Impacts, strategies and tools to mitigate UHI

The impacts of climate changes to cities, which are home to over half of the world´s population, are already being felt. In many cases, the intensive speed with which urban centres have been growing means that little attention has been paid to the role played by climatic factors in maintaining the quality of life. Among the negative consequences of rapid city growth is the expansion of the problems posed by urban heat islands, defined as areas in a city that are much warmer than in other sites, especially in comparison with rural areas. This paper analyses the consistency of the UHI related literature in three stages: first it outlines its characteristics and impacts in a wide variety of cities around the world, which poses pressures to public health in many different countries. Then it introduces strategies which may be employed in order to reduce its effects, and finally, it analyses available tools to systematize the initial high-level assessment of the phenomenon for multidisciplinary teams involved in the urban planning process. The analysis of the literature on the characteristics, impacts, strategies and digital tools to assess on the UHI, reveals the wide variety of parameters, methods, tools and strategies analysed and suggested in the different studies, which does not always allow to compare or standardize the diagnosis or solutions

Assessing sustainable urban development trends in a dynamic tourist coastal area using 3D Spatial Indicators

In coastal areas, the tourism sector contributes to the local economy, generating income, employment, investments and tax revenues but the rapid urban expansion creates great pressure on local resources and infrastructures, with negative repercussions on the residents’ quality of life, but also compromising the visitor’s experience. These areas face problems such as the formation of meteorological effects known as heat islands, due to the soil sealing, and increased energy demand in the peak season. To evaluate the impact of urban growth spatial pattern and change, three strategic sustainable challenges—urban form, urban energy, and urban outdoor comfort—were selected. The progress towards sustainability was measured and analyzed in a tourist city in the Algarve region, Portugal, for the period 2007–2018, using geographic information. A set of 2D and 3D indicators was derived for the building and block scales. Then, a change assessment based on cluster analysis was performed, and three different trends of sustainable development were identified and mapped. Results allow detecting the urban growth patterns that lead to more sustainable urban areas. The study revealed that a high sustainable development was observed in 12% of the changed blocks in the study area. All indicators suggest that the growth pattern of the coastal area is in line with the studied sustainability dimensions. However, most of the blocks that changed between 2007 and 2018 (82%) followed a low sustainable development. These blocks had the lowest variation in the built volume and density, and consequently the lowest variations in the roof areas with good solar exposition. The urban development also privileged more detached and less compact buildings. This analysis will support the integration of 2D and 3D information into the planning process, assisting smart cities to comply with the sustainable development goals.info:eu-repo/semantics/publishedVersio

Mapping Past Land Use Changes and Modeling Future Urbanization Patterns in a Mid-Sized American City

On a global scale, humans have been moving from rural to urban areas at an increasingly fast rate in a process called urbanization. It is crucial to understand and predict the impacts of urbanization because city expansion encroaches on farmland and woodland, reducing regional ecosystem services. Therefore, urbanization must be well planned in a forecasting manner. The objective of this study is to map the land use change in Knox County, Tennessee, from 2001-2019 to identify the urbanization trends and understand the dynamic geospatial relationships between the urban and rural areas. The geospatial mapping was done using USGS land use data by classifying land into urban, agricultural, non-agricultural, and waterbody areas. Then, geographic information system (GIS) software was used to analyze the change of each land area in relation to infrastructure change. The results show a decrease in agricultural and non-agricultural land area and an increase in urban use. In addition, normalized difference vegetation index (NDVI) and elevation data, which were collected from the USGS Landsat database, were used to analyze the changes in vegetation, impervious surface area, and surface reflectance during the urban growth. The results were used to create a suitability index model from an environmental view in order to predict the areas in Knox County that are suitable for urban development. Finally, a machine learning model was implemented to compare areas identified as suitable with areas of predicted urbanization. These two models can enable urban planners to develop policies that geospatially optimize urban infrastructure while minimizing environmental footprints

The effects of thermal-spatial behaviours of land covers on urban heat islands in semi-arid climates

