Atmospheric 'Flying Rivers' Map Out Moisture Highways Across South America

Scientists have charted a vast system of airborne moisture streams that criss‑cross South America, forming branching patterns that closely resemble the river basins we see on the ground.

Using a combination of satellite‑based water‑vapor measurements and high‑resolution climate models, researchers traced the movement of humid air from the Atlantic and Pacific coasts inland, revealing persistent corridors that funnel moisture hundreds of kilometres before it is released as rain.

The observed pathways exhibit the same hierarchical structure as terrestrial drainage networks: small “tributaries” of humid air merge into larger “confluences,” ultimately feeding the massive “main stems” that supply the Amazon basin and other interior regions.

These atmospheric highways are more than a scientific curiosity; they deliver the bulk of the precipitation that sustains the continent’s rainforests, agriculture and water supplies. A disruption in any segment of the network could translate into reduced rainfall far downstream, with implications for food security and ecosystem health.

While the term “atmospheric river” has been applied to narrow, high‑intensity moisture flows that affect places like California, the new analysis shows that South America hosts an extensive, web‑like system that operates year‑round, linking oceanic sources to interior catchments in a manner previously unrecognized.

The findings are prompting calls for these flying rivers to be incorporated into regional climate forecasts and drought‑early‑warning systems, as better representation of their dynamics could improve predictions of rainfall variability across the continent.