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  • 101.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Torstensson, G
    Wittgren, Hans Bertil
    SMHI, Research Department.
    Landscape planning to reduce coastal eutrophication: agricultural practices and constructed wetlands2004In: Landscape and Urban Planning, ISSN 0169-2046, E-ISSN 1872-6062, Vol. 67, no 1-4, p. 205-215Article in journal (Refereed)
    Abstract [en]

    Southern Sweden suffers from coastal eutrophication and one reason is the high nitrogen load through rivers. The major part of this load originates from diffuse land-based sources, e.g. arable soil leaching. Effective reduction of load from such sources demand careful landscape analysis, combined with changed behaviour of the stakeholders. This study describes a chain of methods to achieve trustworthy management plans that are based on numerical modelling and stakeholders participation and acceptance. The effect of some measures was unexpected when modelling their impact on the catchment scale. Management scenarios to reduce riverine nitrogen load were constructed in an actor game (i.e. role-play) for the Genevadsan catchment in southern Sweden. The game included stakeholders for implementation of a loading standard for maximum nitrogen transport at the river mouth. Scenarios were defined after negotiation among involved actors and included changes in agricultural practices, improved wastewater treatment, and establishment of wetlands. Numerical models were used to calculate the nitrogen reduction for different measures in each scenario. An index model (STANK) calculated the root zone leaching of nitrogen from crops at four type farms. This generated input to a catchment scale model (HBV-N) and farm economics. The economic impact of different sets of remedial measures was evaluated for each type farm and then extrapolated to the catchment. The results from scenario modelling show that possible changes in agricultural practices (such as tuning, timing of fertilisation and ploughing, changed crop cultivation) could reduce the nitrogen load to the sea by some 30%, while wetland construction only reduced the original load by some 5%. In the most cost-effective scenario agricultural practices could reduce the riverine load by 86 t per year at a cost of 1.0 million SEK, while constructed wetlands only reduced the load by 14 t per year at a cost of 1.7 million SEK. Thus, changed agricultural practices can be the most effective and less expensive way to reduce nitrogen transport from land to the sea, while constructed wetlands with realistic allocations and sizes may only have small impact on riverine nitrogen transport from land to sea. The overall experience is that actor games and numerical modelling are useful tools in landscape planning for analysing stakeholders' behaviour and the impact of measures to reduce coastal eutrophication. (C) 2003 Elsevier Science B.V. All rights reserved.

  • 102.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Wittgren, H B
    Modelling nitrogen removal in potential wetlands at the catchment scale2002In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, Vol. 19, no 1, p. 63-80Article in journal (Refereed)
    Abstract [en]

    The reduction of nitrogen fluxes from land to sea is an important task in areas with estuarine or marine eutrophication. Wetland creation has been proposed as one method to reduce nitrogen from streams draining agricultural areas. In this study, a scenario of nitrogen removal in created wetlands was evaluated by mathematical modelling of nitrogen fluxes in a catchment (224 km(2)) in southern Sweden. The scenario was based on topographically realistic siting of 40 potential wetlands with a total area of 0.92 km(2) (0.4% of the catchment area). Nitrogen removal in the wetlands was described with a simple and robust first-order model, which was modified and evaluated against data from eight monitored surface-flow wetlands. However, the modifications gave no substantial support for changing the basic model. For catchment-scale modelling this wetland model was incorporated into a dynamic process-based catchment model (HBV-N). The catchment was then divided to several coupled subbasins, so that the wetland influence on nitrogen load could be estimated separately for each potential wetland. The modelling showed that the 40 potential wetlands would reduce the nitrogen transport to the coast with approximately 6%. Specific removal rates ranged between 57 and 466 kg ha(-1) yr(-1) for the different wetlands, depending on residence time (size and hydraulic loading) and nitrogen concentration in inflow. Due to temperature dependence and seasonal variation in water discharge, significant decrease in nitrogen concentrations mainly occurred during summer periods with low loading. The study illustrates that catchment modelling is a useful method for analysing wetland creation plans, and that wetland creation must cover fairly large areas and be combined with other measures in order to achieve substantial reduction of nitrogen fluxes to coastal waters. Further monitoring of existing wetlands will improve the removal expression and decrease uncertainty. For instance, at present it could not be deducted whether wetlands with low average residence times ( < 2 days) have net removal or net resuspension on an annual basis. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 103.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Wittgren, Hans Bertil
    SMHI, Research Department.
    MODELING THE EFFECTS OF WETLANDS ON REGIONAL NITROGEN TRANSPORT1994In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 23, no 6, p. 378-386Article in journal (Refereed)
    Abstract [en]

    Created wetlands have been suggested as a method to reduce nitrogen transport to the Baltic Sea. This paper presents a dynamic conceptual model for simulation of the hypothetical effect of wetlands on nitrogen export to the coastal zone. The study was performed in the Soder-kopingsan drainage basin (882 km(2)) in southeastern Sweden, discharging into the Baltic Sea. An empirically based routine for wetland retention was calibrated separately and incorporated in the model. Scenarios with different location and size of wetlands were analyzed. It was estimated that conversion of 1% (8.8 km(2)) of this basin into wetlands would reduce the nitrogen transport by 10-16% and that more than 5% (45 km(2)) conversion to wetlands is required to reduce the transport by 50%. It was concluded that creation of wetlands should be considered, primarily, downstream from major lakes, in coastal areas, and where the summer load is a significant portion of the annual load. Some further conclusions from the study were that: i) the net reduction of nitrogen transport per unit area of wetland decreases with increasing total area of wetlands in a drainage basin; ii) the wetland retention efficiency obtained in studies of individual wetlands can not be extrapolated in a linear fashion to estimate the net reduction of nitrogen transport at the mouth of a whole drainage basin; iii) the seasonal hydrological and hydrochemical dynamics are of fundamental importance for wetland retention efficiency, which complicates comparison and extrapolation of results from one region to another.

  • 104. Arnbjerg-Nielsen, K.
    et al.
    Willems, P.
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Beecham, S.
    Pathirana, A.
    Gregersen, I. Bulow
    Madsen, H.
    Nguyen, V. -T-V
    Impacts of climate change on rainfall extremes and urban drainage systems: a review2013In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 68, no 1, p. 16-28Article, review/survey (Refereed)
    Abstract [en]

    A review is made of current methods for assessing future changes in urban rainfall extremes and their effects on urban drainage systems, due to anthropogenic-induced climate change. The review concludes that in spite of significant advances there are still many limitations in our understanding of how to describe precipitation patterns in a changing climate in order to design and operate urban drainage infrastructure. Climate change may well be the driver that ensures that changes in urban drainage paradigms are identified and suitable solutions implemented. Design and optimization of urban drainage infrastructure considering climate change impacts and co-optimizing these with other objectives will become ever more important to keep our cities habitable into the future.

