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  • 1.
    Ahlberg, Jesper
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Distributed snow modelling integrating ground penetrating radar data for improved runoff predictions in a Swedish mountain basin2009Ingår i: EGU General Assembly 2009, 2009Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Operational forecasts of snow melt runoff in Sweden are currently running with precipitation and temperature as the main input variables and calibrated with runoff data, and there is an interest to make better use of new measurement systems for distributed snow data. At the same time, various data assimilation techniques are becoming more frequently used in hydrological modeling, in order to reduce uncertainties related to both model structure errors and errors in input and calibration data. Thus, it is important to address not only what type of snow data that can be used to improve the model predictions, but also what type of input data and model structures that are optimal in relation to the available snow data. The objective of this study is to investigate to what extent the runoff predictions can be improved by assimilation of temporal and spatially distributed snow data, and if the improvements depend on the choice of model structures, for instance the use of energy balance or day-degree snow models. In order to achieve these objectives a new distributed snow model has been implemented into the hydrological modeling framework HYSS/HYPE. This model can easily be setup with either an energy balance model or a day-degree model for the snow pack calculations, and it is easy to run the model with different spatial resolutions. In the fully distributed case, snow drift processes are implicitly included in the model through a precipitation distribution model, based on topographical information and wind direction. The model was applied to a mountain basin in northern Sweden used for hydropower production, where extensive snow measurements were taken during the last two winters 2007-2009. A climate station is located at the outlet of the regulation lake, including automated point measurements of snow depth, snow mass (snow pillow), snow wetness and snow temperature. Distributed snow cover data was sampled using ground-penetrating radar from snow mobiles. Measurements were taken at the time of the maximum snow cover, providing a data set with snow depth, snow density, snow water equivalent along 20 km long transects in representative areas of the basin. The precipitation distribution model was calibrated using the distributed SWE data from the GPR measurements. Application of the calibrated model to previous years without available snow data show that the runoff predictions was improved compared to calibrations without the distributed snow data, however the improvements were larger for the energy balance compared to the day-degree model. Further developments will include assimilation of the temporal and spatial snow data to adjust the distribution of various input variables, for instance air temperature and wind speed.

  • 2.
    Ahlberg, Jesper
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Snow melt runoff simulations using ensemble Kalman filter assimilation of distributed snow data2010Konferensbidrag (Övrigt vetenskapligt)
  • 3. Bormann, H.
    et al.
    Holländer, H. M.
    Blume, T.
    Buytaert, W.
    Chirico, G. B.
    Exbrayat, J. -F
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630).
    Hölzel, H.
    Kraft, P.
    Krauße, T.
    Nazemi, A.
    Stamm, C.
    Stoll, S.
    Blöschl, G.
    Flühler, H.
    Comparative discharge prediction from a small artificial catchment without model calibration: Representation of initial hydrological catchment development2011Ingår i: Die Bodenkultur, ISSN 0006-5471, Vol. 62, nr 1-4, s. 23-29Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ten conceptually different models were applied to predict the discharge from the 6 ha artificial Chicken Creek catchment in Lausatia, North-East Germany, which has been created in an open cast mining area. The study consisted of three steps to make a model intercomparison with the objective of a priori prediction of the water balance and the discharge dynamics. In order to test the ability of each model and modeller to predict water flows in an ungauged catchment, only soil texture, topography, vegetation coverage and climate data were provided to the modellers in the first step. Hydrological data on discharge, soil moisture and groundwater levels were withheld. This enabled us to assess the predictive capabilities of the models under sparse data conditions. The predicted components of the water balance varied in a wide range. None of the model simulations came close to the observed water balance for the entire 3-year study period. Discharge was mainly predicted as subsurface flow with little surface runoff. In reality, surface runoff was a major flow component despite the fairly coarse soil texture. In the second step, additional process knowledge was gained during a joint field visit. The occurence of gully erosion and surface crusting was detected and implemented into the models. Consequently, model predictions changed considerably. The previous simulations dominated by subsurface flow changed to surface flow-dominated simulations. Additional data, provided in the third step, mainly confirmed the parameterisations and assisted in a better definition of initial conditions and subsurface storage. The comparison indicates that, in addition to model philosophy, the personal judgement of the modellers was a major source of the differences in the model results. The model parameterisation and choice of initial conditions depended on the modeller's judgement and were therefore a result of the modellers' experience in terms of model types and case studies.

  • 4. Essery, Richard
    et al.
    Rutter, Nick
    Pomeroy, John
    Baxter, Robert
    Stahli, Manfred
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Barr, Alan
    Bartlett, Paul
    Elder, Kelly
    An Evaluation of Forest Snow Process Simulations2009Ingår i: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 90, nr 8, s. 1120-+Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Northern Hemisphere has large areas that are forested and seasonally snow covered. Compared with open areas, forest canopies strongly influence interactions between the atmosphere and snow on the ground by sheltering the snow from wind and solar radiation and by intercepting falling snow; these influences have important consequences for the meteorology, hydrology, and ecology of forests. Many of the land surface models used in meteorological and hydrological forecasting now include representations of canopy snow processes, but these have not been widely tested in comparison with observations. Phase 2 of the Snow Model Intercomparison Project (SnowMIP2) was therefore designed as an intercomparison of surface mass and energy balance simulations for snow in forested areas. Model forcing and calibration data for sites with paired forested and open plots were supplied to modeling groups. Participants in 11 countries contributed output from 33 models, and the results are published here for sites in Canada, the United States, and Switzerland. On average, the models perform fairly well in simulating snow accumulation and ablation, although there is a wide intermodal spread and a tendency to underestimate differences in snow mass between open and forested areas. Most models capture the large differences in surface albedos and temperatures between forest canopies and open snow well. There is, however, a strong tendency for models to underestimate soil temperature under snow, particularly for forest sites, and this would have large consequences for simulations of runoff and biological processes in the soil.

  • 5. Feiccabrino, James
    et al.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Lundberg, Angela
    Surface-based precipitation phase determination methods in hydrological models2013Ingår i: Hydrology Research, ISSN 1998-9563, Vol. 44, nr 1, s. 44-57Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We compared solid and liquid precipitation mass output from three categories of common model precipitation phase determination schemes (PPDS) to the recorded precipitation phase in a set of 45 years of 3-hour manual meteorological observations from 19 Swedish meteorological stations. In the first category of rain/snow thresholds, it was found that rain/snow air temperature threshold (ATT) is a better precipitation phase indicator than a rain/snow dew point temperature threshold. When a rain/snow ATT of 0.0 degrees C (a default value used in some recent models) was replaced by 1.0 degrees C, misclassified precipitation was reduced by almost one half. A second category of PPDS use two ATTs, one snow and one rain, with a linear decrease in snow fraction between. This category identified precipitation phase better than a rain/snow ATT at 17 stations. Using all observations from all the meteorological stations, a final category using an air-temperature-dependent snow probability curve resulted in slightly lower misclassified precipitation mass at 13 of the 19 stations. However, schemes from the linear decrease in snow fraction category had the lowest misclassified precipitation mass at four meteorological stations.

