Impacts of Land Cover Change on Urban Heat Island (UHI) in Denver from 1985 to 2020

Rapid urbanization due to land use and land cover change has become one of the major problems in the fastest-growing cities during the past few decades. Land surface temperature has changed dramatically due to urban expansion, and it is a major driver of urban eco-environmental change. Increasing temperature leads to the Urban Heat Island (UHI) problem in rapidly growing cities like Denver, contributing to global warming at multiple scales. UHI study is significant to monitor and mitigate the urban heat islandrelated problem in the study area Denver. Satellite remote sensing analysis ready data (ARD) with 30 m resolution based on Landsat 4,5,7 and 8 were acquired for nine dates that correspond to summer, fall, and winter seasons in 1985, 2000, and 2020. Land cover change dynamics were derived using Land Change Monitoring Assessment and Projection (LCMAP) developed land cover classes, and land surface temperature (LST) has been extracted from seasonal and annual surface temperature data. Land cover data analysis observed changes within seven primary land cover classes; for instance, study area has gained 13% of developed land cover but lost a significant percentage of cropland from 1985 to 2020. The relationship between land cover and surface temperature has been explored by linear regression analysis using normalized difference vegetation index (NDVI) and LST. NDVI was taken as the explanatory variable, and LST was taken as a dependent variable to show the correlation between land cover and LST. Investigation of the correlation between NDVI and LST found that seasonal variability, spatiotemporal variations, and other underlying factors affect their relationship. Seasonal and annual Urban Heat Island intensity (UHII) distribution and variation have been investigated. The results found that the mean annual UHII in 2020 was 1°C which was greater than the mean UHII in 1985 and 2000. The UHII distribution was consistent in the central part of the city, and the scattered distribution of UHII was examined in non-urban extent over the past three decades. The methodology of this study can be a framework for future research on cities with a similar climate to Denver, and this can also help for sustainable urban planning and a better ecological environment

Spatial Evolution of the Effects of Urban Heat Island on Residents\u27 Health

Rising summer temperatures caused by the urban heat island (UHI) has considerable effects on the physical and mental health of urban residents globally. To categorize residents’ health risk areas and evaluate the characteristics of urban spatial evolution, based on data analysis methods, such as ArcGIS, ENVI software, and geostatistical analysis, data from meteorological stations, satellite images, and electronic maps were used to investigate spatial evolution and the process by which UHI affects the respiratory, circulatory, and cardiovascular systems and emotional health of the residents of Tianjin. Results show the UHI significantly increases respiratory, circulatory, and cardiovascular diseases. The emotional health of residents is also significantly affected with the affected level moving from level 1 to level 2-4. Highly concentrated areas in the urban center and patches with high health risks are found to be scattered and fragmented, as indicated by the phased pattern of spatially deteriorating hotspots. Hotspots expansion occurs unidirectionally to the south, surrounding the city center, while shrinking from the inside to the outside. The study identifies urban health space risks and provides theoretical guidance for urban space optimization and healthy urban planning

An Evaluation of Surface Urban Heat Islands in Two Contrasting Cities

This thesis presents a comparative study on surface urban heat islands effects in Baghdad and Perth. The first part evaluates expansion of built-up areas and quantifies its effects on land surface temperature patterns. The second part examines the extent to which the urban thermal environment is influenced by spatial patterns of land use and land cover (LULC) categories. The final part investigates the thermophysical behaviour of various urban LULC categories using albedo and LST parameters

The Spatial and Temporal Characteristics of the Urban Thermal Environment in East Africa: Implications for Sustainable Urban Development

Targeting cities in East Africa, where urbanisation and climate change are posing unprecedented threats to livelihoods and ecosystems, this thesis focuses on the combined effects of rapid urbanisation and climate change on Land Surface Temperature (LST), Surface Urban Heat Island (SUHI) effects and the role of Blue Green infrastructure (BGI) and vegetation dynamics. The aim of this thesis is to advance understanding of the urban thermal environment and the role of factors such as climate, vegetation and urbanisation patterns that add to its complexity. Through the use of satellite and remote sensing data (e.g., Google Earth Engine), spatial and statistical analyses, conducted in ArcGIS, Geoda and R, this thesis provides analyses of temporal trends between 2003 and 2017, and spatial differences in LST and SUHI in five East African cities (Khartoum, Addis Ababa, Kampala, Nairobi, Dar es Salaam). It advances understanding of how the configuration of urban areas affects the urban thermal environment, the amount of vegetation and surface water, and demonstrates the influence of urban density on the changes in SUHI intensity in both space and time. By linking the findings from the three results chapters and placing this in the context of the broader literature, corresponding policy implications and solutions are presented. The urgent need to provide a more detailed understanding of urban thermal environments, including macroclimate differences, seasonal variation and urban morphological characteristics, is highlighted. Recommendations emphasise the use of cloud-based analysis methods to overcome data scarcity, while the results point towards the utility of nature-based solutions for urban sustainable development. The methods and lessons emerging from this study can also be applied in other rapidly urbanising cities, where climate change is posing an unprecedented threat to livelihoods and ecosystems, and where resources are limited