  • 105.
    Arneborg, Lars
    et al.
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Lensu, Mikko
    Ljungman, Olof
    Mattsson, Johan
    Oil drift modeling in pack ice - Sensitivity to oil-in-ice parameters2017In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 144, p. 340-350Article in journal (Refereed)
  • 106.
    Arneborg, Lars
    et al.
    SMHI, Research Department, Oceanography.
    Jansson, Par
    Staalstrom, Andre
    Broström, Göran
    Tidal Energy Loss, Internal Tide Radiation, and Local Dissipation for Two-Layer Tidal Flow over a Sill2017In: Journal of Physical Oceanography, ISSN 0022-3670, E-ISSN 1520-0485, Vol. 47, no 7, p. 1521-1538Article in journal (Refereed)
  • 107. Arnold, S. R.
    et al.
    Emmons, L. K.
    Monks, S. A.
    Law, K. S.
    Ridley, D. A.
    Turquety, S.
    Tilmes, S.
    Thomas, J. L.
    Bouarar, I.
    Flemming, J.
    Huijnen, V.
    Mao, J.
    Duncan, B. N.
    Steenrod, S.
    Yoshida, Y.
    Langner, Joakim
    SMHI, Research Department, Air quality.
    Long, Y.
    Biomass burning influence on high-latitude tropospheric ozone and reactive nitrogen in summer 2008: a multi-model analysis based on POLMIP simulations2015In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, no 11, p. 6047-6068Article in journal (Refereed)
    Abstract [en]

    We have evaluated tropospheric ozone enhancement in air dominated by biomass burning emissions at high latitudes (>50 degrees N) in July 2008, using 10 global chemical transport model simulations from the POLMIP multimodel comparison exercise. In model air masses dominated by fire emissions, Delta O-3/Delta CO values ranged between 0.039 and 0.196 ppbv ppbv(-1) (mean: 0.113 ppbv ppbv(-1)) in freshly fire-influenced air, and between 0.140 and 0.261 ppbv ppb(-1) (mean: 0.193 ppbv) in more aged fire-influenced air. These values are in broad agreement with the range of observational estimates from the literature. Model Delta PAN/Delta CO enhancement ratios show distinct groupings according to the meteorological data used to drive the models. ECMWF-forced models produce larger Delta PAN/Delta CO values (4.47 to 7.00 pptv ppbv(-1)) than GEOS5-forced models (1.87 to 3.28 pptv ppbv(-1)), which we show is likely linked to differences in efficiency of vertical transport during poleward export from mid-latitude source regions. Simulations of a large plume of biomass burning and anthropogenic emissions exported from towards the Arctic using a Lagrangian chemical transport model show that 4-day net ozone change in the plume is sensitive to differences in plume chemical composition and plume vertical position among the POLMIP models. In particular, Arctic ozone evolution in the plume is highly sensitive to initial concentrations of PAN, as well as oxygenated VOCs (acetone, acetaldehyde), due to their role in producing the peroxyacetyl radical PAN precursor. Vertical displacement is also important due to its effects on the stability of PAN, and subsequent effect on NOx abundance. In plumes where net ozone production is limited, we find that the lifetime of ozone in the plume is sensitive to hydrogen peroxide loading, due to the production of HOx from peroxide photolysis, and the key role of HO2 + O-3 in controlling ozone loss. Overall, our results suggest that emissions from biomass burning lead to large-scale photochemical enhancement in high-latitude tropospheric ozone during summer.

  • 108.
    Arnér, Erik
    SMHI.
    Simulering av vårflöden med HBV-modellen1991Report (Other academic)
    Abstract [en]

    In order to improve the HBV-models ability to forecast the start of the spring flood, a degree-day model which uses the daily extreme temperatures to calculate snow accumulation and snowmelt was tested. The temperatures each day were assumed to vary linearly between the daily maximum and the daily minimum temperatu.re. Precipitation was distributed within each timestep as rain and snow according to the time the temperature had been on either side of a threshold temperature. Snow accumulation and snowmelt were calculated seperately du.ring timesteps where the extreme temperatures enclosed the threshold temperature. The simulation results were compared to those obtained by the original HBV-model, which uses the daily mean temperatu.res only. Six Swedish basins with different size and climate were selected, and totally 88 years were simulated and analyzed. The results showed that the new model improved the predictions of the start of the spring flood a bit, hut on the other hand it yielded lower values of the efficiency criterion, the R2-value. The results varied between the examined basins, hut altogether the performance of the new model was as good as the performance of the original HB Vmodel, and the models were considered equivalent. A test of the influence of the refreezing parameter in the new mode! was done in two small basins. The refreezing parameter was changed in steps from 0.00 to 0.21, and at each step the other snow parameters were recalibrated. It was found that the value of the refreezing parameter can have some influence, but the most important is that it exists so the snow is dry then the melting starts in spring. The amount of refreezing water can to some extent be controlled by other parameters in the model. In one of the basins the effect of the quality of used temperature data in the models was tested. This was done by running the models with data from one station at a time. Temperature data from three stations were used, and for every new station the snow parameters were recalibrated. It was noted that the simulation results were changed as much when the used temperature station was changed as when the model was changed. The results indicated that the new model was more dependant on accurate temperature data than the original HB V -model. The POC automatic calibration method (Har lin, 1991) has been used in this project, and almost 50 calibrations have been macie. The experience of this new method was good. The report includes a description of the HBV-model anda literature review on modeling snowmelt-runoff.

  • 109. Arritt, Raymond W.
    et al.
    Rummukainen, Markku
    SMHI, Core Services.
    CHALLENGES IN REGIONAL-SCALE CLIMATE MODELING2011In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 92, no 3, p. 365-368Article in journal (Other academic)
  • 110. Ashcroft, Linden
    et al.
    Coll, Joan Ramon
    Gilabert, Alba
    Domonkos, Peter
    Brunet, Manola
    Aguilar, Enric
    Castella, Merce
    Sigro, Javier
    Harris, Ian
    Undén, Per
    SMHI, Research Department, Meteorology.
    Jones, Phil
    A rescued dataset of sub-daily meteorological observations for Europe and the southern Mediterranean region, 1877-20122018In: Earth System Science Data, ISSN 1866-3508, E-ISSN 1866-3516, Vol. 10, no 3, p. 1613-1635Article in journal (Refereed)
  • 111. ASKNE, J
    et al.
    LEPPARANTA, M
    Thompson, Thomas
    SMHI.
    THE BOTHNIAN EXPERIMENT IN PREPARATION FOR ERS-1, 1988 (BEPERS-88) - AN OVERVIEW1992In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 13, no 13, p. 2377-2398Article in journal (Refereed)
    Abstract [en]

    BEPERS-88 was an extensive field campaign on the use of Synthetic Aperture Radar (SAR) in sea ice remote sensing in the Baltic Sea. This experiment was performed in order to study the possibilities of using the ERS-1 satellite SAR (and radar altimeter) in connection with the brackish ice in the Baltic Sea. The Canada Centre for Remote Sensing CV-580 C/X-band SAR was flown and an extensive validation programme was carried out. The data have been used for SAR image analysis, backscatter investigations, geophysical validation of SAR over sea ice, and evaluation of the potentials of SAR in operational ice information services. The results indicate that SAR can be used to discriminate between ice and open water, classify ice types into three categories, quantify ice ridging intensity, and determine the ice drift. As an operational tool SAR is expected to be an excellent complement to NOAA imagery and ground truth.

  • 112. Astrom, Christofer
    et al.
    Astrom, Daniel Oudin
    Andersson, Camilla
    SMHI, Research Department, Air quality.
    Ebi, Kristie L.
    Forsberg, Bertil
    Vulnerability Reduction Needed to Maintain Current Burdens of Heat-Related Mortality in a Changing Climate-Magnitude and Determinants2017In: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 14, no 7, article id 741Article in journal (Refereed)
  • 113. Astrom, Christofer
    et al.
    Ebi, Kristie L.
    Langner, Joakim
    SMHI, Research Department, Air quality.
    Forsberg, Bertil
    Developing a Heatwave Early Warning System for Sweden: Evaluating Sensitivity of Different Epidemiological Modelling Approaches to Forecast Temperatures2015In: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 12, no 1, p. 254-267Article in journal (Refereed)
    Abstract [en]

    Over the last two decades a number of heatwaves have brought the need for heatwave early warning systems (HEWS) to the attention of many European governments. The HEWS in Europe are operating under the assumption that there is a high correlation between observed and forecasted temperatures. We investigated the sensitivity of different temperature mortality relationships when using forecast temperatures. We modelled mortality in Stockholm using observed temperatures and made predictions using forecast temperatures from the European Centre for Medium-range Weather Forecasts to assess the sensitivity. We found that the forecast will alter the expected future risk differently for different temperature mortality relationships. The more complex models seemed more sensitive to inaccurate forecasts. Despite the difference between models, there was a high agreement between models when identifying risk-days. We find that considerations of the accuracy in temperature forecasts should be part of the design of a HEWS. Currently operating HEWS do evaluate their predictive performance; this information should also be part of the evaluation of the epidemiological models that are the foundation in the HEWS. The most accurate description of the relationship between high temperature and mortality might not be the most suitable or practical when incorporated into a HEWS.

