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  • 451.
    Vedin, Haldo
    SMHI.
    FREQUENCY OF RARE WEATHER EVENTS DURING PERIODS OF EXTREME CLIMATE1990In: Geografiska Annaler. Series A, Physical Geography, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 72, no 2, p. 151-155Article in journal (Refereed)
  • 452.
    Venäläinen, Ari
    et al.
    Finnish Meteorological Institute, Finland.
    Saku, Seppo
    Finnish Meteorological Institute, Finland.
    Jylhä, Kirsti
    Finnish Meteorological Institute, Finland.
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Climate extremes and safety of nuclear power plants: Extreme temperatures and enthalpy in Finland and Sweden in a changing climate.2009Report (Other academic)
  • 453. Voisin, Nathalie
    et al.
    Hamlet, Alan F.
    Graham, Phil
    SMHI, Research Department, Climate research - Rossby Centre.
    Pierce, David W.
    Barnett, Tim P.
    Lettenmaier, Dennis P.
    The role of climate forecasts in Western US power planning2006In: Journal of Applied Meteorology and Climatology, ISSN 1558-8424, E-ISSN 1558-8432, Vol. 45, no 5, p. 653-673Article in journal (Refereed)
    Abstract [en]

    The benefits of potential electric power transfers between the Pacific Northwest (PNW) and California ( CA) are evaluated using a linked set of hydrologic, reservoir, and power demand simulation models for the Columbia River and the Sacramento-San Joaquin reservoir systems. The models provide a framework for evaluating climate-related variations and long-range predictability of regional electric power demand, hydropower production, and the benefits of potential electric power transfers between the PNW and CA. The period of analysis is 1917-2002. The study results show that hydropower production and regional electric power demands in the PNW and CA are out of phase seasonally but that hydropower productions in the PNW and CA have strongly covaried on an annual basis in recent decades. Winter electric power demand and spring and annual hydropower production in the PNW are related to both El Nino-Southern Oscillation (ENSO) and the Pacific decadal oscillation (PDO) through variations in winter climate. Summer power demand in CA is related primarily to variations in the PDO in spring. Hydropower production in CA, despite recent covariation with the PNW, is not strongly related to ENSO variability overall. Primarily because of strong variations in supply in the PNW, potential hydropower transfers between the PNW and CA in spring and summer are shown to be correlated to ENSO and PDO, and the conditional probability distributions of these transfers are therefore predictable with long lead times. Such electric power transfers are estimated to have potential average annual benefits of $136 and $79 million for CA and the PNW, respectively, at the year-2000 regional demand level. These benefits are on average 11%-27% larger during cold ENSO/PDO events and are 16%-30% lower during warm ENSO/PDO events. Power transfers from the PNW to CA and hydropower production in CA are comparable in magnitude, on average.

  • 454. Walther, Alexander
    et al.
    Jeong, Jee-Hoon
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Chen, Deliang
    Evaluation of the warm season diurnal cycle of precipitation over Sweden simulated by the Rossby Centre regional climate model RCA32013In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 119, p. 131-139Article in journal (Refereed)
    Abstract [en]

    This study examines the diurnal cycle of precipitation over Sweden for the warm season (April to September) both in hourly observational data and in simulations from the Rossby Centre regional climate model (RCA3). A series of parallel long-term simulations of RCA3 with different horizontal resolutions - 50, 25, 12, and 6 km - were analyzed to investigate the sensitivity of the model's horizontal resolution to the simulated diurnal cycle of precipitation. Overall, a clear distinction between an afternoon peak for inland stations and an early morning peak for stations along the Eastern coast is commonly found both in observation and model results. However, the diurnal cycle estimated from the model simulations show too early afternoon peaks with too large amplitude compared to the observation. Increasing horizontal model resolution tends to reduce this bias both in peak timing and amplitude, but this resolution effect seems not to be monotonic; this is clearly seen only when comparing coarser resolution results with the 6 km resolution result. As the resolution increases, the peak timing and amplitude of the diurnal cycle of resolved large-scale precipitation become more similar to the observed cycle of total precipitation while the contribution of subgrid scale convective precipitation to the total precipitation decreases. An increase in resolution also tends to reduce too much precipitation of relatively light intensity over inland compared to the observation, which may also contribute to the more realistic simulation of the afternoon peak in convective precipitation. (C) 2011 Elsevier B.V. All rights reserved.

