Quantifying the Connection Between Eulerian and Lagrangian Approaches to Studying Storm Tracks

The mid-latitude storm tracks are often defined and quantified using Eulerian and Lagrangian approaches. The Eulerian approach relies on eddies (deviations from the mean) while the Lagrangian approach considers the tracks of individual cyclones and anticyclones. Though each approach has its advantages, it is unclear how they are quantitatively connected. In particular, how the well-known hemispheric differences in annual mean and seasonal cycle of Eulerian eddy kinetic energy (EKE) and the NH summertime decrease of Eulerian EKE are connected to Lagrangian storm track number, intensity, etc. Here we develop a Lagrangian EKE that quantitatively connects the Eulerian EKE results to the number, duration, intensity, and radius of feature-tracked cyclones and anticyclones. The results show that the dominant Lagrangian factor accounting for the hemispheric differences in annual mean and seasonal cycle of Eulerian EKE is cyclone and anticyclone intensity and not number. Furthermore, the dominant Lagrangian factors responsible for the NH summertime decrease of Eulerian EKE are cyclone and anticyclone intensity and cyclone radius. Overall, the results are the first step toward understanding the connection between the Eulerian and Lagrangian storm track response to global warming.