Research

19 pages, 7929 KiB

Open AccessEditor’s ChoiceArticle

Impacts of Urban Development between 2002 and 2022 on the Effects of Sea Breezes in Sendai, Japan—Analyzing Heat Balance Mechanism in Urban Space

by Yonghang Xie, Yasuyuki Ishida, Hironori Watanabe and Akashi Mochida

Atmosphere 2023, 14(4), 677; https://doi.org/10.3390/atmos14040677 - 03 Apr 2023

Cited by 3 | Viewed by 1578

Abstract

Sea breezes are important in a coastal urban climate; however, the impact of urban development on the effects of sea breezes, which decrease air temperature and increase humidity, has not been understood quantitatively. To quantitatively evaluate this impact in Sendai, Japan over the [...] Read more.

Sea breezes are important in a coastal urban climate; however, the impact of urban development on the effects of sea breezes, which decrease air temperature and increase humidity, has not been understood quantitatively. To quantitatively evaluate this impact in Sendai, Japan over the past twenty years, this study analyzed the heat balance mechanisms in urban spaces based on the simulation results of the Weather Research and Forecasting (WRF) model coupled with Local Climate Zone (LCZ) maps. Compared to the observation data on air temperature, specific humidity, and wind in August 2002, results of the numerical simulation, using the 2002 LCZ map and the meteorological conditions of August 2002, confirmed that the WRF model could reproduce meteorological factors well. Thereafter, two numerical simulations using the LCZ maps from 2002 and 2022 were conducted based on the same meteorological condition, from 25 July to 1 September 2008, to extract the impact of urban development on the effects of sea breeze. Consequently, when land use changed from urban built-up land to natural land cover, both the effects of sea breeze—decreasing air temperature and increasing humidity—decreased. Additionally, increases in LCZ 3 (compact low rise), mainly from LCZ 6 (open low rise) and LCZ 9 (sparsely built), decreased the effects of sea breeze (decreasing air temperature and increasing humidity) by 5% and 10%, respectively, in areas around Sendai Station. This was because the consumption of the sea breeze’s potential to decrease air temperature and increase humidity increased and the wind speed of sea breezes decreased in the windward areas of Sendai Station. These results provide new insights into the impact of urban development on the effects of sea breeze and quantitatively reveal changes in the effects of sea breeze. Full article

(This article belongs to the Special Issue Strategies for Mitigation and Adaptation to Urban Heat)

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20 pages, 8927 KiB

Open AccessEditor’s ChoiceArticle

Urban Heat Mitigation towards Climate Change Adaptation: An Eco-Sustainable Design Strategy to Improve Environmental Performance under Rapid Urbanization

by Mehdi Makvandi, Wenjing Li, Xiongquan Ou, Hua Chai, Zeinab Khodabakhshi, Jiayan Fu, Philip F. Yuan and Elyse de la Joie Horimbere

Atmosphere 2023, 14(4), 638; https://doi.org/10.3390/atmos14040638 - 28 Mar 2023

Cited by 7 | Viewed by 2273

Abstract

Rapid urbanization has led to drastic land-use/cover changes (LUCCs) and urban heat islands (UHIs), negatively altering the urban climate and air quality. LUCC’s significant impacts on human health and energy consumption have inspired researchers to develop nature-based solutions to mitigate UHIs and improve [...] Read more.

Rapid urbanization has led to drastic land-use/cover changes (LUCCs) and urban heat islands (UHIs), negatively altering the urban climate and air quality. LUCC’s significant impacts on human health and energy consumption have inspired researchers to develop nature-based solutions to mitigate UHIs and improve air quality. However, integrating GIS-CFD modeling for urban heat mitigation towards climate change adaptation was largely neglected for eco-sustainable urban design in rapidly urbanizing areas. In this study, (1) long-term LUCC and meteorological analysis were conducted in the Wuhan metropolitan area from 1980 to 2016; (2) to mitigate the adverse effects of LUCC under a speedy development process, the role and relevance of optimizing building morphology and urban block configuration were discussed; (3) and particular design attention in strategy towards climate change adaptation for environmental performance improvement was paid in Wuhan’s fast-growing zones. The results show that UHII in 1980 was less severe than in 2016. Air temperature (Ta) increased by 0.4 °C on average per decade in developing areas. This increases the severity of UHII in urban fringes. It is found obligatory for a nature-based design to adopt urban morphology indicators (UMIs) such as average building height (μBH), sky view factors (ψ_SVF), and building density (BD/λ_p = % of built area) towards these changes. Further, on-site measurement revealed that λ_p is the most effective indicator for increasing urban heat around the buildings and boosting UHII. Using UMIs and a combined three-in-one regulation strategy based on μBH of common building types of high-rise (BH^A), mid-rise (BH^B), and low-rise (BH^C) buildings can effectively contribute to regulating Ta and air movement within block configuration. As a result of this study’s strategy, urban heat is mitigated via reinforcing wind in order to adapt to climate change, which impacts the quality of life directly in developing areas. Full article

