| 1. |
- Franzén, Lars, 1950, et al.
(författare)
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The potential peatland extent and carbon sink in Sweden, as related to the Peatland / Ice Age Hypothesis
- 2012
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Ingår i: Mires and Peat. - 1819-754X. ; 10:artikel nr 08, s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands cover approximately 65,600 km2 (16 %) of the Swedish land area. The available areas suitable for peatland expansion are far from occupied after ca. 12,000 years of the present interglacial. We estimate the potential extent of peatland in Sweden, based on slope properties of possible areas excluding lakes and glaciofluvial deposits. We assume no human presence or anthropic effects, so the calculation is speculative. It may have been relevant for previous interglacials. We calculate the potential final area of peatlands in three scenarios where they cover all available land with different maximum slope angles (1−3 º) using a Digital Elevation Model (DEM). The three scenarios yield potential peatland areas of 95,663 km2 (21 % of total available area), 168,287 km2 (38 %) and 222,141 km2 (50 %). The relative increases from the present 65,600 km2 are 46, 157 and 239 % respectively. The slope scenarios give CO2 uptake rates of 8.9−10.8, 18.1−22.4 and 24.6−30.5 Mt yr−1. Under global warming conditions with isotherms moved northwards and to higher altitudes, following an increase of raised bog area, the CO2 uptake rates might increase to 12.2−13.8, 24.4−27.7 and 33.5−37.9 Mt yr−1; i.e. up to 4.3−4.9 vpb of atmospheric CO2. If we make the speculative extrapolation from Sweden to all high latitude peatlands, and assume that all suitable areas with slope angle ≤ 3 ° become occupied, the global peatland CO2 sink might approach 3.7 Gt yr−1 (about 2 vpm yr−1) and potentially cause a net radiative cooling approaching 5 W m−2.
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| 2. |
- Johansson, Lars, 1972, et al.
(författare)
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Statistical modelling of pedestrian wind speed using high‐resolution digital surface models
- 2012
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Ingår i: The Eight International Conference on Urban Climates. ; :abstract 183
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Spatial variations of near ground wind speed (2magl) within urban areas are simulated by using a statistical model. The model is built upon the statistical relationship between derivatives extracted from digital surface models characterizing urban geometries (sky view factor, fetch, frontal area index) and wind speed, using statistical regression techniques. The geometric parameters are calculated for a number of urban settings in Gothenburg, Sweden. Wind speed patterns are derived using the three-dimensional microclimate model, ENVI-met. The model closely estimate the wind speed within-the major parts of the model domains such as in squares, and narrow streets as well as canyons perpendicular to the incoming wind direction. However, the output wind speed patterns are largely different from the wind speed simulated by ENVI-met in wide streets and around buildings where wind speed is high. Statistical models, as presented here, would be useful for not only climatologist/ meteorologist but also urban designers to consider wind modes depending on urban geometries and also to estimate thermal comfort influenced by wind.
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| 3. |
- Konarska, Janina, 1986, et al.
(författare)
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Transmissivity of solar radiation through crowns of single urban trees—application for outdoor thermal comfort modelling
- 2014
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Ingår i: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 117:3-4, s. 363-376
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Tidskriftsartikel (refereegranskat)abstract
- Trees play an important role in mitigating heat stress on hot summer days, mainly due to their ability to provide shade. However, an important issue is also the reduction of solar radiation caused by trees in winter, in particular at high latitudes. In this study, we examine the transmissivity of total and direct solar radiation through crowns of single street trees in Göteborg, Sweden. One coniferous and four deciduous trees of species common in northern European cities were selected for case study. Radiation measurements were conducted on nine clear days in 2011–2012 in foliated and leafless tree conditions using two sunshine pyranometers— one located in shade of a tree and the other one on the roof of an adjacent building. The measurements showed a significant reduction of total and direct shortwave radiation in the shade of the studied trees, both foliated and leafless. Average transmissivity of direct solar radiation through the foliated and defoliated tree crowns ranged from 1.3 to 5.3 % and from 40.2 to 51.9 %, respectively. The results confirm the potential of a single urban tree to reduce heat stress in urban environment. However, the relatively low transmissivity through defoliated trees should be considered while planning street trees in high latitude cities, where the solar access in winter is limited. The results were used for parameterisation of SOLWEIG model for a better estimation of the mean radiant temperature (Tmrt). Measured values of transmissivity of solar radiation through both foliated and leafless trees were found to improve the model performance.