In recent decades, unsustainable urban development stemming from uncontrolled changes in land cover and the accumulation of population and activities have given rise to adverse environmental consequences, such as the formation of urban heat islands (UHIs) and changes in urban microclimates. The formation and intensity of UHIs can be influenced not only by the type of land cover, but also by other factors, such as the spatial patterns of thermal clusters (e.g., dimensions, contiguity, and integration). By emphasising the differences between semi-arid and cold-and-humid climates in terms of the thermal−spatial behaviours of various types of land cover in these climates, this paper aims to assess the behavioural patterns of thermal clusters in Tehran, Iran. To this end, the relationship between the land surface temperature (LST) and the types of land cover is first demonstrated using combined multispectral satellite images taken by Operational Land Imager (OLI), Thermal Infrared Sensor (TIRS) of the Landsat8 and MODIS, and Sentinel satellites to determine LST and land cover. The effects of different behavioural patterns of thermal clusters on the formation of daytime urban heat islands are then analysed through spatial cross-correlation analysis. Lastly, the thermal behaviours of each cluster are separately examined to reveal how their spatial patterns, such as contiguity, affect the intensity and formation of UHI, with the assumption that each point in a contiguous surface may exhibit different thermal behaviours, depending on its distance from the edge or centre. The results of this study show that the daytime UHIs do not occur in the central parts of Tehran, and instead they are created in the surrounding layer, which mostly consists of barren cover. This finding contrasts with previous research conducted regarding cities located in cold-and-humid climates. Our research also finds that the more compact the hot and cool clusters are, the more contiguous they become, which leads to an increase in UHIs. The results suggest that for every 100 pix/km2 increase, the cluster temperature increases by approximately 0.7−1 °C. Additionally, placing cool clusters near or in combination with hot clusters interrupts the effect of the hot clusters, leading to a significant temperature reduction. The paper concludes with recommendations for potential sustainable and context-based solutions to UHI problems in semi-arid climates that relate to the determination of the optimal contiguity distance and land use integration patterns for thermal clusters

Study of land use/cover change impacts on thermal microclimate using QGIS in urban agglomeration

Thermal comfort and air quality are major concerns for people living in urban areas. In the last decades, cities are growing quickly and the increased urbanization is leading to the expansion of cities, which changes the properties and composition of the landscape. However, the surface temperatures are increasing, globally, because of anthropogenic climate change. Land use and land cover change have been shown to have a significant effect on climate through various pathways that modulate land surface temperature and rainfall. The objective of this study is to understand how the land use and land cover change affects the thermal microclimate in the city of Biskra (Algeria) using QGIS for the period between 2010 and 2020. The analysis results reveal that the mean temperature of the city has increased by ~4 °C during the past decade with the most accelerated warming (~7 °C) occurring during the recent decade (2010 to 2020). Our study shows also that 32% to 56% of this observed overall warming is associated with land use/cover and the largest changes are related to changing vegetation cover as evidenced by changes to both land use and land covers classes and normalized difference vegetation index (NDVI)

Urban form and air quality in U.S. metropolitan and megapolitan areas

The spatial form, or morphology, of urban areas may significantly affect the anthropogenic production of air pollutants. This dissertation explores the relationships between air quality and urban form at the metropolitan and megapolitan (multi-metropolitan) scale. Urban form was quantified for 86 metropolitan and 19 megapolitan areas using both pre-existing sprawl indices and multiple spatial metrics derived from remotely sensed landcover data. Air quality was assessed by measuring several key air pollutants, including the ambient concentration of ozone (O3), the non-point source emissions of the two O3 precursors nitrogen oxides (NOx) and volatile organic compounds (VOCs), the ambient concentration and non-point source emissions of fine particulate matter (PM2.5) and coarse particulate matter (PM10), and the mobile emissions of carbon dioxide (CO2). The ambient concentrations of air pollutants were averaged over the 5-year period 1998 to 2002. While controlling for industrial emissions, climate, population and geographic area, multiple linear regression was used to evaluate the degree of association between measures of urban form and air quality. The results suggest that urban form has a measurable impact on both the non-point source emission and ambient concentration of air pollution. Urban areas that exhibited more "sprawl-like" urban forms (i.e. lower residential density, less street network connectivity, less contiguous urban development) generally had higher non-point source emissions and/ or ambient concentrations of air pollution. Pre-existing sprawl indices were most significantly associated with ambient concentrations, while two spatial-metrics based measures of urban structure, urban "continuity" and urban "shape complexity," were most significantly associated with non-point source emissions. The relationships between measures of urban form calculated using spatial metrics and air pollution were most significant at the metropolitan scale. The extent of the urban area (i.e. high versus low urban threshold), however, did not significantly affect the associations between urban form, as assessed using spatial metrics, and air pollution. Understanding the relationships between urban form and air quality is an important step in identifying effective urban land use configurations and developing healthier cities

