Urban heat risk: protocols for mapping and implications for Colombo, Sri Lanka

Global and urban-induced local warming lead to increasing heat risk in cities. The rapid increase in urban population, weak infrastructure, poverty, as well as an ageing population, make the risk more acute in developing cities. However, heat risk is not uniformly distributed and a detailed exploration of the link between urban characteristics and local variations in heat risk is needed to aid targeted mitigation. In this paper, we demonstrate a fine-grained heat risk map using existing data combined with expert opinion in a humid tropical city (Colombo, Sri Lanka) with the objective of highlighting the relative heat risk as a function of physical and socioeconomic conditions across the city. We then simulate the effects of shading and greening on the ‘high’ heat risk areas, and greening on the ‘low’ heat risk areas, to show that a combined approach will be needed to reduce risk at ‘high’ risk areas. In ‘low’ risk areas, maintaining the green cover is crucial to heat risk reduction. The paper, thus, establishes a protocol for detailed heat risk mapping with existing data and points to the differing importance of shading and greening in different parts of the city, thus, showing where, and to what extent, mitigation actions could be beneficial

Quantifying Surface Urban Heat Island Formation in the World Heritage Tropical Mountain City of Sri Lanka

Presently, the urban heat island (UHI) phenomenon, and its adverse impacts, are becoming major research foci in various interrelated fields due to rapid changes in urban ecological environments. Various cities have been investigated in previous studies, and most of the findings have facilitated the introduction of proper mitigation measures to overcome the negative impact of UHI. At present, most of the mountain cities of the world have undergone rapid urban development, and this has resulted in the increasing surface UHI (SUHI) phenomenon. Hence, this study focuses on quantifying SUHI in Kandy City, the world heritage tropical mountain city of Sri Lanka, using Landsat data (1996 and 2017) based on the mean land surface temperature (LST), the difference between the fraction of impervious surfaces (IS), and the fraction of green space (GS). Additionally, we examined the relationship of LST to the green space/impervious surface fraction ratio (GS/IS fraction ratio) and the magnitude of the GS/IS fraction ratio. The SUHI intensity (SUHII) was calculated based on the temperature difference between main land use/cover categories and the temperature difference between urban-rural zones. We demarcated the rural zone based on the fraction of IS recorded, <10%, along with the urban-rural gradient zone. The result shows a SUHII increase from 3.9 °C in 1996 to 6.2 °C in 2017 along the urban-rural gradient between the urban and rural zones (10 < IS). These results relate to the rapid urban expansion of the study areas from 1996 to 2017. Most of the natural surfaces have changed to impervious surfaces, causing an increase of SUHI in Kandy City. The mean LST has a positive relationship with the fraction of IS and a negative relationship with the fraction of GS. Additionally, the GS/IS fraction ratio shows a rapid decline. Thus, the findings of this study can be considered as a proxy indicator for introducing proper landscape and urban planning for the World Heritage tropical mountain city of Kandy in Sri Lanka

Impact of Urbanization on Land Cover Changes and Land Surface Temperature in Iseyin Local Government Area, Oyo State, Nigeria

Urbanization, without any iota of doubt, is one of the leading factors modifying the Earth’s surface because it has a significant impact on land cover changes and Land Surface Temperature (LST). This study assessed the impact of urbanization on land cover changes and LST in Iseyin Local Government Area. Landsat images of 22 years duration (2000, 2013, and 2022) and 30 m resolution were used in the study. The result showed that in 2000, vegetation occupied 58538 ha (43%), the built-up areas covered 2535 ha (2%), farmland covered 61248 ha (45%), rocky/hilly areas accounted for 3226 ha (2.4%), water bodies accounted for 431.17 ha (0.3%) while bare land covered 8642 equivalent to 6.42% of the area. In 2013, the built-up area occupied 3.4% (4577 ha), water body covered 0.21% (281 ha), vegetation covered 35% (48136 ha), farmland covered 48% (64352 ha), bare land covered 11% (15944 ha) while rocky/hilly area covered 1.02% (1376 ha). In 2022, built-up areas covered 6393 ha (4.8%), water bodies, vegetation and farmland covered 515 ha, 33819 ha, and 75999 ha respectively while bare land and rocky/hilly areas also covered 14346 ha and 3594 ha respectively. The LST result showed a mean temperature value of about 32oC, 27oC and 29oC in 2000, 2013, and 2022 respectively. The study concludes that urbanization has largely affected the land cover types in Iseyin LGA and increased the LST between 2000 and 2022. The study has therefore provided a scientific reference to policymakers to develop effective and sustainable policies in Iseyin LGA

Investigation and Prediction of the Land Use/Land Cover (LU/LC) and Land Surface Temperature (LST) Changes for Mashhad City in Iran during 1990–2030