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| 4. |
- Lindberg, Fredrik, 1974, et al.
(författare)
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3D modelling of vegetation within a 2D model – evaluation and application
- 2012
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Ingår i: The Eight International Conference on Urban Climates.. ; :abstract nr 180
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The SOlar and LongWave Environmental Irradiance Geometry (SOLWEIG) model simulates spatial variations of 3D radiation fluxes and mean radiant temperature (Tmrt) as well as shadow patterns in complex urban settings. Here, a new vegetation scheme is presented and evaluated. A new shadow casting algorithm for complex vegetation structures makes it possible to obtain continuous images of shadow patterns and sky view factors taking both buildings and vegetation into account. The model is evaluated using 5 days of integral radiation measurements at two sites within a square surrounded by low-rise buildings and vegetation in Göteborg, Sweden (57°N). There is good agreement between modelled and observed values of Tmrt. Furthermore, SOLWEIG is used to examine vegetation and building morphology characteristics through a north-south LiDAR transect across the megacity of London. It is shown that the contribution of vegetation to the shadowing and reduction of Tmrt at ground level is higher during summer than in autumn. The results from these simulations highlight that vegetation can be most effective at reducing heat stress within dense urban environments in summer. The daytime average Tmrt is found to be lowest in the densest urban environments due to shadowing; foremost from buildings but also from trees. It is clearly shown that this method could be used to quantify the influence of vegetation on Tmrt within the urban environment. The results presented in this paper highlight a number of possible climate sensitive planning practices for urban areas at the local scale.
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| 5. |
- Lindberg, Fredrik, 1974, et al.
(författare)
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Characteristics of the mean radiant temperature in high latitude cities—implications for sensitive climate planning applications
- 2014
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Ingår i: International Journal Of Biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 58:5, s. 613-627
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of how the mean radiant temperature (T mrt ) is affected by factors such as location, climate and urban setting contributes to the practice of climate sensitive planning. This paper examines how T mrt varies within an urban setting and how it is influenced by cloudiness. In addition, variations of T mrt in three high latitude cities are investigated in order to analyse the impact of geographical context and climate conditions. Results showed large spatial variations between sunlit and shaded areas during clear weather conditions, with the highest values of T mrt close to sunlit walls and the lowest values in the areas shaded by buildings and vegetation. As cloudiness increases, the spatial pattern is altered and the differences are reduced. The highest T mrt under cloudy conditions is instead found in open areas where the proportion of shortwave diffuse radiation from the sky vault is high. A regional comparison between three Swedish coastal cities showed that T mrt during summer is similar regardless of latitudinal location. On the other hand, large differences in T mrt during winter were found. Shadows, both from buildings and vegetation are the most effective measure to reduce extreme values of T mrt . However, extensive areas of shadow are usually not desired within outdoor urban environments at high latitude cities. One solution is to create diverse outdoor urban spaces in terms of shadow and also ventilation. This would provide individuals with access to a choice of thermal environments which they can use to assist their thermal regulation, based on personal needs and desires.
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| 6. |
- Lindberg, Fredrik, 1974, et al.
(författare)
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Impact of city changes and weather on anthropogenic heat flux in Europe 1995–2015
- 2013
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Ingår i: Urban Climate. - 2212-0955. ; 4, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- How people live, work, move from place to place, consume and the technologies they use all affect heat emissions in a city which influences urban weather and climate. Here we document changes to a global anthropogenic heat flux (QF) model to enhance its spatial (30'' x 30'' to 0.5° x 0.5°) resolution and temporal coverage (historical, current and future). QF is estimated across Europe (1995–2015), considering changes in temperature, population and energy use. While on average QF is small (of the order 1.9–4.6Wm2 across all the urban areas of Europe), significant spatial variability is documented (maximum 185Wm2). Changes in energy consumption due to changes in climate are predicted to cause a 13% (11%) increase in QF on summer (winter) weekdays. The largest impact results from changes in temperature conditions which influences building energy use; for winter, with the coldest February on record, the mean flux for urban areas of Europe is 4.56 W m-2 and for summer (warmest July on record) is 2.23 W m-2. Detailed results from London highlight the spatial resolution used to model the QF is critical and must be appropriate for the application at hand, whether scientific understanding or decision making.
