (Refereed)
  • 5.
    Berg, Peter
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Wagner, Sven
    Kunstmann, Harald
    Schaedler, Gerd
    High resolution regional climate model simulations for Germany: part I-validation2013In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 40, no 1-2, p. 401-414Article in journal (Refereed)
    Abstract [en]

    A five-member ensemble of regional climate model (RCM) simulations for Europe, with a high resolution nest over Germany, is analysed in a two-part paper: Part I (the current paper) presents the performance of the models for the control period, and Part II presents results for near future climate changes. Two different RCMs, CLM and WRF, were used to dynamically downscale simulations with the ECHAM5 and CCCma3 global climate models (GCMs), as well as the ERA40-reanalysis for validation purposes. Three realisations of ECHAM5 and one with CCCma3 were downscaled with CLM, and additionally one realisation of ECHAM5 with WRF. An approach of double nesting was used, first to an approximately 50 km resolution for entire Europe and then to a domain of approximately 7 km covering Germany and its near surroundings. Comparisons of the fine nest simulations are made to earlier high resolution simulations for the region with the RCM REMO for two ECHAM5 realisations. Biases from the GCMs are generally carried over to the RCMs, which can then reduce or worsen the biases. The bias of the coarse nest is carried over to the fine nest but does not change in amplitude, i.e. the fine nest does not add additional mean bias to the simulations. The spatial pattern of the wet bias over central Europe is similar for all CLM simulations, and leads to a stronger bias in the fine nest simulations compared to that of WRF and REMO. The wet bias in the CLM model is found to be due to a too frequent drizzle, but for higher intensities the distributions are well simulated with both CLM and WRF at the 50 and 7 km resolutions. Also the spatial distributions are close to high resolution gridded observations. The REMO model has low biases in the domain averages over Germany and no drizzle problem, but has a shift in the mean precipitation patterns and a strong overestimation of higher intensities. The GCMs perform well in simulating the intensity distribution of precipitation at their own resolution, but the RCMs add value to the distributions when compared to observations at the fine nest resolution.

  • 6. Brodeau, Laurent
    et al.
    Koenigk, Torben
    SMHI, Research Department, Climate research - Rossby Centre.
    Extinction of the northern oceanic deep convection in an ensemble of climate model simulations of the 20th and 21st centuries2016In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 46, no 9-10, p. 2863-2882Article in journal (Refereed)
  • 7.
    Caian, Mihaela
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Koenigk, Torben
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Devasthale, Abhay
    SMHI, Research Department, Atmospheric remote sensing.
    An interannual link between Arctic sea-ice cover and the North Atlantic Oscillation2018In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, no 1-2, p. 423-441Article in journal (Refereed)
  • 8.
    Caian, Mihaela
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Koenigk, Torben
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Devasthale, Abhay
    SMHI, Research Department, Atmospheric remote sensing.
    An interannual link between Arctic sea-ice cover and the North Atlantic Oscillation (vol 50, pg 423, 2017)2018In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, no 1-2, p. 443-443Article in journal (Refereed)
  • 9.
    Caron, Louis-Philippe
    et al.
    SMHI, Research Department, Climate research - Rossby Centre. Climate Forecasting Unit, Institut Cátála de Ciènces del clima (IC3).
    Boudreault, Mathieu
    Bruyere, Cindy L.
    Changes in large-scale controls of Atlantic tropical cyclone activity with the phases of the Atlantic multidecadal oscillation2015In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 44, no 7-8, p. 1801-1821Article in journal (Refereed)
    Abstract [en]

    Atlantic tropical cyclone activity is known to oscillate between multi-annual periods of high and low activity. These changes have been linked to the Atlantic multidecadal oscillation (AMO), a mode of variability in Atlantic sea surface temperature which modifies the large-scale conditions of the tropical Atlantic. Cyclone activity is also modulated at higher frequencies by a series of other climate factors, with some of these influences appearing to be more consistent than others. Using the HURDAT2 database and a second set of tropical cyclone data corrected for possible missing storms in the earlier part of the record, we investigate, through Poisson regressions, the relationship between a series of climate variables and a series of metrics of seasonal Atlantic cyclone activity during both phases of the AMO. We find that, while some influences, such as El Nino Southern oscillation, remain present regardless of the AMO phase, other climate factors show an influence during only one of the two phases. During the negative phase, Sahel precipitation and the North Atlantic oscillation (NAO) are measured to play a role, while during the positive phase, the 11-year solar cycle and dust concentration over the Atlantic appear to be more important. Furthermore, we show that during the negative phase of the AMO, the NAO influences all our measures of tropical cyclone activity, and we go on to provide evidence that this is not simply due to changes in steering current, the mechanism by which the NAO is usually understood to impact Atlantic cyclone activity. Finally, we conclude by demonstrating that our results are robust to the sample size as well as to the choice of the statistical model.

  • 10. Caron, Louis-Philippe
    et al.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Understanding and simulating the link between African easterly waves and Atlantic tropical cyclones using a regional climate model: the role of domain size and lateral boundary conditions2012In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, no 1-2, p. 113-135Article in journal (Refereed)
    Abstract [en]

    Using a suite of lateral boundary conditions, we investigate the impact of domain size and boundary conditions on the Atlantic tropical cyclone and african easterly Wave activity simulated by a regional climate model. Irrespective of boundary conditions, simulations closest to observed climatology are obtained using a domain covering both the entire tropical Atlantic and northern African region. There is a clear degradation when the high-resolution model domain is diminished to cover only part of the African continent or only the tropical Atlantic. This is found to be the result of biases in the boundary data, which for the smaller domains, have a large impact on TC activity. In this series of simulations, the large-scale Atlantic atmospheric environment appears to be the primary control on simulated TC activity. Weaker wave activity is usually accompanied by a shift in cyclogenesis location, from the MDR to the subtropics. All ERA40-driven integrations manage to capture the observed interannual variability and to reproduce most of the upward trend in tropical cyclone activity observed during that period. When driven by low-resolution global climate model (GCM) integrations, the regional climate model captures interannual variability (albeit with lower correlation coefficients) only if tropical cyclones form in sufficient numbers in the main development region. However, all GCM-driven integrations fail to capture the upward trend in Atlantic tropical cyclone activity. In most integrations, variations in Atlantic tropical cyclone activity appear uncorrelated with variations in African easterly wave activity.