  • 455. Wang, Jia
    et al.
    Kwok, Ron
    Saucier, F. J.
    Hutchings, J
    Ikeda, M
    Hibler III, W
    Haapala, J
    Coon, M.D.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Eicken, H
    Tanaka, N
    Prentki, D
    Johnsson, W
    Working toward improved small‐scale sea ice‐ocean modeling in the Arctic seas2003In: EOS: Transactions, ISSN 0096-3941, E-ISSN 2324-9250, Vol. 84, no 34, p. 325-330Article in journal (Refereed)
  • 456. Wang, Zhan
    et al.
    Belusic, Danijel
    SMHI, Research Department, Climate research - Rossby Centre.
    Huang, Yi
    Siems, Steven T.
    Manton, Michael J.
    Understanding Orographic Effects on Surface Observations at Macquarie Island2016In: Journal of Applied Meteorology and Climatology, ISSN 1558-8424, E-ISSN 1558-8432, Vol. 55, no 11, p. 2377-2395Article in journal (Refereed)
  • 457. Westra, S.
    et al.
    Fowler, H. J.
    Evans, J. P.
    Alexander, L. V.
    Berg, Peter
    SMHI, Research Department, Climate research - Rossby Centre.
    Johnson, F.
    Kendon, E. J.
    Lenderink, G.
    Roberts, N. M.
    Future changes to the intensity and frequency of short-duration extreme rainfall2014In: Reviews of geophysics, ISSN 8755-1209, E-ISSN 1944-9208, Vol. 52, no 3, p. 522-555Article, review/survey (Refereed)
    Abstract [en]

    Evidence that extreme rainfall intensity is increasing at the global scale has strengthened considerably in recent years. Research now indicates that the greatest increases are likely to occur in short-duration storms lasting less than a day, potentially leading to an increase in the magnitude and frequency of flash floods. This review examines the evidence for subdaily extreme rainfall intensification due to anthropogenic climate change and describes our current physical understanding of the association between subdaily extreme rainfall intensity and atmospheric temperature. We also examine the nature, quality, and quantity of information needed to allow society to adapt successfully to predicted future changes, and discuss the roles of observational and modeling studies in helping us to better understand the physical processes that can influence subdaily extreme rainfall characteristics. We conclude by describing the types of research required to produce a more thorough understanding of the relationships between local-scale thermodynamic effects, large-scale atmospheric circulation, and subdaily extreme rainfall intensity.

  • 458.
    Wetterhall, Fredrik
    et al.
    SMHI, Research Department, Hydrology.
    Bardossy, Andras
    Chen, Deliang
    Halldin, Sven
    Xu, Chong-yu
    Statistical downscaling of daily precipitation over Sweden using GCM output2009In: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483, Vol. 96, no 1-2, p. 95-103Article in journal (Refereed)
    Abstract [en]

    A classification of Swedish weather patterns (SWP) was developed by applying a multi-objective fuzzy-rule-based classification method (MOFRBC) to large-scale-circulation predictors in the context of statistical downscaling of daily precipitation at the station level. The predictor data was mean sea level pressure (MSLP) and geopotential heights at 850 (H850) and 700 hPa (H700) from the NCEP/NCAR reanalysis and from the HadAM3 GCM. The MOFRBC was used to evaluate effects of two future climate scenarios (A2 and B2) on precipitation patterns on two regions in south-central and northern Sweden. The precipitation series were generated with a stochastic, autoregressive model conditioned on SWP. H850 was found to be the optimum predictor for SWP, and SWP could be used instead of local classifications with little information lost. The results in the climate projection indicated an increase in maximum 5-day precipitation and precipitation amount on a wet day for the scenarios A2 and B2 for the period 2070-2100 compared to 1961-1990. The relative increase was largest in the northern region and could be attributed to an increase in the specific humidity rather than to changes in the circulation patterns.

