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  • 251. Linders, Viktor
    et al.
    Kupiainen, Marco
    SMHI, Research Department, Climate research - Rossby Centre.
    Nordstrom, Jan
    Summation-by-Parts operators with minimal dispersion error for coarse grid flow calculations2017In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 340, p. 160-176Article in journal (Refereed)
  • 252.
    Lindstedt, David
    SMHI, Research Department, Climate research - Rossby Centre.
    Effekter av djupvattenomblandning i Östersjön – en modellstudie2008Report (Other academic)
    Abstract [sv]

    Blandningen av vattenmassorna har mycket stor betydelse i ett halvinslutet hav som Östersjön. Den påverkar bland annat havsströmmar, yttemperatur och algblomning. Blandningen orsakas främst av skjuvning från vind- och isstress, buoyancyflöden på grund av avkylning eller avdunstning vid ytan samt skjuvning från interna vågor.Genom att jämföra olika turbulensmodeller har skillnader av förnyelsen av djupvattnet i Östersjön studerats. Till detta har en kopplad tredimensionell fysikalisk-biogeokemisk modell använts. Den grundar sig på Rossby Centre Ocean Model (RCO) och Swedish Coastal and Ocean Biogeochemical model (SCOBI). I havsmodellen har blandningen beräknats med en turbulensmodell av typen k-e. Stabilitetsfunktionerna består av ett Richardsonsberoende Prandtltal. Som jämförelse har samma turbulensmodell använts men med en mer komplex stabilitetsfunktion. Slutligen har även effekterna av ett blandningsschema av typen KPP (K Profil Parametrisation) studerats. Djupvattenomblandningen på grund av interna vågor är parametriserad som en funktion av buoyancyfrekvensen för samtliga turbulensmodeller.Studien visade att KPP modellen simulerar den lägsta blandningen vilket ger ett för tunt väl omblandat ytskikt. k-e modellen med modifierade stabilitetsfunktioner har det lägsta inflödet av saltrikt vatten medan KPP har det högsta inflödet. Den horisontella advektionen av djupvatten in till östra Gotlandsbassängen är högst i den modifierade k-e modellen vilket har störst påverkan för syrenivån.

  • 253.
    Lindstedt, David
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Lind, Petter
    SMHI, Research Department, Climate research - Rossby Centre.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    A new regional climate model operating at the meso-gamma scale: performance over Europe2015In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 67, article id 24138Article in journal (Refereed)
    Abstract [en]

    There are well-known difficulties to run numerical weather prediction (NWP) and climate models at resolutions traditionally referred to as 'grey-zone' (similar to 3-8 km) where deep convection is neither completely resolved by the model dynamics nor completely subgrid. In this study, we describe the performance of an operational NWP model, HARMONIE, in a climate setting (HCLIM), run at two different resolutions (6 and 15 km) for a 10-yr period (1998-2007). This model has a convection scheme particularly designed to operate in the 'grey-zone' regime, which increases the realism and accuracy of the time and spatial evolution of convective processes compared to more traditional parametrisations. HCLIM is evaluated against standard observational data sets over Europe as well as high-resolution, regional, observations. Not only is the regional climate very well represented but also higher order climate statistics and smaller scale spatial characteristics of precipitation are in good agreement with observations. The added value when making climate simulations at similar to 5 km resolution compared to more typical regional climate model resolutions is mainly seen for the very rare, high-intensity precipitation events. HCLIM at 6 km resolution reproduces the frequency and intensity of these events better than at 15 km resolution and is in closer agreement with the high-resolution observations.

  • 254.
    Lucas-Picher, Philippe
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Boberg, Fredrik
    Christensen, Jens H.
    Berg, Peter
    SMHI, Research Department, Climate research - Rossby Centre.
    Dynamical Downscaling with Reinitializations: A Method to Generate Finescale Climate Datasets Suitable for Impact Studies2013In: Journal of Hydrometeorology, ISSN 1525-755X, E-ISSN 1525-7541, Vol. 14, no 4, p. 1159-1174Article in journal (Refereed)
    Abstract [en]

    To retain the sequence of events of a regional climate model (RCM) simulation driven by a reanalysis, a method that has not been widely adopted uses an RCM with frequent reinitializations toward its driving field. In this regard, this study highlights the benefits of an RCM simulation with frequent (daily) reinitializations compared to a standard continuous RCM simulation. Both simulations are carried out with the RCM HIRHAM5, driven with the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) data, over the 12-km-resolution European Coordinated Regional Climate Downscaling Experiment (CORDEX) domain covering the period 1989-2009. The analysis of daily precipitation shows improvements in the sequence of events and the maintenance of the added value from the standard continuous RCM simulation. The validation of the two RCM simulations with observations reveals that the simulation with reinitializations indeed improves the temporal correlation. Furthermore, the RCM simulation with reinitializations has lower systematic errors compared to the continuous simulation, which has a tendency to be too wet. A comparison of the distribution of wet day precipitation intensities shows similar added value in the continuous and reinitialized simulations with higher variability and extremes compared to the driving field ERA-Interim. Overall, the results suggest that the finescale climate dataset of the RCM simulation with reinitializations better suits the needs of impact studies by providing a sequence of events matching closely the observations, while limiting systematic errors and generating reliable added value. Downsides of the method with reinitializations are increased computational costs and the introduction of temporal discontinuities that are similar to those of a reanalysis.

  • 255.
    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.

  • 256. Mair, Louise
    et al.
    Harrison, Philip J.
    Raty, Minna
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    Snäll, Tord
    Forest management could counteract distribution retractions forced by climate change2017In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 27, no 5, p. 1485-1497Article in journal (Refereed)
  • 257. Mair, Louise
    et al.
    Jonsson, Mari
    Raty, Minna
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    Lamas, Tomas
    Snall, Tord
    Land use changes could modify future negative effects of climate change on old-growth forest indicator species2018In: Diversity & distributions: A journal of biological invasions and biodiversity, ISSN 1366-9516, E-ISSN 1472-4642, Vol. 24, no 10, p. 1416-1425Article in journal (Refereed)
  • 258. Maraun, Douglas
    et al.
    Widmann, Martin
    Gutierrez, Jose M.
    Kotlarski, Sven
    Chandler, Richard E.
    Hertig, Elke
    Wibig, Joanna
    Huth, Radan
    Wilcke, Renate
    SMHI, Research Department, Climate research - Rossby Centre.
    VALUE: A framework to validate downscaling approaches for climate change studies2015In: Earth's Future, ISSN 1384-5160, E-ISSN 2328-4277, Vol. 3, no 1, p. 1-14Article in journal (Refereed)
    Abstract [en]

