SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Lindberg Fredrik 1974) "

Sökning: WFRF:(Lindberg Fredrik 1974)

  • Resultat 1-50 av 110
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Andersson-Sköld, Yvonne, et al. (författare)
  • A framework for assessing urban greenery's effects and valuing its ecosystem services
  • 2018
  • Ingår i: Journal of Environmental Management. - : Academic Press. - 0301-4797 .- 1095-8630. ; 205, s. 274-285
  • Tidskriftsartikel (refereegranskat)abstract
    • Ongoing urban exploitation is increasing pressure to transform urban green spaces, while there is increasing awareness that greenery provides a range of important benefits to city residents. In efforts to help resolve associated problems we have developed a framework for integrated assessments of ecosystem service (ES) benefits and values provided by urban greenery, based on the ecosystem service cascade model. The aim is to provide a method for assessing the contribution to, and valuing, multiple ES provided by urban greenery that can be readily applied in routine planning processes. The framework is unique as it recognizes that an urban greenery comprises several components and functions that can contribute to multiple ecosystem services in one or more ways via different functional traits (e.g. foliage characteristics) for which readily measured indicators have been identified. The framework consists of five steps including compilation of an inventory of indicator; application of effectivity factors to rate indicators' effectiveness; estimation of effects; estimation of benefits for each ES; estimation of the total ES value of the ecosystem. The framework was applied to assess ecosystem services provided by trees, shrubs, herbs, birds, and bees, in green areas spanning an urban gradient in Gothenburg, Sweden. Estimates of perceived values of ecosystem services were obtained from interviews with the public and workshop activities with civil servants. The framework is systematic and transparent at all stages and appears to have potential utility in the existing spatial planning processes.
  •  
2.
  • Hu, Yumei, et al. (författare)
  • The use of screening effects in modelling route-based daytime road surface temperature
  • 2016
  • Ingår i: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 125:1, s. 303-319
  • Tidskriftsartikel (refereegranskat)abstract
    • © 2015 The Author(s) Winter road maintenance is essential for road safety. Accurate predictions of the road surface temperature (RST) and conditions can enhance the efficiency of winter road maintenance. Screening effects, which encompass shading effects and the influence of the sky-view factor (ψs), influence RST distributions because they affect road surface radiation fluxes. In this work, light detection and ranging (Lidar) data are used to derive shadow patterns and ψs values, and the resulting shadow patterns are used to model route-based RST distributions along two stretches of road in Sweden. The shading patterns and road surface radiation fluxes calculated from the Lidar data generally agreed well with measured RST values. Variation in land use types and the angle between the road direction and solar azimuth may introduce uncertainties, and accounting for these factors may improve the results obtained in certain cases. A simple shading model that only accounts for the direct radiation at the instant of measurement is often sufficient to provide reasonably accurate RST estimates. However, in certain cases, such as those involving measurements close to sunset, it is important to consider the radiation accumulated over several hours. The inclusion of ψs improves the model performance even more in such cases. Overall, RST models based on the accumulated direct shortwave radiation offered an optimal balance of simplicity and accuracy. General radiation models were built for country road and highway environments, explaining up to 70 and 65 %, respectively, of the observed variation in RST along the corresponding stretches of road.
  •  
3.
  • Aminipouri, M., et al. (författare)
  • Urban tree planting to maintain outdoor thermal comfort under climate change: The case of Vancouver's local climate zones
  • 2019
  • Ingår i: Building and Environment. - : Elsevier BV. - 0360-1323. ; 158, s. 226-236
  • Tidskriftsartikel (refereegranskat)abstract
    • Spatiotemporal variation of mean radiant temperature (Tmrt), a major driver of outdoor human thermal comfort, is driven by exposure to solar and longwave radiation, which in turn respond to local patterns of shading, wind speed, air humidity and air temperature. In this study, the SOlar and LongWave Environmental Irradiance Geometry (SOLWEIG) model was used to simulate how changes in minimum and maximum air temperature and solar radiation under Representative Concentration Pathways (RCP) 4.5 and 8.5 climate projections would change Tmrt in Vancouver over the 2070-2100 period. With micrometeorological variables representative of a changed climate, days with Tmrt above 65 degrees C were predicted to increase three-to five-fold under RCP 4.5 and 8.5, respectively. SOLWEIG was also used to quantify the potential of maximum feasible street tree cover to reduce Tmrt for the hottest day on record for Vancouver (July 29, 2009), and an end-of-century hot day under the two future climate scenarios. SOLWEIG simulations with maximum feasible street tree cover under RCP 4.5 demonstrated an average reduction of 1.3 degrees C in Tmrt, compared to the contemporary extreme heat day with current street trees. However, average Tmrt increased by 1.9 degrees C under the RCP 8.5 scenario even with maximum feasible street tree cover, relative to the contemporary extreme heat day. We conclude that adding street trees has the potential to offset Tmrt increases under the RCP 4.5 scenario, however this measure is insufficient to maintain contemporary Tmrt under the RCP 8.5 scenario.
  •  
4.
  • Andersson-Sköld, Yvonne, et al. (författare)
  • An integrated method for assessing climate-related risks and adaptation alternatives in urban areas
  • 2015
  • Ingår i: Climate Risk Management. - : Elsevier BV. - 2212-0963. ; 7, s. 31-50
  • Tidskriftsartikel (refereegranskat)abstract
    • © 2015 The Authors. The urban environment is a complex structure with interlinked social, ecological and technical structures. Global warming is expected to have a broad variety of impacts, which will add to the complexity. Climate changes will force adaptation, to reduce climate-related risks. Adaptation measures can address one aspect at the time, or aim for a holistic approach to avoid maladaptation. This paper presents a systematic, integrated approach for assessing alternatives for reducing the risks of heat waves, flooding and air pollution in urban settings, with the aim of reducing the risk of maladaptation. The study includes strategies covering different spatial scales, and both the current climate situation and the climate predicted under climate change scenarios. The adaptation strategies investigated included increasing vegetation; selecting density, height and colour of buildings; and retreat or resist (defend) against sea-level rise. Their effectiveness was assessed with regard to not only flooding, heat stress and air quality but also with regard to resource use, emissions to air (incl. GHG), soil and water, and people's perceptions and vulnerability. The effectiveness of the strategies were ranked on a common scale (from -3 to 3) in an integrated assessment. Integrated assessments are recommended, as they help identify the most sustainable solutions, but to reduce the risk of maladaptation they require experts from a variety of disciplines. The most generally applicable recommendation, derived from the integrated assessment here, taking into account both expertise from different municipal departments, literature surveys, life cycle assessments and publics perceptions, is to increase the urban greenery, as it contributes to several positive aspects such as heat stress mitigation, air quality improvement, effective storm-water and flood-risk management, and it has several positive social impacts. The most favourable alternative was compact, mid-rise, light coloured building design with large parks/green areas and trees near buildings.
  •  
5.
  • Bernard, Jérémy, 1989, et al. (författare)
  • URock 2023a: an open-source GIS-based wind model for complex urban settings
  • 2023
  • Ingår i: Geoscientific Model Development. - 1991-959X .- 1991-9603. ; 16:20, s. 5703-5727
  • Tidskriftsartikel (refereegranskat)abstract
    • URock 2023a is an open-source diagnostic model dedicated to wind field calculation in urban settings. It is based on a quick method initially proposed by and already implemented in the proprietary software QUIC-URB. First, the model method is described as well as its implementation in the free and open-source geographic information system called QGIS. Then it is evaluated against wind tunnel measurements and QUIC-URB simulations for four different building layouts plus one case with an isolated tree. The correlation between URock and QUIC-URB is high, and URock reproduces the spatial variation of the wind speed observed in the wind tunnel experiments quite well, even in complex settings. However, sources of improvements, which are applicable for both URock and QUIC-URB, are highlighted. URock and QUIC-URB overestimate the wind speed downstream of the upwind edges of wide buildings and also downstream of isolated tree crowns. URock 2023a is available via the Urban Multiscale Environment Predictor (UMEP), a city-based climate service tool designed for researchers and service providers presented as a plug-in for QGIS. The model, data, and scripts used to write this paper can be freely accessed at 10.5281/zenodo.7681245 .