  • 6. Feiccabrino, James
    et al.
    Lundberg, Angela
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Improving surface-based precipitation phase determination through air mass boundary identification2012Ingår i: Hydrology Research, ISSN 1998-9563, Vol. 43, nr 3, s. 179-191Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most hydrological models apply one empirical formula based on surface air temperature for precipitation phase determination. This approach is flawed as surface precipitation phase results from energy exchanges between falling precipitation and air in the lower atmosphere. Different lower atmospheric conditions cause different precipitation phase probabilities for near-freezing temperatures. Often directly measured lower atmospheric conditions are not available for remote areas. However, meteorological observations occurring before/after similar air mass boundaries have similar atmospheric conditions that vary from most other observations. Therefore, hydrological models can indirectly account for lower atmospheric conditions. Twenty years of manual observations from eight United States weather stations were used to compare misclassified precipitation proportions when analyzing (a) all precipitation observations together and (b) identified cold air mass boundary observations (CAB) and non-CAB observations separately. The CAB observations were identified by a rapid surface air temperature decrease. A two-surface air temperature threshold method with one threshold all snow (T-S degrees C) and one all rain (T-R degrees C) having a linear snow fraction decrease between the thresholds was used. The T-S (0 degrees C), and T-R (4 degrees C) values for CAB were 1 degrees C warmer than for non-CAB (-1 degrees C, 3 degrees C). Analyzing CAB and non-CAB separately reduced misclassified precipitation 23%, from 7.0 to 5.4%.

  • 7. Gouttevin, I.
    et al.
    Lehning, M.
    Jonas, T.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Mölder, M.
    A two-layer canopy model with thermal inertia for an improved snowpack energy balance below needleleaf forest (model SNOWPACK, version 3.2.1, revision 741)2015Ingår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 8, nr 8, s. 2379-2398Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new, two-layer canopy module with thermal inertia as part of the detailed snow model SNOWPACK (version 3.2.1) is presented and evaluated. As a by-product of these new developments, an exhaustive description of the canopy module of the SNOWPACK model is provided, thereby filling a gap in the existing literature. In its current form, the two-layer canopy module is suited for evergreen needleleaf forest, with or without snow cover. It is designed to reproduce the difference in thermal response between leafy and woody canopy elements, and their impact on the underlying snowpack or ground surface energy balance. Given the number of processes resolved, the SNOWPACK model with its enhanced canopy module constitutes a sophisticated physics-based modeling chain of the continuum going from atmosphere to soil through the canopy and snow. Comparisons of modeled sub-canopy thermal radiation to stand-scale observations at an Alpine site (Alptal, Switzerland) demonstrate improvements induced by the new canopy module. Both thermal heat mass and the two-layer canopy formulation contribute to reduce the daily amplitude of the modeled canopy temperature signal, in agreement with observations. Particularly striking is the attenuation of the nighttime drop in canopy temperature, which was a key model bias. We specifically show that a single-layered canopy model is unable to produce this limited temperature drop correctly. The impact of the new parameterizations on the modeled dynamics of the sub-canopy snowpack is analyzed. The new canopy module yields consistent results but the frequent occurrence of mixed-precipitation events at Alptal prevents a conclusive assessment of model performance against snow data. The new model is also successfully tested without specific tuning against measured tree temperature and biomass heatstorage fluxes at the boreal site of Norunda (Sweden). This provides an independent assessment of its physical consistency and stresses the robustness and transferability of the chosen parameterizations. The SNOWPACK code including the new canopy module, is available under Gnu General Public License (GPL) license and upon creation of an account at https://models.slf.ch/.

  • 8.
    Granlund, Nils
    et al.
    Luleå University of Technology.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Lundberg, Angela
    Luleå University of Technology.
    Snow Salinity Influence on the Relationship between Electrical: Conductivity of Snow and Snow Wetness2009Ingår i: 65th Annual Eastern Snow Conference, 2009Konferensbidrag (Övrigt vetenskapligt)
  • 9. Granlund, Nils
    et al.
    Lundberg, Angela
    Feiccabrino, James
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Miljögeokemi och ekoteknik.
    Laboratory test of snow wetness influence on electrical conductivity measured with ground penetrating radar2009Ingår i: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 40, nr 1, s. 33-44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ground penetrating radar operated from helicopters or snowmobiles is used to determine snow water equivalent (SWE) for annual snowpacks from radar wave two-way travel time. However, presence of liquid water in a snowpack is known to decrease the radar wave velocity, which for a typical snowpack with 5% (by volume) liquid water can lead to an overestimation of SWE by about 20%. It would therefore be beneficial if radar measurements could also be used to determine snow wetness. Our approach is to use radar wave attenuation in the snowpack, which depends on electrical properties of snow (permittivity and conductivity) which in turn depend on snow wetness. The relationship between radar wave attenuation and these electrical properties can be derived theoretically, while the relationship between electrical permittivity and snow wetness follows a known empirical formula, which also includes snow density. Snow wetness can therefore be determined from radar wave attenuation if the relationship between electrical conductivity and snow wetness is also known. In a laboratory test, three sets of measurements were made on initially dry 1m thick snowpacks. Snow wetness was controlled by stepwise addition of water between radar measurements, and a linear relationship between electrical conductivity and snow wetness was established.

  • 10. Granlund, Nils
    et al.
    Lundberg, Angela
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630).
    Laboratory study of the influence of salinity on the relationship between electrical conductivity and wetness of snow2010Ingår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 24, nr 14, s. 1981-1984Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Snow water equivalent of a snowpack can be estimated using ground-penetrating radar from the radar wave two-way travel time. However, such estimates often have low accuracy when the snowpack contains liquid water. If snow wetness is known, it is possible to take it into account in the estimates; it is therefore desirable to be able to determine snow wetness from already available radar data. Our approach is based on using radar wave attenuation, and it requires that the relationship between electrical conductivity and wetness of snow should be known. This relationship has been tentatively established in previous laboratory experiments, but only for a specific liquid water salinity and radar frequency. This article presents the results of new laboratory experiments conducted to investigate if and how this relationship is influenced by salinity. In each experiment, a certain amount of snow was melted and a known amount of salt (different for different experiments) was added to the water. Water salinity was measured, and the water was added step-wise to a one-meter thick snowpack, with radar measurements taken between additions of water. Our experiments have confirmed the earlier established linear relationship between electrical conductivity and wetness of snow, and they allow us to suggest that the influence of liquid water salinity on electrical conductivity is negligible when compared to the influence of liquid water content in snow.

  • 11.
    Granlund, Nils
    et al.
    Luleå University of Technology.
    Lundberg, Angela
    Luleå University of Technology.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Ahlberg, Jesper
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Wetterhall, Fredrik
    Sveriges Meteorologiska och Hydrologiska Institut.
    Towards better predictions of snow melt runoffs: Measuring Snow Depth and Density Using Ground Penetrating Radar2009Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Snow melt runoff predictions by hydrological models are essential for efficient hydropower production in the Scandinavian countries, similar to many areas with a substantial amount of snow precipitation. Operational models in Sweden are currently based on precipitation and temperature as the main input variables and calibrated with runoff data, but there is an interest to make better use of new measurement systems for distributed snow data, especially the total amount of snow in the catchment area of interest. The main objective of our project is to investigate the potential improvements in runoff predictions in relation to the choice of model structure and measurement systems, as well as measurement accuracy. This involves comparing different methods for estimating the total amount of snow in a catchment area as well as improving their accuracy. Here we present the result of such comparison based on data from case studies conducted in Sweden. Our approach involves automated single point measurements over a long period in combination with high resolution distributed measurements over a large area during critical periods. Stationary measurements are performed at a snow measurement station, with snow density and wetness estimated with a low-frequency impedance sensor band, snow depth measured using an ultrasonic depth gauge, and temperature measured at several (fixed) snow depths and at the snow surface. The station, located at Lake Korsvattnet in Swedish mountains, operates continuously during the whole winter season. Measurements of snow depth and density over large lateral distances are performed using multi-offset ground penetrating radar (GPR) operated from a snow mobile. These measurements are conducted once a year, in late winter, when the amount of snow is expected to reach its maximum before snow melt begins. Since 2007 and during the duration of the project, yearly measurements have been and will be taken in two Swedish mountain basins important for hydropower, Lake Korsvattnet and Lake Kultsjön. The radar system used is a multi-channel RAMAC/GPR system with shielded 800 and 1600 MHz antennas. The antennas are attached to a snow mobile sledge forming an array, which allows us to use the common midpoint method to calculate both radar propagation velocity and two-way travel time of radar pulses. For dry snow this gives snow density and depth via an empirical formula establishing the relationship between electrical permittivity (i.e. propagation velocity) and snow density. Note that for wet snow additional information about liquid water content in snow is required, which can be estimated, for example, from radar wave attenuation. However, for the purpose of this presentation we assume that the snow is dry. The results of GPR measurements taken from a snow mobile are compared with results obtained by two other methods. The first comparison is with manual measurements taken with traditional snow tubes along a 1000 m measurement profile at the area of Lake Korsvattnet. In this case a log-linear relationship between snow depth and density is used to interpret GPR data (note that this relationship is obtained from analysis of radar data itself). The other comparison is with GPR measurements taken from a helicopter along a 12 km transect in the area of Lake Kultsjön.

