Does the urban presence of a city in the central Amazon induce more extreme precipitation?

Abstract In recent years, significant efforts have been made to understand how urban environments influence local weather, particularly extreme precipitation events. However, studies conducted to date for the largest city in the Amazon, Manaus, have focused mainly on investigating the effects of urbanization based on case studies, often limited to just one extreme precipitation event. This work expands on this approach by investigating 45 extreme events that occurred between 2010 and 2020, to assess the average impact of extremes in the presence of an urban surface surrounded by forests and rivers. Using the Weather Research and Forecasting Model (WRF) coupled with the Single Layer Urban Canopy Model (SLUCM), simulations were performed with (URB) and without (NOURB) the presence of the urban area. The results show that urbanization intensified extreme precipitation, increasing both the accumulated volume (by 16.8% in the city center) and hourly intensity (with approximately 79.2% of the hourly values exceeding those of the NOURB scenario), especially in the city center during the afternoon. It was noted that the increase in precipitation in the URB scenario was associated with three main mechanisms: i) greater heating of the surface ( $$\Delta T_{skin}$$ = 2.9 $$^{\circ }$$ C) and of the air layer immediately in contact with it ( $$\Delta T_{2m}$$ = 0.6 $$^{\circ }$$ C); ii) higher vertical wind speed in the middle troposphere ( $$\Delta w$$ = 0.03 m/s); and iii) greater moisture convergence in the middle troposphere ( $$\Delta q_{800}$$ = 0.09 g/kg). These mechanisms favored the intensification of convective systems over the city. By considering multiple events, this study offers a more comprehensive understanding of how urban environments, situated in humid tropical contexts, can influence extreme precipitation patterns.