Avanço da urbanização e impacto nos fluxos de água e energia à superfície na cidade de Manaus: Estudo de Modelagem

Abstract

Manaus' urbanization over the past five decades has been fast, losing part of its native forest cover to a highly dense urban infrastructure. Considering this fast process, it was realized the necessity of a deep investigation into the urban impact on energy and hydrological surface fluxes. Therefore, in this study, two numerical experiments were performed with the WRF model coupled with an urban canopy model and a surface schema. Numerical simulations were performed considering: (1) the urbanization in Manaus from the beginning of the 70’s decade, with a prevailing area of native forest and a small urban portion classified as low residence density; and (2), the current urban area, which includes forest fragments, high and low residence density and industrial classes. The results show that the urban sprawl modified the airflow aerodynamic caused by the urban infrastructure and, along with the increase of surface and air temperature related to soil and sensible heat fluxes, resulted in the precipitation increase over the urban area. This increase induced the modification of the available surface energy partitioning, being the latent heat flux its biggest share. Still, due to the reduction of the vegetation cover, the latent heat flux was smaller in the urbanized simulation. The combined effect of surface change and the precipitation increase favored the modification of surface hydrological components, such as an increase of surface and subsurface runoff caused by the increasing of impermeable areas and the rain volume; an increase of the surface evaporation, acting as a precipitation feedback mechanism; and the reduction of transpiration and intercepted evaporation, linked to the forest cover. Therefore, this preliminary study shows that the urbanization advance in Manaus, over the last 49 years, significantly changed the surface energy balance that contributed to the increase of local temperature and the Urban Heat Island effect configuration. Besides, contributed to the increase of rain over the urban area and change in the surface water balance components. These results indicate a combined effect linked straight to the enlargement of the urban infrastructure and its influence on the local atmospheric conditions.