scholarly journals Global long-term mapping of surface temperature shows intensified intra-city urban heat island extremes

2021 ◽  
Author(s):  
Lorenzo Mentaschi ◽  
Gregory Duveiller ◽  
Grazia Zulian ◽  
Christina Corbane ◽  
Martino Pesaresi ◽  
...  
Keyword(s):  
Heat Stress ◽  
Surface Temperature ◽  
Urban Heat Island ◽  
Urban Areas ◽  
Human Impacts ◽  
Warm Season ◽  
Mitigation Strategies ◽  
Heat Island ◽  
Urban Heat

Abstract Surface temperatures are generally higher in cities than in rural surroundings. This phenomenon, known as surface urban heat island (SUHI), increases the risk of heat-related human illnesses and mortality. Past global studies analysed this phenomenon aggregated at city scale or over seasonal and annual time periods, while human impacts strongly depend on shorter term heat stress experienced locally. Here we develop a global long-term high-resolution dataset of daytime SUHI as urban-rural surface temperature differences. Our results show that across urban areas worldwide over the period 2003-2020, 3-day SUHI extremes are on average more than twice as high as the warm-season median SUHI, with local exceedances up to 10 K. Over this period, SUHI extremes have increased more rapidly than warm-season medians, and averaged worldwide are now 1.04 K or 31% higher compared to 2003. This can be linked with increasing urbanisation, more frequent heatwaves, and greening of the earth, processes that are all expected to continue in the coming decades. Within many cities there are hotspots where extreme SUHI intensity is 10 to 15 K higher compared to relatively cooler city parts. Given the limited human adaptability to heat stress, our results advocate for mitigation strategies targeted at reducing SUHI extremes in the most vulnerable and exposed city neighbourhoods.

scholarly journals Quantification of Urban Heat Island-Induced Contribution to Advance in Spring Phenology: A Case Study in Hangzhou, China

2021 ◽  
Vol 13 (18) ◽  
pp. 3684
Author(s):  
Yingying Ji ◽  
Jiaxin Jin ◽  
Wenfeng Zhan ◽  
Fengsheng Guo ◽  
Tao Yan
Keyword(s):  
Surface Temperature ◽  
Urban Heat Island ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Urban Areas ◽  
Vegetation Index ◽  
Heat Island ◽  
Spring Phenology ◽  
Urban Heat ◽  
The Difference

Plant phenology is one of the key regulators of ecosystem processes, which are sensitive to environmental change. The acceleration of urbanization in recent years has produced substantial impacts on vegetation phenology over urban areas, such as the local warming induced by the urban heat island effect. However, quantitative contributions of the difference of land surface temperature (LST) between urban and rural (ΔLST) and other factors to the difference of spring phenology (i.e., the start of growing season, SOS) between urban and rural (ΔSOS) were rarely reported. Therefore, the objective of this study is to explore impacts of urbanization on SOS and distinguish corresponding contributions. Using Hangzhou, a typical subtropical metropolis, as the study area, vegetation index-based phenology data (MCD12Q2 and MYD13Q1 EVI) and land surface temperature data (MYD11A2 LST) from 2006–2018 were adopted to analyze the urban–rural gradient in phenology characteristics through buffers. Furthermore, we exploratively quantified the contributions of the ΔLST to the ΔSOS based on a temperature contribution separation model. We found that there was a negative coupling between SOS and LST in over 90% of the vegetated areas in Hangzhou. At the sample-point scale, SOS was weakly, but significantly, negatively correlated with LST at the daytime (R2 = 0.2 and p < 0.01 in rural; R2 = 0.14 and p < 0.05 in urban) rather than that at nighttime. Besides, the ΔSOS dominated by the ΔLST contributed more than 70% of the total ΔSOS. We hope this study could help to deepen the understanding of responses of urban ecosystem to intensive human activities.

Understanding and Analysing the Urban Heat Island (UHI) Effect in Micro-Scale

2019 ◽  
Vol 10 (2) ◽  
pp. 14-28 ◽  
Author(s):  
Ali Soltani ◽  
Ehsan Sharifi
Keyword(s):  
Heat Stress ◽  
Surface Temperature ◽  
Urban Heat Island ◽  
Metropolitan Area ◽  
Urban Environments ◽  
Heat Island ◽  
Late Afternoon ◽  
Micro Scale ◽  
Daily Cycles ◽  
Urban Heat

