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  • 2151. Woick, H
    et al.
    Dewitte, S
    Feijt, A
    Gratzki, A
    Hechler, P
    Hollmann, R
    Karlsson, Karl-Göran
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Laine, V
    Lowe, P
    Nitsche, H
    Werscheck, M
    Wollenweber, G
    The satellite application facility on climate monitoring2002Ingår i: EARTH'S ATMOSPHERE, OCEAN AND SURFACE STUDIES, 2002, nr 11, s. 2405-2410Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Satellite Application Facility on Climate Monitoring is a joint project of the National Meteorological Services and other institutes from Belgium, Finland, Germany, Sweden and The Netherlands. The objective of the project is to set up a system to provide atmospheric and oceanographic data sets from (primarily) operational geostationary and polar orbiting meteorological satellites for climate monitoring, research and applications at regional European scale, for some products on a global scale. Initial operational SAF products are related to clouds, radiation budget, ocean status and water vapour content in the atmosphere. SAF operations are foreseen to start in 2004. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

  • 2152. Wolski, Tomasz
    et al.
    Wisniewski, Bernard
    Giza, Andrzej
    Kowalewska-Kalkowska, Halina
    Boman, Hanna
    Grabbi-Kaiv, Silve
    Hammarklint, Thomas
    SMHI, Samhälle och säkerhet.
    Holfort, Juergen
    Lydeikaite, Zydrune
    Extreme sea levels at selected stations on the Baltic Sea coast2014Ingår i: Oceanologia, ISSN 0078-3234, Vol. 56, nr 2, s. 259-290Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this article is to analyse and describe the extreme characteristics of the water levels and illustrate them as the topography of the sea surface along the whole Baltic Sea coast. The general pattern is to show the maxima and minima of Baltic Sea water levels and the extent of their variations in the period from 1960 to 2010. A probability analysis is carried out on the annual sea level maxima and minima for 31 water level gauges in order to define the probability of occurrence of theoretical sea levels once in a specific number of years. The spatial distribution of sea levels for hundred-year maximum and minimum water levels is illustrated. Then, the number of storm surges for the accepted criteria are presented: these numbers increased in the 50-year period analysed. The final part of the work analyses some extreme storm events and calculates the static value and dynamic deformation of the sea surface by mesoscale, deep low-pressure systems.

  • 2153. Wolters, L
    et al.
    Cats, G
    Gustafsson, Nils
    SMHI, Forskningsavdelningen, Meteorologi.
    Wilhelmsson, T
    Data-parallel numerical methods in a weather forecast model1995Ingår i: Applied Numerical Mathematics, ISSN 0168-9274, E-ISSN 1873-5460, Vol. 19, nr 1-2, s. 159-171Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The results presented in this paper are part of a research project to investigate the possibilities to apply massively parallel architectures for numerical weather forecasting. Within numerical weather forecasting several numerical techniques are used to solve the model equations. This paper compares the performance of implementations on a MasPar system of two techniques, finite difference and spectral, that are adopted in the numerical weather forecasting model HIRLAM. The operational HIRLAM model is based on finite difference methods, while the spectral model is still in a research phase. Also the differences in relative performance of these methods on the MasPar and vector architectures will be discussed.

  • 2154. Worman, A.
    et al.
    Lindström, Göran
    SMHI, Forskningsavdelningen, Hydrologi.
    Riml, Joakim
    SMHI, Forskningsavdelningen, Hydrologi.
    The power of runoff2017Ingår i: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 548, s. 784-793Artikel i tidskrift (Refereegranskat)
  • 2155. Worman, Anders
    et al.
    Lindström, Göran
    SMHI, Forskningsavdelningen, Hydrologi.
    Akesson, Anna
    Riml, Joakim
    SMHI, Forskningsavdelningen, Hydrologi.
    Drifting runoff periodicity during the 20th century due to changing surface water volume2010Ingår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 24, nr 26, s. 3772-3784Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fourier and wavelet analyses were used to reveal the dominant trends and coherence of a more than one-century-long time series of precipitation and discharge in several watersheds in Sweden, two of which were subjected to hydropower and intensive agriculture. During the 20th century, there was a gradual, significant drift of the dominant discharge periodicity in agricultural watersheds. This study shows that the steepness of the Fourier spectrum of runoff from the May to October period each year increased gradually during the century, which suggests a more predictable intra-annual runoff pattern (more apart from white-noise). In the agricultural watershed, the coherence spectrum of precipitation and runoff is generally high with a consistent white-noise relationship for precipitation during the 20th century, indicating that precipitation is not controlling the drift of the discharge spectrum. In the hydropower regulated watershed, there was a sudden decrease of the discharge spectrum slope when regulation commenced in the 1920s. This study develops a new theory in which the runoff spectrum is related to the hydraulic and hydro-morphological characteristics of the watershed. Using this theory, we explain the changes in runoff spectra in the two watersheds by the anthropogenic change in surface water volume and, hence, changes in kinematic wave celerity and water transit times. The reduced water volume in the agricultural watershed would also contribute to decreasing evaporation, which could explain a slightly increasing mean discharge during the 20th century despite the fact that precipitation was statistically constant in the area. Copyright (C) 2010 John Wiley & Sons, Ltd.

