The intense and extreme rains in southeastern Brazil are spatially and temporally dynamic, corroborating their substantial complexity regarding understanding and associations. Therefore, the present study aimed at determining threshold values for events of intense and extreme rainfall in the region of São Carlos/SP using a climatic index, as well as temporal and spatial observations. The RClimdex script, Rnn index, and the detection of outliers were employed in order to mark and establish intense and extreme rainfall thresholds for the region. Values of 10 mm and 20 mm of rain were considered typical and of greater recurrence, and their incidence over a period of 24 hours did not necessarily denote intense events. In turn, values of 35, 46, and 60 mm indicate pluviometric rates that impact on significant disasters, as verified in the IPMET/UNESP natural disasters database. It is important to emphasize that values below 60 mm of daily rainfall may also indicate disaster contexts. However, they do not exclude the necessity to verify the intensity, duration, and frequency of intense rain events, and can delineate thresholds for territorial management organizations in their planning.

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O aspecto dinâmico da atmosfera promove, por meio das chuvas, significativa heterogeneidade temporal e espacial nos dados pluviométricos. A orografia, como elemento de destaque nesse processo, pode intensificar tal dinâmica. Compreender a influência desse mecanismo espaçotemporal se faz necessário. Para tanto, foram analisados 31 postos pluviométricos diários na região centro-leste do Estado de São Paulo, a fim de identificar essa influência, na série histórica 1979-2017. Utilizou-se do cálculo de índices climáticos (RClimdex) e da interpolação especial de dados (IDW) para compreender tal influência. Notaram-se “ilhas de umidade” na região onde o relevo apresenta-se mais elevado, como destaque para os índices de chuva acumulada anual, máximo diário, máximo acumulado em 5 dias e na intensidade pluviométrica. Tal intensificação se reafirma pela conjuntura geoambiental e pelo fator orográfico, sendo mais evidente na relação entre o número de dias consecutivos chuvosos e no valor máximo acumulado em 5 dias consecutivos. Tais aspectos reafirmam a dinâmica de sistemas frontais (SFs) e da convergência de ventos úmidos (ZCAS), típicos da região, que se intensificam em função do relevo. Palavras-chave: Precipitação, chuva orográfica, cuestas basálticas, RClindex e SIG.   Abstract The atmosphere dynamics promotes, through the rains, spatio-temporal heterogeneity in the pluviometric data. Orography as an element it can be intensify rainfall. The comprehended influence of this spatiotemporal mechanism is necessary. For this purpose, 31 daily pluviometry stations were analyzed in the central-eastern region of the State pf São Paulo over 1979-2017 data. The climatic index calculation (RClimdex) and the spatial interpolation data was used to understand this influence. It was noted "humidity islands" in the region where the relief is highest. The annual accumulated rainfall, the daily maximum, the accumulated maximum in 5 days and rainfall intensity improve this. The intensification is reaffirmed by the geoenvironmental situation. The orographic factor being more evident in the relation between the number of consecutive rainy days and the maximum value accumulated in 5 consecutive days. These reaffirms the dynamics of frontal systems (FS) and the convergence of moist winds (ZCAS), typical of the region, which intensify due to the relief. Keywords: Precipitation, orographic rain, basaltic slopes, RClindex and SIG.

Rainfall expresses one of the most complex climate factors in Southeastern Brazil. Understanding the dynamics and temporal trends of rainfall represents a significant challenge due to regional and even global mechanisms, such as FS (Frontal Systems) and the SACZ (South Atlantic Convergence Zone), and the interaction with the Atlantic and Pacific Oceans. The present study aimed at analyzing the pluviometric tendencies in São Carlos/SP, in the countryside of São Paulo State. Laplace trend test was used to comprehend the temporal evolution of daily rainfall in the region in the historical series 1979-2017, in seven pluviometric stations (climatological or surface stations). Significant fluctuations in interannual trends and between seasons were observed. However, it was noted that the beginning of the 1980s showed positive trends, whereas, as of the year 2000, most of the stations demonstrated negative trends, indicating a reduction in daily rainfall volume due to the great tropical climatic variability of Brazil. Emphasis should also be given to the regional and local effects, such as elevation and urbanization, respectively, which corroborate such differences among the analyzed stations. This methodology is of considerable value for the observation of pluviometric trends, and future studies can validate such a tool in climatological studies.