  • 114. Astrom, Christofer
    et al.
    Orru, Hans
    Rocklov, Joacim
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    Ebi, Kristie L.
    Forsberg, Bertil
    Heat-related respiratory hospital admissions in Europe in a changing climate: a health impact assessment2013In: BMJ Open, ISSN 2044-6055, E-ISSN 2044-6055, Vol. 3, no 1, article id e001842Article in journal (Refereed)
    Abstract [en]

    Objectives: Respiratory diseases are ranked second in Europe in terms of mortality, prevalence and costs. Studies have shown that extreme heat has a large impact on mortality and morbidity, with a large relative increase for respiratory diseases. Expected increases in mean temperature and the number of extreme heat events over the coming decades due to climate change raise questions about the possible health impacts. We assess the number of heat-related respiratory hospital admissions in a future with a different climate. Design: A Europe-wide health impact assessment. Setting: An assessment for each of the EU27 countries. Methods: Heat-related hospital admissions under a changing climate are projected using multicity epidemiological exposure-response relationships applied to gridded population data and country-specific baseline respiratory hospital admission rates. Times-series of temperatures are simulated with a regional climate model based on four global climate models, under two greenhouse gas emission scenarios. Results: Between a reference period (1981-2010) and a future period (2021-2050), the total number of respiratory hospital admissions attributed to heat is projected to be larger in southern Europe, with three times more heat attributed respiratory hospital admissions in the future period. The smallest change was estimated in Eastern Europe with about a twofold increase. For all of Europe, the number of heat-related respiratory hospital admissions is projected to be 26 000 annually in the future period compared with 11 000 in the reference period. Conclusions: The results suggest that the projected effects of climate change on temperature and the number of extreme heat events could substantially influence respiratory morbidity across Europe.

  • 115.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    On the variability of Baltic Sea deepwater mixing1998In: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, Vol. 103, no C10, p. 21667-21682Article in journal (Refereed)
    Abstract [en]

    Historical oceanographic data from the period 1964-1997 from two deep subbasins (the Gotland Deep and the Landsort Deep) in the Baltic Sea have been analyzed, by using a budget method on stagnant periods, with respect to vertical diffusion and vertical energy flux density in the deep water. It was found that the rate of deepwater mixing varied with the seasons, with higher rates in fall and winter compared to spring and summer. Further, according to the analyzed data, the downward flux density of energy available for vertical diffusion decreased with increasing depth in the Gotland Deep. In the Landsort Deep, however, the flux density increased somewhat, probably because of topographic concentration of the energy, before decreasing toward the bottom. Moreover, the vertical energy flux densities were compared with the expected flux density from the local wind. It is proposed that in the Gotland Deep, which is outside the coastal boundary layer, the observed deepwater mixing is dominated by the energy input from the wind via inertial currents and internal waves. In the Landsort Deep, however, which is within the coastal boundary layer, the expected flux density of energy from the local wind cannot explain the observed rate of work against the buoyancy forces. It is proposed that the active coastal boundary layer plays a central role in the transfer of energy to mixing processes in the deep water.

  • 116.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Wind-driven internal waves and Langmuir circulations in a numerical ocean model of the southern Baltic Sea2002In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 107, no C11, article id 3204Article in journal (Refereed)
    Abstract [en]

    [1] A one-dimensional numerical ocean model of the southern Baltic Sea is used to investigate suitable parameterizations of unresolved turbulence and compare with available observations. The turbulence model is a k-epsilon model that includes extra source terms P-IW and P-LC of turbulent kinetic energy (TKE) due to unresolved, breaking internal waves and Langmuir circulations, respectively. As tides are negligible in the Baltic Sea, topographic generation of internal wave energy (IWE) is neglected. Instead, the energy for deepwater mixing in the Baltic Sea is provided by the wind. At each level the source term P-IW is assumed to be related to a vertically integrated pool of IWE, E-0, and the buoyancy frequency N at the same level, according to P-IW (z) proportional to E0Ndelta (z). This results in vertical profiles of epsilon (the dissipation rate of TKE) and K-h (the eddy diffusivity) according to epsilon proportional to N-delta and K-h proportional to Ndelta-2 below the main pycnocline. Earlier observations are inconclusive as to the proper value of delta, and here a range of values of delta is tested in hundreds of 10-year simulations of the southern Baltic Sea. It is concluded that delta = 1.0 +/- 0.3 and that a mean energy flux density to the internal wave field of about (0.9 +/- 0.3) x 10(-3) W m(-2) is needed to explain the observed salinity field. In addition, a simple wind-dependent formulation of the energy flux to the internal wave field is tested, which has some success in describing the short- and long-term variability of the deepwater turbulence. The model suggests that similar to16% of the energy supplied to the surface layer by the wind is used for deepwater mixing. Finally, it is also shown that Langmuir circulations are important to include when modeling the oceanic boundary layer. A simple parameterization of Langmuir circulations is tuned against large-eddy simulation data and verified for the Baltic Sea.

  • 117.
    Axell, Lars
    et al.
    SMHI, Research Department, Oceanography.
    Liu, Ye
    SMHI, Research Department, Oceanography.
    Application of 3-D ensemble variational data assimilation to a Baltic Sea reanalysis 1989-20132016In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 68, article id 24220Article in journal (Refereed)
    Abstract [en]

    A 3-D ensemble variational (3DEnVar) data assimilation method has been implemented and tested for oceanographic data assimilation of sea surface temperature (SST), sea surface salinity (SSS), sea ice concentration (SIC), and salinity and temperature profiles. To damp spurious long-range correlations in the ensemble statistics, horizontal and vertical localisation was implemented using empirical orthogonal functions. The results show that the 3DEnVar method is indeed possible to use in oceanographic data assimilation. So far, only a seasonally dependent ensemble has been used, based on historical model simulations. Near-surface experiments showed that the ensemble statistics gave inhomogeneous and anisotropic horizontal structure functions, and assimilation of real SST and SIC fields gave smooth, realistic increment fields. The implementation was multivariate, and results showed that the cross-correlations between variables work in an intuitive way, for example, decreasing SST where SIC was increased and vice versa. The profile data assimilation also gave good results. The results from a 25-year reanalysis showed that the vertical salinity and temperature structure were significantly improved, compared to both dependent and independent data.

