Microclimate Mitigation Research Articles

On urban microclimate spatial-temporal dynamics: Evidence from the integration of fixed and wearable sensing and mapping techniques

Urban Heat Island (UHI) is acknowledged to generate harmful consequences on human health, and it is one of the main anthropogenic challenges to face in modern cities. Due to the urban dynamic complexity, a full microclimate decoding is required to design tailored mitigation strategies for reducing heat-related vulnerability. This study proposes a new method to assess intra-urban microclimate variability by combining for the first time two dedicated monitoring systems consisting of fixed and mobile techniques. Data from three fixed weather stations were used to analyze long-term trends, while mobile devices (a vehicle and a wearable) were used in short-term monitoring campaigns conducted in summer and winter to assess and geo-locate microclimate spatial variations. Additionally, data from mobile devices were used as input for Kriging interpolation in the urban area of Florence (Italy) as case study. Mobile monitoring sessions provided high-resolution spatial data, enabling the detection of hyperlocal variations in air temperature. The maximum air temperature amplitudes were verified with the wearable system: 3.3 °C in summer midday and 4.3 °C in winter morning. Physiological Equivalent Temperature (PET) demonstrated to be similar when comparing green areas and their adjacent built-up zone, showing up the microclimate mitigation contribution of greenery in its surrounding. Results also showed that mixing the two data acquisition and varied analysis techniques succeeded in investigating the UHI and the site-specific role of potential mitigation actions. Moreover, mobile dataset was reliable for elaborating maps by interpolating the monitored parameters. Interpolation results demonstrated the possibility of optimizing mobile monitoring campaigns by focusing on targeted streets and times of day since interpolation errors increased by 10% only with properly reduced and simplified input samples. This allowed an enhanced detection of the site-specific granularity, which is important for urban planning and policymaking, adaptation, and risk mitigation actions to overcome the UHI and anthropogenic climate change effects.

Evaluation of microclimate mitigation strategies in a heterogenous street canyon in Kuala Lumpur from outdoor thermal comfort perspective using Envi-met

Assessing the efficacy of mitigation measures for the improvement of the daytime microclimate has been advised extensively, especially in hot and humid tropical regions as an effort to a) reduce the cooling demand of buildings and b) enhance outdoor livability by improving the thermal comfort of pedestrians. The latter has been investigated in this research based on microclimatic and urban characteristics of a developed commercial street in Kuala Lumpur, Malaysia and by utilization of field measurements and parametric simulations. The evaluated area is within a street canyon with heterogeneity in its urban components and building design with various heights and façade materials; being distinguished from the uniform or open-set urban complexes which had been assessed in the previous studies.Five mitigating scenarios were adopted using Envi-met V4.6 simulation software to investigate their influence on air temperature (Ta), surface temperature (Ts), mean radiant temperature (Tmrt), and physiological equivalent temperature (PET) in the study area during peak hours of the day from 11:00 to 16:00. Among the high albedo façade, high reflective ground surfaces, permeable pavement, extra tree coverage, and a mixture of the last two measures, it is identified that the application of permeable pavements and added tree resulted in maximum PET improvement along with Ta, Tmrt, and Ts reductions. The study also shows that increasing the albedo of facades despite a negligible impact in reducing Ta, causes PET to worsen; the same results were obtained regarding high reflective pavements and roads, although significant Ts reduction occurred through this method. The research concludes that considering the tropical climate of Kuala Lumpur with abundant solar radiation and rainfall, for narrow streets with variation in components and high-rise buildings, implementation of permeable pavement on sidewalks and open parking areas not only contribute to alleviating urban warming effects but can potentially manage stormwater runoff as well.

Study on an air conditioning system with the use of natural cooling

Issues of microclimate mitigation in Uzbekistan during the summer period require urgent resolution. It should be noted that currently there are very few researches, as well as practical recommendations related to the formation of a favorable microclimatic environment in cities with a hot climate. The simplest and most economical way of cooling, in dry and hot climates, is the evaporative cooling of a dry air stream. One of the possible ways to increase the efficiency of the system is the use of night evaporative cooling of water, followed by its accumulation for daytime cooling in heat-insulated batteries. The conducted experiments testify that rather simple and cheap natural sources of cold can be used along with machine cold sources for air conditioning of residential buildings in Uzbekistan.

