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  • 1.
    Doescher, Ralf
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Willen, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Rutgersson, Anna
    SMHI, Research Department, Climate research - Rossby Centre.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Hansson, Ulf
    SMHI, Research Department, Climate research - Rossby Centre.
    Graham, Phil
    SMHI, Research Department, Climate research - Rossby Centre.
    The development of the regional coupled ocean-atmosphere model RCAO2002In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 7, no 3, p. 183-192Article in journal (Refereed)
    Abstract [en]

    A regional coupled ocean-atmosphere-ice general circulation model for northern Europe is introduced for climate study purposes. The Baltic Sea is interactively coupled. The coupled model is validated in a 5-year hind-cast experiment with a focus on surface quantities and atmosphere-ocean heat fluxes. The coupled sea surface temperature matches observations well. The system is free of drift, does not need flux corrections and is suitable for multi-year climate runs. With flux forcing from the atmospheric model the regional ocean model gives sea surface temperatures statistically equivalent to the uncoupled ocean model forced by observations. Other oceanic surface quantities do not reach this quality in combination with the current atmosphere model. A strong dependence of sea ice extent on details of the atmospheric radiation scheme is found. Our standard scheme leads to an overestimation of ice, most likely due to a negative bias of long-wave radiation. There is indication that a latent heat flux bias in fall contributes to the ice problem. Other atmosphere-ocean heat fluxes are generally realistic in the long term mean.

  • 2. Enmar, Linda
    et al.
    Lake, Irene
    SMHI, Research Department, Oceanography.
    Lundberg, Peter
    Sigray, Peter
    A note on ADCP-based indirect observations of turbulence2016In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 21, no 1-2, p. 44-52Article in journal (Refereed)
    Abstract [en]

    A 70-day data set from bottom-mounted ADCPs on the two sides of the Faroe-Bank Channel was analysed using the recorded flow variance and echo intensity in the deeper reaches of the passage as proxies for turbulence. A consistent picture emerged, not least since the data losses (which were ascribed to turbulence-induced activation of the fish-elimination option in the ADCP software) could be shown to co-vary with the internal M-2 tide affecting the vertical shear, which in turn proved to be correlated with the flow variance.

  • 3. Enmar, Linda
    et al.
    Lake, Irene
    SMHI, Research Department.
    Lundberg, Peter
    Sigray, Peter
    A note on ADCP-based indirect observations of turbulence2016In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 21, no 1-2, p. 44-52Article in journal (Refereed)
  • 4. Fortelius, C
    et al.
    Andrae, Ulf
    SMHI, Research Department, Meteorology.
    Forsblom, M
    The BALTEX regional reanalysis project2002In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 7, no 3, p. 193-201Article in journal (Refereed)
    Abstract [en]

    The BALTEX regional reassimilation project uses meteorological data assimilation for quantifying the climatic energy and water cycles over the catchment basin of the Baltic Sea during the course of one annual cycle, Sep. 1999-Oct. 2000. This report presents the data assimilation system used, the available products, and a sample of preliminary results. The latter demonstrate that the system is capable of simulating the essential features of the energy and water cycles of the Baltic drainage basin. We find this encouraging, because the model has not been tuned to reproduce these cycles, but mainly to predict the atmospheric state.

  • 5.
    Graham, Phil
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Rosberg, Jörgen
    SMHI, Research Department, Hydrology.
    Hellström, Sara-Sofia
    SMHI, Research Department, Hydrology.
    Berndtsson, Ronny
    Simulating river flow to the Baltic Sea from climate simulations over the past millennium2009In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 14, no 1, p. 173-182Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to reconstruct river flow to the Baltic Sea using data from different periods during the past thousand years. A hydrological model coupled to simulations from climate models was used to estimate river flow. A "millennium" simulation of past climate from the ECHO-G coupled atmosphere-ocean global climate model provided climatological inputs. Results from this global model were downscaled with the RCA3 regional climate model over northern Europe. Temperature and precipitation from the downscaled simulation results were then used in the HBV hydrological model to simulate river flows to the Baltic Sea for the periods 1000-1199 and 1551-1929. These were compared with observations for the period 1921-2002. A general conclusion from this work is that although climate has varied during the past millennium, variability in annual river flow to the Baltic Sea does not appear more pronounced in recent years than during the previous millennium, or vice versa.