  • 118.
    Axell, Lars
    et al.
    SMHI, Research Department, Oceanography.
    Ljungman, Olof
    SMHI, Research Department, Oceanography.
    A One-Equation Turbulence Model for Geophysical Applications: Comparison with Data and the k - epsilon Model2001In: Environmental Fluid Mechanics, ISSN 1567-7419, E-ISSN 1573-1510, Vol. 1, no 1, p. 71-106Article in journal (Refereed)
    Abstract [en]

    A one-equation turbulence model is presented, in which the turbulent kinetic energy k is calculated with a transport equation whereas the turbulent length scale l is calculated with an algebraic expression. The value of l depends on the local stratification and reduces to the classical kappa vertical bar z vertical bar scaling for unstratified flows near a wall, where vertical bar z vertical bar is the distance to the wall. The length scale decreases during stable stratification, and increases for unstable stratification compared to the neutral case. In the limit of strong stable stratification, the so-called buoyancy length scale proportional to k(1/2)N(-1) is obtained, where N is the buoyancy frequency. The length scale formulation introduces a single model parameter which is calibrated against experimental data. The model is verified extensively against laboratory measurements and oceanic data, and comparisons are made with the two-equation k-epsilon model. It is shown that the performance of the proposed k model is almost identical to that of the k-epsilon model. In addition, the stability functions of Launder are revisited and adjusted to obtain better agreement with recent data.

  • 119. Bailey, Helen
    et al.
    Fossette, Sabrina
    Bograd, Steven J.
    Shillinger, George L.
    Swithenbank, Alan M.
    Georges, Jean-Yves
    Gaspar, Philippe
    Strömberg, Patrik
    SMHI, Core Services.
    Paladino, Frank V.
    Spotila, James R.
    Block, Barbara A.
    Hays, Graeme C.
    Movement Patterns for a Critically Endangered Species, the Leatherback Turtle (Dermochelys coriacea), Linked to Foraging Success and Population Status2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 5, article id e36401Article in journal (Refereed)
    Abstract [en]

    Foraging success for pelagic vertebrates may be revealed by horizontal and vertical movement patterns. We show markedly different patterns for leatherback turtles in the North Atlantic versus Eastern Pacific, which feed on gelatinous zooplankton that are only occasionally found in high densities. In the Atlantic, travel speed was characterized by two modes, indicative of high foraging success at low speeds (<15 km d(-1)) and transit at high speeds (20-45 km d(-1)). Only a single mode was evident in the Pacific, which occurred at speeds of 21 km d(-1) indicative of transit. The mean dive depth was more variable in relation to latitude but closer to the mean annual depth of the thermocline and nutricline for North Atlantic than Eastern Pacific turtles. The most parsimonious explanation for these findings is that Eastern Pacific turtles rarely achieve high foraging success. This is the first support for foraging behaviour differences between populations of this critically endangered species and suggests that longer periods searching for prey may be hindering population recovery in the Pacific while aiding population maintenance in the Atlantic.

  • 120. Bais, A F
    et al.
    Gardiner, B G
    Slaper, H
    Blumthaler, M
    Bernhard, G
    McKenzie, R
    Webb, A R
    Seckmeyer, G
    Kjeldstad, B
    Koskela, T
    Kirsch, P J
    Grobner, J
    Kerr, J B
    Kazadzis, S
    Leszczynski, K
    Wardle, D
    Josefsson, Weine
    SMHI, Research Department, Atmospheric remote sensing.
    Brogniez, C
    Gillotay, D
    Reinen, H
    Weihs, P
    Svenoe, T
    Eriksen, P
    Kuik, F
    Redondas, A
    SUSPEN intercomparison of ultraviolet spectroradiometers2001In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 106, no D12, p. 12509-12525Article in journal (Refereed)
    Abstract [en]

    Results from an intercomparison campaign of ultraviolet spectroradiometers that was organized at Nea Michaniona, Greece July, 1-13 1997, are presented. Nineteen instrument systems from 15 different countries took part and provided spectra of global solar UV irradiance for two consecutive days from sunrise to sunset every half hour. No data exchange was allowed between participants in order to achieve absolutely independent results among the instruments. The data analysis procedure included the determination of wavelength shifts and the application of suitable corrections to the measured spectra, their standardization to common spectral resolution of 1 nm full width at half maximum and the application of cosine corrections. Reference spectra were calculated for each observational time, derived for a set of instruments which were objectively selected and used as comparison norms for the assessment of the relative agreement among the various instruments. With regard to the absolute irradiance measurements, the range of the deviations from the reference for all spectra was within +/- 20%. About half of the instruments agreed to within +/-5%, while only three fell outside the +/- 10% agreement limit. As for the accuracy of the wavelength registration of the recorded spectra, for most of the spectroradiometers (14) the calculated wavelength shifts were smaller than 0.2 nm. The overall outcome of the campaign was very encouraging, as it was proven that the agreement among the majority of the instruments was good and comparable to the commonly accepted uncertainties of spectral UV measurements. In addition, many of the instruments provided consistent results relative to at least the previous two intercomparison campaigns, held in 1995 in Ispra, Italy and in 1993 in Garmisch-Partenkirchen, Germany. As a result of this series of intercomparison campaigns, several of the currently operating spectroradiometers operating may be regarded as a core group Of instruments, which with the employment of proper operational procedures are capable of providing quality spectral solar UV measurements.

  • 121. Bal, S.
    et al.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Spangehl, T.
    Cubasch, U.
    On the robustness of the solar cycle signal in the Pacific region2011In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, article id L14809Article in journal (Refereed)
    Abstract [en]

    The potential role of the stratosphere for the 11-year solar cycle signal in the Pacific region is investigated by idealized simulations using a coupled atmosphere-ocean general circulation model. The model includes a detailed representation of the stratosphere and accounts for changes in stratospheric heating rates from prescribed time dependent variations of ozone and spectrally high resolved solar irradiance. Three transient simulations are performed spanning 21 solar cycles each. The simulations use slightly different ozone perturbations representing uncertainties of solar induced ozone variations. The model reproduces the main features of the 20th century observed solar response. A persistent mean sea level pressure response to solar forcing is found for the eastern North Pacific extending over North America. Moreover, there is evidence for a La Nina-like response assigned to solar maximum conditions with below normal SSTs in the equatorial eastern Pacific, reduced equatorial precipitation, enhanced off-equatorial precipitation and an El Nino-like response a couple of years later, thus confirming the response to solar forcing at the surface seen in earlier studies. The amplitude of the solar signal in the Pacific region depends to a great extent on the choice of the centennial period averaged. Citation: Bal, S., S. Schimanke, T. Spangehl, and U. Cubasch (2011), On the robustness of the solar cycle signal in the Pacific region, Geophys. Res. Lett., 38, L14809, doi:10.1029/2011GL047964.