    VALUE is an open European network to validate and compare downscaling methods for climate change research. VALUE aims to foster collaboration and knowledge exchange between climatologists, impact modellers, statisticians, and stakeholders to establish an interdisciplinary downscaling community. A key deliverable of VALUE is the development of a systematic validation framework to enable the assessment and comparison of both dynamical and statistical downscaling methods. In this paper, we present the key ingredients of this framework. VALUE's main approach to validation is user-focused: starting from a specific user problem, a validation tree guides the selection of relevant validation indices and performance measures. Several experiments have been designed to isolate specific points in the downscaling procedure where problems may occur: what is the isolated downscaling skill? How do statistical and dynamical methods compare? How do methods perform at different spatial scales? Do methods fail in representing regional climate change? How is the overall representation of regional climate, including errors inherited from global climate models? The framework will be the basis for a comprehensive community-open downscaling intercomparison study, but is intended also to provide general guidance for other validation studies.

  • 259. 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.

  • 260. 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)
  • 261. Martin, G. M.
    et al.
    Peyrille, P.
    Roehrig, R.
    Rio, C.
    Caian, Mihaela
    SMHI, Research Department, Climate research - Rossby Centre.
    Bellon, G.
    Codron, F.
    Lafore, J. -P
    Poan, D. E.
    Idelkadi, A.
    Understanding the West African Monsoon from the analysis of diabatic heating distributions as simulated by climate models2017In: Journal of Advances in Modeling Earth Systems, ISSN 1942-2466, Vol. 9, no 1, p. 239-270Article in journal (Refereed)
  • 262.
    Mattsson, Johan
    et al.
    SMHI.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    Växthuseffekten och klimatet i Norden - en översikt1998Report (Other academic)
  • 263. Maure, G.
    et al.
    Pinto, I.
    Ndebele-Murisa, M.
    Muthige, M.
    Lennard, C.
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Dosio, A.
    Meque, A.
    The southern African climate under 1.5 degrees C and 2 degrees C of global warming as simulated by CORDEX regional climate models2018In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 13, no 6, article id 065002Article in journal (Refereed)
  • 264. Mba, Wilfried Pokam
    et al.
    Longandjo, Georges-Noel T.
    Moufouma-Okia, Wilfran
    Bell, Jean-Pierre
    James, Rachel
    Vondou, Derbetini A.
    Haensler, Andreas
    Fotso-Nguemo, Thierry C.
    Guenang, Guy Merlin
    Tchotchou, Angennes Lucie Djiotang
    Kamsu-Tamo, Pierre H.
    Takong, Ridick R.
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Lennard, Christopher J.
    Dosio, Alessandro
    Consequences of 1.5 degrees C and 2 degrees C global warming levels for temperature and precipitation changes over Central Africa2018In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 13, no 5, article id 055011Article in journal (Refereed)
  • 265. McCreesh, Nicky
    et al.
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Booth, Mark
    Predicting the effects of climate change on Schistosoma mansoni transmission in eastern Africa2015In: Parasites & Vectors, ISSN 1756-3305, E-ISSN 1756-3305, Vol. 8, article id 4Article in journal (Refereed)
    Abstract [en]

    Background: Survival and fitness attributes of free-living and sporocyst schistosome life-stages and their intermediate host snails are sensitive to water temperature. Climate change may alter the geographical distribution of schistosomiasis by affecting the suitability of freshwater bodies for hosting parasite and snail populations. Methods: We have developed an agent-based model of the temperature-sensitive stages of the Schistosoma mansoni and intermediate host snail lifecycles. The model was run using low, moderate and high warming climate projections over eastern Africa. For each climate projection, eight model scenarios were used to determine the sensitivity of predictions to different relationships between air and water temperature, and different snail mortality rates. Maps were produced showing predicted changes in risk as a result of increasing temperatures over the next 20 and 50 years. Results: Baseline model output compared to prevalence data indicates suitable temperatures are necessary but not sufficient for both S. mansoni transmission and high infection prevalences. All else being equal, infection risk may increase by up to 20% over most of eastern Africa over the next 20 and 50 years. Increases may be higher in Rwanda, Burundi, south-west Kenya and eastern Zambia, and S. mansoni may become newly endemic in some areas. Results for 20-year projections are robust to changes in simulated intermediate host snail habitat conditions. There is greater uncertainty about the effects of different habitats on changes in risk in 50 years' time. Conclusions: Temperatures are likely to become suitable for increased S. mansoni transmission over much of eastern Africa. This may reduce the impact of control and elimination programmes. S. mansoni may also spread to new areas outside existing control programmes. We call for increased surveillance in areas defined as potentially suitable for emergent transmission.

  • 266. McGinnity, Philip
    et al.
    Jennings, Eleanor
    DeEyto, Elvira
    Allott, Norman
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Rogan, Gerard
    Whelan, Ken
    Cross, Tom
    Impact of naturally spawning captive-bred Atlantic salmon on wild populations: depressed recruitment and increased risk of climate-mediated extinction2009In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 276, no 1673, p. 3601-3610Article in journal (Refereed)
    Abstract [en]

    The assessment report of the 4th International Panel on Climate Change confirms that global warming is strongly affecting biological systems and that 20-30% of species risk extinction from projected future increases in temperature. It is essential that any measures taken to conserve individual species and their constituent populations against climate-mediated declines are appropriate. The release of captive bred animals to augment wild populations is a widespread management strategy for many species but has proven controversial. Using a regression model based on a 37-year study of wild and sea ranched Atlantic salmon (Salmo salar) spawning together in the wild, we show that the escape of captive bred animals into the wild can substantially depress recruitment and more specifically disrupt the capacity of natural populations to adapt to higher winter water temperatures associated with climate variability. We speculate the mechanisms underlying this seasonal response and suggest that an explanation based on bio-energetic processes with physiological responses synchronized by photoperiod is plausible. Furthermore, we predict, by running the model forward using projected future climate scenarios, that these cultured fish substantially increase the risk of extinction for the studied population within 20 generations. In contrast, we show that positive outcomes to climate change are possible if captive bred animals are prevented from breeding in the wild. Rather than imposing an additional genetic load on wild populations by releasing maladapted captive bred animals, we propose that conservation efforts should focus on optimizing conditions for adaptation to occur by reducing exploitation and protecting critical habitats. Our findings are likely to hold true for most poikilothermic species where captive breeding programmes are used in population management.