(This article belongs to the Special Issue Strategies for Mitigation and Adaptation to Urban Heat)

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19 pages, 2649 KiB

Open AccessEditor’s ChoiceArticle

Tree Traits and Microclimatic Conditions Determine Cooling Benefits of Urban Trees

by Mahmuda Sharmin, Mark G. Tjoelker, Sebastian Pfautsch, Manuel Esperón-Rodriguez, Paul D. Rymer and Sally A. Power

Atmosphere 2023, 14(3), 606; https://doi.org/10.3390/atmos14030606 - 22 Mar 2023

Cited by 6 | Viewed by 2763

Abstract

Trees play a key role in mitigating urban heat by cooling the local environment. This study evaluated the extent to which street trees can reduce sub-canopy air temperature relative to ambient conditions (ΔT), and how ΔT relates to tree traits and microclimatic variables. [...] Read more.

Trees play a key role in mitigating urban heat by cooling the local environment. This study evaluated the extent to which street trees can reduce sub-canopy air temperature relative to ambient conditions (ΔT), and how ΔT relates to tree traits and microclimatic variables. Air temperature under the canopies of 10 species was recorded within residential areas in Western Sydney, Australia, during summer 2019–2020. Tree and canopy traits, namely tree height, specific leaf area, leaf dry matter content, leaf area index, crown width and the Huber value (the ratio of sapwood area to leaf area) were then measured for all species. Species differed significantly in their ΔT values, with peak cooling (maximum ΔT −3.9 °C) observed between 9–10 am and sub-canopy warming (i.e., positive ΔT values) typically occurring during afternoon and overnight. Trees with high LAI and wider canopies were associated with the greatest daytime cooling benefits and lower levels of nighttime warming. ΔT was also negatively related to windspeed and vapor pressure deficit, and positively to solar irradiance. This study provides valuable information on how tree characteristics and microclimate influence potential cooling benefits that may aid planning decisions on the use of trees to mitigate heat in urban landscapes. Full article

(This article belongs to the Special Issue Strategies for Mitigation and Adaptation to Urban Heat)

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26 pages, 34335 KiB

Open AccessArticle

Landscape Configuration Effects on Outdoor Thermal Comfort across Campus—A Case Study

by Shaojie Zhang, Shanzhi Li, Ling Shu, Tieqiao Xiao and Taotao Shui

Atmosphere 2023, 14(2), 270; https://doi.org/10.3390/atmos14020270 - 29 Jan 2023

Cited by 7 | Viewed by 2383

Abstract

As a main place for student activities on campus, outdoor spaces have positive impacts on students’ physical and mental health. Namely, outdoor heat and comfort are of great significance to improve activity quality. Here, four unique outdoor spaces were studied to explore the [...] Read more.

As a main place for student activities on campus, outdoor spaces have positive impacts on students’ physical and mental health. Namely, outdoor heat and comfort are of great significance to improve activity quality. Here, four unique outdoor spaces were studied to explore the varying effects on human thermal comfort during hot-summer and cold-winter periods. Distinct outdoor spaces (fully open, semi-open, semi-enclosed, and fully enclosed areas) from the southern campus of Anhui Jianzhu University were chosen. The PET was used as a metric for measuring thermal comfort and analyzing correlated spatiotemporal distributions. The results showed that outdoor thermal comfort was derived from multiple factors, including vegetation, underlying surface materials, building presence, and wind-heat environment. Notably, high correlations between Tmrt and thermal comfort were revealed, where such temperatures of places with trees or building shade were low; thus, PET was low. Further, Ws showed a significantly negative correlation with PET. Of the four outdoor space forms, the fully enclosed location had the lowest thermal comfort level, while the semi-enclosed spaces showed the highest level of body comfort. Therefore, semi-enclosed space (U-shaped) is recommended in campus planning and construction. Accordingly, an improved strategy was proposed based on experimental transformation for fully enclosed spaces. The thermal comfort after optimization was simulated to provide references for outdoor space thermal comfort improvement during seasonal extremes. Full article

