In recent decades, Urban Heat Island Effects have become more pronounced and more widely examined. Despite great technological advances, our current societies still experience great spatial disparity in urban forest a...In recent decades, Urban Heat Island Effects have become more pronounced and more widely examined. Despite great technological advances, our current societies still experience great spatial disparity in urban forest access. Urban Heat Island Effects are measurable phenomenon that are being experienced by the world’s most urbanized areas, including increased summer high temperatures and lower evapotranspiration from having impervious surfaces instead of vegetation and trees. Tree canopy cover is our natural mitigation tool that absorbs sunlight for photosynthesis, protects humans from incoming radiation, and releases cooling moisture into the air. Unfortunately, urban areas typically have low levels of vegetation. Vulnerable urban communities are lower-income areas of inner cities with less access to heat protection like air conditioners. This study uses mean evapotranspiration levels to assess the variability of urban heat island effects across the state of Tennessee. Results show that increased developed land surface cover in Tennessee creates measurable changes in atmospheric evapotranspiration. As a result, the mean evapotranspiration levels in areas with less tree vegetation are significantly lower than the surrounding forested areas. Central areas of urban cities in Tennessee had lower mean evapotranspiration recordings than surrounding areas with less development. This work demonstrates the need for increased tree canopy coverage.展开更多
Alterations made to the natural ground surface and the anthropogenic activity elevate the surface and air temperature in the urban areas compared with the surrounding rural areas,known as urban heat island effect.Ther...Alterations made to the natural ground surface and the anthropogenic activity elevate the surface and air temperature in the urban areas compared with the surrounding rural areas,known as urban heat island effect.Thermal remote sensors measure the radiation emitted by ground objects,which can be used to estimate the land surface temperature and are beneficial for studying urban heat island effects.The present study investigates the spatial and temporal variations in the effects of urban heat island over Tiruchirappalli city in India during the summer and winter seasons.The study also identifies hot spots and cold spots within the study area.In this study,a significant land surface temperature difference was observed between the urban and rural areas,predominantly at night,indicating the presence of urban heat island at night.These diurnal land surface temperature fluctuations are also detected seasonally,with a relatively higher temperature intensity during the summer.The trend line analysis shows that the mean land surface temperature of the study area is increasing at a rate of 0.166 K/decade with p less than 0.01.By using the spatial autocorrelation method with the urban heat island index as the key parameter,hot spots with a 99 percent confidence level and a 95 percent confidence level were found within the urban area.A hot spot with 95 and 90 percent confidence level was identified outside the urban area.This spike in temperature for a particular region in the rural area is due to industry and the associated built-up area.The study also identified cold spots with a 90 percent confidence level within the rural area.However,cold spots with a 95 and 99 percent confidence level were not identified within the study area.展开更多
With the advancement of urbanization,the urban heat island effect and ozone pollution have become hot issues in urban research.The urban heat island effect can impact ozone conversion,but its mechanism of action is un...With the advancement of urbanization,the urban heat island effect and ozone pollution have become hot issues in urban research.The urban heat island effect can impact ozone conversion,but its mechanism of action is unclear.In this study,the effects of the urban heat island effect on ozone concentration in Chengdu City,China,were investigated by comparing the ozone concentration under different heat island levels with ozone data from March 2020 to February 2021 and the temperature and wind field data of ERA5-Land during the same period.The results showed that:1)regarding the distribution characteristics,the ozone concentration in Chengdu presented a‘high in summer and low in winter’distribution.The ozone concentration in summer(189.54µg/m^(3))was nearly twice that in winter(91.99µg/m^(3)),and the ozone diurnal variation presented a‘single peak and single valley’distribution,with a peak at 16:00.2)For the characteristics of the heat island effect,the heat island intensity in Chengdu was obviously higher in spring than in other seasons,and the diurnal variation showed a‘single peak and single valley’distribution,with the peak and trough values appearing at 9:00 and 17:00,respectively.Spatially,the eastern part of Chengdu was a heat island,while the western and northwestern parts were mostly cold island.3)The correlation analysis between heat island intensity and ozone concentration showed a significant positive correlation but with a 7–8 h time lag.Ambient air temperature was not the main factor affecting ozone concentration.The heat island effect impacts the ozone concentration in two ways:changing the local heat budget to promote ozone generation and forming local urban wind,which promotes ozone diffusion or accumulation and forms different areas of low and high ozone values.展开更多