  •  
6.
  • Bäcklin, Oskar, 1991, et al. (författare)
  • Outdoor heat stress at preschools during an extreme summer in Gothenburg, Sweden - Preschool teachers’ experiences contextualized by radiation modelling
  • 2021
  • Ingår i: Sustainable Cities and Society. - : Elsevier BV. - 2210-6707. ; 75
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a mixed-method approach consisting of interviews with preschool teachers and modelling of the outdoor thermal conditions using the mean radiant temperature as an indicator of heat stress, the occurrence of heat stress in Gothenburg preschools during the summer of 2018 and its effects have been studied. One third of 440 preschool yards modelled have more than 50% of the preschool yard-area exposed to strong heat stress during a warm and sunny summer day, implying children in many preschools have considerably less play area than current guidelines deem sufficient. Shade, where present, was mostly from trees within the preschool yards themselves rather from objects in surrounding areas, provided effective heat mitigation. Interviews confirmed that excessive heat conditions at preschool yards resulted in tired, drowsy and overheated children as well as forcing the preschool to prioritise care over pedagogical activities. The results demonstrated that heat stress occurs at Gothenburg preschools, with difficulties in ensuring the well-being of children at many preschools as a consequence. Many preschools need more shade, preferably from trees to provide healthy and secure environments for preschool children. Finally, the study highlights the need for more research on how weather and outdoor environments affect children's activity and well-being.
  •  
7.
  • Bäcklin, Oskar, 1991, et al. (författare)
  • Outdoor heat stress at preschools during an extreme summer in Gothenburg, Sweden - Preschool teachers’ experiences contextualized by radiation modelling
  • 2022
  • Ingår i: Multiple Nordic Geographies 9th Nordic Geographers Meeting 19th - 22nd of June 2022 Joensuu, Finland.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • With increasing urbanisation and climate change, heat stress issues are becoming increasingly important to consider in order to create sustainable urban environments worldwide. Heat affects all groups in society, although small children are especially vulnerable due to physiological factors as well as limitations in their everyday mobility. Therefore, it is crucial to ensure that outdoor areas used by children, such as preschools provide healthy safe thermal conditions. Trees are proven effective heat mitigating objects, as well as highly appreciated features of preschool yards for their aesthetic and pedagogical aspects. However, there is a large variation in the amount of trees at preschool yards which can prove to be problematic regarding thermal comfort and well-being for both children and preschool teachers today and in the future. Using a mixed-method approach consisting of 19 interviews with preschool teachers, and modelling outdoor thermal conditions on 440 preschool yards, the occurrence of heat stress in Gothenburg preschools during the heat wave of 2018 and its effects on preschools has been studied. One third of modelled preschool yards were found to have more than 50% of the preschool yard area exposed to strong heat stress during a warm and sunny summer days, implying children in many preschools have significantly less play area than current guidelines deem sufficient. Shading, which was found mainly provided by trees within preschool yards rather than from objects in surrounding areas, provide effective heat mitigation. Shading devices such as shade-sails were found prone to breakage and not providing sufficient shading. Thus, shading devices are not suggested as a long-term solution for heat mitigation at preschool yards. Interviews confirmed that excessive heat conditions at preschool yards cause tired, drowsy and overheated children as well as forcing the preschool to prioritise care over pedagogical activities. The results demonstrated that heat stress is a problem at many Gothenburg preschools, with difficulties in ensuring the well-being of children at many preschools as a consequence. The strong correlation found between amount of trees at preschool yards and less heat stress highlight the importance of trees for heat mitigation.
  •  
8.
  • Carlström, Eric, 1957, et al. (författare)
  • Medical Emergencies During a Half Marathon Race - The Influence of Weather
  • 2019
  • Ingår i: International Journal of Sports Medicine. - Stuttgart : Georg Thieme Verlag KG. - 0172-4622 .- 1439-3964. ; 40:5, s. 312-316
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim was to analyze the influence of weather conditions on medical emergencies in a half-marathon, specifically by evaluating its relation to the number of non-finishers, ambulance-required assistances, and collapses in need of ambulance as well as looking at the location of such emergencies on the race course. Seven years of data from the world's largest half marathon were used. Meteorological data were obtained from a nearby weather station, and the Physiological Equivalent Temperature (PET) index was used as a measure of general weather conditions. Of the 315,919 race starters, 104 runners out of the 140 ambulance-required assistances needed ambulance services due to collapses. Maximum air temperature and PET significantly co-variated with ambulance-required assistances, collapses, and non-finishers (R (2) =0.65-0.92; p=0.001-0.03). When air temperatures vary between 15-29 degrees C, an increase of 1 degrees C results in an increase of 2.5 (0.008/1000) ambulance-required assistances, 2.5 (0.008/1000) collapses (needing ambulance services), and 107 (0.34/1000) non-finishers. The results also indicate that when the daily maximum PET varies between 18-35 degrees C, an increase of 1 degrees C PET results in an increase of 1.8 collapses (0.006/1000) needing ambulance services and 66 non-finishers (0.21/1000).
  •  
9.
  •  
10.
  • Chrysoulakis, N, et al. (författare)
  • 7E.3: Urban Energy Balance from Space: the URBANFLUXES Project
  • 2018
  • Ingår i: 10th International Conference on Urban Climate/14th Symposium on the Urban Environment, New York, US, August 2018.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The H2020-Space project URBANFLUXES investigated the potential of Copernicus Sentinels to retrieve the key components of the Urban Energy Budget (UEB). The Discrete Anisotropic Radiative Transfer (DART) model was used to estimate the net all-wave radiation fluxes. The storage heat flux was determined using the Element Surface Temperature Method (ESTM) after being modified to use satellite observations. Turbulent sensible and latent heat fluxes were estimated with the Aerodynamic Resistance Method (ARM). The fluxes were evaluated with in-situ flux measurements in London, Basel and Heraklion. URBANFLUXES prepared the ground for further innovative exploitation of Earth Observation data in climate variability studies scales and emerging applications (sustainable urban planning, mitigation technologies) to benefit climate change mitigation and adaptation. The wide range of data produced (e.g. land cover, vegetation phenology, surface morphology) have a much large possible applications. This project website (http://urbanfluxes.eu) provides more detailed information.
  •  
11.
  • Chrysoulakis, Nektarios, et al. (författare)
  • A novel approach for anthropogenic heat flux estimation from space
  • 2016
  • Ingår i: IGARSS 2016 - IEEE International Geoscience and Remote Sensing Symposium. 10-15 July 2016. Beijing; China. - : IEEE. - 2153-7003. - 9781509033324
  • Konferensbidrag (refereegranskat)abstract
    • The recently launched H2020 project URBANFLUXES (URBan ANthrpogenic heat FLUX from Earth observation Satellites) investigates the potential of EO to retrieve anthropogenic heat flux, as a key component in the Urban Energy Budget (UEB). URBANFLUXES advances existing Earth Observation (EO) based methods for estimating spatial patterns of turbulent sensible and latent heat fluxes, as well as urban heat storage flux at city scale and local scale. Independent methods and models are engaged to evaluate the derived products and statistical analyses provide uncertainty measures. Optical, thermal and SAR data are exploited to improve the accuracy of the UEB components spatial distribution calculation. Synergistic use of different types and of various resolution EO data allows estimates in local and city scale. Ultimate goal of the URBANFLUXES is to develop a highly automated method for estimating UEB components to use with Copernicus Sentinel data, enabling its integration into applications and operational services.
  •  
12.
