Caribbean Precipitation Trends during a Regional Sea Surface Temperature Warming Period, 1982–2014

This study investigates precipitation trends during the sea surface temperature (SST) warming period (1982 – 2014) that has been detected in the Intra-Americas Region (IAR), the region including the Caribbean and parts of North America, South America, Mexico, and Central America. A warming trend of SSTs has been detected in the IAR for the past 32 years (1982-2014), which could have potential implications for precipitation variation within the Caribbean and the surrounding region. The IAR experiences bimodal precipitation periods which define the seasons – the Early Rainfall Season (ERS) from April to June, the Late Rainfall Season (LRS) from August to November and the Dry Season from December to March. Negative trends (drying) were observed for annual, ERS, and DS regionally accumulated rainfall and a positive trend for the LRS, but only the DS trend was determined to be statistically significant for the 32-year period. The Dry Season reflects the steepest decreasing trends associated with statistically significant p-values at the 95% significance level. Spatial analyses show the southern part of the region has experienced an increase in annual and seasonal rainfall, however, only with high statistical significance in some parts of the IAR during the LRS. In addition, precipitation also reflects high, positive correlations with SSTs in the southern part of the IAR with high statistical significance. Principal component analysis results indicate that the first principal component (PC1) of the Dry Season has the highest variance of all seasons which is approximately 28% for precipitation and 40% for SSTs. Results from a linear model determined that SSTs explain the interannual variability and trend observed for precipitation during the 1982-2014 period, with the annual model yielding the highest adjusted R² (0.706) when the first three modes are considered. The equivalent models for each season varied in significance of PCs for the ERS (0.359), LRS (0.699), and DS (0.484). The third mode (PC3) was determined to be significant in all cases except the ERS, in which only the first mode (PC1) was significant. Spatial maps of PC3 reflect an East-West dipole or gradient effect in the region and may be indicative of sea-level pressure or atmospheric effects. The link between warming SSTs and rainfall during the same period is demonstrated on an annual mode, however, other climate phenomena during individual seasons reduce the impact of warmer SST conditions.