Based on the local climate zoning theory and the observation data of hourly temperature of 22 automatic weather stations from 2012 to 2021, K-means clustering algorithm was used to analyze the daily, monthly, seasonal...Based on the local climate zoning theory and the observation data of hourly temperature of 22 automatic weather stations from 2012 to 2021, K-means clustering algorithm was used to analyze the daily, monthly, seasonal, annual and spatial variation characteristics of urban heat island effect in Weihai City in the past 10 years. The results showed that in recent 10 years, the average urban heat island intensity was 1.24 ℃, showing a gradual weakening trend of -0.169 3 ℃/10 a;the summer average heat island intensity was 0.86 ℃, showing a gradual weakening trend of -0.047 5 ℃/10 a. The heat island intensity had obvious diurnal variation characteristics, that is, "it was weak in the day and strong at night". In terms of seasonal variation, heat island effect was the weakest in summer, stronger in spring and autumn, and the strongest in winter. The diurnal, seasonal and annual changes of heat island intensity showed a reverse trend to those of temperature. The high-value area of urban heat island was highly consistent with human residential activity areas and industrial and commercial intensive areas, and the extension trend of heat island intensity was the same as the direction of urban development and construction. The "cold island phenomenon" in some offshore areas was related to the geographical location, terrain and the southeast monsoon trend in summer. The adverse effects of urban heat island effect can be reduced by optimizing the types and distribution of vegetation communities, rationally planning and constructing urban water body, promoting green building materials and adjusting shape design, etc.展开更多
[Objective] The aim was to analyse the variation characteristics of temperature in Anqing City and urban heat island effect.[Method] Based on the observation data of temperature from Anqing Station,other surrounding m...[Objective] The aim was to analyse the variation characteristics of temperature in Anqing City and urban heat island effect.[Method] Based on the observation data of temperature from Anqing Station,other surrounding meteorological stations and local automatic meteorological stations in suburbs,the annual variation of temperature and regional consistency was analysed,then the abrupt change of annual average temperature was tested by Mann-Kendall test,finally the influences of urban heat island effect on temperature variation in Anqing Station were studied.[Result] Affected by station migration and urban construction,the annual average temperature increased significantly in Anqing Station from 1977 to 2009,and the rising was more prominent after the middle of the 1990s.Mann-Kendall test showed that the change of temperature in Anqing Station was obviously abrupt around 1993;because of the development of urbanization,average temperature in Anqing Station was 0.8 ℃ higher than that in suburbs,and the minimum temperature rose more remarkably.In addition,urban heat island effect was the strongest in spring,followed by summer and autumn,while it was the weakest in winter.[Conclusion] The effects of urbanization development on the temperature in Anqing City were understood through this research.展开更多
This paper analyzes the Urban Heat Island (UHI) effect in Lhasa City of Tibet using meteorological observations, the Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST) data obtained fr...This paper analyzes the Urban Heat Island (UHI) effect in Lhasa City of Tibet using meteorological observations, the Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST) data obtained from Earth Observing System/Moderate resolution Imaging Spectroradiometer (EOS/MODIS) information, and correlation and composite analyses. The results show: (1) Areas with high temperature are primarily located in the center of the city or nearby counties, while low temperature areas are in the suburbs of counties. The area with high temperature has expanded in recent years and some high-temperature centers have even migrated to certain other regions. (2) The UHI intensity tends to be stronger both in annual and seasonal variations, especially in winter. Also, LST is somewhat positively related to mean air temperature. (3) A negative correlation exists between the changes of LST and NDVI with the increase of vegetation from urban to rural areas in different seasons. (4) The UHI intensity is negatively correlated with precipitation while positively correlated with wind speed, and the relation between the UHI intensity and evaporation varies with the seasons, namely, the intensity is positively correlated with summer evaporation but negatively corre- lated with winter evaporation. (5) UHI intensity might be enhanced by intensified urbanization, wherein built-up areas expand, there is increased heat from human activity, and there is more artificial heat input to the atmosphere.展开更多
