Article

How much air conditioning can increase air temperatures for a city like Paris (France)?

Authors:
  • Meteo France International
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Abstract

A consequence of urban heat islands in summer is an increase in the use of air conditioning in urbanized areas, which while cooling the insides of buildings, releases waste heat to the atmosphere. A coupled model consisting of a meso-scale meteorological model (MESO-NH) and an urban energy balance model (TEB) has been used to simulate and quantify the potential impacts on street temperature of four air conditioning scenarios at the scale of Paris. The first case consists of simulating the current types of systems in the city and was based on inventories of dry and evaporative cooling towers and free cooling systems with the river Seine. The other three scenarios were chosen to test the impacts of likely trends in air conditioning equipment in the city: one for which all evaporative and free cooling systems were replaced by dry systems, and the other two designed on a future doubling of the overall air conditioning power but with different technologies. The comparison between the scenarios with heat releases in the street and the baseline case without air conditioning showed a systematic increase in the street air temperature, and this increase was greater at nighttime than day time. It is counter-intuitive because the heat releases are higher during the day. This is due to the shallower atmospheric boundary layer during the night. The increase in temperature was 0.5 °C in the situation with current heat releases, 1 °C with current releases converted to only sensible heat, and 2 °C for the future doubling of air conditioning waste heat released to air. These results demonstrated to what extent the use of air conditioning could enhance street air temperatures at the scale of a city like Paris, and the importance of a spatialized approach for a reasoned planning for future deployment of air conditioning in the city.

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... It also increases the instability of the urban boundary layer during the morning and evening hours (Chen et al. 2009). Though the waste heat released from AC is greatest at noon in summer, its impact on air temperatures is most noticeable at night (Chen et al. 2009;Salamanca et al. 2012;De Munck et al. 2013;Salamanca et al. 2014). ...
... Similar findings were presented in e.g. De Munck et al. (2013) and Martilli et al. (2015), stating that 21 3 Impact of air conditioning (AC) systems on the outdoor thermal environment anthropogenic heat emissions due to AC waste heat further increase the difference in Q H between urban and suburban grid cells. In addition, a spatial analysis (see section 3.4 in Paper II) demonstrates a substantially stronger effect of VerAC22 on T 2.5m than HorAC22, especially in the central areas where high-rise buildings dominate. ...
... It also increases the instability of the urban boundary layer in the morning and evening [24]. Although the release of waste heat due to AC is greatest at noon in summer, the effect on air temperatures is more pronounced during the night [20,[24][25][26]. ...
Thesis
In dieser Arbeit wird die Entwicklung eines Gebäudeenergiemodells (BEM) und eines Schemas für die mittlere Strahlungstemperatur ($T_mrt$) vorgestellt, das in das Doppel-Canyon basierte städtische Bestandsschichtsschema (DCEP) integriert ist. Das erweiterte DCEP-BEM Modell zielt darauf ab, eine Verbindung zwischen anthropogener Wärme und dem Stadtklima herzustellen, indem Gebäude in Straßenschluchten einbezogen werden, um die Energieflüsse auf städtischen Oberflächen, die Auswirkungen der anthropogenen Wärme auf die Atmosphäre, die Innenraumlufttemperatur und die Abwärme von Klimaanlagen zu untersuchen. Das DCEP-BEM wird mit dem mesoskaligen Klimamodell COSMO-CLM (COnsortium for Small-scale MOdelling in CLimate Mode, im Folgenden CCLM) gekoppelt und zur Simulation des Winters und Sommers 2018 in Berlin. Die Auswertung der Wintersimulationen zeigt, dass CCLM/DCEP-BEM den mittleren Tagesverlauf der gemessenen turbulenten Wärmeströme gut reproduziert und die simulierte 2-m-Lufttemperatur und den städtischen Wärmeinseleffekt (UHI) verbessert. Im Sommer bildet das CCLM/DCEP-BEM die Innenraumlufttemperatur richtig ab und verbessert die Ergebnisse für die 2-m-Lufttemperatur und die UHI leicht. Außerdem wird das CCLM/DCEP-BEM angewendet, um die Abwärmeemissionen von Klimaanlagen im Sommer zu untersuchen. Die Abwärmeemissionen der Klimaanlagen erhöhen die Lufttemperatur in Oberflächennähe erheblich. Der Anstieg ist in der Nacht und in hochurbanisierten Gebieten stärker ausgeprägt. Es werden zwei Standorte für die AC-Außengeräte betrachtet: entweder an der Wand eines Gebäudes (VerAC) oder auf dem Dach eines Gebäudes (HorAC). Die Auswirkung von HorAC ist im Vergleich zu VerAC insgesamt geringer, was darauf hindeutet, dass HorAC einen kleineren Einfluss auf die oberflächennahe Lufttemperatur und den UHI hat. Ein Schema für $T_mrt$ wird für das CCLM/DCEP-BEM entwickelt und umfassend validiert. Es wird gezeigt, dass dieses Schema eine zuverlässige Darstellung von $T_mrt$ bietet.
... Наличие в мезомасштабной метеорологической модели города блока теплового баланса зданий с расчетной температурой внутри помещений и параметризацией работы приборов кондиционирования позволило провести чи-сленные расчеты эффекта взаимодействия энергопотребления, температуры и мезомасштабной циркуляции для городов: Нью-йорк [55,56], Гонконг [57], Париж [58], Токио [59], Осака [60], Мадрид [61]. ...
... Для преодоления отмеченных недостатков в модели UCL включаются в виде отдельных блоков модели энергетического баланса зданий (BEM -building energy models) [47,58,79,84,[116][117][118][119]. В BEM энергетический баланс зданий рассчитывается исходя из условия поддержания внутри помещений комфортного диапазона температур и, возможно, влажности. ...
Article
The anthropogenic impact on the Earths climate system is currently one of the main factors determining climate change on all spatial scales, from local to global. A lot of scientific research is devoted to the direct and indirect influence of various types of human activity on the state of the Earths climate system. Using different climate models, feedbacks that enhance or weaken anthropogenic effects in the process of global warming have been studied in enough detail. Developed in recent years regional models of climatic and meteorological processes are allowing to describe in detail the climate features in urban agglomerations and the role of feedback in the development of mesoscale atmospheric processes. This review is devoted to the description and analysis of mesoscale feedbacks in the climate system, including the energy consumption of an urban economy that depends on climatic and weather conditions, and the role of these feedbacks in the formation and dynamics of urban climate and the needs of the urban economy in energy supply.
... Indeed, previous investigations reported several different relevant UHI dependencies, including the city size and population density (Oke, 1982;Clinton and Gong, 2013;Oke et al., 2017;Manoli et al., 2019), socioeconomic conditions (e.g., Hong et al., 2019;Li et al., 2020;He et al., 2021), urban vegetation coverage (Kaloustian and Diab, 2015;Peng et al., 2012;Zhou et al., 2014;Nogueira and Soares, 2019), background climate conditions (namely precipitation and wind; Zhou et al., 2013;Lemonsu et al., 2013;Zhao et al., 2014;Manoli et al., 2019), and urban morphology (city geometry, building height, construction materials, etc.; Oke, 1973Oke, , 1982Zhou et al., 2017;Krayenhoff et al., 2018;Nogueira and Soares, 2019;Masson et al., 2020). Heat release resulting from human activities has also been shown to modulate the UHI (De Munck et al., 2013;Schoetter et al., 2020). Moreover, surface and near-surface air temperatures over natural regions also display large sensitivity to the complex land use and land cover patterns (e.g., Beljaars et al., 1996;Koster et al., 2004;Johannsen et al., 2019;Nogueira et al., 2020aNogueira et al., , 2021a, which represents an additional layer of complexity to the UHI. ...
... The present study assesses the ability of the LSM-UCM approach to downscale ERA5 reanalysis, the fifth, and latest, generation reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) to resolutions of a few kilometers over dense urban areas. Specifically, we analyze the added value of the Météo-France SURFEX (Surface Externalisée) surface modeling platform (Le Moigne, 2018) in improving the simulation of the UHI and SUHI over Paris, a European megacity characterized by a well-known strong urban heat island effect (e.g., Sarkar and De Ridder, 2011;De Munck et al., 2013;Hamdi et al., 2015;Lemonsu et al., 2015;Daniel et al., 2019). SURFEX is particularly relevant in this context since it has shown to perform particularly well in offline urban simulations (e.g., Hamdi et al., 2015;Lemonsu et al., 2015;Nogueira and Soares, 2019;Nogueira et al., 2020b). ...
Article
Full-text available
Cities concentrate people, wealth, emissions, and infrastructure, thus representing a challenge and an opportunity for climate change mitigation and adaptation. This urgently demands for accurate urban climate projections to help organizations and individuals to make climate-smart decisions. However, most of the large ensembles of global and regional climate model simulations do not include sophisticated urban parameterizations (e.g., EURO-CORDEX; CMIP5/6). Here, we explore this shortcoming in ERA5 (the latest generation reanalysis from the European Centre for Medium-Range Weather Forecasts) and in a simulation with the SURFEX (Surface Externalisée) land surface model employing the widely used bulk bare rock approach. The city of Paris is considered as a case study. Subsequently, we apply a more complex urban scheme – SURFEX coupled to the Town Energy Balance (TEB) urban canopy model to assess its benefits on characterizing the Paris urban climate. Both simulations and ERA5 were compared to the LSA SAF (Satellite Application Facility on Land Surface Analysis) land surface temperature product to evaluate the simulation of Parisian surface urban heat island (SUHI). Our results show a significant added value of SURFEX-TEB in reproducing the SUHI during the daytime and the UHI during both the daytime and nighttime (with overall reductions in the bias and root mean square error and improvements in the representation of the statistics of the SUHI/UHI displayed by the Perkins skill score or S score). The improvement in the simulated SUHI is lower during the nighttime due to the lack of land–atmosphere feedbacks in the proposed offline framework. Nonetheless, the offline SURFEX-TEB framework applied here clearly demonstrates the added value of using more comprehensive parameterization schemes to simulate the urban climate and, therefore, allowing the improvement of urban climate projections.
