Assessing Spatial-Temporal Variability of Land Surface Temperature in Kigali City of Rwanda.

Abstract

Urbanization is a growing fact in Low- and Middle-Income Countries (LMICs), with the development of new urban areas improving the overall quality of life. However, the impact of urbanization on the thermal environment of cities has become increasingly significant. The increase in urban population is a primary factor in the expansion of residential areas, which significantly impacts the land surface temperature (LST). This study aims to examine the impact of urban growth, Land Use Land Cover (LULC) changes, and built-up areas (using the Normalized Difference Built-up Index, NDBI) and vegetation (using the Normalized Difference Vegetation Index, NDVI) on LST in Kigali City. The analysis of LST in 2000, 2010 and 2020 through Remote Sensing and GIS techniques showed the increase in LST over the two decades with considerably higher increase between 2010 and 2020. The minimum and maximum LST increased from 12.17°C and 24.25°C to 16.4 °C and 35.7°C in 2000 to 29.28 °C in 2020 with the ramp increase observed in the urban regions of the earth. These results show a significant regression relationship between the LST, NDVI, and NDBI indices, linking them to changes in land-use. The increase in NDVI significantly reduced the LST, ranging between -0.86 and -0.96, while a high rise in NDBI enhanced the heat island effect, ranging between 0.94 and 0.97. Temporal analysis revealed a reduced NDVI and an enhanced NDBI, also known as the decreased vegetation density and increased built-up area, which, in turn, led to the increased LST. The results indicate that urban planning and management are critical in mitigating issues such as the decline in vegetation cover and the intensification of the urban heat island effect.

Key words: LST, Remote Sensing, NDVI, NDBI, LULC Change