  • 459. White, Christopher J.
    et al.
    Carlsen, Henrik
    Robertson, Andrew W.
    Klein, Richard J. T.
    Lazo, Jeffrey K.
    Kumar, Arun
    Vitart, Frederic
    de Perez, Erin Coughlan
    Ray, Andrea J.
    Murray, Virginia
    Bharwani, Sukaina
    MacLeod, Dave
    James, Rachel
    Fleming, Lora
    Morse, Andrew P.
    Eggen, Bernd
    Graham, Richard
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Becker, Emily
    Pegion, Kathleen V.
    Holbrook, Neil J.
    McEvoy, Darryn
    Depledge, Michael
    Perkins-Kirkpatrick, Sarah
    Brown, Timothy J.
    Street, Roger
    Jones, Lindsey
    Remenyi, Tomas A.
    Hodgson-Johnston, Indi
    Buontempo, Carlo
    Lamb, Rob
    Meinke, Holger
    Arheimer, Berit
    SMHI, Research Department, Hydrology.
    Zebiak, Stephen E.
    Potential applications of subseasonal-to-seasonal (S2S) predictions2017In: Meteorological Applications, ISSN 1350-4827, E-ISSN 1469-8080, Vol. 24, no 3, p. 315-325Article in journal (Refereed)
  • 460. Wibig, Joanna
    et al.
    Maraun, Douglas
    Benestad, Rasmus
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Lorenz, Philip
    Christensen, Ole Bossing
    Projected Change-Models and Methodology2015Chapter in book (Other academic)
    Abstract [en]

    General (global) circulation models (GCMs) are a useful tool for studying how climate may change in the future. Although GCMs have high temporal resolution, their spatial resolution is low. To simulate the future climate of the Baltic Sea region, it is necessary to downscale GCM data. This chapter describes the two conceptually different ways of downscaling: regional climate models (RCMs) nested in GCMs and using empirical and/or statistical relations between large-scale variables from GCMs and small-scale variables. There are many uncertainties in climate models, including uncertainty related to future land use and atmospheric greenhouse gas concentrations, limits on the amount of input data and their accuracy, and the chaotic nature of weather. The skill of methods for describing regional climate futures is also limited by natural climate variability. For the Baltic Sea area, the lack of an oceanic component in RCMs and poor representation of forcing by aerosols and changes in land use are major limitations.

  • 461.
    Wilcke, Renate
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Selecting regional climate scenarios for impact modelling studies2016In: Environmental Modelling & Software, ISSN 1364-8152, E-ISSN 1873-6726, Vol. 78, p. 191-201Article in journal (Refereed)
    Abstract [en]

    In climate change research ensembles of climate simulations are produced in an attempt to cover the uncertainty in future projections. Many climate change impact studies face difficulties using the full number of simulations available, and therefore often only subsets are used. Until now such subsets were chosen based on their representation of temperature change or by accessibility of the simulations. By using more specific information about the needs of the impact study as guidance for the clustering of simulations, the subset fits the purpose of climate change impact research more appropriately. Here, the sensitivity of such a procedure is explored, particularly with regard to the use of different climate variables, seasons, and regions in Europe. While temperature dominates the clustering, the resulting selection is influenced by all variables, leading to the conclusion that different subsets fit different impact studies best. (C) 2016 The Authors. Published by Elsevier Ltd.

  • 462.
    Wilk, Julie
    et al.
    SMHI, Research Department, Hydrology.
    Jonsson, Anna
    SMHI, Core Services.
    Rydhagen, Birgitta
    Rani, Ashu
    Kumar, Arun
    The perspectives of the urban poor in climate vulnerability assessments - The case of Kota, India2018In: Urban Climate, ISSN 2212-0955, E-ISSN 2212-0955, Vol. 24, p. 633-642Article in journal (Refereed)
  • 463.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Comparison of Model and Cloud Radar Derived Cloud Vertical Structure and Overlap for the BALTEX BRIDGE Campaign.2004In: Fourth Study Conference on BALTEX: Conference Proceedings / [ed] Hans-Jörg Isemer, 2004, p. 18-Conference paper (Other academic)
  • 464.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Comparison of modeled and radar measured cloud fraction and overlap2005In: Extended abstracts of a WMO/WCRP-sponsored Regional-Scale Climate Modelling Workshop [Elektronisk resurs] : high-resolution climate modelling : assessment, added value and applications, Lund, Sweden, 29 March-2 April 2004 / [ed] Lars Bärring & René Laprise, Lund: Department of Physical Geography & Ecosystems Analysis, Lund University , 2005, p. 128-Conference paper (Other academic)
  • 465.
    Willén, Ulrika
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Crewell, S.
    Comparison of model and cloud radar derived cloud vertical structure and overlap.2004In: 14th International Conference on Clouds and Precipitation(ICCP), 2004, p. 1434-1437Conference paper (Other academic)
  • 466.
    Willén, Ulrika
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Crewell, S
    Baltink, H K
    Sievers, O
    Assessing model predicted vertical cloud structure and cloud overlap with radar and lidar ceilometer observations for the Baltex Bridge Campaign of CLIWA-NET2005In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 75, no 3, p. 227-255Article in journal (Refereed)
    Abstract [en]