Urban Growth and Its Impact on Urban Heat Sink and Island Formation in the Desert City of Dubai.

The rapid pace of urban growth in Dubai has attracted the attention of economists, environmentalists and urban planners. This thesis quantifies the extent of urbanisation within the Emirate since the discovery of oil and investigates the impacts of such growth on urban temperatures. The study used remotely-sensed imagery in the absence of publicly available data on city growth and microclimate. The study used a hybrid classification method and landscape metrics to capture historical urban forms, rates and engines of growth in the Emirate. Stepwise multiple regression analysis techniques were subsequently used to investigate the relationship between the rate and form of urbanisation and the intensity of the urban heat sink between 1990 and 2011. Local Climate Zones were then developed to specifically investigate the impacts of urban geometry variables and proximity to water on both urban heat sinks during the day-time and urban heat islands during the night. The study revealed a significant increase in urban area over time (1972-2011) with accelerated phases of growth, linked to local and global economic conditions, occurring during specific periods. Physical urban growth has now outpaced population growth, indicating urban sprawl. This growth has occurred at the expense of sand and has included a significant increase in vegetation and water bodies unlike other desert cities in the Gulf region. The results demonstrated that urban growth has promoted a heat sink effect during daytime and that all urban land use types contributed to this effect. Urban albedo was not responsible for the daytime urban heat sink; other factors including the specific heat capacity of urban materials, urban geometry and proximity to the Gulf were mainly responsible. Furthermore, increases in vegetation cover and impervious surface cover over time have contributed to the daytime (morning) urban heat sink. At night-time, urban geometry and proximity to the Gulf were the major influences upon the formation of urban heat islands. This research contributes to better understanding of urbanisation in desert cities as demonstrated through Dubai, revealing previously unknown spatiotemporal variations in urban areas across the city through the use of a time-series of satellite images. The findings provide new insights into the impacts of land cover, land use, proximity to water and urban geometry on the formation of urban heat sinks and urban heat islands in the desert environment

Towards a generalisation of the relationship between nocturnal surface and canopy urban heat islands using urban meteorological network

The Urban Heat Island (UHI) as a result of urbanisation processes remains a compelling focus of urban climate research. With the advance of thermal remote sensing, surface urban heat island (sUHI) quantified by the land surface temperature from satellite observations becomes more prevalent in studying the UHI effects. The difference and the physical linkage between sUHI and urban canopy air heat island (aUHI) measured by Urban Meteorological Network (UMN) intrigue the whole urban climate community. The complicated relationship between the intensity of sUHI and aUHI across cities limits the application of the thermal remote sensing in urban environment. This thesis explores the relationship between nocturnal sUHI and aUHI (the sUHI-aUHI relationship) by applying a transferable method, using MODIS satellite and UMN in Oklahoma City, US and Birmingham, UK. Specific patterns of the sUHI-aUHI relationship under different seasons, wind speed conditions and land characteristics are found in both cities. The comparisons between the two cities highlight the strong controls of the local climate and the configurations of the UMN on the differences of the sUHI-aUHI relationship across cities, which are considerable factors in order to generalise this relationship globally