  • 12.
    Gustafsson, David
    KTH, Tidigare Institutioner                               , Mark- och vattenteknik.
    Boreal land surface water and heat balance: Modelling soil-snow-vegetation-atmosphere behaviour2002Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The water and heat exchange in thesoil-snow-vegetation-atmosphere system was studied in order toimprove the quantitative knowledge of land surface processes.In this study, numerical simulation models and availabledatasets representing arable land, sub-alpine snowpack, andboreal forest were evaluated at both diurnal and seasonaltimescales.

    Surface heat fluxes, snow depth, soil temperatures andmeteorological conditions were measured at an agriculturalfield in central Sweden during three winters and two summersfrom 1997 to 2000 within the WINTEX project. A one-dimensionalsimulation model (COUP) was used to simulate the water and heatbalance of the field. Comparison of simulated and measured heatfluxes in winter showed that parameter values governing theupper boundary condition were more important for explainingmeasured fluxes than the formulation of the internal mass andheat balance of the snow cover. The assumption of steady stateheat exchange between the surface and the reference height wasinadequate during stable atmospheric conditions. Independentestimates of the soil heat and water balance together with thecomparison of simulated and measured surface heat fluxes showedthat the eddy-correlation estimates of latent heat fluxes fromthe arable field were on average 40 % too low.

    The ability of a multi-layered snowpack model (SNTHERM) tosimulate the layered nature of a sub-alpine snowpack wasevaluated based on a dataset from Switzerland. The modelsimulated the seasonal development of snow depth and densitywith high accuracy. However, the models ability to reproducethe strong observed snowpack layering was limited by theneglection of the effect of snow microstructure on snowsettling, and a poor representation of water redistributionwithin the snowpack.

    The representation of boreal forest in the land surfacescheme used within a weather forecast (ECMWF) model was testedwith a three-year dataset from the NOPEX forest site in centralSweden. The new formulation with separate energy balances forvegetation and the soil/snow beneath the tree cover improvedthe simulation of seasonal and diurnal variations in latent andsensible heat flux. Further improvements of simulated latentheat fluxes were obtained when seasonal variation in vegetationproperties was introduced. Application of the COUP model withthe same dataset showed that simulation of evaporation fromintercepted snow contributed to a better agreement with themeasured sensible heat flux above forests, but also indicatedthat the measurements might have underestimated latent heatflux. The winter sensible heat flux above the forest wasfurther improved if an upper limit of the aerodynamicresistance of 500 s m-1 was applied for stable conditions.

    A comparison of the water and heat balance of arable landand forest confirmed the general knowledge of the differencesbetween these two surface types. The forest contributed withconsiderably more sensible heat flux to the atmosphere than thearable land in spring and summer due to the lower albedo andrelatively less latent heat flux. Latent heat flux from theforest was higher in winter due to the evaporation ofintercepted snow and rain. The net radiation absorbed by theforest was 60 % higher than that absorbed by the arable land,due to the lower surface albedo in winter.

    Key words:soil; snow; land surface heat exchange;forest; arable land; eddy-correlation.

  • 13.
    Gustafsson, David
    KTH, Tidigare Institutioner                               , Mark- och vattenteknik.
    Land surface heat exchange over snow and frozen soil2001Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The energy exchange in the soil-snow-vegetation-atmospheresystem was studied to improve the quantitative knowledge of thegoverning processes. The lack of such knowledge contributes tothe uncertainty in the applicability of many existing modelsindependent of the temporal or spatial scale. The theoreticalbackground and available methods for measurements and numericalsimulations were reviewed. Numerical simulation models andavailable data sets representing open land and boreal forestwere evaluated in both diurnal and seasonal time-scales.Surface heat fluxes, snow depth, soil temperatures andmeteorological conditions were measured at an agriculturalfield in central Sweden over two winters, 1997-1999. Twoone-dimensional simulation models of different complexity wereused to simulate the heat and water transfer in thesoil-snow-atmosphere system and compared with the measurements.Comparison of simulated and observed heat fluxes showed thatparameter values governing the upper boundary condition weremore important than the formulation of the internal mass andheat balance of the snow cover. The models were useful toevaluate the lack of energy balance closure in the observedsurface heat fluxes, which underlined the importance ofimproved accuracy in eddy correlation measurements of latentflow during winter conditions.

    The representation of boreal forest in the land surfacescheme used within a weather forecast model was tested with athree-year data set from the NOPEX forest site in centralSweden. The formulation with separate energy balances forvegetation and the soil/snow beneath tree cover improvedsimulation of the seasonal and diurnal variations of latent andsensible heat flux compared with an older model version.Further improvements of simulated surface heat fluxes could beexpected if the variation of vegetation properties within andbetween years and a new formulation of the boundary conditionsfor heat flux into the soil is included.

    Keywords: Surface energy balance, Snow, Boreal forest,SVAT models, Eddy-correlation Measurements, Latent heat flux,Sensible heat flux, Net radiation, Soil temperature,Aerodynamic roughness, Surface resistance

  • 14.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Measurements of snow water equivalent using multiple-offset ground-penetrating radar2006Ingår i: , 2006Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Ground-penetrating radar (GPR) measurements of snow water equivalent depend onaccurate information of the radar wave propagation velocity in the snow cover, aswell as on the relationship between the dielectric constant and snow density. This paperevaluates a simplified procedure to derive snow water equivalent from GPR traveltime data only, using multiple-offset GPR antennas arranged in an array. The dielectricconstant and the depth of the snow cover are determined by multi-channel measurementsusing several combinations of transmitter and receiver antennas in the array,based on basic common-mid-point principles. This set-up enables continuous determinationof both snow cover depth and snow density along the measurement profile,which reduces the uncertainties due to spatial variation of snow density. The measurementsystem is evaluated using manual snow depth and snow density measurements attwo sites in northern Sweden during winter 2004/2005. Results show that the spatialvariation of both snow depth and snow density were improved with the multi-offsetmeasurements compared to the use of a single channel measurement.