    The cloud vertical distribution and overlap of four large-scale models operating at different horizontal and vertical resolutions have been assessed using radar and lidar observations from the Baltex Bridge Campaign of CLIWA-NET. The models range from the global European Centre for Medium range Weather Forecast (ECMWF) model, to the Regional Atmospheric Climate Model (RACMO) and the Rossby Centre Atmospheric (RCA) regional climate model, to the non-hydrostatic meso-scale Lokal Model (LM). Different time averaging periods for the radar data were used to estimate the uncertainty of the point-to-space transformations of the observations. Relative to the observations, all models underestimated the height of the lowest cloud base. Clouds occurred more frequently in the models but with smaller cloud fractions below 7 km. The findings confirm previous cloud radar studies which found that models overestimate cloud fractions above 7 km. Radar-observed clouds were often thinner than the model vertical resolutions, which can have serious implications on model cloud overlap and radiation fluxes. The radar-derived cloud overlap matrix, which takes into account the overlap of all vertical layers, was found to be close to maximum-random overlap. Using random overlap for vertically continuous clouds with vertical gradients in cloud fraction larger than 40-50% per kilometre gave the best fit to the data. The gradient approach could be improved by making it resolution- and cloud system-dependent. Previous cloud radar overlap studies have considered the overlap of two cloud layers as a function of maximum and random overlap. Here, it was found that the two-layer overlap could be modelled by a mixture of maximum and minimum overlap. (c) 2005 Elsevier B.V. All rights reserved.

  • 467.
    Willén, Ulrika
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Baltink, Henk Klein
    Quante, Markus
    COMPARISON OF MODEL AND CLOUD RADAR DERIVED CLOUD OVERLAP2002Conference paper (Other academic)
  • 468. Winsor, P
    et al.
    Rodhe, J
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Baltic Sea ocean climate: an analysis of 100 yr of hydrographic data with focus on the freshwater budget2001In: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 18, no 1-2, p. 5-15Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea climate is analysed based upon long-term oceanographic measurements. The objective of the work is to study the natural variability of present day climate with focus on the freshwater budget. The results are designed to be used for validation of climate models and for discrimination of the significance of modelled climate change scenarios. Almost 100 yr of observations are used in the study, including data for river runoff, water exchange through the Danish Straits (as calculated from river runoff and from sea level data from the Kattegat), salinity data from the Baltic Sea and the Kattegat, and oxygen content in the deep Baltic Sea. The analyses illustrate that freshwater supply to the Baltic shows large variations on time scales up to several decades. The long-term variations in freshwater storage are closely correlated to accumulated changes in river runoff. This indicates strong positive feedback between the amount of outflowing surface water from the Baltic Sea and the salinity of the inflowing Kattegat water. One implication of the study is that climate control simulations must cover several decades, probably up to 100 yr in order to capture the natural variability of present day climate. Also, models designed to study climate change for the Baltic Sea probably need to start integrating from the present day.

  • 469. Wormbs, N.
    et al.
    Nilsson, A.E.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Sörlin, S.
    The History of Emerging Arctic Climate Modelling, poster presented at the IPY final conference in Oslo2010Conference paper (Other academic)
  • 470. Wramneby, Anna
    et al.
    Smith, Benjamin
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Hot spots of vegetation-climate feedbacks under future greenhouse forcing in Europe2010In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 115, article id D21119Article in journal (Refereed)
    Abstract [en]

    We performed simulations of future biophysical vegetation-climate feedbacks with a regional Earth System Model, RCA-GUESS, interactively coupling a regional climate model and a process-based model of vegetation dynamics and biogeochemistry. Simulated variations in leaf area index and in the relative coverage of evergreen forest, deciduous forest, and open land vegetation in response to simulated climate influence atmospheric state via variations in albedo, surface roughness, and the partitioning of the land-atmosphere heat flux into latent and sensible components. The model was applied on a similar to 50 x 50 km grid over Europe under a future climate scenario. Three potential "hot spots" of vegetation-climate feedbacks could be identified. In the Scandinavian Mountains, reduced albedo resulting from the snow-masking effect of forest expansion enhanced the winter warming trend. In central Europe, the stimulation of photosynthesis and plant growth by "CO2 fertilization" mitigated warming, through a negative evapotranspiration feedback associated with increased vegetation cover and leaf area index. In southern Europe, increased summer dryness restricted plant growth and survival, causing a positive warming feedback through reduced evapotranspiration. Our results suggest that vegetation-climate feedbacks over the European study area will be rather modest compared to the radiative forcing of increased global CO2 concentrations but may modify warming projections locally, regionally, and seasonally, compared with results from traditional "off-line" regional climate models lacking a representation of the relevant feedback mechanisms.

