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  • 51.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Beringer, Jason
    Monash University, Melbourne, VIC.
    Albedo and snowmelt rates across a tundra-to-forest transition2005Inngår i: Proceedings of the 15 northern research basins international symposium and workshop, Lund: Department of Water Resources Engineering, Lund University , 2005, s. 1-10Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Arctic ecosystems play an important role in the functioning of the earth system because they occupy a large area, are sensitive to climate changes and could feedback to affect regional and global climate, Albedo and melt rates measured at a tundra, shrub and forest site at Council (ca 64 54N) and at a tundra site at Ivotuk (ca 68 29N) in Alaska during the snowmelt period in year 2000 showed that the difference in the timing of snowmelt was greater between vegetation types (13 days between shrub and tundra) than between the two sites of different latitude (7days between the two tundra sites with 3.6 difference in latitude). Hence any increase in the abundance and distribution of shrubs and forest could result in earlier spring melt. That the absorption of radiation used for snowmelt was greater for the shrub site than for the other sites was confirmed by degree-index simulations where the shrub site (8.2 mm C۫- 1day-1) required a much larger degree-index than the other sites (forest 3.44 mm C۫-1day-1and 4.1 tundra mm C۫-1day-1) i۫n order to correctly simulate the melt rate. The impacts of changes in snowmelt are not restricted to impacts on surface fluxes but potentially also on hydrological process, regional climate, nutrient and pollutant fluxes.

  • 52.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Beyerl, H.
    Ash on snow a tool - a tool to prevent flooding?2001Inngår i: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 32, nr 3, s. 195-214Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Years with late spring in combination with thick snow-pack constitute risk for flooding. To decrease that risk, the possibility of spreading albedo-lowering material (wood ash) on parts of a basin snow has been examined. By blackening the snow more solar radiation is absorbed and the snowmelt is enhanced. If sun-exposed parts of the basin are ash-treated (before normal runoff starts) the runoff will be distributed over a longer period of time and the risk of flooding will be reduced. Wood ash in different concentrations was spread on small snow plots and melt rates and albedo were measured. For snow covered with 0.03 kg ash m super(-2), the albedo was decreased from approximately 0.60 for natural snow to approximately 0.25, resulting in approximately 90% more absorbed short-wave radiation. Melt on the ash treated surface, (daily average snow water equivalent), was 70% larger than melt on natural snow (12 and 7 mm d super(-1) respectively). A five times larger concentration (0.15 kg m super(-2)) only increased the melt rate to 14 mm d super(-1). The temperature-index method was shown to be inadequate for modelling the melt rate for the ash treated snow. A radiation-index model, based on absorbed incoming short wave radiation, was shown to model the melt rate better than the temperature-index method.

  • 53.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Beyrel, B.
    Enhanced melt rates with wood ash: a tool to prevent flooding2000Inngår i: Nordic Hydrological Conference 2000: Uppsala, Sweden 26-30 June 2000 / [ed] Torbjörn Nilsson, Uppsala: Sveriges Lantbruksuniversitet, 2000, s. 562-569Konferansepaper (Fagfellevurdert)
  • 54.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Calder, Ian
    Institute of Hydrology, Wallingford.
    Harding, Richard
    Institute of Hydrology, Wallingford.
    Evaporation of intercepted snow: measurement and modelling1998Inngår i: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 206, nr 3-4, s. 151-163Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Snow storage on a coniferous forest canopy was measured using γ-ray attenuation and tree weighing systems, along with measurements of throughfall, using two plastic sheet net rainfall gauges. Meteorological parameters were measured with an automatic weather station. Estimates of evaporation of intercepted snow show an average rate of 0.24 mm h-1 and a maximum cumulative total of 3.9 mm in 7 h. Comparison with evaporation determined by a combination method with two different estimates of aerodynamic resistance (the "standard" rain aerodynamic resistance raL and a snow aerodynamic resistance raS-an order of magnitude larger than raL) showed that raL overestimated the evaporation by a factor of 2.6, whereas raS gave fair agreement with the measured evaporation. A multilayer model may be needed to take into account the variations of latent heat source area. Using the long-term measurements of the weight of snow on a single tree the total interception evaporation was estimated to be of the order 200 mm year-1.

  • 55.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Eriksson, Barbro
    Luleå tekniska universitet.
    Erixon, Peter
    Fell, Astrid
    Ingri, Johan
    Lundmark, Carina
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Samhällsvetenskap.
    Maurice, Christian
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Rönnbäck, Brit
    Teaching community in sustainable development: aim, realization and evaluation. Final report from project "Teaching communities" (självförbättrande lärartem)2006Rapport (Annet vitenskapelig)
    Abstract [en]

    A model for the educational development of university teachers (a type of teaching community) has been tested. University staff from different faculties worked and reflected together over the teaching and learning practice in a couple of courses. The community was supervised by an educational developer with a doctoral degree in psychology, and they worked in close collaboration with both undergraduate students and PhD students. The teaching staff that participated improved their teaching skills, extended their repertoire of learning tools, and experienced increased self-reliance. Their motivation and enthusiasm for teaching increased, and today they act as "missionaries" for good teaching and learning practices at the University. It was not obvious, however, that this educational development promoted their academic careers. New project ideas emerged from the teaching community.

  • 56.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Eriksson, M.
    Uppsala University, Institution for Earth Science, Deparment of Hydrology.
    Halldin, S.
    Uppsala University, Institution for Earth Science, Deparment of Hydrology.
    Kellner, E.
    Uppsala University, Institution for Earth Science, Deparment of Hydrology.
    Seibert, J.
    Uppsala University, Institution for Earth Science, Deparment of Hydrology.
    New approach to the measurement of interception evaporation1997Inngår i: Journal of Atmospheric and Oceanic Technology, ISSN 0739-0572, E-ISSN 1520-0426, Vol. 14, nr 5, s. 1023-1035Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Evaporation of water intercepted by vegetation represents an important (sometimes major) part of evapotranspiration in temperate regions. Interception evaporation is an important process where insufficient measurement techniques hamper progress in knowledge and modeling. An ideal technique to study the interception evaporation process should monitor intercepted mass (and its vertical distribution) and interception loss with high accuracy (0.1 mm) and time resolution (1 min), and give correct area estimates. The method should be inexpensive, require minor supervision during extended periods, and work in dense forests. Net precipitation techniques, in which interception evaporation is determined from the difference between gross precipitation (measured with funnels) and throughfall (measured with funnels, troughs, or plastic sheet net-rainfall gauges) fulfill many of the requirements but usually have a too-low accuracy and time resolution for process studies. Precipitation measurements are normally affected by distortion of the wind held around gauges as well as by adhesive and evaporative lasses. Throughfall measurements with precipitation funnels, troughs, or plastic sheet net-rainfall gauges, manually emptied or combined with tipping buckets, usually have too-low accuracy and time resolution for process studies and are impaired by adhesive losses. A new loadcell-based system to determine interception evaporation from gross and net precipitation is presented. A weighing gauge with minimal wind loss is used for precipitation, and weighing troughs are used for throughfall measurements. The weighing troughs minimize adhesive-loss errors and react instantaneously. Preliminary results with the method confirm that it can be used for process studies with a high accuracy (0.1 mm) and a high time resolution (1 min).