  • 122. Bal, Sourabh
    et al.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Spangehl, Thomas
    Cubasch, Ulrich
    Enhanced residual mean circulation during the evolution of split type sudden stratospheric warming in observations and model simulations2018In: Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences, ISSN 0253-4126, E-ISSN 0973-774X, Vol. 127, no 5, article id 68Article in journal (Refereed)
  • 123. Bal, Sourabh
    et al.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Spangehl, Thomas
    Cubasch, Ulrich
    Variable influence on the equatorial troposphere associated with SSW using ERA-Interim2017In: Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences, ISSN 0253-4126, E-ISSN 0973-774X, Vol. 126, no 2, article id UNSP 19Article in journal (Refereed)
  • 124. Balaji, Venkatramani
    et al.
    Maisonnave, Eric
    Zadeh, Niki
    Lawrence, Bryan N.
    Biercamp, Joachim
    Fladrich, Uwe
    SMHI, Research Department, Climate research - Rossby Centre.
    Aloisio, Giovanni
    Benson, Rusty
    Caubel, Arnaud
    Durachta, Jeffrey
    Foujols, Marie-Alice
    Lister, Grenville
    Mocavero, Silvia
    Underwood, Seth
    Wright, Garrett
    CPMIP: measurements of real computational performance of Earth system models in CMIP62017In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 10, no 1, p. 19-34Article in journal (Refereed)
  • 125. Baldacchini, Chiara
    et al.
    Castanheiro, Ana
    Maghakyan, Nairuhi
    Sgrigna, Gregorio
    Verhelst, Jolien
    Alonso, Rocio
    Amorim, Jorge Humberto
    SMHI, Research Department, Air quality.
    Bellan, Patrick
    Bojovic, Danijela Dunisijevic
    Breuste, Juergen
    Buhler, Oliver
    Cantar, Ilie C.
    Carinanos, Paloma
    Carriero, Giulia
    Churkina, Galina
    Dinca, Lucian
    Esposito, Raffaela
    Gawronski, Stanislaw W.
    Kern, Maren
    Le Thiec, Didier
    Moretti, Marco
    Ningal, Tine
    Rantzoudi, Eleni C.
    Sinjur, Iztok
    Stojanova, Biljana
    Urosevic, Mira Anicic
    Velikova, Violeta
    Zivojinovic, Ivana
    Sahakyan, Lilit
    Calfapietra, Carlo
    Samson, Roeland
    How Does the Amount and Composition of PM Deposited on Platanus acerifolia Leaves Change Across Different Cities in Europe?2017In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, no 3, p. 1147-1156Article in journal (Refereed)
  • 126. Baranizadeh, Elham
    et al.
    Murphy, Benjamin N.
    Julin, Jan
    Falahat, Saeed
    SMHI, Core Services.
    Reddington, Carly L.
    Arola, Antti
    Ahlm, Lars
    Mikkonen, Santtu
    Fountoukis, Christos
    Patoulias, David
    Minikin, Andreas
    Hamburger, Thomas
    Laaksonen, Ari
    Pandis, Spyros N.
    Vehkamaki, Hanna
    Lehtinen, Kari E. J.
    Riipinen, Ilona
    Implementation of state-of-the-art ternary new-particle formation scheme to the regional chemical transport model PMCAMx-UF in Europe2016In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 9, no 8, p. 2741-2754Article in journal (Refereed)
  • 127. Baron, P.
    et al.
    Murtagh, D. P.
    Urban, J.
    Sagawa, H.
    Ochiai, S.
    Kasai, Y.
    Kikuchi, K.
    Khosrawi, F.
    Körnich, Heiner
    SMHI, Research Department, Meteorology.
    Mizobuchi, S.
    Sagi, K.
    Yasui, M.
    Observation of horizontal winds in the middle-atmosphere between 30 degrees S and 55 degrees N during the northern winter 2009-20102013In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 12, p. 6049-6064Article in journal (Refereed)
    Abstract [en]

    Although the links between stratospheric dynamics, climate and weather have been demonstrated, direct observations of stratospheric winds are lacking, in particular at altitudes above 30 km. We report observations of winds between 8 and 0.01 hPa (similar to 35-80 km) from October 2009 to April 2010 by the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station. The altitude range covers the region between 35-60 km where previous space-borne wind instruments show a lack of sensitivity. Both zonal and meridional wind components were obtained, though not simultaneously, in the latitude range from 30 degrees S to 55 degrees N and with a single profile precision of 7-9 ms(-1) between 8 and 0.6 hPa and better than 20 ms(-1) at altitudes above. The vertical resolution is 5-7 km except in the upper part of the retrieval range (10 km at 0.01 hPa). In the region between 1-0.05 hPa, an absolute value of the mean difference <2 ms(-1) is found between SMILES profiles retrieved from different spectroscopic lines and instrumental settings. Good agreement (absolute value of the mean difference of similar to 2 ms(-1)) is also found with the European Centre for Medium-Range Weather Forecasts (ECMWF) analysis in most of the stratosphere except for the zonal winds over the equator (difference >5 ms(-1)). In the mesosphere, SMILES and ECMWF zonal winds exhibit large differences (>20 ms(-1)), especially in the tropics. We illustrate our results by showing daily and monthly zonal wind variations, namely the semi-annual oscillation in the tropics and reversals of the flow direction between 50-55 degrees N during sudden stratospheric warmings. The daily comparison with ECMWF winds reveals that in the beginning of February, a significantly stronger zonal westward flow is measured in the tropics at 2 hPa compared to the flow computed in the analysis (difference of similar to 20 ms(-1)). The results show that the comparison between SMILES and ECMWF winds is not only relevant for the quality assessment of the new SMILES winds, but it also provides insights on the quality of the ECMWF winds themselves. Although the instrument was not specifically designed for measuring winds, the results demonstrate that space-borne sub-mm wave radiometers have the potential to provide good quality data for improving the stratospheric winds in atmospheric models.

  • 128. Barreiro, Marcelo
    et al.
    Sitz, Lina
    de Mello, Santiago
    Fuentes Franco, Ramon
    SMHI, Research Department, Climate research - Rossby Centre.
    Renom, Madeleine
    Farneti, Riccardo
    Modelling the role of Atlantic air-sea interaction in the impact of Madden-Julian Oscillation on South American climate2019In: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 39, no 2, p. 1104-1116Article in journal (Refereed)
  • 129. Barthelmie, R
    et al.
    Larsen, G
    Pryor, S
    Jorgensen, H
    Bergstrom, H
    Schlez, W
    Rados, K
    Lange, B
    Volund, P
    Neckelmann, S
    Mogensen, S
    Schepers, G
    Hegberg, T
    Folkerts, L
    Magnusson, Mikael
    SMHI, Core Services.
    ENDOW (Efficient development of offshore wind farms): Modelling wake and boundary layer interactions2004In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 7, no 3, p. 225-245Article in journal (Refereed)
    Abstract [en]

    While experience gained through the offshore wind energy projects currently operating is valuable, a major uncertainty in estimating power production lies in the prediction of the dynamic links between the atmosphere and wind turbines in offshore regimes. The objective of the ENDOW project was to evaluate, enhance and interface wake and boundary layer models for utilization offshore. The project resulted in a significant advance in the state of the art in both wake and marine boundary layer models, leading to improved prediction of wind speed and turbulence profiles within large offshore wind farms. Use of new databases from existing offshore wind farms and detailed wake profiles collected using sodar provided a unique opportunity to undertake the first comprehensive evaluation of wake models in the offshore environment. The results of wake model performance in different wind speed, stability and roughness conditions relative to observations provided criteria for their improvement. Mesoscale model simulations were used to evaluate the impact of thermal flows, roughness and topography on offshore wind speeds. The model hierarchy developed under ENDOW forms the basis of design tools for use by wind energy developers and turbine manufacturers to optimize power output from offshore wind farms through minimized wake effects and optimal grid connections. The design tools are being built onto existing regional-scale models and wind farm design software which was developed with EU funding and is in use currently by wind energy developers. Copyright (C) 2004 John Wiley Sons, Ltd.

