What is the name for a long, narrow corridor of concentrated water vapour in the atmosphere?

An atmospheric river is a long, narrow corridor that transports concentrated water vapour through the atmosphere.

These features are typically associated with extratropical weather systems and can carry moisture from warm ocean regions toward land. When an atmospheric river reaches a mountain range, rising air can produce heavy rain or snow. A small number of events can deliver a large share of a region’s annual precipitation.

Atmospheric rivers are not literal rivers in the sky filled with liquid water. Their water is mainly present as invisible vapour, and the term describes the transport corridor rather than a single cloud type. Some atmospheric rivers bring beneficial precipitation that replenishes reservoirs and snowpack, while stronger events can cause flooding, landslides and travel disruption.

Scientists identify them using measurements such as integrated water vapour and water-vapour transport. Their frequency, intensity and impacts vary by region and climate pattern.