... Building heat rejection to the outdoor climate by air-conditioning is considered as a growing source of urban anthropogenic heat, particularly in the United States (Ackermann, 2002;Akbari, 2002), with growth in the United Kingdom anticipated (Boardman, et al., 2005;Pathan, et al., 2008). Energy use and climate interactions are considered by a number of studies, which highlight increased use of air-conditioning as adversely affecting the urban climate (Sailor, 2010;Iamarino, et al., 2012;de Munck, et al., 2013), as Anthropogenic emissions UHI intensity Building energy use well as the UK national carbon reduction target (He, et al., 2005;Pathan, et al., 2008). Strategies for addressing climate warming risks have advocated the introduction of detailed legislation (ASC, 2014), and as an alternative, 'nudge theory' to assist behavioural adaptation (Thaler & Sunstein, 2008). ...
... In comparison, the simulation of the Gloucester Terrace canyon resulted in a moderate nocturnal increase of 0.4 K. The nocturnal significance of such anthropogenic heat emissions is attributed by climatologists to the contracted urban canopy layer, which concentrates emissions nearer to the surface, while during the day the greater depth of the urban boundary layer encourages rejected heat to rise further up into the atmosphere to minimise the effect at the surface (de Munck, et al., 2013). Another complicating factor is that some air-conditioning systems use evaporative cooling to exchange heat (as latent heat) with the outdoor environment (Sailor, 2010). ...
Thesis
Full-text available
A warming climate, increasing frequency and severity of extreme heat events, and the heat island effect are cumulatively expected to exacerbate environmental thermal loading on urban buildings. This in turn could lead to increased summertime overheating, with potential for causing adverse effects to the health and wellbeing of building occupants. The means for addressing such heat-related risks are likely to influence energy consumption and CO2 emission trends, particularly in residential areas where active cooling has traditionally received less attention in the United Kingdom. If energy efficient approaches are not adopted, future patterns of urban living are likely to adversely influence the carbon reduction target prescribed by the Climate Change Act 2008. This dissertation is concerned with identifying adaptations for addressing summertime overheating risk in temperate climate urban residential buildings, and ways in which both authorities and designers can facilitate such measures. The method for addressing this considered the simulation of a residential street canyon within the London heat island, with the findings discussed with reference to a multidisciplinary evidence base. The findings highlighted that accounting for the warmer urban microclimate had a beneficial 12.9% reduction in the energy consumption estimate, although at the expense of increased overheating risk. Improving the thermal performance of the envelope had a patent energy use benefit, although the mixed influence on overheating highlighted that threshold exceedance increased while ‘severity’ was reduced. Adding adaptive capabilities to this improved envelope demonstrated that ‘comfort’ could be achieved without the need for energy intensive active solutions. The argument against the widespread adoption of mechanical cooling as a principal adaptation was highlighted by an estimated 0.4 K increase in nocturnal canyon temperatures and 77 metric tons of CO2 released to the climate. In addition to the said findings, the study verified a method pathway that included the use of an Urban Weather Generator to account for microclimatic variations in building energy simulations.
... Besides affecting energy consumption, previous studies show varying urban climatic effects by different AC systems. Using a mesoscale meteorological model (MMM) coupled to an urban canopy model (UCM), de Munck et al. (2013) found that the urban heat island intensity in Paris increases by 0.5°C when water-cooled AC systems are converted to individual air-cooled systems. Further, Wang et al. (2018) simulated two alternative water-cooled AC systems, namely the direct cooling system (similar to DCS) and central piped cooling towers, via the building energy model (BEM) of a coupled MMM-UCM and found that although these systems can improve daytime pedestrian thermal comfort by reducing air temperature, they may inhibit urban ventilation and induce air pollution issues. ...
... In the present study, a similar dip in Q H is found for the DCS scenario in the evening but the simulated effect on T2m is relatively small (Fig. 5). Though it is common to observe greater temperature effects by AC heat discharge at night when the boundary layer is shallower (de Munck et al., 2013), our results indicate minimal differences in nocturnal Q H and T2m for Hong Kong because of the low nighttime AC usage in nondomestic buildings and the boundary layer that remains deep at night supported by turbulence over the high-density urban areas (Kwok et al., 2021). A proportion of the urban Q E is due to the evaporative cooling towers in FU-TURE. ...
Article
Climate warming, rapid economic development, and urbanisation in (sub)tropical regions lead to increasing electricity demand for building air-conditioning that could jeopardise the efforts of decarbonisation required to meet the climate change mitigation goals. This study investigates two strategies to reduce building energy consumption due to air-conditioning: 1) the bottom-up adoption of an Adaptive Thermal Comfort (ATC)-based cooling setpoint temperature and 2) the top-down implementation of efficient District Cooling Systems (DCS). The subtropical high-density city of Hong Kong is chosen for case study since detailed data on the city's current and realistic future urban form and function are available. Numerical simulations representing the feedback between urban climate and building energy consumption are conducted by employing a mesoscale atmospheric model coupled to an urban climate and building energy model for a scenario of future (mid-21st century) Hong Kong. A prolonged high temperature event representative of future extreme conditions is simulated, during which the ATC and DCS strategies reduce building cooling energy consumption by 9.7% and 5.9%, respectively. The ATC has almost no effect on the local meteorological conditions, whereas the DCS reduces daytime sensible heat flux by up to 600 W/m² and near-surface air temperature by almost 1 °C in the districts where it is adopted. The DCS thus also contributes to lowering outdoor heat stress in these areas. The cost-free ATC strategy is easily applicable in residential buildings worldwide and can break the vicious cycle in overcooled buildings, where occupants are acclimatised to lower indoor temperature and thus require more air-conditioning than necessary. Apart from reducing energy consumption and near-surface air temperature, the DCS brings additional benefits in building space utilisation and rooftop design. Future policy orientations should therefore encourage a societal change towards the ATC lifestyle and incorporate DCS in the planning of new development areas.
... In urban areas with cooling demand, the Q fs -T-E PFB forms selfreinforcing loops (Fig. 2), causing adverse effects on UHI mitigation and energy conservation, though urban warming favorably reduces the building energy demand for heating and Q fs in winter. Focusing on the adverse effects, a considerable number of studies [7,8,[12][13][14][15][16][17][18][19][20][21][22] have qualitatively mentioned the Q fs -T-E PFB, as referred to as "classic feedback loop" in an International Energy Agency (IEA) report [23]. Particularly in developing nations, many of which lie in hot climate zones with three-quarters of the world's urban population [1], yearlong urban energy demand for cooling could enhance the adverse effects of the PFB [24,25]. ...
... Based on this method, Ohashi et al. [30] detected ΔT ah up to 1 • C during summer in Osaka. In addition, simulation studies [16,17,31,32] have analyzed the ΔQ fs → ΔT using numerical weather models with urban surface parameterizations [33], which originated from slab models and then evolved into urban canopy models (UCMs). Particularly in the last two decades, those parameterizations have made significant progress, in which instead of individual-building-scale detailed building energy models (BEMs) like EnergyPlus [34], urban-district-scale simplified BEMs were developed and coupled with UCMs. ...
Article
Full-text available
The interaction between urban air temperature (T) and building cooling energy demand (E) generates a well-known positive feedback (PFB), which is mediated by sensible anthropogenic heat (Qfs) and named Qfs-T-E PFB in this study. This PFB could induce self-reinforced warming in urban areas, but its effects have not been completely quantified. Hence, this study aimed to clarify these effects by targeting Osaka, a Japanese major city. Focusing on the from-weekends-to-weekdays increase in urban energy consumption including E increase as an observable trigger of the PFB, its induced T rise due to growth in Qfs was estimated with the fed-back additional E gain on weekdays based on observed ground-level T and district-wise electric power consumption during summer. The result indicated that the weekdays–weekends contrast in energy consumption over Osaka could induce the Qfs-T-E PFB effects, which resulted in fed-back E gain reaching 10% on weekdays. Such observational PFB impact on E was found to be roughly reproducible by the proposed urban meteorological model, named WRF-CM-BEM. Thus, the validated model was applied to the quantification of the climatological PFB impact on T based on feedback gain (gA ) which means a percentage of T variation caused by the PFB. An attempt was made to quantify gA through the two-cases simulations of the weekdays-run and holidays-run for the months of August in 10 years, focusing again on the weekdays–weekends contrast in urban energy consumption. The simulations provided estimates on gA, whose daytime averages reached nearly 10% in the downtown commercial areas and 20% in the leeward-located residential areas, suggesting the influence of sea breeze heat advection of downtown Qfs. Such estimated impacts on T were roughly in the same order of magnitude compared to those in a few earlier studies that were not based on observational validations and seemed to be non-negligible, considering the feedback impacts on global surface warming estimated with gA of approximately 50% by the Intergovernmental Panel on Climate Change.
... According to Wen and Lian (2009), the AC system can increase the urban air temperature between 0.2 and 2.5°C. A similar study was carried out by de Munck et al. (2013) over Paris and found that AC systems increase air temperature between 0.5 and 2°C during summer while a similar impact was also noted by Salamanca et al. (2012) in Madrid. Mughal et al. (2019) mentioned that heat from AC systems can lead up to 2.2°C increase of air temperature over Singapore. ...
... Mughal et al. (2019) mentioned that heat from AC systems can lead up to 2.2°C increase of air temperature over Singapore. The impacts of AH over urban areas have been studied in North America (Fan and Sailor, 2005;Salamanca et al., 2014;Chow et al., 2014) and countries such as Japan (Takane et al., 2017), China (Liu and Han, 2016;Chen and Hu, 2017), Taiwan (Lin et al., 2016) and France (Iamarino et al., 2012;de Munck et al., 2013). ...
