Spatialization of monthly aridity index for Piaui state

The objective of this work to estimate the monthly aridity index for the Piaui State. This index is given by the relationship between the amount of rain and reference evapotranspiration. It was used in this study daily data records of rainfall of 165 sites, 145 are located in the state of Piauí and the other in the states of Maranhão, Bahia, Ceará and Pernambuco. For the same locations was estimated monthly reference evapotranspiration by Thornthwaite Method, allowed to calculate the monthly index of aridity. The values found for the 165 sites were spatializated for Piauí State, performing slicing into six thematic classes of monthly aridity index, obtaining thus the thematic maps of monthly aridity index for the Piauí state. Between June and September, about 90% of the Piauí state area is under arid conditions. Only in February and March the rainfall exceeds the evapotranspiration, while 90% of the Piaui state is classified as humid. The spatial distribution of the monthly aridity index can identify times and places most suitable for the development of agriculture, as well as regions subject to desertification.