Cooling air in contact with natural sources of cold

Issues of microclimate mitigation in Uzbekistan during the summer period require urgent resolution. It should be noted that currently there are very few research, as well as practical recommendations related to the formation of a favorable microclimatic environment in cities with a hot climate. The simplest and most economical way of cooling, in dry and hot climates, is the evaporative cooling of a dry air stream. One of the possible ways to increase the efficiency of the system is the use of night evaporative cooling of water, followed by its accumulation for daytime cooling in heat-insulated batteries. The conducted experiments testify that rather simple and cheap natural sources of cold can be used along with machine cold sources for air conditioning of residential buildings in Uzbekistan.

About possibility of using natural sources of cold in air conditioning system

Issues of microclimate mitigation in Uzbekistan during the summer period require urgent resolution. It should be noted that currently, there is very little research and practical recommendations related to the formation of a favorable microclimatic environment in cities with a hot climate. The simplest and most economical way of cooling in dry and hot climates is the evaporative cooling of a dry air stream. One of the possible ways to increase the system's efficiency is the use of night evaporative cooling of water, followed by its accumulation for daytime cooling in heat-insulated batteries. The conducted experiments testify that rather simple and cheap natural sources of cold can be used along with cold machine sources for air conditioning residential buildings in Uzbekistan.

Pocket parks for human-centered urban climate change resilience: Microclimate field tests and multi-domain comfort analysis through portable sensing techniques and citizens’ science

Dense urban areas are subject to dynamic and urgent challenges, exacerbated by anthropogenic forcing. Urban Heat Island and heatwaves pose a threat to citizens’ comfort, due to extreme microclimate conditions. In this panorama, urban parks represent effective strategies towards more livable and comfortable urban areas. In particular, small pocket parks could aid in the mitigation of such challenges in every neighborhood. Indeed, they are in close proximity to citizens, allowing large population groups to benefit from the advantage of living green areas. Therefore, this paper assesses for the first time microclimate conditions and personal multi-domain perception imputable to pocket parks, by means of human-centered experimental analyses, coupling objective and subjective assessment. Wearable monitoring-systems are employed for the assessment of granular-microclimate variables mapping, and questionnaire-surveys are collected in the pocket parks and their surroundings, for comparison purposes. Results show that, while microclimate mitigation is not extremely significant as expected (−0.5 °C air temperature, +5–10% relative humidity inside the park), perceived comfort in pocket parks is higher than on the streets, shifting from “neutral” on the close by streets to “good/very good” in the park. Therefore, a better design for microclimate mitigation of pocket parks is needed, especially taking into account the potential air stagnation, while acknowledging their fundamental societal role.

Blue-Green infrastructure determines the microclimate mitigation potential targeted for urban cooling

Urban Heat Island (UHI) exacerbated by global warming can increase the thermal load in cities, which leads to more extreme climate events. One of the strategies to mitigate the impact of extreme climates and UHI is through nature-based solutions such as the Blue-Green Infrastructure as it provides environmental and community benefits However, Blue-Green Infrastructure’s role in urban cooling in the tropics still needs to be further investigated. Therefore, this study examined the role of Blue-Green Infrastructure on microclimate modifications in an urban park. Microclimate measurements were made using systematic random sampling with random start (total of 64 sampling points) at a waterbody (Blue Infrastructure) and tree and grass (Green Infrastructure) areas during solar noon time (1200-1400). Blue-Green Infrastructure showed greater microclimate benefits compared to the open space with the reduction of air temperature by up 1.6°C. However, green infrastructure had greater cooling benefits compared to Blue Infrastructure especially trees with significantly lower air temperature and solar radiation interception (0.71°C and 250.3 W/m2, respectively) as well as higher relative humidity (12.17%). Moreover, stand characteristics determine the microclimate mitigation function. This study provides a useful indication of the role of blue and green spaces in urban cooling, where it further emphasizes the importance of Blue-Green Infrastructure utilization in urban landscapes. It further recommends that urban planners, managers and policymakers should consider these strategies for urban cooling purposes : 1) Utilising Blue and Green Infrastructures especially trees 2) Tree canopy cover and DBH should be set as priority traits.