  • 471. Wu, Minchao
    et al.
    Schurgers, Guy
    Rummukainen, Markku
    SMHI, Core Services.
    Smith, Benjamin
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Jansson, Christer
    Siltberg, Joe
    May, Wilhelm
    Vegetation-climate feedbacks modulate rainfall patterns in Africa under future climate change2016In: Earth System Dynamics, ISSN 2190-4979, E-ISSN 2190-4987, Vol. 7, no 3, p. 627-647Article in journal (Refereed)
  • 472.
    Wyser, Klaus
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Modeled and observed clouds during Surface Heat Budget of the Arctic Ocean (SHEBA)2005In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 110, no D9, article id D09207Article in journal (Refereed)
    Abstract [en]

    [1] Observed monthly mean cloud cover from the SHEBA site is found to differ by a substantial amount during winter depending on cloud observing instrument. This makes it difficult for climate modelers to evaluate modeled clouds and improve parameterizations. Many instruments and human observers cannot properly detect the thinnest clouds and count them as clear sky instead, resulting in too low cloud cover. To study the impact from the difficulties in the detection of thin clouds, we compute cloud cover in our model with a filter that removes the thinnest clouds. Optical thickness is used as a proxy to identify thin clouds as we are mainly interested in the impact of clouds on radiation. With the results from a regional climate model simulation of the Arctic, we can reproduce the large variability in wintertime cloud cover between instruments when assuming different cloud detection thresholds. During winter a large fraction of all clouds are optically thin, which causes the large sensitivity to filtering by optical thickness. During summer, most clouds are far above the optical thickness threshold and filtering has no effect. A fair comparison between observed and modeled cloud cover should account for thin clouds that may be present in models but absent in the observational data set. Difficulties with the proper identification of clouds and clear sky also has an effect on cloud radiative forcing. The derived clear-sky longwave flux at the surface can vary by some W m(-2) depending on the lower limit for the optical thickness of clouds. This impacts on the "observed'' LW cloud radiative forcing and suggests great care is needed in using satellite-derived cloud radiative forcing for model development.

  • 473.
    Wyser, Klaus
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Du, P.
    Girard, E.
    Willen, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Cassano, J.
    Christensen, J. H.
    Curry, J. A.
    Dethloff, K.
    Haugen, J. -E
    Jacob, D.
    Koltzow, M.
    Laprise, R.
    Lynch, A.
    Pfeifer, S.
    Rinke, A.
    Serreze, M.
    Shaw, M. J.
    Tjernstrom, M.
    Zagar, M.
    An evaluation of Arctic cloud and radiation processes during the SHEBA year: simulation results from eight Arctic regional climate models2008In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 30, no 2-3, p. 203-223Article in journal (Refereed)
    Abstract [en]

    Eight atmospheric regional climate models (RCMs) were run for the period September 1997 to October 1998 over the western Arctic Ocean. This period was coincident with the observational campaign of the Surface Heat Budget of the Arctic Ocean (SHEBA) project. The RCMs shared common domains, centred on the SHEBA observation camp, along with a common model horizontal resolution, but differed in their vertical structure and physical parameterizations. All RCMs used the same lateral and surface boundary conditions. Surface downwelling solar and terrestrial radiation, surface albedo, vertically integrated water vapour, liquid water path and cloud cover from each model are evaluated against the SHEBA observation data. Downwelling surface radiation, vertically integrated water vapour and liquid water path are reasonably well simulated at monthly and daily timescales in the model ensemble mean, but with considerable differences among individual models. Simulated surface albedos are relatively accurate in the winter season, but become increasingly inaccurate and variable in the melt season, thereby compromising the net surface radiation budget. Simulated cloud cover is more or less uncorrelated with observed values at the daily timescale. Even for monthly averages, many models do not reproduce the annual cycle correctly. The inter-model spread of simulated cloud-cover is very large, with no model appearing systematically superior. Analysis of the co-variability of terms controlling the surface radiation budget reveal some of the key processes requiring improved treatment in Arctic RCMs. Improvements in the parameterization of cloud amounts and surface albedo are most urgently needed to improve the overall performance of RCMs in the Arctic.

