Sub-regional Precipitation Climate of the Caribbean and Relationships With ENSO and NAO

Thirty-five meteorological stations encompassing the Caribbean region (Cuba, Bahamas, Jamaica, Dominican Republic, Puerto Rico, U.S. Virgin Islands, St. Maarten, and Barbados) were analyzed over the time interval 1951-1981 to assess regional precipitation patterns and their relationships with the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO). Application of factor analysis to these series revealed the existence of four geographically distinct precipitation regions: (1) western Cuba and northwestern Bahamas, (2) Jamaica, eastern Cuba, and southeastern Bahamas, (3) Dominican Republic and northwestern Puerto Rico, and (4) eastern Puerto Rico, U.S. Virgin Islands, St. Marteen, and Barbados. This regionalization is related to different annual cycles and interannual fluctuations of rainfall. The annual cycle is unimodal and largest in the northwest Caribbean (1), and becomes increasingly bimodal toward lower latitudes (4) as expected. Year-to-year variations of precipitation are compared with two well known climatic indices. The ENSO relationship, represented by Niño3.4 SST, is positive and stable at all lags, but tends to reverse over the SE Caribbean (4) in late summer. The NAO influence is weak and seasonally dependent. Early summer rainfall in the northwest Caribbean (1) increases under El Niño conditions. Clusters 2 and 3 are less influenced by the global predictors and more regional in character. Previous related work sub-divided the Caribbean into two to three regions. Our work also shows that the main Caribbean basin should be divided into two clusters and not one homogeneous region as has previously been reported.