  • 15.
    Gustafsson, David
    KTH, Tidigare Institutioner                               , Mark- och vattenteknik.
    Surface heat and water balance of a boreal arable field: long-term measurements and simulationsManuskript (preprint) (Övrigt vetenskapligt)
  • 16.
    Gustafsson, David
    KTH, Tidigare Institutioner                               , Mark- och vattenteknik.
    The energy exchange at the land surface during winter: existing theories and their limitationsManuskript (preprint) (Övrigt vetenskapligt)
  • 17.
    Gustafsson, David
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Ahlberg, Jesper
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Granlund, Nils
    Luleå University of Technology.
    Lindström, Göran
    Sveriges meteorologiska och hydrologiska institut.
    Wetterhall, Fredrik
    Sveriges meteorologiska och hydrologiska institut.
    Lundberg, Angela
    Luleå University of Technology.
    Distribuerade system för förbättrade snö- och avrinningsprognoser. Integration i hydrologiska modeller: Delrapport 12009Rapport (Övrigt vetenskapligt)
  • 18.
    Gustafsson, David
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Granlund, Nils
    Luleå University of Technology.
    Lundberg, Angela
    Luleå University of Technology.
    Multi-offset impulse radar for snow water equivalent measurements2008Ingår i: Proceedings of the 65th Annual Meeting of Eastern Snow Conference, 2008Konferensbidrag (Övrigt vetenskapligt)
  • 19.
    Gustafsson, David
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Gärdenäs, Annemieke
    Department of Soil and Environment, Swedish University of Agricultural Sciences.
    Eckersten, Henrik
    Department of Ecology and Crop Production, Swedish University of Agricultural Sciences.
    Simulated carbon and water processes of forest ecosystems in Forsmark and Oskarshamn during a 100-year period2006Rapport (Övrigt vetenskapligt)
  • 20.
    Gustafsson, David
    et al.
    KTH, Tidigare Institutioner                               , Mark- och vattenteknik.
    Jansson, Per-Erik
    Lewan, E
    Water and heat balance of the boreal landscape: comparison of forest and arable land.Manuskript (preprint) (Övrigt vetenskapligt)
  • 21.
    Gustafsson, David
    et al.
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Lewan, E.
    Jansson, Per-Erik
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Modeling water and heat balance of the boreal landscape - comparison of forest and arable land in Scandinavia2004Ingår i: Journal of applied meteorology (1988), ISSN 0894-8763, E-ISSN 1520-0450, Vol. 43, nr 11, s. 1750-1767Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The water and heat balances of an arable field and a forest in the boreal zone in Scandinavia were explored using 3 yr of observations and simulations with two different soil - vegetation - atmosphere transfer (SVAT) models over a 30-yr period. Results from a detailed mechanistic model [ coupled heat and mass transfer model ( COUP)] were compared with those obtained with a large-scale type of SVAT model used in the weather prediction model at the European Centre for Medium-Range Weather Forecasts [ECMWF tiled land surface scheme (TESSEL)]. The COUP model simulations agreed well with the observations from a seasonal perspective. The TESSEL model differed significantly from the measurements when standard operational parameter values were used. The introduction of a seasonal variation in leaf-area index values, tuned canopy resistance for forest, and a reduced roughness length over snow-covered open land reduced the discrepancies. Net radiation was 40% higher in the forest when compared with the arable land, based on 30-yr simulations with both models. Furthermore, the forest was a net source of sensible heat flux, whereas the arable land was a net sink. Because of different treatment of winter interception evaporation, forest latent heat flux based on the COUP model considerably exceeded that from the TESSEL model, and suggested that the total annual evaporation was higher from the forest than from arable land. The representation of interception evaporation in winter, as well as seasonal dynamics in vegetation properties are, thus, of considerable importance for adequate simulation of forest and arable land energy fluxes within the boreal zone.

  • 22.
    Gustafsson, David
    et al.
    KTH, Tidigare Institutioner                               , Mark- och vattenteknik.
    Lewan, E.
    van den Hurk, Bjjm
    Viterbo, P.
    Grelle, A.
    Lindroth, A.
    Cienciala, E.
    Molder, M.
    Halldin, S.
    Lundin, L. C.
    Boreal forest surface parameterization in the ECMWF model - 1D test with NOPEX long-term data2003Ingår i: Journal of applied meteorology (1988), ISSN 0894-8763, E-ISSN 1520-0450, Vol. 42, nr 1, s. 95-112Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 23.
    Gustafsson, David
    et al.
    KTH, Tidigare Institutioner                               , Anläggning och miljö.
    Lewan, E
    van den Hurk, B.J.J.M.
    Viterbo, P
    Grelle, A
    Lindroth, A
    Cienciala, E
    Mölder, M
    Halldin, S
    Lundin, L-C
    Boreal-forest surface parameterisation in the ECMWF model: 1D test with NOPEX long-term data.Manuskript (preprint) (Övrigt vetenskapligt)
  • 24.
    Gustafsson, David
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Magnusson, Jan
    WSL Swiss Federal Institute for Snow and Avalanche Research.
    Granlund, Nils
    Luleå University of Technology.
    Impulse radar measurements of snow interception: laboratory tests and field application to a forest stand in northern Sweden2009Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Snow melt runoff is a dominating water resource in many alpine and high latitude regions. Therefore, hydrological model predictions and information on the amount of snow are important for efficient management of for instance hydropower production. Snow interception and evaporation of snow from forest canopies is known to reduce the snow cover accumulation in forest areas compared to open areas, but there is a need for better process understanding in order to improve the model predictions. The exchange of heat and water between snow cover, canopy, and atmosphere involve many processes that can be difficult to observe at the relevant scales. Particularly, the snow interception storage is difficult to observe on a forest stand level compared with snow cover development and forest evaporation. In this study, a new application of ground penetrating impulse radar (GPR) to measure the total amount, spatial distribution and phase of the interception storage in the forest canopy is presented. The propagation velocity and frequency dependent attenuation of a broadband impulse radar wave can be used to give a direct estimate of the complex effective dielectric permittivity. The real part of the effective dielectric permittivity, estimated from the propagation velocity alone, can be used to estimate either the mass of liquid water or the mass of dry snow on the canopy if a suitable mixing formula for the effective permittivity is known. However, to separate between liquid and frozen interception additional information that we intend to get from the attenuation is needed. It has been shown for snow that the liquid water content can be estimated from the imaginary component of the effective permittivity alone. Thus, the contribution from liquid water to the real component can be subtracted, and the remaining fraction depended only on the amount of frozen snow. Laboratory experiments were performed with a GPR system, measuring the propagation velocity and frequency dependent attenuation through a sample of Norway spruce branches loaded with different amount of liquid water and snow. The results were used to establish empirical mixing formulas relating imaginary and real components of the effective dielectric permittivity to the volumetric fraction of liquid and frozen water. The obtained formulas were tested in a field application in northern Sweden, in a homogeneous stand dominated by Norway spruce. The mass of snow stored in the tree canopies were measured in two ways: firstly by measuring the weight of a single tree scaled to a forest stand average and secondly using impulse radar measurements through a small section of the forest. The transmitting and receiving antennas were placed in two small towers, separated horizontally by 15 m. The amount of intercepted snow determined from the radar measurements compared well with the measurements from the single tree weighing lysimeter, especially during cold conditions. Systematic differences were observed in situations with melting snow on the trees, when the estimation of liquid water content was overestimated by the frequency attenuation method. However, this might be due to a combination of uncertainties in the mixing models and inadequate corrections for drift in the measurement system. Overall, the results were promising and showed that impulse radar can be used to study snow interception.

