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- Chrysoulakis, N., et al.
(författare)
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Urban energy exchanges monitoring from space
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8
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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.
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| 2. |
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| 3. |
- Chrysoulakis, N, et al.
(författare)
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7E.3: Urban Energy Balance from Space: the URBANFLUXES Project
- 2018
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Ingår i: 10th International Conference on Urban Climate/14th Symposium on the Urban Environment, New York, US, August 2018.
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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.
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| 4. |
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| 5. |
- Lindberg, Fredrik, 1974, et al.
(författare)
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Influence of ground surface characteristics on the mean radiant temperature in urban areas
- 2016
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Ingår i: International Journal of Biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 60:9, s. 1439-1452
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Tidskriftsartikel (refereegranskat)abstract
- The effect of variations in land cover on mean radiant temperature (T-mrt) is explored through a simple scheme developed within the radiation model SOLWEIG. Outgoing longwave radiation is parameterised using surface temperature observations on a grass and an asphalt surface, whereas outgoing shortwave radiation is modelled through variations in albedo for the different surfaces. The influence of ground surface materials on T-mrt is small compared to the effects of shadowing. Nevertheless, altering ground surface materials could contribute to a reduction in T-mrt to reduce the radiant load during heat-wave episodes in locations where shadowing is not an option. Evaluation of the new scheme suggests that despite its simplicity it can simulate the outgoing fluxes well, especially during sunny conditions. However, it underestimates at night and in shadowed locations. One grass surface used to develop the parameterisation, with very different characteristics compared to an evaluation grass site, caused T-mrt to be underestimated. The implications of using high temporal resolution (e.g. 15 minutes) meteorological forcing data under partly cloudy conditions are demonstrated even for fairly proximal sites.
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| 6. |
- Lindberg, Fredrik, 1974, et al.
(författare)
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Sunlit fractions on urban facets – Impact of spatial resolution and approach
- 2015
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Ingår i: Urban Climate. - 2212-0955. ; 12, s. 65-84
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Tidskriftsartikel (refereegranskat)abstract
- The extent of the surface area sunlit is critical for radiative energy exchanges and therefore for a wide range of applications that require urban land surface models (ULSM), ranging from human comfort to weather forecasting. Here a computationally demanding shadow casting algorithm is used to assess the capability of a simple single-layer urban canopy model, which assumes an infinitely long rotating canyon (ILC), to reproduce sunlit areas on roofs, walls and roads over central London. Results indicate that the sunlit road areas are well-represented but somewhat smaller using an ILC, while sunlit roofs areas are consistently larger, especially for dense urban areas. The largest deviations from real world sunlit areas are for roofs during mornings and evenings. Sunlit fractions on walls are overestimated using an ILC during mornings and evenings are found. The implications of these errors are dependent on the application targeted. For example, (independent of albedo) ULSMs used in numerical weather prediction applying ILC representation of the urban form will overestimate outgoing shortwave radiation from roofs due to the overestimation of sunlit fraction of the roofs. Complications of deriving height to width ratios from real world data are also discussed.
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| 7. |
- Lindberg, Fredrik, 1974, et al.
(författare)
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Urban Multi-scale Environmental Predictor (UMEP): An integrated tool for city-based climate services
- 2018
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Ingår i: Environmental Modelling and Software. - : Elsevier BV. - 1364-8152. ; 99, s. 70-87
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 The Authors UMEP (Urban Multi-scale Environmental Predictor), a city-based climate service tool, combines models and tools essential for climate simulations. Applications are presented to illustrate UMEP's potential in the identification of heat waves and cold waves; the impact of green infrastructure on runoff; the effects of buildings on human thermal stress; solar energy production; and the impact of human activities on heat emissions. UMEP has broad utility for applications related to outdoor thermal comfort, wind, urban energy consumption and climate change mitigation. It includes tools to enable users to input atmospheric and surface data from multiple sources, to characterise the urban environment, to prepare meteorological data for use in cities, to undertake simulations and consider scenarios, and to compare and visualise different combinations of climate indicators. An open-source tool, UMEP is designed to be easily updated as new data and tools are developed, and to be accessible to researchers, decision-makers and practitioners.
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| 8. |
- Onomura, Shiho, 1985, et al.
(författare)
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Meteorological forcing data for urban outdoor thermal comfort models from a coupled convective boundary layer and surface energy balance scheme
- 2015
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Ingår i: Urban Climate. - : Elsevier BV. - 2212-0955. ; 11, s. 1-23
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Tidskriftsartikel (refereegranskat)abstract
- Site-specific meteorological forcing appropriate for applications such as urban outdoor thermal comfort simulations can be obtained using a newly coupled scheme that combines a simple slab convective boundary layer (CBL) model and urban land surface model (ULSM) (here two ULSMs are considered). The former simulates daytime CBL height, air temperature and humidity, and the latter estimates urban surface energy and water balance fluxes accounting for changes in land surface cover. The coupled models are tested at a suburban site and two rural sites, one irrigated and one unirrigated grass, in Sacramento, U.S.A. All the variables modelled compare well to measurements (e.g. coefficient of determination = 0.97 and root mean square error = 1.5 °C for air temperature). The current version is applicable to daytime conditions and needs initial state conditions for the CBL model in the appropriate range to obtain the required performance. The coupled model allows routine observations from distant sites (e.g. rural, airport) to be used to predict air temperature and relative humidity in an urban area of interest. This simple model, which can be rapidly applied, could provide urban data for applications such as air quality forecasting and building energy modelling, in addition to outdoor thermal comfort.
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