Nature-Based Solutions: Thermal Comfort Improvement and Psychological Wellbeing, a Case Study in Genoa, Italy

The urban heat island (UHI) effect is among the most critical issues caused by human activities and high building density. UHI has severe impacts on the urban and natural environment as well as on human health and wellbeing. The research presented here aims at evaluating the effects of nature-based solutions (NBS) in improving the livability of a district in the city of Genoa, which is heavily cemented and a major example of the heat island phenomenon. This study focuses on the microclimatic benefits of urban heat island mitigation as well as on psychological and perceptual aspects. A preliminary analysis of the district through CFD simulations using Envi-met software allowed for selection of the most suitable areas for a system of punctual interventions in urban regeneration using nature-based solutions. For each area identified, we simulated the effects of different design scenarios on microclimate mitigation and thermal comfort improvement. In addition, to evaluate the perceptual benefits of the most well-performing design scenarios, we set up a web-based survey that was administered to a convenience sample of Genoa residents. In terms of aesthetic satisfaction and perception of improved conditions of physical and psychological well-being, the preferred design outcomes were those which emphasized a freer and more natural environment. This study shows that nature-based solutions can improve the overall conditions of dense urban areas; microclimate performance and psychological effects should be both considered in the design process in order to improve the wellbeing of urban citizens.

Analysis of Olive Grove Destruction by Xylella fastidiosa Bacterium on the Land Surface Temperature in Salento Detected Using Satellite Images

Agricultural activity replaces natural vegetation with cultivated land and it is a major cause of local and global climate change. Highly specialized agricultural production leads to extensive monoculture farming with a low biodiversity that may cause low landscape resilience. This is the case on the Salento peninsula, in the Apulia Region of Italy, where the Xylella fastidiosa bacterium has caused the mass destruction of olive trees, many of them in monumental groves. The historical land cover that characterized the landscape is currently in a transition phase and can strongly affect climate conditions. This study aims to analyze how the destruction of olive groves by X. fastidiosa affects local climate change. Land surface temperature (LST) data detected by Landsat 8 and MODIS satellites are used as a proxies for microclimate mitigation ecosystem services linked to the evolution of the land cover. Moreover, recurrence quantification analysis was applied to the study of LST evolution. The results showed that olive groves are the least capable forest type for mitigating LST, but they are more capable than farmland, above all in the summer when the air temperature is the highest. The differences in the average LST from 2014 to 2020 between olive groves and farmland ranges from 2.8 °C to 0.8 °C. Furthermore, the recurrence analysis showed that X. fastidiosa was rapidly changing the LST of the olive groves into values to those of farmland, with a difference in LST reduced to less than a third from the time when the bacterium was identified in Apulia six years ago. The change generated by X. fastidiosa started in 2009 and showed more or less constant behavior after 2010 without substantial variation; therefore, this can serve as the index of a static situation, which can indicate non-recovery or non-transformation of the dying olive groves. Failure to restore the initial environmental conditions can be connected with the slow progress of the uprooting and replacing infected plants, probably due to attempts to save the historic aspect of the landscape by looking for solutions that avoid uprooting the diseased plants. This suggests that social-ecological systems have to be more responsive to phytosanitary epidemics and adapt to ecological processes, which cannot always be easily controlled, to produce more resilient landscapes and avoid unwanted transformations.

A Study on Microclimate characteristics and energy balance within near-river riparian systems

Riparian microclimate studies are gaining increasing attention due to their close ecological, climatologic and aesthetic interactions with lives in both natural and urban areas. Historically, many researchers studied thermal regimes of rivers and river temperature responses to different management strategies. Near-river microclimate characteristics and relevant energy balance were not fully understood. This review documents recent research on near-river microclimatic features and energy exchanging processes, roles of macroclimate, rivers, riparian vegetation and topography play in microclimate mitigation, their ecological importance in terms of biodiversity support and human thermal comfort promotion. It also emphasizes potentials of studies on integration of rivers and plants, as well as their controls on heat exchanging. This study is hopefully useful for river scholars to strengthen the comprehension for further research, as well as for river designers and managers to make informed decisions of sustainable urban development.