(This article belongs to the Special Issue Strategies for Mitigation and Adaptation to Urban Heat)

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18 pages, 6586 KiB

Open AccessArticle

Analysis of Changes in Vegetation Index during the Rapid Urban Spatial Development Period (1990–2020) in Tehran Metropolis, Iran

by Alizadeh Shahin Zenouzi, Komali Yenneti, Raziyeh Teimouri, Fatemeh Abbasiyan and Massimo Palme

Atmosphere 2022, 13(12), 2010; https://doi.org/10.3390/atmos13122010 - 30 Nov 2022

Cited by 4 | Viewed by 1779

Abstract

Rapid urbanisation, economic growth, and urban spatial development in developing countries, such as Iran, have resulted in tremendous loss of green cover and associated ecological problems. Any effort to achieve sustainable urban development should be supported by recognising and evaluating the ecological health [...] Read more.

Rapid urbanisation, economic growth, and urban spatial development in developing countries, such as Iran, have resulted in tremendous loss of green cover and associated ecological problems. Any effort to achieve sustainable urban development should be supported by recognising and evaluating the ecological health of vegetation cover. This study investigates vegetation cover reduction and changes in the Tehran Metropolis, Iran and identifies the most important factors influencing the observed changes. The aim of this study is two-fold: first, to assess the spatio-temporal changes in vegetation cover in Tehran between 1990 and 2020, and second, to identify the factors contributing to the changes. The Normalised Difference Vegetation Index (NDVI) is used as an indicator of green cover. The spatial and statistical data used in this study were extracted from Landsat satellite imagery and the last approved Master Plan of Tehran (2006). Geographically Weighted Regression (GWR) and geographical modelling methods were employed to analyse vegetation cover in all municipal districts of the Tehran metropolis. The results show that the vegetation density in the Tehran metropolis decreased significantly (from 38,936.80 hectares to 4663.23 hectares) between 1990 and 2020. The expansion of construction lands and the increase of population density were the most significant factors affecting the reduction in vegetation cover in Tehran. In contrast, the growth of industrial units in the urban areas of Tehran had no significant relationship with vegetation cover. The results of this study can help urban planners understand the significant drivers of vegetation loss and identify appropriate interventions to prevent it. Full article

(This article belongs to the Special Issue Strategies for Mitigation and Adaptation to Urban Heat)

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16 pages, 3815 KiB

Open AccessArticle

Research on Outdoor Thermal Comfort and Activities in Residential Areas in Subtropical China

by Yuwan Deng, Dexin Gan, Na Tang, Zhengwu Cai, Xinyi Li, Simin Chen and Xiaoma Li

Atmosphere 2022, 13(9), 1357; https://doi.org/10.3390/atmos13091357 - 25 Aug 2022

Cited by 6 | Viewed by 1767

Abstract

Public spaces in residential areas are the main places for the daily activities of residents, and thermally comfortable activity space is particularly important for promoting the activities and public health of residents. Previous studies have mostly focused on tropical regions, with less research [...] Read more.

Public spaces in residential areas are the main places for the daily activities of residents, and thermally comfortable activity space is particularly important for promoting the activities and public health of residents. Previous studies have mostly focused on tropical regions, with less research on outdoor thermal comfort in subtropical regions. In this study, we aimed to investigate outdoor thermal benchmarks and outdoor activities in summer subtropical residential areas. Through physical measurements, questionnaires, and field observations, four residential areas in Changsha city were studied. The outdoor thermal comfort and activity of residents were studied with the physiological equivalent temperature (PET) as a model. The results showed that: (1) the neutral PET and neutral PET ranges for residents were 26.2 °C and 24.7–27.8 °C, respectively, and the range of 90% acceptable PET was lower than 28.5 °C; (2) globe temperature and air temperature were the primary factors influencing the thermal sensation of the residents; and (3) residents adapted to the thermal environment by adjusting their activity time and space in summer. These results help us to better understand the outdoor thermal comfort and activities of people living in subtropical regions and can provide guidance for the design of future residential open spaces. Full article

