scholarly journals Changes in Urbanization and Urban Heat Island Effect in Dhaka City

2021 ◽  
Author(s):  
A S M Shanawaz Uddin ◽  
Najeebullah Khan ◽  
Abu Reza Md. Towfiqul I ◽  
Mohammad Kamruzzaman ◽  
Shamsuddin Shahid
Keyword(s):  
Urban Heat Island ◽  
Land Surface ◽  
Urban Areas ◽  
Clustering Algorithm ◽  
Planning Process ◽  
Urban Expansion ◽  
Heat Island ◽  
Dhaka City ◽  
Urban Heat ◽  
The City

Abstract Urbanization changes the local environment, resulting in urban heat island (UHI) effect and deteriorating human life quality. Knowledge of urban environments and temperature changes is important to outline the urban planning process for mitigation of UHI effect. The study aimed to assess the changes in urban areas and UHI effects in Dhaka city, Bangladesh from 2001to 2017, using Moderate Resolution Imaging Spectroradiometer (MODIS) daily day- and nighttime land surface temperature (LST) data from 2001to 2017. The expansion of the city was calculated using the city clustering algorithm (CCA). The temperature of the identified urbanized area was analyzed and compared with the adjacent regions. The changes in urban temperature were estimated using non-parametric statistical methods. The results showed that the Dhaka city area has grown by 19.12% and its inhabitants by 76.65% during 2001–2017. Urban expansion and dense settlements caused an increase in average temperature in some areas of Dhaka city nearly 3°C compared to that at its boundary. The day and night temperatures at Dhaka city's warmest location were nearly 7 and 5ºC, respectively, more than the coolest point outside the city. The city's annual average day- and nighttime temperature was increasing at a rate of 0.03° and 0.023°C/year over the period 2001–2017. The rising temperature would increase the UHI effect in the future, which combined with high humidity, may cause a significant increase in public health risk in the city if mitigation practices are not followed.

Identifikasi Pertumbuhan Urban Heat Island secara Spasial-Temporal di Kota Palangka Raya Menggunakan Penginderaan Jauh dan Sistem Informasi Geografis

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Afrilyani Kontryana ◽  
Abdul Wahid Hasyim ◽  
Amin Setyo Leksono
Keyword(s):  
Surface Temperature ◽  
Urban Heat Island ◽  
Urban Area ◽  
Land Surface ◽  
Urban Areas ◽  
Landsat 8 ◽  
Heat Island ◽  
Urban Village ◽  
Urban Heat ◽  
The City

Developments in the city of Palangka Raya y giving different temperature between urban and sub-urban. Phenomenon that  cities have warmer temperatures than sub-urban and rural areas called Urban Heat Island (UHI). This study aims to find out about the development of the UHI phenomenon in the city of Palangka Raya  from 2000  to 2018 using remote sensing and geographical system. Based on the analysis of the TIR band landsat 7,  in Kota Palangka Raya since 2000 has been UHI phenomenon, where high Land Surface Temperature (LST) was found dominantly in urban areas  compared to sub-urban areas . In 2018, as Palangka Raya city  had developed, based on the result of TIR band Landsat 8, the distribution of high LST not only found in the urban area, but in the sub-urban zone, especially at  Menteng Urban Village and Panarung Urban Village. The development of UHI in Palangka Raya city over eighteen years (2000-2018) show  in the sub-urban area  experienced changes of UHIindex’s area more dynamic than the urban area. Urban development causing to conversion of  vegetated land into impervious land,  which greatly affects the energy balance. The increase in impervious areas causes more solar radiation  that reaches the surfaces of the earth   more absorbing and it is converted into sensible thermal  energy which increases the surface temperature.

scholarly journals Persebaran Fenomena Suhu Tinggi melalui Kerapatan Vegetasi dan Pertumbuhan Bangunan serta Distribusi Suhu Permukaan

2020 ◽  
Vol 17 (2) ◽  
pp. 56-62
Author(s):  
Eggy Arya Giofandi
Keyword(s):  
Urban Heat Island ◽  
Land Surface ◽  
Urban Areas ◽  
Green Space ◽  
Initial Temperature ◽  
Landsat 8 ◽  
Heat Island ◽  
Surrounding Area ◽  
Urban Heat ◽  
The City