  • 11. Caron, Louis-Philippe
    et al.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Doblas-Reyes, Francisco
    Multi-year prediction skill of Atlantic hurricane activity in CMIP5 decadal hindcasts2014In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 42, no 9-10, p. 2675-2690Article in journal (Refereed)
    Abstract [en]

    Using a statistical relationship between simulated sea surface temperature and Atlantic hurricane activity, we estimate the skill of a CMIP5 multi-model ensemble at predicting multi-annual level of Atlantic hurricane activity. The series of yearly-initialized hindcasts show positive skill compared to simpler forecasts such as persistence and climatology as well as non-initialized forecasts and return anomaly correlation coefficients of similar to 0.6 and similar to 0.8 for five and nine year forecasts, respectively. Some skill is shown to remain in the later years and making use of those later years to create a lagged-ensemble yields, for individual models, results that approach that obtained by the multi-model ensemble. Some of the skill is shown to come from persisting rather than predicting the climate shift that occur in 1994-1995. After accounting for that shift, the anomaly correlation coefficient for five-year forecasts is estimated to drop to 0.4, but remains statistically significant up to lead years 3-7. Most of the skill is shown to come from the ability of the forecast systems at capturing change in Atlantic sea surface temperature, although the failure of most systems at reproducing the observed slow down in warming over the tropics in recent years leads to an underestimation of hurricane activity in the later period.

  • 12.
    Caron, Louis-Philippe
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Vaillancourt, Paul A.
    Winger, Katja
    On the relationship between cloud-radiation interaction, atmospheric stability and Atlantic tropical cyclones in a variable-resolution climate model2013In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 40, no 5-6, p. 1257-1269Article in journal (Refereed)
    Abstract [en]

    We compare two 28-year simulations performed with two versions of the Global Environmental Multiscale model run in variable-resolution mode. The two versions differ only by small differences in their radiation scheme. The most significant modification introduced is a reduction in the ice effective radius, which is observed to increase absorption of upwelling infrared radiation and increase temperature in the upper troposphere. The resulting change in vertical lapse rate is then observed to drive a resolution-dependent response of convection, which in turn modifies the zonal circulation and induces significant changes in simulated Atlantic tropical cyclone activity. The resulting change in vertical lapse rate and its implication in the context of anthropogenic climate change are discussed.

  • 13.
    Caron, Louis-Philippe
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Winger, Katja
    Impact of resolution and downscaling technique in simulating recent Atlantic tropical cylone activity2011In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 37, no 5-6, p. 869-892Article in journal (Refereed)
    Abstract [en]

    Using the global environmental multiscale (GEM) model, we investigate the impact of increasing model resolution from 2A degrees to 0.3A degrees on Atlantic tropical cyclone activity. There is a clear improvement in the realism of Atlantic storms with increased resolution, in part, linked to a better representation of African easterly waves. The geographical distribution of a Genesis Potential Index, composed of large-scales fields known to impact cyclone formation, coincides closely in the model with areas of high cyclogenesis. The geographical distribution of this index also improves with resolution. We then compare two techniques for achieving local high resolution over the tropical Atlantic: a limited-area model driven at the boundaries by the global 2A degrees GEM simulation and a global variable resolution model (GVAR). The limited-area domain and high-resolution part of the GVAR model coincide geographically, allowing a direct comparison between these two downscaling options. These integrations are further compared with a set of limited-area simulations employing the same domain and resolution, but driven at the boundaries by reanalysis. The limited-area model driven by reanalysis produces the most realistic Atlantic tropical cyclone variability. The GVAR simulation is clearly more accurate than the limited-area version driven by GEM-Global. Degradation in the simulated interannual variability is partly linked to the models failure to accurately reproduce the impact of atmospheric teleconnections from the equatorial Pacific and Sahel on Atlantic cyclogenesis. Through the use of a smaller limited-area grid, driven by GEM-Global 2A degrees, we show that an accurate representation of African Easterly Waves is crucial for simulating Atlantic tropical cyclone variability.

  • 14. Carril, A. F.
    et al.
    Menendez, C. G.
    Remedio, A. R. C.
    Robledo, F.
    Soerensson, A.
    Tencer, B.
    Boulanger, J. -P
    de Castro, M.
    Jacob, D.
    Le Treut, H.
    Li, L. Z. X.
    Penalba, O.
    Pfeifer, S.
    Rusticucci, M.
    Salio, P.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Sanchez, E.
    Zaninelli, P.
    Performance of a multi-RCM ensemble for South Eastern South America2012In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, no 12, p. 2747-2768Article in journal (Refereed)
    Abstract [en]

    The ability of four regional climate models to reproduce the present-day South American climate is examined with emphasis on La Plata Basin. Models were integrated for the period 1991-2000 with initial and lateral boundary conditions from ERA-40 Reanalysis. The ensemble sea level pressure, maximum and minimum temperatures and precipitation are evaluated in terms of seasonal means and extreme indices based on a percentile approach. Dispersion among the individual models and uncertainties when comparing the ensemble mean with different climatologies are also discussed. The ensemble mean is warmer than the observations in South Eastern South America (SESA), especially for minimum winter temperatures with errors increasing in magnitude towards the tails of the distributions. The ensemble mean reproduces the broad spatial pattern of precipitation, but overestimates the convective precipitation in the tropics and the orographic precipitation along the Andes and over the Brazilian Highlands, and underestimates the precipitation near the monsoon core region. The models overestimate the number of wet days and underestimate the daily intensity of rainfall for both seasons suggesting a premature triggering of convection. The skill of models to simulate the intensity of convective precipitation in summer in SESA and the variability associated with heavy precipitation events (the upper quartile daily precipitation) is far from satisfactory. Owing to the sparseness of the observing network, ensemble and observations uncertainties in seasonal means are comparable for some regions and seasons.

  • 15. Casanueva, A.
    et al.
    Kotlarski, S.
    Herrera, S.
    Fernandez, J.
    Gutierrez, J. M.
    Boberg, F.
    Colette, A.
    Christensen, O. B.
    Goergen, K.
    Jacob, D.
    Keuler, K.
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Teichmann, C.
    Vautard, R.
    Daily precipitation statistics in a EURO-CORDEX RCM ensemble: added value of raw and bias-corrected high-resolution simulations2016In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 47, no 3-4, p. 719-737Article in journal (Refereed)
  • 16. Deque, M
    et al.
    Jones, R G
    Wild, M
    Giorgi, F
    Christensen, J H
    Hassell, D C
    Vidale, P L
    Rockel, B
    Jacob, D
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    de Castro, M
    Kucharski, F
    van den Hurk, B
    Global high resolution versus Limited Area Model climate change projections over Europe: quantifying confidence level from PRUDENCE results2005In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 25, no 6, p. 653-670Article in journal (Refereed)
    Abstract [en]