  • Chrysoulakis, Nektarios, et al. (författare)
  • A novel approach for anthropogenic heat flux estimation from space
  • 2015
  • Ingår i: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July 2015, Toulouse, France.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • How people live, work, move from place to place, what they consume and the technology they use, all affect the fabric, morphology and emissions in a city and in turn its climate. To understand the relations between urban form, energy use and carbon emissions an important challenge is to disaggregate urban areas into different spatial units and evaluate their impacts on energy fluxes and greenhouse gas emissions. There is a need in Earth system science communities for spatially disaggregated anthropogenic heat data, at local and city scales. The anthropogenic heat flux is the heat flux resulting from vehicular emissions, space heating and cooling of buildings, industrial processing and the metabolic heat release by people. Such information is practically impossible to derive by point in-situ flux measurements, while satellite remote sensing has proven a valuable tool for estimating energy budget parameters exploiting Earth Observation (EO) data. While EO data are widely used for urban studies, their main application area is limited to land cover mapping and similar applications. Nevertheless, currently available EO data and forthcoming satellite systems can considerably contribute to the study of urban climate. To this aim the recently launched H2020 project URBANFLUXES (URBan ANthrpogenic heat FLUX from Earth observation Satellites) investigates the potential of EO to retrieve anthropogenic heat flux, as a key component in the urban energy budget. The urban energy budget is considered in the context of a volume because of the three dimensional nature of the city, and includes the fluxes into, or out of, or the storage change within the control volume. URBANFLUXES advances existing EO-based methods for estimating spatial patterns of turbulent sensible and latent heat fluxes, as well as urban heat storage flux at city scale and local scale. Independent methods and models are engaged to evaluate the derived products and statistical analyses provide uncertainty measures. Optical, thermal and SAR data from existing satellite sensors are exploited to improve the accuracy of the energy budget components spatial distribution calculation. Synergistic use of different types and of various resolution EO data allows estimates in local and city scale. In-situ reflectance measurements of urban materials for calibration. The URBANFLUXES project prepares the ground for further innovative exploitation of EO data in scientific activities involving Earth system modelling and climate change studies in cities. The URBANFLUXES products will support system models to provide more robust climate simulations. Ultimate goal of the URBANFLUXES is to develop a highly automated method for estimating urban energy budget components to use with Copernicus Sentinel data, enabling its integration into applications and operational services. The improved data quality, spatial coverage and revisit times of the Copernicus data will allow support of future emerging applications regarding sustainable urban planning, with the objective of improving the quality of life in cities.
  •  
13.
  •  
14.
  • Chrysoulakis, Nektarios, et al. (författare)
  • Anthropogenic Heat Flux Estimation from Space: The URBANFLUXES Project
  • 2016
  • Ingår i: AMS 22nd Symposium on Boundary Layers and Turbulence, 20 – 24 June, 2016, Salt Lake City, USA..
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The H2020 project URBANFLUXES (URBan ANthrpogenic heat FLUX from Earth observation Satellites) investigates the potential of Copernicus Sentinels to retrieve anthropogenic heat flux, as a key component of the Urban Energy Budget (UEB). Temperatures in cities are predicted to rise even more in the future, resulting in increased energy demand for cooling systems in low and mid-latitude cities, modifying UEB. A positive feedback cycle occurs in many urban areas, where higher temperatures result in more energy being used for cooling, which in turn adds to heat emissions and increases temperatures further during periods with increased heat wave risk. It is expected that without mitigation measures, energy demand will continue to increase during the warmest months. URBANFLUXES advances the current knowledge of the impacts of UEB fluxes on urban heat island and consequently on energy consumption in cities. This will lead to the development of tools and strategies to mitigate these effects, improving thermal comfort and energy efficiency. In URBANFLUXES, the anthropogenic heat flux is estimated as a residual of UEB. Therefore, the rest UEB components, namely, the net all-wave radiation, the net change in heat storage and the turbulent sensible and latent heat fluxes are independently estimated from Earth Observation (EO), whereas the advection term is included in the error of the anthropogenic heat flux estimation from the UEB closure. A dense network of conventional meteorological stations is used in each case study city: London, Basel and Heraklion. EO data is initially analyzed to map urban surface morphology and cover, whilst a new approach has been developed to define appropriate zones for energy partitioning. Using these zones as a framework, advanced EO-based methods are used to estimate UEB fluxes: a sophisticated radiative transfer model (Discrete Anisotropic Radiative Transfer) was employed to simulate the net all-wave radiation; the computation of the storage term was based on the Element Surface Temperature Method, supported by the auxiliary datasets; and the estimation of the turbulent heat fluxes was based on the Aerodynamic Resistance Method, supported by standard meteorological measurements. In-situ flux measurements (Eddy Covariance, scintillometry) and bottom-up approaches (inventories, building energy models) were used to evaluate URBANFLUXES outcomes, whereas uncertainties were specified and analyzed. The project exploits Sentinels observations, which provide improved data quality, coverage and revisit times and increase the value of EO data for scientific work and future emerging applications. These observations can reveal novel scientific insights for the detection and monitoring of the spatial distribution of the urban energy budget fluxes in cities, thereby generating new EO opportunities. URBANFLUXES thus exploits the European capacity for space-borne observations to enable the development of operational services in the field of urban environmental monitoring and energy efficiency in cities. It is therefore expected to prepare the ground for further innovative exploitation of European space data in scientific activities (climate variability studies at local and regional scales) and future and emerging applications (sustainable urban planning, mitigation technologies) to benefit climate change mitigation/adaptation and civil protection. More information on the project can be found at http://urbanfluxes.eu.
  •  
15.
  • Chrysoulakis, N., et al. (författare)
  • Urban energy exchanges monitoring from space
  • 2018
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • One important challenge facing the urbanization and global environmental change community is to understand the relation between urban form, energy use and carbon emissions. Missing from the current literature are scientific assessments that evaluate the impacts of different urban spatial units on energy fluxes; yet, this type of analysis is needed by urban planners, who recognize that local scale zoning affects energy consumption and local climate. Satellite-based estimation of urban energy fluxes at neighbourhood scale is still a challenge. Here we show the potential of the current satellite missions to retrieve urban energy budget fluxes, supported by meteorological observations and evaluated by direct flux measurements. We found an agreement within 5% between satellite and in-situ derived net all-wave radiation; and identified that wall facet fraction and urban materials type are the most important parameters for estimating heat storage of the urban canopy. The satellite approaches were found to underestimate measured turbulent heat fluxes, with sensible heat flux being most sensitive to surface temperature variation (-64.1, +69.3 W m(-2) for +/- 2 K perturbation). They also underestimate anthropogenic heat fluxes. However, reasonable spatial patterns are obtained for the latter allowing hot-spots to be identified, therefore supporting both urban planning and urban climate modelling.
  •  
16.
  • Eliasson, Ingegärd, 1961, et al. (författare)
  • Climate and behaviour in a Nordic city
  • 2007
  • Ingår i: LANDSCAPE AND URBAN PLANNING. - : Elsevier BV. - 0169-2046 .- 1872-6062. ; 82:1-2, s. 72-84
  • Tidskriftsartikel (refereegranskat)abstract
    • Four urban public spaces, representing various designs and microclimates, were investigated in Gothenburg, Sweden, in order to estimate how weather and microclimate affect people in urban outdoor environments. The research strategy was both multidisciplinary and interdisciplinary and included scientists from three disciplines: architecture, climatology and psychology. The project is based on common case studies carried out during four seasons, including measurements of meteorological variables, interviews and observations of human activity at each place. Multiple regression analysis of meteorological and behavioural data showed that air temperature, wind speed and clearness index (cloud cover) have a significant influence on people's assessments of the weather, place perceptions and place-related attendance. The results support the arguments in favour of employing climate sensitive planning in future urban design and planning projects, as the physical component of a place can be designed to influence the site-specific microclimate and consequently people's place-related attendance, perceptions and emotions.
  •  
17.