Urban heat island is one of the events where the temperature in the metropolitan area is warmer than the surrounding area. Indonesia is located in a tropical climate making several cities potentially increase in temperature during the dry season. As a representative, the City of Pekanbaru is one of the cities with infrastructure growth that is fast including on the island of Sumatra. Population growth and high enthusiastic of residents to find work in the city made land on the edge of the city built up. This makes the green space less and less with the uneven distribution of green space in the city of Pekanbaru. The number of buildings that exist makes the temperature rise in urban areas with an initial temperature of 29oC to 36oC. temperature increases occurred throughout the year with the hottest peaks of temperatures reaching 37oC on April 15, 2013. Whereas in 2009 there was a decrease in temperature with levels ranging from 27oC. This makes the city of Pekanbaru one of the hottest cities in Indonesia. This study uses Landsat 5 imagery for 2000 and 2009, and Landsat 8 for 2018 with the Land Surface Temperature (LST) method and Normalized Difference Built-up Index (NDBI) which are useful to explain the urban heat island distribution (UHI) in Pekanbaru City

scholarly journals Ecological impact evaluation of urban heat island in Dhaka city; a spatio-temporal approach

2021 ◽  
Author(s):  
Kazi Jihadur Rashid ◽  
Sumaia Islam ◽  
Mohammad Atiqur Rahman
Keyword(s):  
Land Cover ◽  
Urban Heat Island ◽  
Land Surface ◽  
Ecological Impact ◽  
Urban Life ◽  
Heat Island ◽  
Dhaka City ◽  
Ecological Conditions ◽  
Urban Heat ◽  
The Impact

Abstract Urban heat island (UHI) is one of the major causes for deteriorating ecology of the rapidly expanding Dhaka city in the changing climatic conditions. Although researchers have identified, characterized and modeled UHI in the study area, the ecological evaluation of UHI effect has not yet been focused. This study uses land surface normalization techniques such as urban thermal field variance (UTFVI) to quantify the impact of UHI and also identifies vulnerable UHI areas compared to land cover types. Landsat imageries from 1990 to 2020 were used at decadal intervals. Results of the study primarily show that intensified UHI areas have increased spatially from 33.1–40.9% in response to urban growth throughout the period of 1990 to 2020. Extreme surface temperature values above 31°C have also been shown in open soils in under-construction sites for future developmental purposes. UTFVI is categorized into six categories representing UHI intensity in relation to ecological conditions. Finally, comparative analysis between land use/land cover (LULC) with UTFVI shows that the ecological conditions deteriorate as the intensity of UHI increases in the area. The developed areas facing ecological threat have increased from 9.3–19.8% throughout the period. Effective mitigating measures such as increasing green surfaces and planned urbanization practices are crucial in this regard. This study would help policymakers to concentrate on controlling thermal exposure and on preserving sustainable urban life.

scholarly journals Assessment of Changes in Land Use/Land Cover and Land Surface Temperatures and Their Impact on Surface Urban Heat Island Phenomena in the Kathmandu Valley (1988–2018)

2020 ◽  
Vol 9 (12) ◽  
pp. 726
Author(s):  
Md. Omar Sarif ◽  
Bhagawat Rimal ◽  
Nigel E. Stork
Keyword(s):  
Urban Heat Island ◽  
Land Surface ◽  
Agricultural Land ◽  
Kathmandu Valley ◽  
Heat Island ◽  
City Center ◽  
Urban Heat ◽  
Surface Urban Heat Island ◽  
The City ◽  
Normal Difference