Article
Increased urbanization and anthropogenic activities in tropical cities lead to the temperature gradient betweenthe urban and rural environments, causing the urban heat island (UHI) phenomenon. This study is a pioneeringattempt that examines the changes in the temporal evolution of the surface energy budget induced by urbaniza-tion known as the Anthropogenic Influence (AI) in modifying the urban climate of a tropical city using WeatherResearch and Forecasting (WRF) numerical modeling system. The AI from buildings, traffic and power plants isdetermined infive different scenarios and the model is validated with high temporal resolution in-situ data.These increased AIs provide improved WRF capability with root mean square error (RMSE) less than 2 °C andmean bias error (MBE) less than 0.5 °C between different performance indicators. Building envelopes (withoutindoor activity/equipment) are found to be a major contributor in exacerbating the island wide urban heatΔTaAI,maxto 3.7 °C compared to baseline all green scenario. This is followed by the air-conditioner (AC) systemsthat contribute up to 1.4 °C. The maximum local contribution of traffic and power plants to urban heat is 0.9 °Cand 0.4 °C, respectively.
... An adverse consequence of urban heat islands is the increased usage of cooling systems (fans, coolers, and air-conditioners) during summer, which in turn liberates more heat to the establishment surroundings, enhancing the heat island impact (de Munck et al., 2013). Delhi's yearly electrical power consumption is around 3.2 × 10 10 kWh, as stated in the economic survey of 2017-2018, of which approximately 29.1% (in 2016) contribution is from the domestic cooling systems (Economic Survey of Delhi, 2019). ...
Article
Full-text available
The paradigm to shift toward cleaner fuel in vehicles and upgrade emission norms is a frequent discussion. The current study is a narrative of comparing fuels (gasoline, diesel, and compressed natural gas) in non-commercial four-wheel vehicles on the urban heat island (UHI) and their effects on emissions of greenhouse gases (GHG) and pollutants. We assume all such vehicles are single-fuel driven at a time in the densely populated urban city of Delhi, corresponding to the fiscal year 2017. We estimate that CNG can potentially raise the local temperature due to vehicular heat released and increased power plant load during summer by 1.09 • C and produces ~1.6 times more heat than gasoline and diesel vehicles for the same distance traveled. CNG lowered the PM 2.5 emissions by 81%, NO x by 45%, and VOC by 3%, while CO emissions increased by ~14% and GHG emissions increased by 15%. For natural gas to become more effective, CNG vehicles' efficiency needs to improve, and the dependence on electricity should be more on cleaner resources. The analysis is based on estimates for Delhi, although the results would apply to other cities in India and globally.
... L'utilisation de la climatisation, si elle permet de bénéficier d'un environnement agréable à l'intérieur des bâtiments, présente deux inconvénients majeurs : d'une part, elle consomme de l'énergie et contribue ainsi à l'augmentation des émissions de GES ; d'autre part, elle rejette la chaleur à l'extérieur des bâtiments, ce qui augmente l'intensité de l'îlot de chaleur urbain. La contribution de la climatisation à l'ICU, évaluée à environ 1 à 2°C pour l'agglomération parisienne (de Munck et al., 2013), détériore le confort climatique des espaces publics. ...
Thesis
Cette thèse s’intéresse aux modalités de construction territoriale de l’adaptation au changement climatique (ACC), avec le recours à une approche interdisciplinaire, à l’interface des sciences sociales et des sciences du climat. La première partie analyse la prise en compte du climat par certaines politiques publiques en les considérant sous une triple dimension : normative, organisationnelle et cognitive. L’examen de ces politiques, montre que les logiques sectorielles constituent un invariant des démarches d’ACC, et que faute d’approches territoriales, les mesures d’adaptation préconisées peinent à se concrétiser. Au plan organisationnel, la rareté des ressources, la caducité des instruments de planification et l’instabilité politique empêchent l’intégration de l’adaptation dans l’urbanisme. De plus, les représentations sociales des acteurs tunisois constituent de réels obstacles à cette émergence. La seconde partie traite de la fabrique des données urbaines nécessaires à la construction d’une expertise microclimatique. Une base de données architecturales, morphologiques et d’occupation du sol du Grand Tunis est constituée afin de pallier la pénurie des données urbaines. L’ensemble de ces données a été mis à disposition des acteurs, leur offrant ainsi la possibilité de se saisir des enjeux climatiques. La troisième partie mobilise ces bases de données afin de construire des cartes climatiques. Afin d’observer les dynamiques d’appropriation de ces cartes, nous avons mobilisé le cadre d’analyse de la théorie de l’acteur-réseau. Nous avons montré que les cartes climatiques influençaient peu l’action urbaine à Tunis. Pour permettre une meilleure appropriation des enjeux climatiques par les acteurs, nous avons opté pour la co-construction d’une plateforme de données environnementales qui englobe les données climatiques sans pour autant s’y réduire. Ce projet a joué le rôle de catalyseur de l’action collective en faveur de l’émergence de l’ACC dans l’urbanisme.
... The local climate zone (LCZ) scheme, originally proposed to provide an interdisciplinary taxonomy, plays an important role in urban heat island (UHI) effect studies [1]. With the deepening of research, it can also provide a foundation for other urban-oriented studies, such as population density estimation, economic development monitoring [2], urban climatology [3], infrastructure planning [4], navigation application of disaster mitigation [5], etc. Recently, with the resolution of satellite images becoming higher, and the swath becoming wider, LCZ classification in remote sensing images has attracted more attention due to its broad vision in urban-oriented applications [6]. ...
Article
Full-text available
The local climate zone (LCZ) scheme is of great value for urban heat island (UHI) effect studies by providing a standard classification framework to describe the local physical structure at a global scale. In recent years, with the rapid development of satellite imaging techniques, both multi-spectral (MS) and synthetic aperture radar (SAR) data have been widely used in LCZ classification tasks. However, the fusion of MS and SAR data still faces the challenges of the different imaging mechanisms and the feature heterogeneity. In this study, to fully exploit and utilize the features of SAR and MS data, a data-grouping method was firstly proposed to divide multi-source data into several band groups according to the spectral characteristics of different bands. Then, a novel network architecture, namely Multi-source data Fusion Network for Local Climate Zone (MsF-LCZ-Net), was introduced to achieve high-precision LCZ classification, which contains a multi-branch CNN for multi-modal feature extraction and fusion, followed by a classifier for LCZ prediction. In the proposed multi-branch structure, a split–fusion-aggregate strategy was adopted to capture multi-level information and enhance the feature representation. In addition, a self channel attention (SCA) block was introduced to establish long-range spatial and inter-channel dependencies, which made the network pay more attention to informative features. Experiments were conducted on the So2Sat LCZ42 dataset, and the results show the superiority of our proposed method when compared with state-of-the-art methods. Moreover, the LCZ maps of three main cities in China were generated and analyzed to demonstrate the effectiveness of our proposed method.
... In another study in Hongkong, China, the housing conditions were summarized, including factors such as green spaces, air ventilations, artificial wind tunnels, air conditioning, fans, etc. [111]. Research conducted in Tokyo, Japan, and Paris, France, revealed that air conditioning would release heat outside, raising the air temperature [132,133]. Another important indicator that cannot be ignored is the floor of the residence. Most of the time, people who live on the top floor are more at risk because they are close to the roof and are affected by draughts [134]. ...
Article
As a vital component of urban heat risk, the vulnerability of exposed elements must be assessed before further impact prediction and strategy implementation. In previous studies, heat vulnerability was commonly defined as the tendency to be adversely affected by an extremely high temperature from both physical and social perspectives. However, it cannot explain what the adverse effects are. Also, the decision-making of mitigation strategies was often regarded as an individual session, lacking a combination of heat vulnerability. This paper established a qualitative multi-sector network by discovering existing cause-effect within indicators related to heat vulnerability, extending the concept of vulnerability. It identified what makes population and urban elements vulnerable to urban heat from the view of the effects they trigger. Besides the physical and social sectors of demographic, urban elements, and exposure, three essential but frequently ignored effect sectors - emissions, human health, and economy - were also included in the causal network. Based on a new classification of mitigation strategies, they could connect with vulnerability indicators in multi-sectors, forming causal chains from intervention to their profound effects. A discussion of the network's future implementation was conducted in the end, prospecting the potential of a combination with the vulnerability assessment. This paper uncovers that future vulnerability assessments should include productivity as an indicator to show the adverse impact of high temperature on the economy. It also shows that different mitigation strategies can intervene in heat vulnerability assessment through all cause sectors, the sector of exposure, and the sector of emissions.
... To this end, particular attention has been paid to the feedback of AC systems on outdoor air temperatures. De Munck (De Munck et al. 2013) demonstrate a coupling scheme between a meso-meteorological model and a single layer-module to account for the built environment, in order to estimate Paris air temperature increase due to air conditioning units. The 6 days' simulation period was chosen for anticyclonic conditions of the 2003's heatwave. ...
... To this end, particular attention has been paid to the feedback of AC systems on outdoor air temperatures. De Munck (De Munck et al. 2013) demonstrate a coupling scheme between a meso-meteorological model and a single layer-module to account for the built environment, in order to estimate Paris air temperature increase due to air conditioning units. The 6 days' simulation period was chosen for anticyclonic conditions of the 2003's heatwave. ...
... The prime effect of urbanization on the local climate, investigated since the 1980s, is known as the urban heat island (UHI) effect: Cities are almost always warmer than their environment (1,2). The resulting heat stress, intensified by global warming, leads to health impairment, increased mortality (3,4), and/or an increase in energy consumption for air conditioning, which positively feedbacks on the UHI (5,6). As more than half of the world's population now lives in urban areas (7), it has become crucial to adapt cities and design new ones in a way that both improves thermal comfort and reduces energy consumption (8,9). ...
... The prime effect of urbanization on the local climate, investigated since the 1980s, is known as the urban heat island (UHI) effect: Cities are almost always warmer than their environment (1,2). The resulting heat stress, intensified by global warming, leads to health impairment, increased mortality (3,4), and/or an increase in energy consumption for air conditioning, which positively feedbacks on the UHI (5,6). As more than half of the world's population now lives in urban areas (7), it has become crucial to adapt cities and design new ones in a way that both improves thermal comfort and reduces energy consumption (8,9). ...