  • 130. Bartolino, Valerio
    et al.
    Tian, Huidong
    Bergstrom, Ulf
    Jounela, Pekka
    Aro, Eero
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Cardinale, Massimiliano
    Bland, Barbara
    Casini, Michele
    Spatio-temporal dynamics of a fish predator: Density-dependent and hydrographic effects on Baltic Sea cod population2017In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 2, article id e0172004Article in journal (Refereed)
  • 131. Bauer, Barbara
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Casini, Michele
    Hoff, Ayoe
    Margonski, Piotr
    Orio, Alessandro
    Saraiva, Sofia
    SMHI, Research Department, Oceanography.
    Steenbeek, Jeroen
    Tomczak, Maciej T.
    Reducing eutrophication increases spatial extent of communities supporting commercial fisheries: a model case study2018In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 75, no 4, p. 1306-1317Article in journal (Refereed)
  • 132. Bauer, Barbara
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Casini, Michele
    Hoff, Ayoe
    Margonski, Piotr
    Orio, Alessandro
    Saraiva, Sofia
    SMHI, Research Department, Oceanography.
    Steenbeek, Jeroen
    Tomczak, Maciej T.
    Reducing eutrophication increases spatial extent of communities supporting commercial fisheries: a model case study (vol 75, pg 1155, 2018)2018In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 75, no 3, p. 1155-1155Article in journal (Refereed)
  • 133. Bech, J.
    et al.
    Gjertsen, U.
    Haase, Gunther
    SMHI, Research Department, Atmospheric remote sensing.
    Modelling weather radar beam propagation and topographical blockage at northern high latitudes2007In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 133, no 626, p. 1191-1204Article in journal (Refereed)
    Abstract [en]

    This paper describes a study to evaluate the variability of radio-propagation conditions and to assess their effects upon weather-radar beam blockage corrections for precipitation estimates. Radiosonde observations are examined in order to analyse the propagation conditions at several locations covered by the Nordic Weather Radar Network (NORDRAD). A beam-propagation model is used to simulate the interaction between the radar beam and the topography and to derive correction factors. The model is applied to correct yearly accumulations, assuming standard radio-propagation conditions, and is also used to examine case studies in detail under various propagation conditions. The correction reduces the bias between yearly radar precipitation estimates and gauge records by 1 dB for moderate blockages (1% to 50%), and by up to 3 dB for severe blockages (50% to 70%). The case studies indicate that HIRLAM forecasts show potential to predict the radar coverage and the associated ground- and sea-clutter patterns. This research aims at determining a beam-blockage-correction algorithm to be used within the NORDRAD quality-control system. This is particularly useful for obtaining radar precipitation estimates in environments with complex topography. Copyright (C) 2007 Royal Meteorological Society.

  • 134. Belda, Michal
    et al.
    Skalak, Petr
    Farda, Ales
    Halenka, Tomas
    Deque, Michel
    Csima, Gabriella
    Bartholy, Judit
    Torma, Csaba
    Boroneant, Constanta
    Caian, Mihaela
    SMHI, Research Department, Climate research - Rossby Centre.
    Spiridonov, Valery
    CECILIA Regional Climate Simulations for Future Climate: Analysis of Climate Change Signal2015In: Advances in Meteorology, ISSN 1687-9309, E-ISSN 1687-9317, article id 354727Article in journal (Refereed)
    Abstract [en]

    Regional climate models (RCMs) are important tools used for downscaling climate simulations from global scale models. In project CECILIA, two RCMs were used to provide climate change information for regions of Central and Eastern Europe. Models RegCM and ALADIN-Climate were employed in downscaling global simulations from ECHAM5 and ARPEGE-CLIMAT under IPCC A1B emission scenario in periods 2021-2050 and 2071-2100. Climate change signal present in these simulations is consistent with respective driving data, showing similar large-scale features: warming between 0 and 3 degrees C in the first period and 2 and 5 degrees C in the second period with the least warming in northwestern part of the domain increasing in the southeastern direction and small precipitation changes within range of +1 to -1 mm/day. Regional features are amplified by the RCMs, more so in case of the ALADIN family of models.

  • 135. Beldring, S.
    et al.
    Andréasson, J.
    Bergström, Sten
    SMHI, Research Department, Hydrology.
    Graham, Phil
    SMHI, Professional Services.
    Jónsdóttir, J. F
    Rogozova, S.
    Rosberg, Jörgen
    SMHI, Research Department, Hydrology.
    Suomalainen, M.
    Tonning, T.
    Vehviläinen, B.
    Veijalainen, N.
    Mapping water resources in the Nordic region under a changing climate.2006Report (Other academic)
  • 136. Bellucci, A.
    et al.
    Haarsma, R.
    Bellouin, N.
    Booth, B.
    Cagnazzo, C.
    van den Hurk, B.
    Keenlyside, N.
    Koenigk, Torben
    SMHI, Research Department, Climate research - Rossby Centre.
    Massonnet, F.
    Materia, S.
    Weiss, M.
    Advancements in decadal climate predictability: The role of nonoceanic drivers2015In: Reviews of geophysics, ISSN 8755-1209, E-ISSN 1944-9208, Vol. 53, no 2, p. 165-202Article in journal (Refereed)
    Abstract [en]

    We review recent progress in understanding the role of sea ice, land surface, stratosphere, and aerosols in decadal-scale predictability and discuss the perspectives for improving the predictive capabilities of current Earth system models (ESMs). These constituents have received relatively little attention because their contribution to the slow climatic manifold is controversial in comparison to that of the large heat capacity of the oceans. Furthermore, their initialization as well as their representation in state-of-the-art climate models remains a challenge. Numerous extraoceanic processes that could be active over the decadal range are proposed. Potential predictability associated with the aforementioned, poorly represented, and scarcely observed constituents of the climate system has been primarily inspected through numerical simulations performed under idealized experimental settings. The impact, however, on practical decadal predictions, conducted with realistically initialized full-fledged climate models, is still largely unexploited. Enhancing initial-value predictability through an improved model initialization appears to be a viable option for land surface, sea ice, and, marginally, the stratosphere. Similarly, capturing future aerosol emission storylines might lead to an improved representation of both global and regional short-term climatic changes. In addition to these factors, a key role on the overall predictive ability of ESMs is expected to be played by an accurate representation of processes associated with specific components of the climate system. These act as signal carriers, transferring across the climatic phase space the information associated with the initial state and boundary forcings, and dynamically bridging different (otherwise unconnected) subsystems. Through this mechanism, Earth system components trigger low-frequency variability modes, thus extending the predictability beyond the seasonal scale.

  • 137. Bellucci, A.
    et al.
    Haarsma, R.
    Gualdi, S.
    Athanasiadis, P. J.
    Caian, Mihaela
    SMHI, Research Department, Climate research - Rossby Centre.
    Cassou, C.
    Fernandez, E.
    Germe, A.
    Jungclaus, J.
    Kroeger, J.
    Matei, D.
    Mueller, W.
    Pohlmann, H.
    Salas y Melia, D.
    Sanchez, E.
    Smith, D.
    Terray, L.
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Yang, S.
    An assessment of a multi-model ensemble of decadal climate predictions2015In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 44, no 9-10, p. 2787-2806Article in journal (Refereed)
    Abstract [en]

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

  • 138.
    Belusic, Danijel
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Fuentes-Franco, Ramon
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    Jukimenko, Alex
    Afforestation reduces cyclone intensity and precipitation extremes over Europe2019In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 14, no 7, article id UNSP 074009Article in journal (Refereed)
  • 139. Bengtsson, L.
    et al.
    Grahn, L
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Hydrological function of a thin extensive green roof in southern Sweden2005In: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 36, no 3, p. 259-268Article in journal (Refereed)
    Abstract [en]

    The runoff from and the water balance of a thin extensive green roof with sedum-moss have been studied. The soil cover is about 3 cm underlain by a thin drainage layer. The water balance is determined on a monthly basis. The runoff from the green roof is much reduced compared to runoff from hard roofs because of evapotranspiration. The annual runoff is rather close to that of natural river basins. Although most rainy days there is no or little runoff from the roof, the highest observed daily runoff values are close to the daily rainfall. Runoff is initiated when the soil is at field capacity, which for the studied roof corresponds to 9 mm storage. After that, on a not very short time basis, the runoff equals the precipitation. The reduction of the daily runoff can be described in a simple way knowing the daily precipitation, potential evaporation and storage capacity of the green roof.

