Influence of the Coupling South Atlantic Convergence Zone-El Niño-Southern Oscillation (SACZ-ENSO) on the Projected Precipitation Changes over the Central Andes

Juan C. Sulca,Rosmeri P. da Rocha

doi:10.3390/cli9050077

Abstract

There are no studies related to the influence of the coupling between the South Atlantic Convergence Zone (SACZ) and El Niño-Southern Oscillation (ENSO) pattern variability on future changes in the austral summer (December-February, DJF) precipitation over the central Andes. Therefore, we evaluated the historical simulations (1980–2005) and projections (2070–2099) for the Representative Concentration Pathway 8.5 (RCP 8.5) scenario of 25 global climate models (GCMs) from the Coupled Model Intercomparison Project phase 5 (CMIP5). Moreover, we also consider the Regional Climate Model version 4 (RegCM4) projections nested in three CMIP5 GCMs (GFDL-ESM2M, MPI-ESM-MR, and HadGEM2-ES) under RCP 8.5. We separate the CMIP5 GCMs according to their abilities to simulate the nonlinear characteristics of ENSO and the SACZ for the historical period. We found that only three out of 25 CMIP5 GCMs (hereafter group A) simulate the nonlinear characteristics of ENSO and the SACZ during the historical period. Although most CMIP5 GCM project DJF precipitation decreases over the central Andes, group A project precipitation increases related to the projected increase in deep convection over the central Peruvian Amazon. On the regional scale, only RegGFDL (nested in a group A CMIP5 GCM) projects a statistically significant increase in DJF precipitation (~5–15%) over the northern central Andes and the central Peruvian Amazon. Conversely, all RegCM4 simulations project a decrease in DJF precipitation (~−10%) over the southern central Andes.

Highlights

The South American Monsoon System (SAMS) is one of the major monsoon systems in the Southern Hemisphere [1]
Since the BH is not enough to describe the pattern of atmospheric circulation associated with DJF precipitation over the northern central Andes (e.g., Mantaro basin) [36], we focus on the performance of the Bolivian high-Nordeste low (BH-NL) system over South America during the austral summer in Coupled Model Intercomparison Project phase 5 (CMIP5) global climate models (GCMs)
We found that three CMIP5 GCMs (MPI-ESM-MR, MPI-ESMP, and HadGEM2-ES) do not reproduce the nonlinear behavior of El Niño-Southern Oscillation (ENSO) because they present a nonlinear ENSO metric (α) that is greater than −0.12 or even positive

Summary

Introduction

The South American Monsoon System (SAMS) is one of the major monsoon systems in the Southern Hemisphere [1]. The SAMS onset occurs in October, reaching its mature phase from December to February and declining in April [2]. During the austral summer (December-January-February, DJF), the maximum precipitation falls over the south-central. There is an intense low-level moisture flux from the central Amazon basin toward southeastern South America at 850 hPa called the South. American low-level jet (SALLJ; [3]) (Figure 1a). In the upper troposphere (200 hPa), the Bolivian high-Nordeste low (BH-NL) system is the main feature of the austral summer climatology in South America [4] (Figure 1b). The BH-NL system disappears when the upper-level westerly zonal flow prevails over the continent

Objectives

Methods

Results

Conclusion