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 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 Development of a Zero-Dimensional Mesoscale Thermal Model for Urban Climate

2009 ◽  
Vol 48 (3) ◽  
pp. 657-668 ◽  
Author(s):  
Humberto R. Silva ◽  
Rahul Bhardwaj ◽  
Patrick E. Phelan ◽  
Jay S. Golden ◽  
Susanne Grossman-Clarke
Keyword(s):  
Energy Balance ◽  
Urban Heat Island ◽  
Mitigation Strategies ◽  
Anthropogenic Heat ◽  
Mitigation Measures ◽  
Balance Model ◽  
Time Range ◽  
Heat Island ◽  
Time Step ◽  
Urban Heat

Abstract A simple energy balance model is created for use in developing mitigation strategies for the urban heat island effect. The model is initially applied to the city of Phoenix, Arizona. There are six primary contributions to the overall energy balance: incident solar radiation, anthropogenic heat input, conduction heat loss, outgoing evapotranspiration, outgoing convection, and outgoing emitted radiation. Meteorological data are input to the model, which then computes an urban characteristic temperature at a calculated time step for a specified time range. The model temperature is shown to have the same periodic behavior as the experimentally measured air temperatures. Predicted temperature changes, caused by increasing the average urban albedo, agree within 0.1°C with comparable maximum surface temperature predictions from the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5). The present model, while maintaining valid energy-balance physics, allows users to quickly and easily predict the relative effects of urban heat island mitigation measures. Representative mitigation strategies, namely changes in average albedo and long-wavelength emissivity are presented here. Increasing the albedo leads to the greater reduction in daytime maximum temperatures; increasing the emissivity leads to a greater reduction in nighttime minimum temperatures.

The impact of COVID-19 lockdowns on surface urban heat island changes and air-quality improvements across 21 major cities in the Middle East

2021 ◽  
pp. 117802
Author(s):  
Ahmed M. El Kenawy ◽  
Juan I. Lopez-Moreno ◽  
Matthew F. McCabe ◽  
Fernando Domínguez-Castro ◽  
Dhais Peña-Angulo ◽  
...  
Keyword(s):  
Air Quality ◽  
Middle East ◽  
Urban Heat Island ◽  
Heat Island ◽  
Quality Improvements ◽  
Urban Heat ◽  
Surface Urban Heat Island ◽  
The Impact

scholarly journals Disproportionate exposure to urban heat island intensity across major US cities

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Angel Hsu ◽  
Glenn Sheriff ◽  
Tirthankar Chakraborty ◽  
Diego Manya
Keyword(s):  
Urban Heat Island ◽  
Census Tract ◽  
Demographic Data ◽  
Heat Exposure ◽  
Poverty Line ◽  
Built Environments ◽  
Heat Island ◽  
Urban Heat ◽  
Surface Urban Heat Island ◽  
Us Cities

AbstractUrban heat stress poses a major risk to public health. Case studies of individual cities suggest that heat exposure, like other environmental stressors, may be unequally distributed across income groups. There is little evidence, however, as to whether such disparities are pervasive. We combine surface urban heat island (SUHI) data, a proxy for isolating the urban contribution to additional heat exposure in built environments, with census tract-level demographic data to answer these questions for summer days, when heat exposure is likely to be at a maximum. We find that the average person of color lives in a census tract with higher SUHI intensity than non-Hispanic whites in all but 6 of the 175 largest urbanized areas in the continental United States. A similar pattern emerges for people living in households below the poverty line relative to those at more than two times the poverty line.

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