  • 267.
    Meier, Markus
    SMHI, Research Department, Climate research - Rossby Centre.
    Regional ocean modeling – climate variability and impact studies of the Baltic Sea2005In: EXTENDED ABSTRACTS of a WMO/WCRP-sponsored REGIONAL-SCALE CLIMATE MODELLING WORKSHOP: HIGH-RESOLUTION CLIMATE MODELLING: ASSESSMENT, ADDED VALUE AND APPLICATIONS / [ed] Lars Bärring & René Laprise, Department of Physical Geography & Ecosystems Analysis Lund University, Sweden , 2005, p. 40-41Conference paper (Other academic)
  • 268.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Andréasson, Johan
    SMHI, Professional Services.
    Broman, Barry
    SMHI, Research Department, Climate research - Rossby Centre.
    Graham, Phil
    SMHI, Professional Services.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Persson, Gunn
    SMHI, Professional Services.
    Climate change scenario simulations of wind, sea level, and river discharge in the Baltic Sea and Lake Mälaren region – a dynamical downscaling approach from global to local scales2006Report (Other academic)
    Abstract [en]

    A regional climate model (RCM) and oceanographic, hydrological and digital elevation models were applied to study the impact of climate change on surface wind, sea level, river discharge, and flood prone areas in the Baltic Sea region. The RCM was driven by two global models and two emission scenarios. According to the four investigated regional scenario simulations, wind speed in winter is projected to increase between 3 and 19% as an area average over the Baltic Sea. Although extremes of the wind speed will increase about as much as the mean wind speed, sea level extremes will increase more than the mean sea level, especially along the eastern Baltic coasts. In these areas projected storm events and global average sea level rise may cause an increased risk for flooding. However, the Swedish east coast will be less affected because mainly the west wind component in winter would increase and because land uplift would compensate for increased sea levels, at least in the northern parts of the Baltic. One of the aims of the downscaling approach was to investigate the future risk of flooding in the Lake Mälaren region including Stockholm city. In Stockholm the 100-year surge is projected to change between -51 and 53 cm relative to present mean sea level suggesting that in the city the risk of flooding from the Baltic Sea is relatively small because the critical height of the jetty walls will not be exceeded. Lake Mälaren lies just to the west of Stockholm and flows directly into the Baltic Sea to the east. This study addresses also the question of how the water level in Lake Mälaren may be affected by climate change by incorporating the following three contributing components into an analysis: 1) projected changes to hydrological inflows to Lake Mälaren, 2) changes to downstream water levels in the Baltic Sea, and 3) changes in outflow regulation from the lake. The first component is analyzed using hydrological modeling. The second and third components employ the use of a lake discharge model. An important conclusion is that projected changes to hydrological inflows show a stronger impact on lake levels than projected changes in water level for the Baltic Sea. Furthermore, an identified need for increased outflow capacity from the lake for the present climate does not diminish with projections of future climate change. The tools developed in this work provide valuable inputs to planning for both present and future operations of water level in Lake Mälaren. Based on the oceanographic and hydrological scenario simulations, flood prone areas were analysed in detail for two municipalities, namely Ekerö and Stockholm. The GIS analysis of both municipalities indicates a series of affected areas. However, in case of the 100-year flood (0.65 m above the mean lake level) in present climate or even in case of the maximum probable flood (1.48 m above the mean lake level) the potential risks will be relatively low.

  • 269.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Broman, Barry
    SMHI, Research Department, Climate research - Rossby Centre.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Modelling Sea Level Variability in Different Climates of the Baltic Sea2004In: Fourth Study Conference on BALTEX: Conference Proceedings / [ed] Hans-Jörg Isemer, Risø National Laboratory Technical University of Denmark GKSS Forschungszentrum Geesthacht GmbH , 2004, p. 170-171Conference paper (Other academic)
  • 270.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Broman, Barry
    SMHI, Research Department, Climate research - Rossby Centre.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Simulated sea level in past and future climates of the Baltic Sea2004In: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 27, no 1, p. 59-75Article in journal (Refereed)
    Abstract [en]

    Sea levels of the Baltic Sea in past and future climates were investigated based upon 6-hourly regional model results. For the future climate, the Rossby Centre Atmosphere Ocean model was used to perform a set of 30 yr time slice experiments. For each of the 2 driving global models HadAM3H and ECHAM4/OPYC3, one control run (1961 to 1990) and 2 scenario runs (2071 to 2100) based upon the scenarios A2 and B2 of the Special Report on Emission Scenarios (SRES) were conducted. To estimate uncertainties in the global and regional models, 3 sea level scenarios for the Baltic Sea were compiled assuming global average sea level rises between 0.09 and 0.88 m and considering land uplift and the impact of regional changes in wind direction and velocity from the time slice experiments. In the scenarios forced with ECHAM4/OPYC3 the mean sea level between October and April increases significantly compared to the control climate, and storm surges increase even more than monthly mean sea level. In the scenarios forced with HadAM3H the changes are mostly not significant. Depending on the sea level rise, the risk of flooding at the coasts may either decrease in the entire Baltic, or it may increase, especially at the eastern ends of the Gulf of Finland and Gulf of Riga and in Gdansk Bay. Here, maximum changes of about 1 m are found in the winter mean 99% quantiles of the sea level. For the past climate the regional ocean model was forced with reconstructed surface wind fields for 1903 to 1998. The results are close to observations, but storm surges in the western Baltic are underestimated.