  • 6.
    Höglund, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Ice conditions for maritime traffic in the Baltic Sea in future climate2017In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 22, p. 245-265Article in journal (Refereed)
  • 7. Jonsson, Oskar
    et al.
    Andersson, Camilla
    SMHI, Research Department, Air quality.
    Forsberg, Bertil
    Johansson, Christer
    Air pollution episodes in Stockholm regional background air due to sources in Europe and their effects on human population2013In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 18, no 3-4, p. 280-302Article in journal (Refereed)
    Abstract [en]

    Using air quality measurements, we categorized air pollution according to source sectors in a rural background environment in southern Sweden based on hourly air-mass backward trajectories during 1997-2010. Concentrations of fine (PM2.5) and sum of fine and coarse particulate matter (PM10), accumulation mode particle number, black carbon and surface ozone were 4.0, 3.9, 4.5, 6.8 and 1.3 times higher, respectively, in air masses from the southeast as compared with those in air masses from the cleanest sector in the northwest, consistent with air-mass transport over areas with relatively high emissions of primary particulate matter (PM) and secondary PM precursors. The highest ultrafine particle numbers were associated with clean air from the northwest. We estimate that almost 7.8% and 0.6% higher premature human mortality is caused by PM2.5 and ozone exposure, respectively, when air originates from the southeast as compared with that when air originates from the northwest. Reductions of emissions in eastern Europe would reduce the highest air pollution concentrations and associated health risks. However, since air masses from the southwest are more frequent, emissions in the western part of Europe are more important for annual mean premature mortality.

  • 8.
    Kjellström, Erik
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Lind, Petter
    SMHI, Research Department, Climate research - Rossby Centre.
    Changes in the water budget in the Baltic Sea drainage basin in future warmer climates as simulated by the regional climate model RCA32009In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 14, no 1, p. 114-124Article in journal (Refereed)
    Abstract [en]

    In this study we investigate three different regional climate change scenarios with respect to changes in the water budget over the Baltic Sea drainage basin. The scenarios are transient climate change scenarios in which the regional climate model RCA3 has been used to downscale results from two general circulation models, with three different emissions scenarios, for the years 1961-2100. First we show that the control climate in the late 20th century is too wet as compared with observations. This wet bias in the simulations is partly attributable to biases in the forcing global models but is also amplified in the regional climate model. The future climate change signal shows a gradually warmer and wetter climate during the 21st century with increased moisture transport into the region via the atmosphere. This leads to an intensification of the hydrological cycle with more precipitation and evaporation. The net precipitation increases in all scenarios in the entire region. The changes are of the order 15%-20% for annual and areal mean fluxes.

  • 9. Koistinen, J
    et al.
    Michelson, Daniel
    SMHI, Core Services.
    BALTEX weather radar-based precipitation products and their accuracies2002In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 7, no 3, p. 253-263Article in journal (Refereed)
    Abstract [en]

    This paper briefly reviews the measurement of precipitation by radar, discusses factors affecting the accuracy of such measurements, and outlines how such factors may be dealt with to improve the quality of precipitation measurements by radar for the purposes of the Baltic Sea Experiment (BALTEX). Precipitation products from the BALTEX Radar Network (BALTRAD) are then briefly presented, along with descriptions of how their qualities are improved, as are some new results on their accuracies. Intelligent compositing of data from a heterogeneous network, combined with innovative quality control, is shown to give high quality high resolution information for monitoring relative precipitation variability simultaneously over land and sea in both time and space. Gauge adjustment of radar-derived accumulated precipitation is shown to efficiently minimize the radar data's bias with increasing distance, thus yielding quantitatively useful datasets for application by the BALTEX community.

  • 10.
    Langner, Joakim
    et al.
    SMHI, Research Department, Air quality.
    Andersson, Camilla
    SMHI, Research Department, Air quality.
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Atmospheric input of nitrogen to the Baltic Sea basin: present situation, variability due to meteorology and impact of climate change2009In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 14, no 1, p. 226-237Article in journal (Refereed)
    Abstract [en]

    We present estimates of the present and future deposition of atmospheric nitrogen into the Baltic Sea made using the Eulerian chemical transport model MATCH, and compare these with earlier model estimates. The average total nitrogen deposition for periods of five to ten years from 1992 to 2001 was estimated to be in the range of 261-300 Gg N yr(-1). The deposition across the whole catchment area for 2001 was estimated to be 1.55-1.73 Tg N yr(-1). Inter-annual variability of nitrogen deposition into the Baltic Sea was calculated to be in the range of 5.1%-8.0%. Investigating one climate change scenario using emissions for year 2000 indicated a rather small impact on total deposition of nitrogen due to climate change, i.e. increase of total nitrogen deposition by similar to 5% by the end of the 21st century as compared with present conditions. The combined effect of climate change and future changes in anthropogenic emissions of nitrogen to the atmosphere remains an open question. Additional climate change scenarios using different combinations of global and regional climate models and greenhouse gas emission scenarios need to be explored.

  • 11.
    Lind, Petter
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Water budget in the Baltic Sea drainage basin: Evaluation of simulated fluxes in a regional climate model2009In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 14, no 1, p. 56-67Article in journal (Refereed)
    Abstract [en]

    We investigated the Rossby Centre regional climate model, RCA3, and its ability to reproduce the water budget of the Baltic Sea drainage basin during the period from 1979 to 2002. The model was forced on its lateral boundaries with European Centre for Medium-Range Weather Forecasts Re-Analysis data, ERA40. Simulated long-term means and inter-annual variability were compared with observational records and model-derived data. The basin-wide water fluxes were broadly captured by the model, and annual mean net precipitation over land agreed well (i.e., within 5%) with observed total discharge to the Baltic Sea. Long-term annual means of precipitation were around 20% higher in RCA3 compared with reference data, the differences being in most months statistically significant at the 5% level. On the other hand, differences between the reference datasets were evident and in most months also statistically significant. The inclusion of a high-resolution dataset showed a close agreement compared with RCA3; differences were less than 5% in the long-term annual mean. Therefore, more high-resolution observational datasets, especially for evaporation and runoff, are required to refine the water budget and compare water fluxes on sub-regional and local scales.

