Avaliação da estimativa da evapotranspiração potencial via dados de satélite meteorológico em um modelo hidrológico aplicado às sub-bacias do Nordeste do Brasil.

Abstract

In this research. the impact of the estimated potential evapotranspiration (ETP) on river discharge. actual evapotranspiration and soil humidity. which were determined by using a general hydrological model (GMH) is evaluated. The daily and monthly climatological data were used to estimate the potential evapotranspiration by means of the empirical equations and also to initialize the hydrological model. The global solar radiation data for the month of September. 1997 was obtained from the global solar radiation estimation model. GL 1.0. The model GL 1.0 utilizes the data from the VIS channel of GOES-8. Also used were the hydrological data of precipitation and river discharge of the sub-basins 37 and 38 of the hydrographic basin 3 which is located in the Northeast Brazil. The methodology involved the following steps: 1) spatial regionalization of the potential evapotrasnpiration using the method of WARD which is available on SPSS (Statistical Package for the Social Sciences) software: 2) corrclation bctween the potential evapotranspiration values estimated from the methods of Jensen & Haise - MJH (1963). Caselles et al. - MCA (1992) and the method of Penman - MP (1948). respectively. were obtained: 3) tests of sensibility of the empirical formulations proposed by Jensen & Haise MJH (1963) and Caselles et al. - MCA (1992) as a function of the changes in the surfacc global solar radiation and the air temperature: 4)simulation of the general hydrological model for the sub-basin 37 and 38. considering the different methods of estimation of the potential evapotranspiration and the evaluation of the correction coefficient in the estimation of the potential evapotranspiration: and. 5) estimation of the actual evapotrasnpiration. soil humidity and the discharge using the GHM. MCA and the global solar radiation data. The general hydrological model was developed for the South America with a spatial resolution of 0.5° x 0.5°. The sensibility tests showed the method of estimation of ETP influenced the discharge rates calculated for the regions where the precipitation values are very close to those of the ETP. The estimates of actual evapotrasnpiration. soil humidity and river discharge. obtained from the hydrological model. presents satisfactory results with a maximum error of 20% when compared with the estimates obtained from the satellite data.