  • 271.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Christensen, Ole Bössing
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Lorenz, Philip
    Rockel, Burkhardt
    Zorita, Eduardo
    Selected examples of the added value of regional climate models2009In: / [ed] Rockel, B., Bärring, L and Reckermann, M., 2009, p. 54-55Conference paper (Other academic)
  • 272.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Simulated water and heat cycles of the Baltic Sea using a 3D coupled atmosphere-ice - ocean model2002In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 7, no 4, p. 327-334Article in journal (Refereed)
    Abstract [en]

    The heat and water cycles of the Baltic Sea are calculated utilizing multi-year model simulations. This is one of the major objectives of the BALTEX program. For the period 1988-1993, results of a 3D ice-ocean model forced with observed atmospheric surface fields are compared with results of a fully coupled atmosphere-ice-ocean model using re-analysis data at the lateral boundaries. The state-of-the-art coupled model system has been developed for climate study purposes in the Nordic countries. The model domain of the atmosphere model covers Scandinavia, Europe and parts of the North Atlantic whereas the ocean model is limited to the Baltic Sea. The annual and monthly mean heat budgets for the Baltic Sea are calculated from the dominating surface fluxes, i.e. sensible heat, latent heat, net longwave radiation and solar radiation to the open water or to the sea ice. The main part of the freshwater inflow to the Baltic is the river runoff. A smaller part of about 11 % is added from net precipitation. The heat and water cycles are compared with the results of a long-term simulation (1980-1993) using the stand-alone Baltic Sea model forced with observed atmospheric surface fields. In general, both approaches, using the uncoupled or coupled Baltic Sea model, give realistic estimates of the heat and water cycles and are in good agreement with results of other studies. However, in the coupled model the parameterizations of the latent heat flux and the incoming longwave radiation need to be improved.

  • 273.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Broman, Barry
    SMHI, Research Department, Climate research - Rossby Centre.
    Piechura, J
    The major Baltic inflow in January 2003 and preconditioning by smaller inflows in summer/autumn 2002: a model study2004In: Oceanologia, ISSN 0078-3234, Vol. 46, no 4, p. 557-579Article in journal (Refereed)
    Abstract [en]

    Using the results of the Rossby Centre Ocean model (RCO) the Baltic inflows in summer/autumn 2002 and January 2003 have been studied. The model results were extracted from a long simulation with observed atmospheric forcing Starting in May 1980. In RCO a bottom boundary layer model was embedded. Both the Smaller inflows and the major inflow in January 2003 are simulated in good agreement with observations. We found that a total of 222 km(3) water entered the Baltic in January: the salinity of 94 km(3) was greater than 17 PSU. In August/September 2002 the outflow through the Sound and inflow across the Darss Sill were simulated. The net inflow volume amounted to about 50 km(3).

  • 274.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Coward, Andrew C.
    James Renell Div,. Southhampton Oceanogr. Centre.
    Nycander, Jonas
    MISU.
    Döös, Kristofer
    MISU.
    RCO – Rossby Centre regional Ocean climate model: model description (version 1.0) and first results from the hindcast period 1992/931999Report (Other academic)
    Abstract [en]

    Within SWECLIM a 3D fully coupled ice-ocean model has been developed based on the massively parallel OCCAM code from Southampton. Compared to the global OCCAM the model has to be adopted to Baltic Sea conditions with implementations of high-frequent atmospheric forcing fields in connection with adequate bulk formulae for wind stress, heat uxes and freshwater uxes, solar radiation, river runoff, active open boundary conditions, a second-order moment turbulence closure scheme and a dynamic-thermodynamic sea ice model. Thereby, state-of-the-art sub-models and parameterizations have been used. RCO is the first 3D coupled ice-ocean model for the Baltic Sea with the above mentioned specifications suitable for use on mpp computers like CRAY-T3E's. Thus, a milestone for 3D ocean model development has been set. No other model is as fast as RCO. The performance has been improved significantly using advanced algorithms to optimize processor maps. This guarantees work load balance between the different processors. From now on it is possible to perform longterm simulations (10 years) within SWECLIM using a sufficiently resolved 3D Baltic Sea model. The open boundary conditions have been tested. They allow waves to radiate out of the model domain and signals prescribed at the border to in uence the model interior. No significant trends (like emptying or filling) have been observed which might prevent longer integrations of the system. An option has been included in RCO for active open boundary conditions also for temperature and salinity. For the first time the turbulence closure model has been tested within a 3D model in all Baltic sub-basins. The new flux boundary conditions for turbulent kinetic energy parameterizing breaking surface waves perform well. First results for the hindcast period 1992/93 are presented. Therefor, realistic atmospheric, runoff and boundary data have been used. The model is initialized using observed profile temperature and salinity data. A spin-up period of 3 months starting in May is sufficient to smooth out artificial gradients from the initialization procedure and to turn in basin wide volume changes correctly. The model results have been compared to sea level, sea surface temperature, temperature/salinity profile and ice thickness/compactness data with good agreement. Basin wide volume changes as well as daily sea level oscillations are simulated surprisingly good. Sea surface temperatures follow the observed seasonal cycle. Up- and downwelling events in RCO occur as observed with the right frequency and area extent but the sst's tend to be colder in upwelling and warmer in downwelling regions compared to observations. Mixed layer depths, which are important for the ocean heat content, agree well with previous model studies which are validated against observations intensively (Meier, 1996). The water exchange between Baltic and North Sea crucial for multi-year integrations is modelled realistically. Especially the salt water inflow in January 1993 can be reproduced. The bottom water in Bornholm Basin is replaced by new water originating from the North Sea but maximum observed bottom salinities at Bornholm Deep are underestimated by 1-2 PSU. Freezing, breakup date and maximum ice extent are in good correspondence with observations. Improved parameterizations result in modelled ice thicknesses as observed whereas other authors report too large ice thicknesses and delayed ice melting (e.g., Haapala and Lepparanta,1996). Multi-year simulations including mild, normal and severe winters will be necessary to elucidate this problem further. A comparison between an experiment with full dynamic-thermodynamics and one without dynamic effects reveals the importance of ice advection under wind influence. A process study from the beginning of February 1993 showed that under strong wind conditions a hole in the ice coverage can open with the size of half of the Bothnian Bay. At the end of January 1993 the Bothnian Bay, the coastal area of the Bothnian Sea and the eastern parts of the Gulf of Finland are ice covered. A couple of days later westerly winds led to wide open areas in the western Bothnian Bay while ice piled up at the eastern coasts to a correct amount. This phenomenon can be modelled only with ice dynamics included. The aim of SWECLIM is to increase our knowledge of the effects of climate change in Sweden and the other Nordic countries. Therefor, it is necessary to understand the present climate. For the Baltic Sea even the knowledge about the present mean state and its transients is rather poor. Only a small number of long-time observations like sea level records (for example from Stockholm, see Ekman (1988)), maximum annual ice extent (e.g., Palosuo, 1953; Seina and Palosuo, 1993) or temperature and salinityprofiles from monitoring stations in some of the sub-basins (e.g., Matthaus and Frank,1992) are available. These informations are not enough to understand the driving mechanisms of mean horizontal and vertical transports of energy, momentum and matter. 3D Baltic Sea models like RCO will close this knowledge gap in future. Thereby, it will be possible to close the water and energy cycle of the Baltic catchment area, a final goal of BALTEX. By applying atmospheric forcing data from scenario simulations in one- or two-way coupled mode it will be possible to make predictions of climate change for the Baltic Sea. Impact studies of the future marine environment will be available using detailed highly resolved information from RCO. This report presents a powerful tool for solving these and other tasks.