  • 474.
    Wyser, Klaus
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Modelling clouds and radiation in the Arctic2005In: Extended abstracts of a WMO/WCRP-sponsored Regional-Scale Climate Modelling Workshop [Elektronisk resurs] : high-resolution climate modelling : assessment, added value and applications / [ed] Lars Bärring & René Laprise, Lund: Department of Physical Geography & Ecosystems Analysis, Lund University , 2005, p. 128-Conference paper (Other academic)
  • 475.
    Wyser, Klaus
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Modelling clouds and radiation in the ARctic.2004In: 14th International conference on clouds and precipitation, 2004, p. 1442-1445Conference paper (Other academic)
  • 476. Xavier, Prince K.
    et al.
    Petch, Jon C.
    Klingaman, Nicholas P.
    Woolnough, Steve J.
    Jiang, Xianan
    Waliser, Duane E.
    Caian, Mihaela
    SMHI, Research Department, Climate research - Rossby Centre.
    Cole, Jason
    Hagos, Samson M.
    Hannay, Cecile
    Kim, Daehyun
    Miyakawa, Tomoki
    Pritchard, Michael S.
    Roehrig, Romain
    Shindo, Eiki
    Vitart, Frederic
    Wang, Hailan
    Vertical structure and physical processes of the Madden-Julian Oscillation: Biases and uncertainties at short range2015In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 120, no 10, p. 4749-4763Article in journal (Refereed)
    Abstract [en]

    An analysis of diabatic heating and moistening processes from 12 to 36h lead time forecasts from 12 Global Circulation Models are presented as part of the Vertical structure and physical processes of the Madden-Julian Oscillation (MJO) project. A lead time of 12-36h is chosen to constrain the large-scale dynamics and thermodynamics to be close to observations while avoiding being too close to the initial spin-up of the models as they adjust to being driven from the Years of Tropical Convection (YOTC) analysis. A comparison of the vertical velocity and rainfall with the observations and YOTC analysis suggests that the phases of convection associated with the MJO are constrained in most models at this lead time although the rainfall in the suppressed phase is typically overestimated. Although the large-scale dynamics is reasonably constrained, moistening and heating profiles have large intermodel spread. In particular, there are large spreads in convective heating and moistening at midlevels during the transition to active convection. Radiative heating and cloud parameters have the largest relative spread across models at upper levels during the active phase. A detailed analysis of time step behavior shows that some models show strong intermittency in rainfall and differences in the precipitation and dynamics relationship between models. The wealth of model outputs archived during this project is a very valuable resource for model developers beyond the study of the MJO. In addition, the findings of this study can inform the design of process model experiments, and inform the priorities for field experiments and future observing systems.

  • 477. Zadra, Ayrton
    et al.
    Caya, Daniel
    Coté, Jean
    Dugas, Bernard
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Laprise, René
    Winger, Katja
    Caron, Louis-Philippe
    The next Canadian Regional Climate Model.2008In: Physics in Canada, Vol. 64, no 2Article in journal (Refereed)
  • 478. Zampieri, M.
    et al.
    Giorgi, F.
    Lionello, P.
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Regional climate change in the Northern Adriatic2012In: Physics and Chemistry of the Earth, ISSN 1474-7065, E-ISSN 1873-5193, Vol. 40-41, p. 32-46Article in journal (Refereed)
    Abstract [en]

    An analysis of the climate change signal for seasonal temperature and precipitation over the Northern Adriatic region is presented here. We collected 43 regional climate simulations covering the target area, including experiments produced in the context of the PRUDENCE and ENSEMBLES projects, and additional experiments produced by the Swedish Meteorological and Hydrological Institute. The ability of the models to simulate the present climate in terms of mean and interannual variability is discussed and the insufficient reproduction of some features, such as the intensity of summer precipitation, are shown. The contribution to the variance associated with the intermodel spread is computed. The changes of mean and interannual variability are analyzed for the period 2071-2100 in the PRUDENCE runs (A2 scenario) and the periods 2021-2050 and 2071-2100 (A1B scenario) for the other runs. Ensemble results show a major warming at the end of the 21st century. Warming will be larger in the A2 scenario (about 5.5 K in summer and 4 K in winter) than in the A1B. Precipitation is projected to increase in winter and decrease in summer by 20% (+0.5 mm/day and -1 mm/day over the Alps, respectively). The climate change signal for scenario A1B in the period 2021-2050 is significant for temperature, but not yet for precipitation. In summer, interannual variability is projected to increase for temperature and for precipitation. Winter interannual variability change is different among scenarios. A reduction of precipitation is found for A2, while for A1B a reduction of temperature interannual variability is observed. (C) 2010 Elsevier Ltd. All rights reserved.