  • 25.
    Gustafsson, David
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Biogeofysik.
    Magnusson, Jan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Biogeofysik.
    Grelle, Achim
    Swedish University of Agricultural Sciences.
    Lundberg, Angela
    Luleå University of Technology.
    Impact of snow interception on water and energy balance of a forest stand in northern Sweden: combining measurements with impulse radar and eddy-correlation with numerical modelling2007Konferensbidrag (Övrigt vetenskapligt)
  • 26.
    Gustafsson, David
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Sommer, Wolfram
    Sommer Mess- Systemtechnique, Austria.
    Measurement of liquid water content in snow and its applications in snow hydrological modeling2010Konferensbidrag (Övrigt vetenskapligt)
  • 27.
    Gustafsson, David
    et al.
    KTH, Tidigare Institutioner                               , Anläggning och miljö.
    Stahli, M
    Jansson, Per-Erik
    KTH, Tidigare Institutioner                               , Anläggning och miljö.
    The surface energy balance of a snow cover: comparing measurements to two different simulation models2001Ingår i: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483, Vol. 70, nr 1-4, s. 81-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We compared two one-dimensional simulation models for heat and water fluxes in the soil-snow-atmosphere system with respect to their mathematical formulations of the surface heat exchange and the snow pack evolution. They were chosen as examples of a simple one-layer snow model and a more detailed multiple-layer snow model (SNTHERM). The snow models were combined with the same one-dimensional model for the heat and water balance of the underlying soil (CoupModel). Data from an arable field in central Sweden (Marsta), covering two years (1997-1999) of soil temperature, snow depth and eddy-correlation measurements were successfully compared with the models. Conditions with a snow pack deeper or shallower than 10cm and bare soil resulted in similar discrepancies. The simulated net radiation and sensible heat flux were in good agreement with that measured during snow-covered periods, except for situations with snowmelt when the downward sensible heat flux was overestimated by 10-20 WM-2. The results showed that the uncertainties in parameter values were more important than the model formulation and that both models were useful in evaluating the limitations and uncertainties of the measurements.

  • 28.
    Gustafsson, David
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Stähli, Manfred
    WSL Swiss Federal Institute for Forest Snow and Landscape Research.
    Lundberg, Angela
    Luleå University of Technology.
    A Multi-criteria parameterisation of a numerical forest snow processes model: analysis of parameter uncertainty and governing processes2006Ingår i: , 2006Konferensbidrag (Övrigt vetenskapligt)
  • 29.
    Gustafsson, David
    et al.
    KTH, Tidigare Institutioner, Mark- och vattenteknik.
    Waldner, Peter, A.
    Stähli, Manfred
    Factors governing the formation and persistance of layers in a sub-alpine snowpack2004Ingår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 18, nr 7, s. 1165-1183Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The layered structure of a snowpack has a great effect on several important physical processes, such as water movement, reflection of solar radiation or avalanche release. Our aim was to investigate what factors are most important with respect to the formation and persistence of distinct layers in a subalpine environment. We used a physically based numerical one-dimensional model to simulate the development of a snowpack on a subalpine meadow in central Switzerland during one winter season (1998-99). A thorough model validation was based on extensive measurement data including meteorological and snow physical parameters. The model simulated the snow water equivalent and the depth of the snowpack as well as the energy balance accurately. The observed strong layering of the snowpack, however, was not reproduced satisfactorily. In a sensitivity analysis, we tested different model options and parameter settings significant for the formation of snow layers. The neglection of effects of snow microstructure on the compaction rate, and the current description of the water redistribution inside the snowpack, which disregard capillary barrier effects, preferential flow and lateral water flow, were the major limitations for a more realistic simulation of the snowpack layering.

  • 30.
    Gärdenäs, Annemieke
    et al.
    Department of Soil and Environment, Swedish University of Agricultural Sciences.
    Eckersten, Henrik
    Department of Ecology and Crop Production, Swedish University of Agricultural Sciences.
    Reinlert, André
    Dept. of Physical Geography and Ecosystems Analysis, Lund University.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Ekström, Per-Anders
    Facilia AB.
    Avila, Rodolfo
    Facilia AB.
    Greger, Maria
    Dept. of Botany, Stockholm University.
    Tracey - a simulation model of trace element fluxes in soil-plant system for long-term assessment of a radioactive groundwater contamination2009Rapport (Övrigt vetenskapligt)
  • 31. Hollaender, H. M.
    et al.
    Blume, T.
    Bormann, H.
    Buytaert, W.
    Chirico, G. B.
    Exbrayat, J. F.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Miljögeokemi och ekoteknik.
    Hoelzel, H.
    Kraft, P.
    Stamm, C.
    Stoll, S.
    Bloeschl, G.
    Fluehler, H.
    Comparative predictions of discharge from an artificial catchment (Chicken Creek) using sparse data2009Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 13, nr 11, s. 2069-2094Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ten conceptually different models in predicting discharge from the artificial Chicken Creek catchment in North-East Germany were used for this study. Soil texture and topography data were given to the modellers, but discharge data was withheld. We compare the predictions with the measurements from the 6 ha catchment and discuss the conceptualization and parameterization of the models. The predictions vary in a wide range, e.g. with the predicted actual evapotranspiration ranging from 88 to 579 mm/y and the discharge from 19 to 346 mm/y. The predicted components of the hydrological cycle deviated systematically from the observations, which were not known to the modellers. Discharge was mainly predicted as subsurface discharge with little direct runoff. In reality, surface runoff was a major flow component despite the fairly coarse soil texture. The actual evapotranspiration (AET) and the ratio between actual and potential ET was systematically overestimated by nine of the ten models. None of the model simulations came even close to the observed water balance for the entire 3-year study period. The comparison indicates that the personal judgement of the modellers was a major source of the differences between the model results. The most important parameters to be presumed were the soil parameters and the initial soil-water content while plant parameterization had, in this particular case of sparse vegetation, only a minor influence on the results.

  • 32. Holländer, H. M.
    et al.
    Bormann, H.
    Blume, T.
    Buytaert, W.
    Chirico, G. B.
    Exbrayat, J. -F
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Hölzel, H.
    Krausse, T.
    Kraft, P.
    Stoll, S.
    Blöschl, G.
    Flühler, H.
    Impact of modellers' decisions on hydrological a priori predictions2014Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 18, nr 6, s. 2065-2085Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In practice, the catchment hydrologist is often confronted with the task of predicting discharge without having the needed records for calibration. Here, we report the discharge predictions of 10 modellers - using the model of their choice - for the man-made Chicken Creek catchment (6 ha, northeast Germany, Gerwin et al., 2009b) and we analyse how well they improved their prediction in three steps based on adding information prior to each following step. The modellers predicted the catchment's hydrological response in its initial phase without having access to the observed records. They used conceptually different physically based models and their modelling experience differed largely. Hence, they encountered two problems: (i) to simulate discharge for an ungauged catchment and (ii) using models that were developed for catchments, which are not in a state of landscape transformation. The prediction exercise was organized in three steps: (1) for the first prediction the modellers received a basic data set describing the catchment to a degree somewhat more complete than usually available for a priori predictions of ungauged catchments; they did not obtain information on stream flow, soil moisture, nor groundwater response and had therefore to guess the initial conditions; (2) before the second prediction they inspected the catchment on-site and discussed their first prediction attempt; (3) for their third prediction they were offered additional data by charging them pro forma with the costs for obtaining this additional information. Hollander et al. (2009) discussed the range of predictions obtained in step (1). Here, we detail the modeller's assumptions and decisions in accounting for the various processes. We document the prediction progress as well as the learning process resulting from the availability of added information. For the second and third steps, the progress in prediction quality is evaluated in relation to individual modelling experience and costs of added information. In this qualitative analysis of a statistically small number of predictions we learned (i) that soft information such as the modeller's system understanding is as important as the model itself (hard information), (ii) that the sequence of modelling steps matters (field visit, interactions between differently experienced experts, choice of model, selection of available data, and methods for parameter guessing), and (iii) that added process understanding can be as efficient as adding data for improving parameters needed to satisfy model requirements.