  • 57.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Erixon, Peter
    Widenfalk, Lennart
    Maurice, Christian
    Eriksson, Barbro
    Luleå tekniska universitet.
    Rönnbäck, Brit
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Pedagogik språk och Ämnesdidaktik.
    Promotion of collaborative learning in sustainable development: Arena Global Resources2006Inngår i: Proceedings 2005: utvecklingskonferensen 16-18 november i Karlstad / [ed] Ingrid Järnefelt, Luleå tekniska universitet, 2006Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In the Arena Global resources many exercises that designed to promote team-work and collaborative learning were introduced during the first semester. Examples of exercises were: a) adventure based experiential learning b) supervised peer review of written (process writing) and oral student presentations c) an exercise that revealed the disadvantages with lack of co-operation d) a home-work exercise where the students were encouraged to co-operate e) team-work dealing with water resources in an international perspective f) student panel discussion where knowledge from two different courses was integrated g) a tree-day study tour where the students learn to know each other. The students were also encouraged to read texts describing advantages with collaborative learning.

  • 58.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Feiccabrino, James
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Sea ice growth: modeling of precipitation phase2009Inngår i: Proceedings of the 20th International Conference on Port and Ocean Engineering under Arctic Conditions: June 9-12, 2009, Luleå, Sweden, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Snow insulates and changes ice albedo, therefore the precipitation phase identification scheme is important when modeling lake and sea ice growth. Precipitation phase separation schemes in coupled atmospheric-ice models are usually based on air temperatures but, snow fractions as a function of air temperature vary between models. Two examples of models which use 2-temperature thresholds, one for all rain and one for all snow with a linear decrease in snow fraction in-between, are the CAM-3 model used by National Centre for Atmospheric Research NCAR and the coupled Ocean Sea-Ice Model for Earth Simulators (OIFES). CAM-3 simulates 50% snow at 0°C while OIFES simulates 0% snow at the same temperature. Forty-five years of three-hour man-made precipitation phase observations for nineteen Swedish meteorological stations were used to compare different phase separation schemes. Observations of mixed precipitation were included (assumed to be half rain and half snow). A larger fraction (about 70%) of the precipitation was found to be snow at zero degrees as compared to the fractions simulated with the models mentioned above. This indicates that too large a fraction of the precipitation is classified as rain in these models. Consequently they underestimate the insulation of the snow as well as the albedo. For example, the reduction in (conduction driven) ice growth for a 0.5-m ice with 0.1-m low density (100 kg m-3) snow cover is about 90% compared to pure ice. Solar radiation absorption on the other hand is overestimated and this counterbalance might explain why the models perform fairly well with regard to ice growth even if the snow fraction is underestimated.

  • 59.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Feiccabrino, James
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Westerlund, Camilla
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Urban snow deposits versus snow cooling plants in northern Sweden: A quantitative analysis of snow melt pollutant releases2014Inngår i: Water quality research journal of Canada, ISSN 1201-3080, Vol. 49, nr 1, s. 32-42Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-velocity runoff from snow deposit transports suspended grain-attached contaminants while underground snow storages trapped these contaminants within the storage. The aim here is to quantify pollutant masses from an urban snow deposit and to investigate the conditions when pollutant control was increased by turning a snow deposit into a snow cooling plant with permeable underground snow storage. Pollutant masses in an urban snow deposit in northern Sweden were: Cu = 67, Pb = 17, Zn = 160, P = 170, SS = 620, 000, Cl = 1, 200, N = 380 kg. A theoretical analysis showed that the fraction of surface runoff from a surface deposit largely depends on the hydraulic conductivity (K, m s-1) of the soil. For a melt rate of 30 mm, day-1, surface runoff would be about 97% for a soil with K = 10-8, while nonexistent for K>10-6. Similar soil conductivities are needed to ensure that all snow melt could be transported as groundwater from an underground storage. The largest pollution-control advantage with underground snow storage compared to a surface deposit would thus be that piping and filters for operation of the plant could be used to filter surface snow melt runoff before rejection

  • 60.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Granlund, Nils
    Gustafsson, D.
    Kungliga tekniska högskolan, KTH.
    "Ground truth" snow measurements: review of operational and new ground-based snow measurement methods for Sweden, Norway and Finland2009Inngår i: 65th Eastern Snow Conference, 2009, s. 215-237Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Manual snow measurements are becoming increasingly expensive at the same time as climate change imposed snow alterations affects runoff and frost patterns; snow observations are included into runoff modelling, making reliable snow observations outmost important. New and modified ground-based techniques for monitoring snow depth, density, water equivalent (SWE), wetness and layering have the last decade been tested and this justifies a review of such methods. Techniques based on snow mass, electrical properties, attenuation of radioactivity and other miscellaneous properties are reviewed. The following sensors seem suitable for registration of temporal variations: Ultrasonic (depth), several snow pillows at the same location (SWE), CRREL/NRCS weighing sensor (SWE), Snowpower (depth, density, SWE and wetness), active and passive (cosmic) gamma-ray attenuation (SWE), and adjusted TDR-probes (density and wetness). Ground penetrating radar (GPR) is, depending on design and operation mode suitable for different purposes; when arrays of antennas are pulled by a snowmobile the technique is suitable for monitoring of spatial variations in depth, SWE, and density for dry snow. Techniques are under development which will improve the accuracy also for wet snow measurements. Frequency modulated continuous wave (FMCW) GPRs seem fit for measurement of snow layering. Some suggested techniques are not operational yet.

  • 61.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Granlund, Nils
    Gustafsson, David
    Division of Biogeophysics, The Royal Institute of Technology, KTH.
    Towards automated 'ground truth' snow measurements: a review of operational and new measurement methods for Sweden, Norway, and Finland2010Inngår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 24, nr 14, s. 1955-1970Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Manual snow measurements are becoming increasingly expensive and climate-change-imposed snow alterations are affecting run-off and frost patterns; snow observations are included in run-off modelling, making reliable snow observations of utmost importance. Multiple new and modified ground-based techniques for monitoring snow depth, density, snow water equivalent (SWE), wetness, and layering have been tested over the last decade, justifying a review of such methods. Techniques based on snow mass, electrical properties, attenuation of radioactivity, and other miscellaneous properties are reviewed. The following sensors seem suitable for registration of temporal variations: ultrasonic (depth) and terrestrial laser scanning (depth), several snow pillows at the same location (SWE), Cold Regions Research and Engineering Laboratory/Natural Resources Conservation Service weighing sensor (SWE), Snowpower (depth, density, SWE, and wetness), active and passive (cosmic) γ-ray attenuation (SWE), and adjusted time domain reflectometry probes (density and wetness). Ground-penetrating radar (GPR) is, depending on the design and operation modes, suitable for different purposes; when arrays of antennas are pulled by a snowmobile, the technique is suitable for monitoring of spatial variations in depth, density, and SWE for dry snow. Techniques are under development, which will hopefully improve the accuracy for wet snow measurements. Frequency-modulated continuous wave GPRs seem fit for measurement of snow layering. Some suggested techniques are not operational yet. Copyright