  • 2156. Wormbs, N.
    et al.
    Nilsson, A.E.
    Doescher, Ralf
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Sörlin, S.
    The History of Emerging Arctic Climate Modelling, poster presented at the IPY final conference in Oslo2010Konferensbidrag (Övrigt vetenskapligt)
  • 2157. Wramneby, Anna
    et al.
    Smith, Benjamin
    Samuelsson, Patrick
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Hot spots of vegetation-climate feedbacks under future greenhouse forcing in Europe2010Ingår i: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 115, artikel-id D21119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 2158. Wu, Dong L.
    et al.
    Baum, Bryan A.
    Choi, Yong-Sang
    Foster, Michael J.
    Karlsson, Karl-Göran
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Heidinger, Andrew
    Poulslsen, Caroline
    Pavolonis, Michael
    Riedi, Jerome
    Roebeling, Robert
    Sherwood, Steven
    Thoss, Anke
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Watts, Philip
    TOWARD GLOBAL HARMONIZATION OF DERIVED CLOUD PRODUCTS2017Ingår i: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 98, nr 2, s. ES49-ES52Artikel i tidskrift (Refereegranskat)
  • 2159. Wu, Minchao
    et al.
    Schurgers, Guy
    Rummukainen, Markku
    SMHI, Samhälle och säkerhet.
    Smith, Benjamin
    Samuelsson, Patrick
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jansson, Christer
    Siltberg, Joe
    May, Wilhelm
    Vegetation-climate feedbacks modulate rainfall patterns in Africa under future climate change2016Ingår i: Earth System Dynamics, ISSN 2190-4979, E-ISSN 2190-4987, Vol. 7, nr 3, s. 627-647Artikel i tidskrift (Refereegranskat)
  • 2160. Wulff, A.
    et al.
    Karlberg, M.
    Olofsson, M.
    Torstensson, A.
    Riemann, L.
    Steinhoff, F. S.
    Chierici, M.
    Mohlin, Malin
    SMHI.
    Ekstrand, N.
    THE FUTURE FOR BALTIC CYANOBACTERIA?2017Ingår i: Phycologia, ISSN 0031-8884, E-ISSN 2330-2968, Vol. 56, nr 4, s. 199-200Artikel i tidskrift (Refereegranskat)
  • 2161. Wulff, Angela
    et al.
    Karlberg, Maria
    Olofsson, Malin
    Torstensson, Anders
    Riemann, Lasse
    Steinhoff, Franciska S.
    Mohlin, Malin
    SMHI.
    Ekstrand, Nina
    Chierici, Melissa
    Ocean acidification and desalination: climate-driven change in a Baltic Sea summer microplanktonic community2018Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 165, nr 4, artikel-id 63Artikel i tidskrift (Refereegranskat)
  • 2162. WULFF, F
    et al.
    Rahm, Lars
    SMHI, Forskningsavdelningen, Oceanografi.
    LONG-TERM, SEASONAL AND SPATIAL VARIATIONS OF NITROGEN, PHOSPHORUS AND SILICATE IN THE BALTIC - AN OVERVIEW1988Ingår i: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 26, nr 1, s. 19-37Artikel i tidskrift (Refereegranskat)
  • 2163. WULFF, F
    et al.
    STIGEBRANDT, A
    Rahm, Lars
    SMHI, Forskningsavdelningen, Oceanografi.
    NUTRIENT DYNAMICS OF THE BALTIC SEA1990Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 19, nr 3, s. 126-133Artikel i tidskrift (Refereegranskat)
  • 2164.
    Wyser, Klaus
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Modeled and observed clouds during Surface Heat Budget of the Arctic Ocean (SHEBA)2005Ingår i: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 110, nr D9, artikel-id D09207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 2165.
    Wyser, Klaus
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Du, P.
    Girard, E.
    Willen, Ulrika
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Cassano, J.
    Christensen, J. H.
    Curry, J. A.
    Dethloff, K.
    Haugen, J. -E
    Jacob, D.
    Koltzow, M.
    Laprise, R.
    Lynch, A.
    Pfeifer, S.
    Rinke, A.
    Serreze, M.
    Shaw, M. J.
    Tjernstrom, M.
    Zagar, M.
    An evaluation of Arctic cloud and radiation processes during the SHEBA year: simulation results from eight Arctic regional climate models2008Ingår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 30, nr 2-3, s. 203-223Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 2166.
    Wyser, Klaus
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Willén, Ulrika
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Modelling clouds and radiation in the Arctic2005Ingår i: Extended abstracts of a WMO/WCRP-sponsored Regional-Scale Climate Modelling Workshop [Elektronisk resurs] : high-resolution climate modelling : assessment, added value and applications / [ed] Lars Bärring & René Laprise, Lund: Department of Physical Geography & Ecosystems Analysis, Lund University , 2005, s. 128-Konferensbidrag (Övrigt vetenskapligt)
  • 2167.
    Wyser, Klaus
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Willén, Ulrika
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Modelling clouds and radiation in the ARctic.2004Ingår i: 14th International conference on clouds and precipitation, 2004, s. 1442-1445Konferensbidrag (Övrigt vetenskapligt)
  • 2168.
    Wyser, Klaus
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Rummukainen, Markku
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Strandberg, Gustav
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Nordic regionalisation of a greenhouse-gas stabilisation scenario2006Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The impact of a CO2 stabilisation on the Swedish climate is investigated with the regional climate model RCA3 driven by boundary conditions obtained from a global coupled climate system model (CCSM3). The global model has been forced with observed greenhouse gas concentrations from pre-industrial conditions until today’s, and with an idealised further increase until the stabilisation level is reached. After stabilisation the model integration continues for another 150+ years in order to follow the delayed response of the climate system over a period of time.Results from the global and regional climate model are compared against observations and ECMWF reanalysis for 1961-1990. For this period, the global model is found to be too cold over Europe and with a zonal flow from the North Atlantic towards Europe that is too strong. The climate of the driving global model controls the climate of the regional model and the same deviations from one are thus inherited by the other. We therefore analyse the relative climate changes differences, or ratios, of climate variables between future's and today's climate.Compared to pre-industrial conditions, the global mean temperature changes by about 1.5oC as a result of the stabilisation at 450 ppmv equivalent CO2. Averaged over Europe, the temperature change is slightly larger, and it is even larger for Sweden and Northern Europe. Annual mean precipitation for Europe is unaffected, but Sweden receives more precipitation under higher CO2 levels. The inter-annual and decadal variability of annual mean temperature and precipitation does not change with any significant degree.The changes in temperature and precipitation are not evenly distributed with the season: the largest warming and increased precipitation in Northern Europe occurs during winter months while the summer climate remains more or less unchanged. The opposite is true for the Mediterranean region where the precipitation decreases mostly during summer. This also implies higher summer temperatures, but changes in winter are smaller. No substantial change in the wind climate over Europe is found.

