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  • 1651. Yin, Yunxing
    et al.
    Jiang, Sanyuan
    Pers, Charlotta
    SMHI, Research Department, Hydrology.
    Yang, Xiaoying
    Liu, Qun
    Yuan, Jin
    Yao, Mingxing
    He, Yi
    Luo, Xingzhang
    Zheng, Zheng
    Assessment of the Spatial and Temporal Variations of Water Quality for Agricultural Lands with Crop Rotation in China by Using a HYPE Model2016In: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 13, no 3Article in journal (Refereed)
    Abstract [en]

    Many water quality models have been successfully used worldwide to predict nutrient losses from anthropogenically impacted catchments, but hydrological and nutrient simulations with limited data are difficult considering the transfer of model parameters and complication of model calibration and validation. This study aims: (i) to assess the performance capabilities of a new and relatively more advantageous model, namely, Hydrological Predictions for the Environment (HYPE), that simulates stream flow and nutrient load in agricultural areas by using a multi-site and multi-objective parameter calibration method and (ii) to investigate the temporal and spatial variations of total nitrogen (TN) and total phosphorous (TP) concentrations and loads with crop rotation by using the model for the first time. A parameter estimation tool (PEST) was used to calibrate parameters. Results show that the parameters related to the effective soil porosity were highly sensitive to hydrological modeling. N balance was largely controlled by soil denitrification processes. P balance was influenced by the sedimentation rate and production/decay of P in rivers and lakes. The model reproduced the temporal and spatial variations of discharge and TN/TP relatively well in both calibration (2006-2008) and validation (2009-2010) periods. Among the obtained data, the lowest Nash-Suttclife efficiency of discharge, daily TN load, and daily TP load were 0.74, 0.51, and 0.54, respectively. The seasonal variations of daily TN concentrations in the entire simulation period were insufficient, indicated that crop rotation changed the timing and amount of N output. Monthly TN and TP simulation yields revealed that nutrient outputs were abundant in summer in terms of the corresponding discharge. The area-weighted TN and TP load annual yields in five years showed that nutrient loads were extremely high along Hong and Ru rivers, especially in agricultural lands.

  • 1652. Yom-Tov, Elad
    et al.
    Yom-Tov, Yoram
    Yom-Tov, Shlomith
    Andersen, Mogens
    Rosenfeld, Daniel
    Devasthale, Abhay
    SMHI, Research Department, Atmospheric remote sensing.
    Geffen, Eli
    The complex effects of geography, ambient temperature, and North Atlantic Oscillation on the body size of Arctic hares in Greenland2017In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 120, no 4, p. 909-918Article in journal (Refereed)
  • 1653. Yttri, Karl Espen
    et al.
    Simpson, David
    Bergström, Robert
    SMHI, Research Department, Air quality.
    Kiss, Gyula
    Szidat, Sonke
    Ceburnis, Darius
    Eckhardt, Sabine
    Hueglin, Christoph
    Nojgaard, Jacob Kleno
    Perrino, Cinzia
    Pisso, Ignazio
    Prevot, Andre Stephan Henry
    Putaud, Jean-Philippe
    Spindler, Gerald
    Vana, Milan
    Zhang, Yan-Lin
    Aas, Wenche
    The EMEP Intensive Measurement Period campaign, 2008-2009: characterizing carbonaceous aerosol at nine rural sites in Europe2019In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 19, no 7, p. 4211-4233Article in journal (Refereed)
  • 1654. Yurkin, Maxim A.
    et al.
    Kahnert, Michael
    SMHI, Research Department, Air quality.
    Light scattering by a cube: Accuracy limits of the discrete dipole approximation and the T-matrix method2013In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 123, p. 176-183Article in journal (Refereed)
    Abstract [en]

