Pacific and Atlantic Multidecadal Variability Relations with the Choco and Caribbean Low-Level Jets during the 1900–2015 Period

Wilmar L Cerón,Itamara Parente De Souza,Mary T Kayano,Rita V Andreoli,Rodrigo A F Souza,Alvaro Avila-Diaz

doi:10.3390/atmos12091120

Abstract

This study analyzes the variability of the Choco jet (CJ) and Caribbean low-level jet (CLLJ) with consideration of the simultaneous Pacific interdecadal oscillation (PDO) and Atlantic multidecadal oscillation (AMO) low-frequency mean states and their effects on the atmospheric circulation and rainfall in northwestern South America and Central America for the 1900–2015 period, during the seasons with the highest intensities of the CJ (September–November (SON)) and the CLLJ (June–August). Variations in the sea surface temperature (SST) anomaly positioning in the eastern Pacific, tropical North Atlantic (TNA)/Caribbean Sea during different mean states restrict the anomalous circulation, and, consequently, the intensity of the CJ and CLLJ. During the warm AMO (WAMO)/cold PDO (CPDO), the SST gradient from the tropical Pacific into the TNA, accompanied by a cyclonic circulation near the east coast of the Americas, intensifies the west–east circulation in the region, strengthening the CJ and weakening the CLLJ during SON such that rainfall increases over Colombia, Central America and in adjacent oceans. During the cold AMO (CAMO)/warm PDO (WPDO) phase, a relative east/west SST gradient occurs in TNA, consistent with a cyclonic circulation in western TNA, establishing an anomalous southwest–northwestward circulation from the eastern Pacific into the Caribbean basin, forming a well-configured CJ, increasing precipitation over Central America and its adjacent oceans. For the CLLJ, during CAMO phases, the anticyclonic circulations extended over most of the TNA favor its intensification from 30° W to the Caribbean Sea. In contrast, during WAMO, the cyclonic circulation near the east coast of the United States restricts its intensification to the Caribbean Sea region. To the best of our knowledge, the results presented here are new and might be useful in atmospheric modeling and extreme event studies.

Highlights

It is well known that the rainfall in northwestern South America is strongly influenced by the Pacific and Atlantic Intertropical Convergence Zones (ITCZ) [1,2,3,4,5] and by two lowlevel regional jets (LLJs), one in the far eastern Pacific and western Colombia (the Choco jet (CJ)) and another formed by the easterlies in the Caribbean Sea (the Caribbean low-level jet (CLLJ)) [6,7,8,9] (Figure 1)
This study analyzes the variability of the CJ and CLLJ with consideration of the simultaneous Pacific, and Atlantic sea surface temperature (SST) low-frequency mean states and their effects on the atmospheric circulation and rainfall in northwestern South America and Central America for the 1900–2015 period
Our results suggest that part of the variability of the CJ and CLLJ might be due to differences in the combined low-frequency mean states between the Atlantic multidecadal oscillation (AMO) and Pacific interdecadal oscillation (PDO) and the contrasts generated in the interbasin gradient between the eastern tropical Pacific and the tropical North Atlantic (TNA)/Caribbean Sea

Summary

Introduction

It is well known that the rainfall in northwestern South America is strongly influenced by the Pacific and Atlantic Intertropical Convergence Zones (ITCZ) [1,2,3,4,5] and by two lowlevel regional jets (LLJs), one in the far eastern Pacific and western Colombia (the Choco jet (CJ)) and another formed by the easterlies in the Caribbean Sea (the Caribbean low-level jet (CLLJ)) [6,7,8,9] (Figure 1). Diverse local and regional atmospheric circulation patterns interact with the ITCZ, the main system that modulates the annual precipitation cycle through its meridional migration [3,22,23]. In this regard, the CJ is forced to ascend to the western Andes in Colombia and interact with easterly trade winds, causing deep convection over the west and center of the country [3,6].

Results

Discussion

Conclusion