Análise da variabilidade dos períodos secos e chuvosos da precipitação pluvial no estado da Paraíba utilizando o Índice Padronizado de Precipitação (SPI).

Abstract

Located in the Brazilian Northeast (NEB), Paraíba presents a climatic variability, with periods that vary from high precipitation rates to seasons of severe droughts, due to the direct influence of elements and mechanisms that dictate the rainfall regime in this Region. This work aimed to estimate the variability and trend of rainfall in the state of Paraíba through the analysis of average monthly and annual precipitation in rainy and dry periods. Records from 123 rainfall stations of AESA were considered, contemplating 27 years of observations. Basic statistics were estimated: mean, median, standard deviation, asymmetry coefficient, kurtosis and variation. The results showed that the distribution of rainfall occurs irregularly and with great variation throughout the year. The annual distribution showed high spatial variability of precipitation in the central sector of the state, with smaller values around 300 to 500 mm. In the Sertão and Alto Sertão these values are around 700 to 900 mm. In the Brejo and Agreste of 700 to 1200 mm and in the Litoral from 1200 to 2000 mm. The months of March and April were the wettest months in almost the entire state and from May to August the highest precipitation totals were concentrated in the east lane and mainly in the southern coast. September was considered the driest month and in the rest of the year the rains occurred in an isolated way. The values of the asymmetry coefficient (𝐶𝑠) varied greatly, but in the Zona da Mata these values were more uniform. In almost all months of the historical series of rainfall data the asymmetry was positive. In almost all months of the historical series of rainfall data the skewness was positive. The peaks of the kurtosis coefficient (𝐶𝑘) were concentrated in the central part of the state comprising January through May. From June on, the highest values were seen in the western part of the state. The peaks of the Coefficient of variation (𝐶𝑣) were located in the Agreste and Borborema regions, between January and April. The Sertão was configured as the region with the greatest variation of (𝐶𝑣) during the rest of the year. The Zona da Mata presented a practically annual homogeneity, with low variation from January to March. In the analysis of the dry and rainy periods, the Standardized Precipitation Indices (SPIs) were used in the time scales of 1, 3, 6 and 12 months. Between the years 1997 and 2000 droughts were verified and identified by all the SPIs. These events were possibly influenced by the El Niño phenomenon. Noteworthy here is the historical drought across the entire Paraíba territory in 1998, as well as the droughts that occurred between 2014 and 2016.