    We simulated light-scattering by small and wavelength-sized cubes with three largely different values of the refractive index using the discrete dipole approximation (DDA) and the T-matrix method. Our main goal was to push the accuracy of both methods to the limit. For the DDA we used an earlier developed extrapolation technique based on simulation results for different levels of discretization. For the T-matrix method we developed a procedure to estimate a confidence range for the simulated value, using results for different values of the truncation index (number of multipoles). In most cases this confidence range was reliable, enclosing the corresponding DDA result. We present benchmark results by both methods, including estimated uncertainties, for selected integral and angle-resolved scattering quantities. Estimated relative uncertainties of the DDA result are unprecedentedly small (from 10(-7) to 10(-3)), while relative differences between the T-matrix and DDA results are larger (from 10(-4) to 0.2) in accordance with estimated T-matrix uncertainties. (C) 2012 Elsevier Ltd. All rights reserved.

  • 1655. Zadra, Ayrton
    et al.
    Caya, Daniel
    Coté, Jean
    Dugas, Bernard
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Laprise, René
    Winger, Katja
    Caron, Louis-Philippe
    The next Canadian Regional Climate Model.2008In: Physics in Canada, Vol. 64, no 2Article in journal (Refereed)
  • 1656. Zampieri, M.
    et al.
    Giorgi, F.
    Lionello, P.
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Regional climate change in the Northern Adriatic2012In: Physics and Chemistry of the Earth, ISSN 1474-7065, E-ISSN 1873-5193, Vol. 40-41, p. 32-46Article in journal (Refereed)
    Abstract [en]

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

  • 1657. Zandersen, Marianne
    et al.
    Hyytiainen, Kari
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Tomczak, Maciej T.
    Bauer, Barbara
    Haapasaari, Paivi E.
    Olesen, Jorgen Eivind
    Gustafsson, Bo G.
    Refsgaard, Jens Christian
    Fridell, Erik
    Pihlainen, Sampo
    Le Tissier, Martin D. A.
    Kosenius, Anna-Kaisa
    Van Vuuren, Detlef P.
    Shared socio-economic pathways extended for the Baltic Sea: exploring long-term environmental problems2019In: Regional Environmental Change, ISSN 1436-3798, E-ISSN 1436-378X, Vol. 19, no 4, p. 1073-1086Article in journal (Refereed)
  • 1658. Zaplotnik, Ziga
    et al.
    Zagar, Nedjeljka
    Gustafsson, Nils
    SMHI, Research Department, Meteorology.
    An intermediate-complexity model for four-dimensional variational data assimilation including moist processes2018In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 144, no 715, p. 1772-1787Article in journal (Refereed)
  • 1659. Zarekarizi, Mahkameh
    et al.
    Rana, Arun
    SMHI, Research Department, Climate research - Rossby Centre.
    Moradkhani, Hamid
    Precipitation extremes and their relation to climatic indices in the Pacific Northwest USA2018In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, no 11-12, p. 4519-4537Article in journal (Refereed)
  • 1660. Zhang, Daoxi
    et al.
    Lavender, Samantha
    Muller, Jan-Peter
    Walton, David
    Karlson, Bengt
    SMHI, Research Department, Oceanography.
    Kronsell, Johan
    SMHI, Core Services.
    Determination of phytoplankton abundances (Chlorophyll-a) in the optically complex inland water - The Baltic Sea2017In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 601, p. 1060-1074Article in journal (Refereed)
  • 1661. Zhang, Jianzhong
    et al.
    Kuenzer, Claudia
    Tetzlaff, Anke
    SMHI, Research Department, Atmospheric remote sensing.
    Oertel, Dieter
    Zhukov, Boris
    Wagner, Wolfgang
    Thermal characteristics of coal fires 2: Results of measurements on simulated coal fires2007In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 63, no 3-4, p. 135-147Article in journal (Refereed)
    Abstract [en]