  • 62.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Gustafsson, David
    Research and Development, Swedish Meteorological and Hydrological Institute (SMHI).
    Stumpp, Christine
    Helmholtz Zentrum München, German Research Center for Environmental Health—Institute of Groundwater Ecology.
    Kløve, Bjørn
    Water Resources and Environmental Engineering. Research Group, University of Oulu.
    Feiccabrino, JAmes
    Department of Water Resources Engineering., Lund University.
    Spatiotemporal Variations in Snow and Soil Frost: A Review of Measurement Techniques2016Inngår i: Hydrology, ISSN 2306-5338, Vol. 3, nr 3, artikkel-id 28Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Large parts of the northern hemisphere are covered by snow and seasonal frost. Climate warming is affecting spatiotemporal variations of snow and frost, hence influencing snowmelt infiltration, aquifer recharge and river runoff patterns. Measurement difficulties have hampered progress in properly assessing how variations in snow and frost impact snowmelt infiltration. This has led to contradicting findings. Some studies indicate that groundwater recharge response is scale dependent. It is thus important to measure snow and soil frost properties with temporal and spatial scales appropriate to improve infiltration process knowledge. The main aim with this paper is therefore to review ground based methods to measure snow properties (depth, density, water equivalent, wetness, and layering) and soil frost properties (depth, water and ice content, permeability, and distance to groundwater) and to make recommendations for process studies aiming to improve knowledge regarding infiltration in regions with seasonal frost. Ground-based radar (GBR) comes in many different combinations and can, depending on design, be used to assess both spatial and temporal variations in snow and frost so combinations of GBR and tracer techniques can be recommended and new promising methods (auocostics and self potential) are evolving, but the study design must be adapted to the scales, the aims and the resources of the study. View Full-Text

  • 63.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Halldin, S.
    Uppsala University, Department of Hydrology.
    Evaporation of intercepted snow: analysis of governing factors1994Inngår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 30, nr 9, s. 2587-2598Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Insufficient understanding of winter hydrology conditions still hampers progress in predicting springtime discharge. The least known term in the winter water balance is evaporation, particularly of intercepted snow. Recent studies have shown that the evaporation from intercepted snow can be important. This paper elaborates factors governing evaporation of intercepted snow. Measurements with a cut tree-weighing device combined with a method to measure throughfall and drip gave a maximum evaporation rate of 0.3 +/- 0.06 mm/h or 3.3 +/- 0.06 mm/24 hours from a 6-m-high spruce. Calculations of evaporation with a combination equation and different ways to calculate the aerodynamic resistance and the evaporation from a snow-intercepted canopy during melt and sleet events showed that the most important factors for calculating the evaporation were the relative humidity, the aerodynamic resistance, the wind speed, and the intercepted mass. Less important factors were the energy to melt the intercepted snow, the method for calculating reduction in evaporation caused by a partly snow-covered canopy, accuracy in measurement of wind speed, air temperature, and net radiation.

  • 64.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Halldin, S.
    Snow interception evaporation: review of measurement techniques, processes and models1998Inngår i: XX Nordic Hydrological Conference: Helsinki, Finland 10-13 August 1998 / [ed] Juha Kajander, Helsinki: Nordic Association for Hydrology , 1998Konferansepaper (Fagfellevurdert)
  • 65.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Halldin, S.
    Institute of Earth Sciences/Hydrology, Uppsala University.
    Snow interception evaporation: review of measurement techniques, processes, and models2001Inngår i: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483, Vol. 70, nr 1-4, s. 117-133Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A global warming, primarily affecting wintertime conditions at high latitudes will influence the functioning of the boreal forest. The least known term of the winter water-balance equation is evaporation of snow intercepted in forest canopies. Several investigations stress the importance of snow-interception evaporation in coniferous forests and evaporation fractions of gross precipitation as large as 0.2-0.5 have been observed by investigators in Scotland, Canada, and Japan. Evaporation rates as high as 0.56 mm hm1 are reported. The largest differences between the rain and snow interception evaporation processes are the differences in storage. Snow storage (both mass and duration) is often an order of magnitude larger than that for rain. Snow interception changes the canopy albedo although some studies indicate the opposite. Process knowledge is limited because of measurement difficulties but it is known that canopy closure, aerodynamic resistance (ra), and vapour-pressure deficit are important factors. Existing formulations of ra as function of storage location and age cannot fully explain observed differences in evaporation rates. Operationalhydrology and weather models, and GCMs describe snow interception in a very simplified way and might benefit from incorporation of more realistic schemes.

  • 66.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Halldin, S.
    Institute of Earth Sciences/Hydrology, Uppsala University.
    Snow measurement techniques for land-surface-atmosphere exchange studies in boreal landscapes2001Inngår i: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483, Vol. 70, nr 1-4, s. 215-230Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Snow has been studied widely in hydrology for many decades whereas recent meteorological interest in snow is caused by increased emphasis on high latitudes and wintertime in climate-change research as well as by the need to improve weather-forecast models during these conditions. Ground-based measurements of snow properties are needed both to improve understanding of surface-atmosphere exchange processes and to provide ground truth to new remote-sensing algorithms. This justifies a review of techniques to measure snow in combination with establishment of criteria for the suitability of the methods for process studies. This review assesses the state-of-art in ground-based snow-measurement techniques in the end of the 1990s in view of their accuracy, time resolution, possibility to automate, practicality and suitability in different terrain. Methods for snow-pack water equivalent, depth, density, growth, quality, liquid-water content and water leaving the snow pack are reviewed. Synoptic snow measurements in Fennoscandian countries are widely varying and there is no single standard on which process-related studies can build. A long-term, continuous monitoring of mass and energy properties of a snow cover requires a combination of point-measurement techniques. Areally representative values of snow properties can be achieved through a combination of automatically collected point data with repeated manual, areally covering measurements, remote-sensing data and digital elevation models, preferably in a GIS framework.

  • 67.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Halldin, S.
    Snow measurements for land-surface-atmosphere exchange studies in boreal landscapes1998Inngår i: XX Nordic Hydrological Conference: Helsinki, Finland 10-13 August 1998 / [ed] Juha Kajander, Helsinki: Nordic Association for Hydrology , 1998, s. 681-Konferansepaper (Fagfellevurdert)
  • 68.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Johansson, R.-M.
    Luleå University of Technology.
    Optical precipitation gauge: determination of precipitation type and intensity by light attenuation technique1994Inngår i: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 25, nr 5, s. 359-370Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There exists a great need for automatic precipitation gauges for effective road maintenance during the winter period. These gauges should be inexpensive, not require mains supply, need little attendance, give information about presence of precipitation and determine type (snow, rain or sleet) while there is no need for high accuracy of the precipitation intensity. Light attenuation precipitation sensors (optical gauges) fulfil several of these requirements and are used in the Swedish National Road Administration Road Weather System. The optical gauges measure the time it takes of particles of snow etc. to pass (attenuate) a light beam and relate this time to precipitation type and intensity. The rain precipitation mass is approximately proportional to the accumulated attenuation time. To investigate whether or not optical gauges could also be used for solid precipitation, the precipitation mass for snow, rain and sleet was measured with a reference gauge and compared to the attenuation time. The passage time of individual hydrometeorologic particles (snow, rain and sleet) was compared with precipitation type and wind speed. Air temperature could be used as a rough guide a distinguish three precipitation categories for the following temperatures: rain (> +2-degrees-C), sleet (0 to +2-degrees-C) and snow (less-than-or-equal-to 0-degree-C). At low wind speeds (< 3 m/s) the passage time of individual particles could be used to distinguish between rain and snow. The accumulated attenuation time for the same precipitation mass was approximately 25 and 5 times greater for snow and sleet respectively compared to rain. With the attenuation time for the snow-fall corrected for wind influence the quotient between the attenuation time for snow and rain is decreased from approximately 25 to approximately 12 times.