Intra-urban vulnerability to heat-related mortality in New York City, 1997–2006

AbstractThe health impacts of exposure to summertime heat are a significant problem in New York City (NYC) and for many cities and are expected to increase with a warming climate. Most studies on heat-related mortality have examined risk factors at the municipal or regional scale and may have missed the intra-urban variation of vulnerability that might inform prevention strategies. We evaluated whether place-based characteristics (socioeconomic/demographic and health factors, as well as the built and biophysical environment) may be associated with greater risk of heat-related mortality for seniors during heat events in NYC. As a measure of relative vulnerability to heat, we used the natural cause mortality rate ratio among those aged 65 and over (MRR65+), comparing extremely hot days (maximum heat index 100°F+) to all warm season days, across 1997–2006 for NYC’s 59 Community Districts and 42 United Hospital Fund neighborhoods. Significant positive associations were found between the MRR65+ and neighborhood-level characteristics: poverty, poor housing conditions, lower rates of access to air-conditioning, impervious land cover, surface temperatures aggregated to the area-level, and seniors’ hypertension. Percent Black/African American and household poverty were strong negative predictors of seniors’ air conditioning access in multivariate regression analysis

Contrasting changes of urban heat island intensity during hot weather episodes

Cities typically exhibit higher air temperatures than their rural surroundings, a phenomenon known as the urban heat island (UHI) effect. Contrasting results are reported as to whether UHI intensity (UHII) is exacerbated or reduced during hot weather episodes (HWEs). This contrast is investigated for a four-year period from 2015 to 2018, utilising a set of observational data from high-quality meteorological stations, as well as from hundreds of crowdsourced citizen weather stations, located in the urban region of Berlin, Germany. It can be shown that if HWEs, defined here as the ten percent hottest days or nights during May–September, are identified via daytime conditions, or by night-time conditions at inner-city sites, then night-time UHII is exacerbated. However, if HWEs are identified via night-time conditions at rural sites, then night-time UHII is reduced. These differences in UHII change can be linked with prevalent weather conditions, namely radiation, cloud cover, wind speed, precipitation, and humidity. This highlights that, beside land cover changes, future changes in weather conditions due to climate change will control UHIIs, and thus heat-stress hazards in cities.BMBF, 01LP1602C , Verbundprojekt Stadtklima: Dreidimensionale Beobachtung atmosphärischer Prozesse in Städten, Modul B - 3DODFG, 322579844, Hitzewellen in Berlin, Deutschland - StadtklimamodifkationenDFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Analisis Perubahan Temperatur Permukaan Wilayah Surabaya Timur Tahun 2001-2016 Menggunakan Citra LANDSAT

Urban Heat Island (UHI) adalah suatu fenomena dimana suhu udara pada wilayah yang padat bangunan atau kawasan perkotaan lebih tinggi daripada suhu udara di wilayah dengan ruang terbuka yang lebih banyak atau wilayah pedesaan. Salah satu cara untuk mengamati terjadinya fenomena UHI adalah dengan mengamati dinamika suhu permukaan yang terdapat pada suatu wilayah dalam beberapa periode. Penelitian ini menggunakan analisis remote sensing untuk dapat mengkonversikan nilai-nilai digital number pada citra satelit LANDSAT masing-masing periode menjadi nilai land surface temperature/suhu permukaan suatu wilayah serta analisis overlay untuk mengetahui dinamika perubahan suhu permukaan dari beberapa periode waktu yang telah ditentukan. Berddasarkan hasil penelitian dapat diketahui bahwa terdapat peningkatan yang cukup signifikan yaitu selama periode tahun 2001-2016 telah terjadi peningkatan sebesar 6,612°C atau sekitar 25,41% dari nilai suhu permukaan rata-rata pada tahun 2001. Daerah yang memiliki intensitas peningkatan suhu permukaan tertinggi merupakan bagian timur dan selatan wilayah Surabaya Timur

Conceptualizing Spatial Heterogeneity of Urban Composition Impacts on Precipitation Within Tropics

Urban composition has exacerbated precipitation patterns. Rapid urbanization with dynamic composition and anthropogenic activities lead to the change of physical environment, especially land-use and land cover which subsequently magnifies the environmental effects such as flash floods, extreme lightning, and landslides. Due to extreme and elevated temperature trends with exacerbated rainfall patterns, these environmental effects become major issues in tropics. Albeit several studies pointed out that rapid urbanization induced precipitation, studies about the heterogeneity of urban composition on precipitation variables are still limited. Thus, this paper review studies about precipitation pattern in relation to the heterogeneity of urban composition that successfully integrates geographical information system (GIS) and remote sensing techniques to enhance the understanding of interactions between precipitation patterns against heterogeneity of urban composition. This article also addressed the current state of uncertainties and scarcity of data concerning remote sensing techniques. Evidently, with a comprehensive investigation and probing of the precipitation variables in the context of urbanization models fused with remote sensing and GIS, they put forward powerful set tools for geographic cognition and understand how its influence on spatial variation. Hence, this study indicated a great research opportunity to set the course of action in determining the magnitude of spatial heterogeneity of an urban composition towards the pattern of precipitation