Variabilidade espacial e temporal de componentes dos balanços de água e de energia sobre a bacia do rio São Francisco com ênfase para a região de ZCAS.

Abstract

The objective of this study is to analyze the space-temporary variability of meteorological variables that compose the water and energy balances on the Basin of the San Francisco River during the period of actuation of SACZ (South Atlantic Convergence Zones). The area of the Basin corresponds to 7,5% of the national territory occupying parts of the states of Minas Gerais, Bahia, Goias, Distrito Federal, Pernambuco, Alagoas and Sergipe. The principal mechanism producing of precipitation on the Basin of the San Francisco River is the SACZ that acts from November to March. The data from the NCEP/NCAR of precipitation, specific humidity, net radiation, latent heat, sensitive heat and components zonal and meridional of the wind for the period from 1982 to 1994 were used. It was analyzed the averages, the monthly values and the anomalies for each variable for the five months (November to March) from 1982 to 1994. Comprehending like this, periods of normal conditions, of El Nino and of La Nina. On the latitude of 20°S, in the months from November to March, a strip with higher precipitation was observed; this latitude is the same of the medium position of the SACZ. To the north of 20°S, in other words, to the north of the SACZ, it was observed a strip of stronger winds. In the north part of the Basin, in general, in the years of El Nino was observed precipitation, flow of latent heat and specific humidity inferior to climatic average and net radiation and flow of sensitive heat superior to climatic average and the inverse in the years of La Nina. On the other hand, in the south part of the Basin systematic patterns were not observed for the years of El Nino and of La Nina. The configurations of flow of latent and sensitive heat didn't show a pattern type SACZ, so much in the years of El Nino as in the years of La Nina, possibly due the great differences of these flows on the ocean and continent. The pattern type SACZ, in the precipitation field was defined better in the years of El Nino (1982/83 and 1992/93) than in the years of La Nina (1988/89). In some events of El Nino or La Nina the expected pattern as answer to the configuration of the atmosphere was not observed, for example, the precipitation that was so much above or below the average in the years of El Nino or in the years of La Nina. The pattern of precipitation depended on the position of SACZ.