  • 2169.
    Wåhlstrom, Irene
    et al.
    SMHI, Forskningsavdelningen, Oceanografi.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    A model sensitivity study for the sea-air exchange of methane in the Laptev Sea, Arctic Ocean2014Ingår i: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 66, artikel-id 24174Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ocean's sinks and sources determine the concentration of methane in the water column and by that regulating the emission of methane to the atmosphere. In this study, we investigate how sensitive the sea-air exchange of methane is to increasing/decreasing sinks and sources as well as changes of different drivers with a time-dependent biogeochemical budget model for one of the shallow shelf sea in the Siberian Arctic, the Laptev Sea. The applied changes are: increased air temperature, river discharge, wind, atmospheric methane, concentration of nutrients in the river runoff or flux of methane from the sediment. Furthermore, simulations are performed to examine how the large range in observations for methane concentration in the Lena River as well as the rate of oxidation affects the net sea-air exchange. In addition, a simulation with five of these changes applied together was carried out to simulate expected climate change at the end of this century. The result indicates that none of the simulations changed the seawater to becoming a net sink for atmospheric methane and all simulations except three increased the outgassing to the atmosphere. The three exceptions were: doubling the atmospheric methane, decreasing the rivers' concentration of methane and increasing the oxidation rate where the latter is one of the key mechanisms controlling emission of methane to the atmosphere.