  • Feigenwinter, Christian, et al. (författare)
  • Spatial Distribution of Sensible and Latent Heat Flux in the City of Basel (Switzerland)
  • 2018
  • Ingår i: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. - 1939-1404 .- 2151-1535. ; 11:8 (S1), s. 2717-2723
  • Tidskriftsartikel (refereegranskat)abstract
    • IEEE Urban surfaces are a complex mixture of different land covers and surface materials; the relative magnitudes of the surface energy balance components therefore vary widely across a city. Eddy covariance (EC) measurements provide the best estimates of turbulent heat fluxes but are restricted to the source area. Land surface modeling with earth observation (EO) data is beneficial for extrapolation of a larger area since citywide information is possible. Turbulent sensible and latent heat fluxes are calculated by a combination of micrometeorological approaches (the aerodynamic resistance method, ARM), EO data, and GIS techniques. Input data such as land cover fractions and surface temperatures are derived from Landsat 8 OLI and TIRS, urban morphology was calculated from high-resolution digital building models and GIS data layers, and meteorological data were provided by flux tower measurements. Twenty-two Landsat scenes covering all seasons and different meteorological conditions were analyzed. Sensible heat fluxes were highest for industrial areas, railway stations, and areas with high building density, mainly corresponding to the pixels with highest surface-to-air temperature differences. The spatial distribution of latent heat flux is strongly related to the saturation deficit of vapor and the (minimum) stomatal resistance of vegetation types. Seasonal variations are highly dependent on meteorological conditions, i.e., air temperature, water vapor saturation deficit, and wind speed. Comparison of measured fluxes with modeled fluxes in the weighted source area of the flux towers is moderately accurate due to known drawbacks in the modeling approach and uncertainties inherent to EC measurements, particularly in urban areas.
  •  
18.
  • Feigenwinter, Christian, et al. (författare)
  • Spatial distribution of sensible and latent heat flux in the URBANFLUXES case study city Basel (Switzerland)
  • 2017
  • Ingår i: 2017 Joint Urban Remote Sensing Event (JURSE). Dubai; United Arab Emirates; 6-8 March 2017. - 9781509058099
  • Konferensbidrag (refereegranskat)abstract
    • Turbulent sensible and latent heat fluxes are calculated by a combined method using micrometeorological approaches (the Aerodynamic Resistance Method ARM), Earth Observation (EO) data and GIS-Techniques. The spatial distributions of turbulent heat fluxes were analyzed for 22 for the city of Basel (Switzerland), covering all seasons and different meteorological conditions. Seasonal variations in heat fluxes are strongly dependent on meteorological conditions, i.e. air temperature, water vapor saturation deficit and wind speed. The agreement of measured fluxes (by the Eddy Covariance method) with modeled fluxes in the weighted source area of the flux towers is moderate due to known drawbacks in the modelling approach and uncertainties inherent to EC measurements, particularly also in urban areas.
  •  
19.
  • Franzén, Lars, 1950, et al. (författare)
  • The potential peatland extent and carbon sink in Sweden, as related to the Peatland / Ice Age Hypothesis
  • 2012
  • Ingår i: Mires and Peat. - 1819-754X. ; 10:artikel nr 08, s. 1-19
  • 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.
  •  
20.
  •  
21.
  •  
22.
  •  
23.
  •  
24.
  • Holmer, Björn, 1943, et al. (författare)
  • How to transform the standing man from a box to a cylinder – a modified methodology to calculate mean radiant temperature in field studies and models
  • 2015
  • Ingår i: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July, Toulouse, France.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Mean radiant temperature (Tmrt) has shown to be an important meteorological variable in studies of human comfort and health. The Tmrt is calculated as the surface temperature of a standing man approximated as a cylinder emitting the same amount of longwave radiation as all short- and longwave radiation fluxes received from the surrounding four cardinal points and down- and upwards. The calculation was introduced by Höppe in 1992 and has then been used both in models (e.g. SOLWEIG) and field studies. However, the formula by Höppe describes in fact a man shaped like a box and not a cylinder, which has resulted in some peculiar features noticed in studies of Tmrt such as a secondary daytime minimum and an influence of the orientation of the field equipment. A methodology to change the box man to a cylindrical man is proposed. It will remove the peculiarities that have been observed in earlier studies. The methodology is based on the partition of the observed shortwave fluxes in direct and diffuse radiation. The minimum shortwave radiation of the four cardinal points is used as diffuse radiation since it is monitored by a sensor that is not sunlit. By subtraction of this quantity the horizontal direct fluxes are obtained. Calculation of the resultant flux of the sunlit sensors and adjustment for solar angle gives the direct shortwave radiation. The surface of the standing man (as a cylinder) perpendicular to the direct radiation must be determined and the direct shortwave radiation received by the standing man can be calculated. Then the sum of the shortwave fluxes can be calculated. The diffuse and longwave fluxes can be calculated according to the Höppe formula since they differ little with direction. In the SOLWEIG model the direct shortwave radiation is used as an input. Thus the calculation according to the new methodology is easy to apply, only the solar position needs to be added. The new methodology is tested by model calculations with SOLWEIG and field studies in both high-latitude Gothenburg, Sweden and low-latitude Ouagadougou, Burkina Faso. The secondary minimum disappears. In Gothenburg at a site with SVF=0.95 the noon depression of Tmrt by the Höppe formula was about 2 °C and there was an overestimation of 1.5-1.7 °C two-three hours before and after noon.differences in summer. In Ouagadougou data from an open site (SVF=0.83) in the dry season the differences were slightly smaller. Sites with lower SVF and much reflected direct shortwave radiation differed less from the Tmrt obtained with the Höppe formula.
  •  
25.
  • Holmer, Björn, 1943, et al. (författare)
  • Urban climatic map studies in Sweden: Gothenburg
  • 2015
  • Ingår i: The Urban Climatic Map: A Methodology for Sustainable Urban Planning. - Milton Park : Taylor and Francis. ; , s. 324-342
  • Bokkapitel (refereegranskat)
  •  
26.
  • Johansson, Lars, 1972, et al. (författare)
  • Statistical modelling of pedestrian wind speed using high‐resolution digital surface models
  • 2012
  • Ingår i: The Eight International Conference on Urban Climates. ; :abstract 183
  • 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.
  •  
27.
  • Johansson, Lars, et al. (författare)
  • Towards the modelling of pedestrian wind speed using high-resolution digital surface models and statistical methods
  • 2016
  • Ingår i: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 124:1, s. 189-203
  • Tidskriftsartikel (refereegranskat)abstract
    • Wind is a complex phenomenon and a critical factor in assessing climatic conditions and pedestrian comfort within cities. To obtain spatial information on near-ground wind speed, 3D computational fluid dynamics (CFD) modelling is often used. This is a computationally intensive method which requires extensive computer resources and is time consuming. By using a simpler 2D method, larger areas can be processed and less time is required. This study attempts to model the relationship between near-ground wind speed and urban geometry using 2.5D raster data and variable selection methods. Such models can be implemented in a geographic information system (GIS) to assess the spatial distribution of wind speed at street level in complex urban environments at scales from neighbourhood to city. Wind speed data, 2 m above ground, is obtained from simulations by CFD modelling and used as a response variable. A number of derivatives calculated from high-resolution digital surface models (DSM) are used as potential predictors. A sequential variable selection algorithm followed by all-possible subset regression was used to select candidate models for further evaluation. The results show that the selected models explain general spatial wind speed pattern characteristics but the prediction errors are large, especially so in areas with high wind speeds. However, all selected models did explain 90 % of the wind speed variability (R2 ≈0.90). Predictors adding information on width and height ratio and alignment of street canyons with respect to wind direction are suggested for improving model performance. To assess the applicability of any derived model, the results of the CFD model should be thoroughly evaluated against field measurements.
  •  
28.