The cold-island effect of urban wetlands has received increasing attention in recent years due to its important role in the alleviation of urban heat islands.Hangzhou,a representative rapidly urbanizing city with rich...The cold-island effect of urban wetlands has received increasing attention in recent years due to its important role in the alleviation of urban heat islands.Hangzhou,a representative rapidly urbanizing city with rich wetlands in China,was selected as a case study for researching the changes that the urban wetlands have undergone and their impact on the urban thermal environment.Land surface temperature(LST) was acquired from the thermal infrared data of Landsat 5 Thematic Mapper(TM) images in 1990,1995,2000,2006,and 2010,using the single-channel method.The results are as follows:1) considering the changes in land use,the urban wetlands located to the west of Hangzhou have decreased significantly during 1990–2010 because of rapid urbanization.In the Xixi Wetland,the change in land use was relatively small and most of the water body and vegetation were preserved.However,to the east of the Xixi Wetland,large areas of water body and vegetation have been replaced by built-up land as a result of the urbanization process;2) considering the change in LST,it was found from land surface temperature retrieval that the changing spatial pattern of the thermal field was highly correlated with land use changes.Low temperature regions of the eastern Xixi Wetland were gradually eroded by high temperature regions,and the centroid of the heat island in East Xixi was found to be constantly shifting westward.In addition,the difference in LST between the Xixi Wetland and East Xixi has increased;3) considering the impact factors for this area,land use structure and patch shape were found to have a significant impact on LST,shown by the results of multiple linear stepwise regressions.Increasing the size of the wetlands in urban planning is considered to be the most effective measure in alleviating the urban heat island effect.Moreover,reducing the spatial complexity of landscape patches also contributes to the alleviation of the urban heat island effect.展开更多
According to the data in the past nine years in Heyuan urban district and its adjacent five counties,annual,seasonal and monthly change characteristics of heat island effect in Heyuan City and its meteorological influ...According to the data in the past nine years in Heyuan urban district and its adjacent five counties,annual,seasonal and monthly change characteristics of heat island effect in Heyuan City and its meteorological influence factors were analyzed. The results showed that the intensity of heat island effect in central urban district and suburb of Heyuan City overall showed an upward trend from 2007 to 2015. From 2007 to 2012,heat island effect showed a slow weakening trend; from 2012 to 2013,heat island effect significantly enhanced and then weakened; after 2013,heat island effect significantly reduced. Heat island effect of Heyuan was the strongest in winter,followed by autumn,and it was the weakest in summer.The strongest heat island effect occurred in October,while the weakest occurred in July. According to the grey correlation analysis,the main factors affecting urban heat island effect of Heyuan were analyzed,and the order of each influence factor was as follows: average wind speed > relative humidity > rainfall > sunshine hours.展开更多
[Objective] The study aims at conducting the inversion of urban heat island effect in Xi'an City. [Method] Based on the United States Landsat-7 ETM~ and TM data in different phases, the spatial distribution and chang...[Objective] The study aims at conducting the inversion of urban heat island effect in Xi'an City. [Method] Based on the United States Landsat-7 ETM~ and TM data in different phases, the spatial distribution and changing trends of urban heat island effect in Xi'an City were ana- lyzed, and some corresponding measures to relieve the heat island effect in Xran were put forward according to its spatial distribution and intensity changes. [ Result] Urban heat island effect was very obvious in Xi'an City, that is, surface temperature of urban areas was distinctly higher than that of surrounding suburban areas, and the high-temperature region was akin to an island with a clear boundary. As the enlarging of Xi'an City, the areas subjected to heat island effect expended toward the south and north especially. In addition, heat island effect of Lantian District became more prominent, so it should be paid more attention to. We suggest that some measures like improving urban vegetation coverage, reasonably planing urban buildings, reducing the discharge of man-made heat, preventing and controlling atmospheric pollution should be adopted to control urban heat island effect of Xi'an City effectively. [ Concision] The study could offer theoretical references for the control of urban heat island effect and the im- provement of ecological environment in Xi'an City.展开更多