  • 479. Zarekarizi, Mahkameh
    et al.
    Rana, Arun
    SMHI, Research Department, Climate research - Rossby Centre.
    Moradkhani, Hamid
    Precipitation extremes and their relation to climatic indices in the Pacific Northwest USA2018In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, no 11-12, p. 4519-4537Article in journal (Refereed)
  • 480. Zhang, W.
    et al.
    Jansson, Christer
    SMHI, Research Department, Climate research - Rossby Centre.
    Miller, P. A.
    Smith, B.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Biogeophysical feedbacks enhance the Arctic terrestrial carbon sink in regional Earth system dynamics2014In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, no 19, p. 5503-5519Article in journal (Refereed)
    Abstract [en]

    Continued warming of the Arctic will likely accelerate terrestrial carbon (C) cycling by increasing both uptake and release of C. Yet, there are still large uncertainties in modelling Arctic terrestrial ecosystems as a source or sink of C. Most modelling studies assessing or projecting the future fate of C exchange with the atmosphere are based on either stand-alone process-based models or coupled climate-C cycle general circulation models, and often disregard biogeophysical feedbacks of land-surface changes to the atmosphere. To understand how biogeophysical feedbacks might impact on both climate and the C budget in Arctic terrestrial ecosystems, we apply the regional Earth system model RCA-GUESS over the CORDEX-Arctic domain. The model is forced with lateral boundary conditions from an EC-Earth CMIP5 climate projection under the representative concentration pathway (RCP) 8.5 scenario. We perform two simulations, with or without interactive vegetation dynamics respectively, to assess the impacts of biogeophysical feedbacks. Both simulations indicate that Arctic terrestrial ecosystems will continue to sequester C with an increased uptake rate until the 2060-2070s, after which the C budget will return to a weak C sink as increased soil respiration and biomass burning outpaces increased net primary productivity. The additional C sinks arising from biogeophysical feedbacks are approximately 8.5 Gt C, accounting for 22% of the total C sinks, of which 83.5% are located in areas of extant Arctic tundra. Two opposing feedback mechanisms, mediated by albedo and evapotranspiration changes respectively, contribute to this response. The albedo feedback dominates in the winter and spring seasons, amplifying the near-surface warming by up to 1.35 degrees C in spring, while the evapotranspiration feedback dominates in the summer months, and leads to a cooling of up to 0.81 degrees C. Such feedbacks stimulate vegetation growth due to an earlier onset of the growing season, leading to compositional changes in woody plants and vegetation redistribution.

  • 481. Zhang, W.
    et al.
    Miller, P. A.
    Jansson, C.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Mao, J.
    Smith, B.
    Self-Amplifying Feedbacks Accelerate Greening and Warming of the Arctic2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 14, p. 7102-7111Article in journal (Refereed)
  • 482. Zhang, Wenxin
    et al.
    Miller, Paul A.
    Smith, Benjamin
    Wania, Rita
    Koenigk, Torben
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Tundra shrubification and tree-line advance amplify arctic climate warming: results from an individual-based dynamic vegetation model2013In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 8, no 3, article id 034023Article in journal (Refereed)
    Abstract [en]

    One major challenge to the improvement of regional climate scenarios for the northern high latitudes is to understand land surface feedbacks associated with vegetation shifts and ecosystem biogeochemical cycling. We employed a customized, Arctic version of the individual-based dynamic vegetation model LPJ-GUESS to simulate the dynamics of upland and wetland ecosystems under a regional climate model-downscaled future climate projection for the Arctic and Subarctic. The simulated vegetation distribution (1961-1990) agreed well with a composite map of actual arctic vegetation. In the future (2051-2080), a poleward advance of the forest-tundra boundary, an expansion of tall shrub tundra, and a dominance shift from deciduous to evergreen boreal conifer forest over northern Eurasia were simulated. Ecosystems continued to sink carbon for the next few decades, although the size of these sinks diminished by the late 21st century. Hot spots of increased CH4 emission were identified in the peatlands near Hudson Bay and western Siberia. In terms of their net impact on regional climate forcing, positive feedbacks associated with the negative effects of tree-line, shrub cover and forest phenology changes on snow-season albedo, as well as the larger sources of CH4, may potentially dominate over negative feedbacks due to increased carbon sequestration and increased latent heat flux.