  • 2170.
    Wåhlström, Irene
    et al.
    SMHI, Forskningsavdelningen, Oceanografi.
    Dieterich, Christian
    SMHI, Forskningsavdelningen, Oceanografi.
    Pemberton, Per
    SMHI, Forskningsavdelningen, Oceanografi.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Impact of increasing inflow of warm Atlantic water on the sea-air exchange of carbon dioxide and methane in the Laptev Sea2016Ingår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, nr 7, s. 1867-1883Artikel i tidskrift (Refereegranskat)
  • 2171.
    Wåhlström, Irene
    et al.
    SMHI, Forskningsavdelningen, Oceanografi.
    Eilola, Kari
    SMHI, Forskningsavdelningen, Oceanografi.
    Edman, Moa
    SMHI, Forskningsavdelningen, Oceanografi.
    Almroth-Rosell, Elin
    SMHI, Forskningsavdelningen, Oceanografi.
    Evaluation of open sea boundary conditions for the coastal zone. A model study in the northern part of the Baltic Proper.2017Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Miljötillståndet i Sveriges kustvatten är starkt kopplat till tillståndet i det öppna havet på grund av det stora vattenutbytet mellan dessa. Det är därför viktigt att modeller utvecklade för kustzonens vatten har drivning från utsjön av god kvalitet med bra täckning i tid och rum samt med information om de variabler som krävs.

    För att beräkna vattenkvalitén i kustnära vatten har SMHI utvecklat en modell kallad kustzonsmodellen (SCM). Den drivs för närvarande från öppna havet av resultatfiler från en en-dimensionell modell som med hjälp av observationer har korrigerat och förbättrat modellresultaten. Tyvärr är dessa observationer undermåliga i tid och rum, och saknar nödvändiga variabler för att få bra drivning av SCM modellen. Dessa mätstationer ligger också längre ut i öppna havet och kan därför underskatta variabiliteten närmare kusten för de olika parametrarna. Dessa problem löses delvis med den en-dimensionella modellen som beräknar alla de variabler som är nödvändiga i SCM. Dock är dessa resultat inte användbara om man vill undersöka en historisk period eller framtida klimatförändringar i kustzonen. På grund av dessa tillkortakommanden undersöker vi i denna studie om det är möjligt att istället ersätta dagens drivning från öppna havet med resultat från en tre-dimensionell, kopplad fysisk och biogeokemisk modell för Östersjön som drivning för SCM, framförallt för att undersöka de två ovan nämnda perioder.

    I denna studie har sju känslighetsexperiment utförts i en pilotstudie för Norra Östersjön, inklusive Stockholms skärgård. De sju känslighetsexperimenten utfördes för att utvärdera olika metoder att extrahera resultat-filer från den tre-dimensionella modellen RCO-SCOBI med avsikt att användas som drivning för SCM. RCO-SCOBI är en modell för Östersjön med hög horisontell och vertikal upplösning av de variabler som krävs. Resultaten för både de fysiska och biogeokemiska processerna från de olika testen undersöktes och utvärderades mot observationer i kustzonen med hjälp av en statistisk metod.

    Slutsaten från dessa test är att resultatfiler från RCO-SCOBI är tillämpbara som utsjödrivning för SCM. Den bästa metoden är att extrahera en djupprofil per variabel för varje ytterbassäng i SCM i en punkt 10 nautiska mil österut och 10 nautiska mil söderut i egentliga Östersjön eller norrut i Bottenhavet för varje ytterbassäng i SCM.

  • 2172. Xavier, Prince K.
    et al.
    Petch, Jon C.
    Klingaman, Nicholas P.
    Woolnough, Steve J.
    Jiang, Xianan
    Waliser, Duane E.
    Caian, Mihaela
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Cole, Jason
    Hagos, Samson M.
    Hannay, Cecile
    Kim, Daehyun
    Miyakawa, Tomoki
    Pritchard, Michael S.
    Roehrig, Romain
    Shindo, Eiki
    Vitart, Frederic
    Wang, Hailan
    Vertical structure and physical processes of the Madden-Julian Oscillation: Biases and uncertainties at short range2015Ingår i: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 120, nr 10, s. 4749-4763Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 2173.
    Xingnan, Zhang
    SMHI.
    A comparative study of the HBV model and development of an automatic calibration scheme1994Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report contains a compari on between two rainfall-runoff models, namely the Swedish HBV model and the Chinese Xinanjiang medel, together with some examples of applications of the two models. It further contains a more detailed study of automatic calibration schemes for the HBV model, as well as the development of a new optimization scheme. The work was carried out by Dr ZHANG Xingnan, on a six month research leave from the Hohai University in Nanjing, China. Dr ZHANGs stay at the Swedish Meteorological and Hydrological lnstitute was made possible by a grant from the Swedish lnstitute. Dr ZHANG worked in close cooperation with the staff of the SMID. The work presented herein was done within the framework of the HBV-2000 project. This project is a revision of the HBV model structure, which has remained relatively unchanged since its development some twenty years ago.

