Atmospheric rivers as Lagrangian coherent structures

TL;DR

This paper demonstrates that filamentous atmospheric rivers over the North Atlantic are closely associated with attracting Lagrangian Coherent Structures in the wind field, which influence passive water vapor transport.

Contribution

It reveals the connection between atmospheric rivers and LCSs using FTLE analysis, linking water vapor patterns to flow structures in the atmosphere.

Findings

LCSs bound AR filaments on the back side.

LCSs influence passive water vapor transport.

AR water vapor patterns correlate with LCS locations.

Abstract

We show that filamentous Atmospheric Rivers (ARs) over the Northern Atlantic Ocean are closely linked to attracting Lagrangian Coherent Structures (LCSs) in the large scale wind field. LCSs represent lines of attraction in the evolving flow with a significant impact on all passive tracers. Using Finite-Time Lyapunov Exponents (FTLE), we extract LCSs from a two-dimensional flow derived from water vapor flux of atmospheric reanalysis data and compare them to the three-dimensional LCS obtained from the wind flow. We correlate the typical filamentous water vapor patterns of ARs with LCSs and find that LCSs bound the filaments on the back side. Passive advective transport of water vapor from tropical latitudes is potentially possible.