  • 275.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Faxen, T
    A multiprocessor coupled ice-ocean model for the Baltic Sea: Application to salt inflow2003In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 108, no C8, article id 3273Article in journal (Refereed)
    Abstract [en]

    Within the Swedish Regional Climate Modeling Program, SWECLIM, a three-dimensional (3-D) coupled ice-ocean model for the Baltic Sea has been developed to simulate physical processes on timescales of hours to decades. The code has been developed based on the massively parallel version of the Ocean Circulation Climate Advanced Modeling (OCCAM) project of the Bryan-Cox-Semtner model. An elastic-viscous-plastic ice rheology is employed, resulting in a fully explicit numerical scheme that improves computational efficiency. An improved two-equation turbulence model has been embedded to simulate the seasonal cycle of surface mixed layer depths as well as deepwater mixing on decadal timescale. The model has open boundaries in the northern Kattegat and is forced with realistic atmospheric fields and river runoff. Optimized computational performance and advanced algorithms to calculate processor maps make the code fast and suitable for multi-year, high-resolution simulations. As test cases, the major salt water inflow event in January 1993 and the stagnation period 1980-1992, have been selected. The agreement between model results and observations is regarded as good. Especially, the time evolution of the halocline in the Baltic proper is realistically simulated also for the longer period without flux correction, data assimilation, or reinitialization. However, in particular, smaller salt water inflows into the Bornholm Basin are underestimated, independent of the horizontal model resolution used. It is suggested that the mixing parameterization still needs improvements. In addition, a series of process studies of the inflow period 1992/1993 have been performed to show the impact of river runoff, wind speed, and sea level in Kattegat. Natural interannual runoff variations control salt water inflows into the Bornholm Basin effectively. The effect of wind speed variation on the salt water flux from the Arkona Basin to the Bornholm Basin is minor.

  • 276.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Halkka, A
    Simulated distributions of Baltic Sea-ice in warming climate and consequences for the winter habitat of the Baltic ringed seal2004In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 33, no 4-5, p. 249-256Article in journal (Refereed)
    Abstract [en]

    Sea-ice in the Baltic Sea in present and future climates is investigated. The Rossby Centre Regional Atmosphere-Ocean model was used to perform a set of 30-year-long time slice experiments. For each of the two driving global models HadAM3H and ECHAM4/OPYC3, one control run (1961-1990) and two scenario runs (2071-2100) based upon the SIRES A2 and B2 emission scenarios were conducted. The future sea-ice volume in the Baltic Sea is reduced by 83% on average. The Bothnian Sea, large areas of the Gulf of Finland and Gulf of Riga, and the outer parts of the southwestern archipelago of Finland will become ice-free in the mean. The presented scenarios are used to study the impact of climate change on the Baltic ringed seal (Phoca hispida botnica). Climate change seems to be a major threat to all southern populations. The only fairly good winter sea-ice habitat is found to be confined to the Bay of Bothnia.

  • 277.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Modelling the changing climate of the Baltic Sea.2006Report (Other academic)
  • 278.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Graham, Phil
    SMHI, Research Department, Climate research - Rossby Centre.
    Estimating uncertainties of projected Baltic Sea salinity in the late 21st century2006In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 33, no 15, article id L15705Article in journal (Refereed)
    Abstract [en]

    As the uncertainty of projected precipitation and wind changes in regional climate change scenario simulations over Europe for the late 21st century is large, we applied a multi-model ensemble approach using 16 scenario simulations based upon seven regional models, five global models, and two emission scenarios to gain confidence in projected salinity changes in the Baltic Sea. In the dynamical downscaling approach a regional ocean circulation model and a large-scale hydrological model for the entire Baltic Sea catchment area were used. Despite the uncertainties, mainly caused by global model biases, salinity changes in all projections are either negative or not statistically significant in terms of natural variability.

  • 279. Menendez, C. G.
    et al.
    de Castro, M.
    Boulanger, J. -P
    D'Onofrio, A.
    Sanchez, E.
    Soerensson, A. A.
    Blazquez, J.
    Elizalde, A.
    Jacob, D.
    Le Treut, H.
    Li, Z. X.
    Nunez, M. N.
    Pessacg, N.
    Pfeiffer, S.
    Rojas, M.
    Rolla, A.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Solman, S. A.
    Teichmann, C.
    Downscaling extreme month-long anomalies in southern South America2010In: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 98, no 3-4, p. 379-403Article in journal (Refereed)
    Abstract [en]

    We investigate the performance of one stretched-grid atmospheric global model, five different regional climate models and a statistical downscaling technique in simulating 3 months (January 1971, November 1986, July 1996) characterized by anomalous climate conditions in the southern La Plata Basin. Models were driven by reanalysis (ERA-40). The analysis has emphasized on the simulation of the precipitation over land and has provided a quantification of the biases of and scatter between the different regional simulations. Most but not all dynamical models underpredict precipitation amounts in south eastern South America during the three periods. Results suggest that models have regime dependence, performing better for some conditions than others. The models' ensemble and the statistical technique succeed in reproducing the overall observed frequency of daily precipitation for all periods. But most models tend to underestimate the frequency of dry days and overestimate the amount of light rainfall days. The number of events with strong or heavy precipitation tends to be under simulated by the models.

  • 280. Miao, J F
    et al.
    Chen, D
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Modelling subgrid scale dry deposition velocity of O-3 over the Swedish west coast with MM5-PX model2006In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 40, no 3, p. 415-429Article in journal (Refereed)
    Abstract [en]

    A mesoscale meteorological model (MM5) coupled with an advanced land surface model (PX LSM) is used in this study to model high-resolution (2 km) dry deposition velocity of ozone over the Swedish west coast, together with a newly revised dry deposition parameterization for air-quality models with emphasis on non-stomatal resistance. The important air-surface exchange processes for air quality (surface fluxes of heat, moisture and momentum) are also simulated by this model. The modelled subgrid scale variability of the dry deposition velocity and its dependence on land use, terrain height and synoptic conditions are investigated. It is found that a systematic difference in the deposition velocity modelled by different resolutions exists, and the difference varies diurnally and daily. The subgrid scale variation is significant, which has a clear impact on the area-averaged deposition velocity. The deposition velocity depends strongly on land use and weather conditions, but not on topography for the area studied. Meteorological conditions at subgrid scales play an important role in determining the deposition velocity. It is also concluded that the dry deposition velocity simulated in this study is reasonable, and that a 6-km resolution would be practically good enough to resolve the inhomogeneity of the surface properties for dry deposition studies in this area. The variation range of dry deposition velocity over different land use categories and the corresponding resistances are outlined. Moreover, the difference in the estimated dry deposition velocitiy between the methods using fractional land use and using dominant land use is compared. (c) 2005 Elsevier Ltd. All rights reserved.

