A principal component analysis was used to characterize the annual and interannual variability of outgoing longwave radiation over South America and neighboring regions. The data sample is comprised of monthly Advanced Very High Resolution Radiometer (AVHRR) data, covering the period January 1982 - December 1993. The results obtained characterize the behavior of the spatial pattern of the dominant weather systems acting over Brazil. The first component represents the mean convective activity pattern; the second and the fourth ones are respectively associated with the summer/winter and spring/autumn modes of the annual cycle. The third component shows spatial variability modulated by El Niño and the fifth one is associated with the semi-annual cycle.
convective activity; principal components; climate