    In this paper we present thermal characteristics of coal fires as measured during simulated fires under an experimental setting in Germany in July 2002. It is thus a continuation of the previously published paper "Thermal surface characteristics of coal fire 1: Results of in-situ measurement", in which we presented temperature measurements of real subsurface coal fires in China [Zhang, J., Kuenzer, C., accepted for publication. Thermal Surface Characteristics of Coal Fires 1: Results of in-situ measurements. Accepted for publication at Journal of Applied Geophysics.]. The focus is on simulated coal fires, which are less complex in nature than fires under natural conditions. In the present study we simulated all the influences usually occurring under natural conditions in a controllable manner (uniform background material of known thermal properties, known ventilation pathways, homogeneous coal substrate), creating two artificial outdoor coal fires under simplified settings. One surface coal fire and one subsurface coal fire were observed over the course of 2 days. The set up of the fires allowed for measurements not always feasible under "real" in-situ conditions: thus compared to the in-situ investigations presented in paper one we could retrieve numerous temperature measurements inside of the fires. Single temperature measurements, diurnal profiles and airborne thermal surveying present the typical temperature patterns of a small surface-and a subsurface fire under undisturbed conditions (easily accessible terrain, 24 hour measurements period, homogeneous materials). We found that the outside air temperature does not influence the fire's surface temperature (up to 900 degrees C), while fire centre temperatures of up to 1200 degrees C strongly correlate with surface temperatures of the fire. The fires could heat their surrounding up to a distance of 4.5 m. However, thermal anomalies on the background surface only persist as long as the fire is burning and disappear very fast if the heat source is removed. Furthermore, heat outside of the fires is transported mainly by convection and not by radiation. In spatial thermal line scanner data the diurnal thermal patterns of the coal fire are clearly represented. Our experiments during that data collection also visualize the thermal anomaly differences between covered (underground) and uncovered (surface) coal fires. The latter could not be observed in-situ in a real coal fire area. Subsurface coal fires express a much weaker signal than open surface fires and contrast only by few degrees against the background. In airborne thermal imaging scanner data the fires are also well represented. Here we could show that the mid-infrared domain (3.8 mu m) is more suitable to pick up very hot anomalies, compared to the common thermal (8.8 mu m) domain. Our results help to understand coal fires and their thermal patterns as well as the limitations occurring during their analysis. We believe that the results presented here can practicably help for the planning of coal fire thermal mapping campaigns - including remote sensing methods and the thermal data can be included into numerical coal fire modelling as initial or boundary conditions. (c) 2007 Elsevier B.V. All rights reserved.

  • 1662. Zhang, Linus
    et al.
    Gustafsson, David
    SMHI, Research Department, Hydrology.
    Editorial: 'The Nordic Hydrology Model' - Linking science and practice2016In: HYDROLOGY RESEARCH, ISSN 1998-9563, Vol. 47, no 4, p. 671-671Article in journal (Refereed)
  • 1663. Zhang, W.
    et al.
    Jansson, Christer
    SMHI, Research Department, Climate research - Rossby Centre.
    Miller, P. A.
    Smith, B.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Biogeophysical feedbacks enhance the Arctic terrestrial carbon sink in regional Earth system dynamics2014In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, no 19, p. 5503-5519Article in journal (Refereed)
    Abstract [en]

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

  • 1664. Zhang, W.
    et al.
    Miller, P. A.
    Jansson, C.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Mao, J.
    Smith, B.
    Self-Amplifying Feedbacks Accelerate Greening and Warming of the Arctic2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 14, p. 7102-7111Article in journal (Refereed)
  • 1665. Zhang, Wenxin
    et al.
    Miller, Paul A.
    Smith, Benjamin
    Wania, Rita
    Koenigk, Torben
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Tundra shrubification and tree-line advance amplify arctic climate warming: results from an individual-based dynamic vegetation model2013In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 8, no 3, article id 034023Article in journal (Refereed)
    Abstract [en]

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

  • 1666. Zhang, X N
    et al.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    A comparative study of a Swedish and a Chinese hydrological model1996In: WATER RESOURCES BULLETIN, ISSN 0043-1370, Vol. 32, no 5, p. 985-994Article in journal (Refereed)
    Abstract [en]