  • 2174.
    Yacoub, Tahsin
    et al.
    SMHI, Samhälle och säkerhet.
    Sanner, Håkan
    SMHI, Samhälle och säkerhet.
    Vattenståndsprognoser baserade på översiktlig kartering: En fallstudie2006Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Räddningsverket,numera MSB, (Myndigheten för Samhällsskydd och Beredskap) finansierar forskningsprojektet ”Översvämningsprognoser - Utveckling av metoder för ett rikstäckande system” som bedrivs på SMHI. Den här rapporten redovisar resultaten från delprojektet ”Vattenståndsprognoser”. Projektet syfte har varit att i fallstudier utvärdera i vilka typer av vattendrag som översiktliga data ger en tillräcklig noggrannhet i prognosticerat vattenstånd. Fallstudier har genomförts för Byälven, Emån, Eskilstunaån och Lagan vid Ljungby. Ursprungligen var det tänkt att den geografiska spridningen skulle vara större, men tillgången på data har fått styra valet av områden. I Byälven och Emån har den hydrauliska modellen, som användes vid Räddningsverkets (numera MSB, Myndigheten för Samhällsskydd och Beredskap), översiktliga översvämningskartering, jämförts med observerade vattenstånd som inte använts vid kalibreringen. För Eskilstunaån och Lagan vid Ljungby har detaljerade hydrauliska modeller satts upp efter det att den översiktliga hydrauliska modellen gjordes. Dessa har här använts i stället för mätningar för att uppskatta vilken noggrannhet den översiktliga hydrauliska modellen ger och hur den skulle kunna förbättras under ett flöde genom korrigering/ uppdatering mot uppmätta värden.Resultaten visar att den översiktliga hydrauliska modellen oftast ger förvånansvärt bra noggrannhet, men stora fel kan finnas på enstaka platser. Brist på regleringsuppgifter och osäkerheter vattenföringsprognoser har oftast större betydelse för osäkerheten i vattenståndsprognoserna än brist i noggrannhet i den översiktliga hydrauliska modellen. De tankar som finns om att låta räddningstjänsten observera vattenstånd vid broar under ett flöde för att förbättra vattenståndsprognoserna får stöd av resultaten.

  • 2175.
    Yacoub, Tahsin
    et al.
    SMHI, Samhälle och säkerhet.
    Westman, Ylva
    SMHI, Samhälle och säkerhet.
    Sanner, Håkan
    SMHI, Samhälle och säkerhet.
    Samuelsson, Bernth
    SMHI, Samhälle och säkerhet.
    Detaljerad översvämningskarta för Eskilstunaån. Ett projekt inom KRIS-GIS2005Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    SMHI har gjort en detaljerad översvämningskarta för en 23 km lång sträcka längs Eskilstunaån, från utloppet av Närsjöfjärden och ned till mynningen i Mälaren. Arbetet har drivits som ett projekt inom KRIS-GIS ® och finansierats till hälften av KBM (via Lantmäteriets Totalförsvarsenhet) och till häften av SMHI. En jämförelse mellan den framtagna detaljerade översvämningskarteringen och den av Räddningsverket (numera MSB, Myndigheten för Samhällsskydd och Beredskap) finansierade översiktliga översvämningskarteringen för Eskilstunaån har också genomförts. En laserskannad höjdmodell med hög noggrannhet har tagits fram och en ekolodning av Eskilstunaån har genomförts. Med bland annat detta underlagsmaterial har den detaljerade karteringen genomförts. De hydrauliska beräkningarna har förbättrats av den mer detaljerade höjddatabasen och djupmätningarna. Vattenståndsberäkningarna i den översiktliga översvämningskarteringen är oftast förvånansvärt bra, men stora fel kan finnas på kortare sträckor längs vattendraget. Det beror på och är beroende av mängden och kvalitén på extrainformationen som inhämtas, såsom broritningar, dammuppgifter, vattenståndsuppgifter från tidigare flöden och tidigare inventeringar. De översvämmade områdena skiljer relativt mycket mellan den detaljerade och den översiktliga översvämningskarteringen. Den huvudsakliga orsaken är skillnaden mellan höjddatabaserna.