Article
Urban areas are a high-stake target of climate change mitigation and adaptation measures. To understand, predict, and improve the energy performance of cities, the scientific community develops numerical models that describe how they interact with the atmosphere through heat and moisture exchanges at all scales. In this review, we present recent advances that are at the origin of last decade's revolution in computer graphics, and recent breakthroughs in statistical physics that extend well-established path-integral formulations to nonlinear coupled models. We argue that this rare conjunction of scientific advances in mathematics, physics, computer, and engineering sciences opens promising avenues for urban climate modeling and illustrate this with coupled heat transfer simulations in complex urban geometries under complex atmospheric conditions. We highlight the potential of these approaches beyond urban climate modeling for the necessary appropriation of the issues at the heart of the energy transition by societies.
... Air Conditioning (AC) is another source that contributes to high AH in an urban area. Some of the studies related to AC were carried out in France (de Munck et al., 2013), the USA (Salamanca et al., 2014), and Hong Kong . Some studies also suggested the individual contribution of each sector in increasing AH. ...
Article
Changing urban land use dynamics and associated anthropogenic heat (AH) has increased warming over urban centres. This warming is associated with the Urban Heat Island (UHI) effect and is mainly studied in major cities worldwide. However, predominantly industrial regions can also experience heat island effect due to heat emissions from industrial infrastructure and associated activities. The current study examines the role of the urban morphology and anthropogenic heat over the Angul-Talcher region (industrial region) of Odisha state, India. The region is also referred to as India's highly polluted industrial cluster due to open cast mining and industries. In the present study, Weather Research and Forecast model (WRF) coupled with Single-Layer Urban Canopy Model (WRFUCM) has been modified to examine the impact of urban morphology and anthropogenic heat on the heat island effect over the region. The study refers modified version of WRFUCM as the WRFAH [Gridded] model, which incorporates anthropogenic heat from different industries with stack height information. It was found that the WRF model capabilities have improved in simulating surface meteorological variables such as temperature at 2 m, wind speed, and relative humidity with the inclusion of gridded AH. Urban canopies were estimated to bring in an increase of up to 0.77 • C in local near-surface temperatures during daytime and up to 2.12 • C during nighttime. AH emissions further increased temperatures by up to 0.32 • C during daytime and 0.69 • C during nighttime. Maximum heat island intensity with urban canopies is estimated to be 5.62 • C which increases to 7.11 • C with the inclusion of average AH released at canopy level. However, this has significantly improved to 5.88 • C with inputs of industry-specific AH released at stack heights with the WRFAH[Gridded] model against observed maximum heat island intensity of 6.06 • C. Overall, the influence of urban morphology was found to be higher than the influence of AH over the region at ground level, and the inclusion of gridded AH in the model showed improved performance for the heat island assessment.
... The downside is double, as this option is both energy consuming and contributes to the warming of street air temperatures. A study calculated that the air temperature in Paris would increase in average by +2 °C with twice the current amount of power (projection of 10 GW sensible heat released) used for airconditioning at the city scale (De Munck et al., 2013). Unfortunately, the use of AC is becoming predominant in many countries for a number of reasons (increasing comfort requirements, global and local warming, growth in local income, price of equipment and electricity, social equity) while it does the opposite to mitigating climate change. ...
Thesis
Due to climate change projecting increased heatwaves occurrence, ensuring that buildings designed and built today will be adapted to future warmer temperatures is essential. The scope of this Ph.D. is to propose a methodological contribution to the design of buildings that both mitigate (minimize yearly energy needs) and adapt (minimize summer indoor overheating, limit health-heat-related risk) to climate change. The methodology can be applied to any building case study in any climate. For this purpose, bias-adjusted weather files containing both present, future typical conditions and future heatwave periods were developed. The potential of different passive cooling mitigation and adaptation strategies to reduce summer indoor overheating is evaluated using these weather files through dynamic thermal simulations, sensitivity analysis and optimization methods. The results of this research work highlight that for the building case study, the evaluated strategies (buffer spaces, thermal mass, roof optical properties, glazing ratio, ventilative cooling) have a strong capacity to enable summer thermal comfort in future typical summers in Paris and in La Rochelle. However, in Carpentras, and under recurring heatwaves in all three cities, the limits of these mitigation and adaptation measures are recognized. In fact, the future heatwaves consistently lead to consecutive days of indoor overheating exposure during both daytime and nighttime for building occupants, leading to a health-heat-related risk especially for the most vulnerable. These sequences are not detected when using only future typical years, which stresses the relevance of this work. Only the combination of optimized building envelopes, ventilative cooling strategies and adaptive opportunities from building occupants (solar control, increased indoor air velocities) have the potential to offset the projected recurring health-heat-related risk, particularly elevated in the South of France.
... Recently, many studies have investigated the impact of anthropogenic heat on the thermal environment [13][14][15][16], which has been carried out on specific types of anthropogenic heat, such as air conditioning waste heat [17,18] and industrial heat [19,20]. Some studies have analyzed the correlation between anthropogenic heat and thermal environment changes [21,22]. ...
Article
Research on the impact of anthropogenic heat discharge in a thermal environment is significant in climate change research. Central heating is more common in the winter in Northeast China as an anthropogenic heat. This study investigates the impact of central heating on the thermal environment in Shenyang, Changchun, and Harbin based on multi-temporal land surface temperature retrieval from remote sensing. An equivalent heat island index method was proposed to overcome the problem of the method based on a single-phase image, which cannot evaluate all the central heating season changes. The method improves the comprehensiveness of a thermal environment evaluation by considering the long-term heat accumulation. The results indicated a significant increase in equivalent heat island areas at night with 22.1%, 17.3%, and 19.5% over Shenyang, Changchun, and Harbin. The increase was significantly positively correlated with the central heating supply (with an R-value of 0.89 for Shenyang, 0.93 for Changchun, and 0.86 for Harbin; p < 0.05). The impact of central heating has a more significant effect than the air temperature. The results provide a reference for future studies of urban thermal environment changes.
... Refinement climate simulation requires finer product, and generating AHF data with higher spatial resolution (e.g., hundreds of meters) may be a vital step in the climate simulation research. For example, numerous previous works simulated and proved the impact of anthropogenic heat emissions on urban climate with multiple physics-based models (e.g., BEM, WRF; Salamanca et al., 2014;Salamanca et al., 2013;de Munck et al., 2013;Li et al., 2013). In this case, the development of a global AHF dataset with high spatial resolution and precision will facilitate the improvement of accuracy in climate simulation. ...
Article
Anthropogenic heat emission affects the surface energy budget, energy exchange, and urban heat islands. Accurate quantification of anthropogenic heat flux (AHF) is significant for understanding the urban climate and improving human settlements. However, accurate global AHF dataset with high spatial heterogeneity (e.g., hundreds of meters) is still limited in practical application. In this study, we integrated multi-source data (global energy consumption statistics, nighttime light data, LandScan population density data, and regional AHF data) to model the global surface 500 m × 500 m AHF in 2016. The evaluation results indicate that the R² between the global AHF integrated with regional fine data (GAHF) and the national energy consumption is 0.77, which is higher than the R² (0.70) between the initial modeled AHF (GAHForg) and the national energy consumption. Besides, the mean R² of GAHF and comparison dataset (0.84) is slightly higher than that of GAHForg (0.83) on the regional scale. On the grid scale, the correlation coefficient of GAHF and comparison dataset is improved compared with that of GAHForg. The absolute difference between GAHForg and China's surface AHF (CAHF) is 9.36 W·m⁻², and that of between GAHF and CAHF is 0.97 W·m⁻². These results demonstrate the feasibility of the global AHF estimation scheme, and the reliability of the global AHF estimates. The results can serve the global environment and climate change research.
... In this case, the buildings were revealed to be generated heats [3] while these heats were mostly generated from the machinery using inside the buildings. De Munck and her team in 2013 [4] showed that increasing the air conditioner uses and the system for cooling the buildings are largely emitting the waste heats to the atmosphere. The waste heats released by the air conditioners at the nighttime were ~ 3 ~ ...
Preprint
Full-text available
Buildings can generate heats which are mostly generated from the machinery using inside the buildings, and these heats generally released to the atmosphere. Buildings can also block the wind flow by their canopies and trap the heat by using low albedo materials. These causes pointedly contribute to urban heat island and greenhouse effects. Likewise, urban development and building construction in Cambodia are growing rapidly. The construction has been recognized as a key development sector while thousands of buildings are being built and have been operated in the main cities. However, those buildings mostly have not been considered to incorporate sustainability concepts while the major final energy consumers in the country are buildings. The buildings' energy consumption is also projected to increase more than double until 2040. Hence, sustainable building promotion in Cambodia is necessary, and sustainable building criteria are completely required. This research aims to find out significant sustainable building criteria for Cambodia and focused on planning and design criteria because having proper planning and design is a smart start leading to achieving building sustainability in all stages. This research used the Delphi methods to validate the relevant sustainable building criteria available in the literature and then select the significant ones for Cambodia based on the Delphi consensus. The results showed that ninety-nine consensus planning and design criteria were found to be significant for sustainable buildings in Cambodia.
... An early study in the center business district carried out by Kikegawa et al. (2003) reported that the daily cooling electricity demands increased 5.66%/℃ in summer days when daily maximum temperature exceeds 31℃. As a kind of vicious circle, the heat from air condition (AC) system was found to increase the urban air temperature in Wuhan (Wen & Liang, 2009), Paris (de Munck et al., 2013), Madrid (Salamanca et al., 2012) and Singapore (Mughal et al., 2019;Mughal et al., 2020. The vehicle heat (VH), which generally recognized as the second largest portion of the AH (Quah et al., 2012;Smith et al., 2009;Ji et al., 2022), was found as the major source of AH during Summer in Sao Paulo, Brazil (Ferreira et al., 2011) and Toulouse, France (Pigeon et al., 2007). ...
Article
Studies have been conducted globally on urban heat countermeasures utilizing Weather Research and Forecasting (WRF) numerical modeling system. Yet, the effects of vehicle heat (VH) on near-surface air temperature in Japanese cities were not clarified. In this study, the WRF Building Effect Parameterization and Building Energy Model (BEP-BEM) coupled with local climate zones (LCZs) was adopted for simulating the influences of VH on the urban climate over Sendai, Japan. To do so, we proposed a novel method to estimate the hourly VH for LCZs via open-source data. Integrating VH and specific urban canopy parameters (UCPs) into BEP-BEM, the climate model was established and then validated with the observed data. Based on that, effects of various urban heat countermeasures were analyzed at a high spatial resolution. It was found that eliminating the vehicle heat contributes up to 0.12°C to urban heat mitigation, as the most effective countermeasures for the compact areas of city center. This study provided a feasible and reliable workflow to quantitatively evaluate urban heat mitigation strategies at high spatial resolution, specifically for reducing VH in Japanese cities, that can support related urban planners and decision makers for implementing targeted urban heat mitigation strategies.
