Apport de la modélisation météorologique à l'évaluation des besoins énergétiques des bâtiments

Buildings represent 40 percents of the end-use energy. Thus, they constitute a key point of the energy saving policies. Recently, climate modeling systems that include a mesoscale atmospheric model, sophisticated urban parameterizations have been developed to account for the complexity of the urban climate and its interactions with the building energy loads. This study aims to assess the capability of such climate modeling systems to provide climate and energy guidelines to urban planners.For this, we used the research collaborative WRF/ARW-BEP+BEM climate modeling system and performed sensitivity tests considering the territory of the Eurodistrict in 2010, and then in 2030. The results reveal that the climate modeling system achieves estimating the building energy needs over the study area, but also indicate that the building energy needs are more sensitive to the building intrinsic properties and occupant behavior than to the urban forms and their induced urban heat island.Les bâtiments représentent 40 pourcents de la consommation finale d'énergie. Ils sont ainsi le fer de lance des politiques de réduction des dépenses énergétiques. Récemment, des systèmes de modèles climatiques qui incluent un modèle atmosphérique régional et des paramétrisations urbaines sophistiquées ont été développés. Ils considèrent la complexité de l’îlot de chaleur urbain et ses interactions avec les besoins énergétiques des bâtiments. Dans quelle mesure ces systèmes constituent-ils des outils d’aide à la décision pour les autorités locales ? Cette étude menée sur le territoire de l'Eurodistrict (Strasbourg-Kehl) en 2010, puis en 2030, à l’aide du système de modèles de climat WRF/ARW-BEP+BEM a démontré que si le système de modèles estimait de manière fiable les besoins en chauffage des bâtiments, ces derniers étaient davantage sensibles aux caractéristiques intrinsèques des bâtiments qu'aux formes urbaines et à l'îlot de chaleur urbain induit par ces formes

Development of a new 1D urban canopy model: coherences between surface parameterizations

A 1-D Canopy Interface Model (CIM) was developed in order to better simulate the effect of urban obstacles on the atmosphere in the boundary layer. The model solves the Navier-Stokes equations on a high-resolved gridded vertical column. The effect of the surface is simulated testing a set of theories and urban parameterizations. The final proposition guarantees its coherence with past theories in any atmospheric stability and terrain configuration. Obstacle characteristics are computed using surface and volume porosities in each cell of the model domain. These porosities are used to weight several terms in the Navier-Stokes equations. A 1.5-order turbulence closure is used in order to compute the turbulent coefficients with the TKE. The mixing length takes into account the density of the obstacles and their height. The turbulent scheme is designed in order to keep CIM coherent with the Prandtl theory in neutral atmospheric conditions and with the MOST in stratified atmospheric stability when CIM is used over plane surfaces. The modifications brought to the main governing equations are discussed following theoretical analysis and experiences with CIM, simulating the averaged meteorological variables (wind speed, turbulent kinetic energy (TKE), temperature and humidity). Simulations are compared with analytical solutions, when possible, and also simulations issued from a computational fluid dynamics (CFD) model. The results show how constant values, usually prescribed, can be theoretically estimated and how the buoyancy term of the turbulent kinetic energy balance equation should be adjusted accordingly. After modifications, it is shown that CIM is coherent with past propositions in any case of atmospheric stabilities over plane surfaces. The use of CIM in presence of obstacles is based on the extension of the 1.5 order turbulence closure to compute the turbulent coefficients with the TKE. CIM shows simulations in good agreement with the CFD simulations in the presence of obstacles. It is able to reproduce an inertial sub-layer as described by the Prandlt and constant-flux layer theory above a displacement height over a homogeneous canopy

Project Coolbit: Can your watch predict heat stress and thermal comfort sensation?

10.1088/1748-9326/abd130ENVIRONMENTAL RESEARCH LETTERS16

Les WEIHERMATTEN (Alsace, France):: Integrating small humid areas (<1 ha) in climate change adaptation strategies in small towns

International audienceHumid areas are portions of surfaces that are usually flooded or gorged with water, in which soil properties and/or vegetation communities (when present) are inherited from the water abundance and dynamics (e.g., presence of hygrophile plants and hydromorphic soils with redoxic horizons; Article L.211-1 of the French Environmental Code).Humid areas provide non-negligible ecosystem services to humans since they can regulate the water cycle (mitigation of flood and drought impacts in a watershed, hydrological functions), store mineral materials or even filter/sequester water or air chemicals such as atmospheric carbon dioxide (physical and biogeochemical functions). Furthermore, they constitute a great support to biodiversity and human production activities (e.g., hayfields for extensive agriculture; ecological and economic functions) and are therefore protected by diverse European and national ecological programs and (supposedly) urban planning policies from urbanization.Yet, the past ten years have seen rapid degradations of humid areas' qualities and quantities along with the intensification of agriculture production, and urbanization, but also the rarefaction of the water resource with climate changes (Rappinel et al.,2019). In such a context small humid areas (< 1 ha) are less scrutineered by experts and preservation policies than large ones (e.g., Ramsar humid areas). The urbanization threat is even bigger when the ‘small’ humid areas are sited in the territory of small municipalities (<50,000 inhabitants) whose are lacking expert knowledge and are facing more immediate concerns (e.g., budget equilibrium, attractiveness competitions).To raise awareness on the necessity to preserve small humid areas in small municipalities, we plead for the setting of an intensive exploratory and collaborative project between researchers and local stakeholders aiming to...(i) Understand the dynamic of a small 1,3 ha humid meadows located in the Murbach sub-watershed and nearby Buhl 3,500 inhabitants municipality (Les Weihermatten, Buhl-France).(ii) Characterize the cooling potential of the small humid meadow in the nearby town and within its watershed (human heat stress perspective)(iii) Raise awareness (if applicable) among local stakeholders on the role of small humid areas in local climate change adaptation strategies

