Urban heat island intensity in coastal cities of northern Colombia using Landsat data and WRF/UCM model

Abstract

This study examines the evolution of urban heat islands (UHI) in northern Colombia during 2016 and 2021. We employed a multi-approach to analyze the intensity and magnitude of UHI in a coastal zone metropolis. We used Landsat images and WRF model numerical modeling coupling the Urban Canopy Module (WRF/UCM) to estimate the UHI variability. Landsat data show the annual mean LST has increased from 27.78 °C in 2016 to 28.46 °C in 2021 in the coastal cities, especially in central and south zones of built-up areas. Moreover, the differences in mean LST values for the LULC classes showed an increase of 0.48, 1.23, 0.06, and 1.07 °C for vegetation areas, build-up areas, water bodies, and barren land areas, respectively, during the analyzed years. The temperature difference between LSTs of built-up and vegetated areas has increased from 2.14 °C in 2016 to 2.89 °C in 2021. The expansion of UHI intensity (UHII) is directly related to the growth of urban zones and the densification of built-up areas. UHI magnitude is high during the daytime and low during the nighttime. In contrast, the average UHII in the diurnal cycle ranged from 1.46 °C to 3.21 °C In 2021, UHII is higher at night (3.49 °C), while in 2016, it is higher in the daytime (1.60 °C) according to the estimate of WRF/UCM model. The expansion and density of urban areas have led to an increase in surface radiation absorption, which has suppressed evaporation over impervious building materials and resulted in a significant rise in 2-m air temperature. Also, the pronounced disparity in surface temperature and the slight variance in sensible heat flux between impervious and vegetation surfaces give rise to heightened UHII during nighttime and, conversely, during daytime. The results of the study underscore the need to promote sustainable practices in the planning and construction of urban infrastructure to mitigate and adapt to UHI.

Keywords

• Urban heat islands
• Coastal cities
• WRF model
• Landsat