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| 7. |
- Lindberg, Fredrik, 1974, et al.
(författare)
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Infrastrukturnära vegetation i Göteborg
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Ett flertal ekosystemtjänster kan identifieras utifrån vegetation inom urbana områden, så som biologisk mångfald, klimatreglering, luft- och vattenrening, markhantering, ljuddämpning samt rekreation och välbefinnande. Den här studien fokuserar på grönska i områden i anslutning av infrastruktur. Studien använder sig av Laserscannat flygdata (LiDAR) som är en relativt ny metod där man har möjlighet av kartera utbredning och diverse egenskaper av högre vegetation (träd och buskar) med mycket stor noggrannhet. Resultat från studien visar att andelen högre vegetation nära infrastruktur är betydligt mindre (halverad) än den totala referensytan (Göteborgs kommun). Försök att uppskatta den årliga ackumuleringen av kol i biomassa med hjälp av LiDAR-data, som ett exempel på en ekosystemtjänst, har också enomförts. Resultat från dessa försök visar på stora osäkerheter och vid tolkning av resultaten av sådana beräkningar är det viktigt att tänka på att de specifika värdena endast är grova approximationer; modellen antar ett uniformt förhållande mellan biomassa och vegetationstäcke, medan det i verkligheten finns stora variationer mellan olika platser, främst beroende på varierande ålder- och artsammansättning. Dessa genskaper kan inte tas fram med hjälp av LiDAR.
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| 8. |
- Lindberg, Fredrik, 1974, et al.
(författare)
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Mapping areas of potential slope failures in cohesive soils using a shadow-casting algorithm – A case study from SW Sweden
- 2011
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Ingår i: Computers and Geotechnics. - : Elsevier BV. - 0266-352X. ; 38, s. 791-799
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Tidskriftsartikel (refereegranskat)abstract
- When performing landslide susceptibility mapping of rotational slides in fine grained soils, slope algorithms found in common GIS software have two major shortcomings. Firstly, these types of terrain algorithms only consider the slope angle at the surface. Secondly, the algorithm is local by its design i.e. it only considers neighbouring pixels. Due to the behaviour of a retrogressive rotational landslide, it would be more preferable to consider slope information as a predetermined cross-section angle from the base of the slope. This paper presents a new method using shadow casting algorithms for preliminary landslide susceptibility mapping in cohesive soils. A case study from western Sweden is also presented.
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| 9. |
- Lindberg, Fredrik, 1974, et al.
(författare)
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Nature of vegetation and building morphology characteristics across a city: Influence on shadow patterns and mean radiant temperatures in London
- 2011
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Ingår i: Urban Ecosystems. - : Springer Science and Business Media LLC. - 1083-8155 .- 1573-1642. ; 14:4, s. 617-634
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Tidskriftsartikel (refereegranskat)abstract
- Vegetation and building morphology characteristics are investigated at 19 sites on a north-south LiDAR transect across the megacity of London. Local maxima of mean building height and building plan area density at the city centre are evident. Surprisingly, the mean vegetation height (zv3) is also found to be highest in the city centre. From the LiDAR data various morphological parameters are derived as well as shadow patterns. Continuous images of the effects of buildings and of buildings plus vegetation on sky view factor (SVF) are derived. A general reduction of SVF is found, indicating the importance of including vegetation when deriving SVF in urban areas. The contribution of vegetation to the shadowing at ground level is higher during summer than in autumn. Using these 3D data the influence on urban climate and mean radiant temperature (Tmrt) is calculated with SOLWEIG. The results from these simulations highlight that vegetation can be most effective at reducing heat stress within dense urban environments in summer. The daytime average Tmrt is found to be lowest in the densest urban environments due to shadowing, foremost from buildings but also from trees. It is clearly shown that this method could be used to quantify the influence of vegetation on Tmrt within the urban environment. The results presented in this paper highlight a number of possible climate sensitive planning practices for urban areas at the local scale (i.e. 102- 5×10^3 m).
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| 10. |
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