The shortage of vegetation cover alongside urban structures and land hardscape in cities causes an artificial temperature increase in urban environments known as the urban heat island (UHI) effect. The artificial heat stress in cities has a particular threat for usability and health-safety of outdoor living in public space. Australia may face a likely 3.8°C increase in surface temperature by 2090. Such an increase in temperature will have a severe impact on regional and local climate systems, natural ecosystems, and human life in cities. This paper aims to determine the patterns of the UHI effect in micro-scale of Adelaide metropolitan area, South Australia. The urban near-surface temperature profile of Adelaide was measured along a linear east-west cross-section of the metropolitan area via mobile traverse method between 26 July 2013 and 15 August 2013. Results indicate that the while the maximum UHI effect occurs at midnight in the central business district (CBD) area in Adelaide, the afternoon urban warmth has more temperature variations (point-to-point variation), especially during the late afternoon when local air temperature is normally in its peak. Thus, critical measurement of heat-health consequences of the UHI effect need to be focused on the afternoon heat stress conditions in UHIs rather than the commonly known night time phenomenon. This mobile traverse urban heat study of Adelaide supports the hypothesis that the UHI effect varies in the built environment during daily cycles and within short distances. Classical UHI measurements are commonly performed during the night – when the urban-rural temperature differences are at their maximum. Thus, they fall short in addressing the issue of excess heat stress on human participants. However, having thermally comfortable urban microclimates is a fundamental characteristic of healthy and vibrant public spaces. Therefore, urban planning professionals and decision makers are required to consider diurnal heat stress alongside nocturnal urban heat islands in planning healthy cities. The results of this article show that the diurnal heat stress varies in the built environment during daily cycles and within short distances. This study confirms that the maximum urban heat stress occurs during late afternoon when both overall temperature and daily urban warmth are at their peak. Literature indicates that diurnal heat stress peaks in hard-landscapes urban settings while it may decrease in urban parklands and near water bodies. Therefore, urban greenery and surface water can assist achieving more liveable and healthy urban environments (generalisation requires further research). A better understanding of daily urban warmth variations in cities assists urban policy making and public life management in the context of climate change.

scholarly journals Features of Urban Heat Island in Mountainous Chongqing from a Dense Surface Monitoring Network

Atmosphere ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 67 ◽  
Author(s):  
Ping Jiang ◽  
Xiaoran Liu ◽  
Haonan Zhu ◽  
Yonghua Li
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Surface Wind ◽  
Warm Season ◽  
Monitoring Network ◽  
Anthropogenic Heat ◽  
Heat Island ◽  
Near Surface ◽  
Urban Heat ◽  
Surface Monitoring

The spatial and temporal features of urban heat island (UHI) intensity in complex urban terrain are barely investigated. This study examines the UHI intensity variations in mountainous Chongqing using a dense surface monitoring network. The results show that the UHI intensity is closely related to underlying surfaces, and the strongest UHI intensity is confined around the central urban areas. The UHI intensity is most prominent at night and in warm season, and the magnitude could reach ~4.5 °C on summer night. Our quantitative analysis shows a profound contribution of urbanization level to UHI intensity both at night and in summer, with regression coefficient b = 4.31 and 6.65, respectively. At night, the urban extra heat such as reflections of longwave radiation by buildings and release of daytime-stored heat from artificial materials, is added into the boundary layer, which compensates part of urban heat loss and thus leads to stronger UHI intensity. In summer, the urban areas are frequently controlled by oppressively hot weather. Due to increased usage of air conditioning, more anthropogenic heat is released. As a result, the urban temperatures are higher at night. The near-surface wind speed can serve as an indicator predicting UHI intensity variations only in the diurnal cycle. The rural cooling rate during early evening transition, however, is an appropriate factor to estimate the magnitude of UHI intensity both at night and in summer.

Synergistic Interactions between Urban Heat Islands and Heat Waves: The Impact in Cities Is Larger than the Sum of Its Parts

2013 ◽  
Vol 52 (9) ◽  
pp. 2051-2064 ◽  
Author(s):  
Dan Li ◽  
Elie Bou-Zeid
Keyword(s):  
Urban Heat Island ◽  
Rural Areas ◽  
Urban Areas ◽  
Heat Waves ◽  
Mitigation Strategies ◽  
Urban Heat Islands ◽  
Heat Island ◽  
Heat Islands ◽  
Urban Heat ◽  
The Impact

AbstractCities are well known to be hotter than the rural areas that surround them; this phenomenon is called the urban heat island. Heat waves are excessively hot periods during which the air temperatures of both urban and rural areas increase significantly. However, whether urban and rural temperatures respond in the same way to heat waves remains a critical unanswered question. In this study, a combination of observational and modeling analyses indicates synergies between urban heat islands and heat waves. That is, not only do heat waves increase the ambient temperatures, but they also intensify the difference between urban and rural temperatures. As a result, the added heat stress in cities will be even higher than the sum of the background urban heat island effect and the heat wave effect. Results presented here also attribute this added impact of heat waves on urban areas to the lack of surface moisture in urban areas and the low wind speed associated with heat waves. Given that heat waves are projected to become more frequent and that urban populations are substantially increasing, these findings underline the serious heat-related health risks facing urban residents in the twenty-first century. Adaptation and mitigation strategies will require joint efforts to reinvent the city, allowing for more green spaces and lesser disruption of the natural water cycle.