  • Jänicke, Britta, et al. (författare)
  • Towards a city-wide analysis of mean radiant temperature at high spatial resolution – An example from Berlin, Germany
  • 2015
  • Ingår i: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July 2015, Toulouse, France.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Heat stress is expected to increase in the future due to global climate change. Many epidemiological studies show the close link between elevated air temperature and increased morbidity and mortality, which are not restricted to subtropical and tropical regions but also common in cities at higher latitudes like Berlin (52.5° N). Heat-stress risks are particularly high in urban regions, since urban climate modifications of regional weather conditions tend to increase heat-stress hazards. In order to analyse heat-stress risks and hazards within a city, the mean radiant temperature is an important variable as it sums up long- and short-wave radiation that reaches the human body. Thus, the mean radiant temperature along with air temperature, atmospheric humidity and wind speed is used for the calculation of many biometeorological indices. In urban environments mean radiant temperature is highly variable due to the shadow patterns of objects. To calculate the mean radiant temperature, urban structures such as trees, bushes, courtyards, street canyons and buildings need to be parameterized or explicitly included. The former reduces the computation demand, but limits the possibility to derive planning measures to reduce heat stress. In addition, weather and climate influence the variability of the mean radiant temperature, because the atmospheric conditions are heterogeneous in large urban areas. Therefore, the aim of this study is to calculate the mean radiant temperature for the case of Berlin while considering both micro-scale urban structures and meso-scale atmospheric conditions. For the computation of the mean radiant temperature we apply a version of the SOLWEIG model (Lindberg et al. 2011) that is able to use gridded meteorological input data. Digital surface models of buildings and vegetation with a spatial resolution of 1m provide the height of the micro-scale urban structures. The Central Europe Refined analysis (CER) serves as input for meso-scale atmospheric conditions. We will discuss the resulting spatio-temporal pattern of the mean radiant temperature in view of the applied methodology as well as regarding actions to reduce heat stress.
  •  
29.
  • Jänicke, Britta, et al. (författare)
  • Towards city-wide, building-resolving analysis of mean radiant temperature
  • 2016
  • Ingår i: Urban Climate. - : Elsevier BV. - 2212-0955. ; 15, s. 83-98
  • Tidskriftsartikel (refereegranskat)abstract
    • This study presents a method to simulate Tmrt building-resolving while considering both micro-scale urban structures and meso-scale atmospheric conditions. We extended the model SOLWEIG, one of the few methods to derive mean radiant temperature (Tmrt) building-resolved and city-wide, to include spatial patterns of meteorological input. Based on a day within an extreme heat event (2003) in Berlin, Germany, we examined the effect of the new method on Tmrt, which uses gridded meteorological input data from a mesoscale weather model, compared to a standard set-up using ungridded data. Results indicted a considerable effect of spatially resolved air temperature (up to 3.2 K) during midnight. Furthermore, we detected high sensitivity of Tmrt to the partitioning of direct and diffuse short-wave radiation. The spatial pattern of Tmrt revealed that at midday the city centre exhibited low values compared to open areas. We conclude that considering meso-scale atmospheric conditions and urban structure for simulating Tmrt city-wide can lead to a more appropriate description of heat-stress hazards and might also be valuable for climate-sensitive urban planning.
  •  
30.
  • Kent, Christoph W., et al. (författare)
  • Evaluation of Urban Local-Scale Aerodynamic Parameters: Implications for the Vertical Profile of Wind Speed and for Source Areas
  • 2017
  • Ingår i: Boundary-Layer Meteorology. - : Springer Science and Business Media LLC. - 0006-8314 .- 1573-1472. ; 164:2, s. 183-213
  • Tidskriftsartikel (refereegranskat)abstract
    • © 2017 The Author(s)Nine methods to determine local-scale aerodynamic roughness length (Formula presented.) and zero-plane displacement (Formula presented.) are compared at three sites (within 60 m of each other) in London, UK. Methods include three anemometric (single-level high frequency observations), six morphometric (surface geometry) and one reference-based approach (look-up tables). A footprint model is used with the morphometric methods in an iterative procedure. The results are insensitive to the initial (Formula presented.) and (Formula presented.) estimates. Across the three sites, (Formula presented.) varies between 5 and 45 m depending upon the method used. Morphometric methods that incorporate roughness-element height variability agree better with anemometric methods, indicating (Formula presented.) is consistently greater than the local mean building height. Depending upon method and wind direction, (Formula presented.) varies between 0.1 and 5 m with morphometric (Formula presented.) consistently being 2–3 m larger than the anemometric (Formula presented.). No morphometric method consistently resembles the anemometric methods. Wind-speed profiles observed with Doppler lidar provide additional data with which to assess the methods. Locally determined roughness parameters are used to extrapolate wind-speed profiles to a height roughly 200 m above the canopy. Wind-speed profiles extrapolated based on morphometric methods that account for roughness-element height variability are most similar to observations. The extent of the modelled source area for measurements varies by up to a factor of three, depending upon the morphometric method used to determine (Formula presented.) and (Formula presented.).
  •  
31.
  •  
32.
  • Khorram-Manesh, Amir, 1958, et al. (författare)
  • Profiling Collapsing Half Marathon Runners-Emerging Risk Factors : Results from Gothenburg Half Marathon
  • 2020
  • Ingår i: Sports. - : MDPI. - 2075-4663. ; 8:1, s. 1-11
  • Tidskriftsartikel (refereegranskat)abstract
    • Among several serious medical conditions, arrhythmia and heat stroke are two important causes of death during endurance races. Clinically, collapsing might be the first sign of these serious conditions and may mimic the more common and benign exercise-associated collapse. Several risk factors have been reported in the literature. We aimed to conduct a qualitative study to find a perceived risk profile among runners who collapsed and who were transported by ambulances to the nearest hospital during Gothenburg's half marathon (2010-2017). Collapsing runners seem to lack the ability to make a decision to withdraw from the contest despite being exhausted. They feel the pain, but are unable to put meaning to their feeling, to adjust their pacing, and to handle other influences. Consequently, they do not overcome the problem or assess the situation. These individual mental characteristics may indicate a unique profile for collapsing runners. Pre-race health control and educational initiatives aiming at mental preparedness and information before endurance races might be a necessary step to avoid life-threatening complications.
  •  
33.
  • Klingberg, Jenny, 1978, et al. (författare)
  • Leaf area measurements of urban woodlands, parks and trees in Gothenburg, Sweden
  • 2015
  • Ingår i: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July 2015, Toulouse, France.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Leaf area of urban vegetation is an important characteristic since it influences e.g. the urban climate through transpiratory cooling, air quality through air pollutant deposition and water management through rainfall interception. Measurements of leaf area are fundamental to accurately model these processes. Few studies have however presented leaf area measurements in the urban environment. The aim of this study was to i) describe the urban greenery based on measurements of leaf area index (LAI) of trees in different types of urban environments and ii) compare two different methods to measure LAI of urban trees. During the summer of 2014, LAI was measured in a central urban deciduous woodland, a suburban mixed forest, a central old park, a grove adjacent to a traffic route and in allotment gardens in Gothenburg, Sweden. In addition, single urban trees of seven common urban tree species in Gothenburg were measured (Acer platanoides, Aesculus hippocastanum, Betula pendula, Fagus sylvatica, Prunus serrulata, Quercus robur and Tilia europaea). Two different indirect methods were used; the LAI-2200 plant canopy analyzer (Li-cor Inc.) and hemispherical photography. The digital images were analyzed with Hemisfer (Schleppi, WSL). The canopy measurements were performed in a grid or cross with 8-32 points with fixed intervals. For single urban trees, 3-6 specimen of each species was measured. Average LAI of the measured urban parks and forests ranged between 2.6 and 4.8. A better way to characterize the different sites was to use cumulative density functions, which visualized the degree of heterogeneity. The old urban park had the largest LAI range (0 - 8.3). As a comparison, LAI ranged from 2.4 to 5.9 in the more homogenous urban woodland. LAI based on hemispherical photos was similar to the values received by the LAI-2200 plant canopy analyzer. Both methods had advantages and disadvantages. The urban environment offers challenges not present in forest canopies, such as interference of buildings. A combination of methods might be necessary for an environment as heterogeneous as the urban, with both single trees and forest canopies.
  •  
34.
  •  
35.