Ecosystem Services of Vegetation Features as the Multifunction Anti-Erosion Measures in the Czech Republic in 2019 and Its 30-Year Prediction

The communication presents the pieces of information of the ecosystem services estimation of the four research localities transformed from an arable land to vegetation features—bosks. These bosks should dispose several ecological functions, primarily anti-erosion measures, additionally the local biodiversity increase, unfavorable microclimate mitigation, shelter provision for small game, birds and insects, or wood and fruit production, etc. One of these benefits, the biodiversity increase, can be evaluated using the Habitat Valuation Method (HVM) and expressed by the financial value obtained on the basis of a combination of expert valuation and cost replacement method. The various combinations of local woody plants and bushes within the project Multifunction anti-erosion measures as a part of adaptable landscape were planted or sown at the project localities (South Moravia and Žďárské vrchy, Czech Republic) in March 2019. Ecosystem services evaluation was one of the fundamental outcomes of the project. The most important result was the calculated value increase of the service termed “environment for the species life providing and genetic diversity conserving”. The increase means the difference between the state prior to planting and the expected target state after 30 years as specified in HVM. In total, the increase of this ecosystem service of the four bosks was valued at 2,633,809.64 CZK (97,206.48 EUR/114,399.06 USD).

Trends and gaps in global research of greenery systems through a bibliometric analysis

This study presents a critical review analysis of greenery systems research through a bibliometric approach. The purpose of this study is to provide a holistic overview by (i) the development of the field; (ii) the research trends and the main issues; and (iii) the main gaps still observed in the literature. Therefore, this paper provides the past, the present and the potential future of this scientific topic and serves as an orientation and guide for researchers who aim for a better understanding of the main progress and gaps. A detailed analysis of 1918 documents found in the Scopus database for the 1974–2019 period was conducted. Content analysis of titles, keywords and abstracts revealed that most of the research has focused on the study of green roofs. Previously this topic was dominated by water runoff analysis, while recent contributions acknowledge greenery as an effective microclimate mitigation strategy, especially in urban areas. The United States was the most productive country, representing almost 20 % of the total documents. Over 86 % of the relevant documents were published since 2009. Overall, research on this topic is increasing, with new methods and directions but some gaps remain particularly on the areas of environmental impact, costs, health, outdoor thermal comfort, and vertical greenery systems.

Combined Effect of Outdoor Microclimate Boundary Conditions on Air Conditioning System’s Efficiency and Building Energy Demand in Net Zero Energy Settlements

In Europe, near zero energy buildings (NZEBs) represent the new frontier of energy efficiency in the built environment. Shifting the scale from NZEBs to net zero energy (NZE) settlements represents the opportunity to achieve further energy, environmental, and cost benefits, thanks to shared energy management, optimization of renewable energy systems, and microclimate mitigation. In particular, the last aspect takes advantage of the implementation of local microclimate mitigation strategies at a larger scale to improve settlements outdoor environmental conditions and citizens’ wellbeing. Furthermore, this inter-building scale mitigation involves relatively less severe working boundary conditions for buildings, able to both reduce building energy demand and improve HVAC (heating, ventilation, and air conditioning) system’s efficiency. In this study, this potential extra-energy saving, achievable without additional costs, is explored within the framework of a NZE settlement built in Italy thanks to an ongoing Horizon 2020 project. Improved working conditions for the operating air conditioning system and building energy savings thanks to settlement scale opportunities for microclimate mitigation are assessed. Findings show how this effect represents a further non-negligible energy-efficient and environmentally sustainable benefit achievable through the design and construction of NZE settlements. Potential energy savings are up to 24% when considering the double effect of microclimate mitigation.