scholarly journals Evaluating the Effectiveness of Mitigation Options on Heat Stress for Sydney, Australia

2018 ◽  
Vol 57 (2) ◽  
pp. 209-220 ◽  
Author(s):  
Shaoxiu Ma ◽  
Andy Pitman ◽  
Jiachuan Yang ◽  
Claire Carouge ◽  
Jason P. Evans ◽  
...  
Keyword(s):  
Heat Stress ◽  
Urban Heat Island ◽  
Air Temperature ◽  
Ambient Air ◽  
Mitigation Strategies ◽  
Heat Island ◽  
Human Thermal Comfort ◽  
Ambient Air Temperature ◽  
Populations At Risk ◽  
Urban Heat

AbstractGlobal warming, in combination with the urban heat island effect, is increasing the temperature in cities. These changes increase the risk of heat stress for millions of city dwellers. Given the large populations at risk, a variety of mitigation strategies have been proposed to cool cities—including strategies that aim to reduce the ambient air temperature. This paper uses common heat stress metrics to evaluate the performance of several urban heat island mitigation strategies. The authors found that cooling via reducing net radiation or increasing irrigated vegetation in parks or on green roofs did reduce ambient air temperature. However, a lower air temperature did not necessarily lead to less heat stress because both temperature and humidity are important factors in determining human thermal comfort. Specifically, cooling the surface via evaporation through the use of irrigation increased humidity—consequently, the net impact on human comfort of any cooling was negligible. This result suggests that urban cooling strategies must aim to reduce ambient air temperatures without increasing humidity, for example via the deployment of solar panels over roofs or via cool roofs utilizing high albedos, in order to combat human heat stress in the urban environment.

scholarly journals Satellite Based Analysis of Surface Urban Heat Island Intensity

2016 ◽  
Vol 9 (1-2) ◽  
pp. 23-30 ◽  
Author(s):  
Orsolya Gémes ◽  
Zalán Tobak ◽  
Boudewijn van Leeuwen
Keyword(s):  
Surface Temperature ◽  
Urban Heat Island ◽  
Urban Climate ◽  
Seasonal Development ◽  
Heat Island ◽  
Early Afternoon ◽  
Local Climate Zones ◽  
Urban Heat ◽  
Surface Urban Heat Island

Abstract The most obvious characteristics of urban climate are higher air and surface temperatures compared to rural areas and large spatial variation of meteorological parameters within the city. This research examines the long term and seasonal development of urban surface temperature using satellite data during a period of 30 years and within a year. The medium resolution Landsat data were (pre)processed using open source tools. Besides the analysis of the long term and seasonal changes in land surface temperature within a city, also its relationship with changes in the vegetation cover was investigated. Different urban districts and local climate zones showed varying strength of correlation. The temperature difference between urban surfaces and surroundings is defined as surface urban heat island (SUHI). Its development shows remarkable seasonal and spatial anomalies. The satellite images can be applied to visualize and analyze the SUHI, although they were not collected at midday and early afternoon, when the phenomenon is normally at its maximum. The applied methodology is based on free data and software and requires minimal user interaction. Using the results new urban developments (new built up and green areas) can be planned, that help mitigate the negative effects of urban climate.

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 STUDI PULAU PANAS PERKOTAAN DAN KAITANNYA DENGAN PERUBAHAN PARAMETER IKLIM SUHU DAN CURAH HUJAN MENGGUNAKAN CITRA SATELIT LANDSAT TM STUDI KASUS DKI JAKARTA DAN SEKITARNYA

2012 ◽  
Vol 13 (1) ◽  
pp. 19 ◽  
Author(s):  
Halda Aditya Belgaman ◽  
Sri Lestari ◽  
Hilda Lestiana
Keyword(s):  
Surface Temperature ◽  
Urban Heat Island ◽  
Air Temperature ◽  
Urban Areas ◽  
Satellite Image ◽  
Heat Island ◽  
Surrounding Area ◽  
Urban Heat ◽  
Climate Parameter ◽  
Landsat Satellite