  • 69.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Johansson, R.M.
    Precipitation intensity and type determined by ligth attenuation technique1994Inngår i: Proceedings / Polartech '94: International Conference on Development and Commercial Utilization of Technologies in Polar Regions, March 22-25, 1994 Luleå, Sweden, Luleå tekniska universitet, 1994, s. 209-220Konferansepaper (Fagfellevurdert)
  • 70.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Koivusalo, Harri
    Laboratory of Water Resources, Helsinki University of Technology.
    Estimating winter evaporation in boreal forests with operational snow course data2003Inngår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 17, nr 8, s. 1479-1493Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Snow course measurements from 11 sites located in eastern and northern Finland were used to estimate the total interception evaporation of a winter season for different forest categories. We categorized the sites based on forest density and tree species. Results showed that interception loss from gross precipitation increased with forest density and approached 30% for a forest with the highest density class. Interception loss for the most common forest density class was 11%. Interception losses were slightly larger in spruce forests than in pine, deciduous, or mixed forests. We provide suggestions as to how to design snow surveys to estimate wintertime interception evaporation better. Rough terrain and transition zones between forest and open areas should be avoided. Since evaporation fraction was strongly dependent on tree crown characteristics, snow course data should include direct estimates of canopy closure. Qualitative observations made by different observers should be given a reference frame to ensure comparability of records from different sites.

  • 71.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Koivusalu, H.
    Use of operational snow course measurements to approximate snow interception evaporation2000Inngår i: Nordic Hydrological Conference 2000: Uppsala, Sweden 26-30 June 2000 / [ed] Torbjörn Nilsson, Uppsala: Sveriges Lantbruksuniversitet, 2000, s. 570-577Konferansepaper (Fagfellevurdert)
  • 72.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Maurice, Christian
    Lundmark, Carina
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Samhällsvetenskap.
    Erixon, Peter
    Arena Global Resources: Experiences from the first Study Semester2003Inngår i: Proceedings 2003 Utvecklingskonferensen 26 - 28 november i Gävle / [ed] Ingrid Järnefelt, Rådet för högre utbildning , 2003, s. 20-40Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Luleå University of Technology is implementing a new type of open programs called Arenas. An Arena is more interdisciplinary than a traditional program and allows a wider entrance and a wider exit. Key words that characterise the arena concept are: Knowledge construction, research connection, collaboration with the surrounding society and individual choice. During the first semester in the Arena global resources the student learning during is focused on a) the development of essential academic skills required for successful studies such as improving personal responsibility and selfassessment skills b) basic knowledge about global resources (scientific, technical, economic, political and legal aspects) c) orientation about available courses, university research and professions within the field of global resources in order for the students to design an individual curriculum. Examples of activities are: a three-day study trip, team-work activities, process writing with student reflection on their learning process. Many teachers are involved in the work with the first study semester and one of the aims with this project is that these teachers should work with an action research approach to improve the student learning. Experiences from the first semester showed that we were successful in creating a good study atmosphere - students that had other first hand choices stayed at the arena, good study results (95% passed the exams). We were less successful with providing the information the students needed to design their individual curriculum.

  • 73.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Nakai, Yuichiro
    Hokkaido Research Centre, Forestry and Forest Products Research Institute, Sapporo.
    Thunehed, Hans
    Luleå tekniska universitet.
    Halldin, Sven
    Uppsala University.
    Snow accumulation in forests from ground and remote sensing data2004Inngår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 18, nr 10, s. 1941-1955Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Winter-forest processes affect global and local climates. The interception-sublimation fraction (F) of snowfall in forests is a substantial part of the winter water budget (up to 40%). Climate, weather-forecast and hydrological modellers incorporate increasingly realistic surface schemes into their models, and algorithms describing snow accumulation and snow-interception sublimation are now finding their way into these schemes. Spatially variable data for calibration and verification of wintertime dynamics therefore are needed for such modelling schemes. The value of F was determined from snow courses in open and forested areas in Hokkaido, Japan. The value of F was related to species and canopy-structure measures such as closure, sky-view fraction (SVF) and leaf-area index (LAI). Forest structure was deduced from fish-eye photographs. The value of F showed a strong linear correlation to structure: F = 0·44 - 0·6 × SVF for SVF < 0·72 and F = 0 for SVF > 0·72, and F = 0·11 LAI. These relationships seemed valid for evergreen conifers, larch trees, alder, birch and mixed deciduous stands. Forest snow accumulation (SF) could be estimated from snowfall in open fields (So) and to LAI according to SF = So (1 - 0·11 LAI) as well as from SVF according to SF = So (0·56 + 0·6 SVF) for SVF < 0·72. The value of SF was equal to So for SVF values above 0·72. The value of sky-view fraction was correlated to the normalized difference snow index (NDSI) using a Landsat-TM image for observation plots exceeding 1 ha. Variables F and SF were related to NDSI for these plots according to: F = -0·37NDSI + 0·29 and SF = So (0·81 + 0·37NDSI). These relationships are somewhat hypothetical because plot-size limitation only allowed one sparse-forest observation of NDSI to be used. There is, therefore, a need to confirm these relationships with further studies.

  • 74.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Richardson-Näslund, C.
    Stockholms Universitet.
    Andersson, C.
    Länsstyrelsen i Norrbotten.
    Snow density variations: consequences for ground-penetrating radar2006Inngår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 20, nr 7, s. 1483-1495Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reliable hydrological forecasts of snowmelt runoff are of major importance for many areas. Ground-penetrating radar (GPR) measurements are used to assess snowpack water equivalent for planning of hydropower production in northern Sweden. The travel time of the radar pulse through the snow cover is recorded and converted to snow water equivalent (SWE) using a constant snowpack mean density from the drainage basin studied. In this paper we improve the method to estimate SWE by introducing a depth-dependent snowpack density. We used 6 years measurements of peak snow depth and snowpack mean density at 11 locations in the Swedish mountains. The original method systematically overestimates the SWE at shallow depths (+25% for 0·5 m) and underestimates the SWE at large depths (-35% for 2·0 m). A large improvement was obtained by introducing a depth-density relation based on average conditions for several years, whereas refining this by using separate relations for individual years yielded a smaller improvement. The SWE estimates were substantially improved for thick snow covers, reducing the average error from 162 ± 23 mm to 53 ± 10 mm for depth range 1·2-2·0 m. Consequently, the introduction of a depth-dependent snow density yields substantial improvements of the accuracy in SWE values calculated from GPR data.

  • 75.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Thunehed, Hans
    Geovista AB.
    Impulse radar surveys - influence of liquid water: remote sensing and hydrology 20002001Inngår i: Remote Sensing and Hydrology 2000: Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000 / [ed] Manfred Owe; Kaye Brubaker; Jerry Ritchie; Albert Rango, Wallingford, Oxfordshire: IAHS Press, 2001, s. 136-138Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Snow water equivalent (SWE) of snow is of great importance for hydropower production in areas where a large proportion of the reservoir water comes from snow. Impulse radar to estimate the SWE is now in operational use in some Scandinavian basins. With radar technology the radar wave propagation time in the snow pack is converted into SWE with the help of a parameter usually termed the a value. Use of radar technology during late winter brings about risk for measurements of wet snow. The a value for dry snow cannot be used directly for wet snow. A liquid-water content of 5% (by volume) reduces the a value by » 20%.