  • Knez, Igor, 1959-, et al. (författare)
  • Psychological mechanisms in outdoor place and weather assessment: towards a conceptual model
  • 2009
  • Ingår i: International Journal of Biometeorology. - : Springer Science and Business Media LLC. - 1432-1254 .- 0020-7128. ; 53:1, s. 101-111
  • Tidskriftsartikel (refereegranskat)abstract
    • The general aim has been to illuminate the psychological mechanisms involved in outdoor place and weather assessment. This reasoning was conceptualized in a model, tentatively proposing direct and indirect links of influence in an outdoor place–human relationship. The model was subsequently tested by an empirical study, performed in a Nordic city, on the impact of weather and personal factors on participants’ perceptual and emotional estimations of outdoor urban places. In line with our predictions, we report significant influences of weather parameters (air temperature, wind, and cloudlessness) and personal factors (environmental attitude and age) on participants’ perceptual and emotional estimations of outdoor urban places. All this is a modest, yet significant, step towards an understanding of the psychology of outdoor place and weather assessment.
  •  
36.
  • Konarska, Janina, 1986, et al. (författare)
  • Applications of dual-wavelength hemispherical photography in urban climatology and urban forestry
  • 2021
  • Ingår i: Urban Forestry & Urban Greening. - : Elsevier BV. - 1618-8667 .- 1610-8167. ; 58
  • Tidskriftsartikel (refereegranskat)abstract
    • Digital hemispherical photography (DHP) is widely used to measure the radiative environment and estimate sky view factors (SVF) in urban areas and leaf area index (LAI) in forests. However, a limitation is the difficulty to distinguish trees from buildings, or leaves from stems and branches. In this study, we collected and processed dual-wavelength photographs recording visible and near-infrared (NIR) light in order to classify pixels into sky, green and woody plant elements, and buildings. Three applications of the method are presented: calculation of partial SVFs accounting for the obstruction of sky by buildings and vegetation separately, the modelling of mean radiant temperature (Tmrt), and the correction of LAI estimates for light intercepted by woody elements and buildings. The obtained partial SVFs were in good agreement with values modelled based on digital surface models. Distinguishing between buildings and vegetation in the modelling of long-wave radiation fluxes in the SOLWEIG model resulted in differences in modelled Tmrt by up to 3 °C. The bias of LAI estimates in urban parks caused by the light interception by woody elements and buildings was found to be relatively small (3–4 %). However, the presented method shows a high potential for estimates of LAI of urban vegetation in densely built-up areas.
  •  
37.
  • Konarska, Janina, 1986, et al. (författare)
  • Influence of vegetation and building geometry on the spatial variations of air temperature and cooling rates in a high latitude city
  • 2016
  • Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 36:5, s. 2379-2395
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to provide a better understanding of how vegetation and building geometry influence the spatial distribution of air temperature and nocturnal cooling rates (CR) in a high-latitude city. Intra-urban thermal variations were analysed in two seasons (May–September and November–March) and in different weather conditions (clear, calm and cloudy, windy) in Gothenburg, Sweden. Simultaneous air temperature measurements were conducted for 2years (2012–2013) at ten fixed park and street sites characterized by varying type and amount of vegetation, building geometry, openness and surface cover. Several spatial characteristics, including sky view factor (SVF) as well as the cover and volume of buildings and trees, were calculated within circular areas of radii ranging from 10 to 150m. Spatial characteristics were found to explain air temperature distribution in the studied area to a large extent throughout the day and year, in both clear, calm as well as cloudy, windy conditions. The highest correlations were found for weighted calculation areas accounting for the influence of both nearest (10m) and wider (25–150m) surroundings. Park sites remained cooler than built-up areas, with the most pronounced cooling effect (0.8°C) on clear, calm days of the warm season. The most important factor governing CR around sunset was SVF. However, on clear, calm nights of the warm season, they were also enhanced by vegetation, indicating the influence of evapotranspiration. Minimum night-time air temperature was governed mostly by the presence of buildings. Within the street canyon, a daytime cooling and night-time warming effect of a street tree was observed, particularly in the warm season. The study shows the importance of various spatial characteristics describing openness, amount of vegetation and building geometry in analysing intra-urban variations in daytime and night-time air temperature.
  •  
38.
  • Konarska, Janina, 1986, et al. (författare)
  • Transmissivity of solar radiation through crowns of single urban trees—application for outdoor thermal comfort modelling
  • 2014
  • Ingår i: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 117:3-4, s. 363-376
  • 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.
  •  
39.
  • Konarska, Janina, 1986, et al. (författare)
  • Transpiration of urban trees and its cooling effect in a high latitude city
  • 2016
  • Ingår i: International journal of biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 60:1, s. 159-172
  • Tidskriftsartikel (refereegranskat)abstract
    • An important ecosystem service provided by urban trees is the cooling effect caused by their transpiration. The aim of this study was to quantify the magnitude of daytime and night-time transpiration of common urban tree species in a high latitude city (Gothenburg, Sweden), to analyse the influence of weather conditions and surface permeability on the tree transpiration, and to find out whether tree transpiration contributed to daytime or nocturnal cooling. Stomatal conductance and leaf transpiration at day and night were measured on mature street and park trees of seven common tree species in Gothenburg: Tilia europaea, Quercus robur, Betula pendula, Acer platanoides, Aesculus hippocastanum, Fagus sylvatica and Prunus serrulata. Transpiration increased with vapour pressure deficit and photosynthetically active radiation. Midday rates of sunlit leaves ranged from less than 1 mmol m−2 s−1 (B. pendula) to over 3 mmol m−2 s−1 (Q. robur). Daytime stomatal conductance was positively related to the fraction of permeable surfaces within the vertically projected crown area. A simple estimate of available rainwater, comprising of precipitation sum and fractional surface permeability within the crown area, was found to explain 68 % of variation in midday stomatal conductance. Night-time transpiration was observed in all studied species and amounted to 7 and 20 % of midday transpiration of sunlit and shaded leaves, respectively. With an estimated night-time latent heat flux of 24 W m−2, tree transpiration significantly increased the cooling rate around and shortly after sunset, but not later in the night. Despite a strong midday latent heat flux of 206 W m−2, a cooling effect of tree transpiration was not observed during the day.
  •  
40.
  • Konarska, Janina, 1986, et al. (författare)
  • Transpiration of urban trees and its impact on nocturnal cooling in Gothenburg, Sweden
  • 2015
  • Ingår i: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July 2015, Toulouse, France.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • One of the ecosystem services provided by urban trees is the cooling effect caused by their transpiration. However, while the transpiration of forest trees has been widely studied, little research has been conducted on the daytime and night-time transpirational cooling effect of mature urban trees. Knowledge about the transpiration of street and park trees and its response to different environmental factors can prove useful in estimating the thermal influence of urban greenery as well as in urban planning and management. The aim of this study is to i) quantify the magnitude and diurnal variation of transpiration of common urban tree species in a high latitude city (Gothenburg, Sweden), ii) analyse the influence of weather conditions and fraction of permeable surfaces within the vertically projected crown area on tree transpiration, and iii) find out whether transpiration of urban trees remains active during the night and therefore contributes to nocturnal cooling. Measurements were conducted on mature street and park trees of seven tree species common in Gothenburg: Tilia europaea (Common lime), Quercus robur (English oak), Betula pendula (Silver birch), Acer platanoides (Norway maple), Aesculus hippocastanum (Horse chestnut), Fagus sylvatica (European beech) and Prunus serrulata (Japanese cherry). Stomatal conductance and leaf transpiration were measured using a LI-6400XT Portable Photosynthesis System (LI-COR Biosciences) at daytime and night-time on warm summer days of 2012-2013 in Gothenburg. Leaf area index (LAI) of the studied trees was measured with a LAI-2200 Plant Canopy Analyser (LI-COR Biosciences) in order to estimate the latent heat flux due to tree transpiration. Leaf transpiration was found to increase with vapour pressure deficit and photosynthetically active radiation, with on average 22% of the midday incoming solar radiation being converted into latent heat flux. Midday rates of sunlit leaves varied between species, ranging from less than 1 mmol m-2 s-1 (B. pendula) to over 3 mmol m-2 s-1 (Q. robur). Daytime stomatal conductance was positively related to the fraction of permeable surfaces within the vertically projected tree crown area. A simple estimate of available rainwater, comprising of precipitation sum and a fractional surface permeability within the tree crown area, was found to explain 68% of variation in midday stomatal conductance. The results indicate that a high fractional surface permeability can minimize the frequency of water stress experienced by urban trees and enhance their transpirational cooling. Night-time transpiration was observed in all studied species and was positively related to daytime tree water use. Nocturnal transpiration amounted to 7% and 20% of midday transpiration of sunlit and shaded leaves, respectively. With an estimated latent heat flux of 27 W m-2, evening tree transpiration enhanced the cooling rates around and 1-2 hours after sunset, but not later in the night. The results of transpiration measurements will be combined with vegetation data derived from LIDAR and LAI measurements to estimate neighbourhood- to city-scale cooling effect provided by urban trees.
