Annual variation of rainfall over Brazil and water vapor characteristics over South America

A large region in central Brazil is characterized by summer rainfall and winter dry conditions. During the 6-month period of September, October, November, December, January, and February (SONDJF) this region receives 70% or more of its annual rainfall. Calculations of vertically integrated water vapor flux and its divergence are made for South America. The results suggest that the Amazon basin is the principal source of moisture for central Brazil during the period SONDJF. Water vapor flux from the equatorial Atlantic associated with trade winds is the main moisture source for the Amazon basin.