  • 76.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Thunehed, Hans
    Geovista AB.
    Snow liquid water content influence on radar surveys2000Inngår i: Nordic Hydrological Conference 2000: Uppsala, Sweden 26-30 June 2000 / [ed] Torbjörn Nilsson, Uppsala: Sveriges Lantbruksuniversitet, 2000, s. 416-421Konferansepaper (Fagfellevurdert)
  • 77.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Thunehed, Hans
    Luleå tekniska universitet.
    Snow wetness influence on impulse radar snow surveys: theoretical and laboratory study2000Inngår i: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 31, nr 2, s. 89-106Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The snow-water equivalent of late-winter snowpack is of utmost importance for hydropower production in areas where a large proportion of the reservoir water emanates from snowmelt. Impulse radar can be used to estimate the snow-water equivalent of the snowpack and thus the expected snowmelt discharge. Impulse radar is now in operational use in some Scandinavian basins. With radar technology the radar wave propagation time in the snowpack is converted into snow-water equivalent with help of a parameter usually termed the a-value. Use of radar technology during late winter brings about risk for measurements on wet snow. The a-value for dry snow cannot be used directly for wet snow. We have found that a liquid-water content of 5% (by volume) reduces the a-value by approximately 20%. In this paper an equation, based on snow density and snow liquid water content, for calculation of wet-snow a-value is presented.

  • 78.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Thunehed, Hans
    Luleå tekniska universitet.
    Bergström, J
    Impulse radar snow surveys: influence of snow density2000Inngår i: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 31, nr 1, s. 1-14Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Snow cover water equivalent (SWE) is of major importance for planning of e.g. hydropower production in areas where a large proportion of the annual precipitation falls as snow. Radar technique can be used to determine SWE from the two-way travel time (twt) of a radar-wave propagation through a snowpack. SWE is usually related to twt through an empirical relationship, SWE = -b+a twt, where the values of a and b are determined by linear regression from simultaneous measurements of SWE (with snow-courses) and twt (with radar technology). In this paper a theoretical relationship between twt and SWE is developed showing the need for introducing the density when relating twt to SWE. Use of different empirical relationships for the real dielectric constant showed that the a-value for dry snow with a density of 350 kg m-3 (a typical value at the end of the accumulation season in the Nordic countries) is 0.040 m ns-1 (twt given in nanoseconds). When the snow density deviates considerably from this value a corrected a-value has to be used. A density of 300 and 400 kg m-3 gives a = 0.036 and 0.045 m ns-1 respectively. The b-value should theoretically be zero for measurements at the snow surface, non-zero values are probably due to the use of the direct wave between transmitter and receiver antennas as reference. The theoretically derived equations were confirmed by laboratory and field measurements as well as by measurements taken from literature.

  • 79.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Thunehed, Hans
    Geovista AB.
    Bergström, J.
    Radar snow surveys: influence of snow density1998Inngår i: XX Nordic Hydrological Conference: Helsinki, Finland 10-13 August 1998 / [ed] Juha Kajander, Helsinki: Nordic Association for Hydrology , 1998, s. 679-Konferansepaper (Fagfellevurdert)
  • 80.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Thunehed, Hans
    Geovista AB.
    Nakai, Y
    Canopy effect on net snow precipitation: estimates using LANDSAT-TM2002Inngår i: XXII Nordic Hydrological Conference: Nordic Association for Hydrology, Røros, Norway 4-7 August 2002 / [ed] Ånund Killingtveit, Trondheim: Norges teknisk-naturvitenskapelige universitet , 2002, s. 431-440Konferansepaper (Fagfellevurdert)
  • 81.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Vikström, Lars
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Assessment by project work in snow engineering2003Inngår i: European Journal of Engineering Education, ISSN 0304-3797, E-ISSN 1469-5898, Vol. 28, nr 1, s. 7-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Assessment in the form of a large project and field- and laboratory work was shown to be successful when applied to a course in snow engineering for university students with various backgrounds. The course was interdisciplinary, with teachers representing three different engineering disciplines. The project work was assessed by a report, a short oral presentation and an optional presentation such as a home page, a poster or a physical model. The students experienced that they had learned more with this assessment strategy than from courses with a final written exam. Peer evaluation of the relative contributions to the project work was applied and was appreciated by the students. The experiences of practical engineering tasks during the project work were also appreciated.

  • 82.
    Lundberg, Angela
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Öhlander, Björn
    The influence of different barrier constructions of tailings impoundments on infiltration rate and water balance: experimental studies from Kristineberg, Northern Sweden2005Inngår i: Ecological Restoration - a Global Challenge, Society for Ecological Restoration , 2005Konferansepaper (Fagfellevurdert)
  • 83.
    Lundin, Lars Christer
    et al.
    Department of Earth Sciences, Uppsala University.
    Halldin, S.
    Department of Earth Sciences, Uppsala University.
    Lindroth, A.
    SLU, Department of Production Ecology, Uppsala.
    Cienciala, E.
    SLU, Department of Soil Sciences, Uppsala.
    Grelle, A.
    SLU, Department of Production Ecology, Uppsala.
    Hjelm, P.
    Department of Earth Sciences, Uppsala University.
    Kellner, E.
    Department of Earth Sciences, Uppsala University.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Mölder, M.
    Department of Earth Sciences, Uppsala University.
    Morén, A.-S.
    SLU, Department of Production Ecology, Uppsala.
    Nord, T.
    Department of Earth Sciences, Uppsala University.
    Seibert, J.
    Department of Earth Sciences, Uppsala University.
    Stähli, M.
    SLU, Department of Soil Sciences, Uppsala.
    Continuous long-term measurements of soil-plant-atmosphere variables at a forest site1999Inngår i: Agricultural and Forest Meteorology, ISSN 0168-1923, E-ISSN 1873-2240, Vol. 98-99, nr 1-4, s. 53-73Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is a major challenge in modern 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-atmosphere-transfer (SVAT) system. Continuous, long-term data are needed in order to correctly quantify balances of water, energy and CO2 in this system and to correctly model it. It is the objective of this paper to demonstrate how a combined system of existing sensor, computer, and network technologies could be set up to provide continuous and reliable long-term SVAT-process data from a forested site under almost all environmental conditions. The Central Tower Site (CTS) system was set up in 1993-1994 in a 25 m high boreal forest growing on a highly heterogeneous till soil with a high content of stones and blocks. It has successfully monitored relevant states and fluxes in the system, such as atmospheric fluxes of momentum, heat, water vapour and CO2, atmospheric profiles of temperature, water vapour, CO2, short-and long-wave radiation, heat storage in soil and trees, sap-flow and a variety of ecophysiological properties, soil-water contents and tensions, and groundwater levels, rainfall and throughfall. System uptime has been more than 90% for most of its components during the first 5 years of operation. Results from the first 5 years of operation include e.g., budgets for energy, water and CO2, information on important but rarely occurring events such as evaporation from snow-covered canopies, and reactions of the forest to extreme drought. The carbon budget shows that the forest may be a sink of carbon although it is still growing. The completeness of the data has made it possible to test the internal consistency of SVAT models. The pioneering set-up at the CTS has been adopted by a large number of SVAT-monitoring sites around the world. Questions concerning tower maintenance, long-term calibration plans, maintenance of sensors and data-collection system, and continuous development of the computer network to keep it up to date are, however, only partly of interest as a research project in itself. It is thus difficult to get it funded from usual research-funding agencies. The full value of data generated by the CTS system can best be appreciated after a decade or more of continuous operation. Main uses of the data would be to evaluate how SVAT models handle the natural variability of climate conditions, quantification of water, carbon and energy budgets during various weather conditions, and development of new parameterisation schemes in global and regional climate models.

