El Niño–Southern Oscillation and North Atlantic Oscillation Control of Climate in Puerto Rico

Abstract Many studies have shown that the El Nino–Southern Oscillation (ENSO) has a significant influence on climate in many parts of the globe, mostly in the Pacific Basin. The objective of this study is to examine the possible impact of ENSO on climatic patterns on the island of Puerto Rico in the Caribbean. The authors find that annual mean air temperatures are controlled by ENSO since 1914. El Nino years are associated with warm air temperatures, whereas El Viejo (La Nina) years, which are the opposite of El Nino, are cooler. On the other hand, since 1911 fluctuations in annual rainfall amounts are synchronous with variations in the North Atlantic Oscillation (NAO) during the winter and are not controlled by ENSO. During years of a high winter NAO index, when the axis of moisture transport in the North Atlantic changes to a more southwesterly–northeasterly orientation, annual precipitation in Puerto Rico is lower than average.