    Four high resolution atmospheric general circulation models (GCMs) have been integrated with the standard forcings of the PRUDENCE experiment: IPCC-SRES A2 radiative forcing and Hadley Centre sea surface temperature and sea-ice extent. The response over Europe, calculated as the difference between the 2071-2100 and the 1961-1990 means is compared with the same diagnostic obtained with nine Regional Climate Models (RCM) all driven by the Hadley Centre atmospheric GCM. The seasonal mean response for 2m temperature and precipitation is investigated. For temperature, GCMs and RCMs behave similarly, except that GCMs exhibit a larger spread. However, during summer, the spread of the RCMs-in particular in terms of precipitation-is larger than that of the GCMs. This indicates that the European summer climate is strongly controlled by parameterized physics and/or high-resolution processes. The temperature response is larger than the systematic error. The situation is different for precipitation. The model bias is twice as large as the climate response. The confidence in PRUDENCE results comes from the fact that the models have a similar response to the IPCC-SRES A2 forcing, whereas their systematic errors are more spread. In addition, GCM precipitation response is slightly but significantly different from that of the RCMs.

  • 17.
    Doescher, Ralf
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Qian, Minwei
    Redler, Ren
    Quantifying Arctic contributions to climate predictability in a regional coupled ocean-ice-atmosphere model2010In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 34, no 7-8, p. 1157-1176Article in journal (Refereed)
    Abstract [en]

    The relative importance of regional processes inside the Arctic climate system and the large scale atmospheric circulation for Arctic interannual climate variability has been estimated with the help of a regional Arctic coupled ocean-ice-atmosphere model. The study focuses on sea ice and surface climate during the 1980s and 1990s. Simulations agree reasonably well with observations. Correlations between the winter North Atlantic Oscillation index and the summer Arctic sea ice thickness and summer sea ice extent are found. Spread of sea ice extent within an ensemble of model runs can be associated with a surface pressure gradient between the Nordic Seas and the Kara Sea. Trends in the sea ice thickness field are widely significant and can formally be attributed to large scale forcing outside the Arctic model domain. Concerning predictability, results indicate that the variability generated by the external forcing is more important in most regions than the internally generated variability. However, both are in the same order of magnitude. Local areas such as the Northern Greenland coast together with Fram Straits and parts of the Greenland Sea show a strong importance of internally generated variability, which is associated with wind direction variability due to interaction with atmospheric dynamics on the Greenland ice sheet. High predictability of sea ice extent is supported by north-easterly winds from the Arctic Ocean to Scandinavia.

  • 18. Endris, Hussen Seid
    et al.
    Lennard, Christopher
    Hewitson, Bruce
    Dosio, Alessandro
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Panitz, Hans-Juergen
    Teleconnection responses in multi-GCM driven CORDEX RCMs over Eastern Africa2016In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 46, no 9-10, p. 2821-2846Article in journal (Refereed)
  • 19. Favre, Alice
    et al.
    Philippon, Nathalie
    Pohl, Benjamin
    Kalognomou, Evangelia-Anna
    Lennard, Christopher
    Hewitson, Bruce
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Dosio, Alessandro
    Panitz, Hans-Juergen
    Cerezo-Mota, Ruth
    Spatial distribution of precipitation annual cycles over South Africa in 10 CORDEX regional climate model present-day simulations2016In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 46, no 5-6, p. 1799-1818Article in journal (Refereed)
    Abstract [en]

    This study presents an evaluation of the ability of 10 regional climate models (RCMs) participating in the COordinated Regional climate Downscaling Experiment-Africa to reproduce the present-day spatial distribution of annual cycles of precipitation over the South African region and its borders. As found in previous studies, annual mean precipitation is quasi-systematically overestimated by the RCMs over a large part of southern Africa south of about 20A degrees S and more strongly over South Africa. The spatial analysis of precipitation over the studied region shows that in most models the distribution of biases appears to be linked to orography. Wet biases are quasi-systematic in regions with higher elevation with inversely neutral to dry biases particularly in the coastal fringes. This spatial pattern of biases is particularly obvious during summer and specifically at the beginning of the rainy season (November and December) when the wet biases are found to be the strongest across all models. Applying a k-means algorithm, a classification of annual cycles is performed using observed precipitation data, and is compared with those derived from modeled data. It is found that the in-homogeneity of the spatial and temporal distribution of biases tends to impact the modeled seasonality of precipitation. Generally, the pattern of rainfall seasonality in the ensemble mean of the 10 RCMs tends to be shifted to the southwest. This spatial shift is mainly linked to a strong overestimation of convective precipitation at the beginning of the rainy season over the plateau inducing an early annual peak and to an underestimation of stratiform rainfall in winter and spring over southwestern South Africa.

  • 20. Fosser, G.
    et al.
    Khodayar, S.
    Berg, Peter
    SMHI, Research Department, Hydrology.
    Benefit of convection permitting climate model simulations in the representation of convective precipitation2015In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 44, no 1-2, p. 45-60Article in journal (Refereed)
    Abstract [en]

    A major source of uncertainty in regional climate model (RCM) simulations arises from the parameterisation of sub-grid scale convection. With increasing model resolution, approaching the so-called convection permitting scale, it is possible to switch off most of the convection parameterisations. A set of simulations using COSMO-CLM model has been carried out at different resolutions in order to investigate possible improvements and limitations resulting from increased horizontal resolution. For our analysis, 30 years were simulated in a triple nesting setup with 50, 7 and 2.8 km resolutions, with ERA40 reanalysis data at the lateral boundaries of the coarsest nest. The investigation area covers the state of Baden-Wurttemberg in southwestern Germany, which is a region known for abundant orographically induced convective precipitation. A very dense network of high temporal resolution rain gauges is used for evaluation of the model simulations. The purpose of this study is to examine the differences between the 7 and 2.8 km resolutions in the representation of precipitation at sub-daily timescales, and the atmospheric conditions leading to convection. Our results show that the highest resolution of RCM simulations significantly improves the representation of both hourly intensity distribution and diurnal cycle of precipitation. In addition, at convection permitting scale the atmospheric fields related to convective precipitation show a better agreement with each other. The results imply that higher spatial resolution partially improves the representation of the precipitation field, which must be the way forward for regional climate modelling.

