| 1. |
- Blösch, Günter, et al.
(författare)
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Twenty-three unsolved problems in hydrology (UPH) - a community perspective
- 2019
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 64:10, s. 1141-1158
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Tidskriftsartikel (refereegranskat)abstract
- This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.
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| 2. |
- Feiccabrino, James M., et al.
(författare)
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A new GIS landscape classification method for rain/snow temperature thresholds in surface based models
- 2017
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 48:4, s. 902-914
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Tidskriftsartikel (refereegranskat)abstract
- Landscape air temperature thresholds (TA) and percent misclassified precipitation (error) for 12 years of meteorological observations from 40 stations across the Scandinavian Peninsula were derived and compared using both manual and geographic information system (GIS) landscape classification methods. Dew-point, wet-bulb, and wet bulb 0.5 were also tested. Both classification methods used the following west to east landscape categories: windward (WW) ocean, coast, fjord, hill, and mountain in Norway; and leeward (LW) mountain, hill, rolling terrain, and coast in Sweden. GIS landscape classification has the advantages of automating the classification process and increasing objectivity. The GIS classification was based on station location (LW or WW) relative to the Scandinavian mountain range, and the % water or range of elevation change within 15 km. The GIS and manual method had the same TA for 20 stations, and similar total reduction in error (2.29 to 2.17% respectively) when compared to country TA. Therefore, automated GIS landscape classification can be used to decrease error from common country or global scale TA. Wet-bulb temperature thresholds for GIS landscapes resulted in a greater reduction in error (8.26%) compared to air (2.29%), and dew-point (-16.67%) thresholds. However, finding stations reporting relative humidity or wetbulb temperature may limit its widespread use.
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| 3. |
- Feiccabrino, James, et al.
(författare)
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Meteorological Knowledge Useful for the Improvement of Snow Rain Separation in Surface Based Models
- 2015
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Ingår i: Hydrology. - : MDPI AG. - 2306-5338. ; 2:4, s. 266-288
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Tidskriftsartikel (refereegranskat)abstract
- An accurate precipitation phase determination—i.e., solid versus liquid—is of paramount importance in a number of hydrological, ecological, safety and climatic applications. Precipitation phase can be determined by hydrological, meteorological or combined approaches. Meteorological approaches require atmospheric data that is not often utilized in the primarily surface based hydrological or ecological models. Many surface based models assign precipitation phase from surface temperature dependent snow fractions, which assume that atmospheric conditions acting on hydrometeors falling through the lower atmosphere are invariant. This ignores differences in phase change probability caused by air mass boundaries which can introduce a warm air layer over cold air leading to more atmospheric melt energy than expected for a given surface temperature, differences in snow grain-size or precipitation rate which increases the magnitude of latent heat exchange between the hydrometers and atmosphere required to melt the snow resulting in snow at warmer temperatures, or earth surface properties near a surface observation point heating or cooling a shallow layer of air allowing rain at cooler temperatures or snow at warmer temperatures. These and other conditions can be observed or inferred from surface observations, and should therefore be used to improve precipitation phase determination in surface models.
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| 4. |
- Feiccabrino, James
(författare)
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Precipitation phase determination in cold region conceptual models - analysis and method development
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Precipitation phase uncertainty is a known source of error in conceptual models used for many hydrological, climatological, and environmental applications. These conceptual models often use the simple approach of calibrating an air temperature threshold (TRS) over a large area irrespective of physiographic characteristics such as distance to the ocean and topographic relief. Conceptual modeling requires empirical formulas to simplify physical processes. However, there is a plethora of literature against this TRS approach. The magnitude of uncertainty caused by the use of a set TRS is greatest in areas such as Scandinavia, where an average of 39% annual station precipitation occurs in the air temperature (TA) range of -3 to 5°C. One argument for the use of set threshold temperatures in conceptual models was the reduction of computational load, but this came at the cost of accuracy. To compound this error, surface conditions only have a minor contribution to the surface precipitation phase. Instead, microphysics (air-hydrometeor energy exchanges) and properties of the air in the lower atmosphere are the major influences on the observed precipitation phase. However, without adding atmospheric data, improvements to cold region conceptual model, precipitation phase can be achieved through the use of other reported surface data. Meteorological data from 169 observing stations were used to determine percent misclassified precipitation when air temperature (TA), Wet-bulb temperature 0.5°C (TW 0.5°C) thresholds, and an air temperature adjusted by relative humidity (TRH) = 0.75+0.085*(100-RH) formula were applied. The main dataset had roughly 400,000 precipitation events between TA -3 and 5°C. When analysed by country, Norwegian stations had average misclassified precipitation of 10.8% (1.2°C) for TA, 8.3% for TW 0.5°C, and 8.7% for TRH. In comparison, Swedish stations had misclassified precipitation totals of 9.3% (0.9°C) for TA, 8.2% for TW 0.5°C, and 8.7% for TRH. TW 0.5°C resulted in the least misclassified precipitation for both countries. However, saturation vapor pressure, relative humidity (RH), and other parameters required to calculate TW are often not reported by hydrological or meteorological stations. Therefore, improvement in TA methods is preferential over TW or RH methods. Cloud base height TA thresholds were found to increase with height and could be used as a proxy for RH. Cloud base height thresholds had 10.3%, and 9.1% misclassified precipitation in Norway and Sweden respectively. This method had greater error than RH, but performed better in low cloud conditions (100m in Norway and 300m in Sweden), so combining the methods is an option. However, cloud base height is not reported by all stations. If restricted to TA methods, sub-grouping stations by physiographic characteristics within a 15km radius decreased TA misclassified precipitation by 0.5% in Norway with little change in Sweden. This is a result of the Norwegian landscape varying to a greater extent than in Sweden. TA thresholds in Norway ranged from 2.4°C for ocean platforms to 0.9°C in the hills. Particularly high misclassified precipitation rates in mountains and hills can be reduced by nearly 10% when assigning TA for different station sub-groups using 1km maximum elevation or relief. For oceans/coast stations, TA assigned for water temperature sub-groups (reported by 16 stations) reduced misclassified precipitation by 17%. Models applying a daily TA threshold, had precipitation phase uncertainty reduced 10% with RH methods. Changing to an hourly timestep reduced error by more than 29%. Therefore, decreasing temporal resolution to 1-hour was more beneficial than adding parameters to the 24-hour model.
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| 5. |
- Lundberg, Angela, et al.
(författare)
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Spatiotemporal Variations in Snow and Soil Frost : A Review of Measurement Techniques
- 2016
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Ingår i: Hydrology. - : MDPI AG. - 2306-5338. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 6. |
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