| 1. |
- 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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| 2. |
- 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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| 3. |
- Lindberg, Fredrik, 1974, et al.
(författare)
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Träden i staden – Användningen av LiDAR-data för att identifiera urban vegetation
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Detaljerad kartläggning av urban vegetation är en viktig förutsättning för att värdera ekosystemtjänster i städer. Dock saknas som regel detaljerad information om vegetationsom faller utanför stadens detaljplanering och markanvändningskartor, speciellt gäller detta vegetationens tredimensionella egenskaper. I denna studie har två olika LiDARdatasetanvänts för att kartlägga den urbana vegetationen med avseende på dessutbredning och tredimensionella egenskaper (vegetationshöjd, stamzonhöjd och krönhöjd): (1) nationella Lantmäteriet (LM) och (2) från Göteborg stads stadsbyggnadskontor (SBK). Dataseten skiljer sig åt, främst i fråga om punkttäthet, klassificering och årstid för insamling, vilket innebär olika förutsättningar för vegetationskartering. I rapporten redovisas skillnader mellan dataseten och hur dessa skillnader påverkar kartläggningen av vegetation i urban miljö. Resultaten jämfördes medfältobservationer. Fyra områden (1x1 km) i Göteborg användes som fallstudie. Resultaten visar att vegetationens utbredning och höjd kan uppskattas bra med LiDARdata i urbana miljöer om punkttätheten är hög och klassificeringen medger bra separeringav returer. SBK-data uppfyller båda dessa kriterier. Den lägre punkttätheten och den grövre klassificeringen av LM-data medför att mycket vegetation utelämnas samt attoönskade objekt i större grad inkluderas i analysen. Beräknad vegetationshöjd korrelerar väl med fältobservationer, vilket gäller båda dataseten. Kronhöjd visar något sämrekorrelation på grund av stor osäkerhet i beräkning av stamzonhöjd. Filtrering av preliminära vegetationsraster har genomförts vilket löser en del problem med oönskade objekt och artefakter som härrör från rumsliga variationer i punktmolnets täthet. Filtreringinnebär dock manipulation av data och är därför också en osäkerhetsfaktor. LM-data kräver mer filtrering, framför allt måste celler med låga värden (
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| 4. |
- Lindberg, Fredrik, 1974, et al.
(författare)
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Träden i staden – Användningen av LiDAR-data för att identifiera urban vegetation
- 2013
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Detaljerad kartläggning av urban vegetation är en viktig förutsättning för att värdera ekosystemtjänster i städer. Dock saknas som regel detaljerad information om vegetation som faller utanför stadens detaljplanering och markanvändningskartor, speciellt gäller detta vegetationens tredimensionella egenskaper. I denna studie har två olika LiDARdataset använts för att kartlägga den urbana vegetationen med avseende på dess utbredning och tredimensionella egenskaper (vegetationshöjd, stamzonhöjd och krönhöjd): (1) nationella Lantmäteriet (LM) och (2) från Göteborg stads stadsbyggnadskontor (SBK). Dataseten skiljer sig åt, främst i fråga om punkttäthet, klassificering och årstid för insamling, vilket innebär olika förutsättningar för vegetationskartering. I rapporten redovisas skillnader mellan dataseten och hur dessa skillnader påverkar kartläggningen av vegetation i urban miljö. Resultaten jämfördes med fältobservationer. Fyra områden (1x1 km) i Göteborg användes som fallstudie. Resultaten visar att vegetationens utbredning och höjd kan uppskattas bra med LiDARdata i urbana miljöer om punkttätheten är hög och klassificeringen medger bra separering av returer. SBK-data uppfyller båda dessa kriterier. Den lägre punkttätheten och den grövre klassificeringen av LM-data medför att mycket vegetation utelämnas samt att oönskade objekt i större grad inkluderas i analysen. Beräknad vegetationshöjd korrelerar väl med fältobservationer, vilket gäller båda dataseten. Kronhöjd visar något sämre korrelation på grund av stor osäkerhet i beräkning av stamzonhöjd. Filtrering av preliminära vegetationsraster har genomförts vilket löser en del problem med oönskade objekt och artefakter som härrör från rumsliga variationer i punktmolnets täthet. Filtrering innebär dock manipulation av data och är därför också en osäkerhetsfaktor. LM-data kräver mer filtrering, framför allt måste celler med låga värden (< 2m) avlägsnas för att ta bort oönskade objekt, till exempel bilar. Den lägre upplösningen i LM-data gör också att filtreringen blir mer oprecis.
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| 5. |
- Thorsson, Sofia, 1972, et al.
(författare)
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Adapting cities to climate induced risks - a coordinated approach
- 2011
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Ingår i: Climate and Construction. ; , s. 173-180
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Konferensbidrag (refereegranskat)abstract
- In an era of changing climate there is a growing interest to create resilient cities, which can absorb and manage climate induce risks, such as heat waves and natural hazards (flooding, landslides etc). The increased frequencies and magnitudes of these climate hazards are expected to have a major impact on society. In order to maintain risks to society at acceptable levels, measures to reduce the vulnerability need to be taken. Such measures may, however, have significant non-expected and non-wanted impacts elsewhere on society. The need of holistic planning strategies becomes apparent. The overall aim of this new transdisciplinary research project is to develop knowledge and methods that enable an integrated assessment of the impact of climate induced risks on society. The free-port area in Gothenburg, Sweden, will has been selected for a case study that will sharpen both the individual scientific methods and the interdisciplinary and intersectoral cooperation and integration. The project brings together experts in urban climate, atmospheric science, natural risk assessment, stratified vulnerability and multi-criteria analyses with local city planners in an integrated research effort. Strategic plans for climate adaptation will be developed and proposed. The stakeholder involvement will promote transfer of knowledge and applicability of results.