More than half of the world’s populations now live in rapidly expanding urban and its surrounding areas. The consequences for Land Use/Land Cover (LULC) dynamics and Surface Urban Heat Island (SUHI) phenomena are poorly understood for many new cities. We explore this issue and their inter-relationship in the Kathmandu Valley, an area of roughly 694 km2, at decadal intervals using April (summer) Landsat images of 1988, 1998, 2008, and 2018. LULC assessment was made using the Support Vector Machine algorithm. In the Kathmandu Valley, most land is either natural vegetation or agricultural land but in the study period there was a rapid expansion of impervious surfaces in urban areas. Impervious surfaces (IL) grew by 113.44 km2 (16.34% of total area), natural vegetation (VL) by 6.07 km2 (0.87% of total area), resulting in the loss of 118.29 km2 area from agricultural land (17.03% of total area) during 1988–2018. At the same time, the average land surface temperature (LST) increased by nearly 5–7 °C in the city and nearly 3–5 °C at the city boundary. For different LULC classes, the highest mean LST increase during 1988–2018 was 7.11 °C for IL with the lowest being 3.18 °C for VL although there were some fluctuations during this time period. While open land only occupies a small proportion of the landscape, it usually had higher mean LST than all other LULC classes. There was a negative relationship both between LST and Normal Difference Vegetation Index (NDVI) and LST and Normal Difference Moisture Index (NDMI), respectively, and a positive relationship between LST and Normal Difference Built-up Index (NDBI). The result of an urban–rural gradient analysis showed there was sharp decrease of mean LST from the city center outwards to about 15 kms because the NDVI also sharply increased, especially in 2008 and 2018, which clearly shows a surface urban heat island effect. Further from the city center, around 20–25 kms, mean LST increased due to increased agriculture activity. The population of Kathmandu Valley was 2.88 million in 2016 and if the growth trend continues then it is predicted to reach 3.85 million by 2035. Consequently, to avoid the critical effects of increasing SUHI in Kathmandu it is essential to improve urban planning including the implementation of green city technologies.

scholarly journals The Effects of Green Roofs on Outdoor Thermal Comfort, Urban Heat Island Mitigation and Energy Savings

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 123 ◽  
Author(s):  
Guglielmina Mutani ◽  
Valeria Todeschi
Keyword(s):  
Surface Temperature ◽  
Thermal Comfort ◽  
Urban Heat Island ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Green Roofs ◽  
Heat Island ◽  
Urban Context ◽  
Urban Heat ◽  
The City

There is growing attention to the use of greenery in urban areas, in various forms and functions, as an instrument to reduce the impact of human activities on the urban environment. The aim of this study has been to investigate the use of green roofs as a strategy to reduce the urban heat island effect and to improve the thermal comfort of indoor and outdoor environments. The effects of the built-up environment, the presence of vegetation and green roofs, and the urban morphology of the city of Turin (Italy) have been assessed considering the land surface temperature distribution. This analysis has considered all the information recorded by the local weather stations and satellite images, and compares it with the geometrical and typological characteristics of the city in order to find correlations that confirm that greenery and vegetation improve the livability of an urban context. The results demonstrate that the land-surface temperature, and therefore the air temperature, tend to decrease as the green areas increase. This trend depends on the type of urban context. Based on the results of a green-roofs investigation of Turin, the existing and potential green roofs are respectively almost 300 (257,380 m2) and 15,450 (6,787,929 m2). Based on potential assessment, a strategy of priority was established according to the characteristics of building, to the presence of empty spaces, and to the identification of critical areas, in which the thermal comfort conditions are poor with low vegetation. This approach can be useful to help stakeholders, urban planners, and policy makers to effectively mitigate the urban heat island (UHI), improve the livability of the city, reduce greenhouse gas (GHG) emissions and gain thermal comfort conditions, and to identify policies and incentives to promote green roofs.

scholarly journals Climate change over UK cities: the urban influence on extreme temperatures in the UK climate projections

2021 ◽  
Author(s):  
William J. Keat ◽  
Elizabeth J. Kendon ◽  
Sylvia I. Bohnenstengel
Keyword(s):  
Urban Heat Island ◽  
Rural Areas ◽  
Land Surface ◽  
Urban Areas ◽  
Climate Model ◽  
Climate Projections ◽  
Heat Island ◽  
Night Time ◽  
Urban Heat ◽  
The Uk