Pulau panas adalah suatu fenomena dimana suhu udara di suatu daerah lebih tinggi daripada suhu udara terbuka di sekitarnya. Daerah urban (perkotaan) sering mempunyai suhu lebih tinggi 1-6 derajat Celsius dibandingkan daerah sekitarnya (daerah pinggiran/ rural). Fenomena inilah yang dikenal sebagai ”Pulau Panas perkotaan” atau ”Urban Heat Island” (UHI). Penelitian ini bertujuan untuk mengetahui pengaruh fenomena pulau panas perkotaan terhadap parameter iklim terutama suhu dan curah hujan di daerahJakarta dan sekitarnya. Data yang digunakan pada tugas akhir ini adalah data curah hujan dan temperatur udara harian pada 5 stasiun pengamatan iklim, periode Januari 1991 – Desember 2001 sebagai data permukaan. Citra satelit Landsat 7 ETM+ path / row 122/064 akuisisi tanggal 15/07/2001 band 5,4,2 digunakan untuk menganalisis tutupan lahan dan band 6 digunakan untuk distribusi temperatur permukaan. Hasil menunjukkan nilai temperatur permukaan Kota Jakarta dan sekitarnya berada antara 15.07˚C hingga 33.28˚C. Lokasi pulau panas perkotaan terdapat di daerah Jakarta pusat dan Jakarta utara, dengan perbedaan temperatur sebesar 3˚C dibandingkan dengan daerah sekitarnya.Tutupan lahan yang terdapat di lokasi tersebut merupakan lahan terbangun yang terdiri dari bangunan perumahan, perkantoran, dan jalan raya. Perhitungan nilai korelasi Spearman antara data temperatur udara dari lima stasiun pengamatan dengan nilai piksel temperatur permukaan memperlihatkan adanya korelasi positif antara dua variabel tersebut yang ditunjukkan oleh indeks korelasi sebesar 0.6.Dengan persamaan regresi diperoleh citra temperatur permukaan di seluruh daerah pengamatan yang hasilnya menggambarkan bahwa lokasi pulau panas perkotaan sangat berpengaruh terhadap distribusi temperatur udara di atasnya.Heat island was a phenomenon where the temperature of air in one region higher than the temperature of the open air around it. Urban areas often had the temperature higher 1-6 Celsius when compared the area of surrounding area (the area of outskirts/rural). This phenomenon that was known as ”Pulau Panas Perkotaan” or ”Urban Heat Island” (UHI). This Research aimed to knowing influence of the heat islands of urban areas to climate parameter especially the temperature and the rainfall in the Jakarta and surrounding area. Data used in this research was rainfall data and daily air temperaturefrom 5 climate observation stations, within time period from January 1991 to December 2001 as the surface data. The Landsat satellite image 7 ETM+ path/row 122/064 acquisition date 15/07/2001, band 5, 4, 2 was used to analyze the cover of land and the band 6 was used for the distribution of surface temperature was based on the pixels value.Results showed the value of surface temperature in Jakarta and surrounding area was between 15.07˚C through to 33.28˚C. Location of heat island were in the centre Jakarta and north Jakarta, with the difference of the temperature as big as 3˚C with thesurrounding area. The land cover in this location were the housing building, the office complex, and the highway. Calculation of Spearman correlation value between the air temperature and surface temperature showed the existence of the positive correlation between two variables that it was demonstrated by the correlation index 0.6. From the regression equation we get the interpolated air temperature in Jakarta area.

scholarly journals Evaluation of Urban Heat Island (UHI) Using Satellite Images in Densely Populated Cities of South Asia

Earth ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 86-110
Author(s):  
Manisha Maharjan ◽  
Anil Aryal ◽  
Bijay Man Shakya ◽  
Rocky Talchabhadel ◽  
Bhesh Raj Thapa ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Urban Heat Island ◽  
South Asia ◽  
Land Surface ◽  
Urban Areas ◽  
Well Being ◽  
Heat Island ◽  
Rapid Urbanization ◽  
Urban Heat ◽  
The Impact

Rapid Urbanization, and other anthropogenic activities, have amplified the change in land-use transition from green space to heat emission in built-up areas globally. As a result, there has been an increase in the land surface temperature (LST) causing the Urban Heat Island (UHI) effect, particularly in large cities. The UHI effect poses a serious risk to human health and well-being, magnified in large developing cities with limited resources to cope with such issues. This study focuses on understanding the UHI effect in Kathmandu Valley (KV), Delhi, and Dhaka, three growing cities in South Asia. The UHI effect was evaluated by analyzing the UHI intensity of the city with respect to the surroundings. We found that the central urban area, of all three cities, experienced more heat zones compared to the peri-urban areas. The estimated average surface temperature ranged from 21.1 ∘C in March 2014 to 32.0 ∘C in June 2015 in KV, while Delhi and Dhaka experienced surface temperature variation from 29.7 ∘C in June 2017 to 40.2 ∘C in June 2019 and 23.6 ∘C in March 2017 to 33.2 ∘C in March 2014, respectively. Based on magnitude and variation of LST, highly built-up central KV showed heat island characteristics. In both Delhi and Dhaka, the western regions showed the UHI effect. Overall, this study finds that the UHI zones are more concentrated near the urban business centers with high population density. The results suggest that most areas in these cities have a rising LST trend and are on the verge of being UHI regions. Therefore, it is essential that further detailed assessment is conducted to understand and abate the impact of the temperature variations.

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