Phase Coherence Between Surrounding Oceans Enhances Precipitation Shortages in Northeast Brazil

Author(s)

Mao, Y. ; Zou, Y. ; Alves, L. M. ; Macau, E. E. N. ; Taschetto, A. S. ; Santoso, A. ; Kurths, J.

• Document type: Journal article
• Source: Geophysical Research Letters; v. 49, n. 9, p. 10-pg., 2022-05-16.

Abstract

Understanding the direct and indirect impact of the Pacific and Atlantic Oceans on precipitation in the region of Northeast Brazil (NEB) is crucial for monitoring unprecedented drought events. We propose nonlinear methods of phase coherence and generalized event synchronization analysis to understand the underlying mechanism. In particular, the relationships between sea surface temperature (SST) variability and the standard precipitation index are interpreted as direct interactions, while the relationships between surrounding oceans are interpreted as indirect effects on the precipitation. Our results reveal a dominant role of tropical North Atlantic for precipitation deficit and droughts, particularly in recent decades. Meanwhile, the indirect Pacific-North Atlantic phase synchronizations have significant influence on and reinforcement of the droughts in NEB. Furthermore, we find that the instantaneous angular frequencies of precipitation and SST are drastically changed after very strong El Nino and La Nina events, therefore resulting in a higher probability of phase coherence. Plain Language Summary Atmospheric teleconnections are coherent climate responses across the globe and commonly identified by large distance correlations, which have been largely included in climate analysis. Still, the nonlinear features of teleconnections to many places across the globe, including Northeast Brazil (NEB), have not been fully understood. Here, we propose a nonlinear framework of combining phase coherence with event synchronization analysis to further understand the teleconnections between the surrounding oceans and precipitation in NEB, which has been affected significantly by extreme droughts in the recent decade. We find that the North Atlantic Ocean plays a dominant role in affecting NEB rainfall variability. We also show that this influence has become more persistent in recent years compared to the impact from the tropical Pacific. At the same time, the teleconnection between Pacific and North Atlantic has also become more frequent in recent years, which suggests that these tropical ocean basin interactions reinforced the NEB droughts in recent decades. (AU)

• FAPESP's process: 15/50122-0 - Dynamic phenomena in complex networks: basics and applications
• Grantee: Elbert Einstein Nehrer Macau
• Support Opportunities: Research Projects - Thematic Grants