AbstractIncreasing summer temperatures in a warming climate will increase the exposure of the UK population to heat-stress and associated heat-related mortality. Urban inhabitants are particularly at risk, as urban areas are often significantly warmer than rural areas as a result of the urban heat island phenomenon. The latest UK Climate Projections include an ensemble of convection-permitting model (CPM) simulations which provide credible climate information at the city-scale, the first of their kind for national climate scenarios. Using a newly developed urban signal extraction technique, we quantify the urban influence on present-day (1981–2000) and future (2061–2080) temperature extremes in the CPM compared to the coarser resolution regional climate model (RCM) simulations over UK cities. We find that the urban influence in these models is markedly different, with the magnitude of night-time urban heat islands overestimated in the RCM, significantly for the warmest nights (up to $$4~^{\circ }$$ 4 ∘ C), while the CPM agrees much better with observations. This improvement is driven by the improved land-surface representation and more sophisticated urban scheme MORUSES employed by the CPM, which distinguishes street canyons and roofs. In future, there is a strong amplification of the urban influence in the RCM, whilst there is little change in the CPM. We find that future changes in soil moisture play an important role in the magnitude of the urban influence, highlighting the importance of the accurate representation of land-surface and hydrological processes for urban heat island studies. The results indicate that the CPM provides more reliable urban temperature projections, due at least in part to the improved urban scheme.

scholarly journals Data and techniques for studying the urban heat island effect in Johannesburg

2015 ◽  
Vol XL-7/W3 ◽  
pp. 203-206 ◽  
Author(s):  
C. H. Hardy ◽  
A. L. Nel
Keyword(s):  
Remote Sensing ◽  
Urban Heat Island ◽  
Urban Areas ◽  
Remote Sensing Data ◽  
Urban Heat Island Effect ◽  
Heat Island ◽  
Sensing Data ◽  
Island Effect ◽  
Urban Heat ◽  
The City

The city of Johannesburg contains over 10 million trees and is often referred to as an urban forest. The intra-urban spatial variability of the levels of vegetation across Johannesburg’s residential regions has an influence on the urban heat island effect within the city. Residential areas with high levels of vegetation benefit from cooling due to evapo-transpirative processes and thus exhibit weaker heat island effects; while their impoverished counterparts are not so fortunate. The urban heat island effect describes a phenomenon where some urban areas exhibit temperatures that are warmer than that of surrounding areas. The factors influencing the urban heat island effect include the high density of people and buildings and low levels of vegetative cover within populated urban areas. This paper describes the remote sensing data sets and the processing techniques employed to study the heat island effect within Johannesburg. In particular we consider the use of multi-sensorial multi-temporal remote sensing data towards a predictive model, based on the analysis of influencing factors.

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.

Analysis of temperature trends and urban heat island in Madrid

2020 ◽  
Author(s):  
Gregorio Maqueda ◽  
Carlos Yagüe ◽  
Carlos Román-Cascón ◽  
Encarna Serrano ◽  
Jon Ander Arrillaga
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Surface Energy Budget ◽  
City Centre ◽  
Synoptic Situation ◽  
Heat Island ◽  
Temperature Trends ◽  
Measuring Period ◽  
Urban Heat ◽  
The City

&lt;p&gt;The temperature in the cities is affected by both global climate change and local changes due to human activities and the different land use compared to rural surroundings. These local changes, which modify the surface energy budget in urban areas, include the replacement of the natural surfaces by buildings and pavements and the heat of anthropogenic origin (heating, air conditioning, traffic). Madrid city (Spain) has a current population of near 3.3 million people and a larger metropolitan area reaching around 6.5 million people. Hence, it is affected by the phenomenon called urban heat island (UHI), which indicates that a higher temperature is found in the city compared with the surrounding rural areas. UHI is defined as the temperature difference between the urban observatory and the rural one and especially affects the minimum temperatures since urban areas cool down to a lesser extent than the neighbouring rural sites. Moreover, the intensity of the UHI is modulated by the meteorological conditions (wind, cloudiness, surface pressure, precipitation), highly associated with different synoptic situations. In this work, we use the Madrid-Retiro meteorological station as the urban one, which has regular and homogeneous data from the beginning of XX century; and the station at Barajas airport (12 km from the city centre) as well as other stations out of Madrid city (but within a range of 20 km from the city centre) as the rural stations. They all have a common measuring period from 1961 until present. The main objectives of the work are: 1) to identify temperature trends in the meteorological stations (both urban and rural); 2) to evaluate the intensity of the UHI for the different rural stations; 3) to apply a systematic and objective algorithm to classify each day in different categories (related to synoptic situation) that produce a different degree of UHI intensity; and, 4) to evaluate possible trends in the UHI intensity.&lt;/p&gt;

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