This study aims to propose a method for quantitatively evaluating the influence which the obstruction of sea breezes by clusters of high-rise buildings has on the urban heat island effect using a weather simulation mo...This study aims to propose a method for quantitatively evaluating the influence which the obstruction of sea breezes by clusters of high-rise buildings has on the urban heat island effect using a weather simulation model and Geographic Information Systems (GIS). Specifically, a method of evaluating the influence of the obstruction of sea breeze by high-rise buildings on the urban heat island effect was proposed. In the method, two scenarios that imagine urban forms which differ with regard to whether or not they contain high-rise buildings are created and weather simulation is conducted, and the results of the simulations are comparatively analyzed focusing on temperature and wind speed. Evaluation was conducted in two stages, and Shiodome of Minato City in the Tokyo Metropolis was selected as the region for evaluation. In two stages of evaluation, a rise in temperature of approximately 0.3 K and a reduction in wind speed of approximately 1 m/s were observed in a region approximately five to ten kilometers square downwind of high-rise buildings in the period 6 PM to 9 PM, and a higher temperature caused by the obstruction of sea breeze by high-rise buildings was identified. The fact that such a higher temperature was confirmed in the time period from 6 PM onwards, in which the temperature decreases, reveals that obstruction of sea breeze by high-rise buildings dulls the decrease in temperature which occurs from evening onwards, and influences nighttime urban heat island formation.展开更多
Urban centers are consistently exhibiting higher temperature than its surrounding suburban rural areas. The large amount of heat generated from urban structures such as road materials and pavement materials and other ...Urban centers are consistently exhibiting higher temperature than its surrounding suburban rural areas. The large amount of heat generated from urban structures such as road materials and pavement materials and other anthropogenic heat sources are the main causes of Urban Heat Island (UHI). The sources of data for this research included primary and secondary sources. Other techniques employed for data collection were direct measurement and readings on the road and pavement materials. The research found out that, there was consistency in rising temperature at different time of the day by the different road and pavement materials. Asphalt has the greatest effect of increasing the urban temperature four degrees higher, followed by concrete, three degree rise in temperature, and earth (ordinary ground) by two degree rise and vegetation (grass) by one degree rise in temperature. The overall effect on the residents of the study area ranges from increase in hotness of the day;44.6% respondents agrees;while 34.3% says it affects the ambient air quality of the area, and other effects such as increased ground level ozone, suffocation, sleeplessness and restlessness as a result of excessive high temperature especially at night are identified in this paper. The research recommends the review or redesigning of the entire Port Harcourt city Master Plan to make provision for creation of more green areas rather than pavements and concreted areas to reduce the effects of (UHI) and ultimately improve the comfort and living conditions of the people in a the garden city Port Harcourt.展开更多
This paper sets out the preliminary results of an experimental research plan aimed at analysing the thermal processes inherent to the urbanisation effect. Although this effect is undeniable, the extent of its impact i...This paper sets out the preliminary results of an experimental research plan aimed at analysing the thermal processes inherent to the urbanisation effect. Although this effect is undeniable, the extent of its impact is a matter of controversy. The results obtained in this study show both the nature of the phenomenon and its considerable magnitude. Failure to take this process into account might seriously bias any analysis of thermal evolution, the cornerstone of the climate change hypothesis.展开更多
