scholarly journals Spatiotemporal patterns of urban thermal environment and comfort across 180 cities in summer under China’s rapid urbanization

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7424 ◽  
Author(s):  
Zhibin Ren ◽  
Yao Fu ◽  
Yunxia Du ◽  
Hongbo Zhao
Keyword(s):  
Thermal Comfort ◽  
Thermal Environment ◽  
Urban Climate ◽  
Spatiotemporal Patterns ◽  
Physiological Equivalent Temperature ◽  
Rapid Urbanization ◽  
Northern Cities ◽  
Changing Patterns ◽  
Urbanization In China ◽  
Urban Thermal Environment

Background China is considered as the largest and most rapidly urbanizing nation in the world. However, possible changes of urban thermal environment and comfort under the rapid urbanization in China still remain poorly understood at a national scale. Methods Based on the data collected from 180 cities in 1990, 2005, and 2015 in China, the spatiotemporal patterns of urban thermal environment and comfort in summer and their relationships with urbanization variables were investigated in this study. Results Our results indicate that urban thermal environment has changed greatly during the 25 years. Furthermore, the changes of urban climate in different regions are inconsistent. The Physiological Equivalent Temperature (PET) at most cities (81%) in China increased from 1990 to 2015, which suggested that urban thermal comfort in China was also deteriorating during the 25 years. However, while the PET of some cities in China began to decrease from 2005 to 2015, there were still 33% of cities that had positive trends,which mainly located in North region. Urbanization resulted in a significant influence on urban climate. Compared to southern cities, northern cities were more sensitive to urbanization impact. The most important contribution to increasing of PET for urbanization variables is gross domestic product, followed by urban population. The analysis results reveal changing patterns of urban thermal comfort in China during summer season. It can help urban government and managers improve urban thermal environment and comfort.

scholarly journals Long-term dynamics of urban thermal comfort in China’s four major capital cities across different climate zones

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e8026 ◽  
Author(s):  
Yao Fu ◽  
Zhibin Ren ◽  
Qiuyan Yu ◽  
Xingyuan He ◽  
Lu Xiao ◽  
...  
Keyword(s):  
Thermal Comfort ◽  
Thermal Environment ◽  
Meteorological Data ◽  
Economic Activities ◽  
Physiological Equivalent Temperature ◽  
Rapid Urbanization ◽  
Climate Zones ◽  
Chinese Cities ◽  
Northern Cities

China has experienced intensive urbanization over the past decades. However, it is still unclear about the influence of urbanization on urban thermal comfort and how the effect varies with climate condition. Based on long-term daily meteorological data from 1990 to 2015 in four Chinese cities undergoing rapid urbanization, our study tried to detect the long-term dynamics of summer urban thermal comfort across different climate zones and analyze their relationships with urbanization. Our results showed that urbanization can increase urban temperature and decrease relative humidity and wind velocity. Urban thermal comfort and discomfort days also changed greatly, especially in Harbin, Northeast China from 1990 to 2015. However, such changes for different cities across different climate zones are inconsistent. Results also showed that urbanization especially for social economic activities can have a significant influence on the physiological Equivalent Temperature (PET). Compared with southern cities, the PET in northern cities such as Harbin and Changchun in this study is more sensitive to urbanization. These results reveal that the changing patterns of urban thermal comfort in Chinese cities under rapid urbanization, and help government take some effective measures to improve urban thermal environment.

scholarly journals The Street Air Warming Phenomenon in a High-Rise Compact City

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 402 ◽  
Author(s):  
Xiaoxue Wang ◽  
Yuguo Li ◽  
Xinyan Yang ◽  
Pak Chan ◽  
Janet Nichol ◽  
...  
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Thermal Environment ◽  
Urban Climate ◽  
Pollutant Dispersion ◽  
Urban Morphology ◽  
Air Temperatures ◽  
Significant Difference ◽  
Sensitivity Studies ◽  
Weather Stations

The street thermal environment is important for thermal comfort, urban climate and pollutant dispersion. A 24-h vehicle traverse study was conducted over the Kowloon Peninsula of Hong Kong in summer, with each measurement period consisting of 2–3 full days. The data covered a total of 158 loops in 198 h along the route on sunny days. The measured data were averaged by three methods (direct average, FFT filter and interpolated by the piecewise cubic Hermite interpolation). The average street air temperatures were found to be 1–3 °C higher than those recorded at nearby fixed weather stations. The street warming phenomenon observed in the study has substantial implications as usually urban heat island (UHI) intensity is estimated from measurement at fixed weather stations, and therefore the UHI intensity in the built areas of the city may have been underestimated. This significant difference is of interest for studies on outdoor air temperature, thermal comfort, urban environment and pollutant dispersion. The differences were simulated by an improved one-dimensional temperature model (ZERO-CAT) using different urban morphology parameters. The model can correct the underestimation of street air temperature. Further sensitivity studies show that the building arrangement in the daytime and nighttime plays different roles for air temperature in the street. City designers can choose different parameters based on their purpose.