Can planning fight the urban overheating and should we tackle the "the urban heat island" per se ?

International audienceExtreme temperatures in the built environment receive more audible cues every year as a result of the combined effects of local urban driven heats and climate change (urban overheating). They are in particular associated with increased mortalities during prolonged and severe heat waves, increased heat stress and poor thermal comfort in outdoors, as well as extra loads on energy, water and transport infrastructures. Though local urban heats (surface-, canopy-, boundary layer-) are associated with poor quality and/or lack of urban green in dense urban fabrics, construction materials that facilitate heat trapping and heat storage in the urban fabrics as well as human activities’ heat-related emissions; urban planners and designers are in the foreground of the definition of overheating coping strategies. They are assumed to frame the future urban resilience to heat. This talk will first present the progress in urban climate knowledge vis-a-vis the role of urban forms on urban overheating and heat stress alleviations. It will secondly discuss the major bottlenecks in the implementation of urban overheating coping strategies, discussing in particular the definition of heat and targets in the planning documents. To do so, the study relies on a literature review of the most reputed international scientific works on urban forms &amp; urban heat* since 1980 as well as on the analysis of four French climate action plans (Marseille, Lyon, Besançon, and Strasbourg) and associated planning documents. Though the drivers of urban heats are well-known (also in the urban planner community), the literature review highlighted the difficulties both in urban climate and planning to apprehend the whole scale and dynamics of the urban heats when it comes to urban heat resilience

Can planning fight the urban overheating and should we tackle the "the urban heat island" per se ?

International audienceExtreme temperatures in the built environment receive more audible cues every year as a result of the combined effects of local urban driven heats and climate change (urban overheating). They are in particular associated with increased mortalities during prolonged and severe heat waves, increased heat stress and poor thermal comfort in outdoors, as well as extra loads on energy, water and transport infrastructures. Though local urban heats (surface-, canopy-, boundary layer-) are associated with poor quality and/or lack of urban green in dense urban fabrics, construction materials that facilitate heat trapping and heat storage in the urban fabrics as well as human activities’ heat-related emissions; urban planners and designers are in the foreground of the definition of overheating coping strategies. They are assumed to frame the future urban resilience to heat. This talk will first present the progress in urban climate knowledge vis-a-vis the role of urban forms on urban overheating and heat stress alleviations. It will secondly discuss the major bottlenecks in the implementation of urban overheating coping strategies, discussing in particular the definition of heat and targets in the planning documents. To do so, the study relies on a literature review of the most reputed international scientific works on urban forms &amp; urban heat* since 1980 as well as on the analysis of four French climate action plans (Marseille, Lyon, Besançon, and Strasbourg) and associated planning documents. Though the drivers of urban heats are well-known (also in the urban planner community), the literature review highlighted the difficulties both in urban climate and planning to apprehend the whole scale and dynamics of the urban heats when it comes to urban heat resilience

Les WEIHERMATTEN (Alsace, France):: Integrating small humid areas (<1 ha) in climate change adaptation strategies in small towns

