Índices climáticos para o Estado da Paraíba: determinação e evolução temporal com abordagem na análise espectral.

Abstract

Due to the large area included in the semiarid delimitation of Brazil, more than 86% of its territory, Paraíba is one of the Brazilian states where aridity is more severe. The availability of water is a decisive process in terms of its effective environmental, social and economic development, which is closely dependent on the prevailing climatic conditions. In this context, the need for the quantification of indexes that have as purpose, the climatic characterization of a given location, in order to better suit the prevailing climate classes, emerges. Thus, the present study aims to weave past scenarios of spatial and temporal variability of climatic indexes. Therefore, climatic indexes are calculated from normal climatological and serial annual data for a period of fifty years to twenty pluviometric stations carefully selected and distributed throughout the state of Paraíba. The methodology proposed by Thornthwaite (1948) and the aridity index applied by the United Nations Environment Program - UNEP (1992) are taken into account. As a subsidy, the conceptual application of spectral methods with the subsequent application of the wavelet analysis to the serial climatic indexes is used. It turns out that even if different methodologies produce different climatic classifications for the same place and period of time, the development of interannual and interdecadal variabilities are extremely similar, recommending the same agents as cause of these variabilities. Even so, the UNEP aridity index is less critical for climate classifications than for the use of the Thornthwaite indices, showing less aridity. The interdecadal variability is significantly more apparent than the interannual variability, with a marked predominance in the 11-year scale, interacting with smaller scales of 5, 3.5 and 2.5 years, which tend to follow the main behaviors of the thermal variability in the basins of the Atlantic and Pacific oceans. Simple correlations indicate more significant connections between Pacific modes and the regions of Sertão and Alto Sertão, decreasing toward the coast. On the other hand, water anomalies in the Atlantic Ocean show almost homogeneous influence in much of the state of Paraíba, with a greater signal in the adjacent eastern range. It is also observed that climatic classifications in a serial way, with the processing of the percentages of each type of climate and temporal distribution, represents a more realistic method of climate analysis, given that, based on climatological normals, it describes an average local condition or regional climate.