Hemispheric Synoptic Patterns Control Rainfall and Long-Range Aerosol Transport in the Amazon

Abstract

The transatlantic transport of dust and smoke aerosols from Africa to South America is a large-scale, year-round process that affects atmospheric and nutrient cycling in the Amazon rainforest. We analyze daily variations in black carbon at the Amazon Tall Tower Observatory (ATTO) to investigate how Atlantic synoptic-scale meteorology influences its long-range transport. Black carbon fluctuations during the Amazon wet season were not fully explained by air mass trajectory length or direction. Instead, regional-scale rainfall emerged as the key driver of shifts between clean and polluted days at ATTO. Rainfall maxima along trajectories preceded clean days, indicating effective wet scavenging. Composite analysis linked these rain events to synoptic systems like U.S. cold air outbreaks and South Atlantic high-pressure anomalies, which enhance moisture convergence and rainfall, promoting aerosol removal. Climate-driven shifts in tropical Atlantic circulation could alter aerosol and nutrient transport to the Amazon, with unknown impacts on rainforest productivity and resilience.