... In this case, the buildings were revealed to be generated heats [3] while these heats were mostly generated from the machinery using inside the buildings. De Munck and her team in 2013 [4] showed that increasing the air conditioner uses and the system for cooling the buildings are largely emitting the waste heats to the atmosphere. The waste heats released by the air conditioners at the nighttime were ~ 3 ~ ...
Preprint
Full-text available
Buildings can generate heats, which are mostly generated from the machinery using inside the buildings, while these waste heats generally released into the atmosphere. Buildings can also block the wind flow by their canopies and trap the heat by using low albedo materials. These causes pointedly contribute to urban heat island and greenhouse effects. Likewise, urban development and building construction in Cambodia are growing rapidly. The construction has been recognized as a key development sector while thousands of buildings are being built and have been operated in the main cities. However, those buildings mostly have not been considered to incorporate sustainability concepts while the major final energy consumers in the country are buildings. The buildings' energy consumption is also projected to increase more than double until 2040. Hence, sustainable building promotion in Cambodia is necessary, and sustainable building criteria are completely required. This research aims to find out significant sustainable building criteria for Cambodia and focused on planning and design criteria because having proper planning and design is a smart start leading to achieving building sustainability in all stages. This research used the Delphi methods to validate the relevant sustainable building criteria available in the literature and then select the significant ones for Cambodia based on the Delphi consensus. The results showed that ninety-nine consensus planning and design criteria were found to be significant for sustainable buildings in Cambodia.
... Moreover, the UHI is shown to increase energy consumption for air-conditioning in cities, which in turn results in extra release of waste heat and air pollutants into the atmosphere during energy production (Akbari et al., 2001). All this together causes an additional mean temperature increase of up to 2 • C in cities (Ohashi et al., 2007;Salamanca et al., 2011;de Munck et al., 2013); an ensuing degradation of air quality associated with urban smog formation (Akbari et al., 2001;Akbari, 2005); and substantial CO 2 emissions, which might impede human efforts towards a sustainable low-carbon society. In the worst emission scenario, when the UHI is taken into account, the total economic costs of climate change for cities are estimated to reach 10.9 % of GDP by 2100 (Estrada et al., 2017). ...
Book
To what extent cities can be made sustainable under the mega-trends of urbanization and climate change remains a matter of unresolved scientific debate. Our inability in answering this question lies partly in the deficient knowledge regarding pivotal humanenvironment interactions. Regarded as the most well documented anthropogenic climate modification, the urban heat island (UHI) effect – the warmth of urban areas relative to the rural hinterland – has raised great public health concerns globally. Worse still, heat waves are being observed and are projected to increase in both frequency and intensity, which further impairs the well-being of urban dwellers. Albeit with a substantial increase in the number of publications on UHI in the recent decades, the diverse urban-rural definitions applied in previous studies have remarkably hampered the general comparability of results achieved. In addition, few studies have attempted to synergize the land use data and thermal remote sensing to systematically assess UHI and its contributing factors. Given these research gaps, this work presents a general framework to systematically quantify the UHI effect based on an automated algorithm, whereby cities are defined as clusters of maximum spatial continuity on the basis of land use data, with their rural hinterland being defined analogously. By combining land use data with spatially explicit surface skin temperatures from satellites, the surface UHI intensity can be calculated in a consistent and robust manner. This facilitates monitoring, benchmarking, and categorizing UHI intensities for cities across scales. In light of this innovation, the relationship between city size and UHI intensity has been investigated, as well as the contributions of urban form indicators to the UHI intensity. This work delivers manifold contributions to the understanding of the UHI, which have complemented and advanced a number of previous studies. Firstly, a log-linear relationship between surface UHI intensity and city size has been confirmed among the 5,000 European cities. The relationship can be extended to a log-logistic one, when taking a wider range of small-sized cities into account. Secondly, this work reveals a complex interplay between UHI intensity and urban form. City size is found to have the strongest influence on the UHI intensity, followed by the fractality and the anisometry. However, their relative contributions to the surface UHI intensity depict a pronounced regional heterogeneity, indicating the importance of considering spatial patterns of UHI while implementing UHI adaptation measures. Lastly, this work presents a novel seasonality of the UHI intensity for individual clusters in the form of hysteresis-like curves, implying a phase shift between the time series of UHI intensity and background temperatures. Combining satellite observation and urban boundary layer simulation, the seasonal variations of UHI are assessed from both screen and skin levels. Taking London as an example, this work ascribes the discrepancies between the seasonality observed at different levels mainly to the peculiarities of surface skin temperatures associated with the incoming solar radiation. In addition, the efforts in classifying cities according to their UHI characteristics highlight the important role of regional climates in determining the UHI. This work serves as one of the first studies conducted to systematically and statistically scrutinize the UHI. The outcomes of this work are of particular relevance for the overall spatial planning and regulation at meso- and macro levels in order to harness the benefits of rapid urbanization, while proactively minimizing its ensuing thermal stress.
... Moreover, heat waste from air conditioning may further exacerbate UHI. For example, a study focused on Paris has shown that heat waste from air-conditioning increases urban temperature by 0.5 • C and that by doubling air-conditioning heat waste, urban temperature increases by 2 • C [27]. Table 1 Benefits and costs of green walls. ...
Article
Urban Heat Island (UHI) is a worldwide threat affecting building energy demand, public health, and energy security. Green wall deployment can simultaneously positively impact UHI and building energy demand depending on climate zones. According to the different climate zones worldwide, the present systematic literature review (SLR) investigates the direct effects of green wall installation on building energy use and UHI. 1325 articles were screened, and 51, corresponding to 647 case studies, were selected after removing those with methodological or statistical heterogeneity. The effects of green wall deployment have been explored according to cooling and heating season, weather conditions, daytime, nighttime, green wall typology, green wall orientation, and application scale. The performed analyses show that green walls: (1) can reduce heating and cooling building energy demand up to 16.5% and ∼51%, respectively, and mitigate UHI up to ∼5 °C in all the investigated climate zones; (2) can decrease to the greatest extent building energy needs when applied in low-density urban contexts where they can be installed on the entire building. Besides, when applied to a single façade, South orientation should be preferred in most climate zones to maximize building energy saving; (3) have the best UHI mitigating potential—up to 8 °C—in highly urbanized areas featured with narrow streets surrounded by high-rising buildings. Altogether, green walls are a fit-all solution to reduce building energy demand and mitigate UHI, providing healthier living conditions. However, further research is necessary to include quantifiable and unquantifiable effects omitted in the current study.
... Studies by Qu et al. (2014) over the continental United States found that DTR had increased slight to moderately over different parts of the USA, and the change had both seasonal and regional patterns. Not only the physical processes, human being also directly contributes to raise temperature of a city with increasing use of air conditioner (de Munck et al. 2013;Salamanca et al. 2014). It may be noted that higher temperature may lead to imposed risks to the elderly population as well as increase of different seasonal diseases (Wu et al., 2009) in the urban areas. ...
Article
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An attempt has been made, in this paper, to understand the characteristics and trends of temperatures of Kolkata, India, by using the temperature extremes, as recommended by Expert Team on Climate Change Detection and Indices (ETCCDI), and other relevant indices. For the purpose, daily maximum, minimum, and mean temperatures (1969–2012) of Alipore and Dum Dum observatories have been used. Both parametric (linear regression test) and non-parametric (Mann–Kendall test) have been done to detect the change, and Sen’s slope estimator has been used to establish the degree of change. To detect homogeneity of the dataset, four homogeneous tests have been applied. Long-term (1969–2012) trends of extreme temperature indices like TXa, TXn, TMa, TNx, TNa, and TNn of monthly, seasonal, and annual time steps significantly detect a positively increasing trend. The rate is found to be the maximum at Dum Dum. Long-term trends of TXa, TNx, TNa, TNn, and TMa indicate an average positive temperature change of 0.30 °C/decade to 0.62 °C/decade, and in extreme cases over 0.65 °C/decade. Results also point out that in the monsoon and the post-monsoon seasons most of the trends are noticeable. In most of the cases, rates of positive temperature trends have been lower in recent time period (series II, 1985–2012), compared to the past time period (series I, 1969–1995). Distribution of the relative temperature indices also points out presence of asymmetric distribution between warm nights and cold days, and cold nights. Around three times more positive increase of warm nights has been noticed at Dum Dum station during 1971–1980 and 2001–2010.
... The present study assesses the ability of the LSM-UCM approach to downscale ERA5 reanalysis, the fifth, and latest, generation reanalysis from the European Centre for Medium-Range Weather Forecasts to resolutions of a few kilometers over dense urban areas. Specifically, we analyze the added value of the Météo-France SURFEX (Surface Externalisée) 105 surface modelling platform (Le Moigne, 2018) in improving the simulation of the UHI and SUHI over Paris, a European mega-city characterized by a well-known strong urban heat island effect (e.g., Sarkar & De Ridder, 2011;De Munck et al., 2013;Hamdi et al., 2015;Lemonsu et al., 2015;Daniel et al., 2019). SURFEX is particularly relevant in this context since it has shown to perform particularly well in offline urban simulations (e.g., Hamdi et al., 2015;Lemonsu et al., 2015;Nogueira & Soares, 2019;Nogueira et al., 2020b). ...
