More frequent and longer duration heat waves have been observed worldwide and are recognized as a serious threat to human health and the stability of electrical grids. Past studies have identified a ...positive feedback between heat waves and urban heat island effects. Anthropogenic heat emissions from buildings have a crucial impact on the urban environment, and hence it is critical to understand the interactive effects of urban microclimate and building heat emissions in terms of the urban energy balance. Here we developed a coupled-simulation approach to quantify these effects, mapping urban environmental data generated by the mesoscale Weather Research and Forecasting (WRF) coupled to Urban Canopy Model (UCM) to urban building energy models (UBEM). We conducted a case study in the city of Los Angeles, California, during a five-day heat wave event in September 2009. We analyzed the surge in city-scale building heat emission and energy use during the extreme heat event. We first simulated the urban microclimate at a high resolution (500 m by 500 m) using WRF-UCM. We then generated grid-level building heat emission profiles and aggregated them using prototype building energy models informed by spatially disaggregated urban land use and urban building density data. The spatial patterns of anthropogenic heat discharge from the building sector were analyzed, and the quantitative relationship with weather conditions and urban land-use dynamics were assessed at the grid level. The simulation results indicate that the dispersion of anthropogenic heat from urban buildings to the urban environment increases by up to 20% on average and varies significantly, both in time and space, during the heat wave event. The heat dispersion from the air-conditioning heat rejection contributes most (86.5%) of the total waste heat from the buildings to the urban environment. We also found that the waste heat discharge in inland, dense urban districts is more sensitive to extreme events than it is in coastal or suburban areas. The generated anthropogenic heat profiles can be used in urban microclimate models to provide a more accurate estimation of urban air temperature rises during heat waves.
Aim: Climatic conditions exert a strong control on the geographic distribution of many woodland-to-grassland transition zones (or 'tree lines'). Because woody plants have, in general, a weaker cold ...tolerance than herbaceous vegetation, their altitudinal or latitudinal limits are strongly controlled by cold sensitivity. While temperature controls on the dynamics of woodland–grassland ecotones are relatively well established, the ability of woody plants to modify their microclimate and to create habitat for seedling establishment and growth may involve a variety of processes that are still not completely understood. Here we investigate feedbacks between vegetation and microclimatic conditions in the proximity to woodland–grassland ecotones. Location: We concentrate on arctic and alpine tree lines, the transition between mangrove forests and salt marshes in coastal ecosystems, and the shift from shrubland to grassland along temperature gradients in arid landscapes. Methods: We review the major abiotic and biotic mechanisms underlying the ability of woody plants to alter the nocturnal microclimate by increasing the temperatures they are exposed to. Results: We find that in many arctic, alpine, desert and coastal landscapes the presence of trees or shrubs causes nocturnal warming thereby favouring the establishment and survival of woody plants. Main conclusion: Because of this feedback, trees and shrubs may establish in areas that would be otherwise unsuitable for their survival. Thus, in grassland–woodland transition zones both vegetation covers may be (alternative) stable states of the landscape, thereby affecting the way tree lines may migrate in response to regional and global climate change.
Life quality in urban contexts is related to several interconnected factors. Lots of innovative technologies allow for the gathering of real-time information, which is helpful for analysing and ...interpreting significant urban dynamics and citizens’ behaviours. The presence of people in outdoor environments, particularly for social and recreational purposes, can be considered as a qualitative indicator, giving evidence of a living environment. The relationship between urban areas and the climate context has been addressed in recent years by the scientific literature. However, these studies did not report the direct correlation between people’s presence and outdoor thermal comfort in outdoor spaces. The aim of this paper is to assess whether the presence of people in outdoor public spaces, detected through human presence sensors, can be associated with outdoor microclimatic conditions (both with on-site measurement and software simulation) and outdoor thermal comfort indicators (as physiological equivalent temperature). The question is whether there exists a direct correlation between outdoor microclimate in public spaces and people’s presence, and if a public event plays a role in changing it. The research compares on-site measurements of physics variables (e.g., air temperature) and people’s presence with outdoor microclimate maps by Envi-met. The case study, carried out in the framework of the H2020 project ROCK—Regeneration and Optimization of Cultural Heritage in Creative and Knowledge cities, focuses on two squares located in Bologna’s historic city center. The conclusions show that public events are the main deciding factor influencing square crowding; nevertheless, the study reveals a relationship between thermal comfort and the number of people.
