Modelo regional de estimativa do balanço hídrico aplicado à variabilidade climática do Nordeste do Brasil.

Abstract

The goals of this work are: to verify the influence of the oceanic events El Nino, La Nina and of the sea surface temperature anomalies in South Atlantic (ASN - negative, ASP - positive) in the interannual variability of the water budget in Northeast Brazil, except Maranhao, to investigate the possible contributions of this variability in desertification processes of semi-arid areas in the Northeast, and to elaborate a regional model to estimate the reference crop evapotranspiration (ET0), used as input data of water budget. The data used is obtained from 52 from meteorological of the INMET, from 434 raingauge stations of SUDENE, FUNCEME and INMET and maximum water retention capacity by the soil from EMBRAPA- Solos of 434 places where precipitation data is available. The FAOPenman- Monteith equation is used to calculate the ET0 of the 52 INMET stations. The regression analysis is used to obtain a regional model to estimate the ET0 of the places where have the raingauge stations. The water balance is estimated from Thomthwaite e Mather (1957) modified method. The results obtained show a large variability in the Northeast climate where multiple climate regimes were verified in the northern, in central portion of the semi-arid the climate is arid, in years of ASN and/or of El Nino, and is subhumid dry/sub-humid humid, in years of ASP and/or of La Nina. During ASN and/or El Nino events the humidity of the soil in the Northeast is very low, the runoff is practically nonexistent and water infiltration for the most profound layers in the soil is almost null, and the precipitation is not enough to supply the evapotranspiration. The droughts during ASN event are severer than the ones during El Nino events. In the ASP and/or La Nina events are observed soil humidity indices, on an average along all year, of the order of 30% in the Northeast part center-north, runoff, and infiltration. It concludes that the water storage in the reservoirs and groundwater occur basically during ASP and La Nina events, and the Northeast of Brazil is a susceptible region to the desertification processes of the point of view of the climate, however in the part center-north of the region the susceptibility degree to desertification processes are very height.