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Cities concentrate people, wealth, emissions, and infrastructures, thus representing a challenge and an opportunity for climate change mitigation and adaptation. This places an urgent demand for accurate urban climate projections to help organizations and individuals making climate smart-decisions. However, most of the state-of-the-art global and regional climate models have an oversimplified representation of (or completely neglect) urban climate processes. Here, we use the city of Paris as a case study to show that this is the case for the fifth (and latest) generation reanalysis from the European Centre for Medium-Range Weather Forecasts (ERA5) and for simulations employing the widely used bulk bare rock approach to urban climate parameterization. Subsequently, we leveraged on the hourly resolution of ERA5 and the Satellite Application Facility Land Surface Analysis (LSA-SAF) land surface temperature product to demonstrate the significant added value of employing the SURFEX land-surface model coupled to Town Energy Balance (TEB) urban canopy model in simulating the Parisian Surface Urban Heat Island (SUHI) during daytime and the urban heat island during both daytime and nighttime. Our results showed the significant added value of SURFEX-TEB in reproducing the observed daytime and nighttime Parisian urban heat island effect. An annual average bias magnitude reduction of 0.5 °C was observed for daytime and around 1.5 °C for nighttime when compared to ERA5 and bare rock approach. Also, SURFEX-TEB revealed an overall better performance in reproducing the observed daytime SUHI, whilst the added value of SURFEX-TEB was lower during nighttime (but still slightly better than ERA5 and the bare rock approach), due to the lack of land-atmosphere feedbacks in the proposed offline framework. Finally, the offline SURFEX-TEB framework applied here demonstrates the ability to simulate the urban climate, which is an asset to build urban climate projections that allow the development of mitigation and adaptation strategies.
... As we know, buildings generally have impacts on environments and human health, and their impacts have been seen clearly in cities [35]. According to the study of De Munck and her colleagues, increasing the use of air conditioning systems for cooling inside buildings generally releases the waste heat into the atmosphere [36]. For example, the waste heat from air conditioners at night can raise urban temperature by more than 1 • C [35,37]. ...
Article
Full-text available
Data collection and review are the building blocks of academic research regardless of the discipline. The gathered and reviewed data, however, need to be validated in order to obtain accurate information. The Delphi consensus is known as a method for validating the data. However, several studies have shown that this method is time-consuming and requires a number of rounds to complete. Until now, there has been no clear evidence that validating data by a Delphi consensus is more significant than by a general consensus. In this regard, if data validation between both methods are not significantly different, then just using a general consensus method is sufficient, easier, and less time-consuming. Hence, this study aims to find out whether or not data validation by a Delphi consensus method is more significant than by a general consensus method. This study firstly collected and reviewed the data of sustainable building criteria, secondly validated these data by applying each consensus method, and finally made a comparison between both consensus methods. The results showed that seventeen of the valid criteria obtained from the general consensus and reduced by the Delphi consensus were found to be inconsistent for sustainable building assessments in Cambodia. Therefore, this study concludes that using the Delphi consensus method is more significant in validating the gathered and reviewed data. This experiment contributes to the selection and application of consensus methods in validating data, information, or criteria, especially in engineering fields.
... (2) Uncertainties also exist in various urban model parameters (Chen et al., 2021), including those related to anthropogenic heat (e.g., air conditioning; De Munck et al., 2013;Xu et al., 2018), landscape irrigation, building wall function (determining indoor-outdoor heat exchange), and urban spatial heterogeneity (e.g., building/vegetation horizontal and vertical distribution). Recent efforts in developing high-resolution urban-model parameters such as LCZ (Stewart et al., 2014) and WUDAPT (Ching et al., 2019) are an excellent step forward. ...
Article
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Urban environments lie at the confluence of social, cultural, and economic activities and have unique biophysical characteristics due to continued infrastructure development that generally replaces natural landscapes with built-up structures. The vast majority of studies on urban perturbation of local weather and climate have been centered on the urban heat island (UHI) effect, referring to the higher temperature in cities compared to their natural surroundings. Besides the UHI effect and heat waves, urbanization also impacts atmospheric moisture, wind, boundary layer structure, cloud formation, dispersion of air pollutants, precipitation, and storms. In this review article, we first introduce the datasets and methods used in studying urban areas and their impacts through both observation and modeling and then summarize the scientific insights on the impact of urbanization on various aspects of regional climate and extreme weather based on more than 500 studies. We also highlight the major research gaps and challenges in our understanding of the impacts of urbanization and provide our perspective and recommendations for future research priorities and directions. Citation: Qian, Y., and Coauthors, 2022: Urbanization impact on regional climate and extreme weather: Current understanding, uncertainties, and future research directions. Adv. Atmos. Sci., https://doi.org/10.1007/s00376-021-1371-9. Article Highlights: • As urban areas expand and populations grow, we urgently need to better understand cities and their interactions with weather and climate. • Urbanization can impact heat waves, atmospheric moisture, clouds, wind patterns, air pollution, boundary-layer, precipitation, and storms. • Research gaps due to complexity of urban areas and deficiencies in current methods are identified and future priorities are highlighted.
... Depuis le début des années 2000, de nombreuses études ont été réalisées avec Meso-NH et TEB pour la modélisation couplée et à haute résolution du climat urbain. Cette configuration a porté essentiellement sur des exercices de modélisation à l'échelle événementielle pour étudier de nombreux phénomènes tels que l'ICU (Pigeon et al., 2006), l'impact des rejets de chaleur anthropiques (De Munck et al., 2013a), le couplage avec la couche limite atmosphérique , les circulations de brises et de panaches urbains (Lemonsu et Masson, 2002 ;Hidalgo et al., 2008), le transport et la dispersion des polluants d'origine urbaine (Sarrat et al., 2006), etc. Plus récemment, Schoetter et al. (2020) et Gardes et al. (2020) ont produit avec le système Meso-NH-TEB une climatologie de référence d'ICU jusqu'à 250 m de résolution sur un ensemble de villes françaises, en particulier sur la région parisienne, dont les données sont exploitées dans le cadre de la thèse (et présentées en sous-section 2.3.2). ...
Thesis
Full-text available
Par ses caractéristiques physiques et géométriques, l'environnement urbain représente une modification profonde du milieu naturel. Ces transformations engendrent des impacts environnementaux et sociétaux déjà perceptibles, qui pourraient s'accentuer avec le changement climatique. La compréhension et l'évaluation de ces impacts et leurs évolutions futures nécessitent des outils de simulation et des scénarios climatiques adaptés à l'échelle de la ville. Certains modèles régionaux de climat atteignent aujourd'hui de très hautes résolutions horizontales permettant de représenter les villes et évaluer les impacts par une descente d'échelle dynamique. Mais leur mise en œuvre coûteuse limite la durée des simulations et le nombre de scénarios étudiés. D'autres méthodes, plus légères, permettent d'améliorer la résolution de ces modèles par une descente d'échelle statistique mais ne représentent pas les rétroactions de la ville sur le climat local. Cette thèse propose une méthodologie pour l'évaluation des impacts du changement climatique en ville, en termes de climat urbain, confort thermique, et demande énergétique, avec la région parisienne comme cas d'étude. Une première étape a consisté à faire un état des lieux de la climatologie urbaine de la région, à partir de longues séries d'observations spatialisées de température de surface, de température de l'air en surface et de précipitation. Des indicateurs de climat urbain innovants ont été proposés et calculés, pour l'analyse du climat passé de Paris, puis remobilisés dans la suite de la thèse pour l'évaluation des modèles et l'étude des évolutions avec le changement climatique. Dans une seconde étape, une méthode de descente d'échelle statistico-dynamique a été développée et testée sur la région parisienne pour combiner les tendances climatiques régionales avec l'effet thermique de la ville sur son environnement local. Les projections climatiques fournies par les modèles du programme EURO-CORDEX 0,11° de résolution) ont été corrigées quotidiennement par des champs atmosphériques issus d'une modélisation à haute résolution du climat urbain. Cette modélisation a été réalisée, dans une précédente étude, avec le modèle Meso-NH couplé au modèle de canopée urbaine TEB, pour un ensemble de situations météorologiques représentatives des types de temps locaux. Une évaluation sur la période passée 2000-2008 a montré la capacité de la méthode à représenter la variabilité spatiale et temporelle des îlots de chaleur urbains parisiens. Enfin, les forçages climatiques produits par cette méthode, avec une résolution spatiale kilométrique et une fréquence temporelle tri-horaire, ont été appliqués à la plateforme de modélisation des surfaces continentales SURFEX incluant TEB. Des simulations du climat urbain de la région parisienne ont été réalisées en continu sur la période 1976-2099 selon le scénario d'émission RCP8,5 ; TEB étant capable de simuler différents indicateurs d'impacts relatifs à la température, le confort thermique et la consommation d'énergie des bâtiments. La méthodologie complète a été comparée à des approches plus simples, sans descente d'échelle des forçages climatiques pour la prise en compte préalable des effets urbains. Cette étude a permis d'évaluer la sensibilité des résultats sur la période historique, et de montrer les apports de la méthodologie proposée pour l'évaluation des impacts. Les résultats ont ensuite été analysés sur tout le XXIe siècle pour quantifier l'évolution du climat urbain et des impacts associés sur la région parisienne sous l'influence du changement climatique.
... As a result, a marked annual increase in the environmental temperature of Taipei Basin has been observed [1], resulting in a heat island effect. Similar problems have been observed in large cities worldwide [2][3][4][5]. The cooling towers of buildings have been used as a heat exchange medium between air conditioners and outdoor air and make the cooling cycle more efficient for air condensation in subtropical areas. ...
Article
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Using circulating groundwater to cool air-conditioning is not new in high latitude regions but difficult in subtropical areas. Different from only using fans to remove the heat from indoor air for drier air in the high latitude region, the latent heat inside the humid air in subtropical areas makes the operation more difficult. Latent heat inside the humid air must remove away by air-conditioning including compressor and fan for cooling indoor air, which means more electrical power is required for the operation. To save total electrical power for the air-conditioning system is the main goal of this study. To use the advantage of groundwater with lower temperature to lower down the work of compressor, this research compared two ways, close/open types of water/groundwater circulation, both using groundwater to remove the heat generated by a 15RT (45 kW) air-conditioning. Full-scale tests and simulations were performed in this study to evaluate the efficiency of transferring the heat produced by air-conditioning systems to stably flowing groundwater in a grave stratum under Taipei Basin. With a closed circulating cooling water system, this study found that a 15RT air conditioner could only operate continuously for 4 h before it had to be shut down due to overheating. Additionally, groundwater must carry the heat away within the following 20 h. In changing the closed circulating water system to an open one, a system that uses a circulatory method to extract groundwater upwards and conduct heat exchange with an air conditioning system can enable the continuous operation of such a system with the same heat production condition. Numerical simulations for the heat dissipation behavior of two circulatory systems were performed herein. The results verified the aforementioned phenomena observed from both tests. The result showed both systems can provide air-conditioning working well. The total electrical power for a 15RT air-conditioning in sub-tropical areas can be reduced by 22% using circulating groundwater. Considering the system optimization, the total power consumption can be reduced by about 28%.
