The Impacts of Landscape Changes on Annual Mean Land Surface Temperature in the Tropical Mountain City of Sri Lanka: A Case Study of Nuwara Eliya (1996–2017)

Abstract

Although urbanization has contributed to improving living conditions, it has had negative impacts on the natural environment in urbanized areas. Urbanization has changed the urban landscape and resulted in increasing land surface temperature (LST). Thus, studies related to LST in various urban environments have become popular. However, there are few LST studies focusing on mountain landscapes (i.e., hill stations). Therefore, this study investigated the changes in the landscape and their impacts on LST intensity (LSTI) in the tropical mountain city of Nuwara Eliya, Sri Lanka. The study utilized annual median temperatures extracted from Landsat data collected from 1996 to 2017 based on the Google Earth Engine (GEE) interface. The fractions of built-up (BL), forested (FL) and agricultural (AL) land, were calculated using land use and cover maps based on urban–rural zone (URZ) analysis. The urban–rural margin was demarcated based on the fractions of BL (<10%), and LSTI that were measured using the mean LST difference in the urban–rural zone. Besides, the mixture of land-use types was calculated using the AL/FL and BL/FL fraction ratios, and grid-based density analysis. The results revealed that the BL in all URZs rapidly developed, while AL decreased during the period 1996 to 2017. There was a minimal change in the forest area of the Nuwara Eliya owing to the government’s forest preservation policies. The mean temperature of the study area increased by 2.1 °C from 1996 to 2017. The magnitude of mean LST between urban–rural zones also increased from 1.0 °C (1996) to 3.5 °C (2017). The results also showed that mean LST was positively correlated with the increase and decrease of the BL/FL and AL/FL fraction ratios, respectively. The grid-based analysis showed an increasing, positive relationship between mean LST and density of BL. This indicated that BL density had been a crucial element in increasing LST in the study area. The results of this study will be a useful indicator to introduce improved landscape and urban planning in the future to minimize the negative impact of LST on urban sustainability.

Google Earth Engine Cloud Computing Platform for Remote Sensing Big Data Applications: A Comprehensive Review

“…Conducting urban studies are essential to support sustainable development. In this regard, RS datasets enable the quantification and profound analysis of urban dynamics that are fundamental for devising suitable approaches for urban development and urban planning [110]. GEE promotes longterm monitoring of urban conditions to effectively study the urban environment from different aspects.…”

“…GEE promotes longterm monitoring of urban conditions to effectively study the urban environment from different aspects. Urban expansion and extent mapping [18], [111], urban morphology and local climate zone monitoring [112], [113], urban 4D modeling [52], urban green space classification [114], [115], urban temperature and urban heat island identification [17], [110] are some of the main urban studies conducted within GEE. For instance, [17] studied the long-term monitoring of Surface Urban Heat Island (SUHI) and its relation to urban land cover changes over six metropolitan areas of the United States.…”

Spatiotemporal Variation of Urban Heat Islands for Implementing Nature-Based Solutions: A Case Study of Kurunegala, Sri Lanka

“…During the past few decades, most of the green areas and wetlands in urban and peri-urban areas in Sri Lanka have been converted to impervious surfaces (IS) [12]. These rapid conversions have resulted in several negative impacts, such as air pollution [13], decreasing green surface (GS) [9], declining agricultural lands [14,15], increasing vector-borne diseases [16], water pollution [17], declining wetlands [18] and increasing Urban Heat Island (UHI) [19].…”

“…In Sri Lanka, most of the past UHI studies focused on the cities which are located in diverse geographical zones including coastal cities (e.g., Colombo [12,19,52] and Galle [53]) and mountain cities (e.g., Kandy, and Nuwara Eliya [9,15,54,55]). The findings of these previous studies provide sufficient information to understand the UHI pattern and to enhance remedial measures to control the negative impacts associated with UHI.…”

Rurbanization—Making the City Greener: Young Citizen Implication and Future Actions

“…Urbanization has a great impact on the local city climate, thus triggering the urban heat island effect and affecting the quality of life [36,37]. The center area of a city registers the highest surface temperature compared to the surrounding open area and the areas covered with vegetation and water [38].…”