  • 140.
    Bengtsson,, Lennart
    et al.
    SMHI.
    Gustafsson, Nils
    SMHI, Research Department, Meteorology.
    Döös, Bo
    SMHI.
    Söderman, Daniel
    Helsinki University in Finland.
    Moen, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Thompson, Thomas
    SMHI.
    Jakobsson, Paul
    SMHI.
    Bleckert, Gunnar
    SMHI.
    Henriksson, Ann-Beate
    SMHI.
    Lindgren, Bo
    SMHI.
    Kållberg, Per
    SMHI, Research Department, Meteorology.
    The Meteorological Auto Code (MAC) and Numerical Weather Prediction (NWP) at SMHI2016Report (Other academic)
    Abstract [en]

    Sweden was a pioneering country in the development of NumericalWeather Prediction (NWP). The worlds first operational numerical forecast was produced already in 1954 by the International Meteorological Institute in Stockholm. SMHI started a bit later, but in 1961 a long term program for development of NWP was initiated. The activities grew gradually during the 1960’s and resulted in a core component for the SMHI forecast services. An early challenge was to overcome the limited computational resources with slow computational speed, small memory size and primitive software support. It was necessary to compensate for these limitations with dedicated work and creativity. A core component in this work was the software system MAC (Meteorological Auto Code) that was developed by the NWP group at SMHI. The MAC system is described in detail in this report and it included all computational software needed for the weather service, for example numerical models, objective analysis techniques, automatic data extraction, quality control of observations as well as forecast products in graphical or digital form.

    We hope that this report will provide the younger generation with some insight into the conditions for development of NWP during the 1960’s.

  • 141.
    Bengtsson, Lisa
    et al.
    SMHI, Research Department, Meteorology.
    Andrae, Ulf
    SMHI, Research Department, Meteorology.
    Aspelien, Trygve
    SMHI.
    Batrak, Yurii
    Calvo, Javier
    de Rooy, Wim
    Gleeson, Emily
    Hansen-Sass, Bent
    Homleid, Mariken
    Hortal, Mariano
    Ivarsson, Karl-Ivar
    SMHI, Core Services.
    Lenderink, Geert
    Niemelza, Sami
    Nielsen, Kristian Pagh
    Onvlee, Jeanette
    Rontu, Laura
    SMHI.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Santos Munoz, Daniel
    Subias, Alvaro
    Tijm, Sander
    Toll, Velle
    Yang, Xiaohua
    Koltzow, Morten Odegaard
    The HARMONIE-AROME Model Configuration in the ALADIN-HIRLAM NWP System2017In: Monthly Weather Review, ISSN 0027-0644, E-ISSN 1520-0493, Vol. 145, no 5, p. 1919-1935Article in journal (Refereed)
  • 142.
    Bengtsson, Lisa
    et al.
    SMHI, Research Department, Meteorology.
    Körnich, Heiner
    SMHI, Research Department, Meteorology.
    Impact of a stochastic parametrization of cumulus convection, using cellular automata, in a mesoscale ensemble prediction system2016In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 142, no 695, p. 1150-1159Article in journal (Refereed)
    Abstract [en]

    A stochastic parametrization for deep convection, based on cellular automata, has been evaluated in the high-resolution (2.5 km) ensemble prediction system Hirlam Aladin Regional Mesoscale Operational NWP Ensemble Prediction System (HarmonEPS). We studied whether such a stochastic physical parametrization, whilst implemented in a deterministic forecast model, can have an impact on the performance of the uncertainty estimates given by an ensemble prediction system. Various feedback mechanisms in the parametrization were studied with respect to ensemble spread and skill, in both subgrid and resolved precipitation fields. It was found that the stochastic parametrization improves the model skill in general, by reducing a positive bias in precipitation. This reduction in bias, however, led to a reduction in ensemble spread of precipitation. Overall, scores that measure the accuracy and reliability of probabilistic predictions indicate that the net impact (improved skill, degraded spread) of the ensemble prediction system is improved for 6 h accumulated precipitation with the stochastic parametrization and is rather neutral for other quantities examined.

  • 143.
    Bengtsson, Lisa
    et al.
    SMHI, Research Department, Meteorology.
    Körnich, Heiner
    SMHI, Research Department, Meteorology.
    Kaellen, Erland
    Svensson, Gunilla
    Large-Scale Dynamical Response to Subgrid-Scale Organization Provided by Cellular Automata2011In: Journal of Atmospheric Sciences, ISSN 0022-4928, E-ISSN 1520-0469, Vol. 68, no 12, p. 3132-3144Article in journal (Refereed)
    Abstract [en]

    Because of the limited resolution of numerical weather prediction (NWP) models, subgrid-scale physical processes are parameterized and represented by gridbox means. However, some physical processes are better represented by a mean and its variance; a typical example is deep convection, with scales varying from individual updrafts to organized mesoscale systems. This study investigates, in an idealized setting, whether a cellular automaton (CA) can be used to enhance subgrid-scale organization by forming clusters representative of the convective scales and thus yield a stochastic representation of subgrid-scale variability. The authors study the transfer of energy from the convective to the larger atmospheric scales through nonlinear wave interactions. This is done using a shallow water (SW) model initialized with equatorial wave modes. By letting a CA act on a finer resolution than that of the SW model, it can be expected to mimic the effect of, for instance, gravity wave propagation on convective organization. Employing the CA scheme permits the reproduction of the observed behavior of slowing down equatorial Kelvin modes in convectively active regions, while random perturbations fail to feed back on the large-scale flow. The analysis of kinetic energy spectra demonstrates that the CA subgrid scheme introduces energy backscatter from the smallest model scales to medium scales. However, the amount of energy backscattered depends almost solely on the memory time scale introduced to the subgrid scheme, whereas any variation in spatial scales generated does not influence the energy spectra markedly.

  • 144.
    Bengtsson, Lisa
    et al.
    SMHI, Research Department, Meteorology.
    Magnusson, Linus
    Källén, Erland
    Independent Estimations of the Asymptotic Variability in an Ensemble Forecast System2008In: Monthly Weather Review, ISSN 0027-0644, E-ISSN 1520-0493, Vol. 136, no 11, p. 4105-4112Article in journal (Refereed)
    Abstract [en]

    One desirable property within an ensemble forecast system is to have a one-to-one ratio between the root-mean-square error (rmse) of the ensemble mean and the standard deviation of the ensemble (spread). The ensemble spread and forecast error within the ECMWF ensemble prediction system has been extrapolated beyond 10 forecast days using a simple model for error growth. The behavior of the ensemble spread and the rmse at the time of the deterministic predictability are compared with derived relations of rmse at the infinite forecast length and the characteristic variability of the atmosphere in the limit of deterministic predictability. Utilizing this methodology suggests that the forecast model and the atmosphere do not have the same variability, which raises the question of how to obtain a perfect ensemble.

  • 145.
    Bengtsson, Lisa
    et al.
    SMHI, Research Department, Meteorology.
    Steinheimer, Martin
    Bechtold, Peter
    Geleyn, Jean-Francois
    A stochastic parametrization for deep convection using cellular automata2013In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 139, no 675, p. 1533-1543Article in journal (Refereed)
    Abstract [en]

    A cellular automaton (CA) is introduced to the deep convection parametrization of the high-resolution limited-area model Aire Limitee Adaptation/Application de la Recherche a l'Operationnel (ALARO). The self-organizational characteristics of the CA allow for lateral communication between adjacent numerical weather prediction (NWP) model grid boxes and add additional memory to the deep convection scheme. The CA acts in two horizontal dimensions, with finer grid spacing than the NWP model. It is randomly seeded in regions where convective available potential energy (CAPE) exceeds a threshold value. Both deterministic and probabilistic rules, coupled to the large-scale wind, are explored to evolve the CA in time. Case studies indicate that the scheme has the potential to organize cells along convective squall lines and enhance advective effects. An ensemble of forecasts using the present CA scheme demonstrated an ensemble spread in the resolved wind field in regions where deep convection is large. Such a spread represents the uncertainty due to subgrid variability of deep convection and could be an interesting addition to an ensemble prediction system.