  • 21. Fosser, G.
    et al.
    Khodayar, S.
    Berg, Peter
    SMHI, Research Department, Hydrology.
    Climate change in the next 30 years: What can a convection-permitting model tell us that we did not already know?2017In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 48, no 5-6, p. 1987-2003Article in journal (Refereed)
  • 22. Hazeleger, W.
    et al.
    Wang, X.
    Severijns, C.
    Stefanescu, S.
    Bintanja, R.
    Sterl, A.
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Semmler, T.
    Yang, S.
    van den Hurk, B.
    van Noije, T.
    van der Linden, E.
    van der Wiel, K.
    EC-Earth V2.2: description and validation of a new seamless earth system prediction model2012In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, no 11, p. 2611-2629Article in journal (Refereed)
    Abstract [en]

    EC-Earth, a new Earth system model based on the operational seasonal forecast system of the European Centre for Medium-Range Weather Forecasts (ECMWF), is presented. The performance of version 2.2 (V2.2) of the model is compared to observations, reanalysis data and other coupled atmosphere-ocean-sea ice models. The large-scale physical characteristics of the atmosphere, ocean and sea ice are well simulated. When compared to other coupled models with similar complexity, the model performs well in simulating tropospheric fields and dynamic variables, and performs less in simulating surface temperature and fluxes. The surface temperatures are too cold, with the exception of the Southern Ocean region and parts of the Northern Hemisphere extratropics. The main patterns of interannual climate variability are well represented. Experiments with enhanced CO2 concentrations show well-known responses of Arctic amplification, land-sea contrasts, tropospheric warming and stratospheric cooling. The global climate sensitivity of the current version of EC-Earth is slightly less than 1 K/(W m(-2)). An intensification of the hydrological cycle is found and strong regional changes in precipitation, affecting monsoon characteristics. The results show that a coupled model based on an operational seasonal prediction system can be used for climate studies, supporting emerging seamless prediction strategies.

  • 23. Ho-Hagemann, Ha Thi Minh
    et al.
    Groger, Matthias
    SMHI, Research Department, Oceanography.
    Rockel, Burkhardt
    Zahn, Matthias
    Geyer, Beate
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Effects of air-sea coupling over the North Sea and the Baltic Sea on simulated summer precipitation over Central Europe2017In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 49, no 11-12, p. 3851-3876Article in journal (Refereed)
  • 24.
    Hordoir, Robinson
    et al.
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Sensitivity of the overturning circulation of the Baltic Sea to climate change, a numerical experiment2018In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, no 3-4, p. 1425-1437Article in journal (Refereed)
  • 25.
    Hordoir, Robinson
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Effect of climate change on the thermal stratification of the baltic sea: a sensitivity experiment2012In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 38, no 9-10, p. 1703-1713Article in journal (Refereed)
    Abstract [en]

    The evolution in time of the thermal vertical stratification of the Baltic Sea in future climate is studied using a 3D ocean model. Comparing periods at the end of the twentieth and twenty first centuries we found a strong increase in stratification at the bottom of the mixed layer in the northern Baltic Sea. In order to understand the causes of this increase, a sensitivity analysis is performed. We found that the increased vertical stratification is explained by a major change in re-stratification during spring solely caused by the increase of the mean temperature. As in present climate winter temperatures in the Baltic are often below the temperature of maximum density, warming causes thermal convection. Re-stratification during the beginning of spring is then triggered by the spreading of freshwater. This process is believed to be important for the onset of the spring bloom. In future climate, temperatures are expected to be usually higher than the temperature of maximum density and thermally induced stratification will start without prior thermal convection. Thus, freshwater controlled re-stratification during spring is not an important process anymore. We employed a simple box model and used sensitivity experiments with the 3D ocean model to delineate the processes involved and to quantify the impact of changing freshwater supply on the thermal stratification in the Baltic Sea. It is suggested that these stratification changes may have an important impact on vertical nutrient fluxes and the intensity of the spring bloom in future climate of the Baltic Sea.

  • 26. Jungclaus, Johann H.
    et al.
    Koenigk, Torben
    SMHI, Research Department, Climate research - Rossby Centre.
    Low-frequency variability of the arctic climate: the role of oceanic and atmospheric heat transport variations2010In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 34, no 2-3, p. 265-279Article in journal (Refereed)
  • 27.
    Koenigk, Torben
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Beatty, Christof Konig
    Caian, Mihaela
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Potential decadal predictability and its sensitivity to sea ice albedo parameterization in a global coupled model2012In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 38, no 11-12, p. 2389-2408Article in journal (Refereed)
    Abstract [en]

    Decadal prediction is one focus of the upcoming 5th IPCC Assessment report. To be able to interpret the results and to further improve the decadal predictions it is important to investigate the potential predictability in the participating climate models. This study analyzes the upper limit of climate predictability on decadal time scales and its dependency on sea ice albedo parameterization by performing two perfect ensemble experiments with the global coupled climate model EC-Earth. In the first experiment, the standard albedo formulation of EC-Earth is used, in the second experiment sea ice albedo is reduced. The potential prognostic predictability is analyzed for a set of oceanic and atmospheric parameters. The decadal predictability of the atmospheric circulation is small. The highest potential predictability was found in air temperature at 2 m height over the northern North Atlantic and the southern South Atlantic. Over land, only a few areas are significantly predictable. The predictability for continental size averages of air temperature is relatively good in all northern hemisphere regions. Sea ice thickness is highly predictable along the ice edges in the North Atlantic Arctic Sector. The meridional overturning circulation is highly predictable in both experiments and governs most of the decadal climate predictability in the northern hemisphere. The experiments using reduced sea ice albedo show some important differences like a generally higher predictability of atmospheric variables in the Arctic or higher predictability of air temperature in Europe. Furthermore, decadal variations are substantially smaller in the simulations with reduced ice albedo, which can be explained by reduced sea ice thickness in these simulations.

  • 28.
    Koenigk, Torben
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Brodeau, Laurent
    Arctic climate and its interaction with lower latitudes under different levels of anthropogenic warming in a global coupled climate model2017In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 49, no 1-2, p. 471-492Article in journal (Refereed)
  • 29.
    Koenigk, Torben
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Brodeau, Laurent
    Ocean heat transport into the Arctic in the twentieth and twenty-first century in EC-Earth2014In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 42, no 11-12, p. 3101-3120Article in journal (Refereed)
    Abstract [en]