  • 2176.
    Yang, Wei
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Andreasson, Johan
    SMHI, Affärsverksamhet.
    Graham, Phil
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Olsson, Jonas
    SMHI, Forskningsavdelningen, Hydrologi.
    Rosberg, Jörgen
    SMHI, Forskningsavdelningen, Hydrologi.
    Wetterhall, Fredrik
    SMHI, Forskningsavdelningen, Hydrologi.
    Distribution-based scaling to improve usability of regional climate model projections for hydrological climate change impacts studies2010Ingår i: HYDROLOGY RESEARCH, ISSN 1998-9563, Vol. 41, nr 3-4, s. 211-229Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As climate change could have considerable influence on hydrology and corresponding water management, appropriate climate change inputs should be used for assessing future impacts. Although the performance of regional climate models (RCMs) has improved over time, systematic model biases still constrain the direct use of RCM output for hydrological impact studies. To address this, a distribution-based scaling (DBS) approach was developed that adjusts precipitation and temperature from RCMs to better reflect observations. Statistical properties, such as daily mean, standard deviation, distribution and frequency of precipitation days, were much improved for control periods compared to direct RCM output. DBS-adjusted precipitation and temperature from two IPCC Special Report on Emissions Scenarios (SRESA1B) transient climate projections were used as inputs to the HBV hydrological model for several river basins in Sweden for the period 1961-2100. Hydrological results using DBS were compared to results with the widely-used delta change (DC) approach for impact studies. The general signal of a warmer and wetter climate was obtained using both approaches, but use of DBS identified differences between the two projections that were not seen with DC. The DBS approach is thought to better preserve the future variability produced by the RCM, improving usability for climate change impact studies.

  • 2177.
    Yang, Wei
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Bardossy, Andras
    Caspary, Hans-Joachim
    Downscaling daily precipitation time series using a combined circulation- and regression-based approach2010Ingår i: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483, Vol. 102, nr 3-4, s. 439-454Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this paper is to introduce a new conditional statistical model for generating daily precipitation time series. The generated daily precipitation can thus be used for climate change impact studies, e.g., crop production, rainfall-runoff, and other water-related processes. It is a stochastic model that links local rainfall events to a continuous atmospheric predictor, moisture flux, in addition to classified atmospheric circulation patterns. The coupled moisture flux is proved to be capable of capturing continuous property of climate system and providing extra information to determine rainfall probability and rainfall amount. The application was made to simultaneously downscale daily precipitation at multiple sites within the Rhine River basin. The results show that the model can well reproduce statistical properties of daily precipitation time series. Especially for extreme rainfall events, the model is thought to better reflect rainfall variability compared to the pure CP-based downscaling approach.

  • 2178.
    Yang, Wei
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Gardelin, Marie
    SMHI, Affärsverksamhet.
    Olsson, Jonas
    SMHI, Forskningsavdelningen, Hydrologi.
    Bosshard, Thomas
    SMHI, Forskningsavdelningen, Hydrologi.
    Multi-variable bias correction: application of forest fire risk in present and future climate in Sweden2015Ingår i: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 15, nr 9, s. 2037-2057Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As the risk of a forest fire is largely influenced by weather, evaluating its tendency under a changing climate becomes important for management and decision making. Currently, biases in climate models make it difficult to realistically estimate the future climate and consequent impact on fire risk. A distribution-based scaling (DBS) approach was developed as a post-processing tool that intends to correct systematic biases in climate modelling outputs. In this study, we used two projections, one driven by historical reanalysis (ERA40) and one from a global climate model (ECHAM5) for future projection, both having been dynamically down-scaled by a regional climate model (RCA3). The effects of the post-processing tool on relative humidity and wind speed were studied in addition to the primary variables precipitation and temperature. Finally, the Canadian Fire Weather Index system was used to evaluate the influence of changing meteorological conditions on the moisture content in fuel layers and the fire-spread risk. The forest fire risk results using DBS are proven to better reflect risk using observations than that using raw climate outputs. For future periods, southern Sweden is likely to have a higher fire risk than today, whereas northern Sweden will have a lower risk of forest fire.

  • 2179. Yin, Yunxing
    et al.
    Jiang, Sanyuan
    Pers, Charlotta
    SMHI, Forskningsavdelningen, Hydrologi.
    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 Model2016Ingår i: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 13, nr 3Artikel i tidskrift (Refereegranskat)
    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.