  • 33.
    Jansson, Christer
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Near surface climate in an urban vegetated park and its surroundings2007Ingår i: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483, Vol. 89, nr 34, s. 185-193Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Near surface climate was observed through temperature profiling from the surface to 2.47 m height in an urban vegetated park and its surroundings in central Stockholm, Sweden. Measurements were conducted during three summer days by mobile traverses. Air temperature differences between the built-up area and the park were in the range of 0.5-0.8°C during the day and reached a maximum of 2°C at sunset. The thermal stratification of the air was mainly stable in the park and unstable in the built-up area. Inverse air temperature profiles in the park were less stable in open than in shady areas, and close to neutral at midday. The most unstable air was found in the north-south orientated canyons in the early afternoon. Possible heat advection from the surroundings, and thus uncoupling between the surface and the air, was identified through temperature gradients pointing at different directions within the 2.47 m profile. Examples at midday indicated that warm air advected as far as 150 m into the park.

  • 34.
    Jansson, Per-Erik
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Svensson, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Berggren Kleja, Dan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Simulated climate change impacts on fluxes of carbon in Norway spruce ecosystems along a climatic transect in Sweden2008Ingår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 89, nr 1, s. 81-94Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A simulation study based on recent regional climate scenarios for Sweden investigated possible changes in carbon (C) dynamics and net ecosystem exchange (NEE) of Swedish Norway spruce forest ecosystems. Four sites, representative of well-drained soils in four regions, were included. Stand development was simulated for a 100-year rotation period using a coupled model describing abiotic and biotic processes in the soil-plant-atmosphere system. Two IPCC climate change scenarios, corresponding to a mean annual temperature increase of about 2 degrees C (A2) or 3 degrees C (B2) from the reference period 1961-1990 to a new period 2061-2090, were considered. Annual maximum snow depth decreased with the increase in air temperature, whereas maximum soil frost depth and mean annual soil temperature showed only small changes, especially for the sites in northern Sweden. Simulations suggested that in the warmer climate, gross primary production (GPP) increased by 24-32% in northern Sweden and by 32-43% in the south. In the north, the increase was related to the combined effect of air and soil temperature extending the growing season, whereas in the south it was mainly governed by increased N availability due to increased soil temperature. NEE increased by about 20% (A2) or 25% (B2) at all sites, more or less solely due to increased accumulation of C in the tree biomass (including harvest residues), since changes in soil C were small compared with the current climate. Both light use efficiency and water use efficiency were improved in the future climate scenarios, despite increases in atmospheric CO2 not being considered.

  • 35.
    Juston, John
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Rating curve uncertainty and change detection in discharge time series: Case study with 44-year historic data from the Nyangores River, Kenya2014Ingår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 28, nr 4, s. 2509-2523Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The intersection of the developing topic of rating curve and discharge series uncertainty with the topic of hydrological change detection (e.g., in response to land cover or climatic change) has not yet been well studied. The work herein explores this intersection, with consideration of a long-term discharge response (1964-2007) for a ~650-km2 headwater basin of the Mara River in west Kenya, starting with stream rating and daily gauge height data. A rating model was calibrated using Bayesian methods to quantify uncertainty intervals in model parameters and predictions. There was an unknown balance of random and systemic error in rating data scatter (a scenario not likely unique to this basin), which led to an unknown balance of noise and information in the calibrated statistical error model. This had implications on testing for hydrological change. Overall, indications were that shifts in basin's discharge response were rather subtle over the 44-year period. A null hypothesis for change using flow duration curves (FDCs) from four different 8-year data intervals could be either accepted or rejected over much of the net flow domain depending on different applications of the statistical error model (each with precedence in the literature). The only unambiguous indication of change in FDC comparisons appeared to be a reduction in lowest baseflow in recent years (flows with >98% exceedance probability). We defined a subjective uncertainty interval based on an intermediate balance of random and systematic error in the rating model that suggested a possibility of more prevalent impacts. These results have relevance to management in the Mara basin and to future studies that might establish linkages to historic land use and climatic factors. The concern about uncertain uncertainty intervals (uncertainty2) extends beyond the Mara and is relevant to testing change where non-random rating errors may be important and subtle responses are investigated.

  • 36. Karlberg, Louise
    et al.
    Gustafsson, David
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Miljögeokemi och ekoteknik.
    Modeling carbon turnover in five terrestrial ecosystems in the boreal zone using multiple criteria of acceptance2006Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 35, nr 8, s. 448-458Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Estimates of carbon fluxes and turnover in ecosystems are key elements in the understanding of climate change and in predicting the accumulation of trace elements in the biosphere. In this paper we present estimates of carbon fluxes and turnover times for five terrestrial ecosystems using a modeling approach. Multiple criteria of acceptance were used to parameterize the model, thus incorporating large amounts of multi-faceted empirical data in the simulations in a standardized manner. Mean turnover times of carbon were found to be rather similar between systems with a few exceptions, even though the size of both the pools and the fluxes varied substantially. Depending on the route of the carbon through the ecosystem, turnover times varied from less than one year to more than one hundred, which may be of importance when considering trace element transport and retention. The parameterization method was useful both in the estimation of unknown parameters, and to identify variability in carbon turnover in the selected ecosystems.

  • 37.
    Karlberg, Louise
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Modelling carbon and water flows in terrestrial ecosystems in the boreal zone: Examples from Oskarshamn2006Rapport (Övrigt vetenskapligt)
  • 38.
    Karlberg, Louise
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Miljögeokemi och ekoteknik.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Miljögeokemi och ekoteknik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Miljögeokemi och ekoteknik.
    Model-based evaluation of low-cost drip-irrigation systems and management strategies using saline water2007Ingår i: Irrigation science, ISSN 0342-7188, E-ISSN 1432-1319, Vol. 25, nr 4, s. 387-399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A drip-irrigation module was developed and included in an ecosystem model and tested on two independent datasets, spring and autumn, on field-grown tomato. Simulated soil evaporation correlated well with measurements for spring (2.62 mm d(-1) compared to 2.60 mm d(-1)). Changes in soil water content were less well portrayed by the model (spring r(2) = 0.27; autumn r(2) = 0.45). More independent data is needed for further model testing in combination with developments of the spatial representation of below-ground variables. In a fresh-water drip-irrigated system, about 30% of the incoming water was transpired, 40% was lost as non-productive evaporative flows, and the remainder left the system as surface runoff or drainage. Simulations showed that saline water irrigation (6 dS m(-1)) caused reduced transpiration, which led to higher drainage and soil evaporation, compared with fresh water. Covering the soil with plastic mulch resulted in an increase in yield and transpiration. Finally, two different drip-irrigation discharge rates (0.2 and 2.5 l h(-1)) were compared; however the simulations indicated that the discharge rate did not have any impact on the partitioning of the incoming water to the system. The model proved to be a useful tool for evaluating the importance of specific management options.

  • 39. Keller, T
    et al.
    Pielmeier, C
    Rixen, C
    Gadient, F
    Gustafsson, David
    Stähli, M
    Impact of artificial snow and ski slope grooming on the snow pack properties and the soil thermal regime in a sub-alpine area2004Ingår i: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 38, s. 314-318Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Studies have indicated that the soil on groomed ski slopes may be subjected to more pronounced cooling than the soil below a natural snowpack. We analyzed the thermal impacts of ski-slope preparation in a sub-alpine ski resort in central Switzerland (1100 in a.s.l.) where artificial snow was produced. Physical snow properties and soil temperature measurements were carried out on the ski slope and off-piste during winter 1999/2000. The numerical soil-vegetation-atmosphere transfer model COUP was run for both locations, with a new option to simulate the snowpack development on a groomed ski slope. Snow density. snow hardness and thermal conductivity were significantly higher on the ski slope than in the natural snowpack. However, these differences did rift affect the cooling of the soil, since no difference was observed between the ski slope and the natural snow cover. This might be because cold periods were rare and short and thus any snowpack could protect the soil from freezing. The major impact of the ski-slope grooming was a 4 week delay in snowmelt and soil warming at the end of the season. The newly implemented option proved to be a useful strategy for simulating the snowpack of a ski slope. However, snow density was underestimated by the model as it could not account adequately for compaction due to grooming traffic. Our study demonstrates that there is no site-independent answer as to whether a groomed snowpack affects the thermal conditions in the soil.

