Climatic classification and semiarid zone regionalization under distinct rainfall scenarios, of the Piauí State, Brazil

Abstract

This work presents a new propose of climatic classification and regionalization for the semiarid region of Piauí State, Brazil. Thornthwaite moisture index estimates of soil-water balance under different climatic conditions as a function of the rainfall scenario (dry, regular, wet and medium depth rainfall years) were used. The percentage of the countries areas under climatic types and rainfall scenario were regionalized by geographical information system (GIS). Six climatic types were defined: arid (E), semiarid (D), sub-humid dry (C1), sub-humid (C2), humid (B1) and humid (B2), which occurrence areas in the State varied with the rainfall conditions. The semiarid zone presented high variation as a function of climatic conditions and climatic classification criteria used in this study. For a regular rainfall year, the semi-arid region varied from 87.8% to 14.1% of the Piauí State area, corresponding to 199 and 34 countries, respectively, depending on the climatic classification criteria. The variability observed in area and countries number show the natural tendency of the rainfall spatial and temporal variability, characterized as function of the rainfall scenario, more compatible with the physic reality.