Intraseasonal synchronization of extreme rainfalls between North India and the Sahel

TL;DR

This study uncovers the synchronized occurrence of extreme rainfall events between North India and the Sahel during the monsoon season, revealing a lagged connection influenced by large-scale climate patterns and atmospheric dynamics.

Contribution

It introduces a climate network approach to identify intraseasonal synchronization of extreme rainfall between two major monsoon regions, highlighting the role of atmospheric circulation patterns.

Findings

Strong synchronization of extreme rainfall during July-August

Heavy rainfall over North India linked to Sahel with ~12 days lag

La Niña conditions and atmospheric oscillations promote synchronization

Abstract

The Indian Summer Monsoon (ISM) and the West African Monsoon (WAM) are dominant drivers of boreal summer precipitation variability in tropical and subtropical regions. Although the regional precipitation dynamics in these two regions have been extensively studied, the intraseasonal interactions between the ISM and WAM remain poorly understood. Here, we employ a climate network approach based on extreme rainfall events to uncover synchronously occurring extreme rainfall patterns across the two monsoon systems. We reveal strong synchronization of extreme rainfall events during the peak monsoon period in July and August, linking heavy rainfall over North India to that over the Sahel with a lag of around 12 days. We find that La Ni\~na-like conditions in combination with the Boreal Summer Intraseasonal Oscillation and an enhanced Tropical Easterly Jet (TEJ) foster the synchronization between the ISM and the WAM. Convective clouds are transported by an intensified TEJ from southwestern Asia toward North Africa, supporting anomalous deep convection over the Sahel region.