Urban heat mitigation in Sydney, Australia : tree effects and policy context

Rapid urbanization, land use modification and anthropogenic heat emission have accelerated the Urban Heat Island Effect (UHIE) in cities. The UHIE can be defined as the “discernible temperature difference between urban and adjacent rural areas caused by the excess heat emitted and the solar gain trapped by the urbanised environment” (Gartland, 2008). Trees provide cooling through evapotranspiration and surface shading. This thesis takes a transdisciplinary approach to assess the efficacy of trees in cooling urban spaces in Sydney and how well this function is embedded in government policies. Overall, this research showed that both science and policy play a key role in the pathway to achieve urban cooling. Effective urban heat management must be guided by comprehensive urban planning policies. Therefore, the key planning policies of local and state government agencies should contain a standalone provision for urban heat management. While there are numerous scientific studies conducted in Australia on UHIE, their integration within strategic planning at local and state government levels is currently inadequate. Surprisingly, none of the councils examined in the study had firm canopy cover targets associated with expected cooling benefits. This indicates that policy makers at all government levels need to have a deeper understanding about urban heat and how to reduce it or adapt to it. This research provides new strategic guidance to better understand spatial and temporal variability of urban heat and offers improvements to existing practices for planting and managing urban trees

Spatiotemporal Dynamics in Regulating Ecosystem Services of Urban Green-blue Infrastructure

Synoptic citywide maps of green-blue infrastructure (GBI) and associated regulating ecosystem services (RES) can indicate priority locations for GBI investment to build urban resilience to future climate stressors. However, current approaches are typically static in view, and may fail to consider change in services over different temporal cycles. Planned GBI investment may not offer optimal RES solutions when considering seasonal fluctuations in climate and ecological conditions, or environmental change due to future urban development. In response, this thesis aimed to develop a range of spatiotemporal analysis methods to improve the usefulness of current RES map information. The city of Manchester, UK, is the study area, as the environmental impacts of considerable urban development, since the turn of the century, is currently poorly understood by local planning stakeholders. Overall, findings indicate that seasonal variation in RES is a limited concern for the city. Incorporation of seasonally adjusted indicators for temperature regulation and stormwater storage RES, against typical assumptions of static year-round RES functions, result in less than 5% discrepancy in identified RES deprived areas. In contrast, environmental change is more evident over an inter-year period (2000 – 2017). The city lost approximately 11% of existing GBI, although net GBI increases were recorded in a minority of areas. GBI declines were recorded for most land uses, with losses of between 5.7% and 28.3% a concern for residential land uses where residents live and consume RES. In response, scenario analysis indicates that concerted land use targeted GBI conservation (i.e. street tree and residential gardens) policies are the minimum action required to prevent significant future declines in GBI and RES. Overall, the thesis provides a multi-stage analysis workflow to investigate various GBI and RES management scenarios within the context of planned and unplanned urban development. GBI loss is a common urban trend across the globe, whilst cyclical variation in RES may prove more important for cities with greater seasonal extremes in climate conditions. The ecological modelling, map classification and change analysis methods here work with accessible research data and are therefore theoretically adaptable to a range of urban conditions. Indicators are mapped at scales (100m grid) suitable to investigate GBI retrofits of existing built infrastructure and can accommodate different data assumptions regarding proxy model parameterisation

Foraging resource use by grey-headed flying-foxes in urban and non-urban Australia

Urbanisation is a major threat to ecosystems globally, resulting in habitat loss and habitat fragmentation, reduced biodiversity, and/or species extinction. However, urban habitats also create opportunities for exploitation by adaptable species, and this often leads to unbalanced management actions that have little regard for species conservation. Better understanding of the underlying drivers of wildlife species urbanisation will assist wildlife managers in developing effective and balanced conservation-management strategies. The grey-headed flying-fox (Pteropus poliocephalus), is a large, highly mobile species, that is becoming increasingly dependent on urban areas. Flying-fox urbanisation has been hypothesised to be a result of loss of natural foraging habitat, an attraction to increased spatiotemporal stability of food resources in urban areas, and/or both. Yet, little is known about how P. poliocephalus utilise urban areas for foraging. This study aims to investigate foraging resource availability as a driver of the documented P. poliocephalus urbanisation. Foraging habitat use was assessed using a large satellite tracking dataset from 98 individuals between 2012-2017. These data were combined with vegetation type data, and published indices of P. poliocephalus habitat quality to assess foraging habitat preferences. Tracked individuals were overwhelmingly dependent on human-modified landscapes for foraging, particularly where they roosted in major-urban areas. To identify the specific food plant species that support P. poliocephalus in urban areas, paired GPS and accelerometer data were used to identify trees visited by foraging individuals roosting in Adelaide. Tracked individuals preferentially visited residential areas and road-side habitats. Individuals visited a relatively high diversity of food plant species in these habitats, and flowering/fruiting phenology records indicated collective year-round availability of food resources for P. poliocephalus. This study suggests that P. poliocephalus urbanisation is, at least in part, driven by spatiotemporal availability and stability of food resources