Identifying potential precursors to anomalous precipitation over Inter-America

• Other Authors: Church, Andrew (author), Hurrell, James (contributor), Gettelman, Andrew (contributor)
• Format: Manuscript
• Language: English
• Published: 2001
• Subjects: Sea surface temperature; Seasonal mean data; Increased rainfall; Nordeste; Decreased precipitation; Subtropical plains; Pacific; North Atlantic
• Online Access: http://nldr.library.ucar.edu/repository/collections/SOARS-000-000-000-139; https://doi.org/10.5065/57xx-4y82

Simultaneous and precursory signals in sea surface temperature (SST) associated with anomalous precipitation over North, Central and South America are examined with seasonal mean data. The relationships are documented for SST variations in three regions: the equatorial Pacific (NIĂ‘O3), the tropical North Atlantic (NATL), and the tropical South Atlantic (SATL). These area definitions are based on the distributions of variance explained by the leading modes of SST variability in each ocean basin. The analyses reveal that when SSTs are warmer than average in the NIĂ‘O3 region, increased rainfall in the Caribbean Islands and southern Central America occurs. Precipitation also increases over the central US while it decreases over portions of Columbia, Venezuela, Guyana, Suriname, and French Guiana as well as the Nordeste region of South America. When NATL SSTs are warmer than average, large areas of the north central US as well as northeast Brazil experience decreased precipitation. When changes in SATL SSTs are considered, positive correlations with precipitation over the Nordeste and subtropical plains regions of South America are highly significant. Several long-lead relationships between SST and anomalous precipitation are identified. Changes in NINO3 SST during boreal summer are significantly correlated with rainfall anomalies over northern South America and southern North America six months later. Similarly, changes in both NATL and SATL SSTs are found to precede inter-American precipitation anomalies by six to nine months.