Tracking jet streams as Lagrangian objects

Accurately locating jet streams is key to understanding climate variability and regional weather patterns. However, the conventional Eulerian view of jets as fast winds overlooks their continuous meandering, favoring spurious streaks to the detriment of weaker but persistent features that shape large-scale transport. Here we make the case for a Lagrangian view of jets as maxima of isentropic displacement. We introduce a new identification scheme, called JetLag, whose two parameters are set by theory. JetLag recovers familiar features of the historical record (1941-2024) without ad hoc parameter tuning. Remarkably, the resulting estimates of jet latitude and variability are robust to parameter choice, supporting a unified view of jets across latitudes and climates. Jet streams are more than strong winds: they are persistent, meandering wind patterns. This perspective reduces the quiet influence of methodological choices on jets’ long-term evolution.