    The ocean heat transport into the Arctic and the heat budget of the Barents Sea are analyzed in an ensemble of historical and future climate simulations performed with the global coupled climate model EC-Earth. The zonally integrated northward heat flux in the ocean at 70A degrees N is strongly enhanced and compensates for a reduction of its atmospheric counterpart in the twenty first century. Although an increase in the northward heat transport occurs through all of Fram Strait, Canadian Archipelago, Bering Strait and Barents Sea Opening, it is the latter which dominates the increase in ocean heat transport into the Arctic. Increased temperature of the northward transported Atlantic water masses are the main reason for the enhancement of the ocean heat transport. The natural variability in the heat transport into the Barents Sea is caused to the same extent by variations in temperature and volume transport. Large ocean heat transports lead to reduced ice and higher atmospheric temperature in the Barents Sea area and are related to the positive phase of the North Atlantic Oscillation. The net ocean heat transport into the Barents Sea grows until about year 2050. Thereafter, both heat and volume fluxes out of the Barents Sea through the section between Franz Josef Land and Novaya Zemlya are strongly enhanced and compensate for all further increase in the inflow through the Barents Sea Opening. Most of the heat transported by the ocean into the Barents Sea is passed to the atmosphere and contributes to warming of the atmosphere and Arctic temperature amplification. Latent and sensible heat fluxes are enhanced. Net surface long-wave and solar radiation are enhanced upward and downward, respectively and are almost compensating each other. We find that the changes in the surface heat fluxes are mainly caused by the vanishing sea ice in the twenty first century. The increasing ocean heat transport leads to enhanced bottom ice melt and to an extension of the area with bottom ice melt further northward. However, no indication for a substantial impact of the increased heat transport on ice melt in the Central Arctic is found. Most of the heat that is not passed to the atmosphere in the Barents Sea is stored in the Arctic intermediate layer of Atlantic water, which is increasingly pronounced in the twenty first century.

  • 30.
    Koenigk, Torben
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Brodeau, Laurent
    Graversen, Rune Grand
    Karlsson, Johannes
    Svensson, Gunilla
    Tjernstrom, Michael
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Arctic climate change in 21st century CMIP5 simulations with EC-Earth2013In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 40, no 11-12, p. 2719-2743Article in journal (Refereed)
    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.

  • 31.
    Koenigk, Torben
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Caian, Mihaela
    SMHI, Research Department, Climate research - Rossby Centre.
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Regional Arctic sea ice variations as predictor for winter climate conditions2016In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 46, no 1-2, p. 317-337Article in journal (Refereed)
    Abstract [en]

    Seasonal prediction skill of winter mid and high northern latitudes climate from sea ice variations in eight different Arctic regions is analyzed using detrended ERA-interim data and satellite sea ice data for the period 1980-2013. We find significant correlations between ice areas in both September and November and winter sea level pressure, air temperature and precipitation. The prediction skill is improved when using November sea ice conditions as predictor compared to September. This is particularly true for predicting winter NAO-like patterns and blocking situations in the Euro-Atlantic area. We find that sea ice variations in Barents Sea seem to be most important for the sign of the following winter NAO-negative after low ice-but amplitude and extension of the patterns are modulated by Greenland and Labrador Seas ice areas. November ice variability in the Greenland Sea provides the best prediction skill for central and western European temperature and ice variations in the Laptev/East Siberian Seas have the largest impact on the blocking number in the Euro-Atlantic region. Over North America, prediction skill is largest using September ice areas from the Pacific Arctic sector as predictor. Composite analyses of high and low regional autumn ice conditions reveal that the atmospheric response is not entirely linear suggesting changing predictive skill dependent on sign and amplitude of the anomaly. The results confirm the importance of realistic sea ice initial conditions for seasonal forecasts. However, correlations do seldom exceed 0.6 indicating that Arctic sea ice variations can only explain a part of winter climate variations in northern mid and high latitudes.

  • 32.
    Koenigk, Torben
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Mikolajewicz, Uwe
    Seasonal to interannual climate predictability in mid and high northern latitudes in a global coupled model2009In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 32, no 6, p. 783-798Article in journal (Refereed)
  • 33.
    Koenigk, Torben
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Mikolajewicz, Uwe
    Jungclaus, Johann H.
    Kroll, Alexandra
    Sea ice in the Barents Sea: seasonal to interannual variability and climate feedbacks in a global coupled model2009In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 32, no 7-8, p. 1119-1138Article in journal (Refereed)
  • 34. Krueger, Oliver
    et al.
    Feser, Frauke
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Kaas, Eigil
    Schmith, Torben
    Tuomenvirta, Heikki
    von Storch, Hans
    Comment on "Trends and low frequency variability of extra-tropical cyclone activity in the ensemble of twentieth century reanalysis" by Xiaolan L. Wang, Y. Feng, G. P. Compo, V. R. Swail, F. W. Zwiers, R. J. Allan, and P. D. Sardeshmukh, Climate Dynamics, 20122014In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 42, no 3-4, p. 1127-1128Article in journal (Other academic)
    Abstract [en]

    The main subject of this article is to comment on the issue of storminess trends derived from the twentieth century reanalysis (20CR) and from observations in the North Atlantic region written about in Wang et al. (Clim Dyn 40(11-12):2775-2800, 2012). The statement that the 20CR estimates would be consistent with storminess derived from pressure-based proxies does not hold for the time prior to 1950.

  • 35. Lewinschal, Anna
    et al.
    Ekman, Annica M. L.
    Körnich, Heiner
    SMHI, Research Department, Meteorology.
    The role of precipitation in aerosol-induced changes in northern hemisphere wintertime stationary waves2013In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 41, no 3-4, p. 647-661Article in journal (Refereed)
    Abstract [en]

    The coupled climate model EC-Earth2 is used to investigate the impact of direct radiative effects of aerosols on stationary waves in the northern hemisphere wintertime circulation. The direct effect of aerosols is simulated by introducing prescribed mixing ratios of different aerosol compounds representing pre-industrial and present-day conditions, no indirect effects are included. In the EC-Earth2 results, the surface temperature response is uncorrelated with the highly asymmetric aerosol radiative forcing pattern. Instead, the anomalous extratropical temperature field bears a strong resemblance to the aerosol-induced changes in the stationary-wave pattern. It is demonstrated that the main features of the wave pattern of EC-Earth2 can be replicated by a linear, baroclinic model forced with latent heat changes corresponding to the anomalous convective precipitation generated by EC-Earth2. The tropical latent heat release is an effective means of generating stationary wave trains that propagate into the extratropics. Hence, the results of the present study indicate that aerosol-induced convective precipitation anomalies govern the extratropical wave-field changes, and that the far-field temperature response dominates over local effects of aerosol radiative forcing.