  • 84.
    Preda, Elena
    et al.
    University of Bucharest.
    Kløve, Bjorn
    Bioforsk, UOULU.
    Kværner, Jens
    Bioforsk.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Siergieiev, Dmytro
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Boukalova, Zuzana
    GIS.
    Postawa, Adam
    AGH.
    Witczak, Stanislaw
    AGH.
    Balderacchi, Matteo
    UCSC.
    Trevisan, Marco
    UCSC.
    Ertürk, Ali
    IGEM.
    Gonenc, Ethem
    IGEM.
    Rossi, Pekka
    University of Oulu.
    Muotka, Timo
    University of Oulu.
    Ilmonen, Jari
    University of Oulu.
    Stefanopoulos, Kyriakos
    Democritus University of Thrace.
    Vadineanu, Angheluta
    University of Bucharest.
    New indicators for assessing GDE vulnerability2013Rapport (Annet (populærvitenskap, debatt, mm))
  • 85. Selberg, Anders
    et al.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Mätning av vattenhalt för artificiell snö producerad från snökanon vid Vallåsens skidanläggning2006Rapport (Annet vitenskapelig)
    Abstract [sv]

    Den här rapporten har beställts av Vallåsens skidanläggning AB. Syftet har varit att utföra en oberoende undersökning av skillnader i vattenhalt i den snö som producerats av två av anläggningens snökanoner. De två kanonerna är av samma fabrikat och modell, Lenko FA4, men har köpts in vid olika tillfällen. Man har på skidanläggningen en tid misstänkt att de maskiner som köpts in vid det senare tillfället producerar blötare snö än vad som är önskvärt. Det är detta man velat få bekräftat. Vattenhalten har bestämts genom att mäta snöns dielektriska egenskaper (den dielektriska konstanten) och densitet och sedan utnyttja empiriskt bestämda samband mellan dessa tre. Mätningarna visar en signifikant skillnad i vattenhalt mellan de två kanonernas snö, under de förutsättningar som rådde under provtagningen. Den nyare kanonen tillverkar snö med en vattenhalt på i medeltal 11,2 volymsprocent, eller 25,6 viktprocent. För den äldre maskinen är motsvarande siffror 0,6 respektive 1,5 volymsprocent. Skillnaden har fastställts med en konfidensgrad på 0,99 både med avseende på volym och vikt.

  • 86. Semadeni-Davies, A.F.
    et al.
    Bengtsson, L.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Schilling, W.
    Urban thermal climate effects on stormwater in cold regions?2001Inngår i: Urban thermal climate effects on stormwater in cold regions?, Lippincott Williams & Wilkins, 2001, Vol. CD-ROM series No.2Konferansepaper (Fagfellevurdert)
  • 87.
    Semadeni-Davies, Annette
    et al.
    Department of Water Resources Engineering, Lund University.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bengtsson, Lars
    Department of Water Resources Engineering, Lund University.
    Radiation balance of urban snow: a water management perspective2001Inngår i: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 33, nr 1, s. 59-76Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The radiation balance of urbanised catchments differs from their rural counterparts, with snowpacks experiencing either enhanced or decreased irradiance depending on snowpack location and condition. As snowmelt is largely driven by radiation inputs, changes to localised irradiance (and melt rates) have implications for urban runoff generation. Storm- and wastewater drainage systems in cold regions are currently dimensioned for rain according to practices developed for temperate climates. They are not designed to cope with wintry conditions, which can lead to surface flooding, hydraulic overloads and poor water quality at receiving waters. Net allwave radiation measurements over snow made at the Swedish city of Luleå during April 1997 and 1998 are presented. The 1997 measurements were made in the vicinity of a matt-black-painted metal building at Luleå University of Technology, whereas the 1998 measurements are from a specially constructed 3×6-m black plastic-clad wall built on an open field just outside the town. Black minimises multiple reflections between the snow and walls, while maximising absorption of shortwave radiation by walls. The data were compared to the outputs of an urban radiation model. The results show that urban structures significantly alter radiation over snow. The temperature of the south-facing walls translates to longwave enhancements in the order of 150 W m−2 for several metres from the walls on sunny days. Shaded snow near the north-facing wall showed a net allwave radiation loss of the same order of magnitude. Radiation inputs to snow are similar both to the north and south of walls when the sky is overcast. The need to include snowmelt energetics within design and management techniques is discussed in light of the results.

  • 88.
    Siergieiev, Dmytro
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ehlert, L.
    Faculty of Science, Institute for Groundwater Management, Dresden.
    Reimann, Thomas
    Faculty of Science, Institute for Groundwater Management, Dresden.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Liedl, Rudolf
    Faculty of Science, Institute for Groundwater Management, Dresden.
    Modelling hyporheic processes for regulated rivers under transient hydrological and hydrogeological conditions2015Inngår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, nr 1, s. 329-340Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Understanding the effects of major hydrogeological controls on hyporheic exchange and bank storage is essential for river water management, groundwater abstraction, restoration and ecosystem sustainability. Analytical models cannot adequately represent complex settings with, for example, transient boundary conditions, varying geometry of surface water-groundwater interface, unsaturated and overland flow, etc. To understand the influence of parameters such as (1) sloping river banks, (2) varying hydraulic conductivity of the riverbed and (3) different river discharge wave scenarios on hyporheic exchange characteristics such as (a) bank storage, (b) return flows and (c) residence time, a 2-D hydrogeological conceptual model and, subsequently, an adequate numerical model were developed. The numerical model was calibrated against observations in the aquifer adjacent to the hydropower-regulated Lule River, northern Sweden, which has predominantly diurnal discharge fluctuations during summer and long-lasting discharge peaks during autumn and winter. Modelling results revealed that bank storage increased with river wave amplitude, wave duration and smaller slope of the river bank, while maximum exchange flux decreased with wave duration. When a homogeneous clogging layer covered the entire river-aquifer interface, hydraulic conductivity positively affected bank storage. The presence of a clogging layer with hydraulic conductivity < 0.001 m dg'1 significantly reduced the exchange flows and virtually eliminated bank storage. The bank storage return/fill time ratio was positively related to wave amplitude and the hydraulic conductivity of the interface and negatively to wave duration and bank slope. Discharge oscillations with short duration and small amplitude decreased bank storage and, therefore, the hyporheic exchange, which has implications for solute fluxes, redox conditions and the potential of riverbeds as fish-spawning locations. Based on these results, river regulation strategies can be improved by considering the effect of certain wave event configurations on hyporheic exchange to ensure harmonious hydrogeochemical functioning of the river-aquifer interfaces and related ecosystems.