Spatiotemporal dynamics of urban ecosystem services in Turkey: The case of Bornova, Izmir

Bornova metropolitan district is one of the most urbanised districts in Izmir metropolitan city, Turkey; with unknown eff ;ects on the potential ecosystem services along urban-rural areas. This study mapped the condition of ecosystem services’ potential and analysed their spatiotemporal dynamics and patterns between 1990 and 2018 for Bornova district. The methodology used in this study was based on an existing potential ecosystem services mapping methodology and spatially explicit index using open access available spatial data. The spatiotemporal changes in the potential ecosystem services along the urban-rural gradient of Bornova district were assessed by global climate regulation (carbon storage), microclimate mitigation (Land Surface Temperature) and ecological integrity. The total vegetation cover in Bornova district increased from 18.41 % to 27.95 % to the last 28 years, particularly in peri-urban areas. Accordingly, two of the selected ecosystem services’ potential has increased throughout the district, except for ecological integrity. These changes were closely related to the deliberate efforts of the Bornova Municipal Council in increasing the amount of urban green and open spaces throughout the Bornova district in coordination with Izmir Metropolitan City Council’s commitment to build a healthy and climate friendly city in the near future.

Microclimate mitigation for enhancing energy and environmental performance of Near Zero Energy Settlements in Italy

This work aims at shifting the focus from single-building to the inter-building scale in construction settlements design by proposing a multi-scale approach, coupling outdoor microclimate mitigation and building energy prediction and saving. The developed procedure links (i) the assessment of outdoor microclimate and mitigation techniques for counteracting Urban Heat Island, (ii) Near Zero Energy (NZE) Building energy efficiency design and (iii) the minimization of their environmental impact in terms of CO2eq. In this view, a multi-objective analysis is carried out by investigating the most proper inter-building size to be focused on for sustainable cities, able to optimize these three targets. Both the energy and environmental aspects are considered at different urban scales, starting with a single-building analysis and progressively extending the field of action. The presented methodology is applied to a real new residential NZE Settlement in Italy. Findings show that microclimate mitigation strategies, e.g. increased vegetated areas and highly-reflective envelope materials and permeable pavements, can lead to annual energy saving up to 12 % and reduction of summer operational CO2 emissions by 4 % at building level. Such benefits reach about 22 % energy savings and 5 % operational CO2 reduction when extending the size of the mitigated area to the whole settlement.

Inter-building assessment of urban heat island mitigation strategies: Field tests and numerical modelling in a simplified-geometry experimental set-up

Large scale mitigation strategies showed to represent promising solutions for enhancing liveability in dense urban contexts. Therefore, most of the researches are focused on assessing the effect of high albedo surfaces and greenery. The paper deals with a numerical and experimental analysis of these evapotranspiration and high-reflectance surfaces in a full scale experimental set-up where more than 20 cubicles are monitored in a Mediterranean continental climate. The experimental set-up itself covers an intermediate inter-building perspective between the lab scale and the real urban contexts, which compromises the possibility to generalize final results. This scale is able to better control geometry of area, but allows real microclimate monitoring and calibration of CFD models. Starting from a validated model, this study simulated alternative scenarios with gradually varying the presence of common mitigation strategies with the scope to evaluate their effect to this aim. Results showed that high albedo solutions best mitigate summer overheating reducing the air temperature, while greenery was more effective in the densest configurations with low albedo envelopes, showing how geometry related variables may play a key role in determining the optima configurations of microclimate mitigation strategies, also important for the best exploitation of renewables in the built environment.

Influence of microclimate boundary conditions in net zero energy settlements on HVAC efficiency

Net zero energy buildings (NZEB) represent reality of new constructions in Europe for environmentally sustainable energy efficiency. The shift to net zero energy settlements represents a further opportunity to achieve extra-energy saving, thanks to utilities sharing, renewables optimization, and microclimate mitigation. This last aspect concerns the opportunity to improve settlements outdoor microclimate conditions in both hot and cold seasons, in a variety of climate conditions, with the purpose to improve occupants’ wellbeing. At the same time, microclimate mitigation at inter-building scale may also involve relatively less severe boundary conditions able to reduce both cooling and heating demand of buildings and better working conditions for HVAC systems, e.g. heat pumps and air-to-air heat exchangers. This extra-energy saving, achievable with no extra costs, may represent an interesting opportunity to be taken into account in net zero energy settlements design and construction. This study analyzes this energy saving in a net zero energy settlement in Italy, built thanks to an on-going Horizon 2020 project. The influence of microclimate mitigation strategies is assessed in terms of energy saving benefits for the heat pump working conditions. Results demonstrate that this further benefit represents a non-negligible, environmentally sustainable, strategy for energy efficiency of NZEB in new inter-building scale developments.