  • 40. Klemedtsson, Leif
    et al.
    Jansson, Per-Erik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Miljögeokemi och ekoteknik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Miljögeokemi och ekoteknik.
    Karlberg, Louise
    Weslien, Per
    von Arnold, Karin
    Ernfors, Maria
    Langvall, Ola
    Lindroth, Anders
    Bayesian calibration method used to elucidate carbon turnover in forest on drained organic soil2008Ingår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 89, nr 1, s. 61-79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Depending on the balance between sink and source processes for C, drained organic forest soil ecosystems can be in balance or act as net sinks or sources of CO2 to the atmosphere. In order to study the effect of groundwater level and soil temperature on C-flux, the CoupModel was calibrated (climate data, groundwater levels, soil CO2 flux, net ecosystem fluxes of CO2-exchange, sensible heat flux and latent heat flux, forest production etc.) for a drained forest in Sweden. Bayesian calibration techniques were used to elucidate how different parameters and variables were interlinked in C-circulation. The calibrated model reproduced abiotic and biotic variables reasonably well except for root respiration, which was largely underestimated. Bayesian calibration reduced the uncertainties in the model and highlighted the fact that calibrations should be performed with a high number of parameters instead of specific parameter values.

  • 41.
    Lehning, Michael
    et al.
    WSL Swiss Federal Institute of Snow and Avalanche Research.
    Bartelt, P.
    Swiss Federal Institute of Snow and Avalanche Research.
    Bethke, S.
    Swiss Federal Institute of Snow and Avalanche Research.
    Fierz, C.
    Swiss Federal Institute of Snow and Avalanche Research.
    Gustafsson, David
    Swiss Federal Institute of Snow and Avalanche Research.
    Landl, B.
    Swiss Federal Institute of Snow and Avalanche Research.
    Martius, O.
    Swiss Federal Institute of Snow and Avalanche Research.
    Meirold, M.
    Swiss Federal Institute of Snow and Avalanche Research.
    Radershall, N.
    Swiss Federal Institute of Snow and Avalanche Research.
    Rhyner, J.
    Swiss Federal Institute of Snow and Avalanche Research.
    Stähli, M.
    Swiss Federal Institute of Snow and Avalanche Research.
    Review of SNOWPACK and ALPINE3D applications2004Ingår i: Snow Engineering V: Proceedings of the Fifth International Conference on Snow Engineering, 5-8 July 2004, Davos, Switzerland / [ed] Bartelt P., Sack R., Sato, A., Adams. E., Christen M., Balkema, 2004, s. 299-307Konferensbidrag (Refereegranskat)
  • 42. Lehning, Michael
    et al.
    Voelksch, Ingo
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Miljögeokemi och ekoteknik.
    Nguyen, Tuan Anh
    Staehli, Manfred
    Zappa, Massimiliano
    ALPINE3D: a detailed model of mountain surface processes and its application to snow hydrology2006Ingår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 20, nr 10, s. 2111-2128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Current models of snow cover distribution, soil moisture. surface runoff and river discharge typically have very simple parameterizations of surface processes, such as degree-day factors or single-layer snow cover representation. For the purpose of reproducing catchment runoff, simple snowmelt routines have proven to be accurate, provided that they are carefully calibrated specifically for the catchment they are applied to. The use of more detailed models is, however. useful to understand and quantify the role of individual surface processes for catchment hydrology, snow cover status and soil moisture distribution. We introduce ALPINE3D, a model for the high-resolution simulation of alpine surface processes. in particular snow processes. The model can be driven by measurements from automatic weather stations or by meteorological model outputs. As a preprocessing alternative, specific high-resolution meteorological fields can be created by running a meteorological model. The core three-dimensional ALPINE3D modules consist of a radiation balance model (which uses a view-factor approach and includes shortwave scattering and Ion-wave emission from terrain and tall vegetation) and a drifting snow model solving a diffusion equation for suspended snow and a saltation transport equation. The processes in the atmosphere are thus treated in three dimensions and are coupled to a distributed (in the hydrological sense of having a spatial representation of the catchment properties) one-dimensional model of vegetation, snow and soil (SNOWPACK) using the assumption that lateral exchange is small in these media. The model is completed by a conceptual runoff module. The model can be run with a choice of modules, thus generating more or less detailed surface forcing data as input for runoff generation simulations. The model modules can be run in a parallel (distributed) mode using a GRID infrastructure to allow computationally demanding tasks. In a case study from the Dischma Valley in eastern Switzerland, we demonstrate that the model is able to simulate snow distribution as seen from a NOAA advanced very high-resolution radiometer image. We then analyse the sensitivity of simulated snow cover distribution and catchment runoff to the use of different surface process descriptions. We compare model runoff simulations with runoff data from 10 consecutive years. The quantitative analysis shows that terrain influence on the radiation processes has a significant influence on catchment hydrology dynamics. Neglecting the role of vegetation and the spatial variability of the soil, on the other hand, had a much smaller influence on the runoff generation dynamics. We conclude that ALPINE3D is a valuable tool to investigate surface dynamics in mountains. It is currently used to investigate snow cover dynamics for avalanche warning and permafrost development and vegetation changes under climate change scenarios. It could also serve to test the output of simpler soil - vegetation - atmosphere transfer schemes used in larger scale climate or meteorological models and to create accurate soil moisture assessments for meteorological and flood forecasting.

  • 43.
    Lind, Bo
    et al.
    Swedish Geotechnical Institute, SGI.
    Larsson, L.
    Gustafsson, Jon-Petter
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Miljögeokemi och ekoteknik.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Biogeofysik.
    Ohlsson, Susanna
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Miljögeokemi och ekoteknik.
    Norrman, J.
    Arvidsson, O.
    Arm, M.
    Energiaska som vägbyggnadsmaterial - utlakning och miljöbelastning från en provväg2005Rapport (Övrigt vetenskapligt)
  • 44.
    Lundberg, Angela
    et al.
    Luleå University of Technology.
    Granlund, Nils
    Luleå University of Technology.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Review of operational and new ground-based snow measurement methods for Sweden, Norway and Finland2009Ingår i: The 65th Annual Meeting of the Eastern Snow Conference, 2009Konferensbidrag (Övrigt vetenskapligt)
  • 45. Lundberg, Angela
    et al.
    Granlund, Nils
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Towards automated 'Ground truth' snow measurements: a review of operational and new measurement methods for Sweden, Norway, and Finland2010Ingår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 24, nr 14, s. 1955-1970Artikel i tidskrift (Refereegranskat)
    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) gamma-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 (C) 2010 John Wiley & Sons, Ltd.

