Padrões de variabilidade do vento à superfície do Nordeste do Brasil.

Abstract

Hourly surface wind data covering a 5-year period (1977-1981) for 77 stations located on Northeast Brazil were used in this study. Multivariate analysis methods (principal components analysis and cluster analysis) were applied to mean decadal values of the zonal (ZWC) and meridional (MWC) surface wind components, individually and in conjunction, in order to identify patterns of their time variability. Patterns' association with physiography and atmospheric phenomena acting on the region was searched for. Factorial analysis based on principal components applied to cach surface wind component shows the first three ZWC temporal factor loadings to explain 93.8% of the total variance, while the first two MWC temporal factor loadings explain 91.0%. Analysis of the ZWC and MWC in conjunction shows the first three temporal factor loadings to explain 88.4% of the total variance. Results show the large-scale atmospheric circulation (South Atlantic subtropical anticyclone) and the complex physiography (principally the São Francisco River valley) to be determining factors for the surface wind behaviour in Northeast Brazil. Temporal patterns were also associatcd with other phenomena; ITCZ, SACZ, upper tropospheric cyclonic vórtices, southern frontal systcms, easterly disturbances, mesoscale convective systems and local circulations. Regionalization on principal component analysis of the most significant temporal factor loadings, followed by cluster analysis based on Ward's method, rcvcals the existence of five homogeneous groups for the ZWC, four (04) homogeneous groups for the MWC and five (05) homogeneous groups for the ZWC and MWC, in conjunction, in Northeast Brazil. The resulting groups are seen to be influcnced by the majority of the atmospheric systems, especially the South Atlantic subtropical anticyclone, and by the physiography.