This paper provides an updated literature review about greenhouse systems and helps to identify the most preferable characteristics of a greenhouse for diverse climates and operating conditions. Data ...on appropriate properties of the covering materials and comparisons of several cladding materials were extensively discussed. The selection process of the greenhouse shape and orientation for different climates is presented, and comparisons between several shapes and orientations are made. This paper also examines the existing thermal models and simulation tools used to optimize the thermal operating conditions of the greenhouse. Furthermore, many recent studies are presented where greenhouses are combined with several systems to provide a favorable microclimate for crops, under extreme, tropical and subtropical climates. Finally, other applications such as greenhouse dryers and seawater greenhouse desalination are also discussed.
According to the challenge of global warming, trees play an effective role in reducing heat islands and improving thermal comfort. In this study, the impact of urban greening on microclimate and ...pedestrian comfort is studied using ENVI met v4 for a residential district in Tabriz, Iran. In-situ measurements of air temperature and relative humidity have been preliminary performed on ten points in the studied site and collected data used to successfully validate the model. Four scenarios with different trees species and patterns were simulated during typical summer and winter days, to assess benefits and disadvantages during different seasons, in terms of air temperature (Ta) and relative humidity (RH), mean radiant temperature (Tmrt) and physiologically equivalent temperature (PET). Result showed that the best scenario provides great summer cooling without compromising winter comfort. In summer Ta and Tmrt are decreased by respectively 0.29 °C and 20.04 °C; while in winter, they reach respectively 6.92 °C and 13.22 °C, compared the reference scenario characterised by 6.28 °C (Ta) and 23.47 °C (Tmrt). These results in a summer PET improvement from 34.92 °C to 26.16 °C, thus moving from an original hot thermal sensation to a slightly warm one. Based on the outcomes of the study, it is possible to provide useful design recommendation for urban adaptation plans.
•Four scenarios with different trees species and patterns were simulated during typical summer and winter days.•From a qualitative point of view, trends highlight a good agreement among observed and predicted data.•Urban greening design can reduce mean radiant temperatures by 20.04 °C.•The change of RH both in summer and winter is modest and can be considered irrelevant for environmental comfort.
The built environment modifies energy budget at its proximity and the main related effect is the so-called Urban Heat Island phenomenon consisting in higher air temperature detected in urban contexts ...with respect to rural surroundings. Many studies focus the attention on the existing correlations between cities morphology and Urban Heat Island intensity. Nevertheless, the urban environment is complex and heterogeneous mining that at a lower scale, distinctive microclimate conditions express intra-urban granularity. The intensity of such phenomenon is most commonly analysed by means of a network of weather stations or remote sensing. The current work proposes to analyse the intra-urban microclimate diversification by means of cluster analysis of environmental data gathered through mobile transects at pedestrian perspective. This methodology is applied to four different typologies of urban context, i.e. mainly open site, packed historical, packed low-rise buildings and packed high-rise buildings, where monitoring campaigns are carried out during both day-time and night-time. The obtained results demonstrate potentials of the method in identifying similar morphological structure on the base of row environmental data. The heterogeneity of the selected contexts demonstrates the replicability of the proposed method while suggests the selection of different number of final clusters as function of the monitored context as further development of the study.
•Urban microclimate monitoring through mobile transects.•Pedestrian perspective captured by means of wearable sensing techniques.•Environmental data mapping in variable intraurban contexts.•Urban pattern described from environmental data clustering (bottom-up process).•Wearable sensing as useful tool for microclimate change analysis.