... Buildings generally have impacts on environments and human health and their impacts have been seen clearly in cities [1]. According to the study of De Munck and her colleagues, increasing the use of air conditioning systems for cooling inside the buildings is generally releasing the waste heat into the atmosphere [2]. For example, the waste heat from air conditioners at night can raise urban temperature by more than 1°C [1,3]. ...
Preprint
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Published data or available literature on sustainable building plan-design, construction, performance, and renovation criteria have covered some stages or some parts of each stage. These data usually have been published partially in many different papers―there have not been any papers that published these data together. Hence, this paper aims to collectively review these data and publish them together. The collection and review of these data were carried out by our twenty-five team members who specialized in sustainable urban, architectural, and civil engineering and construction management. The gathered and reviewed outputs were combined and validated based on a general group consensus. This consensus decision-making proceeded through two major group meetings with several follow-up meetings. The first major meeting was to combine and improve the gathered reviewed sustainable building criteria for Cambodia. The second major meeting was to validate the improved reviewed sustainable building criteria for Cambodia. The several follow-up meetings were to discuss the relevance and importance of the validated data “criteria and their classifications and descriptions” in all stages and more focused on their importance and applicability to Cambodia. The collective reviewed data in this paper would be useful to researchers in the fields. They could also be useful collective knowledge and information for policymakers from governmental agencies and development partners, particularly for sustainable building and construction companies.
... Negative effects are also expected concerning the energy consumption for cooling indoor building environments (Hassid et al., 2000), especially for industrial buildings located in hot-spot areas. In addition, while air conditioning usage cool the insides of industrial buildings, it releases waste heat to the lower part of the urban atmosphere, thus conditioning the local climate at the scale of the city (De Munck et al., 2012). It is therefore essential to plan heatrelated mitigation interventions with particular attention to some industrial sites which, as highlighted in our study, are important heat sources that determine critical intra-urban thermal hot-spot areas. ...
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This study was focused on the metropolitan area of Florence in Tuscany (Italy) with the aim to provide a functional spatial thermal anomaly indicator obtained throughout a thermal summer and winter hot-spot detection. The hot-spot analysis was performed by applying Getis-Ord Gi* spatial statistics to Land Surface Temperature (LST) layers, obtained from Landsat 8 remote sensing data during the 2015–2019 daytime summer and winter period, to delimitate summer hot- and cool-spots, and winter warm- and cold-spots. Further, these ones were spatially combined thus obtaining a comprehensive summer-winter Thermal Hot-Spot (THSSW) spatial indicator. Winter and summer mean daily thermal comfort profiles were provided for the study area assessing the Universal Thermal Climate Index (UTCI) by using meteorological data available from seven local weather stations, located at a maximum distance of 350 m from industrial sites. A specific focus on industrial sites was carried out by analyzing the industrial buildings characteristics and their surrounding areas (50 m buffer), through the following layers: industrial building area (BA), surface albedo of buildings (ALB), impervious area (IA), tree cover (TC), and grassland area (GA). The novel THSSW classification applied to industrial buildings has shown that about 50% of the buildings were located in areas characterized by summer hot-spots. Increases in BA and IA revealed warming effects on industrial buildings, whereas increases in ALB, TC, and GA disclosed cooling effects. A decrease of about 10% of IA replaced by TC and GA was associated with about 2 °C decrease of LST. Very strong outdoor heat stress conditions were observed during summer daytime, whereas moderate winter outdoor cold stress conditions were recorded during nighttime until the early morning. The thermal spatial hot-spot classification in industrial areas provides a very useful source of information for thermal mitigation strategies aimed to reduce the heat-related health risk for workers.
... They have found that a VCC with a COP of 6 at air source temperature of 30 • C, is subjected to a COP reduction up to 5.6-4.5 when the air temperature rises into the range 2 • C-8 • C due to UHI; • #3 the UHI is exacerbated by the heat rejected from the air conditioners causing a local temperature increase resulting in a local micro-warming (UHI spots). De Munck et al. (De Munck et al., 2013) have estimated that air condensers cause a 0.5 • C increase in Paris air temperature and this value can reach 2 • C if the VCCs' will be doubled. Despite, the use of VCCs affects negatively the heat wave as it has happened in Shanghai where it results more intense from 1998 to 2003, at the same time the mortality decreases because of the greater air conditioning systems diffusion (NWS, 2020). ...
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The greenhouse gas emissions caused by human activities determined an increase of global mean temperature during last decade. The growing heating, cooling, ventilation and refrigeration demands for residential, commercial and industrial sectors represent the major contributor to environmental emissions. The environmental analysis represents a good strategy for evaluation, comparison and selection of energy supply system on the basis of users’ demands. The global warming potential of energy conversion devices is usually analysed by considering energy consumption, indirect and direct greenhouse gas emissions caused by refrigerants leakages through the well-known Total Equivalent Warming Impact index, TEWI. In this paper a detailed and extended version of TEWI index, Expanded Total Equivalent Warming Impact (ETEWI) parameter, is proposed to calculate CO2 equivalent emissions from direct and indirect contributions in the HVAC&R sectors. The standard TEWI index contributes are revisited to determine the emissions by an accurate evaluation of direct refrigerant leakages and by detailing the indirect emissions caused by electric energy consumption factor. In addition, new emissions’ contributions are investigated. The novelty of this approach can be summarised in two key-points: the possibility of analysing the environmental impact of both electric and gas driven devices and the definition of an innovative environmental parameter to take into account the direct/indirect contributions of the Urban Heat Island effect and the indirect CO2 emissions due to losses in distribution and transportation pipelines that supply natural-gas to energy conversion systems.
... Even though the buildings provide a lot of benefits to residents and visitors, as well as businessmen and other groups, the research shows that the buildings can generate heats [1] whereas most of the heats are generated from the types of machinery using inside the buildings. Increasing the use of air conditioning systems for cooling inside the buildings is generally releasing the waste heat into the atmosphere [2]. The waste heat from air conditioners at night can raise the urban temperature by more than 1°C [1,3]. ...
Preprint
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Published data or available literature on planning, design, construction, performance, and renovation criteria for sustainable buildings have been focused on some stages, such as design and construction stages, or some parts of each stage due to a limited number of collaborative scholars or the scope of their research. These data usually have been published scattered or partially presented in many different papers―there have not been any papers published these data, all-stage ‘plan-design, construction, performance, and renovation’ criteria, together. Hence, this paper aims to collect and review these data and publish them together. The data collection and review were conducted by our team, 25 members, who specialized in sustainable urban, architectural, and civil engineering and construction management. The review outputs were combined and then validated based on a group consensus. This consensus-based validation proceeded through several times of meetings. These meetings extensively discussed the relevance and importance of the validated data (main criteria and sub-criteria, including their descriptions, of sustainable building in all stages) and more focused on their importance and applicability to the Cambodian context. The collective and review data demonstrated in this paper would be useful to researchers in the fields. They could also be useful collective knowledge and information for policymakers from the governments and development partners, as well as for architecture and building construction companies.
... However, other urban characteristics can also play an important role. Urban materials [15,16], the presence of vegetation [17][18][19], and anthropogenic heat emissions [20,21] can modify significantly OTC levels inside the urban area. ...
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Urban areas are a high-stake target of climate change mitigation and adaptation measures. To understand, predict and improve the energy performance of cities, the scientific community develops numerical models that describe how they interact with the atmosphere through heat and moisture exchanges at all scales. In this review, we present recent advances that are at the origin of last decade's revolution in computer graphics, and recent breakthroughs in statistical physics that extend well established path-integral formulations to non-linear coupled models. We argue that this rare conjunction of scientific advances in mathematics, physics, computer and engineering sciences opens promising avenues for urban climate modeling and illustrate this with coupled heat transfer simulations in complex urban geometries under complex atmospheric conditions. We highlight the potential of these approaches beyond urban climate modeling, for the necessary appropriation of the issues at the heart of the energy transition by societies.
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The changes in human behaviour associated with the spread of COVID-19 infections have changed the urban environment. However, little is known about the extent to which they have changed the urban climate. We quantitatively evaluated these effects using a unique method that integrates real-time human population data (social big data) with an urban climate model. The results showed that in an office district in the city centre of Tokyo, the biggest metropolis in the world, under a significantly reduced population, electricity consumption (CO 2 emissions) would be 30% and anthropogenic heat emission would be 33% of pre-COVID levels (without the stay-at-home advisories). This resulted in a temperature decrease of about 0.2°C, representing about 10% of the past greenhouse gas-induced warming in Tokyo. This method can be benchmarked and then applied to worldwide. The results suggest that changes in human behaviour can represent an adaptation strategy to climate change in cities.
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Chapter
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Published data or available literature on planning, design, construction, performance, and renovation criteria for sustainable buildings have been focused on some stages, such as design and construction stages, or some parts of each stage due to a limited number of collaborative scholars or the scope of their research. These data usually have been published scattered or partially presented in many different papers―there have not been any papers published these data, all-stage ‘plan-design, construction, performance, and renovation’ criteria, together. Hence, this paper aims to collect and review these data and publish them together. The data collection and review were conducted by our team, 25 members, who specialized in sustainable urban, architectural, and civil engineering and construction management. The review outputs were combined and then validated based on a group consensus. This consensus-based validation proceeded through several times of meetings. These meetings extensively discussed the relevance and importance of the validated data (main criteria and sub-criteria, including their descriptions, of sustainable building in all stages) and more focused on their importance and applicability to the Cambodian context. The collective and review data demonstrated in this paper would be useful to researchers in the fields. They could also be useful collective knowledge and information for policymakers from the governments and development partners, as well as for architecture and building construction companies.