  • 2180. Yom-Tov, Elad
    et al.
    Yom-Tov, Yoram
    Yom-Tov, Shlomith
    Andersen, Mogens
    Rosenfeld, Daniel
    Devasthale, Abhay
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Geffen, Eli
    The complex effects of geography, ambient temperature, and North Atlantic Oscillation on the body size of Arctic hares in Greenland2017Ingår i: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 120, nr 4, s. 909-918Artikel i tidskrift (Refereegranskat)
  • 2181. Yttri, Karl Espen
    et al.
    Simpson, David
    Bergström, Robert
    SMHI, Forskningsavdelningen, Luftmiljö.
    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 Europe2019Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 19, nr 7, s. 4211-4233Artikel i tidskrift (Refereegranskat)
  • 2182. Yurkin, Maxim A.
    et al.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    Light scattering by a cube: Accuracy limits of the discrete dipole approximation and the T-matrix method2013Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 123, s. 176-183Artikel i tidskrift (Refereegranskat)
    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.

  • 2183.
    Zachrisson, Gun
    SMHI.
    Svåra islossningar i Torneälven: Förslag till skadeförebyggande åtgärder1989Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    BakgrundEfter den svåra islossningen i Torneälven 1984 inleddes diskussioner om möjliga åtgärder för att minska skadeverkningama av svåra islossningar i framtiden. Ett förslag till treårsprojekt lades fram av SMHI och Vatten- och miljöstyrelsen (VMS) gemensamt (se figur 1.1). Syftet var att ta fram ett åtgärdsprogram omfattande dels ett prognos- och varningssystem för vårflod och issituation, dels förslag till skadeförebyggande tekniska åtgärder. Projektet startade formellt våren 1986 sedan medel för den svenska delen av arbetet  tällts till förfogande av Civildepartementet. From 1987/88 har Statens Räddningsverk svarat för finansieringen av de svenska insatserna. Den finska delen av projektet har bedrivits inom ramen för Vatten- och miljöstyrelsens ordinarie verksamhet. Resultaten av verksamheten under de gångna tre åren presenteras i föreliggande förslag till åtgärdsprogram.

  • 2184. Zadra, Ayrton
    et al.
    Caya, Daniel
    Coté, Jean
    Dugas, Bernard
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Laprise, René
    Winger, Katja
    Caron, Louis-Philippe
    The next Canadian Regional Climate Model.2008Ingår i: Physics in Canada, Vol. 64, nr 2Artikel i tidskrift (Refereegranskat)
  • 2185. Zampieri, M.
    et al.
    Giorgi, F.
    Lionello, P.
    Nikulin, Grigory
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Regional climate change in the Northern Adriatic2012Ingår i: Physics and Chemistry of the Earth, ISSN 1474-7065, E-ISSN 1873-5193, Vol. 40-41, s. 32-46Artikel i tidskrift (Refereegranskat)
    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.

