ENSO teleconnections pathways in South America

Author(s)

Rehbein, Amanda ; Ambrizzi, Tercio

• Document type: Journal article
• Source: Climate Dynamics; v. N/A, p. 16-pg., 2022-12-25.

Abstract

ENSO events are the most important interannual phenomena impacting climate and weather in South America and have been studied for a long time. Most studies gave special focus on its warm phase (El Nino events) during the austral summer months. However, it is not yet conclusive how the teleconnection patterns are modified according to the different intensities of ENSO events in different seasons and consequently impact South America. Therefore, this study aims to investigate how the different phases, intensities, and seasons of the ENSO events modulate the Stationary Rossby Waves that impact South America. For this, we developed a free and open-source tool called raytracing. The distribution of the SST anomalies influences ENSO intensity. When SST anomalies are higher and spread along the Equatorial Pacific Ocean, ENSO tends to be stronger. This has an impact on the convective source intensity and shapes leading to different Rossby wave sources. Weak ENSO events drive weak anomaly precipitation over South America, mainly in the southeast region. Stationary Rossby waves starting positions are slightly closer to the equator during El Nino over downstream crests/upstream troughs. During La Nina events, they are positioned poleward over downstream troughs/upstream crests. Stationary wavenumbers K-S = 2 and 3 are predominant over South America during El Nino events and DJF La Nina events, while K-S = 2 are predominant in the remaining La Nina events. The wave shape and amplitudes are almost constant during summer events independent of the ENSO intensity, configuring the robustness of the precipitation anomaly patterns over South America. However, in the other seasons, those wave features vary largely, influencing the position and signal of the precipitation anomalies over South America. As a general rule, positive precipitation anomalies regions are associated with a downstream crest and upstream trough in both ENSO phases. While downstream troughs/upstream crests are associated with negative precipitation impacts. (AU)

• FAPESP's process: 16/10557-0 - Mesoscale convective systems over the Amazon basin: present climate and future climate change scenarios
• Grantee: Amanda Rehbein
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 14/50848-9 - INCT 2014: INCT for Climate Change
• Grantee: Jose Antonio Marengo Orsini
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants
• FAPESP's process: 21/07992-5 - Impact of climate change on Mesoscale Convective Systems over the Amazon basin
• Grantee: Amanda Rehbein
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 17/09659-6 - Interannual variability of the meridional transports across the SAMOC basin-wide array (SAMBAR)
• Grantee: Edmo José Dias Campos
• Support Opportunities: Research Projects - Thematic Grants