Characterizing Spatiotemporal Variations in the Urban Thermal Environment Related to Land Cover Changes in Karachi, Pakistan, from 2000 to 2020

Abstract

Understanding the spatiotemporal patterns of urban heat islands and the factors that influence this phenomenon can help to alleviate the heat stress exacerbated by urban warming and strengthen heat-related urban resilience, thereby contributing to the achievement of the United Nations Sustainable Development Goals. The association between surface urban heat island (SUHI) effects and land use/land cover features has been studied extensively, but the situation in tropical cities is not well-understood due to the lack of consistent data. This study aimed to explore land use/land cover (LULC) changes and their impact on the urban thermal environment in a tropical megacity—Karachi, Pakistan. Land cover maps were produced, and the land surface temperature (LST) was estimated using Landsat images from five different years over the period 2000–2020. The surface urban heat island intensity (SUHII) was then quantified based on the LST data. Statistical analyses, including geographically weighted regression (GWR) and correlation analyses, were performed in order to analyze the relationship between the land cover composition and LST. The results indicated that the built-up area of Karachi increased from 97.6 km² to 325.33 km² during the period 2000–2020. Among the different land cover types, the areas classified as built-up or bare land exhibited the highest LST, and a change from vegetation to bare land led to an increase in LST. The correlation analysis indicated that the correlation coefficients between the normalized difference built-up index (NDBI) and LST ranged from 0.14 to 0.18 between 2000 and 2020 and that NDBI plays a dominant role in influencing the LST. The GWR analysis revealed the spatial variation in the association between the land cover composition and the SUHII. Parks with large areas of medium- and high-density vegetation play a significant role in regulating the thermal environment, whereas the scattered vegetation patches in the urban core do not have a significant relationship with the LST. These findings can be used to inform adaptive land use planning that aims to mitigate the effects of the UHI and aid efforts to achieve sustainable urban growth.

Diverse cooling effects of green space on urban heat island in tropical megacities

“…It also assumes error terms are independent and normally distributed. Spatial regression models such as spatial lag model, spatial error model and geographically weighted regression can be applied in order to account for spatial dependencies in the relationship between characteristic of UGS and intensity and range of UCI (Bartesaghi-Koc., 2022;Baqa et al, 2022). Urban ecology is a huge system, and any environmental factors are likely to affect urban cool effects (Yu et al, 2017).…”

Prediction of flash flood susceptibility using integrating analytic hierarchy process (AHP) and frequency ratio (FR) algorithms

“…Geographic Information System (GIS) and remote sensing techniques are the most widely used techniques to know the physical and biological surface of the land and gather necessary data for flood modeling (Nashwan et al, 2019;Tariq et al, 2022a;Sadiq Fareed et al, 2022;Wahla et al, 2022). Nowadays, GIS and RS techniques have are crucial tools to develop multi-criteria zoning decision analysis (Nyaupane and Chhetri, 2009;Baqa et al, 2022;Tariq et al, 2022b). GIS techniques are used to prepare flood mapping of an area.…”

Explore the Mitigation Mechanism of Urban Thermal Environment by Integrating Geographic Detector and Standard Deviation Ellipse (SDE)

“…In terms of research content, the research on urban thermal environment mainly includes remote sensing monitoring, formation mechanism, simulation prediction, and ecological safety evaluation of urban thermal environment. For example, there are some studies on the relationship between land use change and urban thermal environment [7][8][9]; urban thermal environment studies based on land surface temperature and socio-ecological variables, and other studies that only list the effects of a single natural or a single human-economic perspective on urban thermal environment [10][11][12]; and at the architectural level, studies in which the main focus is on the planning of urban ventilation corridors and how to mitigate heat islands [13,14].…”