Avaliação temporal do balanço de energia em ambientes urbanos na cidade de Cuiabá-MT

Abstract

The impacts caused by anthropogenic action on the environment of Cuiabá’s city were responsible for changes in the city’s climate, resulting modification in energy balance of the city. Against this background, this study aimed to evaluate the temporal energy balance in urban environments located in three different positions of the Cuiabá city since this approach has not been widely used in the urban areas in Brazil. For this purpose, it was selected three sites in the city: Site 1 located in central region (Eastern), Site 2 in the intermediate region (West), and Site 3 in the peripheral region (Northern). The anthropogenic heat flux dissipated inside the urban canopy (QF) represented approximately 5% of annual net radiation available in the urban environment (Q* + QF) at sites 1, 2 and 3. The fractions of heat stored within the urban canopy (ΔQs), latent heat (QE) and sensible heat (QH) by the energy available in the urban environment in the dry season corresponded to 26, 28 and 46% in the Site 1 and 23, 30 and 46% in the wet season. In the Site 2, these fractions corresponded to 24, 31 and 45% in dry season, and 20, 46 and 33% in the wet season, while the Site 3, 28, 30 and 42% and 26, 32 and 45% respectively. The average daytime (Q* > 0) of the Bowen ratio (β) in the dry season were 1.80, 1.51 and 1.66 for sites 1, 2 and 3, respectively, and 1.62, 0.75 and 1.68 in the wet season, which implies that the sensible turbulent fluxes were predominated on the latent heat fluxes in urban areas. Exception was verified in Site 2 during the rainy season due to the higher presence of vegetation around this site. It was noted that in the three sites, ΔQS and Q* were in phase and that they described elliptical path in a counterclockwise direction. It was found that the rates of heat fluxes stored inside urban canopy and sensible heat fluxes are directly related to the fraction of impermeable flat area and inversely to the fraction of vegetated plat area in the vicinity of urban sites surveyed. The annual averages fractions for QE/Q* were located above the theoretical curve established for temperate cities, while QH/QE and QH/(Q* -ΔQs) were located below, which indicates the need for further research on the topic of cities in tropical climate. The results provide important insights for planning and management of cities as they may assist in the establishment of new criteria and recommendations that can be inserted in the master plan of the Cuiabá city in order to improve the quality of life of its population.