  • 281. Miao, J. -F
    et al.
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Chen, D.
    Ritchie, H.
    Impacts of boundary layer turbulence and land surface process parameterizations on simulated sea breeze characteristics2009In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, no 6, p. 2303-2320Article in journal (Refereed)
    Abstract [en]

    This paper investigates the sensitivity of sea breeze (SB) simulations to combinations of boundary-layer turbulence and land-surface process parameterizations implemented in the MM5 mesoscale meteorological mode for an observed SB case over the Swedish west coast. Various combinations from four different planetary boundary layer (PBL) schemes [Blackadar, Gayno-Seaman (GS), Eta, MRF], and two land surface model (LSM) schemes (SLAB, Noah) with different complexity are designed to simulate a typical SB case over the Swedish west coast. The simulations are conducted using two-way interactively nested grids. Simulated 10-m winds are compared against observed near-surface wind data from the GOTE2001 campaign to examine the diurnal cycle of wind direction and speed for SB timing. The SB (vertical) circulation is also compared in the different experiments. The results show that the different combinations of PBL and LSM parameterization schemes result in different SB timing and vertical circulation characteristics. All experiments predict a delayed SB. The vertical component of the SB circulation varies in the experiments, among which the GS PBL scheme produces the strongest SB circulation. Evident differences between the SLAB and Noah LSMs are also found, especially in maximum of updraft and downdraft velocities of the SB vertical circulation. The results have significant implications for convective initiation, air quality studies and other environmental problems in coastal areas.

  • 282.
    Michelson, Daniel
    et al.
    SMHI, Core Services.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Landelius, Tomas
    SMHI, Research Department, Atmospheric remote sensing.
    Collier, C G
    Haase, Gunther
    SMHI, Research Department, Atmospheric remote sensing.
    Heen, M
    'Down-to-Earth' modelling of equivalent surface precipitation using multisource data and radar2005In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 131, no 607, p. 1093-1112Article in journal (Refereed)
    Abstract [en]

    The estimation of surface rainfall from reflectivity data derived from weather radar has been much studied over many years. It is now clear that central to this problem is the adjustment of these data for the impacts of vertical variations in the reflectivity. In this paper a new procedure (known as Down-to-Earth, DTE) is proposed and tested for combining radar measurements aloft with information from a numerical weather-prediction (NWP) model and an analysis system. The procedure involves the exploitation of moist cloud physics in an attempt to account for physical processes impacting on precipitation during its descent from the height of radar echo measurements to the surface. The application of DTE leads to increased underestimation in the radar measurements compared to precipitation gauge observations at short and intermediate radar ranges (0-120 km), but is successful at reducing the bias at further ranges. However the application of DTE does not lead to significant decreases in the random error of the surface rain rate estimate. No improvement is made when attempting to account for the precipitation phase measured by radar. It is concluded that further work on radar data quality control, along with improvements to the NWP model, are essential to improve upon results using such a physically based procedure.

  • 283.
    Michelson, Daniel
    et al.
    SMHI, Core Services.
    Landelius, Tomas
    SMHI, Research Department, Atmospheric remote sensing.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Collier, C. G.
    Attempts to parameterize cloud water profiles using a neural network2004In: Atmospheric Science Letters, ISSN 1530-261X, E-ISSN 1530-261X, Vol. 5, no 7, p. 141-145Article in journal (Refereed)
    Abstract [en]

    Atmospheric state variables from a Numerical Weather Prediction (NWP) model are combined with analyzed cloud base heights in a neural network, with the objective to model corresponding cloud water profiles. It was found that the neural network was incapable of resolving the inherently non-linear vertical cloud water distributions. Copyright (C) 2004 Royal Meteorological Society

  • 284. Miranda, A.I
    et al.
    Martins, Helena
    SMHI, Research Department, Climate research - Rossby Centre.
    Valente, J.
    Amorim, Jorge Humberto
    SMHI, Research Department, Air quality.
    Borrego, C.
    Tavares, R.
    Samson, R.
    del Amo, R.A.
    Case Studies: Modeling the Atmospheric Benefits of Urban Greening2017In: The Urban Forest - Cultivating Green Infrastructure for People and the Environment / [ed] D. Pearlmutter, C. Calfapietra, R. Samson, L. O'Brien, S.K. Ostoić, G. Sanesi, R.A. del Amo, Springer International Publishing , 2017, p. 89-99Chapter in book (Refereed)
  • 285.
    Moberg, Anders
    et al.
    Department of Physical Geography and Quaternary Geology, Stockholm University Department of Meteorology, Stockholm University.
    Gouirand, Isabelle
    Department of Physical Geography and Quaternary Geology, Stockholm University .
    Schoning, Kristian
    Department of Physical Geography and Quaternary Geology, Stockholm University .
    Wohlfarth, Barbara
    Department of Physical Geography and Quaternary Geology, Stockholm University.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    de Jong, Rixt
    Department of Quaternary Geology, Lund University.
    Linderholm, Hans
    Department of Earth Sciences, Göteborg University .
    Zorita, Eduardo
    GKSS Research Centre, Geesthacht, Germany.
    Climate in Sweden during the past millennium – Evidence from proxy data, instrumental data and model simulations2006Report (Other academic)
  • 286.
    Moen, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    A multi-level quasi-geostrophic model for short range weather predictions1975Report (Other academic)
    Abstract [en]

    A quite generally formulated multilevel quasi-geostrophic medel with possibilities to include second order terms in the vorticity equation is derived. The model includes friction, topography, latent heat and sensible heat. The treatment of the variable boundary conditions, smoothing and ellipticity control is described.