    There are a large number of conceptual hydrological models available today. It is not easy to immediately identify the similarities and differences between the different models. The Swedish HBV model and the Chinese Xinanjiang model are two examples of conceptual, semi-distributed, rainfall-runoff models. The Xinanjiang model was designed for use in humid and semi-humid regions, with no routine for the snowmelt runoff, whereas the snow routine is an important part of the HBV model in many applications. The model structures of the two models may be described in four routines, compared in this paper. The integral structures of them are similar, but there are some differences, especially in the runoff production routine. The physical significance and physical definitions of some model parameters were analyzed. Both models were tested in two basins. Both models gave similar results, and both models performed well in the application. The similarity of the results obtained by different model structures leads to the following two conclusions. First, more effort should probably be spent on the improvement of input data quality and coverage than on the development of more detailed model structures only. Second, inference about basin behavior and characteristics from the values of calibrated model parameters must be made with great caution.

  • 1667. Zilitinkevich, S S
    et al.
    Perov, Veniamin
    SMHI, Research Department, Meteorology.
    King, J C
    Near-surface turbulent fluxes in stable stratification: Calculation techniques for use in general-circulation models2002In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 128, no 583, p. 1571-1587Article in journal (Refereed)
    Abstract [en]

    Practically oriented flux-calculation techniques based on correction functions to the neutral drag and heat/mass transfer coefficients are further developed. In the traditional formulation, the correction functions depend only on the bulk Richardson number. However, data from measurements of turbulent fluxes and mean profiles in stable stratification over different sites exhibit too strong variability in this type of dependencies. Indirect evidence from climate and weather prediction modelling also shows that the traditional flux-calculation technique is not sufficiently advanced. It is conceivable that other mechanisms besides the surface-layer stratification and, therefore, other arguments besides the bulk Richardson number must be considered. The proposed technique includes a newly discovered effect of the static stability in the free atmosphere on the surface-layer scaling and accounts for the general essential difference between the roughness lengths for momentum and scalars. Besides bulk Richardson number, recommended correction functions depend oil one more stability parameter. involving the Brunt-Vaisala frequency in the free atmosphere, and on the roughness lengths.

  • 1668. Zunckel, M
    et al.
    Robertson, Lennart
    SMHI, Research Department, Air quality.
    Tyson, P D
    Rodhe, H
    Modelled transport and deposition of sulphur over Southern Africa2000In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 34, no 17, p. 2797-2808Article in journal (Refereed)
    Abstract [en]

    Ambient SO2 concentrations and atmospheric deposition of sulphur resulting from emissions on the industrialised highveld region of South Africa are estimated using the multi-scale atmospheric transport and chemistry (MATCH) modelling system, developed at the Swedish Meteorological and Hydrological Institute (SMHI), and compared with an inferential model driven by measured input quantities. Modelled SO, concentrations on the central highveld mostly range between 10 and 50 ppb, exceeding 50 ppb in source areas. Dry deposition rates for sulphur exhibit a similar spatial pattern to the ambient SO2 concentrations and both are consistent with synoptic-scale transport patterns. Maximum dry deposition rates for sulphur of more than 10 kg S ha(-1) a(-1) occur over the central highveld with a well-defined gradient decreasing away from the source region. Despite the significant differences in modelling approaches, the estimates of dry deposition provided by MATCH are in reasonable agreement with those of the inferential model. The maximum modelled wet deposition rates occur over the South African highveld and its periphery and range between 1 and 5 kg S ha(-1) a(-1) and compare favourably with measurements from an acid rain network. Wet deposition generally exceed dry deposition on the highveld and the adjacent areas except in the central highveld source region. Over the drier western half of South Africa MATCH-modelled dry and wet deposition rates are again similar and are less that 1 kg S ha(-1) a(-1). Wet deposition exceeds dry in the higher rainfall regions along the south and east coasts of South Africa. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.

31323334 1651 - 1668 of 1668
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