(This article belongs to the Special Issue Strategies for Mitigation and Adaptation to Urban Heat)

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28 pages, 4442 KiB

Open AccessEditor’s ChoiceArticle

Urban Heat Island and Thermal Comfort Assessment in a Medium-Sized Mediterranean City

by Georgios Kalogeropoulos, Argiro Dimoudi, Pavlos Toumboulidis and Stamatis Zoras

Atmosphere 2022, 13(7), 1102; https://doi.org/10.3390/atmos13071102 - 13 Jul 2022

Cited by 8 | Viewed by 2781

Abstract

One of the greatest issues nowadays is that of the urban heat island effect on the thermal conditions inside cities. The air temperature inside the city core is warmer than that in suburbs, thus deteriorating the quality of life for citizens and making [...] Read more.

One of the greatest issues nowadays is that of the urban heat island effect on the thermal conditions inside cities. The air temperature inside the city core is warmer than that in suburbs, thus deteriorating the quality of life for citizens and making outdoor spaces uncomfortable in terms of thermal comfort. This phenomenon is usually assessed in large scale cities worldwide and less often in medium-sized towns. The current study aimed to investigate the urban heat island effect and, therefore, to assess the outdoor thermal comfort conditions in a medium-sized city. More specifically, the methodology of the current study includes: (i) the combination of different monitoring techniques to quantify the urban heat island effect in a medium-sized Mediterranean city. Both in situ measurements and remote sensing techniques were applied to assess the urban heat island effect in terms of both the canopy layer (CUHI) and the surface (SUHI); (ii) the identification of the parameters that affect thermal comfort and the identification of the most appropriate bioclimatic indices that determine outdoor thermal comfort in the city of interest. Both questionnaire survey and in situ measurements took place on a sidewalk in the city of Xanthi, Northern Greece, during the summer. The CUHI effect was obvious, especially in the morning and afternoon. Downscaled MODIS satellite images also showed that the intensity of SUHI was higher in the morning and afternoon. Apart from air temperature, important differences in the values of most microclimatic parameters were recorded between the meteorological station placed inside the urban area and those gathered from a nearby meteorological station. The narrow roads, the thermal properties of construction materials, and the absence of greenery characterized the area of interest and may be the key factors creating these differences in climate. Concerning the thermal comfort assessment, the most significant parameters were the air temperature and solar radiation, although, both empirical and direct indices were found to describe the comfort values well. According to the results, downscaling techniques are also important for the SUHI effect to be investigating in detail in medium-sized urban environments. Full article

(This article belongs to the Special Issue Strategies for Mitigation and Adaptation to Urban Heat)

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12 pages, 6600 KiB

Open AccessArticle

Study on Strategies to Implement Adaptation Measures for Extreme High Temperatures into the Street Canyon

by Hideki Takebayashi, Hiroki Danno and Ushio Tozawa

Atmosphere 2022, 13(6), 946; https://doi.org/10.3390/atmos13060946 - 10 Jun 2022

Cited by 1 | Viewed by 1325

Abstract

The purpose of this study is to evaluate the potential for using the spaces integrating the roads and sidewalks in the street canyon as human-centered spaces, and to investigate more appropriate measures to improve the thermal environment for pedestrians and visitors in these [...] Read more.

The purpose of this study is to evaluate the potential for using the spaces integrating the roads and sidewalks in the street canyon as human-centered spaces, and to investigate more appropriate measures to improve the thermal environment for pedestrians and visitors in these spaces. Based on the spatial distribution of SET* throughout the day, as possible human-centered street space uses, north–south streets with restricted widths and south sidewalks on east–west streets are candidates. Spatiotemporal distributions of SET* were calculated when water was sprinkled on the road surface in the street canyon and when water surface, sunshade, and trees were introduced in the street canyon. Assuming people walk or stay on the water surface, the MRT decreases, causing SET* to be below 31.5 °C at any time, so if a continuous supply of water is guaranteed and people can approach the water surface, the water surface can be expected to have a significant impact anywhere at any time. On the east–west street, shading by sunshades and trees occurs along the lanes at any time, allowing pedestrians moving through the lanes to pass through the shaded areas on a periodic cycle. On north–south street, the time required for the countermeasures is limited to around noon, so the measure is effective even if the shade does not occur in the target lanes only around noon. Full article

(This article belongs to the Special Issue Strategies for Mitigation and Adaptation to Urban Heat)

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