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To improve prediction of the meteorological fields inside the street canyon with TEB, a new version has been developed, following the methodology described in a companion paper (Masson et al. 2009). It resolves the surface boundary layer inside and above urban canopy by introducing a drag force approach. This new version is tested offline in a street canyon. Results are compared with the original single­layer version of TEB and with measurements within and above the street canyon. Results show that this new version produces profiles of wind speed, friction velocity, turbulent kinetic energy, turbulent heat flux, and potential temperature that are more consistent with observations. Furthermore, this new version can still be easily coupled to mesoscale meteorological models.
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Using the Montreal Urban Snow Experiment (MUSE) 2005 database, surface radiation and energy exchanges are simulated in offline mode with the Town Energy Balance (TEB) and the Interactions between Soil, Biosphere, and Atmosphere (ISBA) parameterizations over a heavily populated residential area of Montreal, Quebec, Canada, during the winter–spring transition period (from March to April 2005). The comparison of simulations with flux measurements indicates that the system performs well when roads and alleys are snow covered. In contrast, the storage heat flux is largely underestimated in favor of the sensible heat flux at the end of the period when snow is melted. An evaluation and an improvement of TEB’s snow parameterization have also been conducted by using snow property measurements taken during intensive observational periods. Snow density, depth, and albedo are correctly simulated by TEB for alleys where snow cover is relatively homogeneous. Results are not as good for the evolution of snow on roads, which is more challenging because of spatial and temporal variability related to human activity. An analysis of the residual term of the energy budget—including contributions of snowmelt, heat storage, and anthropogenic heat—is performed by using modeling results and observations. It is found that snowmelt and anthropogenic heat fluxes are reasonably well represented by TEB–ISBA, whereas storage heat flux is underestimated.
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The effect of heat-island reduction (HIR) strategies on annual energy savings and peak-power avoid-ance of the building sector of the Greater Toronto Area is calculated, using an hourly building energy simulation model. Results show that ratepayers could realize potential annual energy savings of over $11M from the effects of HIR strategies. The residential sector accounts for over half (59%) of the total savings, offices 13% and retail stores 28%. Savings from cool roofs are about 20%, shade trees 30%, wind shielding of trees 37%, and ambient cooling by trees and reflective surfaces 12%. These results are pre-liminary and highly sensitive to the relative price of gas and electricity. Potential annual electrticity sav-ings are estimated at about 150 GWh and potential peak power avoidance at 250 MW. Published by Elsevier Ltd.
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A formulation to include prognostic atmospheric layers in offline surface schemes is derived from atmospheric equations. Whereas multilayer schemes developed previously need a complex coupling between atmospheric-model levels and surface-scheme levels, the coupling proposed here remains simple. This is possible because the atmospheric layers interacting with the surface scheme are independent of the atmospheric model that could be coupled above. The surface boundary layer (SBL; both inside and just above the canopy) is resolved prognostically, taking into account large-scale forcing, turbulence, and, if any, drag and canopy forces and surface fluxes. This formulation allows one to retrieve the logarithmic law in neutral conditions, and it has been validated when coupled to a 3D atmospheric model. Systematic comparisons with 2-m observations and 10-m wind have been made for 2 months. The SBL scheme is able to model the 2-m temperature accurately, as well as the 10-m wind, without any use of analytical interpolation. The largest improvement takes place during stable conditions (i.e., by night), during which analytical laws and interpolation methods are known to be less accurate, and in mountainous areas, in which nocturnal low-level flow is strongly influenced by surface cooling. The prognostic SBL scheme is shown to solve the nighttime physical disconnection problem between surface and atmosphere models. The inclusion of the SBL into the urban Town Energy Balance scheme is presented in a paper by Hamdi and Masson in which the ability of the method to simulate the profiles of both mean and turbulent quantities from above the building down to the road surface is shown using data from the Basel Urban Boundary Layer Experiment (BUBBLE). The proposed method will allow the inclusion of the detailed physics of the multilayer schemes (e.g., the interactions of the SBL flow with forest or urban canopy) into a single-layer scheme that is easily coupled with atmospheric models.
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This paper investigates the effect that increased air temperature due to the London heat island has on the effectiveness of stack night ventilation strategies for office buildings. Stack ventilation was investigated as the most suitable night ventilation strategy because this is largely independent of wind variations affected by local urban morphology. The paper presents a summary of the results of air temperature measurements carried out in London in 1999/2000 which were used to quantify the London Urban Heat Island Intensity. It then presents data for two representative weeks, one with extreme hot weather and one with typical hot weather in the centre of the London heat island and a rural reference site. These data are used to carry out a parametric analysis by using a thermal and air flow simulation tool specifically designed for offices in SE England. A reference and optimised office module are described. A comparison of the building types based in the same location suggests that during the typical hot week the rural reference office has 84% energy demand for cooling compared to a similar urban office. A rural optimised office would not need any artificial cooling and would be able to maintain temperatures below 24°C. An urban optimised office would not be able to achieve this. A rural optimised office would need 42% of the cooling required for an optimised urban office. A comparison of the optimised to the reference office module suggests that an urban optimised office reduces the cooling demand to 10% of the urban reference office.
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While the benefits of ensemble techniques over deterministic numerical weather predictions (NWP) are now widely recognized, the prospects of ensemble prediction systems (EPS) at high computational resolution are still largely unclear. Difficulties arise due to the poor knowledge of the mechanisms promoting rapid perturbation growth and propagation, as well as the role of nonlinearities. In this study, the dynamics associated with the growth and propagation of initial uncertainties is investigated by means of real-case high-resolution (cloud resolving) NWP integrations. The considered case is taken from the Mesoscale Alpine Programme intensive observing period 3 (MAP IOP3) and involves convection of intermediate intensity. To assess the underlying mechanisms and the degree of linearity upon the predictability of the flow, vastly different initial perturbation methodologies are compared, while all simulations use identical lateral boundary conditions to mimic a perfectly predictable synoptic-scale flow. Comparison of the perturbation methodologies indicates that the ensuing patterns of ensemble spread converge within 11 h, irrespective of the initial perturbations employed. All methodologies pinpoint the same meso-beta-scale regions of the flow as suffering from predictability limitations. This result reveals the important role of nonlinearities. Analysis also shows that hot spots of error growth can quickly (1–2 h after initialization) develop far away from the initial perturbations. This rapid radiation of the initial uncertainties throughout the computational domain is due to both sound and gravity waves, followed by the triggering and/or growth of perturbations over regions of convective instability. The growth of the uncertainties is then limited by saturation effects, which in turn are controlled by the larger-scale atmospheric environment. From a practical point of view, it is suggested that the combined effects of rapid propagation, sizeable amplification, and inherent nonlinearities may pose severe difficulties for the design of EPS or data assimilation techniques related to high-resolution quantitative precipitation forecasting.
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Ecoclimap, a new complete surface parameter global dataset at a 1-km resolution, is presented. It is intended to be used to initialize the soil-vegetation-atmosphere transfer schemes (SVATs) in meteorological and climate models (at all horizontal scales). The database supports the `tile' approach, which is utilized by an increasing number of SVATs. Two hundred and fifteen ecosystems representing areas of homogeneous vegetation are derived by combining existing land cover maps and climate maps, in addition to using Advanced Very High Resolution Radiometer (AVHRR) satellite data. Then, all surface parameters are derived for each of these ecosystems using lookup tables with the annual cycle of the leaf area index (LAI) being constrained by the AVHRR information. The resulting LAI is validated against a large amount of in situ ground observations, and it is also compared to LAI derived from the International Satellite Land Surface Climatology Project (ISLSCP-2) database and the Polarization and Directionality of the Earth's Reflectance (POLDER) satellite. The comparison shows that this new LAI both reproduces values coherent at large scales with other datasets, and includes the high spatial variations owing to the input land cover data at a 1-km resolution. In terms of climate modeling studies, the use of this new database is shown to improve the surface climatology of the ARPEGE climate model.
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Soil/vegetation–atmosphere transfer schemes (SVATS) require only a few primary parameters as inputs (leaf area index, vegetation fraction and albedo). The object of this paper is to describe methods used to derive these parameters from surface cover maps, climate maps and NDVI datasets. The resolution of these new surface parameters is 1 km at the global scale. The ECOCLIMAP database is available online to the research community at http://www.cnrm.meteo.fr/gmme/PROJETS/ECOCLIMAP/page_ecoclimap.htm. An application of this strategy for urban use at a finer scale (30mresolution) is presented here for the city of Marseille. Copyright © 2005 Royal Meteorological Society.
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The paper describes the turbulence scheme implemented in the Meso-NH community research model, and reports on some validation studies. Since the model is intended to perform both large-eddy and mesoscale simulations, we have developed a full three-dimensional scheme, based on the original method of Redelsperger and Sommeria. A prognostic equation for the turbulent kinetic energy is used, together with conservative variables for moist non-precipitating processes. A particularity of the scheme is the use of variable turbulent Prandtl and Schmidt numbers, consistently derived from the complete set of second-order turbulent-moment equations. The results of three idealized boundary-layer simulations allowing detailed comparisons with other large-eddy simulation (LES) models are discussed, and lead to the conclusion that the model is performing satisfactorily.The vertical flux and gradient computation can be run in isolation from the rest of the scheme, providing an efficient single-column parametrization for the mesoscale configuration of the model, if an appropriate parametrization of the eddy length-scale is used. The mixing-length specification is then the only aspect of the scheme which differs from the LES to the mesoscale configuration, and the numerical constants used for the closure terms are the same in both configurations. The scheme is run in single-column mode for the same three cases as above, and a comparison of single-column and LES results again leads to satisfactory results. It is believed that this result is original, and is due to the proper formulation of the parametrized mixing length and of the turbulent Prandtl and Schmidt numbers. In fact, a comparison of the parametrized mixing length with the length-scale of the energy-containing eddies deduced by spectral analysis of the LES shows interesting similarity.