  • 36.
    Lucas-Picher, Philippe
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Somot, Samuel
    Deque, Michel
    Decharme, Bertrand
    Alias, Antoinette
    Evaluation of the regional climate model ALADIN to simulate the climate over North America in the CORDEX framework2013In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 41, no 5-6, p. 1117-1137Article in journal (Refereed)
    Abstract [en]

    In this study, an ensemble of four multi-year climate simulations is performed with the regional climate model ALADIN to evaluate its ability to simulate the climate over North America in the CORDEX framework. The simulations differ in their driving fields (ERA-40 or ERA-Interim) and the nudging technique (with or without large-scale nudging). The validation of the simulated 2-m temperature and precipitation with observationally-based gridded data sets shows that ALADIN performs similarly to other regional climate models that are commonly used over North America. Large-scale nudging improves the temporal correlation of the atmospheric circulation between ALADIN and its driving field, and also reduces the warm and dry summer biases in central North America. The differences between the simulations driven with different reanalyses are small and are likely related to the regional climate model's induced internal variability. In general, the impact of different driving fields on ALADIN is smaller than that of large-scale nudging. The analysis of the multi-year simulations over the prairie and the east taiga indicates that the ALADIN 2-m temperature and precipitation interannual variability is similar or larger than that observed. Finally, a comparison of the simulations with observations for the summer 1993 shows that ALADIN underestimates the flood in central North America mainly due to its systematic dry bias in this region. Overall, the results indicate that ALADIN can produce a valuable contribution to CORDEX over North America.

  • 37. Marengo, J.
    et al.
    Chou, S.
    Mourao, C.
    Solman, S.
    Sanchez, E.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    da Rocha, R. P.
    Li, L.
    Pessacg, N.
    Remedio, A. R. C.
    Carril, A. F.
    Cavalcanti, I. F.
    Jacob, D.
    Simulation of rainfall anomalies leading to the 2005 drought in Amazonia using the CLARIS LPB regional climate models2013In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 41, no 11-12, p. 2937-2955Article in journal (Refereed)
    Abstract [en]

    The meteorological characteristics of the drought of 2005 in Amazonia, one of the most severe in the last 100 years were assessed using a suite of seven regional models obtained from the CLARIS LPB project. The models were forced with the ERA-Interim reanalyses as boundary conditions. We used a combination of rainfall and temperature observations and the low-level circulation and evaporation fields from the reanalyses to determine the climatic and meteorological characteristics of this particular drought. The models reproduce in some degree the observed annual cycle of precipitation and the geographical distribution of negative rainfall anomalies during the summer months of 2005. With respect to the evolution of rainfall during 2004-2006, some of the models were able to simulate the negative rainfall departures during early summer of 2005 (December 2004 to February 2005). The interannual variability of rainfall anomalies for both austral summer and fall over northern and southern Amazonia show a large spread among models, with some of them capable of reproducing the 2005 observed negative rainfall departures (four out of seven models in southern Amazonia during DJF). In comparison, all models simulated the observed southern Amazonia negative rainfall and positive air temperature anomalies during the El Nino-related drought in 1998. The spatial structure of the simulated rainfall and temperature anomalies in DJF and MAM 2005 shows biases that are different among models. While some models simulated the observed negative rainfall anomalies over parts of western and southern Amazonia during DJF, others simulated positive rainfall departures over central Amazonia. The simulated circulation patterns indicate a weaker northeasterly flow from the tropical North Atlantic into Amazonia, and reduced flows from southern Amazonia into the La Plata basin in DJF, which is consistent with observations. In general, we can say that in some degree the regional models are able to capture the response to the forcing from the tropical Atlantic during the drought of 2005 in Amazonia. Moreover, extreme climatic conditions in response to anomalous low-level circulation features are also well captured, since the boundary conditions come from reanalysis and the models are largely constrained by the information provided at the boundaries. The analysis of the 2005 drought suggests that when the forcing leading to extreme anomalous conditions is associated with both local and non-local mechanisms (soil moisture feedbacks and remote SST anomalies, respectively) the models are not fully capable of representing these feedbacks and hence, the associated anomalies. The reason may be a deficient reproduction of the land-atmosphere interactions.

  • 38. Markovic, Marko
    et al.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Vaillancourt, Paul A.
    Paquin, Dominique
    Winger, Katja
    Paquin-Ricard, Danahe
    An evaluation of the surface radiation budget over North America for a suite of regional climate models against surface station observations2008In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 31, no 7-8, p. 779-794Article in journal (Refereed)
  • 39. Matulla, C.
    et al.
    Schoener, W.
    Alexandersson, Hans
    SMHI.
    von Storch, H.
    Wang, X. L.
    European storminess: late nineteenth century to present2008In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 31, no 2-3, p. 125-130Article in journal (Refereed)
    Abstract [en]

    Annual and seasonal statistics of local air pressure characteristics have already been used as proxies for storminess across Northern Europe. We present an update of such proxies for Northern Europe and an unprecedented analysis for Central Europe which together considerably extends the current knowledge of European storminess. Calculations are completed for three sets of stations, located in North-Western, Northern and Central Europe. Results derived from spatial differences (geostrophic winds) and single station pressure changes per 24 h support each other. Geostrophic winds' high percentiles (95th, 99th) were relatively high during the late nineteenth and the early twentieth century; after that they leveled off somewhat, to get larger again in the late twentieth century. The decrease happens suddenly in Central Europe and over several decades in Northern Europe. The subsequent rise is most pronounced in North-Western Europe, while slow and steady in Central Europe. Europe's storm climate has undergone significant changes throughout the past 130 years and comprises significant variations on a quasi-decadal timescale. Most recent years feature average or calm conditions, supporting claims raised in earlier studies with new evidence. Aside from some dissimilarity, a general agreement between the investigated regions appears to be the most prominent feature. The capability of the NAO index to explain storminess across Europe varies in space and with the considered period.

  • 40.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Baltic Sea climate in the late twenty-first century: a dynamical donwscaling approach using two global models and two emission scenarios2006In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 1, no 27, p. 39-68Article in journal (Refereed)
  • 41.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Baltic Sea climate in the late twenty-first century: a dynamical downscaling approach using two global models and two emission scenarios2006In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 27, no 1, p. 39-68Article in journal (Refereed)
    Abstract [en]

    A regional ocean circulation model was used to project Baltic Sea climate at the end of the twenty-first century. A set of four scenario simulations was performed utilizing two global models and two forcing scenarios. To reduce model biases and to spin up future salinity the so-called Delta-change approach was applied. Using a regional coupled atmosphere-ocean model 30-year climatological monthly mean changes of atmospheric surface data and river discharge into the Baltic Sea were calculated from previously conducted time slice experiments. These changes were added to reconstructed atmospheric surface fields and runoff for the period 1903-1998. The total freshwater supply (runoff and net precipitation) is projected to increase between 0 and 21%. Due to increased westerlies in winter the annual mean wind speed will be between 2 and 13% larger compared to present climate. Both changes will cause a reduction of the average salinity of the Baltic Sea between 8 and 50%. Although salinity in the entire Baltic might be significantly lower at the end of the twenty-first century, deep water ventilation will very likely only slightly change. The largest change is projected for the secondary maximum of sea water age within the halocline. Further, the average temperature will increase between 1.9 and 3.2 degrees C. The temperature response to atmospheric changes lags several months. Future annual maximum sea ice extent will decrease between 46 and 77% in accordance to earlier studies. However, in contrast to earlier results in the warmest scenario simulation one ice-free winter out of 96 seasons was found. Although wind speed changes are uniform, extreme sea levels may increase more than the mean sea level. In two out of four projections significant changes of 100-year surge heights were found.