  • 89.
    Siergieiev, Dmytro
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hydrogeochemical assessment of surface water - groundwater interaction: model development2011Konferansepaper (Fagfellevurdert)
  • 90.
    Siergieiev, Dmytro
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Surface water - groundwater interaction: hyporheic processes of a regulated river2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    During the last two decades large attention has been paid to the interface between rivers and groundwaters. Previous studies mainly focused on pristine streams with minimal human impact on the flow pattern (e.g (Triska et al., 1989). Nowadays, attention is drawn towards large regulated river systems that comprise 58% of the large world’s rivers (Nilsson et al., 2005). Therefore, research on hyporheic processes in such rivers is vital. Studies performed in large regulated rivers show an impact on hyporheic variables such as pressure, temperature, water chemistry and spatial extent of the hyporheic zone. The goal of this study is to extend the knowledge regarding geochemical processes in the hyporheic water by performing comprehensive analyses of hyporheic zone water chemistry of a large regulated boreal river.The hyporheic zone processes together with the river water were studied during a one year period in the regulated Lule River, Northern Sweden. Major features and variations were compared to the pristine settings of the neighboring Kalix River. A monitoring program included continuous measurements of water levels, electrical conductivity and water temperature, with occasional sampling of water chemistry that comprised filtered (<0.45 µm) concentrations of Ca, Na, Mg, K, Si, Fe, Mn, Al and organic carbon. The key difference in hydrological regime between regulated and pristine conditions was the absence of a spring peak, and overall reduced water discharge variations throughout the year in the regulated river. As a result, a fine-grained clogging layer forms on the regulated river bed, which restricts surface water-groundwater exchange. Presence of the clogging layer causes a longer residence time of the groundwater resulting in with higher filtered concentrations in the hyporheic zone. As a result of the short time regulation, frequent oxygenation of the subsurface by infiltration of the surface waters induced lower pH, higher DOC content, and increased filtered Fe, Mn, Si, K, Na, and Al concentrations. Enrichment of the hyporheic water in K and DOC occurs during water level fluctuations, when these elements are leached from the upper soil layer rich in decomposing organic matter.Changes in river stages due to river regulation also reach groundwater up to 50 m away from the river, thus initiating water table variations in the aquifer. It is hypothesized that in the studied area these water level variations induced a decrease in groundwater pH (up to one pH unit lower than the reference groundwater a few hundred meters uphill). Finally, possible acidification of soils and groundwater adjacent to the Lule River groundwater may in turn affect the riparian and riverine ecosystems negatively.

  • 91.
    Siergieiev, Dmytro
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Widerlund, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hyporheic water exchange in a large hydropower regulated boreal river: directions and rates2014Inngår i: Hydrology Research, ISSN 1998-9563, Vol. 45, nr 3, s. 334-348Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Widespread river regulation is known to modify river-aquifer interactions, influencing entire watersheds, but knowledge of the hyporheic flowpath along regulated rivers is limited. This study measured the hydraulic conductivity of the river bed and the aquifer, water levels and seepage fluxes in the heavily regulated Lule River in Northern Sweden, with the aim of characterising water exchange across the river-aquifer interface. While pristine rivers in the area are gaining, the Lule River was recharging the aquifer during 10% of the time. Daily river level fluctuations (typically ±0.25 m) directed ~3% of the total orthogonal flux across the river bed towards the aquifer, while during ~2% of the time the orthogonal fluxes were negligible (≤10–4 m d–1). A clogging layer on the river bed, most likely formed due to the modified river discharge, restricted river-aquifer exchange. The hyporheic zone had higher electrical conductivity than the river and the aquifer and electrical conductivity occasionally decreased following rising river water levels, with 3–5 hours delay. Overall, hydropower regulation has severely altered the hydrological regime of the hyporheic zone in the Lule River.

  • 92.
    Siergieiev, Dmytro
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Widerlund, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Öhlander, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    “Clogging layer” at regulated river beds - implications for river-groundwater exchange2013Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Within the EU-project GENESIS (2013), aiming to provide scientific basis and technical guidance for the update of the EU Groundwater Directive, Luleå University of Technology is investigating possible effects of hydropower regulation on surface water (SW)- groundwater (GW) exchange. The study compares SW, GW and hyporheic processes for the unregulated Kalix River and the regulated Lule River. Hydropower has long been regarded a fairly green energy source but today negative effects have become obvious (Renöfält et al. 2010).The hyporheic zone (HZ) accommodates most of the SW-GW exchange of solutes just beneath and along a river, dampens heat fluxes, processes pollutants and is essential for ecosystems.The study observes SW and GW (in wells orthogonal to the river) at one site in each river. In these, hydrological (water level, hydraulic conductivity, tracer test) and geochemical (temperature, electrical conductivity, water/soil chemistry) measurements were performed during several seasons.The presence of natural high-flow events in the Kalix River removes fines from the river bed, maintaining good SW-GW connectivity that favours hyporheic exchange (Brunke and Gonser 1997). Altered discharge of the regulated river (reduced flow peaks and velocity, daily discharge fluctuations) facilitated deposition of fine sediments at the river bed forming a “clogging layer” (Blaschke et al. 2003). The bed in the regulated river has two orders of magnitude lower hydraulic conductivity than that at the unregulated site and restricts the SW-GW exchange.Reduced hydraulic connectivity between SW and GW at the regulated Lule River site suggests decreased fluxes across the river-aquifer interface (Siergieiev et al. 2013), and thus reduced size of the HZ which is not always the case in regulated rivers (Sawyer et al. 2009).Decreased hyporheic velocities led to increased residence time and favored prolonged contact between water and soil matrix that stimulated biogeochemical transformations. As a result, the electrical conductivity of hyporheic water of the Lule River was higher than that of the surrounding water.Deteriorated connectivity and extended travel time reduced the dissolved oxygen concentration, which is functionally ecologically essential for hyporheic habitat. In addition, complete consumption of nitrate found at the regulated site, suggests formation of a suboxic zone extending several meters inland which promotes metals release reflected in high dissolved Fe and Mn in the HZ. The conditions of SW-GW exchange control nutrients processing and their export to SW. Thus, the HZ in the Lule River acts as a source of dissolved metals, while in the Kalix River much of the metals are removed by hyporheic processes due to good SW-GW connectivity.SW-GW connectivity plays an important role for hyporheic exchange and hyporheic water quality. Hydropower regulation in the Lule River has altered this connectivity, which may have far reaching implications for biogeochemical processes in the river.

  • 93.
    Siergieiev, Dmytro
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Widerlund, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Öhlander, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Wang, Zhiqing
    Hydropower regulation impact on river-groundwater interaction and the riparian zone: a geochemical approach2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Natural rivers, including their riparian zones, belong to the most diverse, dynamic, and complex ecosystems on the world’s continents, and they play key roles in the regulation and maintenance of biodiversity in the landscape (Dynesius and Nilsson, 1994). Hydropower has a major macro-economic impact since it supplies more than 50% of national electricity production in 65 countries (Koch, 2002). Today about two-thirds of the fresh water flowing to the oceans is obstructed by approximately 40,000 large dams and more than 900,000 smaller ones (Petts, 1984; McCully, 1996). Hydropower regulation of river bodies was for a long time considered to be an environmentally friendly source of energy (Renöfält et al., 2009). However, damming of rivers has later been recognized as one of the most dramatic anthropogenic impacts on the natural environment (Petts, 1984). A comparison between one regulated and one pristine river with similar features, both located in Northern Sweden, has been conducted (Collomp 2001). The Luleå River comprises 15 reservoirs and has been regulated for almost a century (72 % of the annual river runoff can be stored in its reservoirs) (Dynesius and Nilsson, 1994). The Kalix River, the last major unregulated river in Europe, is used as a reference for geochemical conditions in a pristine river.Water storage in reservoirs affects seasonal water discharge, water temperature, conductivity and concentrations of nutrients, dissolved oxygen, organic matter and metals. Spring peaks are truncated and postponed and average base flow is higher than that under pristine conditions. Due to increased sedimentation in the reservoirs, the transport of Fe, Si, Al, Mn, DOC, P and N has decreased (Drugge, 2003). The aim of the outlined study is to increase knowledge regarding the effect of river regulation on riparian groundwater geochemistry by:a) analysing river water measurements with respect to river-groundwater exchangeb) measuring riparian groundwater quality at one site in each of the two riversIn both rivers, sampling sites were chosen approximately 100 km upstream of the river mouth. The geological settings and climatic conditions are similar in the two chosen areas, with precipitation rates of about 400 mm/year. In the regulated Luleå River, frequent water level fluctuations cause continuous mixing of river water and groundwater. Land use in both areas is equally non-intensive, and hydropower exploitation of the Luleå River is the only notable difference in land use in the two areas. The monitoring program at each site includes installation of 2-3 groundwater wells, with data loggers continuously recording groundwater levels, temperature, pH, conductivity, DO and ORP. Water samples will be taken weekly or bi-weekly for metal and nutrient analyses, and the hydraulic conductivities at the sites will be determined in soil samples. Expected outcome: Improved knowledge regarding river regulation impact on riparian groundwater, based on comparison of a one-year cycle of seasonal variations in groundwater flow and quality in a heavily regulated and a nearby pristine river.