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| 6. |
- Bocker, L., et al.
(författare)
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Integrated Weather Effects on Cycling Shares, Frequencies, and Durations in Rotterdam, the Netherlands
- 2014
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Ingår i: Weather Climate and Society. - : American Meteorological Society. - 1948-8327 .- 1948-8335. ; 6:4, s. 468-481
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Tidskriftsartikel (refereegranskat)abstract
- With the increasing societal interest in climate change, health, accessibility, and liveability and subsequent policy aims to promote active transport modes over car usage, many scholars have investigated the relationship between weather and cycling. Existing studies, however, hardly address the effects of weather on cycling durations and often lack assessments of the combined effects of different meteorological variables and potential nonlinearity of these effects. Drawing on travel diary data from a panel study of 945 Greater Rotterdam respondents (the Netherlands), this paper investigates and compares the effects of different meteorological variables, singly as well as combined, on cycling frequencies, cycling durations, and the exchange between cycling and other transport modes. Results show linear negative effects of precipitation sum and wind speed and nonlinear bell-shaped effects of thermal variables on cycling and opposite effects on car usage. Out of three thermal variables investigated, mean radiant temperature (radiant heat exchange between humans and the environment) and physiological equivalent temperature (an index combining the effects of air temperature, mean radiant temperature, air humidity, and wind speed) better explain cycling behavior than just air temperature. Optimum thermal conditions for cycling were found on days with maximum air temperatures around 24 degrees C, mean radiant temperatures around 52 degrees C, and physiological equivalent temperatures around 30 degrees C. Policy and planning implications are highlighted that could reduce cyclists' exposures to disadvantageous weather conditions such as heat, precipitation, and wind, at present and in a potentially changing climate.
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| 7. |
- Holmer, Björn, 1943, et al.
(författare)
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Evening evapotranspirative cooling in relation to vegetation and urban geometry in the city of Ouagadougou, Burkina Faso
- 2013
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418. ; 33:15, s. 3089-3105
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Tidskriftsartikel (refereegranskat)abstract
- Intra-urban cooling in the city of Ouagadougou, capital of Burkina Faso in the Sahel zone of West Africa, was studied during the dry seasons in 2003, 2004 and 2007. The aim was to see how vegetation, built structure and position within the built-up area influenced the nocturnal cooling. Cooling was divided into two phases. In Phase 1 (16:00 -20:00 hours LST = CET), cooling was very different between the sites while in Phase 2 (20:00 -06:00 hours LST), cooling rates differed insignificantly and the whole area cooled almost at the same rate. Thus the temperature differences between the sites developed during these few hours in Phase 1 were preserved during the rest of the night. In Phase 1, Evening Evapotranspirative Cooling was intensive at vegetated sites that cooled almost twice as fast as sparsely vegetated. This was indicated by a humidity rate (increase of specific humidity per hour) that was high at a vegetated site, but considerably lower at a sparsely vegetated. In Phase 2 the humidity rate was slightly negative with little difference between the sites. After a division in vegetated and sparsely vegetated sites built structure (sky view factor) were shown to influence cooling, but no influence of the position within the built-up area was traced. Thus, the site-specific properties dominated cooling, giving large intra-urban temperature differences. The study also showed the importance of considering a large enough source area to account for micro-scale advection.
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| 8. |
- Johansson, Erik, et al.
(författare)
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Instruments and methods in outdoor thermal comfort studies - The need for standardization
- 2014
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Ingår i: Urban Climate. - : Elsevier BV. - 2212-0955. ; 10:part 2, s. 346-366
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we review instruments and methods used to assess outdoor thermal comfort and subjective thermal perception in 26 studies reported in the literature during the last decade, covering a wide range of climates and geographical contexts. We found a great variety of instruments and methods used to measure meteorological variables, especially with respect to the mean radiant temperature and wind speed. Moreover, many different subjective judgement scales were used to assess subjective thermal perception, thermal neutrality and thermal preference and a multitude of thermal indices were used to quantify the combined effect of meteorological variables on thermal perception. The use of a variety of methods makes it difficult to compare results of the different studies. There is thus a need for standardization and to give guidance regarding how to conduct field surveys in outdoor environments. Such standards and guidelines should give advice regarding the choice of measurement sites, type and positioning of instruments, appropriate methods to determine the mean radiant temperature, questionnaire design and suitable thermal comfort indices. These guidelines should also include advice on reporting. © 2013 Elsevier Ltd. All rights reserved.
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| 9. |
- Knez, Igor, et al.
(författare)
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Climate Change : Concerns, Beliefs and Emotions in Residents, Experts, Decision Makers, Tourists, and Tourist Industry
- 2013
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Ingår i: American Journal of Climate Change. - : Scientific Research Publishing, Inc.. - 2167-9495 .- 2167-9509. ; 2:4, s. 254-269
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to investigate effects of different groups of individuals (residents, tourists, experts, decision makers and members of tourist industry) and demographic variables (gender, age, education) on climate change-related concerns, beliefs and emotions. In line with the predictions: 1) Experts were shown to be least concerned for and afraid of climate change impact; 2) Youngest participants were found to be most, and oldest least, concerned for their future; 3) Women were shown to be more concerned for and afraid of the consequences of climate change; and 4) Men and the least educated participants believed their jobs to be more threatened by the environmental laws and protection, and the latter ones believed moreover that the claims about climate change are exaggerated. Implications of these findings for value orientations and their relationships to environmental concerns, beliefs and emotions are discussed.
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| 10. |
- 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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