  • 42.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Regional ocean climate simulations with a 3D ice-ocean model for the Baltic Sea. Part 1: model experiments and results for temperature and salinity2002In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 19, no 3-4, p. 237-253Article in journal (Refereed)
    Abstract [en]

    Sea surface temperatures and salinity profiles in the Baltic Sea have been analyzed under different climate conditions using a 3D coupled ice-ocean model. As a reference, hindcast simulations for the period 1980-93 have been performed using observed three-hourly meteorological forcing fields and observed monthly river runoff. The results are compared with available observations from monitoring stations. The observed Baltic Sea climate is well reproduced by the model. Furthermore, two sets of 9-year time slice experiments have been performed using results from an atmospheric regional climate model as forcing. One of the time slice sets represents pre-industrial greenhouse conditions (control simulation), and the other set represents a global warming condition with a 150% increase in equivalent CO(2) concentrations (scenario simulation) with lateral boundary conditions from the global atmosphere-ocean general circulation model, HadCM2. To simulate river runoff, a large-scale hydrological model has been applied. As the time slices are too short to properly spin up initial stratification for future climate, salinity is treated as an uncertainty factor. An extreme condition is obtained by integrating the Baltic Sea model for a period of 100 years while assuming that no salt water inflow will occur in the future. Salinity in the Gotland Basin decreases in the surface layer by about 3 to 4 psu and in the bottom layer by about 6 to 6.5 psu. The final quasi-equilibrium is characterized by salinities of 2.8 psu (minimum at the surface) to 6.5 psu (maximum at the bottom). The area averaged annual mean sea surface temperature change between scenario and control run is about 2.3 degreesC. The warming in different seasons is almost the same. The computational effective time slice approach in dynamical downscaling experiments is regarded as a feasible technique to regionalize global climate change experiments in the Baltic Sea.

  • 43.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Regional ocean climate simulations with a 3D ice-ocean model for the Baltic Sea. Part 2: results for sea ice2002In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 19, no 3-4, p. 255-266Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea ice season under changing climate conditions is investigated using a 3D coupled ice-ocean model. Results of multi-year simulations for the period of May 1980 to December 1993 are compared with observations from monitoring stations, ice charts and satellite data. The period 1980-1993 has been selected mainly because of the availability of homogeneous observational data sets for atmospheric variables and river runoff with sufficient quality to force a 3D high resolution Baltic Sea model. The observed seasonal variation of sea ice is well reproduced by the model. Furthermore, two sets of 9-year time slice experiments have been performed using results of an atmospheric regional climate model as forcing, one representing pre-industrial greenhouse conditions (control simulation), and the other a global warming with a 150% increase of equivalent CO(2) concentration (scenario simulation). At the lateral boundaries of the regional climate model, results of the global atmosphere-ocean general circulation model HadCM2 have been prescribed. In the control run, the mean seasonal cycle of ice cover and its variability is simulated realistically compared to observations, but the seasonal ice cover maximum is shifted in time by about 18 days and the simulated mean melting date is delayed. Mild winters are missing in the relatively short control run. The decrease of mean ice extent in the scenario, compared to the control run, is dramatic, reducing from 210 . 10(9) m(2) to 82 . 10(9) m(2) (a relative change of 61%). However, in all scenario years, ice is still formed in the northernmost basin of the Baltic Sea, the Bothnian Bay. The minimum ice extent is 16 . 10(9) m(2) (for comparison: the area of the Bothnian Bay is about twice as large). The mean number of ice days decreases significantly. In the fast ice zone of the Bothnian Bay the mean ice season is reduced by 40 days. The ice in the scenario run is thinner with less snow on top. In the central Bothnian Bay, mean maximum annual ice thickness is reduced by 25 cm from 54 to 29 cm. Model dependent uncertainties are discussed.

  • 44.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Gustafsson, B. G.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Modeling the combined impact of changing climate and changing nutrient loads on the Baltic Sea environment in an ensemble of transient simulations for 1961-20992012In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, no 9-10, p. 2421-2441Article in journal (Refereed)
    Abstract [en]

    The combined future impacts of climate change and industrial and agricultural practices in the Baltic Sea catchment on the Baltic Sea ecosystem were assessed. For this purpose 16 transient simulations for 1961-2099 using a coupled physical-biogeochemical model of the Baltic Sea were performed. Four climate scenarios were combined with four nutrient load scenarios ranging from a pessimistic business-as-usual to a more optimistic case following the Baltic Sea Action Plan (BSAP). Annual and seasonal mean changes of climate parameters and ecological quality indicators describing the environmental status of the Baltic Sea like bottom oxygen, nutrient and phytoplankton concentrations and Secchi depths were studied. Assuming present-day nutrient concentrations in the rivers, nutrient loads from land increase during the twenty first century in all investigated scenario simulations due to increased volume flows caused by increased net precipitation in the Baltic catchment area. In addition, remineralization rates increase due to increased water temperatures causing enhanced nutrient flows from the sediments. Cause-and-effect studies suggest that both processes may play an important role for the biogeochemistry of eutrophicated seas in future climate partly counteracting nutrient load reduction efforts like the BSAP.