  • 12.
    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.

  • 13. Myrberg, Kai
    et al.
    Ryabchenko, Vladimir
    Isaev, Alexei
    Vankevich, Roman
    Andrejev, Oleg
    Bendtsen, Jorgen
    Erichsen, Anders
    Funkquist, Lennart
    SMHI, Research Department, Oceanography.
    Inkala, Arto
    Neelov, Ivan
    Rasmus, Kai
    Medina, Miguel Rodriguez
    Raudsepp, Urmas
    Passenko, Jelena
    Soederkvist, Johan
    Sokolov, Alexander
    Kuosa, Harri
    Anderson, Thomas R.
    Lehmann, Andreas
    Skogen, Morten D.
    Validation of three-dimensional hydrodynamic models of the Gulf of Finland2010In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 15, no 5, p. 453-479Article in journal (Refereed)
    Abstract [en]

    A model-intercomparison study was conducted, the first of its kind for the Baltic Sea, whose aim was to systematically simulate the basic three-dimensional hydrographic properties of a realistic, complex basin. Simulations of the hydrographic features of the Gulf of Finland for the summer autumn of 1996 by six three-dimensional hydrodynamic models were compared. Validation was undertaken using more than 300 vertical hydrographic profiles of salinity and temperature. The analysis of model performance, including averaging of the ensemble results, was undertaken with a view to assessing the potential suitability of the models in reproducing the physics of the Baltic Sea accurately enough to serve as a basis for accurate simulations of biogeochemistry once ecosystem models are incorporated. The performance of the models was generally satisfactory. Nevertheless, all the models had some difficulties in correctly simulating vertical profiles of temperature and salinity, and hence mixed layer dynamics, particularly in the eastern Gulf of Finland. Results emphasized the need for high resolution in both vertical and horizontal directions in order to resolve the complex dynamics and bathymetry of the Baltic Sea. Future work needs to consider the choice of mixing and advection schemes, moving to higher resolution, high-frequency forcing, and the accurate representation of river discharges and boundary conditions.

  • 14.
    Samuelsson, Patrick
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Kourzeneva, Ekaterina
    Mironov, Dmitrii
    The impact of lakes on the European climate as simulated by a regional climate model2010In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 15, no 2, p. 113-129Article in journal (Refereed)
    Abstract [en]

    The impact of lakes on the European climate is considered by analysing two 30-year regional climate model (RCM) simulations. The RCM applied is the Rossby Centre regional climate model RCA3.5. A simulation where all lakes in the model domain are replaced by land surface is compared with a simulation where the effect of lakes is accounted for through the use of the lake model FLake coupled to RCA. The difference in 2m open-land air temperature between the two simulations shows that lakes induce a warming on the European climate for all seasons. The greatest impact is seen during autumn and winter over southern Finland and western Russia where the warming exceeds 1 C. Locally, e.g. over southern Finland and over Lake Ladoga, the convective precipitation is enhanced by 20%-40% during late summer and early autumn while it is reduced by more than 70% over Lake Ladoga during early summer.

  • 15. Soomere, Tarmo
    et al.
    Delpeche, Nicole
    Viikmaee, Bert
    Quak, Ewald
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Doeoes, Kristofer
    Patterns of current-induced transport in the surface layer of the Gulf of Finland2011In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 16, p. 49-63Article in journal (Refereed)
    Abstract [en]

    The Lagrangian trajectory model TRACMASS based on an Eulerian field of velocities (calculated using the Rossby Centre Ocean Model), combined with relevant statistical analysis, is used for the identification of transport patterns in the surface layer of the Gulf of Finland from 1987-1991. The analysis of velocity fields and properties of net and bulk transport (the distance between the start and end positions of a trajectory, and the total length of the trajectory, respectively) shows the presence of semi-persistent (with a typical lifetime from a week to a few months) features of the surface-layer dynamics, a part of which evidently cannot be extracted directly from the velocity fields. The modelled surface dynamics mostly hosts an Ekman-type drift and, in yearly average, contains an anticyclonic gyre occupying the western part of the gulf. The prevailing transport directions to the east and slightly to the south match the direction of the Ekman surface drift created by predominant south-western winds. The spatial patterns of the net transport substantially vary over different seasons. The most intense net transport along the coasts occurs in the western and central parts of the gulf but contains relatively intense largely meridional transport pathways in some seasons.

1 - 15 of 15
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