  • 287. Moore, Karen
    et al.
    Pierson, Donald
    Pettersson, Kurt
    Schneiderman, Elliot
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Effects of warmer world scenarios on hydrologic inputs to Lake Malaren, Sweden and implications for nutrient loads2008In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 599, p. 191-199Article in journal (Refereed)
    Abstract [en]

    A simple, rapid, and flexible modelling approach was applied to explore the impacts of climate change on hydrologic inputs and consequent implications for nutrient loading to Lake Malaren, Sweden using a loading function model (GWLF). The first step in the process was to adapt the model for use in a large and complex Swedish catchment. We focused on the Galten basin with four rivers draining into the western region of Malaren. The catchment model was calibrated and tested using long-term historical data for river discharge and dissolved nutrients (N, P). Then multiple regional climate model simulation results were downscaled to the local catchment level, and used to simulate possible hydrological and nutrient loading responses to warmer world scenarios. Climate change projections for the rivers of Galten basin show profound changes in the timing of discharge and nutrient delivery due to increased winter precipitation and earlier snow melt. Impacts on total annual discharge and load are minimal, but the alteration in river flow regime and the timing of nutrient delivery for future climate scenarios is strikingly different from historical conditions.

  • 288. Moseley, Christopher
    et al.
    Berg, Peter
    SMHI, Research Department, Climate research - Rossby Centre.
    Haerter, Jan O.
    Probing the precipitation life cycle by iterative rain cell tracking2013In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 118, no 24, p. 13361-13370Article in journal (Refereed)
    Abstract [en]

    Monitoring the life cycle of convective rain cells requires a Lagrangian viewpoint where the observer moves with the dominant background flow. To adopt such a moving reference frame, we design, validate, and apply a simple rain cell tracking methodwhich we term iterative rain cell tracking (IRT)for spatio-temporal precipitation data. IRT iteratively identifies the formation and dissipation of rain cells and determines the large-scale flow. The iteration is repeated until reaching convergence. As validated using reanalysis wind speeds, repeated iterations lead to substantially increased agreement of the background flow field and an increased number of complete tracks. Our method is thereby able to monitor the growth and intensity profiles of rain cells and is applied to a high-resolution (5 min and 1x1 km(2)) data set of radar-derived rainfall intensities over Germany. We then combine this data set with surface temperature observations and synoptic observations to group tracks according to convective and stratiform conditions. Convective tracks show clear life cycles in intensity, with peaks shifted off-center toward the beginning of the track, whereas stratiform tracks have comparatively featureless intensity profiles. Our results show that the convective life cycle can lead to convection-dominating precipitation extremes at short time scales, while track-mean intensities may vary much less between the two types. The observed features become more pronounced as surface temperature increases, and in the case of convection even exceeded the rates expected from the Clausius-Clapeyron relation.

  • 289. Napoly, Adrien
    et al.
    Boone, Aaron
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Gollvik, Stefan
    SMHI.
    Martin, Eric
    Seferian, Roland
    Carrer, Dominique
    Decharme, Bertrand
    Jarlan, Lionel
    The interactions between soil-biosphere-atmosphere (ISBA) land surface model multi-energy balance (MEB) option in SURFEXv8-Part 2: Introduction of a litter formulation and model evaluation for local-scale forest sites2017In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 10, no 4, p. 1621-1644Article in journal (Refereed)
  • 290. Naumann, G.
    et al.
    Alfieri, L.
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Mentaschi, L.
    Betts, R. A.
    Carrao, H.
    Spinoni, J.
    Vogt, J.
    Feyen, L.
    Global Changes in Drought Conditions Under Different Levels of Warming2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 7, p. 3285-3296Article in journal (Refereed)
  • 291. Navarro-Ortega, Alicia
    et al.
    Acuna, Vicenc
    Bellin, Alberto
    Burek, Peter
    Cassiani, Giorgio
    Choukr-Allah, Redouane
    Doledec, Sylvain
    Elosegi, Arturo
    Ferrari, Federico
    Ginebreda, Antoni
    Grathwohl, Peter
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Rault, Philippe Ker
    Kok, Kasper
    Koundouri, Phoebe
    Ludwig, Ralf Peter
    Merz, Ralf
    Milacic, Radmila
    Munoz, Isabel
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Paniconi, Claudio
    Paunovic, Momir
    Petrovic, Mira
    Sabater, Laia
    Sabater, Sergi
    Skoulikidis, Nikolaos Th.
    Slob, Adriaan
    Teutsch, Georg
    Voulvoulis, Nikolaos
    Barcelo, Damia
    Managing the effects of multiple stressors on aquatic ecosystems under water scarcity. The GLOBAQUA project2015In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 503, p. 3-9Article in journal (Refereed)
    Abstract [en]

    Water scarcity is a serious environmental problem in many European regions, and will likely increase in the near future as a consequence of increased abstraction and climate change. Water scarcity exacerbates the effects of multiple stressors, and thus results in decreased water quality. It impacts river ecosystems, threatens the services they provide, and it will force managers and policy-makers to change their current practices. The EU-FP7 project GLOBAQUA aims at identifying the prevalence, interaction and linkages between stressors, and to assess their effects on the chemical and ecological status of freshwater ecosystems in order to improve water management practice and policies. GLOBAQUA assembles a multidisciplinary team of 21 European plus 2 non-European scientific institutions, as well as water authorities and river basin managers. The project includes experts in hydrology, chemistry, biology, geomorphology, modelling, socio-economics, governance science, knowledge brokerage, and policy advocacy. GLOBAQUA studies six river basins (Ebro, Adige, Sava, Evrotas, Anglian and Souss Massa) affected by water scarcity, and aims to answer the following questions: how does water scarcity interact with other existing stressors in the study river basins? How will these interactions change according to the different scenarios of future global change? Which will be the foreseeable consequences for river ecosystems? How will these in turn affect the services the ecosystems provide? How should management and policies be adapted to minimise the ecological, economic and societal consequences? These questions will be approached by combining data-mining, field- and laboratory-based research, and modelling. Here, we outline the general structure of the project and the activities to be conducted within the fourteen work-packages of GLOBAQUA. (C) 2014 The Authors. Published by Elsevier B.V.