文摘In recent decades, Urban Heat Island Effects have become more pronounced and more widely examined. Despite great technological advances, our current societies still experience great spatial disparity in urban forest access. Urban Heat Island Effects are measurable phenomenon that are being experienced by the world’s most urbanized areas, including increased summer high temperatures and lower evapotranspiration from having impervious surfaces instead of vegetation and trees. Tree canopy cover is our natural mitigation tool that absorbs sunlight for photosynthesis, protects humans from incoming radiation, and releases cooling moisture into the air. Unfortunately, urban areas typically have low levels of vegetation. Vulnerable urban communities are lower-income areas of inner cities with less access to heat protection like air conditioners. This study uses mean evapotranspiration levels to assess the variability of urban heat island effects across the state of Tennessee. Results show that increased developed land surface cover in Tennessee creates measurable changes in atmospheric evapotranspiration. As a result, the mean evapotranspiration levels in areas with less tree vegetation are significantly lower than the surrounding forested areas. Central areas of urban cities in Tennessee had lower mean evapotranspiration recordings than surrounding areas with less development. This work demonstrates the need for increased tree canopy coverage.
基金funded this research through grant NITT/R&C/SEED GRANT/2021e22/P.14.
文摘Alterations made to the natural ground surface and the anthropogenic activity elevate the surface and air temperature in the urban areas compared with the surrounding rural areas,known as urban heat island effect.Thermal remote sensors measure the radiation emitted by ground objects,which can be used to estimate the land surface temperature and are beneficial for studying urban heat island effects.The present study investigates the spatial and temporal variations in the effects of urban heat island over Tiruchirappalli city in India during the summer and winter seasons.The study also identifies hot spots and cold spots within the study area.In this study,a significant land surface temperature difference was observed between the urban and rural areas,predominantly at night,indicating the presence of urban heat island at night.These diurnal land surface temperature fluctuations are also detected seasonally,with a relatively higher temperature intensity during the summer.The trend line analysis shows that the mean land surface temperature of the study area is increasing at a rate of 0.166 K/decade with p less than 0.01.By using the spatial autocorrelation method with the urban heat island index as the key parameter,hot spots with a 99 percent confidence level and a 95 percent confidence level were found within the urban area.A hot spot with 95 and 90 percent confidence level was identified outside the urban area.This spike in temperature for a particular region in the rural area is due to industry and the associated built-up area.The study also identified cold spots with a 90 percent confidence level within the rural area.However,cold spots with a 95 and 99 percent confidence level were not identified within the study area.
基金Under the auspices of the National Science Foundation of Sichuan Province(No.2022NSFSC1006)Science and Technology Innovation Capability Improvement Plan Project of Chengdu University of Information Technology in 2022(No.KYQN202215)the National Science Foundation of China(No.41505122)。
文摘With the advancement of urbanization,the urban heat island effect and ozone pollution have become hot issues in urban research.The urban heat island effect can impact ozone conversion,but its mechanism of action is unclear.In this study,the effects of the urban heat island effect on ozone concentration in Chengdu City,China,were investigated by comparing the ozone concentration under different heat island levels with ozone data from March 2020 to February 2021 and the temperature and wind field data of ERA5-Land during the same period.The results showed that:1)regarding the distribution characteristics,the ozone concentration in Chengdu presented a‘high in summer and low in winter’distribution.The ozone concentration in summer(189.54µg/m^(3))was nearly twice that in winter(91.99µg/m^(3)),and the ozone diurnal variation presented a‘single peak and single valley’distribution,with a peak at 16:00.2)For the characteristics of the heat island effect,the heat island intensity in Chengdu was obviously higher in spring than in other seasons,and the diurnal variation showed a‘single peak and single valley’distribution,with the peak and trough values appearing at 9:00 and 17:00,respectively.Spatially,the eastern part of Chengdu was a heat island,while the western and northwestern parts were mostly cold island.3)The correlation analysis between heat island intensity and ozone concentration showed a significant positive correlation but with a 7–8 h time lag.Ambient air temperature was not the main factor affecting ozone concentration.The heat island effect impacts the ozone concentration in two ways:changing the local heat budget to promote ozone generation and forming local urban wind,which promotes ozone diffusion or accumulation and forms different areas of low and high ozone values.
基金Supported by the Science and Technology Research Project of Shandong Meteorological Bureau(2022SDQN17).
文摘Based on the local climate zoning theory and the observation data of hourly temperature of 22 automatic weather stations from 2012 to 2021, K-means clustering algorithm was used to analyze the daily, monthly, seasonal, annual and spatial variation characteristics of urban heat island effect in Weihai City in the past 10 years. The results showed that in recent 10 years, the average urban heat island intensity was 1.24 ℃, showing a gradual weakening trend of -0.169 3 ℃/10 a;the summer average heat island intensity was 0.86 ℃, showing a gradual weakening trend of -0.047 5 ℃/10 a. The heat island intensity had obvious diurnal variation characteristics, that is, "it was weak in the day and strong at night". In terms of seasonal variation, heat island effect was the weakest in summer, stronger in spring and autumn, and the strongest in winter. The diurnal, seasonal and annual changes of heat island intensity showed a reverse trend to those of temperature. The high-value area of urban heat island was highly consistent with human residential activity areas and industrial and commercial intensive areas, and the extension trend of heat island intensity was the same as the direction of urban development and construction. The "cold island phenomenon" in some offshore areas was related to the geographical location, terrain and the southeast monsoon trend in summer. The adverse effects of urban heat island effect can be reduced by optimizing the types and distribution of vegetation communities, rationally planning and constructing urban water body, promoting green building materials and adjusting shape design, etc.
文摘[Objective] The aim was to analyse the variation characteristics of temperature in Anqing City and urban heat island effect.[Method] Based on the observation data of temperature from Anqing Station,other surrounding meteorological stations and local automatic meteorological stations in suburbs,the annual variation of temperature and regional consistency was analysed,then the abrupt change of annual average temperature was tested by Mann-Kendall test,finally the influences of urban heat island effect on temperature variation in Anqing Station were studied.[Result] Affected by station migration and urban construction,the annual average temperature increased significantly in Anqing Station from 1977 to 2009,and the rising was more prominent after the middle of the 1990s.Mann-Kendall test showed that the change of temperature in Anqing Station was obviously abrupt around 1993;because of the development of urbanization,average temperature in Anqing Station was 0.8 ℃ higher than that in suburbs,and the minimum temperature rose more remarkably.In addition,urban heat island effect was the strongest in spring,followed by summer and autumn,while it was the weakest in winter.[Conclusion] The effects of urbanization development on the temperature in Anqing City were understood through this research.
基金supported by programs of the Institute of Urban Meteorology (No. UMRF200705)the China Meteorological Administration (No. CMATG2010M24)the Institute of Plateau Meteorology (No. BROP200705)
文摘This paper analyzes the Urban Heat Island (UHI) effect in Lhasa City of Tibet using meteorological observations, the Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST) data obtained from Earth Observing System/Moderate resolution Imaging Spectroradiometer (EOS/MODIS) information, and correlation and composite analyses. The results show: (1) Areas with high temperature are primarily located in the center of the city or nearby counties, while low temperature areas are in the suburbs of counties. The area with high temperature has expanded in recent years and some high-temperature centers have even migrated to certain other regions. (2) The UHI intensity tends to be stronger both in annual and seasonal variations, especially in winter. Also, LST is somewhat positively related to mean air temperature. (3) A negative correlation exists between the changes of LST and NDVI with the increase of vegetation from urban to rural areas in different seasons. (4) The UHI intensity is negatively correlated with precipitation while positively correlated with wind speed, and the relation between the UHI intensity and evaporation varies with the seasons, namely, the intensity is positively correlated with summer evaporation but negatively corre- lated with winter evaporation. (5) UHI intensity might be enhanced by intensified urbanization, wherein built-up areas expand, there is increased heat from human activity, and there is more artificial heat input to the atmosphere.
基金Under the auspices of National Natural Science Foundation of China(No.41101039,41371068)
文摘The cold-island effect of urban wetlands has received increasing attention in recent years due to its important role in the alleviation of urban heat islands.Hangzhou,a representative rapidly urbanizing city with rich wetlands in China,was selected as a case study for researching the changes that the urban wetlands have undergone and their impact on the urban thermal environment.Land surface temperature(LST) was acquired from the thermal infrared data of Landsat 5 Thematic Mapper(TM) images in 1990,1995,2000,2006,and 2010,using the single-channel method.The results are as follows:1) considering the changes in land use,the urban wetlands located to the west of Hangzhou have decreased significantly during 1990–2010 because of rapid urbanization.In the Xixi Wetland,the change in land use was relatively small and most of the water body and vegetation were preserved.However,to the east of the Xixi Wetland,large areas of water body and vegetation have been replaced by built-up land as a result of the urbanization process;2) considering the change in LST,it was found from land surface temperature retrieval that the changing spatial pattern of the thermal field was highly correlated with land use changes.Low temperature regions of the eastern Xixi Wetland were gradually eroded by high temperature regions,and the centroid of the heat island in East Xixi was found to be constantly shifting westward.In addition,the difference in LST between the Xixi Wetland and East Xixi has increased;3) considering the impact factors for this area,land use structure and patch shape were found to have a significant impact on LST,shown by the results of multiple linear stepwise regressions.Increasing the size of the wetlands in urban planning is considered to be the most effective measure in alleviating the urban heat island effect.Moreover,reducing the spatial complexity of landscape patches also contributes to the alleviation of the urban heat island effect.
文摘According to the data in the past nine years in Heyuan urban district and its adjacent five counties,annual,seasonal and monthly change characteristics of heat island effect in Heyuan City and its meteorological influence factors were analyzed. The results showed that the intensity of heat island effect in central urban district and suburb of Heyuan City overall showed an upward trend from 2007 to 2015. From 2007 to 2012,heat island effect showed a slow weakening trend; from 2012 to 2013,heat island effect significantly enhanced and then weakened; after 2013,heat island effect significantly reduced. Heat island effect of Heyuan was the strongest in winter,followed by autumn,and it was the weakest in summer.The strongest heat island effect occurred in October,while the weakest occurred in July. According to the grey correlation analysis,the main factors affecting urban heat island effect of Heyuan were analyzed,and the order of each influence factor was as follows: average wind speed > relative humidity > rainfall > sunshine hours.
文摘[Objective] The study aims at conducting the inversion of urban heat island effect in Xi'an City. [Method] Based on the United States Landsat-7 ETM~ and TM data in different phases, the spatial distribution and changing trends of urban heat island effect in Xi'an City were ana- lyzed, and some corresponding measures to relieve the heat island effect in Xran were put forward according to its spatial distribution and intensity changes. [ Result] Urban heat island effect was very obvious in Xi'an City, that is, surface temperature of urban areas was distinctly higher than that of surrounding suburban areas, and the high-temperature region was akin to an island with a clear boundary. As the enlarging of Xi'an City, the areas subjected to heat island effect expended toward the south and north especially. In addition, heat island effect of Lantian District became more prominent, so it should be paid more attention to. We suggest that some measures like improving urban vegetation coverage, reasonably planing urban buildings, reducing the discharge of man-made heat, preventing and controlling atmospheric pollution should be adopted to control urban heat island effect of Xi'an City effectively. [ Concision] The study could offer theoretical references for the control of urban heat island effect and the im- provement of ecological environment in Xi'an City.
文摘This study aims to propose a method for quantitatively evaluating the influence which the obstruction of sea breezes by clusters of high-rise buildings has on the urban heat island effect using a weather simulation model and Geographic Information Systems (GIS). Specifically, a method of evaluating the influence of the obstruction of sea breeze by high-rise buildings on the urban heat island effect was proposed. In the method, two scenarios that imagine urban forms which differ with regard to whether or not they contain high-rise buildings are created and weather simulation is conducted, and the results of the simulations are comparatively analyzed focusing on temperature and wind speed. Evaluation was conducted in two stages, and Shiodome of Minato City in the Tokyo Metropolis was selected as the region for evaluation. In two stages of evaluation, a rise in temperature of approximately 0.3 K and a reduction in wind speed of approximately 1 m/s were observed in a region approximately five to ten kilometers square downwind of high-rise buildings in the period 6 PM to 9 PM, and a higher temperature caused by the obstruction of sea breeze by high-rise buildings was identified. The fact that such a higher temperature was confirmed in the time period from 6 PM onwards, in which the temperature decreases, reveals that obstruction of sea breeze by high-rise buildings dulls the decrease in temperature which occurs from evening onwards, and influences nighttime urban heat island formation.
文摘Urban centers are consistently exhibiting higher temperature than its surrounding suburban rural areas. The large amount of heat generated from urban structures such as road materials and pavement materials and other anthropogenic heat sources are the main causes of Urban Heat Island (UHI). The sources of data for this research included primary and secondary sources. Other techniques employed for data collection were direct measurement and readings on the road and pavement materials. The research found out that, there was consistency in rising temperature at different time of the day by the different road and pavement materials. Asphalt has the greatest effect of increasing the urban temperature four degrees higher, followed by concrete, three degree rise in temperature, and earth (ordinary ground) by two degree rise and vegetation (grass) by one degree rise in temperature. The overall effect on the residents of the study area ranges from increase in hotness of the day;44.6% respondents agrees;while 34.3% says it affects the ambient air quality of the area, and other effects such as increased ground level ozone, suffocation, sleeplessness and restlessness as a result of excessive high temperature especially at night are identified in this paper. The research recommends the review or redesigning of the entire Port Harcourt city Master Plan to make provision for creation of more green areas rather than pavements and concreted areas to reduce the effects of (UHI) and ultimately improve the comfort and living conditions of the people in a the garden city Port Harcourt.
文摘This paper sets out the preliminary results of an experimental research plan aimed at analysing the thermal processes inherent to the urbanisation effect. Although this effect is undeniable, the extent of its impact is a matter of controversy. The results obtained in this study show both the nature of the phenomenon and its considerable magnitude. Failure to take this process into account might seriously bias any analysis of thermal evolution, the cornerstone of the climate change hypothesis.
文摘在气候变暖和快速城市化背景下,北京一直面临着城市热岛效应带来的环境问题。基于北京市1981—2020年逐日气温观测资料,采用线性回归、克里金插值和相关性分析等方法,研究了北京市城郊气温变化趋势以及北京市城市热岛强度(Urban Heat Island, UHI)的时空变化特征,并评估了气象因素、人口密度和土地利用/覆盖类型对城市热岛效应的影响。结果表明:近40 a来北京市城郊区的平均气温均呈上升的变化趋势,且城区气温增幅大于郊区,表明北京市UHI上升趋势显著。就季节而言,北京市冬季UHI最强(1.22℃),秋季次之,春、夏最弱,其中秋季UHI增幅最大。同时,北京市城市热岛效应范围也在逐渐扩大,其中城六区为高值区,热岛区由西北向东南方向延伸至城市副中心通州区,朝阳区和通州区增温趋势明显。2000年以来,北京市冬季UHI出现了显著的增加趋势,高值区UHI增加至1.6℃。此外,主成分分析表明人口、建设用地和气压对城市热岛效应的形成起促进作用,而风速和耕地是缓解城市热岛效应的重要影响因素。