Long-term changes in precipitation in the eastern portion of the Guanabara Bay hydrographic region, Rio de Janeiro, Brazil

Abstract The Guanabara Bay hydrographic region (GBHR) is a strategic area of Rio de Janeiro, with few studies on Climatology and on the annual maximum daily rainfall (P max ). Detecting changes in P max is a prerequisite for a better understanding of the climate and developing adaptation and mitigation measures at a regional and local scale. Therefore, the aim of this study is to identify trends in P max through non-parametric tests in the GBHR region of Rio de Janeiro based on historical time series. Five rain gauges were selected with daily rainfall series due to long time series (ranging from 1939 to 2020) and with a maximum of 10% annual failures. The non-parametric tests (MK, modified MK and Pettitt) were applied to the rainfall temporal series. The series of P max were classified as random, independent, homogeneous and stationary. The P max were observed mostly between November and March. It is noteworthy that this identified period corresponds to the greater performance of South Atlantic Convergence Zone (SACZ), convective rainfall and Frontal Systems (FS) in Rio de Janeiro. The results of MK test were coincident with Pettitt test. The modified MK test detected a trend in rain gauges where the Pettit test was no significative. The change points by Pettit test, in significative trend were 1995 and 1985, for Nova Friburgo and Cachoeiras de Macacu. The results obtained from the study are important for territorial planning, airport management, and for the socioeconomic interest of GBHR – Rio de Janeiro, mainly for COMPERJ (petrochemical complex) and landslide and flood areas.