International audienceHumid areas are portions of surfaces that are usually flooded or gorged with water, in which soil properties and/or vegetation communities (when present) are inherited from the water abundance and dynamics (e.g., presence of hygrophile plants and hydromorphic soils with redoxic horizons; Article L.211-1 of the French Environmental Code).Humid areas provide non-negligible ecosystem services to humans since they can regulate the water cycle (mitigation of flood and drought impacts in a watershed, hydrological functions), store mineral materials or even filter/sequester water or air chemicals such as atmospheric carbon dioxide (physical and biogeochemical functions). Furthermore, they constitute a great support to biodiversity and human production activities (e.g., hayfields for extensive agriculture; ecological and economic functions) and are therefore protected by diverse European and national ecological programs and (supposedly) urban planning policies from urbanization.Yet, the past ten years have seen rapid degradations of humid areas' qualities and quantities along with the intensification of agriculture production, and urbanization, but also the rarefaction of the water resource with climate changes (Rappinel et al.,2019). In such a context small humid areas (< 1 ha) are less scrutineered by experts and preservation policies than large ones (e.g., Ramsar humid areas). The urbanization threat is even bigger when the ‘small’ humid areas are sited in the territory of small municipalities (<50,000 inhabitants) whose are lacking expert knowledge and are facing more immediate concerns (e.g., budget equilibrium, attractiveness competitions).To raise awareness on the necessity to preserve small humid areas in small municipalities, we plead for the setting of an intensive exploratory and collaborative project between researchers and local stakeholders aiming to...(i) Understand the dynamic of a small 1,3 ha humid meadows located in the Murbach sub-watershed and nearby Buhl 3,500 inhabitants municipality (Les Weihermatten, Buhl-France).(ii) Characterize the cooling potential of the small humid meadow in the nearby town and within its watershed (human heat stress perspective)(iii) Raise awareness (if applicable) among local stakeholders on the role of small humid areas in local climate change adaptation strategies

Chaleur ou chaleurs au pluriel ?

National audienceComme un écho à l'été et au changement climatique, la chaleur est omniprésente dans les discours médiatiques, politiques et, scientifiques. Elle se décline sous la forme de canicule, d'extrêmes de température, d'îlot de chaleur urbain, ou de stress thermique : en bref, d'excès de chaleur. La chaleur évoque des comportements adaptatifs 'plaisants' (ex. manger une glace, aller à la piscine, porter des vêtements légers) comme des comportements adaptatifs jugés plutôt déplaisants (rester enfermer chez soi, faire attention à sa sueur). Bénéfique en hiver, l'excès de chaleur se doit d'être atténuée en été. Toutefois, quelle 'chaleur' doit-on atténuer ? Comment le corps humains la perçoit-elle ? Quand est-elle excessive ? Et comment utilisons-nous cette perception dans l'aménagement des villes et les politiques d'adaptation au changement climatique ? Autant de questions qui sont au centre des recherches interdisciplinaires en climatologie urbaine et en biométéorologie (i.e. étude des interactions entre le vivant et la météorologie)

Chaleur ou chaleurs au pluriel ?

National audienceComme un écho à l'été et au changement climatique, la chaleur est omniprésente dans les discours médiatiques, politiques et, scientifiques. Elle se décline sous la forme de canicule, d'extrêmes de température, d'îlot de chaleur urbain, ou de stress thermique : en bref, d'excès de chaleur. La chaleur évoque des comportements adaptatifs 'plaisants' (ex. manger une glace, aller à la piscine, porter des vêtements légers) comme des comportements adaptatifs jugés plutôt déplaisants (rester enfermer chez soi, faire attention à sa sueur). Bénéfique en hiver, l'excès de chaleur se doit d'être atténuée en été. Toutefois, quelle 'chaleur' doit-on atténuer ? Comment le corps humains la perçoit-elle ? Quand est-elle excessive ? Et comment utilisons-nous cette perception dans l'aménagement des villes et les politiques d'adaptation au changement climatique ? Autant de questions qui sont au centre des recherches interdisciplinaires en climatologie urbaine et en biométéorologie (i.e. étude des interactions entre le vivant et la météorologie)

Overheating adaptations in acclimatised Singaporeans: Do spatial adaptation options matter? A pilot study Tanjong Pagar CBD case study

International audienceClimate responsive design aims to mitigate extreme heat by consciously integrating climate principles inurban architectures and developments. Thereby, the adoption of climate-responsive design in urbanareas is foreseen to increase the adaptation capacities of urban dwellers to overheating. However,behavioural overheating adaptation can also be aspatial (e.g. a change in activity program, clothes, orfood regime), and thus not depend on the quality of outdoor spaces. According to the behaviouralplanned theory, the selection of one of these is determined by the individual knowledge of heatadaptation options, its transaction capacities with its daily routines, and cultural beliefs giving itscommunity belonging.We investigated the nature of the overheating adaptation strategies in the densely-built city-state ofSingapore for different extreme thermal perceptions so as to determine whenever and when spacematters in individual overheating coping strategies in a tropical climate and mature tertiary society. Weused the records of two biometeorological campaigns aiming to assess the thermal sensitivity ofacclimatized Singaporeans, which were, on occasion, extended with a survey questionnaire dedicated tooverheating behavioural adaptation. Unsurprisingly, extreme sun, rain, and heat triggered adaptativestrategies, while extreme humidity and wind did not. Rain adaptation was mainly aspatial, while extremesun and heat triggered a mix of spatial and aspatial strategies with more option diversity for the sunthan for the heat. Some adaptation options were mutualized as for the air conditioning to cope both withextreme heat and humidity sensations. Last, not all the selected adaptation options reflected thenational Singaporean programs aiming to promote outdoors: urban parks, seafront or large waterreserves although supporting the “city in a garden” marketing were declared to be less used thannaturally and artificially covered roads developed close to house units to foster active mobility