  •  
41.
  • Kotthuas, Simone, et al. (författare)
  • Quantifying the impact of surface heterogeneities on the radiative response of a simplified urban surface
  • 2015
  • Ingår i: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July 2015, Toulouse, France.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Radiation exchanges at the urban surface strongly influence climate conditions within cities. Therefore they directly impact outdoor human thermal comfort, have implications to building energy use and partly determine the energy available to turbulent surface fluxes. The radiative response of the urban surface is a function of both material composition and geometric arrangement of the surface objects. Hence it is crucial to understand how both aspects integrate to the bulk surface characteristics of albedo and emissivity to successfully interpret observed energy exchanges and provide realistic values for model parameterisations. Radiation fluxes are often observed with radiometers installed above the urban canopy. Given the latter is spatially complex and its interaction with the incoming solar radiation may change over time, dynamic modelling approaches are required to relate the fluxes observed to the surface source area. In this study the relative importance of material properties and the three-dimensional surface structure on radiation fluxes at different locations above the urban canopy are considered. Both long- and shortwave radiation fluxes were observed atvarious locations above a simplified urban setting, the Comprehensive Outdoor Scale Model experiment for urban climate (COSMO; Tokyo Institute of Technology, Japan) and high-reflectance materials were installed in the source areas of the radiometers for certain periods. Surface temperatures of all facets were measured by thermal imagery to provide further insight into radiative heating and cooling of the various surfaces. The simplified canopy allows for the spatio-temporal variations observed to be directly associated with certain source area characteristics (e.g. fraction of roof surface). Observations are compared to results from the dynamic radiation model SOLWEIG (Lindberg et al. 2008), characterising the spatial variations of radiation fluxes across the whole canopy. Given SOLWEIG can also be applied in complex, real city settings, conclusions drawn help to advance source area calculations of radiometers operated in many urban climate studies.
  •  
42.
  • Landier, Lucas, et al. (författare)
  • 3D modeling of radiative transfer and energy balance in urban canopies combined to remote sensing acquisitions
  • 2016
  • Ingår i: IGARSS 2016 - 2016 IEEE International Geoscience and Remote Sensing Symposium. - 2153-7003.
  • Konferensbidrag (refereegranskat)abstract
    • In this paper we present a study on the use of remote sensing data combined to the 3D modeling of radiative transfer (RT) and energy balance in urban canopies in the aim to improve our knowledge on anthropogenic heat fluxes in several European cities (London, Basel, Heraklion, and Toulouse). The approach is based on the forcing by the use of LandSAT8 data of a coupled radiative transfer model DART (Direct Anisotropic Radiative Transfer) (www.cesbio.upstlse.fr/dart) with an energy balance module. LandSAT8 visible remote sensing data is used to better parametrize the albedo of the urban canopy and thermal remote sensing data is used to enhance the anthropogenic component in the coupled model. This work is conducted in the frame of the H2020 project URBANFLUXES, which aim is to improve the efficiency of remote-sensing data usage for the determination of the anthropogenic heat fluxes in urban canopies
  •  
43.
  • Landier, Lucas, et al. (författare)
  • Calibration of DART Radiative Transfer Model with Satellite Images for Simulating Albedo and Thermal Irradiance Images and 3D Radiative Budget of Urban Environment
  • 2016
  • Ingår i: 36th EARSeL Symposium, 20-24 June 2016, Bonn, Germany.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Remote sensing is increasingly used for managing urban environment. In this context, the H2020 project URBANFLUXES aims to improve our knowledge on urban anthropogenic heat fluxes, with the specific study of three cities: London, Basel and Heraklion. Usually, one expects to derive directly 2 major urban parameters from remote sensing: the albedo and thermal irradiance. However, the determination of these two parameters is seriously hampered by complexity of urban architecture. For example, urban reflectance and brightness temperature are far from isotropic and are spatially heterogeneous. Hence, radiative transfer models that consider the complexity of urban architecture when simulating remote sensing signals are essential tools. Even for these sophisticated models, there is a major constraint for an operational use of remote sensing: the complex 3D distribution of optical properties and temperatures in urban environments. Here, the work is conducted with the DART (Discrete Anisotropic Radiative Transfer) model. It is a comprehensive physically based 3D radiative transfer model that simulates optical signals at the entrance of imaging spectro-radiometers and LiDAR scanners on board of satellites and airplanes, as well as the 3D radiative budget, of urban and natural landscapes for any experimental (atmosphere, topography,…) and instrumental (sensor altitude, spatial resolution, UV to thermal infrared,…) configuration. Paul Sabatier University distributes free licenses for research activities. This paper presents the calibration of DART model with high spatial resolution satellite images (Landsat 8, Sentinel 2, etc.) that are acquired in the visible (VIS) / near infrared (NIR) domain and in the thermal infrared (TIR) domain. Here, the work is conducted with an atmospherically corrected Landsat 8 image and Bale city, with its urban database. The calibration approach in the VIS/IR domain encompasses 5 steps for computing the 2D distribution (image) of urban albedo at satellite spatial resolution. (1) DART simulation of satellite image at very high spatial resolution (e.g., 50cm) per satellite spectral band. Atmosphere conditions are specific to the satellite image acquisition. (2) Spatial resampling of DART image at the coarser spatial resolution of the available satellite image, per spectral band. (3) Iterative derivation of the urban surfaces (roofs, walls, streets, vegetation,…) optical properties as derived from pixel-wise comparison of DART and satellite images, independently per spectral band. (4) Computation of the band albedo image of the city, per spectral band. (5) Computation of the image of the city albedo and VIS/NIR exitance, as an integral over all satellite spectral bands. In order to get a time series of albedo and VIS/NIR exitance, even in the absence of satellite images, ECMWF information about local irradiance and atmosphere conditions are used. A similar approach is used for calculating the city thermal exitance using satellite images acquired in the thermal infrared domain. Finally, DART simulations that are conducted with the optical properties derived from remote sensing images give also the 3D radiative budget of the city at any date including the date of the satellite image acquisition.
  •  
44.
  • Lau, Kevin Ka-Lun, et al. (författare)
  • Investigating solar energy potential in tropical urban environment : A case study of Dar es Salaam, Tanzania
  • 2017
  • Ingår i: Sustainable Cities and Society. - : Elsevier BV. - 2210-6707. ; 30, s. 118-127
  • Tidskriftsartikel (refereegranskat)abstract
    • Solar energy is considered to be an alternative sustainable energy source in the urban environment. The potential of using solar energy in urban areas is highly dependent on urban morphology which affects the level of solar irradiance received by individual buildings. Many studies focus on solar energy potential of building form in urban areas but relatively few studies examine how urban morphology affects solar energy potential of urban neighbourhoods. It leads to inefficient design of neighbourhoods in terms of solar energy potential. The present study investigates the potential of exploiting solar energy in Dar es Salaam, Tanzania by using numerical modelling of solar irradiance on building roofs and façades. It is shown that there is substantial solar irradiance received by building roofs in all four study neighbourhoods and urban morphology has considerable effects on annual solar irradiance. Solar irradiance of different orientations of tilted roofs and façades is subject to seasonality of the solar azimuth angle. It is suggested that such abundant solar energy sources would provide solutions to accommodate the increasing energy demand and to improve living quality in urban areas due to the rapid urbanization of the city.