  • 2186. Zandersen, Marianne
    et al.
    Hyytiainen, Kari
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    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 problems2019Ingår i: Regional Environmental Change, ISSN 1436-3798, E-ISSN 1436-378X, Vol. 19, nr 4, s. 1073-1086Artikel i tidskrift (Refereegranskat)
  • 2187. Zaplotnik, Ziga
    et al.
    Zagar, Nedjeljka
    Gustafsson, Nils
    SMHI, Forskningsavdelningen, Meteorologi.
    An intermediate-complexity model for four-dimensional variational data assimilation including moist processes2018Ingår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 144, nr 715, s. 1772-1787Artikel i tidskrift (Refereegranskat)
  • 2188. Zarekarizi, Mahkameh
    et al.
    Rana, Arun
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Moradkhani, Hamid
    Precipitation extremes and their relation to climatic indices in the Pacific Northwest USA2018Ingår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, nr 11-12, s. 4519-4537Artikel i tidskrift (Refereegranskat)
  • 2189.
    Zengmao, Wu
    SMHI.
    Numerical analysis of initialization procedure in a two-dimensional lake breeze model1986Rapport (Övrigt vetenskapligt)
  • 2190.
    Zengmao, Wu
    SMHI.
    Numerical study of lake-land breeze over Lake Vättern, Sweden1986Rapport (Övrigt vetenskapligt)
  • 2191. Zerefos, Christos S.
    et al.
    Eleftheratos, Kostas
    Kapsomenakis, John
    Solomos, Stavros
    Inness, Antje
    Balis, Dimitris
    Redondas, Alberto
    Eskes, Henk
    Allaart, Marc
    Amiridis, Vassilis
    Dahlback, Arne
    De Bock, Veerle
    Diemoz, Henri
    Engelmann, Ronny
    Eriksen, Paul
    Fioletov, Vitali
    Grobner, Julian
    Heikkila, Anu
    Petropavlovskikh, Irina
    Jaroslawski, Janusz
    Josefsson, Weine
    SMHI, Samhälle och säkerhet.
    Karppinen, Tomi
    Koehler, Ulf
    Meleti, Charoula
    Repapis, Christos
    Rimmer, John
    Savinykh, Vladimir
    Shirotov, Vadim
    Siani, Anna Maria
    Smedley, Andrew R. D.
    Stanek, Martin
    Stubi, Rene
    Detecting volcanic sulfur dioxide plumes in the Northern Hemisphere using the Brewer spectrophotometers, other networks, and satellite observations2017Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, nr 1, s. 551-574Artikel i tidskrift (Refereegranskat)
  • 2192. Zhang, Daoxi
    et al.
    Lavender, Samantha
    Muller, Jan-Peter
    Walton, David
    Karlson, Bengt
    SMHI, Forskningsavdelningen, Oceanografi.
    Kronsell, Johan
    SMHI, Samhälle och säkerhet.
    Determination of phytoplankton abundances (Chlorophyll-a) in the optically complex inland water - The Baltic Sea2017Ingår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 601, s. 1060-1074Artikel i tidskrift (Refereegranskat)
  • 2193. Zhang, Jianzhong
    et al.
    Kuenzer, Claudia
    Tetzlaff, Anke
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Oertel, Dieter
    Zhukov, Boris
    Wagner, Wolfgang
    Thermal characteristics of coal fires 2: Results of measurements on simulated coal fires2007Ingår i: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 63, nr 3-4, s. 135-147Artikel i tidskrift (Refereegranskat)
    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.

  • 2194. Zhang, Linus
    et al.
    Gustafsson, David
    SMHI, Forskningsavdelningen, Hydrologi.
    Editorial: 'The Nordic Hydrology Model' - Linking science and practice2016Ingår i: HYDROLOGY RESEARCH, ISSN 1998-9563, Vol. 47, nr 4, s. 671-671Artikel i tidskrift (Refereegranskat)
  • 2195. Zhang, W.
    et al.
    Jansson, Christer
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Miller, P. A.
    Smith, B.
    Samuelsson, Patrick
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Biogeophysical feedbacks enhance the Arctic terrestrial carbon sink in regional Earth system dynamics2014Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, nr 19, s. 5503-5519Artikel i tidskrift (Refereegranskat)
    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.

  • 2196. Zhang, W.
    et al.
    Miller, P. A.
    Jansson, C.
    Samuelsson, Patrick
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Mao, J.
    Smith, B.
    Self-Amplifying Feedbacks Accelerate Greening and Warming of the Arctic2018Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, nr 14, s. 7102-7111Artikel i tidskrift (Refereegranskat)
  • 2197. Zhang, Wenxin
    et al.
    Miller, Paul A.
    Smith, Benjamin
    Wania, Rita
    Koenigk, Torben
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Doescher, Ralf
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Tundra shrubification and tree-line advance amplify arctic climate warming: results from an individual-based dynamic vegetation model2013Ingår i: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 8, nr 3, artikel-id 034023Artikel i tidskrift (Refereegranskat)
    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.

  • 2198. Zhang, X N
    et al.
    Lindström, Göran
    SMHI, Forskningsavdelningen, Hydrologi.
    A comparative study of a Swedish and a Chinese hydrological model1996Ingår i: WATER RESOURCES BULLETIN, ISSN 0043-1370, Vol. 32, nr 5, s. 985-994Artikel i tidskrift (Refereegranskat)
    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.

  • 2199. Zilitinkevich, S S
    et al.
    Perov, Veniamin
    SMHI, Forskningsavdelningen, Meteorologi.
    King, J C
    Near-surface turbulent fluxes in stable stratification: Calculation techniques for use in general-circulation models2002Ingår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 128, nr 583, s. 1571-1587Artikel i tidskrift (Refereegranskat)
    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.

  • 2200. Zunckel, M
    et al.
    Robertson, Lennart
    SMHI, Forskningsavdelningen, Luftmiljö.
    Tyson, P D
    Rodhe, H
    Modelled transport and deposition of sulphur over Southern Africa2000Ingår i: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 34, nr 17, s. 2797-2808Artikel i tidskrift (Refereegranskat)
    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.

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