1.
Thorsson, Sofia, 1972, et al.
(författare)
Present and projected future mean radiant temperature for three European cities
2017
Ingår i: International Journal of Biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 61:9
Tidskriftsartikel (refereegranskat) abstract
© 2017 The Author(s)Present-day and projected future changes in mean radiant temperature, Tmrt in one northern, one mid-, and one southern European city (represented by Gothenburg, Frankfurt, and Porto), are presented, and the concept of hot spots is adopted. Air temperature, Ta, increased in all cities by 2100, but changes in solar radiation due to changes in cloudiness counterbalanced or exacerbated the effects on Tmrt. The number of days with high Tmrt in Gothenburg was relatively unchanged at the end of the century (+1 day), whereas it more than doubled in Frankfurt and tripled in Porto. The use of street trees to reduce daytime radiant heat load was analyzed using hot spots to identify where trees could be most beneficial. Hot spots, although varying in intensity and frequency, were generally confined to near sunlit southeast-southwest facing walls, in northeast corner of courtyards, and in open spaces in all three cities. By adding trees in these spaces, the radiant heat load can be reduced, especially in spaces with no or few trees. A set of design principles for reducing the radiant heat load is outlined based on these findings and existing literature.
2.
3.
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.
4.
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.
5.
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.
6.
7.
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.
8.
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.
9.
10.
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.