  • 483.
    FN:s klimatpanel – Sammanfattning för beslutsfattare Global uppvärmning på 1,5ºC2019Report (Refereed)
    Abstract [en]

    This Report responds to the invitation for IPCC ‘... to provide a Special Report in 2018 on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways’ contained in the Decision of the 21st Conference of Parties of the United Nations Framework Convention on Climate Change to adopt the Paris Agreement. The IPCC accepted the invitation in April 2016, deciding to prepare this Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. This Summary for Policymakers (SPM) presents the key findings of the Special Report, based on the assessment of the available scientific, technical and socio-economic literature relevant to global warming of 1.5°C and for the comparison between global warming of 1.5°C and 2°C above pre-industrial levels. The level of confidence associated with each key finding is reported using the IPCC calibrated language. The underlying scientific basis of each key finding is indicated by references provided to chapter elements. In the SPM, knowledge gaps are identified associated with the underlying chapters of the Report.

  • 484.
    FN:s klimatpanel – Sammanfattning för beslutsfattare Global uppvärmning på 1,5ºC2019Report (Other academic)
    Abstract [sv]

    Denna rapport har tagits fram på förfrågan till IPCC ”… att till år 2018 ta fram en specialrapport om konsekvenserna av 1,5°C uppvärmning jämfört med förindustriella nivåer och relaterade globala utsläppsbanor av växthusgaser”. Detta framgår av 21:a partskonferensen av FN:s ramkonvention om klimatförändringar beslut om antagande av Parisavtalet.

    IPCC beslutade i april 2016 att ta fram denna specialrapport om effekter av global uppvärmning på 1,5°C över förindustriella nivåer och relaterade utsläppsbanor av växthusgaser, i syfte att stärka den globala förmågan att svara upp mot hotet från klimatförändringen, målsättningar inom hållbar utveckling och ansträngningar för att utrota fattigdom.

    I denna Sammanfattning för beslutsfattare (“Summary for Policy Makers”, SPM) presenteras specialrapportens viktigaste slutsatser baserat på utvärderingen av tillgänglig vetenskaplig, teknisk och socioekonomisk litteratur med relevans för en global uppvärmning på 1,5°C och för att kunna jämföra mellan en global uppvärmning på 1,5°C och 2°C över förindustriell nivå. Konfidensnivån för varje central slutsats anges med IPCC:s standardiserade terminologi. Den vetenskapliga grunden för varje slutsats anges genom referenser till avsnitt i respektive kapitel. I sammanfattningen identifieras ävenkunskapsluckor, med hänvisning till relevanta underliggande kapitel.

  • 485.
    Karttjänst för framtida medelvattenstånd längs Sveriges kust2018Report (Other academic)
    Abstract [sv]

    Havsnivån stiger och orsaken är den globala uppvärmningen. Effekterna av uppvärmningen på havets nivå kommer främst från den termiska expansionen samt bidrag från smältande glaciärer och de stora landisarna på Grönland och Antarktis.

    Hur snabbt den globala havsnivån stiger beror på hur stora utsläppen av växthusgaser blir. Globala medelvattenstånd fram till år 2100 har framtagits inom IPCC och beskrivs utifrån klimatscenarier, som innebär olika antaganden om den framtida utvecklingen. Oavsett klimatscenario stiger havsnivån och den kommer att fortsätta stiga även efter år 2100. Störst osäkerhet råder, angående framtida havsnivåer, kring avsmältningen av de stora ismassorna på Grönland och Antarktis.

    Medelvattenståndet är den nivå som avgör var strandlinjen normalt ligger och som höga och låga vattenstånd varierar kring. Medelvattenståndet längs Sveriges kuster kommer att förändras olika mycket, främst beroende på den pågående landhöjningen. Andra regionala processer som kan påverka medelvattenståndet är dåligt kända men bedöms i nuläget vara små.

    Globala medelvattenstånd, framtagna inom IPCC AR5, i kombination med landhöjningsinformation från Lantmäteriet har använts för att göra beräkningar av framtida medelvattenstånd längs svenska kusten. Beräkningarna sträcker sig till år 2100. Medelvattenstånd vid observationsplatser längs kusten för referensperioden 1986-2005 används som utgångsvärde.

    Resultaten har publicerats i en karttjänst som visar medelvattenståndet enligt tre olika utsläppsscenarier kring år 2050 respektive år 2100. Karttjänsten ger indikationer för vilka områden som kan vara sårbara för stigande havsnivåer.

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