Mansourmoghaddam, M., Rousta, I., Cabral, P., Ali, A. A., Olafsson, H., Zhang, H., & Krzyszczak, J. (2023). Investigation and Prediction of the Land Use/Land Cover (LU/LC) and Land Surface Temperature (LST) Changes for Mashhad City in Iran during 1990–2030. Atmosphere, 14(4), 1-21. [741]. https://doi.org/10.3390/atmos14040741 --- Funding: This study was supported by the Shanghai Municipal Science and Technology Commission within the international cooperation framework of the Youth Scientists from the “One Atmosphere 2023, 14, 741 18 of 21 Belt and One Road” countries (2020–2023), and partially supported by the FCT (Fundação para a Ciência e a Tecnologia) under the project UIDB/04152/2020—Centro de Investigação em Gestão de Informação (MagIC).Studies on how cities are affected by urban heat islands (UHI) are critical nowadays for a better understanding of the connected effects and for providing helpful insights for sustainable city development planning. In this study, Landsat-5 Thematic Mapper (TM), Landsat-7 Enhanced Thematic Mapper+ (ETM+), and Landsat-8 Operational Land Imager (OLI) images were used to assess the dynamics of the spatiotemporal pattern of land use/land cover (LU/LC) and land surface temperature (LST) in the metropolitan city of Mashhad, Iran in the period between 1990 and 2019. The Markov chain model (MCM) was used to predict LU/LC and LST for 2030. In the analyzed LU/LC maps, three LU/LC classes were distinguished, including built-up land (BUL), vegetated land (VL), and bare land (BL) using the maximum likelihood (ML) classification method. The collected data showed different variations in the geographical pattern of Mashhad LST during the research period that impacted the LST in this metropolis. The study evaluated the variations in LU/LC classes and evaluated their impact on the LST. The value of the LST was positively correlated with the occurrence of the built-up land (BUL), and with the bare land areas, while it was negatively correlated with the occurrence of the VL areas. The analysis of changes observed over three decades with 10-year intervals and the prediction of the LU/LC and LST for 2030 constitute an important contribution to the delineation of the dynamics of long LU/LC and LST records. These innovative results may have an important impact on policymaking fostering environmental sustainability, such as the control and management of urban expansion of Mashhad in connection with UHI.publishersversionpublishe

Ecosystem Service and Land-Use Changes in Asia

This book highlights the role of research in Ecosystem Services and Land Use Changes in Asia. The contributions include case studies that explore the impacts of direct and indirect drivers affecting provision of ecosystem services in Asian countries, including China, India, Mongolia, Sri Lanka, and Vietnam. Findings from these empirical studies contribute to developing sustainability in Asia at both local and regional scales

Impact of Urban Surface Characteristics and Socio-Economic Variables on the Spatial Variation of Land Surface Temperature in Lagos City, Nigeria

The urban heat island (UHI) and its consequences have become a key research focus of various disciplines because of its negative externalities on urban ecology and the total livability of cities. Identifying spatial variation of the land surface temperature (LST) provides a clear picture to understand the UHI phenomenon, and it will help to introduce appropriate mitigation technique to address the advanced impact of UHI. Hence, the aim of the research is to examine the spatial variation of LST concerning the UHI phenomenon in rapidly urbanizing Lagos City. Four variables were examined to identify the impact of urban surface characteristics and socio-economic activities on LST. The gradient analysis was employed to assess the distribution outline of LST from the city center point to rural areas over the vegetation and built-up areas. Partial least square (PLS) regression analysis was used to assess the correlation and statistically significance of the variables. Landsat data captured in 2002 and 2013 were used as primary data sources and other gridded data, such as PD and FFCOE, were employed. The results of the analyses show that the distribution pattern of the LST in 2002 and 2013 has changed over the study period as results of changing urban surface characteristics (USC) and the influence of socio-economic activities. LST has a strong positive relationship with NDBI and a strong negative relationship with NDVI. The rapid development of Lagos City has been directly affected by conversion more green areas to build up areas over the time, and it has resulted in formulating more surface urban heat island (SUHI). Further, the increasing population and their socio-economic activities including industrialization and infrastructure development have also caused a significant impact on LST changes. We recommend that the results of this research be used as a proxy tool to introduce appropriate landscape and town planning in a sustainable viewpoint to make healthier and livable urban environments in Lagos City, Nigeria

Strategic Analyses of the National River Linking Project (NRLP) of India, Series 1. India’s water future: scenarios and issues

River basinsEnvironmental flowsDevelopment projectsWater requirementsIrrigated farmingWater demandFood demandGroundwater irrigationIrrigation efficiencyWater harvestingSupplemental irrigationWater productivityWater conservationDrip irrigationSprinkler irrigationRainfed farmingAgricultural policy