scholarly journals Landsat-Based Monitoring of the Heat Effects of Urbanization Directions and Types in Hangzhou City from 2000 to 2020

2021 ◽  
Vol 13 (21) ◽  
pp. 4268
Author(s):  
Lin Chen ◽  
Bin Zhou ◽  
Weidong Man ◽  
Mingyue Liu
Keyword(s):  
Urban Areas ◽  
Single Channel ◽  
Thermal Environment ◽  
Urban Expansion ◽  
Spatiotemporal Patterns ◽  
Annual Growth Rate ◽  
Impervious Surfaces ◽  
Rapid Urbanization ◽  
Heat Effects ◽  
Urban Heat

Rapid urbanization has produced serious heat effects worldwide. However, the literature lacks a detailed study on heat effects based on the directions and types of urban expansion. In this work, a typical city with an extremely hot summer climate, Hangzhou, was selected as a case study to determine the relationships between the urban heat-effect dynamics and spatiotemporal patterns of impervious surface expansion. Based on long-term Landsat imagery, this study characterized the spatiotemporal patterns of urban expansion and normalized surface temperatures in Hangzhou City from 2000 to 2020 using object-based backdating classification and a generalized single-channel algorithm with the help of a land-use transfer matrix, expansion index, and spatial centroids. Relevant policies, industries, and traffic networks were discussed to help explain urban expansion and thermal environment changes. The results demonstrated that in 2020, the area of impervious surfaces covered 1139.29 km2. The majority of the gains were in farmland, water, and forests, and the annual growth rate was 32.12 km2/year beginning in 2000. During the expansion of impervious surfaces, the city warmed at a slower rate, and more thermal contributions came from sub-urban areas. The southeast-oriented expansion of impervious surfaces was the key reason for the spatiotemporal dynamics of the urban heat effects. The dominant urban edge expansion intensified the local heat effects. This research provides a Landsat-based methodology for better understanding the heat effects of urban expansion.

scholarly journals Effects of urban street trees on human thermal comfort and physiological indices: a case study in Changchun city, China

2021 ◽  
Author(s):  
Zhibin Ren ◽  
Hongbo Zhao ◽  
Yao Fu ◽  
Lu Xiao ◽  
Yulin Dong
Keyword(s):  
Blood Pressure ◽  
Thermal Comfort ◽  
Thermal Environment ◽  
Physiological Parameters ◽  
Tree Cover ◽  
Street Trees ◽  
Urban Street ◽  
Human Thermal Comfort ◽  
Physiological Indices ◽  
Urban Thermal Environment

AbstractPlanting trees along urban streets is one of the most important strategies to improve the urban thermal environment. However, the net impacts of urban street trees on human thermal comfort and physiological parameters are still less clear. On three similar east–west orientated streets with different degrees of tree cover—low (13%), medium (35%), and high (75%), urban microclimatic parameters and human physiological indices for six male students were simultaneously measured on three cloudless days in summer 2018. The results show that the differences in tree cover were predominant in influencing urban thermal environment and comfort. The street with the highest tree cover had significantly lower physiological equivalent temperature (PET) and more comfortable than the other two streets. The frequency of strong heat stress (PET > 35 °C) was 64%, 11%, and 0%, respectively, for streets with low, medium, and high tree cover. For the six male university students, human physiological indices varied greatly across the three streets with different tree cover. Systolic blood pressure, diastolic blood pressure, and pulse rate increased with decreasing tree cover. The results also suggest that urban thermal environment and comfort had considerable impact on human physiological parameters. Our study provides reasons for urban planners to plant trees along streets to improve the thermal environment and promote urban sustainability.

scholarly journals Forecasting of outdoor thermal comfort index in urban open spaces: The Nis fortress case study

2016 ◽  
Vol 20 (suppl. 5) ◽  
pp. 1531-1539 ◽  
Author(s):  
Ivana Bogdanovic-Protic ◽  
Ana Vukadinovic ◽  
Jasmina Radosavljevic ◽  
Meysam Alizamirc ◽  
Mihajlo Mitkovic
Keyword(s):  
Thermal Comfort ◽  
Extreme Learning Machine ◽  
Computational Models ◽  
Thermal Environment ◽  
Outdoor Thermal Comfort ◽  
Special Importance ◽  
Equivalent Temperature ◽  
Machine Model ◽  
Physiological Equivalent Temperature ◽  
Learning Machine

Outdoor thermal environment is affected by variables like air temperature, wind velocity, humidity, temperature of the radiant surfaces, and solar radiation, which can be expressed by a single number - the thermal index. Since these variables are subject to annual and diurnal variations, prediction of thermal comfort is of special importance for people to plan their outdoor activities. The purpose of this research was to develop and apply the extreme learning machine for forecasting physiological equivalent temperature values. The results of the extreme learning machine model were compared with genetic programming and artificial neural network. The reliability of the computational models was accessed based on simulation results and using several statistical indicators. According to obtained results, it can be concluded that extreme learning machine can be utilized effectively in short term forecasting of physiological equivalent temperature.

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