Mitigation of rising urban temperatures starting from historic and modern street canyons towards zero energy settlement

The necessity of restraining global warming to 1.5°C (IPCC Special Report 2018) implies many actions at global and local level in order to reduce CO2 emissions to net zero by 2050. Moreover, in urban area, the intensity of more and more frequent heatwaves is magnified by Urban Heat Island (UHI) effects and it increases the production of CO2 due to the intensification in cooling demand. Over the years, the historic settlement (medieval town) has showed to be more resilient to temperature changes than modern district. This paper compares the historic district with the modern one in Bari (southern Italy) in terms of morphology, type and construction technology through Envi-met simulations. It highlights how the fabric of the old town may have positive impact on summer regime for thermal comfort and its analysis can be useful for the definition of some guidelines for contemporary settlement. Natural solutions (e.g. vegetation, green roofs and water jects) and cool materials are proposed to reduce energy demand according to EU directive 2018/844 and complying with the constraints for consolidated urban area. The aim is also to evaluate the solutions for microclimate mitigation of urban canyons towards zero energy settlement starting from the old town features.

The Role of Green Roofs on Microclimate Mitigation Effect to Local Climates in Summer

Although there is a large body of previous studies on the cooling effect of green roofs on urban heat islands (UHIs), more empirical studies with an experimental setting measuring the role of green roof on mitigating urban heat should be considered. The purpose of this research is to determine the air temperature difference between green and bare roofs located on two buildings in the same local climate zone, and calculate the expected cooling effect extended from the green roof to the local climate. The study site consisted of an extensive green roof and a bare roof which were close to each other and were located in a highly built-up same area. During the three and a half clean days of testing in the middle of summer, air temperature data were collected from each roof using an air temperature logger and a local automatic weather station close to both roofs; these data were then converted to hourly data. The data were analyzed by the t test, ANOVA test, and a regression analysis to determine the heat mitigation effect of green roofs. As a result, the green roof’s air temperature showed much lower than the bare roof’s and followed the local station’s air temperature change during the day. At night the air temperature difference between the two roofs was only slight and the green roof’s air temperature kept lower than the local station’s. Thus, even extensive green roofs can reduce air temperature through their cooling effects from their vegetation and substrates against solar radiation. The established models reported that the green roof contributed to lowering air temperatures in a local climate zone, while the bare roof made such zones more heated. The findings of this study contribute to the existing literature by proving that green roofs can be expected to help cool down not only at the small scale with building units, but also at the broader scale of urban district area. The study also gives field-experimented values to be used as updated variables to local climate simulation models.

How outdoor microclimate mitigation affects building thermal-energy performance: A new design-stage method for energy saving in residential near-zero energy settlements in Italy

Abstract Key research effort was dedicated toward zero-energy buildings. Recent interest is switching from single-building to inter-building scale, to enhance the whole district economic-environmental sustainability. This upscaling opens the doors to further optimization strategies thanks to outdoor microclimate mitigation aimed at reducing winter thermal losses and summer overheating. This work proposes a novel design-stage replicable method for multiscale microclimate improvement correlated to building thermal-energy analysis in a residential near-zero-energy district in central Italy. Cool surface installation and conscious greenery design in the outdoors were used in the district of single-family houses. Therefore, a microclimate simulation was performed to elaborate realistic weather files to be used in the second-stage dynamic thermal-energy simulation at building level, in order to evaluate the impact of the local microclimate on building thermal-energy performance and renewables’ production. Microclimate analysis demonstrated how local conditions affect outdoor comfort and that they may be considered in the same way as traditional energy-efficiency improvement early-stage design strategies at building scale, being able to reduce building energy need for HVAC up to 10% in the studied conditions. Therefore, new potentialities of inter-building scale analyses for energy efficiency enhancement and renewable energy exploitation are expected while downscaling microclimate assessment toward building thermal-energy performance.