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Träfflista för sökning "hsv:(NATURVETENSKAP) hsv:(Geovetenskap och miljövetenskap) hsv:(Oceanografi hydrologi och vattenresurser) ;pers:(Lundin L C)"

Sökning: hsv:(NATURVETENSKAP) hsv:(Geovetenskap och miljövetenskap) hsv:(Oceanografi hydrologi och vattenresurser) > Lundin L C

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1.
  • Hansson, Klas, et al. (författare)
  • Water content reflectometer application to construction materials and its relation to time domain reflectometry
  • 2006
  • Ingår i: Vadose Zone Journal. - : Wiley. - 1539-1663. ; 5:1, s. 459-468
  • Tidskriftsartikel (refereegranskat)abstract
    • Moisture content measurements using time domain reflectometry (TDR) or water content reflectometry (WCR) are basic in many research areas. The goals of this study were to establish a relation between apparent dielectric number and WCR sensor output, to compare TDR and WCR calibration equations for two coarse road construction materials, and to investigate the influence of sampling volume for horizontally installed sensors. Measurements were performed in fluids of known dielectric number and in two incrementally saturated coarse materials. The effect of sampling volume was evaluated using an electrostatic finite-element model. A two-parameter equation was determined relating the apparent dielectric number to Campbell CS616 ( Campbell Scientific, Logan, UT) WCR output (r(2) > 0.99). A simple calibration can adapt the equation to individual CS616, or similar, sensors. For the finer, coarse material, a three-phase mixing model proved best, while for the coarser material no equation adequately described the measurements. Numerical simulations indicated that limited capillary rise, creating a rapid transition from wet to dry close to saturation, was the explanation, warranting caution when interpreting measurements in nearly saturated coarse materials.
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2.
  • Gustafsson, David, et al. (författare)
  • Boreal forest surface parameterization in the ECMWF model - 1D test with NOPEX long-term data
  • 2003
  • Ingår i: Journal of applied meteorology (1988). - 0894-8763 .- 1520-0450. ; 42:1, s. 95-112
  • Tidskriftsartikel (refereegranskat)abstract
    • The objective of the present study was to assess the performance and recent improvements of the land surface scheme used operationally in the European Centre for Medium-Range Weather Forecasts (ECMWF) in a Scandinavian boreal forest climate/ecosystem. The previous (the 1999 scheme of P. Viterbo and A. K. Betts) and the new (Tiled ECMWF Surface Scheme for Exchange Processes over Land, TESSEL) surface schemes were validated by single-column runs against data from NOPEX (Northern Hemisphere Climate-Processes Land-Surface Experiment). Driving and validation datasets were prepared for a 3-yr period (1994-96). The new surface scheme, with separate surface energy balances for subgrid fractions (tiling), improved predictions of seasonal as well as diurnal variation in surface energy fluxes in comparison with the old scheme. Simulated wintertime evaporation improved significantly as a consequence of the introduced additional aerodynamic resistance for evaporation from snow lying under high vegetation. Simulated springtime evaporation also improved because the limitation of transpiration in frozen soils was now accounted for. However, downward sensible heat flux was still underestimated during winter, especially at nighttime, whereas soil temperatures were underestimated in winter and overestimated in summer. The new scheme also underestimated evaporation during dry periods in summer, whereas soil moisture was overestimated. Sensitivity tests showed that further improvements of simulated surface heat fluxes and soil temperatures could be obtained by calibration of parameters governing the coupling between the surface and the atmosphere and the ground heat flux, and parameters governing the water uptake by the vegetation. Model performance also improved when the seasonal variation in vegetation properties was included.
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4.
  • Halldin, S, et al. (författare)
  • Continuous long-term measurements of soil-plant-atmosphere variables at an agricultural site
  • 1999
  • Ingår i: AGRICULTURAL AND FOREST METEOROLOGY. - : ELSEVIER SCIENCE BV. - 0168-1923. ; 98-9, s. 75-102
  • Tidskriftsartikel (refereegranskat)abstract
    • It is a major challenge in modem science to decrease the uncertainty in predictions of global climate change. One of the largest uncertainties in present-day global climate models resides with the understanding of processes in the soil-vegetation-atmosphe
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5.
  • Halldin, S, et al. (författare)
  • NOPEX - a northern hemisphere climate processes land surface experiment
  • 1998
  • Ingår i: JOURNAL OF HYDROLOGY. - : ELSEVIER SCIENCE BV. - 0022-1694. ; 213:1-4, s. 172-187
  • Tidskriftsartikel (refereegranskat)abstract
    • The interface between land surfaces and the atmosphere is a key area in climate research, where lack of basic knowledge prevents us from reducing the considerable uncertainties about predicted changes. Boreal forests play an important, but not well known,
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7.
  • Erlingsson, U, et al. (författare)
  • Geology of the Baltic Sea basin
  • 2003
  • Ingår i: Environmental Science. - : The Baltic University Press, Uppsala. ; , s. 98-99
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
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9.
  • Halldin, S, et al. (författare)
  • Energy, water and carbon exchange in a boreal forest landscape - NOPEX experiences
  • 1999
  • Ingår i: AGRICULTURAL AND FOREST METEOROLOGY. - : ELSEVIER SCIENCE BV. ; 98-9, s. 5-29
  • Recension (övrigt vetenskapligt/konstnärligt)abstract
    • The role of the land surface in controlling climate is still underestimated and access to information from the boreal-forest zone is instrumental to improve this situation. This motivated the organisation of NOPEX (Northern hemisphere climate-Processes la
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  • Resultat 1-10 av 65

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