Dinâmica da urbanização na região metropolitana de Belém e mudanças nos regimes sazonais durante o clima atual e futuro num cenário amazônico.

Abstract

The intense and systematic process of urban population densification and vegetation suppression, a characteristic of anthropic transformations, can trigger several changes not only in the geographic space, but also in the regional climate, thus yelding impacts on social and environmental dimensions. The main objective of this study is to quantify the spatial/temporal dynamics of changes in the surface cover of the Metropolitan Region of Belém (RMB), in eastern Amazon, with a focus on urbanization, during the last four decades, including analysis of the effects/impacts on the seasonal regimes of the rainy (January to April) and dry (July to November) regimes. In addition, a Downscaling study was performed using the regional model RegCM4 to generate future climate projections (next two decades) for the RMB associated with the impacts of global climate change. To achieve the proposed objectives, the study made use of demographic data from the IBGE, mapping by remote sensing with the application of physical indices to identify land use and cover changes, environmental data extracted from the MapBiomas platform and several in situ (station) and satellite (CRU, CHIRPS and CMORPH) climate databases. Statistical methods and quantitative analyzes were used in these databases. The results obtained in the independent study of multitemporal mapping by remote sensing, corroborated by the MapBiomas data, revealed major transformations over the regional landscape of the RMB in the last decades. Among the main evidences found, we can report: urban expansion conditioned a warmer climate in the city of Belém; in the RMB, the vegetation suppression led to the expansion of pasture/agriculture areas, whose environmental changes explained the trend of monotonic increase in air temperature in both seasonal regimes; Belém and RMB present trends of systematic intensification of the rainy regime. The projections generated by RegCM4 (considering the RCP8.5 scenario that is the most extreme of global warming) indicate that regional patterns of future climate in Belém and RMB will be affected by global climate change. Future climate simulations (next 25 years, 2021 to 2045) in relation to current climate data (last 35 years, 1986 to 2020) indicate that warmer urban climate conditions are expected to persist in the coming decades, with an increase in air temperature of 1.5ºC in the RMB and 1.3ºC in Belém for the dry regime and 1ºC in the RMB and 0.9ºC in Belém for the rainy regime. There are indications of continuation of the positive trend of the rainy regime with an increase in precipitation of about 25% in the RMB and 14% in Belém. Finally, it appears that the availability of satellite images, observational climate data bases and time series of meteorological data, associated with image geoprocessing techniques, advances in modeling science and computational technologies to perform downscaling with RegCM4, make possible the continuous monitoring and integrated investigation of the urban geographic space and seasonal climate pattern, whose scientific results are relevant to support the planning and decision-making of municipal environmental management and the elaboration of public policies for the benefit of society.