  • 146.
    Bengtsson, Lisa
    et al.
    SMHI, Research Department, Meteorology.
    Tijm, Sander
    Vana, Filip
    Svensson, Gunilla
    Impact of Flow-Dependent Horizontal Diffusion on Resolved Convection in AROME2012In: Journal of Applied Meteorology and Climatology, ISSN 1558-8424, E-ISSN 1558-8432, Vol. 51, no 1, p. 54-67Article in journal (Refereed)
    Abstract [en]

    Horizontal diffusion in numerical weather prediction models is, in general, applied to reduce numerical noise at the smallest atmospheric scales. In convection-permitting models, with horizontal grid spacing on the order of 1-3 km, horizontal diffusion can improve the model skill of physical parameters such as convective precipitation. For instance, studies using the convection-permitting Applications of Research to Operations at Mesoscale model (AROME) have shown an improvement in forecasts of large precipitation amounts when horizontal diffusion is applied to falling hydrometeors. The nonphysical nature of such a procedure is undesirable, however. Within the current AROME, horizontal diffusion is imposed using linear spectral horizontal diffusion on dynamical model fields. This spectral diffusion is complemented by nonlinear, flow-dependent, horizontal diffusion applied on turbulent kinetic energy, cloud water, cloud ice, rain, snow, and graupel. In this study, nonlinear flow-dependent diffusion is applied to the dynamical model fields rather than diffusing the already predicted falling hydrometeors. In particular, the characteristics of deep convection are investigated. Results indicate that, for the same amount of diffusive damping, the maximum convective updrafts remain strong for both the current and proposed methods of horizontal diffusion. Diffusing the falling hydrometeors is necessary to see a reduction in rain intensity, but a more physically justified solution can be obtained by increasing the amount of damping on the smallest atmospheric scales using the nonlinear, flow-dependent, diffusion scheme. In doing so, a reduction in vertical velocity was found, resulting in a reduction in maximum rain intensity.

  • 147. Bennartz, R
    et al.
    Michelson, Daniel
    SMHI, Core Services.
    Correlation of precipitation estimates from spaceborne passive microwave sensors and weather radar imagery for BALTEX PIDCAP2003In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 24, no 4, p. 723-739Article in journal (Refereed)
    Abstract [en]

    This paper describes the evaluation of a-combined radar and passive microwave dataset obtained during the PIDCAP study of the Baltic Sea Experiment (BALTEX), where three-dimensional volumes of data from the Gotland radar were obtained timed according to the overpasses of the DMSP-satellites F10 and F13. Both satellites are 'equipped with a Special Sensor Microwave/Imager (SSM/I), suitable for precipitation retrievals. We compare radar precipitation estimates, convolved to the native resolution of the SSM/I, at different altitudes with polarization and scattering indices (S-85) derived from the SSM/I. For all 22 overpasses investigated here radar precipitation estimates at 3-4 km altitude correlate well with the SSM/I-derived S-85 (average correlation coefficient = 0.70). Although more directly linked to surface precipitation, polarization indices have been found to be less correlated with radar data, due to limitations inherent in the remote sensing of precipitation at higher latitudes. A stratification of the dataset into frontal and convective events revealed significant variations in these relationships for different types of precipitation events, thus reflecting different cloud microphysical processes associated with precipitation initialization. The relationship between S85 and radar rain estimates at higher altitudes varies considerably for different convective and frontal events. The sensitivity of S-85 to radar-derived rain rate ranges from 3.1 K mm(-1) h(-1) for a strong convective event to about 25 K mm(-1) h(-1) for the frontal and about 70 mm(-1) h(-1) for the small-scale convective events. For extrapolated surface precipitation estimates, sensitivities decrease to 14 mm(-1) h(-1) and 25 mm(-1) h(-1) for frontal and small-scale convective precipitation, respectively.

  • 148. Bennartz, R
    et al.
    Thoss, Anke
    SMHI, Research Department, Atmospheric remote sensing.
    Dybbroe, Adam
    SMHI, Core Services.
    Michelson, Daniel
    SMHI, Core Services.
    Precipitation analysis using the Advanced Microwave Sounding Unit in support of nowcasting applications2002In: Meteorological Applications, ISSN 1350-4827, E-ISSN 1469-8080, Vol. 9, no 2, p. 177-189Article in journal (Refereed)
    Abstract [en]

    We describe a method to remotely sense precipitation and classify its intensity over water, coasts and land surfaces. This method is intended to be used in an operational nowcasting environment. It is based on data obtained from the Advanced Microwave Sounding Unit (AMSU) onboard NOAA-15. Each observation is assigned a probability of belonging to four classes: precipitation-free, risk of precipitation, precipitation between 0.5 and 5 mm/h, and precipitation higher than 5 mm/h. Since the method is designed to work over different surface types, it relies mainly on the scattering signal of precipitation-sized ice particles received at high frequencies. For the calibration and validation of the method we use an eight-month dataset of combined weather radar and AMSU data obtained over the Baltic area. We compare results for the AMSU-B channels at 89 GHz and 150 GHz and find that the high frequency channel at 150 GHz allows for a much better discrimination of different types of precipitation than the 89 GHz channel. While precipitation-free areas, as well as heavily precipitating areas (> 5 mm/h), can be identified to high accuracy, the intermediate classes are more ambiguous. This stems from the ambiguity of the passive microwave observations as well as from the non-perfect matching of the different data sources and sub-optimal radar adjustment. In addition to a statistical assessment of the method's accuracy, we present case studies to demonstrate its capabilities to classify different types of precipitation and to work over highly structured, inhomogeneous surfaces.

  • 149. Bennartz, Ralf
    et al.
    Hoschen, Heidrun
    Picard, Bruno
    Schroder, Marc
    Stengel, Martin
    Sus, Oliver
    Bojkov, Bojan
    Casadio, Stefano
    Diedrich, Hannes
    Eliasson, Salomon
    SMHI, Research Department, Atmospheric remote sensing.
    Fell, Frank
    Fischer, Jurgen
    Hollmann, Rainer
    Preusker, Rene
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    An intercalibrated dataset of total column water vapour and wet tropospheric correction based on MWR on board ERS-1, ERS-2, and Envisat2017In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 10, no 4, p. 1387-1402Article in journal (Refereed)
  • 150.
    Bennet, Cecilia
    et al.
    SMHI, Research Department, Air quality.
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    A regional model for surface ozone in Southeast Asia2008In: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 60, no 5, p. 718-728Article in journal (Refereed)
    Abstract [en]

    As part of the model intercomparison study MICS Asia II, the Swedish MATCH model was set up for Southeast and East Asia. In that study, the comprehensive photochemistry scheme of MATCH was used for the first time in Asia. The current work focuses on results of surface ozone from the MATCH model simulations falling outside the model intercomparison study. Model results of surface ozone concentrations for the entire year of 2001 were investigated and compared with measurements in Southeast Asia. The model produced higher surface ozone concentrations than the observations at all of the non-remote stations investigated but underestimated during the dry season at remote locations. Modelled seasonal variation was similar to, but less pronounced than, the variation in the measurements. This study indicates that NO(x) is the limiting precursor for ozone production in the model, while the fractionation in different species and total amount of non-methane volatile organic compounds (NMVOC) emissions are less important. Naturally emitted NMVOC, isoprene, is an important precursor of surface ozone at certain conditions, and a better inventory of these emissions is needed. Deposition velocities of ozone also have impact on surface concentrations. To improve the model performance, it is important to add a land use inventory with corresponding deposition velocities.

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