  • 94.
    Siergieiev, Dmytro
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Widerlund, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ingri, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Öhlander, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Flow regulation effects on the hydrogeochemistry of the hyporheic zone in boreal rivers2014Inngår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 499, s. 424-436Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    River-aquifer interfaces are essential for ecosystem functioning in terms of nutrient exchange and biological habitat, but are greatly threatened world-wide. This study examined geochemical aspects of river-aquifer interaction in one regulated and one unregulated boreal river in Northern Sweden to determine whether the geochemical functioning of the hyporheic zone is affected by hydrological alterations, e.g. regulated river discharge and river-aquifer connectivity. In the unregulated Kalix River, the hyporheic pore water was well-oxygenated with orthogonal fluxes (≈0.6-0.7 m d-1) and acted as a sink for Fe, Mn, Al, NH4, and Ca, with fractional losses of 95%, 92%, 45%, 31%, and 15%, respectively. A corresponding elevation in the concentrations of these elements in the hyporheic sediment was observed, with higher saturation indices of Fe-, Mn-, and Al-bearing secondary minerals in hyporheic waters. In the regulated Lule River, hydraulic connectivity at the river-aquifer interface was altered by the presence of a clogging layer (0.04 m d–1). In addition, the river discharge oscillated daily, severely reducing exchange flows across the riverbed (<0.01 m d-1). As a result, the hyporheic pore water was suboxic, with elevated concentrations of filtered Fe and Mn (fractional increase of ≈3700% and ≈2500%, respectively) and other solutes (NH4, Si, S, Ca). A conceptual model revealed functional differences between geochemical features of the hyporheic zone of regulated and unregulated rivers. Overall, the results showed that hyporheic processes are altered along regulated rivers, with resulting impacts on the geochemistry of riverine, riparian and related marine ecosystems.

  • 95.
    Siergieiev, Dmytro
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Widerlund, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Drugge, Lisbeth
    Collomp, Magali
    Ingri, Johan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Öhlander, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Impact of Hydropower Regulation on River Water Composition in Northern Sweden2014Inngår i: Aquatic geochemistry, ISSN 1380-6165, E-ISSN 1573-1421, Vol. 20, nr 1, s. 59-80Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using hydrogeochemical analysis of two large boreal rivers (pristine Kalix and hydropower regulated Lule) discharging into the Gulf of Bothnia, the major impacts of regulation on water discharge, element transport, and their seasonal redistribution have been assessed. The pre-regulation hydrogeochemical features were assumed to be similar for the two rivers. For the Lule River, the average maximum runoff was almost halved, while the average minimum was tripled as a result of the regulation. The fraction of winter transport of total organic carbon (TOC), Fe, Si, suspended Mn and P in the Lule River was, according to a conservative estimate, two to three times higher than in the pristine river. Longer residence time in the Lule River delayed arrival of the suspended Mn peak and dissolved Si decline to the river mouth. During summer, the suspended C/N ratio in the regulated river was 10-20 compared to <10 for the pristine, suggesting presence of predominantly old organic material. This was supported by a virtually constant suspended P/Fe ratio throughout the year in the Lule River, indicating low abundance of phytoplankton. TOC varied irregularly in the Lule River suggesting temporal disconnection between the river and the upper riparian zone. The disappearance of the spring flow maximum, a shift of element transport from spring to winter, and supply of mainly old organic material during the vegetation growth season may have a pronounced impact on the ecosystem of the Gulf of Bothnia and the river itself.

  • 96.
    Skogsberg, Kjell
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Wood chips as thermal insulation of snow2005Inngår i: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 43, nr 3, s. 207-218Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Snow (and ice) cooling is in some areas an alternative cooling technique to chillers. However, to utilise snow cooling during the summer, storage is needed. Snow storages were traditionally insulated by sawdust. A large demonstration plant has been in operation since 2000 for cooling the regional hospital in Sundsvall, Sweden. This storage is thermally insulated by larger wood chips. This paper summarizes laboratory testing of some key factors that influence the functioning of cutter shavings (another kind of wood chips) as thermal insulation. The melt rate significantly increased with increased wind velocity, light intensity (from spotlight bulbs), air temperature, and air humidity. A 1 cm thicker layer of cutter shavings decreased the melt rate about 0.097 kg m- 2 h- 1, within the studied layer limits of 2.5 to 7.5 cm. The melt rate with initially wet cutter shavings was about the same as for initially dry cutter shavings. This was explained by the increased evaporation which balanced increased thermal conductivity. Evaporation was found to be an important part of the energy balance and reduced the melt rate. Solar light reflectivity of new cutter shavings was measured in a separate outdoor experiment, found to be about 20%.

  • 97. Sundin, E.
    et al.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Semadeni-Davies, A.F.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Nordell, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Urban Snow Research at Luleå University of Technology2000Inngår i: Nordic Hydrological Conference 2000: Uppsala, Sweden 26-30 June 2000 / [ed] Torbjörn Nilsson, Uppsala: Sveriges Lantbruksuniversitet, 2000, s. 608-615Konferansepaper (Fagfellevurdert)
  • 98.
    Sundström, Nils
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Gustafsson, David
    KTH Royal Institute of Technology, Land and Water Resources Engineering.
    Kruglyak, Andrey
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Field evaluation of a new method for estimation of liquid water content and snow water equivalent of wet snowpacks with GPR2013Inngår i: Hydrology Research, ISSN 1998-9563, Vol. 44, nr 4, s. 600-613Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Estimates of snow water equivalent (SWE) with ground-penetrating radar can be used to calibrate and validate measurements of SWE over large areas conducted from satellites and aircrafts. However, such radar estimates typically suffer from low accuracy in wet snowpacks due to a built-in assumption of dry snow. To remedy the problem, we suggest determining liquid water content from path-dependent attenuation. We present the results of a field evaluation of this method which demonstrate that, in a wet snowpack between 0.9 and 3 m deep and with about 5 vol% of liquid water, liquid water content is underestimated by about 50% (on average). Nevertheless, the method decreases the mean error in SWE estimates to 16% compared to 34% when the presence of liquid water in snow is ignored and 31% when SWE is determined directly from two-way travel time and calibrated for manually measured snow density.

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