Generalized Synchronization Between ENSO and Hydrological Variables in Colombia: A Recurrence Quantification Approach

Hernán D Salas,Norbert Marwan,Germán Poveda,Óscar J Mesa

doi:10.3389/fams.2020.00003

Abstract

We use Recurrence Quantification Analysis (RQA) to study features of Generalized Synchronization (GS) between El Niño-Southern Oscillation (ENSO) and monthly hydrological anomalies (HyAns) of rainfall and streamflows in Colombia. To that end, we check the sensitivity of the RQA concerning diverse HyAns estimation methods, which constitutes a fundamental procedure for any climatological analysis at inter-annual timescales. In general, the GS and its sensitivity to HyAns methods are quantified by means of time-lagged joint recurrence analysis. Then, we link the GS results with the dynamics of major physical mechanisms that modulate Colombia's hydroclimatology, including the Caribbean, the CHOCO and the Orinoco Low-Level Jets (LLJs), and the Cross-Equatorial Flow (CEF) over northwestern Amazonia (southern Colombia). Our findings show that RQA exhibits significant differences depending on the HyAns methods. GS results are similar for the HyAns methods with variable annual cycle but the time-lags seem to be sensitive. On the other hand, our results make evident that HyAns in the Pacific, Caribbean and Andean regions of Colombia exhibit strong (weak) GS with the ENSO signal during La Niña (El Niño), when hydrological anomalies are positive (negative). Results from the GS analysis allow us to identify spatial patterns of non-linear dependence between ENSO and the Colombian's climatology. The mentioned moisture transport sources constitute the interdependence mechanism and contribute to explain hydrological anomalies in Colombia during the phases of ENSO. During La Niña (El Niño), GS is strong (weak) for the Caribbean and the CHOCO LLJs. Moreover, moisture advection by the Caribbean and CHOCO LLJs exhibit synchrony with HyAns at 0 to 2 (2 to 4) month-lags over north-western Colombia. Furthermore, our results suggest a strong (weak) GS between negative (positive) Sea Surface Temperatures (SST) anomalies in the Eastern Pacific and rainfall anomalies in Colombia. In contrast, GS is strong (weak) for positive (negative) SST anomalies in the Central Pacific. Our GS results contribute to advance our understanding on the regional effects of ENSO in Colombia, whose socio-economical, environmental and ecological impacts cannot be overstated. This work provides a novel approach that reveals new insights into the impact of ENSO on northern South America.

Highlights

Synchronization is a well-known phenomenon that occurs when different oscillatory systems adjust the time scales of their oscillations due to mutual interaction [1, 2]
We study the emergence of generalized synchronization (GS) between two different types of ENSO and the Colombian hydrology, given that several recent works have shown that major SST warming has occurred frequently in the central Pacific, notably different from the eastern Pacific warming pattern during canonical El Niño events [46,47,48,49]
The objectives of this work are manifold: (i) To quantify nonlinear inter-dependencies between the ENSO signal and the anomalies of hydrological variables in Colombia using the GS approach based on recurrence quantification analysis (RQA); (ii) To assess the sensitivity of the GSmetrics based on RQA using diverse methods used to define hydro-climatic anomalies; (iii) To evaluate the impact of ENSO on the Colombian hydrology through its effect on the sources of moisture that feed the water cycle dynamics over Colombia; (iv) To calculate GS between different types of El Niño indices (Central Pacific, Eastern Pacific, and Mixed) and the Colombian hydrology; and (v) To examine by means of GS metrics the propagation of the ENSO signals over Colombia

Summary

Introduction

Synchronization is a well-known phenomenon that occurs when different oscillatory systems adjust the time scales of their oscillations due to mutual interaction [1, 2]. Diverse types of synchronization can be determined, such as frequency synchronization (FS), phase synchronization (PS), identical synchronization (IS), generalized synchronization (GS), and lag synchronization (LS) [3]. Diverse methods have been proposed to study synchronization, such as those based on recurrences [5,6,7,8,9,10], phase differences [1, 11,12,13], and quasisimultaneous appearance of events [14,15,16,17]. The method based on recurrences (recurrence plots and RQA) is based on properties from the non-linear dynamical systems, such as the Poincaré Recurrence Theorem [18] and the Takens’ theorem regarding the artificial reconstruction of strange attractors [19, 20]

Objectives

Methods

Results