Role of the eastern Pacific-Caribbean Sea SST gradient in the Choco low-level jet variations from 1900-2015

Abstract

In this article, we propose a novel approach for assessing the effects of sea surface temperature (SST) variations in the eastern Pacific and the Caribbean Sea on the Choco low-level jet (CJ) intensity over the 1900-2015 period that involved defining the interbasin gradient index (IGR) between these 2 oceanic basins. We also studied the effects on rainfall in northwestern South America and Central America in the high CJ season during September-November (SON). Wavelet coherence analysis showed high consistency between CJ and IGR on an interannual scale of 2-8 yr. Precipitation increased over central, western, and northern Colombia and most of Central America during strong CJ (SCJ) and decreased during weak CJ (WCJ) events, which occurred, respectively, in the negative IGR (NIGR) and positive IGR (PIGR) phases. NIGR is associated with anomalous cooling in the tropical Pacific and warming in the equatorial Atlantic; opposite patterns are observed during PIGR. Also, the CJ and the Caribbean low-level jet (CLLJ) showed reversed intensities such that as one strengthened, the other weakened and vice versa. Our results indicate that the low-frequency SST anomalies in the North Atlantic affect the IGR and low-level jet intensities associated with changes in large-scale circulation modulated by the Atlantic multidecadal oscillation (AMO). Indeed, positive precipitation anomalies during the SCJ under NIGR were more accentuated and extensive in the warm AMO (WAMO) than in the cold AMO (CAMO) phase. Conversely, negative precipitation anomalies during WCJ under PIGR were more accentuated and extensive in the CAMO than in the WAMO.