Weather data is a key input to achieve reliable building energy simulation, and in current studies, EnergyPlus Weather (EPW) data, historically measured by a few suburban weather stations, is the ...most widely used. However, weather is shaped by urban morphology and other factors, so transforming weather files for the urban context using tools such as Urban Weather Generator becomes necessary. This study investigated the differences between multi-sourced weather datasets after transforming, and, in turn, the subsequent impact on urban building energy simulation. As a case study, one campus block was selected, with 41 urban blocks and their urban morphologies obtained. One microclimate station and 16 sensors were then installed to collect weather data to validate multi-sourced weather files for energy simulation models. The study results showed the root mean square error of temperature differences between suburban weather station, EPW and on-campus microclimate was 2.1 °C and 4.3 °C, respectively, before transforming and 1.2 °C and 4.1 °C, respectively, after transforming. Regarding building energy use, the mean absolute percentage difference (MAPD) of cooling-energy use intensity (EUI) between those calculated using the three datasets was 32.4% and 13.1%, respectively, before transforming and 25.8% and 4.1%, respectively, after transforming. Meanwhile, the MAPD of heating-EUI was 27.2% and 116.3%, respectively, before transforming and 12.7% and 93.6%, respectively, after transforming. This study results provide a reference for selecting weather data for urban building energy modelling to achieve a reliable energy decision-making process.
•Cooling is not only a function of vegetation and surface materials, but also dependent on the form and spatial arrangement of urban features.•At the microscale, urban form has a larger impact on ...daytime temperatures than landscaping.•In mid-afternoon, dense urban forms can create local cool islands.•Spatial differences in cooling are strongly related to solar radiation and local shading patterns.•The LCZ classification scheme is a useful concept for integrating local climate knowledge into urban planning and design practices.
This study investigates the impact of urban form and landscaping type on the mid-afternoon microclimate in semi-arid Phoenix, Arizona. The goal is to find effective urban form and design strategies to ameliorate temperatures during the summer months. We simulated near-ground air temperatures for typical residential neighborhoods in Phoenix using the three-dimensional microclimate model ENVI-met. The model was validated using weather observations from the North Desert Village (NDV) landscape experiment, located on the Arizona State University's Polytechnic campus. The NDV is an ideal site to determine the model's input parameters, since it is a controlled environment recreating three prevailing residential landscape types in the Phoenix metropolitan area (mesic, oasis, and xeric). After validation, we designed five neighborhoods with different urban forms that represent a realistic cross-section of typical residential neighborhoods in Phoenix. The scenarios follow the Local Climate Zone (LCZ) classification scheme after Stewart and Oke. We then combined the neighborhoods with three landscape designs and, using ENVI-met, simulated microclimate conditions for these neighborhoods for a typical summer day. Results were analyzed in terms of mid-afternoon air temperature distribution and variation, ventilation, surface temperatures, and shading. Findings show that advection is important for the distribution of within-design temperatures and that spatial differences in cooling are strongly related to solar radiation and local shading patterns. In mid-afternoon, dense urban forms can create local cool islands. Our approach suggests that the LCZ concept is useful for planning and design purposes.
Cova de sa Guitarreta is located in the southern part of Mallorca Island (western Mediterranean). It was formed presumably by hypogenic processes in Upper Miocene reefal calcarenites. The cave hosts ...an important breeding colony of bats during the end of spring and early summer. Its microclimate is influenced by the presence of a thermal phreatic water table (27.7ºC) as well as by bat populations remaining in the cave along the reproductive season. The morphological bat-related features include bat claws and thumb marks scratches, together with several morphologies linked to bat excreta and aggressive leachates from guano. From the mineralogical point of view, this cave outstands regarding the presence of cave minerals linked to guano: nine phosphates have been identified, comprising three of them that are reported for the first time in Mallorcan caves (newberyite, struvite and whitlockite). Particularly interesting is the dichotomy between struvite and newberyite: the first one occurs when the cave is occupied by bat colonies (spring-summer), whereas in the colder seasons would occur the transformation of metastable struvite into a more stable newberyite. Caves with seasonal cyclical occupation of bat colonies could provide a new arena for the study of the guano-related mineral assemblages.
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