  • 45.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Almroth-Rosell, Elin
    SMHI, Research Department, Oceanography.
    Impact of accelerated future global mean sea level rise on hypoxia in the Baltic Sea2017In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 49, no 1-2, p. 163-172Article in journal (Refereed)
  • 46. Pessacg, Natalia L.
    et al.
    Solman, Silvina A.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Sanchez, Enrique
    Marengo, Jose
    Li, Laurent
    Remedio, Armelle Reca C.
    da Rocha, Rosmeri P.
    Mourao, Caroline
    Jacob, Daniela
    The surface radiation budget over South America in a set of regional climate models from the CLARIS-LPB project2014In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 43, no 5-6, p. 1221-1239Article in journal (Refereed)
    Abstract [en]

    The performance of seven regional climate models in simulating the radiation and heat fluxes at the surface over South America (SA) is evaluated. Sources of uncertainty and errors are identified. All simulations have been performed in the context of the CLARIS-LPB Project for the period 1990-2008 and are compared with the GEWEX-SRB, CRU, and GLDAS2 dataset and NCEP-NOAA reanalysis. Results showed that most of the models overestimate the net surface short-wave radiation over tropical SA and La Plata Basin and underestimate it over oceanic regions. Errors in the short-wave radiation are mainly associated with uncertainties in the representation of surface albedo and cloud fraction. For the net surface long-wave radiation, model biases are diverse. However, the ensemble mean showed a good agreement with the GEWEX-SRB dataset due to the compensation of individual model biases. Errors in the net surface long-wave radiation can be explained, in a large proportion, by errors in cloud fraction. For some particular models, errors in temperature also contribute to errors in the net long-wave radiation. Analysis of the annual cycle of each component of the energy budget indicates that the RCMs reproduce generally well the main characteristics of the short- and long-wave radiations in terms of timing and amplitude. However, a large spread among models over tropical SA is apparent. The annual cycle of the sensible heat flux showed a strong overestimation in comparison with the reanalysis and GLDAS2 dataset. For the latent heat flux, strong differences between the reanalysis and GLDAS2 are calculated particularly over tropical SA.

  • 47. Prein, A. F.
    et al.
    Gobiet, A.
    Truhetz, H.
    Keuler, K.
    Goergen, K.
    Teichmann, C.
    Maule, C. Fox
    van Meijgaard, E.
    Deque, M.
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Vautard, R.
    Colette, A.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Jacob, D.
    Precipitation in the EURO-CORDEX 0.11 degrees and 0.44 degrees simulations: high resolution, high benefits?2016In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 46, no 1-2, p. 383-412Article in journal (Refereed)
    Abstract [en]

    In the framework of the EURO-CORDEX initiative an ensemble of European-wide high-resolution regional climate simulations on a 0.11 degrees (similar to 12.5 km) grid has been generated. This study investigates whether the fine-gridded regional climate models are found to add value to the simulated mean and extreme daily and sub-daily precipitation compared to their coarser-gridded 0.44 degrees (similar to 50 km) counterparts. Therefore, pairs of fine-and coarse-gridded simulations of eight reanalysis-driven models are compared to fine-gridded observations in the Alps, Germany, Sweden, Norway, France, the Carpathians, and Spain. A clear result is that the 0.11 degrees simulations are found to better reproduce mean and extreme precipitation for almost all regions and seasons, even on the scale of the coarser-gridded simulations (50 km). This is primarily caused by the improved representation of orography in the 0.11 degrees simulations and therefore largest improvements can be found in regions with substantial orographic features. Improvements in reproducing precipitation in the summer season appear also due to the fact that in the fine-gridded simulations the larger scales of convection are captured by the resolved-scale dynamics. The 0.11 degrees simulations reduce biases in large areas of the investigated regions, have an improved representation of spatial precipitation patterns, and precipitation distributions are improved for daily and in particular for 3 hourly precipitation sums in Switzerland. When the evaluation is conducted on the fine (12.5 km) grid, the added value of the 0.11 degrees models becomes even more obvious.

  • 48. Pryor, S. C.
    et al.
    Barthelmie, R. J.
    Clausen, N. E.
    Drews, M.
    MacKellar, N.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Analyses of possible changes in intense and extreme wind speeds over northern Europe under climate change scenarios2012In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 38, no 1-2, p. 189-208Article in journal (Refereed)
    Abstract [en]

    Dynamical downscaling of ECHAM5 using HIRHAM5 and RCA3 for a northern European domain focused on Scandinavia indicates sustained extreme wind speeds with long recurrence intervals (50 years) and intense winds are not likely to evolve out of the historical envelope of variability until the end of C21st. Even then, significant changes are indicated only in the SW of the domain and across the central Baltic Sea where there is some evidence for relatively small magnitude increases in the 50 year return period wind speed (of up to 15%). There are marked differences in results based on the two Regional Climate Models. Additionally, internal (inherent) variability and initial conditions exert a strong impact on projected wind climates throughout the twenty-first century. Simulations of wind gusts by one of the RCMs (RCA3) indicate some evidence for increased magnitudes (of up to +10%) in the southwest of the domain and across the central Baltic Sea by the end of the current century. As in prior downscaling of ECHAM4, dynamical downscaling of ECHAM5 indicates a tendency towards increased energy density and thus wind power generation potential over the course of the C21st. However, caution should be used in interpreting this inference given the high degree of wind climate projection spread that derives from the specific AOGCM and RCM used in the downscaling.

  • 49. Pryor, S C
    et al.
    Barthelmie, R J
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Potential climate change impact on wind energy resources in northern Europe: analyses using a regional climate model2005In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 25, no 7-8, p. 815-835Article in journal (Refereed)
    Abstract [en]

    There is considerable interest in the potential impact of climate change on the feasibility and predictability of renewable energy sources including wind energy. This paper presents dynamically downscaled near-surface wind fields and examines the impact of climate change on near-surface flow and hence wind energy density across northern Europe. It is shown that: Simulated wind fields from the Rossby Centre coupled Regional Climate Model (RCM) (RCAO) with boundary conditions derived from ECHAM4/OPYC3 AOGCM and the HadAM3H atmosphere-only GCM exhibit reasonable and realistic features as documented in reanalysis data products during the control period (1961-1990). The near-surface wind speeds calculated for a climate change projection period of 2071-2100 are higher than during the control run for two IPCC emission scenarios (A2, B2) for simulations conducted using boundary conditions from ECHAM4/OPYC3. The RCAO simulations conducted using boundary conditions from ECHAM4/OPYC3 indicate evidence for a small increase in the annual wind energy resource over northern Europe between the control run and climate change projection period and for more substantial increases in energy density during the winter season. However, the differences between the RCAO simulations for the climate projection period and the control run are of similar magnitude to differences between the RCAO fields in the control period and the NCEP/NCAR reanalysis data. Additionally, the simulations show a high degree of sensitivity to the boundary conditions, and simulations conducted using boundary conditions from HadAM3H exhibit evidence of slight declines or no change in wind speed and energy density between 1961-1990 and 2071-2100. Hence, the uncertainty of the projected wind changes is relatively high.

  • 50. Qian, Minwei
    et al.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Laprise, Rene
    Caya, Daniel
    The Influences of NAO and the Hudson Bay sea-ice on the climate of eastern Canada2008In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 31, no 2-3, p. 169-182Article in journal (Refereed)
12 1 - 50 of 63
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