Urbanization-induced impacts on heat-energy fluxes in tropical South America from 1984 to 2020: The Metropolitan Area of Rio de Janeiro/Brazil

Our study aims to better understand the energy balance in tropical and wet climate urban areas by developing a 37-year (1984-2020) energy balance climatology based on SEBAL algorithm and Landsat data for Metropolitan Area of Rio de Janeiro (MARJ). Particularly, our results show that MARJ lost 13% of its vegetation cover and its urban area almost doubled since the 1980s decade. We show a positive (negative) urban-vegetation albedo (net radiation) difference in MARJ contributing to reduce the UHI intensity, but not capable to compensate for the warming effects related to the partitioning of latent and sensible heat fluxes. Our results revealed that the UHI intensity along the year in MARJ is maximum (minimum) during summer (winter) when the urban-vegetation temperature, sensible and latent heat fluxes absolute differences reach maximum values around 9.9 degrees C (3.8 degrees C), 150 Wm-2 (71 Wm-2), and 330 Wm-2 (145 Wm-2). We observe a great reduction of latent heat flux in urban areas in agreement with the pronounced effect of urbanization on wet climate regions. Thus, alternative/original strategies, not only based on increasing green areas, may be needed to reduce the urban warming in MARJ.

Automated summary

Our study develops an energy balance climatology to understand the energy balance in tropical and wet climate urban areas. The results show a decrease in vegetation cover and an increase in urban area in the Metropolitan Area of Rio de Janeiro. The differences in urban-vegetation albedo contribute to reducing the urban heat island intensity, but the warming effects related to latent and sensible heat fluxes are not compensated. The urban heat island intensity is highest in summer and lowest in winter, with significant differences in urban-vegetation temperature and heat fluxes.