  •  
45.
  • Lau, Kevin Ka-Lun, 1983, et al. (författare)
  • Street geometry design and its effect on mean radiant temperature: A parametric study based on numerical modelling
  • 2015
  • Ingår i: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July 2015, Toulouse, France.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The spatial variation of hotspots, in terms of their locations and magnitude, is examined in the present study, using the Solar and LongWave Environmental Irradiance Geometry (SOLWEIG) model. The effect of street geometry design parameters such as H/W ratios and street orientations on the radiant heat load are analyzed for three European cities with different regional climatic conditions. Various physical configurations of street trees are examined for their corresponding potential in mitigating the radiant heat load within urban structures. Findings suggest that a dense urban structure (H/W ratio ≥ 2) is capable of reducing radiant heat load at street level. High H/W ratios do not only reduce the magnitude of hotspots, but also changes their spatial distribution. The N-S canyons are found to be more favourable than the E-W canyons since they limit sun exposure to several hours at noon, despite of the diminishing difference between two orientations when H/W ratio increases. Diagonal streets reduce the magnitude of hotspots but increase the areas affected by moderately high mean radiant temperature (Tmrt). NE-SW orientated streets exhibits higher average hourly Tmrt during daytime since they are largely sun-exposed at the hottest time of the day. The highest mitigating effect of street trees is found when they are located in the sunlit areas. The reduction in average Tmrt decreases with increasing H/W ratios but considerable mitigating effect is still observed in the NE-SW orientations. It is also observed that larger tree crowns, even with higher spacing between individual trees, provide better shading than closely placed trees with smaller tree crowns. The present study provides information about the locations and magnitude of hotspots in different urban settings as well as the design of street trees as a mitigation measure to radiant heat load. It helps urban planners and designers to better design neighbourhoods in order to improve pedestrian thermal comfort within urban areas.
  •  
46.
  • Lau, Kevin Ka-Lun, 1983, et al. (författare)
  • The effect of urban geometry on mean radiant temperature under future climate change: a study of three European cities
  • 2015
  • Ingår i: International journal of biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 59:7, s. 799-814
  • Tidskriftsartikel (refereegranskat)abstract
    • Future anthropogenic climate change is likely to increase the air temperature (T a ) across Europe and increase the frequency, duration and magnitude of severe heat stress events. Heat stress events are generally associated with clear-sky conditions and high T a , which give rise to high radiant heat load, i.e. mean radiant temperature (T mrt ). In urban environments, T mrt is strongly influenced by urban geometry. The present study examines the effect of urban geometry on daytime heat stress in three European cities (Gothenburg in Sweden, Frankfurt in Germany and Porto in Portugal) under present and future climates, using T mrt as an indicator of heat stress. It is found that severe heat stress occurs in all three cities. Similar maximum daytime T mrt is found in open areas in all three cities despite of the latitudinal differences in average daytime T mrt . In contrast, dense urban structures like narrow street canyons are able to mitigate heat stress in the summer, without causing substantial changes in T mrt in the winter. Although the T mrt averages are similar for the north–south and east–west street canyons in each city, the number of hours when T mrt exceeds the threshold values of 55.5 and 59.4 °C—used as indicators of moderate and severe heat stress—in the north–south canyons is much higher than that in the east–west canyons. Using statistically downscaled data from a regional climate model, it is found that the study sites were generally warmer in the future scenario, especially Porto, which would further exacerbate heat stress in urban areas. However, a decrease in solar radiation in Gothenburg and Frankfurt reduces T mrt in the spring, while the reduction in T mrt is somewhat offset by increasing T a in other seasons. It suggests that changes in the T mrt under the future scenario are dominated by variations in T a . Nonetheless, the intra-urban differences remain relatively stable in the future. These findings suggest that dense urban structure can reduce daytime heat stress since it reduces the number of hours of high T mrt in the summer and does not cause substantial changes in average and minimum T mrt in the winter. In dense urban settings, a more diverse urban thermal environment is also preferred to compensate for reduced solar access in the winter. The extent to which the urban geometry can be optimized for the future climate is also influenced by local urban characteristics.
  •  
47.
  • Lindberg, Fredrik, 1974, et al. (författare)
  • 3D modelling of vegetation within a 2D model – evaluation and application
  • 2012
  • Ingår i: The Eight International Conference on Urban Climates.. ; :abstract nr 180
  • 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.
  •  
48.
  •  
49.
  • Lindberg, Fredrik, 1974, et al. (författare)
  • Characteristics of the mean radiant temperature in high latitude cities—implications for sensitive climate planning applications
  • 2014
  • Ingår i: International Journal Of Biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 58:5, s. 613-627
  • 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.
  •  
50.
  • Lindberg, Fredrik, 1974, et al. (författare)
  • Impact of city changes and weather on anthropogenic heat flux in Europe 1995–2015
  • 2013
  • Ingår i: Urban Climate. - 2212-0955. ; 4, s. 1-15
  • 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.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-50 av 110
Typ av publikation
tidskriftsartikel (65)
konferensbidrag (37)
rapport (4)
doktorsavhandling (2)
bokkapitel (2)
Typ av innehåll
refereegranskat (76)
övrigt vetenskapligt/konstnärligt (34)
Författare/redaktör
Lindberg, Fredrik, 1 ... (109)
Thorsson, Sofia, 197 ... (53)
Holmer, Björn, 1943 (28)
Grimmond, CSB (13)
Rayner, D.P. 1973 (11)
Grimmond, C.S.B. (11)
visa fler...
Rayner, David (10)
Wallenberg, Nils, 19 ... (10)
Parlow, Eberhard (10)
Chrysoulakis, Nektar ... (9)
Mitraka, Zina (8)
Feigenwinter, Christ ... (8)
Olofson, K. Frans G. ... (7)
Börjesson, Mats, 196 ... (6)
Carlström, Eric, 195 ... (6)
Khorram-Manesh, Amir ... (6)
Del Frate, Fabio (6)
Nilson, Finn, 1980- (5)
Palm, Gunnar (5)
Heldens, Wieke (5)
Gastellu-Etchegorry, ... (5)
Klostermann, Judith (5)
Esch, Thomas (5)
Al Bitar, Ahmad (5)
Klingberg, Jenny, 19 ... (4)
Eliasson, Ingegärd, ... (4)
Gabey, Andrew (4)
Marconcini, Mattia (4)
Pleijel, Håkan, 1958 (3)
Andersson-Sköld, Yvo ... (3)
Grimmond, S (3)
Bäcklin, Oskar, 1991 (3)
Grimmond, Sue (3)
Johansson, Erik (2)
Schneider, A. (2)
Uddling, Johan, 1972 (2)
Hedblom, Marcus (2)
Trimmel, H (2)
Jonsson, Per (2)
Knez, Igor (2)
Fröberg, Andreas, 19 ... (2)
Feigenwinter, C. (2)
Scherer, Dieter (2)
Wästberg, Dag (2)
Björklund, Jesper, 1 ... (2)
Raustorp, Anders, 19 ... (2)
Olvmo, Mats, 1956 (2)
Martilli, Alberto (2)
Chrysoulakis, N (2)
Gastellu-Etchegorry, ... (2)
visa färre...
Lärosäte
Göteborgs universitet (107)
Karlstads universitet (6)
Chalmers tekniska högskola (4)
Stockholms universitet (3)
Högskolan i Gävle (3)
Lunds universitet (3)
visa fler...
Umeå universitet (2)
Sveriges Lantbruksuniversitet (2)
VTI - Statens väg- och transportforskningsinstitut (2)
Uppsala universitet (1)
Linköpings universitet (1)
Karolinska Institutet (1)
Marie Cederschiöld högskola (1)
visa färre...
Språk
Engelska (105)
Svenska (5)
Forskningsämne (UKÄ/SCB)
Naturvetenskap (105)
Medicin och hälsovetenskap (11)
Samhällsvetenskap (7)
Teknik (6)
Lantbruksvetenskap (1)
Humaniora (1)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy