scholarly journals Time-Series Analysis Reveals Intensified Urban Heat Island Effects but without Significant Urban Warming

2019 ◽  
Vol 11 (19) ◽  
pp. 2229 ◽  
Author(s):  
Jia Wang ◽  
Weiqi Zhou ◽  
Jing Wang
Keyword(s):  
Time Series ◽  
Urban Heat Island ◽  
Urban Areas ◽  
Temporal Trends ◽  
Heat Island ◽  
Entire Study ◽  
Urban Warming ◽  
Urban Heat ◽  
Surface Urban Heat Island ◽  
Cooling Effects

Numerous studies have shown an increased surface urban heat island intensity (SUHII) in many cities with urban expansion. Few studies, however, have investigated whether such intensification is mainly caused by urban warming, the cooling of surrounding nonurban regions, or the different rates of warming/cooling between urban and nonurban areas. This study aims to fill that gap using Beijing, China, as a case study. We first examined the temporal trends of SUHII in Beijing and then compared the magnitude of the land surface temperature (LST) trend in urban and nonurban areas. We further detected the temporal trend of LST (TrendLST) at the pixel level and explored its linkage to the temporal trends of EVI (TrendEVI) and NDBI (TrendNDBI). We used MODIS data from 2000 to 2015. We found that (1) SUHII significantly increased from 4.35 °C to 6.02 °C, showing an intensified surface urban heat island (SUHI) effect, with an annual increase rate of 0.13 °C in summer during the daytime and 0.04 °C in summer at night. In addition, the intensification of SUHII was more prominent in new urban areas (NUA). (2) The intensified SUHII, however, was largely caused by substantial cooling effects in nonurban areas (NoUA), not substantial warming in urban areas. (3) Spatially, there were large spatial variations in significant warming and cooling spots over the entire study area, which were related to TrendNDBI and TrendEVI. TrendNDBI significantly affected TrendLST in a positive way, while the TrendEVI had a significant positive effect (p = 0.023) on TrendLST only when EVI had an increasing trend. Our study underscores the importance of quantifying and comparing the changes in LST in both urban and nonurban areas when investigating changes in SUHII using time-series trend analysis. Such analysis can provide insights into promoting city-based urban heat mitigation strategies which focused on both urban and nonurban areas.

scholarly journals Nocturnal Surface Urban Heat Island over Greater Cairo: Spatial Morphology, Temporal Trends and Links to Land-Atmosphere Influences

2020 ◽  
Vol 12 (23) ◽  
pp. 3889
Author(s):  
Ahmed M. El Kenawy ◽  
Mohamed Hereher ◽  
Sayed M. Robaa ◽  
Matthew F. McCabe ◽  
Juan I. Lopez-Moreno ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Surface Albedo ◽  
Temporal Trends ◽  
Mitigation Strategies ◽  
Cold Spot ◽  
Heat Island ◽  
Time Step ◽  
Greater Cairo ◽  
Urban Heat ◽  
Surface Urban Heat Island

This study assesses the spatial and temporal characteristics of nighttime surface urban heat island (SUHI) effects over Greater Cairo: the largest metropolitan area in Africa. This study employed nighttime land surface temperature (LST) data at 1 km resolution from the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua sensor for the period 2003–2019. We presented a new spatial anomaly algorithm, which allowed to define SUHI using the most anomalous hotspot and cold spot of LST for each time step over Greater Cairo between 2003 and 2019. Results demonstrate that although there is a significant increase in the spatial extent of SUHI over the past two decades, a significant decrease in the mean and maximum intensities of SUHI was noted. Moreover, we examined the dependency between SUHI characteristics and related factors that influence energy and heat fluxes between atmosphere and land in urban environments (e.g., surface albedo, vegetation cover, climate variability, and land cover/use changes). Results demonstrate that the decrease in the intensity of SUHI was mainly guided by a stronger warming in daytime and nighttime LST in the neighborhood of urban localities. This warming was accompanied by a decrease in surface albedo and diurnal temperature range (DTR) over these areas. Results of this study can provide guidance to local urban planners and decision-makers to adopt more effective mitigation strategies to diminish the negative impacts of urban warming on natural and human environments.

scholarly journals A Comprehensive Statistical Study on Daytime Surface Urban Heat Island during Summer in Urban Areas, Case Study: Cairo and Its New Towns

2016 ◽  
Vol 8 (8) ◽  
pp. 643 ◽  
Author(s):  
Hamid Taheri Shahraiyni ◽  
Sahar Sodoudi ◽  
Abbas El-Zafarany ◽  
Tarek Abou El Seoud ◽  
Hesham Ashraf ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Statistical Study ◽  
Heat Island ◽  
New Towns ◽  
Urban Heat ◽  
Surface Urban Heat Island

scholarly journals Urban Thermal Environment and Heat Island in Ho Chi Minh City, Vietnam from Remote Sensing Data

2017 ◽  
Author(s):  
Van Tran Thi ◽  
Bao Ha Duong Xuan ◽  
Mai Nguyen Thi Tuyet
Keyword(s):  
Surface Temperature ◽  
Urban Heat Island ◽  
Rural Areas ◽  
Land Surface ◽  
Urban Areas ◽  
Ho Chi Minh City ◽  
Heat Island ◽  
Urban Heat ◽  
Surface Urban Heat Island ◽  
The Impact

In urban area, one of the great problem is the rise of temperature, which leads to form the urban heat island effect. This paper refers to the trend of the urban surface temperature extracted from the Landsat images from which to consider changes in the formation of surface urban heat island for the north of Ho Chi Minh city in period 1995-2015. Research has identified land surface temperature from thermal infrared band, according to the ability of the surface emission based on characteristics of normalized difference vegetation index NDVI. The results showed that temperature fluctuated over the city with a growing trend and the gradual expansion of the area of the high-temperature zone towards the suburbs. Within 20 years, the trend of the formation of surface urban heat island with two typical locations showed a clear difference between the surface temperature of urban areas and rural areas with space expansion of heat island in 4 times in 2015 compared to 1995. An extreme heat island located in the inner city has an area of approximately 18% compared to the total area of the region. Since then, the solution to reduce the impact of urban heat island has been proposed, in order to protect the urban environment and the lives of residents in Ho Chi Minh City becoming better

scholarly journals Spatial structure of the Surface Urban Heat Island in summer based on Landsat 8 imagery in the Górnośląsko – Zagłębiowska Metropolis, Southern Poland 

2021 ◽  
Author(s):  
Aleksandra Renc ◽  
Ewa Łupikasza ◽  
Małgorzata Błaszczyk
Keyword(s):  
Land Use ◽  
Standard Deviation ◽  
Spatial Structure ◽  
Urban Heat Island ◽  
Urban Areas ◽  
Landsat 8 ◽  
Heat Island ◽  
Type Of Land Use ◽  
Urban Heat ◽  
Surface Urban Heat Island

<p>Urbanization results in the increase of impervious surfaces build of materials with high heat capacity and low albedo. Therefore, urban areas heat up more than the surroundings, leading to the development of the urban heat island (UHI). The UHI intensifies the effect of global warming by increased intensity and frequency of heatwaves in the city. In summer, the UHI is considered a phenomenon hazardous for the life and health of city inhabitants. The problem of UHI has not been studied in the Górnośląska-Zagłębiowska Metropolis (GZM), which is the most populated area in Poland. This study aims to determine the spatial structure and intensity of the surface urban heat island (SUHI) in GZM and identify the areas exposed to the most intense heat island. The relationship between the type of land use and the SUHI occurrence was also studied. Four LANDSAT 8 images were converted to the form of land surface temperature (LST). Based on the mean and standard deviation of the LST the extent of the overall SUHI was determined without considering the type of land use. Based on the same method, three classes of SUHI intensity (standard, strong and extreme) were defined and distinguished within anthropogenic areas determined based on the Corine Land Cover 2018 classification of land use. The intensity of SUHI was defined as a difference between urban and non-urban areas. The relationships between various types of land use and LST were also examined. In GZM, SUHI has a structure of 'archipelago' rather than an 'island'. In each image, the highest LSTs were identified for industrial areas represented by Katowice Smeltery. The standard SUHI, defined as average LST +1 standard deviation (only within an anthropogenic area) accounted for 12.7% to 14.4% of the GZM area in individual years, which indicates a small temporal variability of its extent. The extreme SUHI was identified mainly for shopping and logistic centers, industrial facilities, or coal dumps. The intensity of SUHI ranged from 5 to 9 °C depending on the image and method of urban and non-urban areas delineating. The highest average LST was characteristic of the discontinuous urban fabric and industrial or commercial units. Water and forest areas had the lowest average LST. The discontinuous urban fabric and industrial or commercial units constituted more than 70% of the overall SUHI area.</p>

scholarly journals Characterization of the subsurface urban heat island and its sources in the Milan city area, Italy

2021 ◽  
Author(s):  
Alberto Previati ◽  
Giovanni B. Crosta
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Heat Fluxes ◽  
Shallow Aquifer ◽  
Heat Island ◽  
Groundwater Temperature ◽  
City Area ◽  
Groundwater Environment ◽  
Urban Heat ◽  
The Impact

AbstractUrban areas are major contributors to the alteration of the local atmospheric and groundwater environment. The impact of such changes on the groundwater thermal regime is documented worldwide by elevated groundwater temperature in city centers with respect to the surrounding rural areas. This study investigates the subsurface urban heat island (SUHI) in the aquifers beneath the Milan city area in northern Italy, and assesses the natural and anthropogenic controls on groundwater temperatures within the urban area by analyzing groundwater head and temperature records acquired in the 2016–2020 period. This analysis demonstrates the occurrence of a SUHI with up to 3 °C intensity and reveals a correlation between the density of building/subsurface infrastructures and the mean annual groundwater temperature. Vertical heat fluxes to the aquifer are strongly related to the depth of the groundwater and the density of surface structures and infrastructures. The heat accumulation in the subsurface is reflected by a constant groundwater warming trend between +0.1 and + 0.4 °C/year that leads to a gain of 25 MJ/m2 of thermal energy per year in the shallow aquifer inside the SUHI area. Future monitoring of groundwater temperatures, combined with numerical modeling of coupled groundwater flow and heat transport, will be essential to reveal what this trend is controlled by and to make predictions on the lateral and vertical extent of the groundwater SUHI in the study area.

scholarly journals Biomimicry-Based Strategies for Urban Heat Island Mitigation: A Numerical Case Study under Tropical Climate

Biomimetics ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 48
Author(s):  
Kevin Araque ◽  
Paola Palacios ◽  
Dafni Mora ◽  
Miguel Chen Austin
Keyword(s):  
Thermal Comfort ◽  
Urban Heat Island ◽  
Urban Areas ◽  
Outdoor Thermal Comfort ◽  
Base Case ◽  
Heat Island ◽  
Urban Heat ◽  
Historical Heritage ◽  
Pet Index ◽  
Radiant Temperature

In recent years, demographic growth has caused cities to expand their urban areas, increasing the risk of overheating, creating insurmountable microclimatic conditions within the urban area, which is why studies have been carried out on the urban heat island effect (UHI) and its mitigation. Therefore, this research aims to evaluate the cooling potential in the application of strategies based on biomimicry for the microclimate in a historical heritage city of Panama. For this, three case studies (base case, case 1, and case 2) of outdoor thermal comfort were evaluated, in which the Envi-met software was used to emulate and evaluate the thermal performance of these strategies during March (highest temperature month) and October (rainier month). The strategies used were extracted from the contrast of zebra skin, human skin, evaporative cooling, and ant skin. The results showed a reduction of 2.8 °C in the air temperature at 11:00, the radiant temperature decreased by 2.2 °C, and the PET index managed to reduce the thermal comfort indicator among its categories. The importance of thinking based on biomimicry in sustainable strategies is concluded; although significant changes were obtained, high risks of discomfort persist due to the layout and proximity of the building.

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