Precipitação em Rio Grande – RS (1913 – 2016): Análise descritiva e da variabilidade

Abstract

O objetivo desse artigo é analisar a variabilidade temporal da precipitação em Rio Grande – RS, no período entre 1913 e 2016. Para isso foram utilizadas técnicas estatísticas descritivas e inferencial para caracterizar a distribuição da precipitação em diferentes escalas de tempo e para identificar os ciclos temporais da ocorrência de secas e chuvas acima da média e suas relações com os fenômenos remotos. As análises mostram que a precipitação mensal em Rio Grande varia entre 0,3mm e 551,8mm, com uma média de 102,1 mm e desvio padrão de 66,1 mm; o total anual da precipitação variou entre 625 mm e 2.261,9 mm, com uma média de 1.226 mm; a média mensal tem uma amplitude de 71,2 mm e 126,7 mm, sendo as médias de dezembro e setembro, respectivamente; e são os meses do verão e o outono que apresentaram maior e menor variabilidade da precipitação. Os ciclos temporais da ocorrência de secas e chuvas acima da média ocorreram predominantemente na escala interanual e está associado predominantemente aos fenômenos ENOS e ODP, sendo mais comum a ocorrência de chuvas acima da média/secas concomitantes ao El Niño/La Niña. Não sendo raro a ocorrência de secas e chuvas acima da média, visto que foram identificados 219 meses de seca e 210 meses de chuvas excessivas no período entre 1913 e 2016, adotando um limiar de |56,4 mm| da anomalia da precipitação.Palavras-chave: Precipitação, variabilidade, wavelet, Rio Grande. Precipitation in the city of Rio Grande – RS (1913 – 2016): Descriptive and variability analysis A B S T R A C T The aim was to analyze the temporal variability of rainfall in Rio Grande - RS, during the years 1913-2016, in order to understand the temporal distribution, using descriptive statistical techniques to characterize the monthly and annual total, the monthly averages, the anomalies, the occurrence of extreme events and inferential techniques in order to characterize the main remote factors controlling precipitation variability. The results of these descriptive analyzes show that the monthly rainfall in Rio Grande varies between 0.3mm and 551.8mm with an average of 102.1mm and standard deviation of 66.1mm; the total annual precipitation indicated a variation between 625 mm (minimum) and 2,261.9 mm (maximum), with an average annual accumulation of 1,226 mm; the monthly average varies between 71.2 mm and 126.7 mm, referring to the months of December and September, respectively; estimation of standard deviation showed summer and autumn as the months with the highest and lowest variations, respectively. Temporal variability occurred at the interannual and interdecenal scales and are predominantly associated with the ENSO/ODP phenomenon, with more than average rainfall occurrin /droughts concomitant with El Niño/La Niña. Anomalies above | 56.4 mm | were considered extreme precipitation events and was identified with the technique of quartiles, 219 months of drought and 210 months of excessive rainfall in the period between 1913 and 2016.Keywords: Precipitation, variability, wavelet, Rio Grande.

Blue Carbon: Beyond the Inventory

“…Wetter summers, including the month of November, were predominant during the period 1980-2010. Silva et al (2021) also report that the major modes of variability of the precipitation in Rio Grande, which can be extrapolated to the study area, are related to the seasonal cycle and to a ~5-years and a 8-years period oscillation linked to the ENSO phenomenon. The authors described that the 5-years (8-years) ENSO cycle is associated to the positive (negative) phase of the Pacific Decadal Oscillation, demonstrating that the teleconnections are important for characterizing the climate of the study area.…”

“…Although our site in the Po ́lvora Island is not subject to high tidal amplitudes (Möller et al, 2001) and the precipitation in the vicinity is not very distinct among all seasons when analyzed at the long-term scale (Silva et al, 2021), it is expected that wetter seasons or individual episodes would impact (diminishing) the vegetation/soil-atmosphere CO 2 fluxes. As pointed out by Möller et al (2001), a wetter estuary (marsh) in the vicinity of our study area is related to the increase in the Patos Lagoon outflow (water level) that, on the other hand, is forced by northerly winds and the increase in precipitation, especially during wintertime.…”

“…The annual cycle of sunshine hours is from 10 h (winter) up to 14 h (summer). The ENSO events also influence the precipitation, with El Niño (La Niña) producing higher (lower) precipitation with respect to the climatological average at a determined period (Silva et al, 2021). For our data collection period (July 2016 up to April 2017), a moderate La Niña 1 event occurred from July until December, inducing lower precipitation than the normal climatological values.…”