  • 292. Nijssen, B
    et al.
    Bowling, L C
    Lettenmaier, D P
    Clark, D B
    El Maayar, M
    Essery, R
    Goers, S
    Gusev, Y M
    Habets, F
    van den Hurk, B
    Jin, J M
    Kahan, D
    Lohmann, D
    Ma, X Y
    Mahanama, S
    Mocko, D
    Nasonova, O
    Niu, G Y
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Schmakin, A B
    Takata, K
    Verseghy, D
    Viterbo, P
    Xia, Y L
    Xue, Y K
    Yang, Z L
    Simulation of high latitude hydrological processes in the Torne-Kalix basin: PILPS phase 2(e) - 2: Comparison of model results with observations2003In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 38, no 1-2, p. 31-53Article in journal (Refereed)
  • 293. Nik, Vahid M.
    et al.
    Kalagasidis, Angela Sasic
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Assessment of hygrothermal performance and mould growth risk in ventilated attics in respect to possible climate changes in Sweden2012In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 55, p. 96-109Article in journal (Refereed)
    Abstract [en]

    Most of the last 20 years in Sweden have been mild and wet compared to the 1961-1990 climate reference period. After a few relatively cold years in the mid-1980s, practically all years have been warmer than the preceding 30 years average. During the indicated period, an increase of moisture-related problems (mould growth) was observed in ventilated attics, a moisture sensitive building part. This work investigates hygrothermal performance of ventilated attics in respect to possible climate change. Hygrothermal simulations of attics were performed numerically in Matlab. Four attic constructions are investigated - a conventional attic and three alternative constructions suggested by practitioners. Simulations were done for the period of 1961-2100 using the weather data of RCA3 climate model. Effects of three different emissions scenarios are considered. Hygrothermal conditions in the attic are assessed using a mould growth model. Based on the results the highest risk of mould growth was found on the north roof of the attic in Gothenburg, Sweden. Results point to increment of the moisture problems in attics in future. Different emissions scenarios do not influence the risk of mould growth inside the attic due to compensating changes in different variables. Assessing the future performance of the four attics shows that the safe solution is to ventilate the attic mechanically, though this solution inevitably requires extra use of electrical energy for running the fan. Insulating roofs of the attic can decrease the condensation on roofs, but it cannot decrease the risk of mould growth considerably, on the wooden roof underlay. (C) 2012 Elsevier Ltd. All rights reserved.

  • 294. Nik, Vahid M.
    et al.
    Kalagasidis, Angela Sasic
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Statistical methods for assessing and analysing the building performance in respect to the future climate2012In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 53, p. 107-118Article in journal (Refereed)
    Abstract [en]

    Global warming and its effects on climate are of great concern. Climate change can affect buildings in different ways. Increased structural loads from wind and water, changes in energy need and decreased moisture durability of materials are some examples of the consequences. Future climate conditions are simulated by global climate models (GCMs). Downscaling by regional climate models (RCMs) provides weather data with suitable temporal and spatial resolutions for direct use in building simulations. There are two major challenges when the future climate data are used in building simulations. The first is to handle and analyse the huge amount of data. The second challenge is to assess the uncertainties in building simulations as a consequence of uncertainties in the future climate data. In this paper two statistical methods, which have been adopted from climatology, are introduced. Applications of the methods are illustrated by looking into two uncertainty factors of the future climate; operating RCMs at different spatial resolutions and with boundary data from different GCMs. The Ferro hypothesis is introduced as a nonparametric method for comparing data at different spatial resolutions. The method is quick and subtle enough to make the comparison. The parametric method of decomposition of variabilities is described and its application in data assessment is shown by considering RCM data forced by different GCMs. The method enables to study data and its variations in different time scales. It provides a useful summary about data and its variations which makes the comparison between several data sets easier. (C) 2012 Elsevier Ltd. All rights reserved.

  • 295.
    Nikulin, Grigory
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Giorgi, Filippo
    Asrar, Ghassem
    Buechner, Matthias
    Cerezo-Mota, Ruth
    Christensen, Ole Bossing
    Deque, Michel
    Fernandez, Jesus
    Haensler, Andreas
    van Meijgaard, Erik
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Sylla, Mouhamadou Bamba
    Sushama, Laxmi
    Precipitation Climatology in an Ensemble of CORDEX-Africa Regional Climate Simulations2012In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 25, no 18, p. 6057-6078Article in journal (Refereed)
    Abstract [en]

    An ensemble of regional climate simulations is analyzed to evaluate the ability of 10 regional climate models (RCMs) and their ensemble average to simulate precipitation over Africa. All RCMs use a similar domain and spatial resolution of similar to 50 km and are driven by the ECMWF Interim Re-Analysis (ERA-Interim) (1989-2008). They constitute the first set of simulations in the Coordinated Regional Downscaling Experiment in Africa (CORDEX-Africa) project. Simulated precipitation is evaluated at a range of time scales, including seasonal means, and annual and diurnal cycles, against a number of detailed observational datasets. All RCMs simulate the seasonal mean and annual cycle quite accurately, although individual models can exhibit significant biases in some subregions and seasons. The multimodel average generally outperforms any individual simulation, showing biases of similar magnitude to differences across a number of observational datasets. Moreover, many of the RCMs significantly improve the precipitation climate compared to that from their boundary condition dataset, that is, ERA-Interim. A common problem in the majority of the RCMs is that precipitation is triggered too early during the diurnal cycle, although a small subset of models does have a reasonable representation of the phase of the diurnal cycle. The systematic bias in the diurnal cycle is not improved when the ensemble mean is considered. Based on this performance analysis, it is assessed that the present set of RCMs can be used to provide useful information on climate projections over Africa.

  • 296.
    Nikulin, Grigory
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Evaluation of temperature extremes from an ensemble of transient RCM simulations driven by several AOGCMs2009Conference paper (Other academic)
  • 297.
    Nikulin, Grigory
    et al.
    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.
    Changes in daily temperature variability over Europe from an ensemble of RCM simulations driven by several AOGCMs2009Conference paper (Other academic)
  • 298.
    Nikulin, Grigory
    et al.
    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.
    Changes in daily temperature variability over Europe from an ensemble of regional climate simulations driven by several AOGCMs.2009Conference paper (Other academic)
  • 299.
    Nikulin, Grigory
    et al.
    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.
    Intraseasonal temperature variability over Europe in a future climate scenario2008In: Abstracts of the contributions of the EGU General Assembly 2008., 2008, Vol. 10, article id EGU2008-A-09248Conference paper (Other academic)
  • 300.
    Nikulin, Grigory
    et al.
    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.
    Projected changes in daily temperature variability over Europe in an ensemble of RCM simulations2009Conference paper (Other academic)
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