  • 46.
    Lundberg, Angela
    et al.
    Luleå University of Technology.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Biogeofysik.
    Sensitivity of snow process simulations to precipitation phase transition method in forested and open areas2009Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Modeling of forest snow processes is complicated and especially problematic seems to be the separation of precipitation phase in climates where a large part of the precipitation falls at temperatures near zero degrees Celsius. When the precipitation is classified as snow, the tree crowns can carry an order of magnitude more canopy storage as compared to when the precipitation is classified as rain, and snow in the trees also alters the albedo of the forest while rain does not. Many different schemes for the precipitation phase separation are used by various snow models. Some models use just one air temperature threshold (TR/S) below which all precipitation is assumed to be snow and above which all precipitation is classified as rain. A more common approach for forest snow models is to use two temperature thresholds. The snow fraction (SF) is then set to one below the snow threshold (TS) and to zero above the rain threshold (TR) and SF is assumed to decrease linearly between these two thresholds. Also more sophisticated schemes exist, but three seems to be a lack of agreement on how the precipitation phase separations should be performed. The aim with this study is to use a hydrological model including canopy snow processes to illustrate the sensitivity for different formulations of the precipitation phase separation on a) the simulated maximum snow pack storage b) the interception evaporation loss and c) snow melt runoff. In other words, to investigate of the choice of precipitation phase separation has an impact on the simulated wintertime water balance. Simulations are made for sites in different climates and for both open fields and forest sites in different regions of Sweden from north to south. In general, precipitation phase separation methods that classified snowfall at higher temperatures resulted in a larger proportion of the precipitation lost by interception evaporation as a result of the increased interception capacity. However, the maximum snow accumulation was also increased in some cases due to the overall increased snowfall, depending on canopy density and precipitation and temperature regimes. Results show that the choice of precipitation phase separation method can have an significant impact on the simulated wintertime water balance, especially in forested regions.

  • 47. Magnusson, Jan
    et al.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik. Swedish Meteorological and Hydrological Institute, Sweden .
    Hüsler, Fabia
    Jonas, Tobias
    Assimilation of point SWE data into a distributed snow cover model comparing two contrasting methods2014Ingår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 50, nr 10, s. 7816-7835Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In alpine and high-latitude regions, water resource decision making often requires large-scale estimates of snow amounts and melt rates. Such estimates are available through distributed snow models which in some situations can be improved by assimilation of remote sensing observations. However, in regions with frequent cloud cover, complex topography, or large snow amounts satellite observations may feature information of limited quality. In this study, we examine whether assimilation of snow water equivalent (SWE) data from ground observations can improve model simulations in a region largely lacking reliable remote sensing observations. We combine the model output with the point data using three-dimensional sequential data assimilation methods, the ensemble Kalman filter, and statistical interpolation. The filter performance was assessed by comparing the simulation results against observed SWE and snow-covered fraction. We find that a method which assimilates fluxes (snowfall and melt rates computed from SWE) showed higher model performance than a control simulation not utilizing the filter algorithms. However, an alternative approach for updating the model results using the SWE data directly did not show a significantly higher performance than the control simulation. The results show that three-dimensional data assimilation methods can be useful for transferring information from point snow observations to the distributed snow model.

    Key Points

    • Evaluating methods for assimilating snow observations into distributed models
    • Assimilation can improve model skill also at locations without observations
    • Assimilation of fluxes appears more successful than assimilation of states
  • 48. Mellander, P. E.
    et al.
    Stahli, M.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Miljögeokemi och ekoteknik.
    Bishop, K.
    Modelling the effect of low soil temperatures on transpiration by Scots pine2006Ingår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 20, nr 9, s. 1929-1944Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For ecosystem modelling of the Boreal forest it is important to include processes associated with low soil temperature during spring-early summer, as these affect the tree water uptake. The COUP model, a physically based SVAT model, was tested with 2 years of soil and snow physical measurements and sap flow measurements in a 70-year-old Scots pine stand in the boreal zone of northern Sweden. During the first year the extent and duration of soil frost was manipulated in the field. The model was successful in reproducing the timing of the soil warming after the snowmelt and frost thaw. A delayed soil warming, into the growing season, severely reduced the transpiration. We demonstrated the potential for considerable overestimation of transpiration by the model if the reduction of the trees' capacity to transpire due to low soil temperatures is not taken into account. We also demonstrated that the accumulated effect of aboveground conditions could be included when simulating the relationship between soil temperature and tree water uptake. This improved the estimated transpiration for the control plot and when soil warming was delayed into the growing season. The study illustrates the need of including antecedent conditions on root growth in the model in order to catch these effects on transpiration. The COUP model is a promising tool for predicting transpiration in high-latitude stands.

  • 49. Musselman, Keith N.
    et al.
    Molotch, Noah P.
    Margulis, Steven A.
    Lehning, Michael
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Improved snowmelt simulations with a canopy model forced with photo-derived direct beam canopy transmissivity2012Ingår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, nr 10, s. W10509-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The predictive capacity of a physically based snow model to simulate point-scale, subcanopy snowmelt dynamics is evaluated in a mixed conifer forest, southern Sierra Nevada, California. Three model scenarios each providing varying levels of canopy structure detail were tested. Simulations of three water years initialized at locations of 24 ultrasonic snow depth sensors were evaluated against observations of snow water equivalent (SWE), snow disappearance date, and volumetric soil water content. When canopy model parameters canopy openness and effective leaf area index were obtained from satellite and literature-based sources, respectively, the model was unable to resolve the variable subcanopy snowmelt dynamics. When canopy parameters were obtained from hemispherical photos, the improvements were not statistically significant. However, when the model was modified to accept photo-derived time-varying direct beam canopy transmissivity, the error in the snow disappearance date was reduced by as much as one week and positive and negative biases in melt-season SWE and snow cover duration were significantly reduced. Errors in the timing of soil meltwater fluxes were reduced by 11 days on average. The optimum aggregated temporal model resolution of direct beam canopy transmissivity was determined to be 30 min; hourly averages performed no better than the bulk canopy scenarios and finer time steps did not increase overall model accuracy. The improvements illustrate the important contribution of direct shortwave radiation to subcanopy snowmelt and confirm the known nonlinear melt behavior of snow cover.

  • 50. Rasmus, S.
    et al.
    Gustafsson, David
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Koivusalo, H.
    Laurén, A.
    Grelle, A.
    Kauppinen, O. -K
    Lagnvall, O.
    Lindroth, A.
    Rasmus, K.
    Svensson, M.
    Weslien, P.
    Estimation of winter leaf area index and sky view fraction for snow modelling in boreal coniferous forests: Consequences on snow mass and energy balance2013Ingår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 27, nr 20, s. 2876-2891Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Leaf area index (LAI) and canopy coverage are important parameters when modelling snow process in coniferous forests, controlling interception and transmitting radiation. Estimates of LAI and sky view factor show large variability depending on the estimation method used, and it is not clear how this is reflected in the calculated snow processes beneath the canopy. In this study, the winter LAI and sky view fraction were estimated using different optical and biomass-based approximations in several boreal coniferous forest stands in Fennoscandia with different stand density, age and site latitude. The biomass-based estimate of LAI derived from forest inventory data was close to the values derived from the optical measurements at most sites, suggesting that forest inventory data can be used as input to snow hydrological modelling. Heterogeneity of tree species and site fertility, as well as edge effects between different forest compartments, caused differences in the LAI estimates at some sites. A snow energy and mass balance model (SNOWPACK) was applied to detect how the differences in the estimated values of the winter LAI and sky view fraction were reflected in simulated snow processes. In the simulations, an increase in LAI and a decrease in sky view fraction changed the snow surface energy balance by decreasing shortwave radiation input and increasing longwave radiation input. Changes in LAI and sky view fraction affected directly snow accumulation through altered throughfall fraction and indirectly snowmelt through the changed surface energy balance. Changes in LAI and sky view fraction had a greater impact on mean incoming radiation beneath the canopy than on other energy fluxes. Snowmelt was affected more than snow accumulation. The effect of canopy parameters on evaporation loss from intercepted snow was comparable with the effect of variation in governing meteorological variables such as precipitation intensity and air temperature.

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