Análise da precipitação pluviométrica em anos extremos no cariri paraibano e suas consequências na agricultura e cobertura vegetal.

Abstract

Precipitation is an important control factor of the hydrological cycle, and also one of the climate variables that exerts the greatest influence on the environmental quality, directly interfering in several sectors of society, especially in regions that suffer from the irregularity of the rainfall distribution, such as Cariri Paraibano. The objective of this work is to investigate the precipitation behavior in extreme years, the influence of the oceans and the impact on agriculture and vegetation cover in the region of Cariri Paraibano. Were selected the municipalities of Sumé (located in Cariri Ocidental) and São João do Cariri (Cariri Oriental). The monthly precipitation data were obtained from the Executive Agency for the Management of Waters of the state of Paraíba (AESA) for the period 1995 to 2015. It was verified that the lowest annual precipitation rates are from September to November, The eastern part of the region (Cariri Oriental) and the largest in the western part (Western Cariri). The highest values of precipitation are concentrated in the first five months of the year, with a contribution of 76.57% of the annual precipitation. From the box-plot technique and the quantiles, it was possible to classify extreme precipitation events. After identification the years of dry and rainy events, these were related to the phases El Niño Southern Oscillation (ENSO) and the interhemispheric meridional temperature gradient of the sea surface (GRADM). And it was verified that, they influence the precipitation events, and as consequences also affect the quantitative of the agricultural production. The visual analysis and the digital processing of Landsat-5 satellite images proved to be very effective in identifying terrestrial targets (vegetation, soil and water). It was also observed that, based on the calculation of the Normalized Difference Vegetation Index (NDVI), it was possible to observe differences in the terrestrial targets, when analyzed the extreme years 1998, 1999, 2008 and 2009. Finally, it can be concluded that the applied methods can be used as a tool for climate monitoring, and that the oceans influence precipitation, harming the population of the region that survives from agriculture.